Implications of binary black hole detections on the merger rates of double neutron stars and neutron star-black holes [IMA]

We show that the inferred merger rate and chirp masses of binary black holes (BBHs) detected by advanced LIGO (aLIGO) can be used to constrain the rate of double neutron star (DNS) and neutron star – black hole (NSBH) mergers in the universe. We explicitly demonstrate this by considering a set of publicly available population synthesis models of \citet{Dominik:2012kk} and show that if all the BBH mergers, GW150914, LVT151012, GW151226, and GW170104, observed by aLIGO arise from isolated binary evolution, the predicted DNS merger rate may be constrained to be $0.6-295$ Gpc$^{-3}$yr$^{-1}$ and that of NSBH mergers will be constrained to $0.3-88$ Gpc$^{-3}$yr$^{-1}$ which are tightened by a factor of $\sim 2$ and $\sim4$, respectively, as compared to the previous rates. These rate estimates may have implications for short Gamma Ray Burst progenitor models assuming they are powered (solely) by DNS or NSBH mergers. While these results are based on a set of open access population synthesis models which may not necessarily be the representative ones, the proposed method is very general and can be applied to any number of models thereby yielding more realistic constraints on the DNS and NSBH merger rates from the inferred BBH rate and chirp mass. These constraints on DNS and NSBH merger rates will be further tightened by future detections of BBH mergers by aLIGO.

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A. Gupta, K. Arun and B. Sathyaprakash
Tue, 15 Aug 17

Comments: 5 pages, no figures, 4 tables

An application of an optimal statistic for characterising relative orientations [IMA]

We present the projected Rayleigh statistic (PRS), a modification of the classic Rayleigh statistic, as a test for non-uniform relative orientation between two sets of pseudo-vector fields. This gives an effective way of investigating whether polarization is preferentially parallel or perpendicular to filaments in the interstellar medium, for example; there are other potential applications in astrophysics, e.g. when comparing small-scale orientations with larger-scale shear patterns. We compare the efficiency of the PRS against histogram binning methods that have previously been used for characterising the relative orientations of gas column density structures with the mag- netic field projected on the plane of the sky. We specifically examine data for the Vela C molecular cloud, where the column density is inferred from Herschel submil- limetre observations, and the magnetic field from observations by the Balloon-borne Large-Aperture Submillimetre Telescope in the 250-, 350-, and 500-{\mu}m wavelength bands. We find that the projected Rayleigh statistic has greater statistical power than approaches that bin the relative orientation angles, and hence this circular statistic makes more efficient use of the information contained in the orientation data.

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D. Jow, R. Hill, D. Scott, et. al.
Tue, 15 Aug 17

Comments: 11 pages, 7 figures

HAWC High Energy Upgrade with a Sparse Outrigger Array [IMA]

The High Altitude Water Cherenkov (HAWC) gamma-ray observatory consists of 300 water Cherenkov detectors and has been fully operational since March 2015 in central Mexico. It detects cosmic- and gamma-ray showers in the TeV energy range. For multi-TeV energies, the shower reconstruction and hence the performance of the detector is affected by the partial containment of the showers within the array. To improve the sensitivity at the highest energies, HAWC is being upgraded with an outrigger array. It consists of 350 comparably much smaller water Cherenkov detectors, sparsely distributed around the HAWC main array. It will increase the instrumented area by a factor of 4-5. In this contribution, we will present the current status of the upgrade as well as simulation results on anticipated improvements in the performance of the observatory.

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V. Joshi and A. Jardin-Blicq
Tue, 15 Aug 17

Comments: Presented at the 35th International Cosmic Ray Conference (ICRC2017), Bexco, Busan, Korea. See arXiv:1708.02572 for all HAWC contributions

Application of a Zero-latency Whitening Filter to Compact Binary Coalescence Gravitational-wave Searches [IMA]

Joint electromagnetic and gravitational-wave (GW) observation is a major goal of both the GW astronomy and electromagnetic astronomy communities for the coming decade. One way to accomplish this goal is to direct follow-up of GW candidates. Prompt electromagnetic emission may fade quickly, therefore it is desirable to have GW detection happen as quickly as possible. A leading source of latency in GW detection is the whitening of the data. We examine the performance of a zero-latency whitening filter in a detection pipeline for compact binary coalescence (CBC) GW signals. We find that the filter reproduces signal-to-noise ratio (SNR) sufficiently consistent with the results of the original high-latency and phase-preserving filter for both noise and artificial GW signals (called “injections”). Additionally, we demonstrate that these two whitening filters show excellent agreement in $\chi^2$ value, a discriminator for GW signals.

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L. Tsukada, K. Cannon, C. Hanna, et. al.
Tue, 15 Aug 17

Comments: 8 pages, 12 figures

A Compact and Lightweight Fibered Photometer for the PicSat Mission [IMA]

PicSat is a nanosatellite developed to observe the transit of the giant planet beta Pictoris b, expected in late 2017. Its science objectives are: the observation of the transit of the giant planet’s Hill sphere, the detection of exocomets in the system, and the fine monitoring of the circumstellar disk inhomogeneities. To answer these objectives without exceeding the possibilities of a 3-unit Cubesat in terms of mass and power budget, a small but ambitious 2 kg opto-mechanical payload was designed. The instrument, specifically made for high precision photometry, uses a 3.5 cm effective aperture telescope which injects the light in a single-mode optical fiber linked to an avalanche photodiode. To ensure the stability of the light injection in the fiber, a fine pointing system based on a two-axis piezoelectric actuation system, is used. This system will achieve a sub-arcsecond precision, and ensure that an overall photometric precision of at least 200 ppm/hr can be reached.

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M. Nowak, S. Lacour, V. Lapeyrere, et. al.
Tue, 15 Aug 17

Comments: 8 pages, 7 figures, Proceedings of the AIAA/USU Conference on Small Satellites, 2017, Science Mission Payloads 1, SSC17-VI-01

An algorithm for the reconstruction of neutrino-induced showers in the ANTARES neutrino telescope [IMA]

Muons created by $\nu_\mu$ charged current (CC) interactions in the water surrounding the ANTARES neutrino telescope have been almost exclusively used so far in searches for cosmic neutrino sources. Due to their long range, highly energetic muons inducing Cherenkov radiation in the water are reconstructed with dedicated algorithms that allow the determination of the parent neutrino direction with a median angular resolution of about \unit{0.4}{\degree} for an $E^{-2}$ neutrino spectrum. In this paper, an algorithm optimised for accurate reconstruction of energy and direction of shower events in the ANTARES detector is presented. Hadronic showers of electrically charged particles are produced by the disintegration of the nucleus both in CC and neutral current (NC) interactions of neutrinos in water. In addition, electromagnetic showers result from the CC interactions of electron neutrinos while the decay of a tau lepton produced in $\nu_\tau$ CC interactions will in most cases lead to either a hadronic or an electromagnetic shower. A shower can be approximated as a point source of photons. With the presented method, the shower position is reconstructed with a precision of about \unit{1}{\metre}, the neutrino direction is reconstructed with a median angular resolution between \unit{2}{\degree} and \unit{3}{\degree} in the energy range of \SIrange{1}{1000}{TeV}. In this energy interval, the uncertainty on the reconstructed neutrino energy is about \SIrange{5}{10}{\%}. The increase in the detector sensitivity due to the use of additional information from shower events in the searches for a cosmic neutrino flux is also presented.

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A. Albert, M. Andre, M. Anghinolfi, et. al.
Tue, 15 Aug 17

Comments: N/A

Science-Driven Optimization of the LSST Observing Strategy [IMA]

The Large Synoptic Survey Telescope is designed to provide an unprecedented optical imaging dataset that will support investigations of our Solar System, Galaxy and Universe, across half the sky and over ten years of repeated observation. However, exactly how the LSST observations will be taken (the observing strategy or “cadence”) is not yet finalized. In this dynamically-evolving community white paper, we explore how the detailed performance of the anticipated science investigations is expected to depend on small changes to the LSST observing strategy. Using realistic simulations of the LSST schedule and observation properties, we design and compute diagnostic metrics and Figures of Merit that provide quantitative evaluations of different observing strategies, analyzing their impact on a wide range of proposed science projects. This is work in progress: we are using this white paper to communicate to each other the relative merits of the observing strategy choices that could be made, in an effort to maximize the scientific value of the survey. The investigation of some science cases leads to suggestions for new strategies that could be simulated and potentially adopted. Notably, we find motivation for exploring departures from a spatially uniform annual tiling of the sky: focusing instead on different parts of the survey area in different years in a “rolling cadence” is likely to have significant benefits for a number of time domain and moving object astronomy projects. The communal assembly of a suite of quantified and homogeneously coded metrics is the vital first step towards an automated, systematic, science-based assessment of any given cadence simulation, that will enable the scheduling of the LSST to be as well-informed as possible.

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Science. Collaboration-LSST, P. Marshall, T. Anguita, et. al.
Tue, 15 Aug 17

Comments: 312 pages, 90 figures. Browse the current version at this https URL, new contributions welcome!