Category Archives: Instrumentation and Methods for Astrophysics

US National Gemini Office in the NOIRLab era [IMA]

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http://arxiv.org/abs/2304.10657


This article presents an overview of the US National Gemini Office (US NGO) and its role within the International Gemini Observatory user community. Throughout the years, the US NGO charter changed considerably to accommodate the evolving needs of astronomers and the observatory. The current landscape of observational astronomy requires effective communication between stakeholders and reliable/accessible data reduction tools and products, which minimize the time between data gathering and publication of scientific results. Because of that, the US NGO heavily invests in producing data reduction tutorials and cookbooks. Recently, the US NGO started engaging with the Gemini user community through social media, and the results have been encouraging, increasing the observatory’s visibility. The US NGO staff developed tools to assess whether the support provided to the user community is sufficient and effective, through website analytics and social media engagement numbers. These quantitative metrics serve as the baseline for internal reporting and directing efforts to new or current products. In the era of the NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab), the US NGO is well-positioned to be the liaison between the US user base and the Gemini Observatory. Furthermore, collaborations within NOIRLab programs, such as the Astro Data Lab and the Time Allocation Committee, enhance the US NGO outreach to attract users and develop new products. The future landscape laid out by the Astro 2020 report confirms the need to establish such synergies and provide more integrated user support services to the astronomical community at large.

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V. Placco and L. Stanghellini
Mon, 24 Apr 23
10/41

Comments: 15 pages, 8 figures, published in the Journal of Astronomical Telescopes, Instruments, and Systems

S-ACF: A selective estimator for the autocorrelation function of irregularly sampled time series [IMA]

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http://arxiv.org/abs/2304.10641


We present a generalised estimator for the autocorrelation function, S-ACF, which is an extended version of the standard estimator of the autocorrelation function (ACF). S-ACF is a versatile definition that can robustly and efficiently extract periodicity and signal shape information from a time series, independent of the time sampling and with minimal assumptions about the underlying process. Calculating the autocorrelation of irregularly sampled time series becomes possible by generalising the lag of the standard estimator of the ACF to a real parameter and introducing the notion of selection and weight functions. We show that the S-ACF reduces to the standard ACF estimator for regularly sampled time series. Using a large number of synthetic time series we demonstrate that the performance of the S-ACF is as good or better than commonly used Gaussian and rectangular kernel estimators, and is comparable to a combination of interpolation and the standard estimator. We apply the S-ACF to astrophysical data by extracting rotation periods for the spotted star KIC 5110407, and compare our results to Gaussian process (GP) regression and Lomb-Scargle (LS) periodograms. We find that the S-ACF periods typically agree better with those from GP regression than from LS periodograms, especially in cases where there is evolution in the signal shape. The S-ACF has a wide range of potential applications and should be useful in quantitative science disciplines where irregularly sampled time series occur. A Python implementation of the S-ACF is available under the MIT license.

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L. Kreutzer, E. Gillen, J. Briegal, et. al.
Mon, 24 Apr 23
28/41

Comments: N/A

Magnetic field measurement from the Davis-Chandrasekhar-Fermi method employed with Atomic Alignment [IMA]

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http://arxiv.org/abs/2304.10665


The Davis-Chandrasekhar-Fermi (DCF) method is widely employed to estimate the mean magnetic field strength in astrophysical plasmas. In this study, we present a numerical investigation using the DCF method in conjunction with a promising new diagnostic tool for studying magnetic fields: the polarization of spectral lines resulting from the atomic alignment effect. We obtain synthetic spectro-polarimetry observations from 3D magnetohydrodynamic (MHD) turbulence simulations and estimate the mean magnetic field projected onto the plane of the sky using the DCF method with GSA polarization maps and a modification to account for the driving scale of turbulence. We also compare the method to the classical DCF approach using dust polarization observations. Our observations indicate that the modified DCF method correctly estimates the plane-of-sky projected magnetic field strengths for sub-Alfv\’enic turbulence using a newly proposed correction factor of $\xi’ \in 0.35 – 0.75$. We find that the field strengths are accurately obtained for all magnetic field inclination and azimuth angles. We also observe a minimum threshold for the mean magnetic field inclination angle with respect to the line of sight, $\theta_B \sim 16^\circ$, for the method. The magnetic field dispersion traced by the polarization from the spectral lines is comparable in accuracy to dust polarization, while mitigating some of the uncertainties associated with dust observations. The measurements of the DCF observables from the same atomic/ionic line targets ensure the same origin for the magnetic field and velocity fluctuations and offer a possibility of tracing the 3D direction of the magnetic field.

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P. Pavaskar, H. Yan and J. Cho
Mon, 24 Apr 23
29/41

Comments: N/A

Fifteen years of millimeter accuracy lunar laser ranging with APOLLO: dataset characterization [IMA]

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http://arxiv.org/abs/2304.11128


We present data from the Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) covering the 15-year span from April 2006 through the end of 2020. APOLLO measures the earth-moon separation by recording the round-trip travel time of photons from the Apache Point Observatory to five retro-reflector arrays on the moon. The APOLLO data set, combined with the 50-year archive of measurements from other lunar laser ranging (LLR) stations, can be used to probe fundamental physics such as gravity and Lorentz symmetry, as well as properties of the moon itself. We show that range measurements performed by APOLLO since 2006 have a median nightly accuracy of 1.7 mm, which is significantly better than other LLR stations.

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J. Battat, E. Adelberger, N. Colmenares, et. al.
Mon, 24 Apr 23
38/41

Comments: 16 pages, 9 figures

TONE: A CHIME/FRB Outrigger Pathfinder for localizations of Fast Radio Bursts using Very Long Baseline Interferometry [IMA]

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http://arxiv.org/abs/2304.10534


The sensitivity and field of view of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) has enabled its fast radio burst (FRB) backend to detect thousands of FRBs. However, the low angular resolution of CHIME prevents it from localizing most FRBs to their host galaxies. Very long baseline interferometry (VLBI) can readily provide the subarcsecond resolution needed to localize many FRBs to their hosts. Thus we developed TONE: an interferometric array of eight $6~\mathrm{m}$ dishes to serve as a pathfinder for the CHIME/FRB Outriggers project, which will use wide field of view cylinders to determine the sky positions for a large sample of FRBs, revealing their positions within their host galaxies to subarcsecond precision. In the meantime, TONE’s $\sim3333~\mathrm{km}$ baseline with CHIME proves to be an excellent testbed for the development and characterization of single-pulse VLBI techniques at the time of discovery. This work describes the TONE instrument, its sensitivity, and its astrometric precision in single-pulse VLBI. We believe that our astrometric errors are dominated by uncertainties in the clock measurements which build up between successive Crab pulsar calibrations which happen every $\approx 24~\mathrm{h}$; the wider fields of view and higher sensitivity of the Outriggers will provide opportunities for higher-cadence calibration. At present, CHIME-TONE localizations of the Crab pulsar yield systematic localization errors of ${0.1}-{0.2}~\mathrm{arcsec}$ – comparable to the resolution afforded by state-of-the-art optical instruments ($\sim 0.05 ~\mathrm{arcsec}$).

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P. Sanghavi, C. Leung, K. Bandura, et. al.
Fri, 21 Apr 23
24/60

Comments: 31 Pages, 25 Figures, To be submitted to Journal of Astronomical Instrumentation

Modeling Charge Cloud Dynamics in Cross Strip Semiconductor Detectors [IMA]

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http://arxiv.org/abs/2304.09713


When a $\gamma$-ray interacts in a semiconductor detector, the resulting electron-hole charge clouds drift towards their respective electrodes for signal collection. These charge clouds will expand over time due to both thermal diffusion and mutual electrostatic repulsion. Solutions to the resulting charge profiles are well understood for the limiting cases accounting for only diffusion and only repulsion, but the general solution including both effects can only be solved numerically. Previous attempts to model these effects have taken into account the broadening of the charge profile due to both effects, but have simplified the shape of the profile by assuming Gaussian distributions. However, the detailed charge profile can have important impacts on charge sharing in multi-electrode strip detectors. In this work, we derive an analytical approximation to the general solution, including both diffusion and repulsion, that closely replicates both the width and the detailed shape of the charge profiles. This analytical solution simplifies the modeling of charge clouds in semiconductor strip detectors.

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S. Boggs
Thu, 20 Apr 23
4/57

Comments: Accepted for publication in Nuclear Instruments and Methods in Physics Research A

Numerically studying the degeneracy problem in extreme finite-source microlensing events [IMA]

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http://arxiv.org/abs/2304.09529


Most transit microlensing events due to very low-mass lens objects suffer from extreme finite-source effects. While modeling their light curves, there is a known continuous degeneracy between their relevant lensing parameters, i.e., the source angular radius normalized to the angular Einstein radius $\rho_{\star}$, the Einstein crossing time $t_{\rm E}$, the lens impact parameter $u_{0}$, the blending parameter, and the stellar apparent magnitude. In this work, I numerically study the origin of this degeneracy. I find that these light curves have 5 observational parameters (i.e., the baseline magnitude, the maximum deviation in the magnification factor, the Full Width at Half Maximum $\rm{FWHM}=2 t_{\rm{HM}}$, the deviation from top-hat model, the time of the maximum time-derivative of microlensing light curves $T_{\rm{max}}=t_{\rm E}\sqrt{\rho_{\star}^{2}-u_{0}^{2}}$). For extreme finite-source microlensing events due to uniform source stars we get $t_{\rm{HM}}\simeq T_{\rm{max}}$, and the deviation from the top-hat model tends to zero which both cause the known continuous degeneracy. When either $\rho_{\star}\lesssim10$ or the limb-darkening effect is considerable $t_{\rm{HM}}$, and $T_{\rm{max}}$ are two independent observational parameters. I use a numerical approach, i.e., Random Forests containing $100$-$120$ Decision Trees, to study how these observational parameters are efficient in yielding the lensing parameters. These machine learning models find the mentioned 5 lensing parameters for finite-source microlensing events from uniform, and limb-darkened source stars with the average $R^{2}$-scores of $0.87$, and $0.84$, respectively. $R^{2}$-score for evaluating the lens impact parameter gets worse on adding limb darkening, and for extracting the limb-darkening coefficient itself this score falls as low as $0.67$.

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S. Sajadian
Thu, 20 Apr 23
25/57

Comments: 10 pages, 6 figures

Fabrication of a 64-Pixel TES Microcalorimeter Array with Iron Absorbers Uniquely Designed for 14.4-keV Solar Axion Search [IMA]

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http://arxiv.org/abs/2304.09539


If a hypothetical elementary particle called an axion exists, to solve the strong CP problem, a 57Fe nucleus in the solar core could emit a 14.4-keV monochromatic axion through the M1 transition. If such axions are once more transformed into photons by a 57Fe absorber, a transition edge sensor (TES) X-ray microcalorimeter should be able to detect them efficiently. We have designed and fabricated a dedicated 64-pixel TES array with iron absorbers for the solar axion search. In order to decrease the effect of iron magnetization on spectroscopic performance, the iron absorber is placed next to the TES while maintaining a certain distance. A gold thermal transfer strap connects them. We have accomplished the electroplating of gold straps with high thermal conductivity. The residual resistivity ratio (RRR) was over 23, more than eight times higher than a previous evaporated strap. In addition, we successfully electroplated pure-iron films of more than a few micrometers in thickness for absorbers and a fabricated 64-pixel TES calorimeter structure.

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Y. Yagi, T. Hayashi, K. Tanaka, et. al.
Thu, 20 Apr 23
36/57

Comments: 5 pages, 5 figures, published in IEEE Transactions on Applied Superconductivity on 8 March 2023

Persistent and occasional: searching for the variable population of the ZTF/4MOST sky using ZTF data release 11 [IMA]

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http://arxiv.org/abs/2304.08519


We present a variability, color and morphology based classifier, designed to identify transients, persistently variable, and non-variable sources, from the Zwicky Transient Facility (ZTF) Data Release 11 (DR11) light curves of extended and point sources. The main motivation to develop this model was to identify active galactic nuclei (AGN) at different redshift ranges to be observed by the 4MOST ChANGES project. Still, it serves as a more general time-domain astronomy study. The model uses nine colors computed from CatWISE and PS1, a morphology score from PS1, and 61 single-band variability features computed from the ZTF DR11 g and r light curves. We trained two versions of the model, one for each ZTF band. We used a hierarchical local classifier per parent node approach, where each node was composed of a balanced random forest model. We adopted a 17-class taxonomy, including non-variable stars and galaxies, three transient classes, five classes of stochastic variables, and seven classes of periodic variables. The macro averaged precision, recall and F1-score are 0.61, 0.75, and 0.62 for the g-band model, and 0.60, 0.74, and 0.61, for the r-band model. When grouping the four AGN classes into one single class, its precision, recall, and F1-score are 1.00, 0.95, and 0.97, respectively, for both the g and r bands. We applied the model to all the sources in the ZTF/4MOST overlapping sky, avoiding ZTF fields covering the Galactic bulge, including 86,576,577 light curves in the g-band and 140,409,824 in the r-band. Only 0.73\% of the g-band light curves and 2.62\% of the r-band light curves were classified as stochastic, periodic, or transient with high probability ($P_{init}\geq0.9$). We found that, in general, more reliable results are obtained when using the g-band model. Using the latter, we identified 384,242 AGN candidates, 287,156 of which have $P_{init}\geq0.9$.

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P. Sánchez-Sáez, J. Arredondo, A. Bayo, et. al.
Wed, 19 Apr 23
35/58

Comments: Accepted for publication in Astronomy & Astrophysics. Abstract shortened for arXiv. Tables containing the classifications and features for the ZTF g and r bands, and the labeled sets will be available at CDS. Individual catalogs per class and band, as well as the labeled set catalogs, can be downloaded at Zenodo DOI:10.5281/zenodo.7826045

The Simons Observatory: Beam characterization for the Small Aperture Telescopes [IMA]

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http://arxiv.org/abs/2304.08995


We use time-domain simulations of Jupiter observations to test and develop a beam reconstruction pipeline for the Simons Observatory Small Aperture Telescopes. The method relies on a map maker that estimates and subtracts correlated atmospheric noise and a beam fitting code designed to compensate for the bias caused by the map maker. We test our reconstruction performance for four different frequency bands against various algorithmic parameters, atmospheric conditions and input beams. We additionally show the reconstruction quality as function of the number of available observations and investigate how different calibration strategies affect the beam uncertainty. For all of the cases considered, we find good agreement between the fitted results and the input beam model within a ~1.5% error for a multipole range l = 30 – 700.

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N. Dachlythra, A. Duivenvoorden, J. Gudmundsson, et. al.
Wed, 19 Apr 23
45/58

Comments: 22 pages, 21 figures, to be submitted to ApJ

Noise in the LIGO Livingston Gravitational Wave Observatory due to Trains [IMA]

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http://arxiv.org/abs/2304.07477


Environmental seismic disturbances limit the sensitivity of LIGO gravitational wave detectors. Trains near the LIGO Livingston detector produce low frequency (0.5-10 Hz) ground noise that couples into the gravitational wave sensitive frequency band (10-100 Hz) through light reflected in mirrors and other surfaces. We investigate the effect of trains during the Advanced LIGO third observing run, and propose a method to search for narrow band seismic frequencies responsible for contributing to increases in scattered light. Through the use of the linear regression tool Lasso (least absolute shrinkage and selection operator) and glitch correlations, we identify the most common seismic frequencies that correlate with increases in detector noise as 0.6-0.8 Hz, 1.7-1.9 Hz, 1.8-2.0 Hz, and 2.3-2.5 Hz in the LIGO Livingston corner station.

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J. Glanzer, S. Soni, J. Spoon, et. al.
Tue, 18 Apr 23
14/80

Comments: 18 pages (including bibliography), 17 figures, 2 tables, and 1 appendix. Submitted to Classical and Quantum Gravity

Updates to ALMA Site Properties: using the ESO-Allegro Phase RMS database — ALMA Memo 624 [IMA]

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http://arxiv.org/abs/2304.08318


We present a long-term overview of the atmospheric phase stability at the Atacama Large Millimeter/submillimeter Array (ALMA) site, using >5 years of data, that acts as the successor to the studies summarized two decades ago by Evans et al 2003. Importantly, we explore the atmospheric variations, the `phase RMS’, and associated metadata of over 17000 accrued ALMA observations taken since Cycle 3 (2015) by using the Bandpass calibrator source scans. We indicate the temporal phase RMS trends for average baseline lengths of 500, 1000, 5000, and 10000m, in contrast to the old stability studies that used a single 300m baseline phase monitor system. At the ALMA site, on the Chajnantor plateau, we report the diurnal variations and monthly changes in the phase RMS on ALMA relevant baselines lengths, measured directly from data, and we reaffirm such trends in atmospheric transmission (via Precipitable Water Vapour – PWV). We confirm that day observations have respectively higher phase RMS and PWV in contrast to night, while the monthly variations show Chilean winter (June – August) providing the best, high-frequency and long-baseline observing conditions – low (stable) phase RMS and low PWV. Yet, not all good phase stability condition occur when the PWV is low. Measurements of the phase RMS as a function of short timescales, 30 to 240s, that tie with typical target source scan times, and as a function of baseline length indicate that phase variations are smaller for short timescales and baselines and larger for longer timescales and baselines. We illustrate that fast-switching phase-referencing techniques, that allow short target scan times, could work well in reducing the phase RMS to suitable levels specifically for high-frequencies (Band 8, 9 and 10), long-baselines, and the two combined.

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L. Maud, A. Pérez-Sánchez, Y. Asaki, et. al.
Tue, 18 Apr 23
27/80

Comments: 34 pages, 19 Figures, 10 Tables ALMA Memo 624: this https URL

Gas selection for Xe-based LCP-GEM detectors onboard the CubeSat X-ray observatory NinjaSat [IMA]

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http://arxiv.org/abs/2304.08321


We present a gas selection for Xe-based gas electron multiplier (GEM) detectors, Gas Multiplier Counters (GMCs) onboard the CubeSat X-ray observatory NinjaSat. To achieve an energy bandpass of 2-50 keV, we decided to use a Xe-based gas mixture at a pressure of 1.2 atm that is sensitive to high-energy X-rays. In addition, an effective gain of over 300 is required for a single GEM so that the 2 keV X-ray signal can be sufficiently larger than the electrical noise. At first, we measured the effective gains of GEM in nine Xe-based gas mixtures (combinations of Xe, Ar, CO2, CH4, and dimethyl ether; DME) at 1.0 atm. The highest gains were obtained with Xe/Ar/DME mixtures, while relatively lower gains were obtained with Xe/Ar/CO2, Xe/Ar/CH4, and Xe+quencher mixtures. Based on these results, we selected the Xe/Ar/DME (75%/24%/1%) mixture at 1.2 atm as the sealed gas for GMC. Then we investigated the dependence of an effective gain on the electric fields in the drift and induction gaps ranging from 100-650 V cm$^{-1}$ and 500-5000 V cm$^{-1}$, respectively, in the selected gas mixture. The effective gain weakly depended on the drift field while it was almost linearly proportional to the induction field: 2.4 times higher at 5000 V cm$^{-1}$ than at 1000 V cm$^{-1}$. With the optimal induction and drift fields, the flight model GMC achieves an effective gain of 460 with an applied GEM voltage of 590 V.

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T. Takeda, T. Tamagawa, T. Enoto, et. al.
Tue, 18 Apr 23
34/80

Comments: 7th international conference on Micro Pattern Gaseous Detectors 2022 – MPGD2022, 3 pages, 2 figures

Using Dark Energy Explorers and Machine Learning to Enhance the Hobby-Eberly Telescope Dark Energy Experiment [IMA]

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http://arxiv.org/abs/2304.07348


We present analysis using a citizen science campaign to improve the cosmological measures from the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX). The goal of HETDEX is to measure the Hubble expansion rate, $H(z)$, and angular diameter distance, $D_A(z)$, at $z =$ 2.4, each to percent-level accuracy. This accuracy is determined primarily from the total number of detected Lyman-$\alpha$ emitters (LAEs), the false positive rate due to noise, and the contamination due to [O II] emitting galaxies. This paper presents the citizen science project, Dark Energy Explorers, with the goal of increasing the number of LAEs, decreasing the number of false positives due to noise and the [O II] galaxies. Initial analysis shows that citizen science is an efficient and effective tool for classification most accurately done by the human eye, especially in combination with unsupervised machine learning. Three aspects from the citizen science campaign that have the most impact are 1) identifying individual problems with detections, 2) providing a clean sample with 100% visual identification above a signal-to-noise cut, and 3) providing labels for machine learning efforts. Since the end of 2022, Dark Energy Explorers has collected over three and a half million classifications by 11,000 volunteers in over 85 different countries around the world. By incorporating the results of the Dark Energy Explorers we expect to improve the accuracy on the $D_A(z)$ and $H(z)$ parameters at $z =$ 2.4 by 10 – 30%. While the primary goal is to improve on HETDEX, Dark Energy Explorers has already proven to be a uniquely powerful tool for science advancement and increasing accessibility to science worldwide.

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L. House, K. Gebhardt, K. Finkelstein, et. al.
Tue, 18 Apr 23
35/80

Comments: 14 pages, 6 figures, accepted for publication in The Astrophysical Journal

Anatomy of parameter-estimation biases in overlapping gravitational-wave signals [IMA]

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http://arxiv.org/abs/2304.06734


In future gravitational-wave (GW) detections, a large number of overlapping GW signals will appear in the data stream of detectors. When extracting information from one signal, the presence of other signals can cause large parameter estimation biases. Using the Fisher matrix (FM), we develop a bias analysis procedure to investigate how each parameter of other signals affects the inference biases. Taking two-signal overlapping as an example, we show detailedly and quantitatively that the biases essentially originate from the overlapping of the frequency evolution. Furthermore, we find that the behaviors of the correlation coefficients between the parameters of the two signals are similar to the biases. Both of them can be used as characterization of the influence between signals. We also corroborate the bias results of the FM method with full Bayesian analysis. Our results provide powerful guidance for parameter estimation, and the analysis methodology is easy to generalize.

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Z. Wang, D. Liang, J. Zhao, et. al.
Mon, 17 Apr 23
5/51

Comments: 29 pages, 13 figures

Lossy Compression of Large-Scale Radio Interferometric Data [IMA]

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http://arxiv.org/abs/2304.07050


This work proposes to reduce visibility data volume using a baseline-dependent lossy compression technique that preserves smearing at the edges of the field-of-view. We exploit the relation of the rank of a matrix and the fact that a low-rank approximation can describe the raw visibility data as a sum of basic components where each basic component corresponds to a specific Fourier component of the sky distribution. As such, the entire visibility data is represented as a collection of data matrices from baselines, instead of a single tensor. The proposed methods are formulated as follows: provided a large dataset of the entire visibility data; the first algorithm, named $simple~SVD$ projects the data into a regular sampling space of rank$-r$ data matrices. In this space, the data for all the baselines has the same rank, which makes the compression factor equal across all baselines. The second algorithm, named $BDSVD$ projects the data into an irregular sampling space of rank$-r_{pq}$ data matrices. The subscript $pq$ indicates that the rank of the data matrix varies across baselines $pq$, which makes the compression factor baseline-dependent. MeerKAT and the European Very Long Baseline Interferometry Network are used as reference telescopes to evaluate and compare the performance of the proposed methods against traditional methods, such as traditional averaging and baseline-dependent averaging (BDA). For the same spatial resolution threshold, both $simple~SVD$ and $BDSVD$ show effective compression by two-orders of magnitude higher than traditional averaging and BDA. At the same space-saving rate, there is no decrease in spatial resolution and there is a reduction in the noise variance in the data which improves the S/N to over $1.5$ dB at the edges of the field-of-view.

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M. Atemkeng, S. Perkins, E. Seck, et. al.
Mon, 17 Apr 23
19/51

Comments: N/A

Optical characteristics and capabilities of the successive versions of Meudon and Haute Provence H$α$ heliographs (1954-2004) [IMA]

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http://arxiv.org/abs/2304.07055


H$\alpha$ heliographs are imaging instruments designed to produce monochromatic images of the solar chromosphere at fast cadence (60 s or less). They are designed to monitor efficiently dynamic phenomena of solar activity, such as flares or material ejections. Meudon and Haute Provence observatories started systematic observations in the frame of the International Geophysical Year (1957) with Lyot filters. This technology evolved several times until 1985 with tunable filters allowing to observe alternatively the line wings and core (variable wavelength). More than 6 million images were produced during 50 years, mostly on 35 mm films (catalogs are available on-line). We present in this paper the optical characteristics and the capabilities of the successive versions of the H$\alpha$ heliographs in operation between 1954 and 2004, and describe briefly the new heliograph (MeteoSpace) which will be commissioned in 2023 at Calern observatory.

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J. Malherbe
Mon, 17 Apr 23
25/51

Comments: N/A

Results from the ARIANNA high-energy neutrino detector [IMA]

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http://arxiv.org/abs/2304.07179


The ARIANNA in-ice radio detector explores the detection of UHE neutrinos with shallow detector stations on the Ross Ice Shelf and the South Pole. Here, we present recent results that lay the foundation for future large-scale experiments. We show a limit on the UHE neutrino flux derived from ARIANNA data, measurements of the more abundant air showers, results from in-situ measurement campaigns, a study of a potential background from internal reflection layers, and give an outlook of future detector improvements.

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C. Glaser
Mon, 17 Apr 23
30/51

Comments: Proceedings of the 9th ARENA workshop 2022

A brief History of Image Sensors in the Optical [IMA]

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http://arxiv.org/abs/2304.07121


Image sensors, most notably the Charge Coupled Device (CCD), have revolutionized observational astronomy as perhaps the most important innovation after photography. Since the 50th anniversary of the invention of the CCD has passed in 2019, it is time to review the development of detectors for the visible wavelength range, starting with the discovery of the photoelectric effect and first experiments to utilize it for the photometry of stars at Sternwarte Babelsberg in 1913, over the invention of the CCD, its development at the Jet Propulsion Laboratory, to the high performance CCD and CMOS imagers that are available off-the-shelf today.

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M. Roth
Mon, 17 Apr 23
34/51

Comments: 9 pages, 10 figures. Presented at SDW2022, accepted for publication in Special Issue of Astronomische Nachrichten

Performance of TES X-Ray Microcalorimeters Designed for 14.4-keV Solar Axion Search [IMA]

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http://arxiv.org/abs/2304.07068


A 57Fe nucleus in the solar core could emit a 14.4-keV monochromatic axion through the M1 transition if a hypothetical elementary particle, axion, exists to solve the strong CP problem. Transition edge sensor (TES) X-ray microcalorimeters can detect such axions very efficiently if they are again converted into photons by a 57Fe absorber. We have designed and produced a dedicated TES array with 57Fe absorbers for the solar axion search. The iron absorber is set next to the TES, keeping a certain distance to reduce the iron-magnetization effect on the spectroscopic performance. A gold thermal transfer strap connects them. A sample pixel irradiated from a 55Fe source detected 698 pulses. In contrast to thermal simulations, we consider that the pulses include either events produced in an iron absorber or gold strap at a fraction dependent on the absorption rate of each material. Furthermore, photons deposited on the iron absorber are detected through the strap as intended. The identification of all events still needs to be completed. However, we successfully operated the TES with the unique design under iron magnetization for the first time.

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Y. Yagi, R. Konno, T. Hayash, et. al.
Mon, 17 Apr 23
48/51

Comments: 10 pages, 6 figures, published in Journal of Low Temperature Physics on 4 February 2023

Quasi Real-Time Autonomous Satellite Detection and Orbit Estimation [IMA]

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http://arxiv.org/abs/2304.06227


A method of near real-time detection and tracking of resident space objects (RSOs) using a convolutional neural network (CNN) and linear quadratic estimator (LQE) is proposed. Advances in machine learning architecture allow the use of low-power/cost embedded devices to perform complex classification tasks. In order to reduce the costs of tracking systems, a low-cost embedded device will be used to run a CNN detection model for RSOs in unresolved images captured by a gray-scale camera and small telescope. Detection results computed in near real-time are then passed to an LQE to compute tracking updates for the telescope mount, resulting in a fully autonomous method of optical RSO detection and tracking. Keywords: Space Domain Awareness, Neural Networks, Real-Time, Object Detection, Embedded Systems.

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J. Jordan, D. Posada, M. Gillette, et. al.
Fri, 14 Apr 23
25/64

Comments: SPIE Defense and Commercial 2023, Orlando, FL

Precision measurement of the index of refraction of deep glacial ice at radio frequencies at Summit Station, Greenland [IMA]

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http://arxiv.org/abs/2304.06181


Glacial ice is used as a target material for the detection of ultra-high energy neutrinos, by measuring the radio signals that are emitted when those neutrinos interact in the ice. Thanks to the large attenuation length at radio frequencies, these signals can be detected over distances of several kilometers. One experiment taking advantage of this is the Radio Neutrino Observatory Greenland (RNO-G), currently under construction at Summit Station, near the apex of the Greenland ice sheet. These experiments require a thorough understanding of the dielectric properties of ice at radio frequencies. Towards this goal, calibration campaigns have been undertaken at Summit, during which we recorded radio reflections off internal layers in the ice sheet. Using data from the nearby GISP2 and GRIP ice cores, we show that these reflectors can be associated with features in the ice conductivity profiles; we use this connection to determine the index of refraction of the bulk ice as n=1.778 +/- 0.006.

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J. Aguilar, P. Allison, D. Besson, et. al.
Fri, 14 Apr 23
35/64

Comments: N/A

Growing Pains: Understanding the Impact of Likelihood Uncertainty on Hierarchical Bayesian Inference for Gravitational-Wave Astronomy [IMA]

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http://arxiv.org/abs/2304.06138


Observations of gravitational waves emitted by merging compact binaries have provided tantalising hints about stellar astrophysics, cosmology, and fundamental physics. However, the physical parameters describing the systems, (mass, spin, distance) used to extract these inferences about the Universe are subject to large uncertainties. The current method of performing these analyses requires performing many Monte Carlo integrals to marginalise over the uncertainty in the properties of the individual binaries and the survey selection bias. These Monte Carlo integrals are subject to fundamental statistical uncertainties. Previous treatments of this statistical uncertainty has focused on ensuring the precision of the inferred inference is unaffected, however, these works have neglected the question of whether sufficient accuracy can also be achieved. In this work, we provide a practical exploration of the impact of uncertainty in our analyses and provide a suggested framework for verifying that astrophysical inferences made with the gravitational-wave transient catalogue are accurate. Applying our framework to models used by the LIGO-Virgo-Kagra collaboration, we find that Monte Carlo uncertainty in estimating the survey selection bias is the limiting factor in our ability to probe narrow populations model and this will rapidly grow more problematic as the size of the observed population increases.

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C. Talbot and J. Golomb
Fri, 14 Apr 23
52/64

Comments: 8 pages, 6 figures

Capella: A Space-only High-frequency Radio VLBI Network Formed by a Constellation of Small Satellites [IMA]

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http://arxiv.org/abs/2304.06482


Very long baseline radio interferometry (VLBI) with ground-based observatories is limited by the size of Earth, the geographic distribution of antennas, and the transparency of the atmosphere. In this whitepaper, we present Capella, a tentative design of a space-only VLBI system. Using four small (<500 kg) satellites on two orthogonal polar low-Earth orbits, and single-band heterodyne receivers operating at frequencies around 690 GHz, the interferometer is able to achieve angular resolutions of approximately 7 microarcsec. Within a total observing time of three days, a near-complete uv plane coverage can be reached, with a 1-sigma point source sensitivity as good as about 6~mJy for an instantaneous bandwidth of 1 GHz. The required downlink data rates of >10 Gbps can be reached through near-infrared laser communication; depending on the actual downlink speed, one or multiple ground communication stations are necessary. We note that all key technologies required for the Capella system are already available, some of them off-the-shelf. Data can be correlated using dedicated versions of existing Fourier transform (FX) software correlators; dedicated routines will be needed to handle the effects of orbital motion, including relativistic corrections. With the specifications assumed in this whitepaper, Capella will be able to address a range of science cases, including: photon rings around supermassive black holes; the acceleration and collimation zones of plasma jets emitted from the vicinity of supermassive black holes; the chemical composition of accretion flows into active galactic nuclei through observations of molecular absorption lines; mapping supermassive binary black holes; the magnetic activity of stars; and nova eruptions of symbiotic binary stars – and, like any substantially new observing technique, has the potential for unexpected discoveries.

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S. Trippe, T. Jung, J. Lee, et. al.
Fri, 14 Apr 23
63/64

Comments: 18 pages, 2 figures, 1 table. Whitepaper version 1.0. Living document, will be updated when necessary

Dynamics of space debris removal: A review [IMA]

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http://arxiv.org/abs/2304.05709


Space debris, also known as “space junk,” presents a significant challenge for all space exploration activities, including those involving human-onboard spacecraft such as SpaceX’s Crew Dragon and the International Space Station. The amount of debris in space is rapidly increasing and poses a significant environmental concern. Various studies and research have been conducted on space debris capture mechanisms, including contact and contact-less capturing methods, in Earth’s orbits. While advancements in technology, such as telecommunications, weather forecasting, high-speed internet, and GPS, have benefited society, their improper and unplanned usage has led to the creation of debris. The growing amount of debris poses a threat of collision with the International Space Station, shuttle, and high-value satellites, and is present in different parts of Earth’s orbit, varying in size, shape, speed, and mass. As a result, capturing and removing space debris is a challenging task. This review article provides an overview of space debris statistics and specifications, and focuses on ongoing mitigation strategies, preventive measures, and statutory guidelines for removing and preventing debris creation, emphasizing the serious issue of space debris damage to space agencies and relevant companies.

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M. Bigdeli, R. Srivastava and M. Scaraggi
Thu, 13 Apr 23
4/59

Comments: N/A

A Gaussian process cross-correlation approach to time delay estimation in active galactic nuclei [IMA]

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http://arxiv.org/abs/2304.05536


We present a probabilistic cross-correlation approach to estimate time delays in the context of reverberation mapping (RM) of Active Galactic Nuclei (AGN). We reformulate the traditional interpolated cross-correlation method as a statistically principled model that delivers a posterior distribution for the delay. The method employs Gaussian processes as a model for observed AGN light curves. We describe the mathematical formalism and demonstrate the new approach using both simulated light curves and available RM observations. The proposed method delivers a posterior distribution for the delay that accounts for observational noise and the non-uniform sampling of the light curves. This feature allow us to fully quantify its uncertainty and propagate it to subsequent calculations of dependent physical quantities, e.g., black hole masses. It delivers out-of-sample predictions, which enables us to subject it to model selection and it can calculate the joint posterior delay for more than two light curves. Because of the numerous advantages of our reformulation and the simplicity of its application, we anticipate that our method will find favour not only in the specialised community of RM, but in all fields where cross-correlation analysis is performed. We provide the algorithms and examples of their application as part of our Julia GPCC package.

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F. Nuñez, N. Gianniotis and K. Polsterer
Thu, 13 Apr 23
24/59

Comments: 13 pages, 16 figures, Accepted for publication in Astronomy and Astrophysics

A Glimpse of International Cooperation in Astrophysical Sciences in India [IMA]

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http://arxiv.org/abs/2304.05626


Astronomy and Astrophysics is an observational science dealing with celestial objects. Aryabhatta Research Institute of Observational Sciences (ARIES) is one of the premier institutions in astronomy and astrophysics and has contributed significantly in this field. No doubt, India is a part of several mega-science projects in the domain of Astronomy and Astrophysics, such as the Thirty Meter Telescope (TMT); Square Kilometer Array (SKA) and Laser Interferometer Gravitational-wave Observatory (LIGO) projects. Growing engagement of India with mega-science projects has brought a positive impact on its science and technology landscape. A few such collaborations are mentioned to demonstrate that international cooperation are necessary in the field of Astrophysical sciences.

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R. Sagar
Thu, 13 Apr 23
43/59

Comments: 4 pages, 1 figure, Invited article

SBI++: Flexible, Ultra-fast Likelihood-free Inference Customized for Astronomical Application [IMA]

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http://arxiv.org/abs/2304.05281


Flagship near-future surveys targeting $10^8-10^9$ galaxies across cosmic time will soon reveal the processes of galaxy assembly in unprecedented resolution. This creates an immediate computational challenge on effective analyses of the full data-set. With simulation-based inference (SBI), it is possible to attain complex posterior distributions with the accuracy of traditional methods but with a $>10^4$ increase in speed. However, it comes with a major limitation. Standard SBI requires the simulated data to have identical characteristics to the observed data, which is often violated in astronomical surveys due to inhomogeneous coverage and/or fluctuating sky and telescope conditions. In this work, we present a complete SBI-based methodology, “SBI$^{++}$,” for treating out-of-distribution measurement errors and missing data. We show that out-of-distribution errors can be approximated by using standard SBI evaluations and that missing data can be marginalized over using SBI evaluations over nearby data realizations in the training set. In addition to the validation set, we apply SBI$^{++}$ to galaxies identified in extragalactic images acquired by the James Webb Space Telescope, and show that SBI$^{++}$ can infer photometric redshifts at least as accurately as traditional sampling methods and crucially, better than the original SBI algorithm using training data with a wide range of observational errors. SBI$^{++}$ retains the fast inference speed of $\sim$1 sec for objects in the observational training set distribution, and additionally permits parameter inference outside of the trained noise and data at $\sim$1 min per object. This expanded regime has broad implications for future applications to astronomical surveys.

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B. Wang, J. Leja, V. Villar, et. al.
Wed, 12 Apr 23
6/45

Comments: 12 pages, 5 figures. Code and a Jupyter tutorial are made publicly available at this https URL

The International Pulsar Timing Array checklist for the detection of nanohertz gravitational waves [IMA]

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http://arxiv.org/abs/2304.04767


Pulsar timing arrays (PTAs) provide a way to detect gravitational waves at nanohertz frequencies. In this band, the most likely signals are stochastic, with a power spectrum that rises steeply at lower frequencies. Indeed, the observation of a common red noise process in pulsar-timing data suggests that the first credible detection of nanohertz-frequency gravitational waves could take place within the next few years. The detection process is complicated by the nature of the signals and the noise: the first observational claims will be statistical inferences drawn at the threshold of detectability. To demonstrate that gravitational waves are creating some of the noise in the pulsar-timing data sets, observations must exhibit the Hellings and Downs curve — the angular correlation function associated with gravitational waves — as well as demonstrating that there are no other reasonable explanations. To ensure that detection claims are credible, the International Pulsar Timing Array (IPTA) has a formal process to vet results prior to publication. This includes internal sharing of data and processing pipelines between different PTAs, enabling independent cross-checks and validation of results. To oversee and validate any detection claim, the IPTA has also created an eight-member Detection Committee (DC) which includes four independent external members. IPTA members will only publish their results after a formal review process has concluded. This document is the initial DC checklist, describing some of the conditions that should be fulfilled by a credible detection.

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B. Allen, S. Dhurandhar, Y. Gupta, et. al.
Wed, 12 Apr 23
12/45

Comments: 6 pages

The James Webb Space Telescope Mission [IMA]

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http://arxiv.org/abs/2304.04869


Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.

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J. Gardner, J. Mather, R. Abbott, et. al.
Wed, 12 Apr 23
20/45

Comments: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figures

Multicolor and multi-spot observations of Starlink's Visorsat [IMA]

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http://arxiv.org/abs/2304.05191


This study provides the results of simultaneous multicolor observations for the first Visorsat (STARLINK-1436) and the ordinary Starlink satellite, STARLINK-1113 in the $U$, $B$, $V$, $g’$, $r$, $i$, $R_{\rm C}$, $I_{\rm C}$, $z$, $J$, $H$, and $K_s$ bands to quantitatively investigate the extent to which Visorsat reduces its reflected light. Our results are as follows: (1) in most cases, Virorsat is fainter than STARLINK-1113, and the sunshade on Visorsat, therefore, contributes to the reduction of the reflected sunlight; (2) the magnitude at 550 km altitude (normalized magnitude) of both satellites often reaches the naked-eye limiting magnitude ($<$ 6.0); (3) from a blackbody radiation model of the reflected flux, the peak of the reflected components of both satellites is around the $z$ band; and (4) the albedo of the near infrared range is larger than that of the optical range. Under the assumption that Visorsat and STARLINK-1113 have the same reflectivity, we estimate the covering factor, $C_{\rm f}$, of the sunshade on Visorsat, using the blackbody radiation model: the covering factor ranges from $0.18 \leq C_{\rm f} \leq 0.92$. From the multivariable analysis of the solar phase angle (Sun-target-observer), the normalized magnitude, and the covering factor, the phase angle versus covering factor distribution presents a moderate anti-correlation between them, suggesting that the magnitudes of Visorsat depend not only on the phase angle but also on the orientation of the sunshade along our line of sight. However, the impact on astronomical observations from Visorsat-designed satellites remains serious. Thus, new countermeasures are necessary for the Starlink satellites to further reduce reflected sunlight.

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T. Horiuchi, H. Hanayama, M. Ohishi, et. al.
Wed, 12 Apr 23
22/45

Comments: 31 pages, 9 figures, published in PASJ

The Large Array Survey Telescope — System Overview and Performances [IMA]

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http://arxiv.org/abs/2304.04796


The Large Array Survey Telescope (LAST) is a wide-field visible-light telescope array designed to explore the variable and transient sky with a high cadence. LAST will be composed of 48, 28-cm f/2.2 telescopes (32 already installed) equipped with full-frame backside-illuminated cooled CMOS detectors. Each telescope provides a field of view (FoV) of 7.4 deg^2 with 1.25 arcsec/pix, while the system FoV is 355 deg^2 in 2.9 Gpix. The total collecting area of LAST, with 48 telescopes, is equivalent to a 1.9-m telescope. The cost-effectiveness of the system (i.e., probed volume of space per unit time per unit cost) is about an order of magnitude higher than most existing and under-construction sky surveys. The telescopes are mounted on 12 separate mounts, each carrying four telescopes. This provides significant flexibility in operating the system. The first LAST system is under construction in the Israeli Negev Desert, with 32 telescopes already deployed. We present the system overview and performances based on the system commissioning data. The Bp 5-sigma limiting magnitude of a single 28-cm telescope is about 19.6 (21.0), in 20 s (20×20 s). Astrometric two-axes precision (rms) at the bright-end is about 60 (30)\,mas in 20\,s (20×20 s), while absolute photometric calibration, relative to GAIA, provides ~10 millimag accuracy. Relative photometric precision, in a single 20 s (320 s) image, at the bright-end measured over a time scale of about 60 min is about 3 (1) millimag. We discuss the system science goals, data pipelines, and the observatory control system in companion publications.

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E. Ofek, S. Ben-Ami, D. Polishook, et. al.
Wed, 12 Apr 23
24/45

Comments: Submitted to PASP, 15pp

Measuring tidal effects with the Einstein Telescope: A design study [IMA]

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http://arxiv.org/abs/2304.05349


Over the last few years, there has been a large momentum to ensure that the third-generation era of gravitational wave detectors will find its realisation in the next decades, and numerous design studies have been ongoing for some time. Some of the main factors determining the cost of the Einstein Telescope lie in the length of the interferometer arms and its shape: L-shaped detectors versus a single triangular configuration. Both designs are further expected to include a xylophone configuration for improvement on both ends of the frequency bandwidth of the detector. We consider binary neutron star sources in our study, as examples of sources already observed with the current generation detectors and ones which hold most promise given the broader frequency band and higher sensitivity of the third-generation detectors. We estimate parameters of the sources, with different kinds of configurations of the Einstein Telescope detector, varying arm-lengths as well as shapes and alignments. Overall, we find little improvement with respect to changing the shape, or alignment. However, there are noticeable differences in the estimates of some parameters, including tidal deformability, when varying the arm-length of the detectors. In addition, we also study the effect of changing the laser power, and the lower limit of the frequency band in which we perform the analysis.

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A. Puecher, A. Samajdar and T. Dietrich
Wed, 12 Apr 23
25/45

Comments: 11 pages, 7 figures, 4 tables

Feature Guided Training and Rotational Standardisation for the Morphological Classification of Radio Galaxies [IMA]

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http://arxiv.org/abs/2304.05095


State-of-the-art radio observatories produce large amounts of data which can be used to study the properties of radio galaxies. However, with this rapid increase in data volume, it has become unrealistic to manually process all of the incoming data, which in turn led to the development of automated approaches for data processing tasks, such as morphological classification. Deep learning plays a crucial role in this automation process and it has been shown that convolutional neural networks (CNNs) can deliver good performance in the morphological classification of radio galaxies. This paper investigates two adaptations to the application of these CNNs for radio galaxy classification. The first adaptation consists of using principal component analysis (PCA) during preprocessing to align the galaxies’ principal components with the axes of the coordinate system, which will normalize the orientation of the galaxies. This adaptation led to a significant improvement in the classification accuracy of the CNNs and decreased the average time required to train the models. The second adaptation consists of guiding the CNN to look for specific features within the samples in an attempt to utilize domain knowledge to improve the training process. It was found that this adaptation generally leads to a stabler training process and in certain instances reduced overfitting within the network, as well as the number of epochs required for training.

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K. Brand, T. Grobler, W. Kleynhans, et. al.
Wed, 12 Apr 23
35/45

Comments: 20 pages, 17 figures, this is a pre-copyedited, author-produced PDF of an article accepted for publication in the Monthly Notices of the Royal Astronomical Society

Comparison of modified black-body fits for the estimation of dust optical depths in interstellar clouds [IMA]

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http://arxiv.org/abs/2304.05102


When dust far-infrared spectral energy distributions (SEDs) are fitted with a single modified black body (MBB), the optical depths tend to be underestimated. This is caused by temperature variations, and fits with several temperature components could lead to smaller errors. We want to quantify the performance of the standard model of a single MBB in comparison with some multi-component models. We are interested in both the accuracy and computational cost. We examine some cloud models relevant for interstellar medium studies. Synthetic spectra are fitted with a single MBB, a sum of several MBBs, and a sum of fixed spectral templates, but keeping the dust opacity spectral index fixed. When observations are used at their native resolution, the beam convolution becomes part of the fitting procedure. This increases the computational cost, but the analysis of large maps is still feasible with direct optimisation or even with Markov chain Monte Carlo methods. Compared to the single MBB fits, multi-component models can show significantly smaller systematic errors, at the cost of more statistical noise. The $\chi^2$ values of the fits are not a good indicator of the accuracy of the $\tau$ estimates, due to the potentially dominant role of the model errors. The single-MBB model also remains a valid alternative if combined with empirical corrections to reduce its bias. It is technically feasible to fit multi-component models to maps of millions of pixels. However, the SED model and the priors need to be selected carefully, and the model errors can only be estimated by comparing alternative models.

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M. Juvela
Wed, 12 Apr 23
44/45

Comments: Accepted to A&A

Measuring the properties of $f-$mode oscillations of a protoneutron star by third generation gravitational-wave detectors [IMA]

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http://arxiv.org/abs/2304.04283


Core-collapse supernovae are among the astrophysical sources of gravitational waves that could be detected by third-generation gravitational-wave detectors. Here, we analyze the gravitational-wave strain signals from two- and three-dimensional simulations of core-collapse supernovae generated using the code F{\sc{ornax}}. A subset of the two-dimensional simulations has non-zero core rotation at the core bounce. A dominant source of time changing quadrupole moment is the $l=2$ fundamental mode ($f-$ mode) oscillation of the proto-neutron star. From the time-frequency spectrogram of the gravitational-wave strain we see that, starting $\sim 400$ ms after the core bounce, most of the power lies within a narrow track that represents the frequency evolution of the $f-$mode oscillations. The $f-$mode frequencies obtained from linear perturbation analysis of the angle-averaged profile of the protoneutron star corroborate what we observe in the spectrograms of the gravitational-wave signal. We explore the measurability of the $f-$mode frequency evolution of protoneutron star for a supernova signal observed in the third-generation gravitational-wave detectors. Measurement of the frequency evolution can reveal information about the masses, radii, and densities of the proto-neutron stars. We find that if the third generation detectors observe a supernova within 10 kpc, we can measure these frequencies to within $\sim$90\% accuracy. We can also measure the energy emitted in the fundamental $f-$mode using the spectrogram data of the strain signal. We find that the energy in the $f-$mode can be measured to within 20\% error for signals observed by Cosmic Explorer using simulations with successful explosion, assuming source distances within 10 kpc.

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C. Afle, S. Kundu, J. Cammerino, et. al.
Tue, 11 Apr 23
5/63

Comments: 17 pages, 11 figures, 2 tables

ASAS-SN Sky Patrol V2.0 [IMA]

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http://arxiv.org/abs/2304.03791


The All-Sky Automated Survey for Supernovae (ASAS-SN) began observing in late-2011 and has been imaging the entire sky with nightly cadence since late 2017. A core goal of ASAS-SN is to release as much useful data as possible to the community. Working towards this goal, in 2017 the first ASAS-SN Sky Patrol was established as a tool for the community to obtain light curves from our data with no preselection of targets. Then, in 2020 we released static V-band photometry from 2013–2018 for 61 million sources. Here we describe the next generation ASAS-SN Sky Patrol, Version 2.0, which represents a major progression of this effort. Sky Patrol 2.0 provides continuously updated light curves for 111 million targets derived from numerous external catalogs of stars, galaxies, and solar system objects. We are generally able to serve photometry data within an hour of observation. Moreover, with a novel database architecture, the catalogs and light curves can be queried at unparalleled speed, returning thousands of light curves within seconds. Light curves can be accessed through a web interface (this http URL) or a Python client (https://asas-sn.ifa.hawaii.edu/documentation). The Python client can be used to retrieve up to 1 million light curves, generally limited only by bandwidth. This paper gives an updated overview of our survey, introduces the new Sky Patrol, and describes its system architecture. These results provide significant new capabilities to the community for pursuing multi-messenger and time-domain astronomy.

Read this paper on arXiv…

K. Hart, B. Shappee, D. Hey, et. al.
Tue, 11 Apr 23
8/63

Comments: Light curves can be accessed through a web interface this http URL, or a Python client at this http URL

Review of X-ray pulsar spacecraft autonomous navigation [IMA]

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http://arxiv.org/abs/2304.04154


This article provides a review on X-ray pulsar-based navigation (XNAV). The review starts with the basic concept of XNAV, and briefly introduces the past, present and future projects concerning XNAV. This paper focuses on the advances of the key techniques supporting XNAV, including the navigation pulsar database, the X-ray detection system, and the pulse time of arrival estimation. Moreover, the methods to improve the estimation performance of XNAV are reviewed. Finally, some remarks on the future development of XNAV are provided.

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Y. Wang, W. Zheng, S. Zhang, et. al.
Tue, 11 Apr 23
27/63

Comments: has been accepted by Chinese Journal of Aeronautics

Triumvirate: A Python/C++ package for three-point clustering measurements [IMA]

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http://arxiv.org/abs/2304.03643


Triumvirate is a Python/C++ package for measuring the three-point clustering statistics in large-scale structure (LSS) cosmological analyses. Given a catalogue of discrete particles (such as galaxies) with their spatial coordinates, it computes estimators of the multipoles of the three-point correlation function, also known as the bispectrum in Fourier space, in the tri-polar spherical harmonic (TripoSH) decomposition proposed by Sugiyama et al. (2019). The objective of Triumvirate is to provide efficient end-to-end measurement of clustering statistics which can be fed into downstream galaxy survey analyses to constrain and test cosmological models. To this end, it builds upon the original algorithms in the hitomi code developed by Sugiyama et al. (2018, 2019), and supplies a user-friendly interface with flexible input/output (I/O) of catalogue data and measurement results, with the built program configurable through external parameter files and tracked through enhanced logging and warning/exception handling. For completeness and complementarity, methods for measuring two-point clustering statistics are also included in the package.

Read this paper on arXiv…

M. Wang, F. Beutler and N. Sugiyama
Mon, 10 Apr 23
6/36

Comments: 5 pages. Submitted to JOSS. Code available at this https URL

Super-resolution imaging for the detection of low-energy ion tracks in fine-grained nuclear emulsions [IMA]

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http://arxiv.org/abs/2304.03645


We propose a new wide-field imaging method that exploits the Localized Surface Plasmon Resonance phenomenon to produce super-resolution images with an optical microscope equipped with a custom design polarization analyzer module. In this paper we describe the method and apply it to the analysis of low-energy carbon ion tracks implanted in a nuclear emulsion film. The result is then compared with the measurements of the same tracks carried out at an electronic microscope. The images set side by side show their close similarity. The resolution achieved with the current microscope setup is estimated to be about 60 nm.

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A. Alexandrov, T. Asada, F. Borbone, et. al.
Mon, 10 Apr 23
17/36

Comments: 13 pages, 10 figures

Direct Exoplanet Detection Using L1 Norm Low-Rank Approximation [IMA]

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http://arxiv.org/abs/2304.03619


We propose to use low-rank matrix approximation using the component-wise L1-norm for direct imaging of exoplanets. Exoplanet detection is a challenging task for three main reasons: (1) the host star is several orders of magnitude brighter than exoplanets, (2) the angular distance between exoplanets and star is usually very small, and (3) the speckles are very similar to the exoplanet signal both in shape and intensity. First, we empirically examine the statistical noise assumptions of the models, second, we evaluate the performance of the proposed L1 low-rank approximation (L1-LRA) algorithm based on visual comparisons and receiver operating characteristic (ROC) curves. We compare the results of the L1-LRA with the widely used truncated singular value decomposition (SVD) based on the L2 norm in two different annuli, one close to the star and one far away.

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H. Daglayan, S. Vary, V. Leplat, et. al.
Mon, 10 Apr 23
21/36

Comments: 5 pages, 3 figures

Machine learning-based seeing estimation and prediction using multi-layer meteorological data at Dome A, Antarctica [IMA]

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http://arxiv.org/abs/2304.03587


Atmospheric seeing is one of the most important parameters for evaluating and monitoring an astronomical site. Moreover, being able to predict the seeing in advance can guide observing decisions and significantly improve the efficiency of telescopes. However, it is not always easy to obtain long-term and continuous seeing measurements from a standard instrument such as differential image motion monitor (DIMM), especially for those unattended observatories with challenging environments such as Dome A, Antarctica. In this paper, we present a novel machine learning-based framework for estimating and predicting seeing at a height of 8 m at Dome A, Antarctica, using only the data from a multi-layer automated weather station (AWS). In comparison with DIMM data, our estimate has a root mean square error (RMSE) of 0.18 arcsec, and the RMSE of predictions 20 minutes in the future is 0.12 arcsec for the seeing range from 0 to 2.2 arcsec. Compared with the persistence, where the forecast is the same as the last data point, our framework reduces the RMSE by 37 percent. Our method predicts the seeing within a second of computing time, making it suitable for real-time telescope scheduling.

Read this paper on arXiv…

X. Hou, Y. Hu, F. Du, et. al.
Mon, 10 Apr 23
26/36

Comments: 13 pages, 14 figures, accepted for publication in Astronomy and Computing

Full Resolution Deconvolution of Complex Faraday Spectra [IMA]

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http://arxiv.org/abs/2304.02728


Polarized synchrotron emission from multiple Faraday depths can be separated by calculating the complex Fourier transform of the Stokes’ parameters as a function of the wavelength squared, known as Faraday Synthesis. As commonly implemented, the transform introduces an additional term $\lambda_0^2$, which broadens the real and imaginary spectra, but not the amplitude spectrum. We use idealized tests to investigate whether additional information can be recovered with a clean process restoring beam set to the narrower width of the peak in the real “full” resolution spectrum with $\lambda_0^2=0$. We find that the $\lambda_0^2$ choice makes no difference, except for the use of a smaller restoring beam. With this smaller beam, the accuracy and phase stability are unchanged for single Faraday components. However, using the smaller restoring beam for multiple Faraday components we find a) better discrimination of the components, b) significant reductions in blending of structures in tomography images, and c) reduction of spurious features in the Faraday spectra and tomography maps. We also discuss the limited accuracy of information on scales comparable to the width of the amplitude spectrum peak, and note a clean-bias, reducing the recovered amplitudes. We present examples using MeerKAT L-band data. We also revisit the maximum width in Faraday depth to which surveys are sensitive, and introduce the variable $W_{max}$, the width for which the power drops by a factor of 2. We find that most surveys cannot resolve continuous Faraday distributions unless the narrower full restoring beam is used.

Read this paper on arXiv…

L. Rudnick and W. Cotton
Fri, 7 Apr 23
9/50

Comments: 17 pages, 23 figures, accepted for publication in MNRAS, 4 April, 2023

The Colorado Ultraviolet Transit Experiment (CUTE) signal to noise calculator [IMA]

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http://arxiv.org/abs/2304.02776


We present here the signal-to-noise (S/N) calculator developed for the Colorado Ultraviolet Transit Experiment (CUTE) mission. CUTE is a 6U CubeSat operating in the near-ultraviolet (NUV) observing exoplanetary transits to study their upper atmospheres. CUTE was launched into a low-Earth orbit in September 2021 and it is currently gathering scientific data. As part of the S/N calculator, we also present the error propagation for computing transit depth uncertainties starting from the S/N of the original spectroscopic observations. The CUTE S/N calculator is currently extensively used for target selection and scheduling. The modular construction of the CUTE S/N calculator enables its adaptation and can be used also for other missions and instruments.

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A. Sreejith, L. Fossati, P. Cubillos, et. al.
Fri, 7 Apr 23
19/50

Comments: Accepted for publication in Astrophysics and Space Science

The Large Array Survey Telescope — Science Goals [IMA]

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http://arxiv.org/abs/2304.02719


The Large Array Survey Telescope (LAST) is designed to survey the variable and transient sky at high temporal cadence. The array is comprised of 48 F/2.2 telescopes of 27.9cm aperture, coupled to full-frame backside-illuminated cooled CMOS detectors with $3.76$$\mu$m pixels, resulting in a pixel scale of $1.25\mathrm{arcsec}$. A single telescope with a field of view of $7.4\mathrm{deg}^2$ reaches a $5\sigma$ limiting magnitude of $19.6$ in $20$s. LAST 48 telescopes are mounted on 12 independent mounts — a modular design which allows us to conduct optimized parallel surveys. Here we provide a detailed overview of the LAST survey strategy and its key scientific goals. These include the search for gravitational-wave (GW) electromagnetic counterparts with a system that can cover the uncertainty regions of the next-generation GW detectors in a single exposure, the study of planetary systems around white dwarfs, and the search for near-Earth objects. LAST is currently being commissioned, with full scientific operations expected in mid 2023. This paper is accompanied by two complementary publications in this issue, giving an overview of the system (Ofek et al. 2023a) and of the dedicated data reduction pipeline (Ofek et al. 2023b).

Read this paper on arXiv…

S. Ben-Ami, E. Ofek, D. Polishook, et. al.
Fri, 7 Apr 23
23/50

Comments: N/A

Improving pulsar-timing solutions through dynamic pulse fitting [IMA]

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http://arxiv.org/abs/2304.02793


Precision pulsar timing is integral to the detection of the nanohertz stochastic gravitational-wave background as well as understanding the physics of neutron stars. Conventional pulsar timing often uses fixed time and frequency-averaged templates to determine the pulse times of arrival, which can lead to reduced accuracy when the pulse profile evolves over time. We illustrate a dynamic timing method that fits each observing epoch using basis functions. By fitting each epoch separately, we allow for the evolution of the pulse shape epoch to epoch. We apply our method to PSR J1103$-$5403 and demonstrate that it undergoes mode changing, making it the fourth millisecond pulsar to exhibit such behaviour. Our method, which is able to identify and time a single mode, yields a timing solution with a root-mean-square error of 1.343 $\mu \mathrm{s}$, a factor of 1.78 improvement over template fitting on both modes. In addition, the white-noise amplitude is reduced 4.3 times, suggesting that fitting the full data set causes the mode changing to be incorrectly classified as white noise. This reduction in white noise boosts the signal-to-noise ratio of a gravitational-wave background signal for this particular pulsar by 32%. We discuss the possible applications for this method of timing to study pulsar magnetospheres and further improve the sensitivity of searches for nanohertz gravitational waves.

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R. Nathan, M. Miles, G. Ashton, et. al.
Fri, 7 Apr 23
48/50

Comments: 8 pages, 8 figures

Deep learning approach for identification of HII regions during reionization in 21-cm observations — II. foreground contamination [IMA]

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http://arxiv.org/abs/2304.02661


The upcoming Square Kilometre Array Observatory (SKAO) will produce images of neutral hydrogen distribution during the epoch of reionization by observing the corresponding 21-cm signal. However, the 21-cm signal will be subject to instrumental limitations such as noise, foreground contamination, and limited resolution, which pose a challenge for accurate detection. In this study, we present the \texttt{SegU-Net v2} framework, which is an enhanced version of our U-Net architecture-based convolutional neural network built for segmenting image data into meaningful features. This framework is designed to identify neutral and ionized regions in the 21-cm signal contaminated with foreground emission that is $\sim$3 order of magnitude larger. We demonstrate the effectiveness of our method by estimating the true ionization history from mock observations of SKA with an observation time of 1000 h, achieving an average classification accuracy of 71 per cent. As the photon sources driving reionization are expected to be located inside the ionised regions identified by \texttt{SegU-Net v2}, this tool can be used to identify locations for follow-up studies with infrared/optical telescopes to detect these sources. Additionally, we derive summary statistics, such as the size distribution of neutral islands, from evaluating the reliability of our method on the tomographic data expected from the SKA-Low. Our study suggests that \texttt{SegU-Net v2} can be a stable and reliable tool for analyzing the 3D tomographic data produced by the SKA and recovering important information about the non-Gaussian nature of the reionization process.

Read this paper on arXiv…

M. Bianco, S. Giri, D. Prelogović, et. al.
Fri, 7 Apr 23
49/50

Comments: 16 pages, 9 figures, 2 tables. Comments welcome

Simulation of CSSTs astrometric capability [IMA]

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http://arxiv.org/abs/2304.02196


The China Space Station Telescope (CSST) will enter a low Earth orbit around 2024 and operate for 10 years, with seven of those years devoted to surveying the area of the median-to-high Galactic latitude and median-to-high Ecliptic latitude of the sky. To maximize the scientific output of CSST, it is important to optimize the survey schedule. We aim to evaluate the astrometric capability of CSST for a given survey schedule and to provide independent suggestions for the optimization of the survey strategy. For this purpose, we first construct the astrometric model and then conduct simulated observations based on the given survey schedule. The astrometric solution is obtained by analyzing the simulated observation data. And then we evaluate the astrometric capability of CSST by analyzing the properties of the astrometric solution. We find that the accuracy of parallax and proper motion of CSST is better than 1 mas( yr1) for the sources of 18-22 mag in g band, and about 1-10 mas( yr1) for the sources of 22-26 mag in g band, respectively. The results from real survey could be worse since the assumptions are optimistic and simple. We find that optimizing the survey schedule can improve the astrometric accuracy of CSST. In the future, we will improve the astrometric capability of CSST by continuously iterating and optimizing the survey schedule.

Read this paper on arXiv…

Z. Fu, Z. Qi, S. Liao, et. al.
Thu, 6 Apr 23
26/76

Comments: 17 pages, 10 figures

Next-Level, Robotic Telescope-Based Observing Experiences to Boost STEM Enrollments and Majors on a National Scale: Year 1 Report [IMA]

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http://arxiv.org/abs/2304.02545


Funded by a $3M Department of Defense (DoD) National Defense Education Program (NDEP) award, we are developing and deploying on a national scale a follow-up curriculum to “Our Place In Space!”, or OPIS!, in which approx. 3,500 survey-level astronomy students are using our global network of “Skynet” robotic telescopes each year. The goal of this new curriculum, called “Astrophotography of the Multi-Wavelength Universe!”, or MWU!, is to boost the number of these students who choose STEM majors. During Y1, our participating educators have developed MWU!’s (now renumbered) 2nd and 4th modules, and are in the process of developing its 3rd and 7th modules (out of 7). Solid progress has also been made on the software front, (1) where we have developed new graphing/analysis/modeling interfaces in support of Modules 2 and 4, and in response to feedback from the participating educators; and (2) where we are in the process of developing and adding astrophotography capabilities to Afterglow Access (AgA), our student-level, web-based, image processing and analysis application, in support of Modules 1 – 3 and 5 – 7. On the hardware front, development of our first four signal-processing units proceeds on schedule; these are key to Skynet’s integration of a global network of radio telescopes, capable of exploring the invisible universe. Preparations have also been made on the evaluation and accessibility fronts, for when the first MWU! modules are deployed in Spring 2023.

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D. Reichart, J. Haislip, V. Kouprianov, et. al.
Thu, 6 Apr 23
29/76

Comments: 10 pages, 9 figures, ASP2022 Conference Proceedings, December 2022

Polarization aberrations in next-generation giant segmented mirror telescopes (GSMTs) I. Effect on the coronagraphic performance [IMA]

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http://arxiv.org/abs/2304.02079


Next-generation large segmented mirror telescopes are expected to perform direct imaging and characterization of Earth-like rocky planets, which requires contrast limits of $10^{-7}$ to $10^{-8}$ at wavelengths from I to J band. One critical aspect affecting the raw on-sky contrast are polarization aberrations arising from the reflection from the telescope’s mirror surfaces and instrument optics. We simulate the polarization aberrations and estimate their effect on the achievable contrast for three next-generation ground-based large segmented mirror telescopes. We performed ray-tracing in Zemax and computed the polarization aberrations and Jones pupil maps using the polarization ray-tracing algorithm. The impact of these aberrations on the contrast is estimated by propagating the Jones pupil maps through a set of idealized coronagraphs using hcipy, a physical optics-based simulation framework. The optical modeling of the giant segmented mirror telescopes (GSMTs) shows that polarization aberrations create significant leakage through a coronagraphic system. The dominant aberration is retardance defocus, which originates from the steep angles on the primary and secondary mirrors. The retardance defocus limits the contrast to $10^{-5}$ to $10^{-4}$ at 1 $\lambda/D$ at visible wavelengths, and $10^{-5}$ to $10^{-6}$ at infrared wavelengths. The simulations also show that the coating plays a major role in determining the strength of the aberrations. Polarization aberrations will need to be considered during the design of high-contrast imaging instruments for the next generation of extremely large telescopes. This can be achieved either through compensation optics, robust coronagraphs, specialized coatings, calibration, and data analysis approaches or by incorporating polarimetry with high-contrast imaging to measure these effects.

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R. Anche, J. Ashcraft, S. Haffert, et. al.
Thu, 6 Apr 23
36/76

Comments: 18 pages, 12 figures, Accepted in Astronomy & Astrophysics manuscript no. aa45651-22

The Enhanced Resolution Imager and Spectrograph for the VLT [IMA]

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http://arxiv.org/abs/2304.02343


ERIS, the Enhanced Resolution Imager and Spectrograph, is an instrument that both extends and enhances the fundamental diffraction limited imaging and spectroscopy capability for the VLT. It replaces two instruments that were being maintained beyond their operational lifetimes, combines their functionality on a single focus, provides a new wavefront sensing module for natural and laser guide stars that makes use of the Adaptive Optics Facility, and considerably improves on their performance. The observational modes ERIS provides are integral field spectroscopy at 1-2.5 {\mu}m, imaging at 1-5 {\mu}m with several options for high contrast imaging, and longslit spectroscopy at 3-4 {\mu}m, The instrument is installed at the Cassegrain focus of UT4 at the VLT and, following its commissioning during 2022, has been made available to the community.

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R. Davies, O. Absil, G. Agapito, et. al.
Thu, 6 Apr 23
49/76

Comments: 19 pages with 29 figures; submitted to A&A

Low-loss Si-based Dielectrics for High Frequency Components of Superconducting Detectors [IMA]

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http://arxiv.org/abs/2304.01362


Silicon-based dielectric is crucial for many superconducting devices, including high-frequency transmission lines, filters, and resonators. Defects and contaminants in the amorphous dielectric and at the interfaces between the dielectric and metal layers can cause microwave losses and degrade device performance. Optimization of the dielectric fabrication, device structure, and surface morphology can help mitigate this problem. We present the fabrication of silicon oxide and nitride thin film dielectrics. We then characterized them using Scanning Electron Microscopy, Atomic Force Microscopy, and spectrophotometry techniques. The samples were synthesized using various deposition methods, including Plasma-Enhanced Chemical Vapor Deposition and magnetron sputtering. The films morphology and structure were modified by adjusting the deposition pressure and gas flow. The resulting films were used in superconducting resonant systems consisting of planar inductors and capacitors. Measurements of the resonator properties, including their quality factor, were performed.

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M. Lisovenko, Z. Pan, P. Barry, et. al.
Wed, 5 Apr 23
17/62

Comments: 4 pages, 5 figures, conference

Fabrication of a Monolithic 5-Meter Aluminum Reflector for Millimeter-Wavelength Observations of the Cosmic Microwave Background [IMA]

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http://arxiv.org/abs/2304.01469


We have demonstrated the fabrication of a monolithic, 5-meter diameter, aluminum reflector with 17.4 $\mu$m RMS surface error. The reflector was designed to avoid the problem of pickup due to scattering from panel gaps in a large, millimeter-wavelength telescope that will be used for measurements on the cosmic microwave background.

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T. Natoli, B. Benson, J. Carlstrom, et. al.
Wed, 5 Apr 23
46/62

Comments: N/A

Astronomical image time series classification using CONVolutional attENTION (ConvEntion) [IMA]

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http://arxiv.org/abs/2304.01236


Aims. The treatment of astronomical image time series has won increasing attention in recent years. Indeed, numerous surveys following up on transient objects are in progress or under construction, such as the Vera Rubin Observatory Legacy Survey for Space and Time (LSST), which is poised to produce huge amounts of these time series. The associated scientific topics are extensive, ranging from the study of objects in our galaxy to the observation of the most distant supernovae for measuring the expansion of the universe. With such a large amount of data available, the need for robust automatic tools to detect and classify celestial objects is growing steadily. Methods. This study is based on the assumption that astronomical images contain more information than light curves. In this paper, we propose a novel approach based on deep learning for classifying different types of space objects directly using images. We named our approach ConvEntion, which stands for CONVolutional attENTION. It is based on convolutions and transformers, which are new approaches for the treatment of astronomical image time series. Our solution integrates spatio-temporal features and can be applied to various types of image datasets with any number of bands. Results. In this work, we solved various problems the datasets tend to suffer from and we present new results for classifications using astronomical image time series with an increase in accuracy of 13%, compared to state-of-the-art approaches that use image time series, and a 12% increase, compared to approaches that use light curves.

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A. Bairouk, M. Chaumont, D. Fouchez, et. al.
Wed, 5 Apr 23
49/62

Comments: N/A

JWST MIRI Imaging Data Post-Processing Preliminary Study with Fourier Transformation to uncover potentially celestial-origin signals [IMA]

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http://arxiv.org/abs/2304.00728


This manuscript reports a part of a dedicated study aiming to disentangle sources of signals from James Webb Space Telescope (JWST) Mid-Infrared Instrument (MIRI) imaging mode. An instrumental introduction and characteristics section is present regarding MIRI. Later, a Fast Fourier Transformation-based filtering approach and its results will be discussed.

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G. Hatipoğlu
Tue, 4 Apr 23
4/111

Comments: 16 pages, 18 figures

The Timing System of LIGO Discoveries [IMA]

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http://arxiv.org/abs/2304.01188


LIGO’s mission critical timing system has enabled gravitational wave and multi-messenger astrophysical discoveries as well as the rich science extracted. Achieving optimal detector sensitivity, detecting transient gravitational waves, and especially localizing gravitational wave sources, the underpinning of multi-messenger astrophysics, all require proper gravitational wave data time-stamping. Measurements of the relative arrival times of gravitational waves between different detectors allow for coherent gravitational wave detections, localization of gravitational wave sources, and the creation of skymaps. The carefully designed timing system achieves these goals by mitigating phase noise to avoid signal up-conversion and maximize gravitational wave detector sensitivity. The timing system also redundantly performs self-calibration and self-diagnostics in order to ensure reliable, extendable, and traceable time stamping. In this paper, we describe and quantify the performance of these core systems during the latest O3 scientific run of LIGO, Virgo, and KAGRA. We present results of the diagnostic checks done to verify the time-stamping for individual gravitational wave events observed during O3 as well as the timing system performance for all of O3 in LIGO Livingston and LIGO Hanford. We find that, after 3 observing runs, the LIGO timing system continues to reliably meet mission requirements of timing precision below 1 $\mu$s with a significant safety margin.

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A. Sullivan, Y. Asali, Z. Márka, et. al.
Tue, 4 Apr 23
28/111

Comments: 11 pages, 8 figures

Fabrication Development for SPT-SLIM, a Superconducting Spectrometer for Line Intensity Mapping [IMA]

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http://arxiv.org/abs/2304.00973


Line Intensity Mapping (LIM) is a new observational technique that uses low-resolution observations of line emission to efficiently trace the large-scale structure of the Universe out to high redshift. Common mm/sub-mm emission lines are accessible from ground-based observatories, and the requirements on the detectors for LIM at mm-wavelengths are well matched to the capabilities of large-format arrays of superconducting sensors. We describe the development of an R = 300 on-chip superconducting filter-bank spectrometer covering the 120–180 GHz band optimized for future mm-LIM experiments, focusing on SPT-SLIM, a pathfinder LIM instrument for the South Pole Telescope. Radiation is coupled from the telescope optical system to the spectrometer chip via an array of feedhorn-coupled orthomode transducers. Superconducting microstrip transmission lines then carry the signal to an array of channelizing half-wavelength resonators, and the output of each spectral channel is sensed by a lumped element kinetic inductance detector (leKID). Key areas of development include incorporating new low-loss dielectrics to improve both the achievable spectral resolution and optical efficiency and development of a robust fabrication process to create a galvanic connection between ultra-pure superconducting thin-films to realize multi-material (hybrid) leKIDs. We provide an overview of the spectrometer design, fabrication process, and prototype devices.

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T. Cecil, C. Albert, A. Anderson, et. al.
Tue, 4 Apr 23
44/111

Comments: 7 pages, 7 figures, presented at 2022 Applied Superconductivity Conference

Characterization of MKIDs for CMB observation at 220 GHz with the South Pole Telescope [IMA]

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http://arxiv.org/abs/2304.01158


We present an updated design of the 220 GHz microwave kinetic inductance detector (MKID) pixel for SPT-3G+, the next-generation camera for the South Pole Telescope. We show results of the dark testing of a 63-pixel array with mean inductor quality factor $Q_i = 4.8 \times 10^5$, aluminum inductor transition temperature $T_c = 1.19$ K, and kinetic inductance fraction $\alpha_k = 0.32$. We optically characterize both the microstrip-coupled and CPW-coupled resonators, and find both have a spectral response close to prediction with an optical efficiency of $\eta \sim 70\%$. However, we find slightly lower optical response on the lower edge of the band than predicted, with neighboring dark detectors showing more response in this region, though at level consistent with less than 5\% frequency shift relative to the optical detectors. The detectors show polarized response consistent with expectations, with a cross-polar response of $\sim 10\%$ for both detector orientations.

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K. Dibert, P. Barry, A. Anderson, et. al.
Tue, 4 Apr 23
50/111

Comments: 6 pages, 5 figures, ASC 2022 proceedings

Measurement of Dielectric Loss in Silicon Nitride at Centimeter and Millimeter Wavelengths [IMA]

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http://arxiv.org/abs/2304.01103


This work presents a suite of measurement techniques for characterizing the dielectric loss tangent across a wide frequency range from $\sim$1 GHz to 150 GHz using the same test chip. In the first method, we fit data from a microwave resonator at different temperatures to a model that captures the two-level system (TLS) response to extract and characterize both the real and imaginary components of the dielectric loss. The inverse of the internal quality factor is a second measure of the overall loss of the resonator, where TLS loss through the dielectric material is typically the dominant source. The third technique is a differential optical measurement at 150 GHz. The same antenna feeds two microstrip lines with different lengths that terminate in two microwave kinetic inductance detectors (MKIDs). The difference in the detector response is used to estimate the loss per unit length of the microstrip line. Our results suggest a larger loss for SiN$_x$ at 150 GHz of ${\mathrm{\tan \delta\sim 4\times10^{-3}}}$ compared to ${\mathrm{2.0\times10^{-3}}}$ and ${\mathrm{\gtrsim 1\times10^{-3}}}$ measured at $\sim$1 GHz using the other two methods. {These measurement techniques can be applied to other dielectrics by adjusting the microstrip lengths to provide enough optical efficiency contrast and other mm/sub-mm frequency ranges by tuning the antenna and feedhorn accordingly.

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Z. Pan, P. Barry, T. Cecil, et. al.
Tue, 4 Apr 23
62/111

Comments: N/A

Electromagnetic Properties of Aluminum-based Bilayers for Kinetic Inductance Detectors [IMA]

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http://arxiv.org/abs/2304.00431


The complex conductivity of a superconducting thin film is related to the quasiparticle density, which depends on the physical temperature and can also be modified by external pair breaking with photons and phonons. This relationship forms the underlying operating principle of Kinetic Inductance Detectors (KIDs), where the detection threshold is governed by the superconducting energy gap. We investigate the electromagnetic properties of thin-film aluminum that is proximitized with either a normal metal layer of copper or a superconducting layer with a lower $T_C$, such as iridium, in order to extend the operating range of KIDs. Using the Usadel equations along with the Nam expressions for complex conductivity, we calculate the density of states and the complex conductivity of the resulting bilayers to understand the dependence of the pair breaking threshold, surface impedance, and intrinsic quality factor of superconducting bilayers on the relative film thicknesses. The calculations and analyses provide theoretical insights in designing aluminum-based bilayer kinetic inductance detectors for detection of microwave photons and athermal phonons at the frequencies well below the pair breaking threshold of a pure aluminum film.

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G. Wang, P. Barry, T. Cecil, et. al.
Tue, 4 Apr 23
65/111

Comments: Submitted as a proceeding for Applied Superconductivity Conference 2022

Noise Optimization for MKIDs with Different Design Geometries and Material Selections [IMA]

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http://arxiv.org/abs/2304.01133


The separation and optimization of noise components is critical to microwave-kinetic inductance detector (MKID) development. We analyze the effect of several changes to the lumped-element inductor and interdigitated capacitor geometry on the noise performance of a series of MKIDs intended for millimeter-wavelength experiments. We extract the contributions from two-level system noise in the dielectric layer, the generation-recombination noise intrinsic to the superconducting thin-film, and system white noise from each detector noise power spectrum and characterize how these noise components depend on detector geometry, material, and measurement conditions such as driving power and temperature. We observe a reduction in the amplitude of two-level system noise with both an elevated sample temperature and an increased gap between the fingers within the interdigitated capacitors for both aluminum and niobium detectors. We also verify the expected reduction of the generation-recombination noise and associated quasiparticle lifetime with reduced inductor volume. This study also iterates over different materials, including aluminum, niobium, and aluminum manganese, and compares the results with an underlying physical model.

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Z. Pan, K. Dibert, J. Zhang, et. al.
Tue, 4 Apr 23
67/111

Comments: N/A

Quasiparticle Generation-Recombination Noise in the Limit of Low Detector Volume [IMA]

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http://arxiv.org/abs/2304.01156


We have measured the quasiparticle generation-recombination (GR) noise in aluminium lumped element kinetic inductors with a wide range of detector volumes at various temperatures. The basic detector consists of meandering inductor and interdigitated capacitor fingers. The inductor volume is varied from 2 to 153 {\mu}m^{3} by changing the inductor width and length to maintain a constant inductance. We started with measuring the power spectrum density (PSD) of the detectors frequency noise which is a function of GR noise and we clearly observed the spectrum roll off at 10 kHz which corresponds to the quasiparticle lifetime. Using data from a temperature sweep of the resonator frequency we convert the frequency fluctuation to quasiparticle fluctuation and observe its strong dependence on detector volume: detectors with smaller volume display less quasiparticle noise amplitude. Meanwhile we observe a saturated quasiparticle density at low temperature from all detectors as the quasiparticle life time {\tau}qp approaches a constant value at low temperature.

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J. Li, P. Barry, T. Cecil, et. al.
Tue, 4 Apr 23
73/111

Comments: N/A

TIRCAM2 Camera Interface on the Side port of the 3.6 meter Devasthal Optical Telescope [IMA]

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http://arxiv.org/abs/2304.00243


The TIFR Near Infrared Imaging Camera-II (TIRCAM2) is being used at the 3.6 m Devasthal Optical Telescope (DOT) operated by Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, Uttarakhand, India. Earlier, the TIRCAM2 was used at the main port of the DOT on time shared basis. It has now been installed at the side port of the telescope. Side port installation allows near simultaneous observations with the main port instrument as well as longer operating periods. Thus, the TIRCAM2 serves the astronomical community for a variety of observations ranging from lunar occultations, transient events and normal scheduled observations.

Read this paper on arXiv…

S. Bhagat, M. Naik, S. Poojary, et. al.
Tue, 4 Apr 23
81/111

Comments: Accepted for publication in the Journal of Astrophysics and Astronomy

Characteristic Modes Analysis of Mutually Coupled Log-Periodic Dipole Antennas [IMA]

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http://arxiv.org/abs/2304.00332


Characteristic Modes Analysis (CMA) is a widely used method with recent progress in multi-antenna systems. We employ this method to characterize the mutual coupling phenomenon between two SKALA4.1 antennas, the low-frequency array elements of the future radiotelescope Square Kilometer Array (SKA-Low). The CMA accuracy is first validated at the lowest frequency range of interest with respect to a standard Method of Moments (MoM) solution by decomposing the single antenna into its characteristic modes. We then examine critical frequencies of a two-antenna system in modal decomposition, and characterize those responsible for the radiated electric field spurious spectral features owing to the mutual coupling. We connect these modes to first-order coupling of single antenna CMA modes, by using the eigenvalue data of both single- and two- antenna simulations.

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G. Kyriakou, P. Bolli and G. Virone
Tue, 4 Apr 23
84/111

Comments: 4 pages, 5 figures, presented at the 17th European Conference on Antennas and Propagation

Predictive power of daily viscacha and vicuña sightings on Simons Array site work results [IMA]

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http://arxiv.org/abs/2304.00351


We studied the predictive power of daily animal sightings on site work outcomes at the Polarbear and Simons Array experiment site in the Atacama Desert, Chile. Specifically, we observed the number of viscacha and vicuna sightings during a two-month period, totaling 31 observation days, and analyzed their relationship with site work outcomes using machine learning techniques. Our results show that there was no significant correlation between the number of animal sightings and site work outcomes. The feather importance score for viscacha and vicuna were 0.71068 and 0.057762, respectively. Future research may include expanding the analysis to include other animal species, investigating the impact of human activity on site work outcomes, and exploring alternative machine learning models or statistical techniques.

Read this paper on arXiv…

P. Siritanasak, I. Birdwell, L. Lowry, et. al.
Tue, 4 Apr 23
93/111

Comments: N/A

An Astronomers Guide to Machine Learning [IMA]

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http://arxiv.org/abs/2304.00512


With the volume and availability of astronomical data growing rapidly, astronomers will soon rely on the use of machine learning algorithms in their daily work. This proceeding aims to give an overview of what machine learning is and delve into the many different types of learning algorithms and examine two astronomical use cases. Machine learning has opened a world of possibilities for us astronomers working with large amounts of data, however if not careful, users can trip into common pitfalls. Here we’ll focus on solving problems related to time-series light curve data and optical imaging data mainly from the Deeper, Wider, Faster Program (DWF). Alongside the written examples, online notebooks will be provided to demonstrate these different techniques. This guide aims to help you build a small toolkit of knowledge and tools to take back with you for use on your own future machine learning projects.

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S. Webb and S. Goode
Tue, 4 Apr 23
99/111

Comments: 12 pages, 5 Figures, International Astronomical Union Proceedings Series 368

ronswanson: Building Table Models for 3ML [IMA]

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http://arxiv.org/abs/2303.17609


ronswanson provides a simple-to-use framework for building so-called table or template models for astromodelsthe modeling package for multi-messenger astrophysical data-analysis framework, 3ML. With astromodels and 3ML one can build the interpolation table of a physical model result of an expensive computer simulation. This then enables efficient reevaluation of the model while, for example, fitting it to a dataset. While 3ML and astromodels provide factories for building table models, the construction of pipelines for models that must be run on high-performance computing (HPC) systems can be cumbersome. ronswanson removes this complexity with a simple, reproducible templating system. Users can easily prototype their pipeline on multi-core workstations and then switch to a multi-node HPC system. ronswanson automatically generates the required Python and SLURM scripts to scale the execution of 3ML with astromodel‘s table models on an HPC system.

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J. Burgess
Mon, 3 Apr 23
10/53

Comments: 3 pages. Accepted for publication in JOSS

Programmed but Arbitrary Control Minimization of Amplitude and phase for speckle Nulling (PACMAN) [IMA]

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http://arxiv.org/abs/2303.18231


We revive a cross-platform focal-plane wavefront sensing and control algorithm originally released in 1980 and show that it can provide significant contrast improvements over conventional control methods on coronagraphic instruments. Its simplicity makes it applicable to various coronagraph models and we demonstrate it on a classical Lyot coronagraph and a phase-apodized pupil Lyot coronagraph, both in simulation and in laboratory experiments. Surprisingly, it had been forgotten for decades, but we present its unbeatable advantages considering the increase in computational power in the last 40 years. We consider it a major game changer in the planning for future, space-based high-contrast imaging missions and recommend it be intensively revisited by all readers.

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I. Laginja and R. Pourcelot
Mon, 3 Apr 23
14/53

Comments: Intended for public access on 1 April 2023

Processing System for Coherent Dedispersion of Pulsar Radio Emission [IMA]

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http://arxiv.org/abs/2303.17280


The work describes a system for converting VLBI observation data using the algorithms of coherent dedispersion and compensation of two-bit signal sampling. Coherent dedispersion is important for processing pulsar observations to obtain the best temporal resolution, while correction for signal sampling makes it possible to get rid of a number of parasitic effects that interfere with the analysis of the diffraction pattern of pulsars. A pipeline has been established that uses the developed converter and the ASC Software Correlator, which will allow reprocessing all archived data of Radioastron pulsar observations and to conduct a search for giant pulses, which requires the best temporal resolution.

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G. A., L. F., A. S., et. al.
Fri, 31 Mar 23
4/70

Comments: 16 pages, 4 figures

As a matter of colon: I am NOT digging cheeky titles (no, but actually yes :>) [IMA]

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http://arxiv.org/abs/2303.17059


What’s in a name, a poet once asked. To which we present this work, where we investigate the importance of a paper title in ensuring its best outcome. We queried astronomy papers using NASA ADS and ranked 6000 of them in terms of cheekiness level. We investigate the correlation between citation counts and (i) the presence of a colon, and (ii) cheekiness ranking. We conclude that colon matters in the anatomy of a paper title. So does trying to be cheeky, but we find that too much cheekiness can lead to cringefests. Striking the right balance is therefore crucial. May we recommend aiming for a level 4 cheekiness on a scale of 1-5.

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J. Tan and T. Suk
Fri, 31 Mar 23
61/70

Comments: 4 pages, 4 figures, 1 meme. Submitted to Acta Prima Aprila

Multi-scale CLEAN in hard X-ray solar imaging [IMA]

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http://arxiv.org/abs/2303.16272


Multi-scale deconvolution is an ill-posed inverse problem in imaging, with applications ranging from microscopy, through medical imaging, to astronomical remote sensing. In the case of high-energy space telescopes, multi-scale deconvolution algorithms need to account for the peculiar property of native measurements, which are sparse samples of the Fourier transform of the incoming radiation. The present paper proposes a multi-scale version of CLEAN, which is the most popular iterative deconvolution method in Fourier space imaging. Using synthetic data generated according to a simulated but realistic source configuration, we show that this multi-scale version of CLEAN performs better than the original one in terms of accuracy, photometry, and regularization. Further, the application to a data set measured by the NASA Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) shows the ability of multi-scale CLEAN to reconstruct rather complex topographies, characteristic of a real flaring event.

Read this paper on arXiv…

A. Volpara, M. Piana and A. Massone
Thu, 30 Mar 23
31/66

Comments: N/A

Dealing with large gaps in asteroseismic time series [IMA]

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http://arxiv.org/abs/2303.15584


With long data sets available for asteroseismology from space missions, it is sometimes necessary to deal with time series that have large gaps. This is becoming particularly relevant for TESS, which is revisiting many fields on the sky every two years. Because solar-like oscillators have finite mode lifetimes, it has become tempting to close large gaps by shifting time stamps. Using actual data from the Kepler Mission, we show that this results in artificial structures in the power spectrum that compromise the measurements of mode frequencies and linewidths.

Read this paper on arXiv…

T. Bedding and H. Kjeldsen
Wed, 29 Mar 23
2/73

Comments: published in RNAAS

Bayesian Computation in Astronomy: Novel methods for parallel and gradient-free inference [IMA]

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http://arxiv.org/abs/2303.16134


The goal of this thesis is twofold; introduce the fundamentals of Bayesian inference and computation focusing on astronomical and cosmological applications, and present recent advances in probabilistic computational methods developed by the author that aim to facilitate Bayesian data analysis for the next generation of astronomical observations and theoretical models. The first part of this thesis familiarises the reader with the notion of probability and its relevance for science through the prism of Bayesian reasoning, by introducing the key constituents of the theory and discussing its best practices. The second part includes a pedagogical introduction to the principles of Bayesian computation motivated by the geometric characteristics of probability distributions and followed by a detailed exposition of various methods including Markov chain Monte Carlo (MCMC), Sequential Monte Carlo (SMC), and Nested Sampling (NS). Finally, the third part presents two novel computational methods (Ensemble Slice Sampling and Preconditioned Monte Carlo) and their respective software implementations (zeus and pocoMC). [abridged]

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M. Karamanis
Wed, 29 Mar 23
4/73

Comments: PhD Thesis, 280 pages

Machine Learning for Observational Cosmology [IMA]

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http://arxiv.org/abs/2303.15794


An array of large observational programs using ground-based and space-borne telescopes is planned in the next decade. The forthcoming wide-field sky surveys are expected to deliver a sheer volume of data exceeding an exabyte. Processing the large amount of multiplex astronomical data is technically challenging, and fully automated technologies based on machine learning and artificial intelligence are urgently needed. Maximizing scientific returns from the big data requires community-wide efforts. We summarize recent progress in machine learning applications in observational cosmology. We also address crucial issues in high-performance computing that are needed for the data processing and statistical analysis.

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K. Moriwaki, T. Nishimichi and N. Yoshida
Wed, 29 Mar 23
33/73

Comments: 55 pages, 8 figures, submitted to Reports on Progress in Physics

Sensitivity to point-like sources of the ALTO atmospheric particle detector array, designed for $\rm 200\,GeV$–$\rm 50\,TeV$ $γ$-ray astronomy [IMA]

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http://arxiv.org/abs/2303.15248


In the context of atmospheric shower arrays designed for $\gamma$-ray astronomy and in the context of the ALTO project, we present: a study of the impact of heavier nuclei in the cosmic-ray background on the estimated $\gamma$-ray detection performance on the basis of dedicated Monte Carlo simulations, a method to calculate the sensitivity to a point-like source, and finally the required observation times to reach a firm detection on a list of known point-like sources.

Read this paper on arXiv…

M. Punch, M. Senniappan, Y. Becherini, et. al.
Tue, 28 Mar 23
15/81

Comments: 16 pages, 7 figures, accepted for publication in JHEAP (Journal of High-Energy Astrophysics)

Detection Rate of <50-meter Interstellar Objects with LSST [IMA]

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http://arxiv.org/abs/2303.14766


The previous decade saw the discovery of the first four known interstellar objects due to advances in astronomical viewing equipment. Future sky surveys with greater sensitivity will allow for more frequent detections of such objects, including increasingly small objects. We consider the capabilities of the Legacy Survey of Space and Time (LSST) of the Vera C. Rubin Observatory to detect interstellar objects of small sizes during its period of operation over the next decade. We use LSST’s detection capabilities and simulate populations of interstellar objects in the range of 1-50m in diameter to calculate the expected number of small interstellar objects that will be detected. We use previous detections of interstellar objects to calibrate our object density estimates. We also consider the impact of the population’s albedo on detection rates by considering populations with two separate albedo distributions: a constant albedo of 0.06 and an albedo distribution that resembles near earth asteroids. We find that the number of detections increases with the diameter over the range of diameters we consider. We estimate a detection rate of up to a small ISO every two years of LSST’s operation with an increase by a factor of ten for future surveys that extend a magnitude deeper.

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C. Ezell and A. Loeb
Tue, 28 Mar 23
29/81

Comments: 17 pages, 7 figures

Scattering Parameter Measurements of the Long Wavelength Array Antenna and Front End Electronics [IMA]

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http://arxiv.org/abs/2303.14904


We present recent 2-port vector network analyzer (VNA) measurements of the complete set of scattering parameters for the antenna used within the Long Wavelength Array (LWA) and the associated front end electronics (FEEs). Full scattering parameter measurements of the antenna yield not only the reflection coefficient for each polarization, S11 and S22, but also the coupling between polarizations, S12 and S21. These had been previously modeled using simulations, but direct measurements had not been obtained until now. The measurements are used to derive a frequency dependent impedance mismatch factor (IMF) which represents the fraction of power that is passed through the antenna-FEE interface and not reflected due to a mismatch between the impedance of the antenna and the impedance of the FEE. We also present results from a two antenna experiment where each antenna is hooked up to a separate port on the VNA. This allows for cross-antenna coupling to be measured for all four possible polarization combinations. Finally, we apply the newly measured IMF and FEE forward gain corrections to LWA data to investigate how well they remove instrumental effects.

Read this paper on arXiv…

C. DiLullo, W. Reeve, B. Hicks, et. al.
Tue, 28 Mar 23
40/81

Comments: 16 pages, 12 figures, Accepted for publication in Publications of the Astronomical Society of the Pacific

Automated Speckle Interferometry of Known Binaries [IMA]

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http://arxiv.org/abs/2303.15011


Astronomers have been measuring the separations and position angles between the two components of binary stars since William Herschel began his observations in 1781. In 1970, Anton Labeyrie pioneered a method, speckle interferometry, that overcomes the usual resolution limits induced by atmospheric turbulence by taking hundreds or thousands of short exposures and reducing them in Fourier space. Our 2022 automation of speckle interferometry allowed us to use a fully robotic 1.0-meter PlaneWave Instruments telescope, located at the El Sauce Observatory in the Atacama Desert of Chile, to obtain observations of many known binaries with established orbits. The long-term objective of these observations is to establish the precision, accuracy, and limitations of this telescope’s automated speckle interferometry measurements. This paper provides an early overview of the Known Binaries Project and provide example results on a small-separation (0.27″) binary, WDS 12274-2843 B 228.

Read this paper on arXiv…

N. Hardy, L. Bewersdorff, D. Rowe, et. al.
Tue, 28 Mar 23
45/81

Comments: N/A

Pulsar and Magnetar Navigation with Fermi/GBM and GECAM [IMA]

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http://arxiv.org/abs/2303.14490


The determination of the absolute and relative position of a spacecraft is critical for its operation, observations, data analysis, scientific studies, as well as deep space exploration in general. A spacecraft that can determine its own absolute position autonomously may perform more than that must rely on transmission solutions. In this work, we report an absolute navigation accuracy of $\sim$ 20 km using 16-day Crab pulsar data observed with $Fermi$ Gamma ray Burst Monitor (GBM). In addition, we propose a new method with the inverse process of the triangulation for joint navigation using repeated bursts like that from the magnetar SGR J1935+2154 observed by the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) and GBM.

Read this paper on arXiv…

X. Luo, S. Xiao, S. Zheng, et. al.
Tue, 28 Mar 23
54/81

Comments: accepted for publication in ApJS

Looking for Stable Celestial Systems Using Bayesian Optimisation [IMA]

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http://arxiv.org/abs/2303.14835


This paper presents a study of the use of numerical simulation and Bayesian optimisation techniques to investigate the dynamics of celestial systems. Initially, the study focuses on Lagrange points in restricted three-body systems where a 2D three-body system simulator is employed to locate the five Lagrange points. An appropriate loss function is developed to capture the gravitational stability of the system, and the stability properties of the different Lagrange points are explored. Additionally, the study investigates how varying the number of variables for the satellite impacts the search for the Lagrange points. Finally, the scope of the study is expanded to explore stable configurations in multi-star systems represented by regular convex n-gons. In this case, Bayesian optimisation is used to find suitable settings for the n-gon’s radius and the stars’ velocity vectors, such that the overall system is stable.

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E. Fladmark, T. Reu and L. Justesen
Tue, 28 Mar 23
61/81

Comments: 10 pages

Implicit electric field Conjugation: Data-driven focal plane control [IMA]

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http://arxiv.org/abs/2303.13719


Direct imaging of Earth-like planets is one of the main science cases for the next generation of extremely large telescopes. This is very challenging due to the star-planet contrast that must be overcome. Most current high-contrast imaging instruments are limited in sensitivity at small angular separations due to non-common path aberrations (NCPA). The NCPA leak through the coronagraph and create bright speckles that limit the on-sky contrast and therefore also the post-processed contrast. We aim to remove the NCPA by active focal plane wavefront control using a data-driven approach. We developed a new approach to dark hole creation and maintenance that does not require an instrument model. This new approach is called implicit Electric Field Conjugation (iEFC) and it can be empirically calibrated. This makes it robust for complex instruments where optical models might be difficult to realize. Numerical simulations have been used to explore the performance of iEFC for different coronagraphs. The method was validated on the internal source of the Magellan Adaptive Optics eXtreme (MagAO-X) instrument to demonstrate iEFC’s performance on a real instrument. Numerical experiments demonstrate that iEFC can achieve deep contrast below $10^{-9}$ with several coronagraphs. The method is easily extended to broadband measurements and the simulations show that a bandwidth up to 40% can be handled without problems. Experiments with MagAO-X showed a contrast gain of a factor 10 in a broadband light and a factor 20 to 200 in narrowband light. A contrast of $5\cdot10^{-8}$ was achieved with the Phase Apodized Pupil Lyot Coronagraph at 7.5 $\lambda/D$. The new iEFC method has been demonstrated to work in numerical and lab experiments. It is a method that can be empirically calibrated and it can achieve deep contrast. This makes it a valuable approach for complex ground-based high-contrast imaging systems.

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S. Haffert, J. Males, K. Ahn, et. al.
Mon, 27 Mar 23
13/59

Comments: 13 pages, 12 figures accepted by A&A

Photometric Catalogue for Space and Ground Night-Time Remote-Sensing Calibration: RGB Synthetic Photometry from Gaia DR3 Spectrophotometry [IMA]

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http://arxiv.org/abs/2303.14147


Recent works have made strong efforts to produce standardised photometry in RGB bands. For this purpose, we carefully defined the transmissivity curves of RGB bands and defined a set of standard sources using the photometric information present in Gaia EDR3. This work aims not only to significantly increase the number and accuracy of RGB standards but also to provide, for the first time, reliable uncertainty estimates using the BP and RP spectrophotometry published in Gaia DR3 instead of their integrated photometry to predict RGB photometry. Furthermore, this method allows including calibrated sources regardless of how they are affected by extinction, which was a major shortcoming of previous work. The RGB photometry is synthesised from the Gaia BP and RP low-resolution spectra by directly using their set of coefficients multiplied with some basis functions provided in the Gaia catalogue for all sources published in Gaia DR3. The output synthetic magnitudes are compared with the previous catalogue of RGB standards available.

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J. Carrasco, N. Cardiel, E. Masana, et. al.
Mon, 27 Mar 23
55/59

Comments: 23 pages, 15 figures

Seeing-limited Coupling of Starlight into Single-mode Fiber with a Small Telescope [IMA]

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http://arxiv.org/abs/2303.12972


An optical fiber link to a telescope provides many advantages for spectrometers designed to detect and characterize extrasolar planets through precise radial velocity (PRV) measurements. In the seeing-limited regime, a multi-mode fiber is typically used so that a significant amount of starlight may be captured. In the near-diffraction-limited case, either with an adaptive optics system or with a small telescope at an excellent site, efficiently coupling starlight into a much smaller, single-mode fiber may be possible. In general, a spectrometer designed for single-mode fiber input will be substantially less costly than one designed for multi-mode fiber input. We describe the results of tests coupling starlight from a 70 cm telescope at Mt. Hopkins, Arizona into the single-mode fiber of the MINERVA-Red spectrometer at a wavelength of ~850 nm using a low-speed tip/tilt image stabilization system comprising all commercial, off-the-shelf components. We find that approximately 0.5% of the available starlight is coupled into the single-mode fiber under seeing conditions typical for observatories hosting small telescopes, which is close to the theoretical expectation. We discuss scientific opportunities for small telescopes paired with inexpensive, high-resolution spectrometers, as well as upgrade paths that should significantly increase the coupling efficiency for the MINERVA-Red system.

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D. Sliski, C. Blake, J. Eastman, et. al.
Fri, 24 Mar 23
1/56

Comments: 8 pages, 4 figures. Accepted for publication in Astronomische Nachrichten

Stochastic Recurrent Neural Networks for Modelling Astronomical Time Series: Advantages and Limitations [IMA]

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http://arxiv.org/abs/2303.13197


This paper reviews the Stochastic Recurrent Neural Network (SRNN) as applied to the light curves of Active Galactic Nuclei by Sheng et al. (2022). Astronomical data have inherent limitations arising from telescope capabilities, cadence strategies, inevitable observing weather conditions, and current understanding of celestial objects. When applying machine learning methods, it is vital to understand the effects of data limitations on our analysis and ability to make inferences. We take Sheng et al. (2022) as a case study, and illustrate the problems and limitations encountered in implementing the SRNN for simulating AGN variability as seen by the Rubin Observatory.

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X. Sheng, M. Nicholl and N. Ross
Fri, 24 Mar 23
19/56

Comments: To appear in proceedings of EAS 2022 S11 session on machine learning in astronomy

Temporal Intensity Interferometry at a 0.5 m Telescope [IMA]

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http://arxiv.org/abs/2303.13265


Intensity interferometry correlates light intensities rather than amplitudes of individual telescopes to recover the source geometry. While intensity correlations can alleviate the technical challenges of amplitude interferometry, and thus enable the realization of larger baselines and therefore higher resolution in astronomical imaging, this comes at the cost of greatly reduced sensitivity. We report the observation of photon bunching in the light of $\alpha$ Lyrae (Vega), measured with a telescope of merely 0.5m in diameter (Planewave CDK 20). The entire measurement setup, including collimation, optical filtering, and detection, was attached directly to the telescope without the use of optical fibers, facilitated by the large area of our single photon detectors. After a total exposure time of 32.4h over the course of six nights, a correlation signal with a contrast of $(9.5 \pm 2.7) \cdot 10^{-3}$ and a coherence time $0.34 \pm 0.12$ps was recovered, fitting well to preceding laboratory tests as well as expectations calculated from the optical and electronic characteristics of our measurement setup.

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S. Karl, S. Richter and J. Zanthier
Fri, 24 Mar 23
33/56

Comments: N/A

Space Astronomy at TIFR: From Balloons to Satellites [IMA]

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http://arxiv.org/abs/2303.13042


Tata Institute of Fundamental Research (TIFR) has a very long tradition of conducting space astronomy experiments. Within a few years of the discovery of the first non-solar X-ray source in 1962, TIFR leveraged its expertise in balloon technology to make significant contributions to balloon-borne hard X-ray astronomy. This initial enthusiasm led to extremely divergent all-round efforts in space astronomy: balloon-borne X-ray and infrared experiments, rocket and satellite-based X-ray experiments and a host of other new initiatives. In the early eighties, however, TIFR could not keep up with the torrent of results coming from the highly sophisticated satellite experiments from around the world but kept the flag flying by continuing research in a few low-key experiments. These efforts culminated in the landmark project, AstroSat, the first multi-wavelength observatory from India, with TIFR playing a pivotal role in it. In this article, I will present a highly personalised and anecdotal sketch of these exciting developments.

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A. Rao
Fri, 24 Mar 23
34/56

Comments: Based on a talk given during the conference `Landmarks@75′, organised by TIFR Alumni Association. Talks about making of AstroSat and could be of interest for a wider audience

JWST MIRI flight performance: The Medium-Resolution Spectrometer [IMA]

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http://arxiv.org/abs/2303.13469


The Medium-Resolution Spectrometer (MRS) provides one of the four operating modes of the Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST). The MRS is an integral field spectrometer, measuring the spatial and spectral distributions of light across the 5-28 $\mu m$ wavelength range with a spectral resolving power between 3700-1300. We present the MRS’ optical, spectral, and spectro-photometric performance, as achieved in flight, and report on the effects that limit the instrument’s ultimate sensitivity. The MRS flight performance has been quantified using observations of stars, planetary nebulae, and planets in our Solar System. The precision and accuracy of this calibration is checked against celestial calibrators with well known flux levels and spectral features. We find that the MRS geometric calibration has a distortion solution accuracy relative to the commanded position of 8 mas at 5 $\mu m$ and 23 mas at 28 $\mu m$. The wavelength calibration is accurate to within 9 km/sec at 5 $\mu m$ and 27 km/sec at 28 $\mu m$. The uncertainty in the absolute spectro-photometric calibration accuracy is estimated at 5.6 +- 0.7 %. The MIRI calibration pipeline is able to suppress the amplitude of spectral fringes to below 1.5 % for both extended and point sources across the entire wavelength range. The MRS PSF is 60 % broader than the diffraction limit along its long axis at 5 $\mu m$ and is 15 % broader at 28 $\mu m$. The MRS flight performance is found to be better than pre-launch expectations. The MRS is one of the most subscribed observing modes of JWST and is yielding many high-profile publications. It is currently humanity’s most powerful instrument for measuring the mid-infrared spectra of celestial sources and is expected to continue as such for many years to come.

Read this paper on arXiv…

I. Argyriou, A. Glasse, D. Law, et. al.
Fri, 24 Mar 23
38/56

Comments: 15 pages, 21 figures

The Brighter-Fatter Effect in the JWST MIRI Si:As IBC detectors I. Observations, impact on science, and modelling [IMA]

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http://arxiv.org/abs/2303.13517


The Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST) uses three Si:As impurity band conduction (IBC) detector arrays. The output voltage level of each MIRI detector pixel is digitally recorded by sampling-up-the-ramp. For uniform or low-contrast illumination, the pixel ramps become non-linear in a predictable way, but in areas of high contrast, the non-linearity curve becomes much more complex. We provide observational evidence of the Brighter-Fatter Effect (BFE) in MIRI conventional and high-contrast coronographic imaging, low-resolution spectroscopy, and medium-resolution spectroscopy data and investigate the physical mechanism that gives rise to the effect on the detector pixel raw voltage integration ramps. We use public data from the JWST/MIRI commissioning and Cycle 1 phase. We also develop a numerical electrostatic model of the MIRI detectors using a modified version of the public Poisson_CCD code. The physical mechanism behind the MIRI BFE is fundamentally different to that of CCDs and Hawaii-2RG (H2RG) detectors. This is due to the largest majority of the MIRI photo-excited electric charges not being stored at the pixels but at the input to the MIRI detector unit cell buffer amplifier capacitance. The resulting detector voltage debiasing alters the electrostatic potential inside the infrared-active layer and causes new photo-excited electrons, generated at a bright pixel, to be guided to the neighboring fainter pixels. Observationally, the debiasing-induced BFE makes the JWST MIRI data yield 10-25 % larger and 0.5-8 % brighter point sources and spectral line profiles as a function of the output level covered by the detector pixels. We find that the profile of the shrinking detector depletion region has implications for developing a pixel ramp non-linearity model for point sources observed with MIRI.

Read this paper on arXiv…

I. Argyriou, C. Lage, G. Rieke, et. al.
Fri, 24 Mar 23
45/56

Comments: 14 pages, 11 figures

Recommending Low-Cost Compact Space Environment and Space Weather Effects Sensor Suites for NASA Missions [IMA]

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http://arxiv.org/abs/2303.11875


As miniaturized spacecraft (e.g., cubesats and smallsats) and instrumentation become an increasingly indispensable part of space exploration and scientific investigations, it is important to understand their potential susceptibility to space weather impacts resulting from the sometimes volatile space environment. There are multitude of complexities involved in how space environment interacts with different space hardware/electronics. Measurements of such impacts, however, have been lacking. Therefore, we recommend developing and/or procuring low-cost, low-power consumption, and compact sensor suites (mainly for space weather and impact purposes) and flying them on all future NASA (and U.S in general) missions in order to measure and quantify space weather impacts, in addition to the main instrumentation.

Read this paper on arXiv…

Y. Zheng, M. Xapsos, I. Jun, et. al.
Wed, 22 Mar 23
1/68

Comments: White paper submitted to Decadal Survey for Solar and Space Physics (Heliophysics) 2024-2033 It can also be accessed here. this http URL

Asymmetric distribution of data products from WALLABY, an SKA precursor neutral hydrogen survey [IMA]

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http://arxiv.org/abs/2303.11670


The Widefield ASKAP L-band Legacy All-sky Blind surveY (WALLABY) is a neutral hydrogen survey (HI) that is running on the Australian SKA Pathfinder (ASKAP), a precursor telescope for the Square Kilometre Array (SKA). The goal of WALLABY is to use ASKAP’s powerful wide-field phased array feed technology to observe three quarters of the entire sky at the 21 cm neutral hydrogen line with an angular resolution of 30 arcseconds. Post-processing activities at the Australian SKA Regional Centre (AusSRC), Canadian Initiative for Radio Astronomy Data Analysis (CIRADA) and Spanish SKA Regional Centre prototype (SPSRC) will then produce publicly available advanced data products in the form of source catalogues, kinematic models and image cutouts, respectively. These advanced data products will be generated locally at each site and distributed across the network. Over the course of the full survey we expect to replicate data up to 10 MB per source detection, which could imply an ingestion of tens of GB to be consolidated in the other locations near real time. Here, we explore the use of an asymmetric database replication model and strategy, using PostgreSQL as the engine and Bucardo as the asynchronous replication service to enable robust multi-source pools operations with data products from WALLABY. This work would serve to evaluate this type of data distribution solution across globally distributed sites. Furthermore, a set of benchmarks have been developed to confirm that the deployed model is sufficient for future scalability and remote collaboration needs.

Read this paper on arXiv…

M. Parra-Royon, A. Shen, T. Reynolds, et. al.
Wed, 22 Mar 23
45/68

Comments: N/A

Dynamic and polarimetric VLBI imaging with a multiscalar approach [IMA]

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http://arxiv.org/abs/2303.11877


Recently multiscale imaging approaches such as DoG-HiT were developed to solve the VLBI imaging problem and showed a promising performance: they are fast, accurate, unbiased and automatic. We extend the multiscalar imaging approach to polarimetric imaging, reconstructions of dynamically evolving sources and finally to dynamic polarimetric reconstructions. These extensions (mr-support imaging) utilize a multiscalar approach. The time-averaged Stokes I image is decomposed by a wavelet transform into single subbands. We use the set of statistically significant wavelet coefficients, the multiresolution support, computed by DoG-HiT as a prior in a constrained minimization manner: we fit the single-frame (polarimetric) observables by only varying the coefficients in the multiresolution support. The EHT is a VLBI array imaging supermassive black holes. We demonstrate on synthetic data that mr-support imaging offers ample regularization and is able to recover simple geometric dynamics at the horizon scale in a typical EHT setup. The approach is relatively lightweight, fast and largely automatic and data driven. The ngEHT is a planned extension of the EHT designed to recover movies at the event horizon scales of a supermassive black hole. We benchmark the performance of mr-support imaging for the denser ngEHT configuration demonstrating the major improvements the additional ngEHT antennas will bring to dynamic, polarimetric reconstructions. Current and upcoming instruments offer the observational possibility to do polarimetric imaging of dynamically evolving structural patterns with highest spatial and temporal resolution. State-of-the-art dynamic reconstruction methods can capture this motion with a range of temporal regularizers and priors. With this work, we add an additional, simpler regularizer to the list: constraining the reconstruction to the multiresolution support.

Read this paper on arXiv…

H. Müller and A. Lobanov
Wed, 22 Mar 23
49/68

Comments: accepted for publication in A&A

MWAX: A New Correlator for the Murchison Widefield Array [IMA]

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http://arxiv.org/abs/2303.11557


We describe the design, validation, and commissioning of a new correlator termed “MWAX” for the Murchison Widefield Array (MWA) low-frequency radio telescope. MWAX replaces an earlier generation MWA correlator, extending correlation capabilities and providing greater flexibility, scalability, and maintainability. MWAX is designed to exploit current and future Phase II/III upgrades to MWA infrastructure, most notably the simultaneous correlation of all 256 of the MWA’s antenna tiles (and potentially more in future). MWAX is a fully software-programmable correlator based around an ethernet multicast architecture. At its core is a cluster of 24 high-performance GPU-enabled commercial-off-the-shelf compute servers that together process in real-time up to 24 coarse channels of 1.28 MHz bandwidth each. The system is highly flexible and scalable in terms of the number of antenna tiles and number of coarse channels to be correlated, and it offers a wide range of frequency / time resolution combinations to users. We conclude with a roadmap of future enhancements and extensions that we anticipate will be progressively rolled out over time.

Read this paper on arXiv…

I. Morrison, B. Crosse, G. Sleap, et. al.
Wed, 22 Mar 23
58/68

Comments: Accepted for publication in PASA. 22 pages, 14 figures, 2 tables

Optical characteristics and capabilities of the successive versions of Meudon spectroheliograph (1908-2023) [IMA]

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http://arxiv.org/abs/2303.10952


The spectroheliograph is a spectroscopic instrument designed to produce monochromatic images of the photosphere (the visible layer) and the chromosphere of the Sun. It was invented at the same time (1892), but independently, by Hale in the USA and Deslandres in France and was dedicated to long-term surveys of the solar cycles. For that purpose, systematic observations of the CaII K and H$\alpha$ lines started in Meudon observatory in 1908 and continue today, so that a huge collection of more than 100000 spectroheliograms, spanning 115 years of solar activity, was recorded. We present in this paper the optical characteristics and the capabilities of the successive versions of the instrument, from 1908 to now.

Read this paper on arXiv…

J. Malherbe
Tue, 21 Mar 23
3/68

Comments: N/A

Accounting for systematic uncertainties in the Imaging X-ray Polarimetry Explorer (IXPE) detector response [IMA]

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http://arxiv.org/abs/2303.10184


Launched on December 9, 2021, the Imaging X-ray Polarimetry Explorer (IXPE) is the first imaging polarimeter ever flown, providing sensitivity in the 2–8 keV range, and during the 2-year initial phase of the mission will sample tens of X-ray sources among different source classes. While most of the measurements will be statistics-limited, for some of the brightest objects observed and long integration times, the systematic uncertainties in the detector response (primarily the effective area, the modulation factor and the absolute energy scale) will be important. In this contribution, we describe a framework to propagate on high-level observables (e.g.: spectro-polarimetric fit parameters) the systematic uncertainties connected with the response of the detector, that we estimate from relevant ground calibrations and from observations of celestial point sources.

Read this paper on arXiv…

S. Silvestri
Tue, 21 Mar 23
5/68

Comments: 2 pages, 8 figures

Broadband plasma spray anti-reflection coating technology for millimeter-wave astrophysics [IMA]

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http://arxiv.org/abs/2303.10273


We present a broadband plasma spray anti-reflection (AR) coating technology for millimeter-wave astrophysics experiments with large-format, cryogenic optics. By plasma spraying alumina- and silica-based powders, we have produced coatings of tunable index of refraction and thickness, low loss, and coefficient of thermal expansion matched to alumina substrates. We demonstrate two-layer AR coatings on alumina with reflection below 5% over 82% and 69% fractional bandwidths for 90/150 and 220/280 GHz passband designs, respectively, and band-averaged absorption loss reduced to $\sim$1\% at 100 K for both AR coatings. We describe the design, tolerance, fabrication process, and optical measurements of these AR coatings.

Read this paper on arXiv…

O. Jeong, R. Plambeck, C. Raum, et. al.
Tue, 21 Mar 23
10/68

Comments: N/A

A reduction procedure and pipeline for the detection of trans-Neptunian objects using occultations [IMA]

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http://arxiv.org/abs/2303.11275


Trans-Neptunian objects smaller than a few kilometers are difficult to observe directly. They can be detected when they randomly occult a background star. Close to the ecliptic plane, each star is occulted once every tens of thousands of hours, and occultations typically last for less than a second. We present an algorithm, and companion pipeline, for detection of diffractive occultation events. Our approach includes: cleaning the data; an efficient and optimal matched filtering of the light-curves with a template bank of diffractive occultations; treating the red-noise in the light-curves; injection of simulated events for efficiency estimation; and applying data quality cuts. We discuss human vetting of the candidate events in a blinded way to reduce bias caused by the human-in-the-loop. We present Markov Chain Monte Carlo tools to estimate the parameters of candidate occultations, and test them on simulated events. This pipeline is used by the Weizmann Fast Astronomical Survey Telescope (W-FAST).

Read this paper on arXiv…

G. Nir, E. Ofek and B. Zackay
Tue, 21 Mar 23
41/68

Comments: N/A

An in-depth exploration of LAMOST Unknown spectra based on density clustering [IMA]

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http://arxiv.org/abs/2303.09836


LAMOST (Large Sky Area Multi-Object Fiber Spectroscopic Telescope) has completed the observation of nearly 20 million celestial objects, including a class of spectra labeled Unknown'. Besides low signal-to-noise ratio, these spectra often show some anomalous features that do not work well with current templates. In this paper, a total of 638,000Unknown’ spectra from LAMOST DR5 are selected, and an unsupervised-based analytical framework of `Unknown’ spectra named SA-Frame (Spectra Analysis-Frame) is provided to explore their origins from different perspectives. The SA-Frame is composed of three parts: NAPC-Spec clustering, characterization and origin analysis. First, NAPC-Spec(Nonparametric density clustering algorithm for spectra) characterizes different features in the “unknown” spectrum by adjusting the influence space and divergence distance to minimize the effects of noise and high dimensionality, resulting in 13 types. Second, characteristic extraction and representation of clustering results are carried out based on spectral lines and continuum, where these 13 types are characterized as regular spectra with low S/Ns, splicing problems, suspected galactic emission signals, contamination from city light and un-gregarious type respectively. Third, a preliminary analysis of their origins is made from the characteristics of the observational targets, contamination from the sky, and the working status of the instruments. These results would be valuable for improving the overall data quality of large-scale spectral surveys.

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H. Yang, X. Yin, J. Cai, et. al.
Mon, 20 Mar 23
18/51

Comments: 18 pages, 15 figures

Efficient channelization on a Graphics Processing Unit [IMA]

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http://arxiv.org/abs/2303.09886


We present an implementation of a channelizer (F-engine) running on a Graphics Processing Unit (GPU). While not the first GPU implementation of a channelizer, we have put significant effort into optimizing the implementation. We are able to process four antennas each with 2 Gsample/s, 10-bit dual-polarized input and 8-bit output, on a single commodity GPU. This fully utilizes the available PCIe bandwidth of the GPU. The system is not as optimized for a single high-bandwidth antenna, but handles 6.2 Gsample/s, limited by single-core CPU performance.

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B. Merry
Mon, 20 Mar 23
23/51

Comments: Submitted to The Journal of Astronomical Telescopes, Instruments, and Systems

XMM2ATHENA, the H2020 project to improve XMM-Newton analysis software and prepare for Athena [IMA]

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http://arxiv.org/abs/2303.10097


XMM-Newton, a European Space Agency observatory, has been observing the X-ray, ultra-violet and optical sky for 23 years. During this time, astronomy has evolved from mainly studying single sources to populations and from a single wavelength, to multi-wavelength or messenger data. We are also moving into an era of time domain astronomy. New software and methods are required to accompany evolving astronomy and prepare for the next generation X-ray observatory, Athena. Here we present XMM2ATHENA, a programme funded by the European Union’s Horizon 2020 research and innovation programme. XMM2ATHENA builds on foundations laid by the XMM-Newton Survey Science Centre (XMM-SSC), including key members of this consortium and the Athena Science ground segment, along with members of the X-ray community. The project is developing and testing new methods and software to allow the community to follow the X-ray transient sky in quasi-real time, identify multi-wavelength or messenger counterparts of XMM-Newton sources and determine their nature using machine learning. We detail here the first milestone delivery of the project, a new online, sensitivity estimator. We also outline other products, including the forthcoming innovative stacking procedure and detection algorithms to detect the faintest sources. These tools will then be adapted for Athena and the newly detected or identified sources will enhance preparation for observing the Athena X-ray sky.

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N. Webb, F. Carrera, A. Schwope, et. al.
Mon, 20 Mar 23
24/51

Comments: 7 pages, 1 figure, accepted for publication in Astronomische Nachrichten

Generalized optimal statistic for characterizing multiple correlated signals in pulsar timing arrays [IMA]

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http://arxiv.org/abs/2303.09615


The optimal statistic (OS) is a frequentist estimator for the amplitude and significance of a spatially-correlated signal in pulsar timing array (PTA) data, and it is widely used to search for the gravitational wave background (GWB). However, the OS cannot perfectly distinguish between different spatial correlations. In this paper, we introduce the multiple component optimal statistic (MCOS): a generalization of the OS that allows for multiple correlations to be simultaneously fit to the data. We use simulated data to show that this method more accurately recovers injected spatially correlated signals, and in particular reduces the risk of a false detection of a signal with the wrong spatial correlation. We also demonstrate that this method can be used to recover multiple correlated signals.

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S. Sardesai and S. Vigeland
Mon, 20 Mar 23
44/51

Comments: 11 pages, 9 figures, 4 tables