December 2021

SunnyNet: A neural network approach to 3D non-LTE radiative transfer. (arXiv:2112.13852v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Chappell_B/0/1/0/all/0/1">Bruce A. Chappell</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pereira_T/0/1/0/all/0/1">Tiago M. D. Pereira</a> Context. Computing spectra from 3D simulations of stellar atmospheres when allowing for departures from local thermodynamic equilibrium (non-LTE) is computationally very intensive. Aims. We develop a machine learning based method to speed up 3D non-LTE radiative transfer calculations in optically thick stellar atmospheres. Methods. Making use of a variety of 3D simulations of the solar atmosphere, we trained a convolutional neural network, SunnyNet, to learn the translation from LTE to non-LTE atomic populations. Non-LTE populations computed with an existing 3D code were considered asRead More →

The hand-made tail: Non-perturbative tails from multifield inflation. (arXiv:2112.14712v1 [hep-th]) <a href="http://arxiv.org/find/hep-th/1/au:+Achucarro_A/0/1/0/all/0/1">Ana Achucarro</a>, <a href="http://arxiv.org/find/hep-th/1/au:+Cespedes_S/0/1/0/all/0/1">Sebastian Cespedes</a>, <a href="http://arxiv.org/find/hep-th/1/au:+Davis_A/0/1/0/all/0/1">Anne-Christine Davis</a>, <a href="http://arxiv.org/find/hep-th/1/au:+Palma_G/0/1/0/all/0/1">Gonzalo A. Palma</a> It is becoming increasingly clear that large but rare fluctuations of the primordial curvature field, controlled by the tail of its probability distribution, could have dramatic effects on the current structure of the universe — {it e.g.} via primordial black-holes. However, the use of standard perturbation theory to study the evolution of fluctuations during inflation fails in providing a reliable description of how non-linear interactions induce non-Gaussian tails. Here, we use the stochastic inflation formalism to study the non-perturbative effects from multi-fieldRead More →

A forecast of using fast radio burst observations to constrain holographic dark energy. (arXiv:2108.04127v2 [astro-ph.CO] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Qiu_X/0/1/0/all/0/1">Xing-Wei Qiu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhao_Z/0/1/0/all/0/1">Ze-Wei Zhao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_L/0/1/0/all/0/1">Ling-Feng Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_J/0/1/0/all/0/1">Jing-Fei Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_X/0/1/0/all/0/1">Xin Zhang</a> Recently, about five hundred fast radio bursts (FRBs) detected by CHIME/FRB Project have been reported. The vast amounts of data would make FRBs a promising low-redshift cosmological probe in the forthcoming years, and thus the issue of how many FRBs are needed for precise cosmological parameter estimation in different dark energy models should be detailedly investigated. Different from the usually considered $w(z)$-parameterized models in the literature, in this work we investigate the holographic darkRead More →

Prospects for measuring dark energy with 21 cm intensity mapping experiments. (arXiv:2108.03552v2 [astro-ph.CO] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Wu_P/0/1/0/all/0/1">Peng-Ju Wu</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_X/0/1/0/all/0/1">Xin Zhang</a> Using the 21 cm intensity mapping (IM) technique can efficiently perform large-scale neutral hydrogen surveys, and this method has great potential for measuring dark-energy parameters. Some 21 cm IM experiments aiming at measuring dark energy in the redshift range of $0<z<3$ have been proposed and performed, in which the typical ones using single-dish mode include e.g., BINGO, FAST, and SKA1-MID, and those using interferometric mode include e.g., HIRAX, CHIME, and Tianlai. In this work, we make a forecast for these typical 21 cm IM experimentsRead More →

Prospective Sensitivities of Atom Interferometers to Gravitational Waves and Ultralight Dark Matter. (arXiv:2108.02468v2 [gr-qc] UPDATED) <a href="http://arxiv.org/find/gr-qc/1/au:+Badurina_L/0/1/0/all/0/1">Leonardo Badurina</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Buchmueller_O/0/1/0/all/0/1">Oliver Buchmueller</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Ellis_J/0/1/0/all/0/1">John Ellis</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Lewicki_M/0/1/0/all/0/1">Marek Lewicki</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+McCabe_C/0/1/0/all/0/1">Christopher McCabe</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Vaskonen_V/0/1/0/all/0/1">Ville Vaskonen</a> We survey the prospective sensitivities of terrestrial and space-borne atom interferometers (AIs) to gravitational waves (GWs) generated by cosmological and astrophysical sources, and to ultralight dark matter. We discuss the backgrounds from gravitational gradient noise (GGN) in terrestrial detectors, and also binary pulsar and asteroid backgrounds in space-borne detectors. We compare the sensitivities of LIGO and LISA with those of the 100m and 1km stages of the AION terrestrial AI project, asRead More →

Constraining Cluster Virialization Mechanism and Cosmology using Thermal-SZ-selected clusters from Future CMB Surveys. (arXiv:2107.10250v2 [astro-ph.CO] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Raghunathan_S/0/1/0/all/0/1">Srinivasan Raghunathan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Whitehorn_N/0/1/0/all/0/1">Nathan Whitehorn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alvarez_M/0/1/0/all/0/1">Marcelo A. Alvarez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Aung_H/0/1/0/all/0/1">Han Aung</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Battaglia_N/0/1/0/all/0/1">Nicholas Battaglia</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Holder_G/0/1/0/all/0/1">Gilbert P. Holder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nagai_D/0/1/0/all/0/1">Daisuke Nagai</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pierpaoli_E/0/1/0/all/0/1">Elena Pierpaoli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reichardt_C/0/1/0/all/0/1">Christian L. Reichardt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vieira_J/0/1/0/all/0/1">Joaquin D. Vieira</a> We forecast the number of galaxy clusters that can be detected via the thermal Sunyaev-Zeldovich (tSZ) signals by future cosmic microwave background (CMB) experiments, primarily the wide area survey of the CMB-S4 experiment but also CMB-S4’s smaller delensing survey and the proposed CMB-HD experiment. We predict that CMB-S4 will detect 75,000 clusters with its wideRead More →

Periodicity Search on X-ray Bursts of SGR J1935+2154 Using 8.5 yr of Fermi/GBM Data. (arXiv:2107.03800v4 [astro-ph.HE] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Zou_J/0/1/0/all/0/1">Jin-Hang Zou</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_B/0/1/0/all/0/1">Bin-Bin Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Zhang_G/0/1/0/all/0/1">Guo-Qiang Zhang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Yang_Y/0/1/0/all/0/1">Yu-Han Yang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shao_L/0/1/0/all/0/1">Lang Shao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_F/0/1/0/all/0/1">Fa-Yin Wang</a> We performed a systematic search for X-ray bursts of the SGR J1935+2154 using the Fermi Gamma-ray Burst Monitor continuous data dated from Jan 2013 to October 2021. Eight bursting phases, which consist of a total of 353 individual bursts, are identified. We further analyze the periodic properties of our sample using the Lomb-Scargle periodogram. The result suggests that those bursts exhibit a period of ~ 238 days with a ~Read More →

Via Machinae: Searching for Stellar Streams using Unsupervised Machine Learning. (arXiv:2104.12789v3 [astro-ph.GA] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Shih_D/0/1/0/all/0/1">David Shih</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Buckley_M/0/1/0/all/0/1">Matthew R. Buckley</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Necib_L/0/1/0/all/0/1">Lina Necib</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tamanas_J/0/1/0/all/0/1">John Tamanas</a> We develop a new machine learning algorithm, Via Machinae, to identify cold stellar streams in data from the Gaia telescope. Via Machinae is based on ANODE, a general method that uses conditional density estimation and sideband interpolation to detect local overdensities in the data in a model agnostic way. By applying ANODE to the positions, proper motions, and photometry of stars observed by Gaia, Via Machinae obtains a collection of those stars deemed most likely to belong to aRead More →

Anomaly Detection in Gravitational Waves data using Convolutional AutoEncoders. (arXiv:2103.07688v2 [astro-ph.IM] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Morawski_F/0/1/0/all/0/1">Filip Morawski</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bejger_M/0/1/0/all/0/1">Micha&#x142; Bejger</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cuoco_E/0/1/0/all/0/1">Elena Cuoco</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Petre_L/0/1/0/all/0/1">Luigia Petre</a> As of this moment, fifty gravitational waves (GW) detections have been announced, thanks to the observational efforts of the LIGO-Virgo Collaboration, working with the Advanced LIGO and the Advanced Virgo interferometers. The detection of signals is complicated by the noise-dominated nature of the data. Conventional approaches in GW detection procedures require either precise knowledge of the GW waveform in the context of matched filtering searches or coincident analysis of data from multiple detectors. Furthermore, the analysis is prone to contamination byRead More →

Bonn Optimized Stellar Tracks (BoOST). Simulated Populations of Massive and Very Massive Stars for Astrophysical Applications. (arXiv:2004.08203v3 [astro-ph.SR] UPDATED) <a href="http://arxiv.org/find/astro-ph/1/au:+Szecsi_D/0/1/0/all/0/1">Dorottya Sz&#xe9;csi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Agrawal_P/0/1/0/all/0/1">Poojan Agrawal</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Wunsch_R/0/1/0/all/0/1">Richard W&#xfc;nsch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Langer_N/0/1/0/all/0/1">Norbert Langer</a> Massive and very massive stars can play important roles in stellar populations by ejecting strong stellar winds and exploding in energetic phenomena. It is therefore imperative that their behavior be properly accounted for in synthetic model populations. We present nine grids of stellar evolutionary model sequences, together with finely resolved interpolated sequences and synthetic populations, of stars with 9-500 Msun and with metallicities ranging from Galactic metallicity down to 1/250 Zsun. The stellar modelsRead More →

Unravelling the role of cosmic velocity field in dark matter halo mass function using deep learning. (arXiv:2112.14743v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Etezad_Razavi_S/0/1/0/all/0/1">Saba Etezad-Razavi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abbasgholinejad_E/0/1/0/all/0/1">Erfan Abbasgholinejad</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sotoudeh_M/0/1/0/all/0/1">Mohammad-Hadi Sotoudeh</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hassani_F/0/1/0/all/0/1">Farbod Hassani</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Raeisi_S/0/1/0/all/0/1">Sadegh Raeisi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Baghram_S/0/1/0/all/0/1">Shant Baghram</a> We discuss an implementation of a deep learning framework to gain insight into the dark matter structure formation. We investigate the impact of velocity and density field information on the construction of halo mass function through cosmological $N$-body simulations. In this direction, we train a Convolutional Neural Network (CNN) on the initial snapshot of an only dark matter simulation to predict the halo mass that individual particles fall intoRead More →

New Fe I Level Energies and Line Identifications from Stellar Spectra. III. Initial Results from UV, Optical, and Infrared Spectra. (arXiv:2112.14742v1 [astro-ph.SR]) <a href="http://arxiv.org/find/astro-ph/1/au:+Peterson_R/0/1/0/all/0/1">Ruth C. Peterson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kurucz_R/0/1/0/all/0/1">Robert L. Kurucz</a> The spectrum of neutral iron is critical to astrophysics, yet furnace laboratory experiments cannot reach many high-lying Fe I levels. Instead, Peterson & Kurucz (2015) and Peterson, Kurucz & Ayres (2017) turned to UV and optical spectra of warm stars to identify and assign energies for 124 Fe I levels with 1900 detectable Fe I lines, and to derive astrophysical gf-values for over a thousand of these. An energy value was assumed for each unknownRead More →

Boosting the public engagement with astronomy through arts. (arXiv:2112.14702v1 [physics.ed-ph]) <a href="http://arxiv.org/find/physics/1/au:+Ivanov_V/0/1/0/all/0/1">Valentin D. Ivanov</a> Arts are a seamless way to introduce the general public to both basic and more sophisticated astronomical concepts. The visual richness of astronomy makes it attractive and easily incorporated in painting and literature. Astronomy is the only science with a muse – Urania – implying that, at least in the eyes of the ancients, it was an art itself. I review some less well known representation of astronomical concepts in literature with potential application in education. Arts are a seamless way to introduce the general public to both basic and moreRead More →

Solving Tolman-Oppenheimer-Volkoff equations in f(T) gravity: a novel approach applied to some realistic equations of state. (arXiv:2109.01155v2 [gr-qc] UPDATED) <a href="http://arxiv.org/find/gr-qc/1/au:+Araujo_J/0/1/0/all/0/1">Jos&#xe9; C. N. de Araujo</a>, <a href="http://arxiv.org/find/gr-qc/1/au:+Fortes_H/0/1/0/all/0/1">Hemily G. M. Fortes</a> There are many ways to probe alternative theories of gravity, namely, via: experimental tests at solar system scale, cosmological data and models, gravitational waves and compact objects. In the present paper we consider a model of gravity with torsion $f(T)$ applied to compact objects such as neutron stars (NSs) for a couple of realistic equations of state (EOS). To do so we follow our previous articles, in which we show how to model compact starsRead More →

Gravitational dark matter: free streaming and phase space distribution. (arXiv:2112.14668v1 [hep-ph]) <a href="http://arxiv.org/find/hep-ph/1/au:+Haque_M/0/1/0/all/0/1">Md Riajul Haque</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Maity_D/0/1/0/all/0/1">Debaprasad Maity</a> Gravitational dark matter (DM) is the simplest possible scenario that has recently gained interest in the early universe cosmology. In this scenario, DM is assumed to be produced from the decaying inflaton through the gravitational interaction during reheating. Gravitational production from the radiation bath will be ignored as our analysis shows it to be suppressed for a wide range of reheating temperatures. Ignoring any other internal parameters except the DM mass and spin, a particular inflation model such as $alpha$-attractor, with a specific scalar spectral index $(n_s)$Read More →

Sound velocity effects on the phase transition gravitational wave spectrum in the Sound Shell Model. (arXiv:2112.14650v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Wang_X/0/1/0/all/0/1">Xiao Wang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Huang_F/0/1/0/all/0/1">Fa Peng Huang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_Y/0/1/0/all/0/1">Yongping Li</a> Cosmological phase transition gravitational wave could provide a novel approach to study the early Universe. In most cases, the acoustic gravitational wave from sound wave mechanism is dominant. We study sound velocity effects on the acoustic phase transition gravitational wave spectrum in the Sound Shell Model using different sound velocities in symmetric and broken phases. We demonstrate that different sound velocities could obviously modify the peak frequency, peak amplitude, and shape of the corresponding gravitational wave power spectra.Read More →

The Power of Locality: Primordial Non-Gaussianity at the Map Level. (arXiv:2112.14645v1 [astro-ph.CO]) <a href="http://arxiv.org/find/astro-ph/1/au:+Baumann_D/0/1/0/all/0/1">Daniel Baumann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Green_D/0/1/0/all/0/1">Daniel Green</a> Primordial non-Gaussianity is a sensitive probe of the inflationary era, with a number of important theoretical targets living an order of magnitude beyond the reach of current CMB constraints. Maps of the large-scale structure of the universe, in principle, have the raw statistical power to reach these targets, but the complications of nonlinear evolution are thought to present serious, if not insurmountable, obstacles to reaching these goals. In this paper, we will argue that the challenge presented by nonlinear structure formation has been overstated. The information encodedRead More →

Correlated signals of first-order phase transitions and primordial black hole evaporation. (arXiv:2112.14588v1 [hep-ph]) <a href="http://arxiv.org/find/hep-ph/1/au:+Marfatia_D/0/1/0/all/0/1">Danny Marfatia</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Tseng_P/0/1/0/all/0/1">Po-Yan Tseng</a> Fermi balls produced in a cosmological first-order phase transition may collapse to primordial black holes (PBHs) if the fermion dark matter particles that comprise them interact via a sufficiently strong Yukawa force. We show that phase transitions described by a quartic thermal effective potential with vacuum energy, $0.1lesssim B^{1/4}/{rm MeV} lesssim 10^3$, generate PBHs of mass, $10^{-20}lesssim M_{rm PBH}/M_odot lesssim 10^{-16}$, and gravitational waves from the phase transition (at THEIA/$mu$Ares) can be correlated with an isotropic extragalactic X-ray/$gamma$-ray background from PBH evaporation (at AMEGO-X/e-ASTROGAM). Fermi ballsRead More →

agnpy: an open-source python package modelling the radiative processes of jetted active galactic nuclei. (arXiv:2112.14573v1 [astro-ph.IM]) <a href="http://arxiv.org/find/astro-ph/1/au:+Nigro_C/0/1/0/all/0/1">C. Nigro</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sitarek_J/0/1/0/all/0/1">J. Sitarek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gliwny_P/0/1/0/all/0/1">P. Gliwny</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sanchez_D/0/1/0/all/0/1">D. Sanchez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tramacere_A/0/1/0/all/0/1">A. Tramacere</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Craig_M/0/1/0/all/0/1">M. Craig</a> Modelling the broadband emission of jetted active galactic nuclei (AGN) constitutes one of the main research topics of extragalactic astrophysics in the multi-wavelength and multi-messenger domain. We present agnpy, an open-source python package modelling the radiative processes of relativistic particles accelerated in the jets of active galactic nuclei. The package includes classes describing the galaxy components responsible for line and thermal emission and calculates the absorption due to $gammagamma$ pair productionRead More →