Category Archives: Uncategorized

Constraints on the scalar inflation from preheating of LATTICEEASY [CEA]

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http://arxiv.org/abs/2212.12851


In this paper, we study scalar inflation in detail by applying the preheating of LATTICEEASY simulation. In general, scalar inflation potential with non-minimal coupling can be approximated to the quartic potential inflation. We observe that the evolutionary trend of this potential is independent of the coupling coefficient, and theoretical predictions for the scalar spectral index $n_s$ and tensor-to-scalar power ratio $r$ are also independent of the coefficient, which implies that the coefficients of this model will not be bounded by the Planck observations. Fortunately, the properties of preheating after inflation provide a feasible scheme to study those coefficients. For the preheating process, the evolution of particle number density, scale factor, and energy density can be restored and tracked by applying LATTICEEASY simulation, then the parameters energy ratio $\gamma$ and the e-folding number of preheating $N_{pre}$ will be deduced, and the $n_s$ and $r$ can be further predicted. We have tested the scalar inflation model by the preheating nature of LATTICEEASY based on the analytical relationship between preheating and inflation models.

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W. Cheng and T. Qin
Tue, 27 Dec 22
22/30

Comments: 13 pages, 6 figures

The Orbital Architecture of Qatar-6: A Fully Aligned 3-Body System? [EPA]

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http://arxiv.org/abs/2212.02542


The evolutionary history of an extrasolar system is, in part, fossilized through its planets’ orbital orientations relative to the host star’s spin axis. However, spin-orbit constraints for warm Jupiters — particularly in binary star systems, which are amenable to a wide range of dynamical processes — are relatively scarce. We report a measurement of the Rossiter-McLaughlin effect, observed with the Keck/HIRES spectrograph, across the transit of Qatar-6 A b: a warm Jupiter orbiting one star within a binary system. From this measurement, we obtain a sky-projected spin-orbit angle $\lambda={0.1\pm2.6}^{\circ}$. Combining this new constraint with the stellar rotational velocity of Qatar-6 A that we measure from TESS photometry, we derive a true obliquity $\psi={21.82^{+8.86}{-18.36}}^{\circ}$ — consistent with near-exact alignment. We also leverage astrometric data from Gaia DR3 to show that the Qatar-6 binary star system is edge-on ($i{B}={90.17^{+1.07}_{-1.06}}^{\circ}$), such that the stellar binary and the transiting exoplanet orbit exhibit line-of-sight orbit-orbit alignment. Ultimately, we demonstrate that all current constraints for the 3-body Qatar-6 system are consistent with both spin-orbit and orbit-orbit alignment. High-precision measurements of the projected stellar spin rate of the host star and the sky-plane geometry of the transit relative to the binary plane are required to conclusively verify the full 3D configuration of the system.

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M. Rice, S. Wang, K. Gerbig, et. al.
Wed, 7 Dec 22
67/74

Comments: 17 pages, 7 figures, accepted to AJ

Per aspera ad astra simul: Through difficulties to the stars together [IMA]

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http://arxiv.org/abs/2208.08134


In this article, we detail the strategic partnerships “Per Aspera Ad Astra Simul” and “European Collaborating Astronomers Project: Espa\~na-Czechia-Slovakia”. These strategic partnerships were conceived to foment international collaboration for educational activities (aimed at all levels) as well as to support the development and growth of early career researchers. The activities, carried out under the auspices of these strategic partnerships, demonstrate that Key Action 2 of the Erasmus+ programme can be an extremely valuable resource for supporting international educational projects, as well as the great impact that such projects can have on the general public and on the continued development of early career researchers. We strongly encourage other educators to make use of the opportunities offered by the Erasmus+ scheme.

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D. Jones, P. Kabath, J. Garcia-Rojas, et. al.
Thu, 18 Aug 22
37/45

Comments: Accepted to Astronomy Education Journal

A dilaton-axion model for string cosmology [CL]

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http://arxiv.org/abs/2203.09398


The generic scale-invariant theory of an axion and a dilaton coupled to gravity in $d$-dimensions is generalized to a universal' one-axion model with two dilatons that reproduces itself under consistent dimensional-reduction/truncation. Flat FLRW cosmologies are shown to correspond to trajectories of a three-dimensional autonomous dynamical system, which we analyse with a focus on accelerated cosmic expansion, deriving the precise swampland bounds that exclude eternal acceleration. We also show that for two sets of values of its three independent parameters, the model is a consistent truncation of maximalmassive’ supergravity theories arising from string/M-theory; for these maximal-supergravity parameter values the FLRW cosmologies include some with a transient de Sitter-like phase, but not the recurring de Sitter-like phase or eternal cosmic acceleration that is possible for other parameter values.

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J. Russo and P. Townsend
Fri, 18 Mar 22
27/66

Comments: 35 pages, 5 figures

The R136 star cluster dissected with Hubble Space Telescope/STIS. III. The most massive stars and their clumped winds [SSA]

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http://arxiv.org/abs/2202.11080


Context: The star cluster R136 inside the LMC hosts a rich population of massive stars, including the most massive stars known. The strong stellar winds of these very luminous stars impact their evolution and the surrounding environment. We currently lack detailed knowledge of the wind structure that is needed to quantify this impact. Aims: To observationally constrain the stellar and wind properties of the massive stars in R136, in particular the parameters related to wind clumping. Methods: We simultaneously analyse optical and UV spectroscopy of 53 O-type and 3 WNh-stars using the FASTWIND model atmosphere code and a genetic algorithm. The models account for optically thick clumps and effects related to porosity and velocity-porosity, as well as a non-void interclump medium. Results: We obtain stellar parameters, surface abundances, mass-loss rates, terminal velocities and clumping characteristics and compare these to theoretical predictions and evolutionary models. The clumping properties include the density of the interclump medium and the velocity-porosity of the wind. For the first time, these characteristics are systematically measured for a wide range of effective temperatures and luminosities. Conclusions: We confirm a cluster age of 1.0-2.5 Myr and derive an initial stellar mass of $\geq 250 {\rm M}\odot$ for the most massive star in our sample, R136a1. The winds of our sample stars are highly clumped, with an average clumping factor of $f{\rm cl}=29\pm15$. We find tentative trends in the wind-structure parameters as a function of mass-loss rate, suggesting that the winds of stars with higher mass-loss rates are less clumped. We compare several theoretical predictions to the observed mass-loss rates and terminal velocities and find that none satisfactorily reproduces both quantities. The prescription of Krti\v{c}ka & Kub\’at (2018) matches best the observed mass-loss rates.

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S. Brands, A. Koter, J. Bestenlehner, et. al.
Wed, 23 Feb 22
41/50

Comments: Accepted for publication in A&A; Appendix I will not be included in the published version

Constraining three-nucleon forces with multimessenger data [HEAP]

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http://arxiv.org/abs/2010.03581


We report the results of a study aimed at inferring direct information on the repulsive three-nucleon potential $V^R_{ijk}$\textemdash driving the stiffness of the nuclear matter equation of state at supranuclear densities\textemdash from astrophysical observations. Using a Bayesian approach, we exploit the measurements of masses, radii and tidal deformabalities performed by the NICER satellite and the LIGO/Virgo collaboration, as well as the mass of the heaviest observed pulsar, to constrain the strength of $V^R_{ijk}$. Our results, largely determined by the bound on the maximum mass, suggest that existing and future facilities have the potential to provide valuable new insight on microscopic nuclear dynamics at supranuclear densities.

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A. Maselli, A. Sabatucci and O. Benhar
Fri, 9 Oct 20
5/64

Comments: 6 pages, 3 figures

Modelling the Galactic very-high-energy $γ$-ray source population [HEAP]

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http://arxiv.org/abs/2010.03305


The High Energy Stereoscopic System (H.E.S.S.) Galactic plane survey (HGPS) is to date the most comprehensive census of Galactic $\gamma$-ray sources at very high energies (VHE; $100\,\mathrm{GeV}\leq E\leq 100\,\mathrm{TeV}$). As a consequence of the limited sensitivity of this survey, the 78 detected $\gamma$-ray sources comprise only a small and biased subsample of the overall population. Still, numerical modelling allows us to study the VHE $\gamma$-ray source population in the Milky Way based on this sample. In this work, several azimuth-symmetric and spiral-arm models are compared for spatial source distribution. The luminosity and radius function of the population are derived from the source properties of the HGPS data set and are corrected for the sensitivity bias of the HGPS. Based on these models, VHE source populations are simulated and the subsets of sources detectable according to the HGPS are compared with HGPS sources. The power-law indices of luminosity and radius functions are determined to range between $-1.6$ and $-1.9$ for luminosity and $-1.1$ and $-1.6$ for radius. Azimuth-symmetric distributions and a distribution following a four-arm spiral structure without Galactic bar describe the HGPS data reasonably well. The total number of Galactic VHE sources is predicted to be in the range from 800 to 7000 with a total luminosity and flux of $(1.6-6.3) \cdot 10^{36}$~ph~s$^{-1}$ and $(3-15) \cdot 10^{-10}$~ph~cm$^{-2}$~s$^{-1}$, respectively. Depending on the model, the HGPS sample accounts for $(68-87)\%$ of the emission of the population in the scanned region. This suggests that unresolved sources represent a critical component of the diffuse emission measurable in the HGPS. With the foreseen jump in sensitivity of the Cherenkov Telescope Array, the number of detectable sources is predicted to increase by a factor between 5 – 9.

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C. Steppa and K. Egberts
Thu, 8 Oct 20
49/54

Comments: 11 pages, 11 figures, accepted for publication in Astronomy & Astrophysics

Dust and gas in the central region of NGC 1316 (Fornax A) — Its origin and nature [GA]

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http://arxiv.org/abs/2010.01606


The early-type galaxy NGC 1316 hosts about 10^7 solar masses of dust within a central radius of 5 kpc. These prominent dust structures are believed to have an external origin, which is also a popular interpretation for other dusty early-type galaxies. We use archival Hubble Space Telescope/ACS data to construct colour maps that delineate the dust pattern in detail, and we compare these data with maps constructed with data from MUSE of the VLT at the European Southern Observatory. Twelve MUSE pointings in wide field mode form a mosaic of the central 3.3’x2.4′. We use the tool PyParadise to fit the stellar population. We use the residual emission lines and the residual interstellar absorption NaI D-lines, and we measure line strengths, the velocity field, and the velocity dispersion field. The emission lines resemble LINER lines, with [NII] being the strongest line everywhere. Ionising sources are plausibly the post-asymptotic giant branch stars of the old or intermediate-age stellar population. There is a striking match between the dust structures, ionised gas, and atomic gas distributions, the last of which is manifested by interstellar absorption residuals of the stellar NaI D-lines. In the dust-free regions, the interstellar NaI D-lines appear in emission, which is indicative of a galactic wind. The velocity field of the ionised gas (and thus of the dust) is characterised by small-scale turbulent movements that indicate short lifetimes. At the very centre, a bipolar velocity field of the ionised gas is observed, which we interpret as an outflow. We identify a strongly inclined gaseous dusty disc along the major axis of NGC1316. A straight beam of ionised gas with a length of about 4 kpc emanates from the centre. Our findings are strongly suggestive of a dusty outflow. Nuclear outflows may be important dust-producing machines in galaxies. (Abridged)

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T. Richtler, M. Hilker and E. Iodice
Tue, 6 Oct 2020
66/85

Comments: 9 pages, 8 figures, accepted by Astron.Astrophys

Implications of Grain Size Distribution and Composition for the Correlation Between Dust Extinction and Emissivity [GA]

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http://arxiv.org/abs/2009.11869


We study the effect of variations in dust size distribution and composition on the correlation between the spectral shape of extinction (parameterized by $R_{\textrm{V}}$) and far-infrared dust emissivity (parameterized by the power-law index $\beta$). Starting from the size distribution models proposed by Weingartner & Draine (2001), using the dust absorption and emission properties derived by Laor & Draine (1993) for carbonaceous and silicate grains, and by Li & Draine (2001) for PAH grains, we calculate the extinction and compare it with the reddening vector derived by Schlafly et al. (2016). An optimizer and an MCMC are used to explore the space of available parameters for the size distributions. We find that larger grains are correlated with high $R_{\textrm{V}}$. However, this trend is not enough to explain the emission-extinction correlation observed by Schlafly et al. (2016). For the $R_{\textrm{V}}-\beta$ correlation to arise, we need to impose explicit priors for the carbonaceous and silicate volume priors as functions of $R_{\textrm{V}}$. The results show that a composition with higher ratio of carbonaceous to silicate grains leads to higher $R_{\textrm{V}}$ and lower $\beta$. A relation between $E(\textrm{B}-\textrm{V})/\tau_{353}$ and $R_{\textrm{V}}$ is apparent, with possible consequences for the recalibration of emission-based dust maps as a function of $R_{\textrm{V}}$.

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I. Zelko and D. Finkbeiner
Mon, 28 Sep 20
6/52

Comments: Accepted for publication in The Astrophysical Journal. 28 pages, 27 figures, 3 Tables

Revised and new proper motions for confirmed and candidate Milky Way dwarf galaxies [GA]

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http://arxiv.org/abs/2007.05011


A new derivation of systemic proper motions of Milky Way satellites is presented, and applied to 59 confirmed or candidate dwarf galaxy satellites using Gaia Data Release 2. This constitutes all known Milky Way dwarf galaxies (and likely candidates) as of May 2020 except the Magellanic Clouds, the Canis Major and Hydra 1 stellar overdensities, and the tidally disrupting Bootes III and Sagittarius dwarf galaxies. We derive systemic proper motions for the first time for Indus 1, Pictoris 1, DES J0225+0304, Cetus 2, Pictor 2 and Leo T, but note that the latter three rely on photometry that is of poorer quality than for the rest of the sample. We cannot resolve a signal for Bootes 4, Cetus 3, Indus 2, Pegasus 3, or Virgo 1. Our method is inspired by the maximum likelihood approach of Pace & Li (2019) and examines simultaneously the spatial, color-magnitude, and proper motion distribution of sources. Systemic proper motions are derived without the need to identify confirmed radial velocity members, although the proper motions of these stars, where available, are incorporated into the analysis through a prior on the model. The associated uncertainties on the systemic proper motions are on average a factor of $\sim 1.4$ smaller than existing literature values, with 20\% of the measurements having measurement errors smaller by approximately a factor of 2 or more. Analysis of the implied membership distribution of the satellites suggests we accurately identify member stars with a contamination rate less than 1 in 20.

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A. McConnachie and K. Venn
Mon, 13 Jul 20
-99/64

Comments: 30 pages, 8 figures, 8 tables. Accepted for publication in the Astronomical Journal