Astrophysical Aspects Research Articles

Navigating Unknowns: Deep Learning Robustness for Gravitational-wave Signal Reconstruction

We present a rapid and reliable deep-learning-based method for gravitational-wave (GW) signal reconstruction from elusive, generic binary black hole mergers in LIGO data. We demonstrate that our model, AWaRe, effectively recovers GWs with parameters it has not encountered during training. This includes features like higher black hole masses, additional harmonics, eccentricity, and varied waveform systematics, which introduce complex modulations in the waveform’s amplitudes and phases. The accurate reconstructions of these unseen signal characteristics demonstrate AWaRe's ability to handle complex features in the waveforms. By directly incorporating waveform reconstruction uncertainty estimation into the AWaRe framework, we show that for real GW events, the uncertainties in AWaRe's reconstructions align closely with those achieved by benchmark algorithms like BayesWave and coherent WaveBurst. The robustness of our model to real GW events and its ability to extrapolate to unseen data open new avenues for investigations in various aspects of GW astrophysics and data analysis, including tests of general relativity and the enhancement of current GW search methodologies.

Formation of millisecond pulsars with wide orbits

ABSTRACT Millisecond pulsars (MSPs) are a kind of radio pulsars with short spin periods, playing a key role in many aspects of stellar astrophysics. In recent years, some more MSPs with wide orbits ($\gt 30\, \rm d$) have been discovered, but their origin is still highly unclear. In this work, according to an adiabatic power-law assumption for the mass-transfer process, we carried out a large number of complete binary evolution computations for the formation of MSPs with wide orbits through the iron core-collapse supernova (CCSN) channel, in which a neutron star originating from a CCSN accretes matter from a red-giant star and spun up to millisecond periods. We found that this channel can form the observed MSPs with wide orbits in the range of $30\!-\!1200\, {\rm d}$, in which the white dwarf (WD) companions have masses in the range of $0.28\!-\!0.55\, \rm M_{\odot }$. We also found that almost all the observed MSPs can be reproduced by this channel in the WD companion mass versus orbital period diagram. We estimate that the Galactic numbers of the resulting MSPs from the CCSN channel are in the range of $\sim 4.8\!-\!8.5\times 10^{5}$. Compared with the accretion-induced collapse channel, the CCSN channel provides a main way to produce MSPs with wide orbits.

A NEW SPHERICALLY SYMMETRIC NEUTRON STAR MODEL EMBEDDING CLASS I IN DURGAPAL METRIC

In this paper, we develop a novel spherically symmetric neutron star model by combining the two useful mathematical aspects of astrophysics, Karmakar’s condition and Durgapal metric for anisotropic stellar objects. We use Karmakar’s condition to embed a class I reducibility criteria in the model. The solutions are simplified by considering 𝒆𝝂=𝑩(𝟏+𝒙)𝟔, where 𝒙=𝑪𝒓𝟐, beyond the fifth model given by Durgapal. The model does not have the central singularity. The model well behaves for the realistic physical properties of the neutron stars. The energy density, the pressure in the radial direction, and the pressure in the tangential direction are positively finite and decrease from the center to the surface of the neutron stars. The redshift and the compression moduli are also positive finite. In the offered model, we take the values of the constants as 1.5760 ≤ A ≤ 2.295, 0.0602 ≤ B ≤ 0.5577, and 7.492 × 10-10 ≤ C ≤ 3.397 × 10-9 for the neutron stars EXO 1785-248, SMC X-1, Her X-1, 4U 1538-52, LMC X-4, and Cen X-3. The Buchdahl condition is well satisfied by the model.

The dynamic universe: realizing the potential of classical time domain and multimessenger astrophysics

In parallel with the multi-messenger revolution, major advances in time-domain astronomy across multiple science disciplines relevant to astrophysics are becoming more urgent to address. Aside from electromagnetic observations of gravitational wave events and explosive counterparts, there are a number of “classical” astrophysical areas that require new thinking for proper exploration in the time domain. How NASA, NSF, ESA, and ESO consider the 2020 USA Decadal Survey within the astronomy community, as well as the worldwide call to support and expand time domain and multi-messenger astrophysics, it is crucial that all areas of astrophysics, including stellar, galactic, Solar System, and exoplanetary science participate in the discussion, and that it not be made into an exclusive preserve of cosmological, high-energy, explosive and transient science. Time domain astronomy is used to explore many aspects of astrophysics–particularly concerning ground- and space-based mission science goals of exploring how the Universe works, understanding how did we get here, and are we alone. Time domain studies are already built into the core operations of many currently operating and future space telescopes (e.g., Roman, PLATO) as well as current and planned large areal ground-based surveys (e.g., Rubin). Time-domain observations designed for one scientific purpose, also lead to great discoveries in many other science areas. The recent advent of user-friendly hardware, software, observational approaches, and online data infrastructure has also helped make time domain observations especially suitable and appealing for citizen science projects. We provide a review of the current state of TDAMM alerts and observational protocols, revealing a wide array of software and applications, much of which is incompatible. Any conversation regarding TDAMM astrophysics should include all aspects of the field, including those aspects seen as classical applications.

Forecasting constraints on the baryon mass fraction in the IGM from fast radio bursts and type Ia supernovae

Fast Radio Bursts (FRBs) are millisecond transient radio events with a high energy. By identifying the origin of the burst, it is possible to measure the redshift of the host galaxy, which can be used to constrain cosmological and astrophysical parameters and test aspects of fundamental physics when combined with the dispersion measure (DM). However, some factors limit the cosmological application of FRBs: (i) the poor modelling of the fluctuations in the DM due to spatial variation in the cosmic electrons density; (ii) the fact that the fraction of baryon mass in the intergalactic medium (fIGM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{IGM}$$\\end{document}) is degenerated with some cosmological parameters; (iii) the limited knowledge about host galaxy contribution (DMhost\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$DM_{host}$$\\end{document}). In this work, we investigate the impact of different redshift distribution models of FRBs to constrain the baryon fraction in the IGM and host galaxy contribution. We use a cosmological model-independent method developed in previous work Lemos (EPJC 83:138, 2023) to perform the analysis and combine simulated FRB data from Monte Carlo simulation and supernovae data. We assume four distribution models for the FRBs: gamma-ray bursts (GRB), star formation rate (SFR), uniform and equidistant (ED). Also, we consider samples with N=15,30,100\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N = 15, 30, 100$$\\end{document} and 500 points and different values of the fluctuations of electron density in the DM, δ=0,100,200,400,230z\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\delta = 0, 100, 200, 400, 230\\sqrt{z}$$\\end{document} pc/cm3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$^{3}$$\\end{document}. Our analysis shows that all the distribution models present consistent results within 2σ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$2\\sigma $$\\end{document} for the free parameters fIGM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$f_{IGM}$$\\end{document} and DMhost,0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$DM_{host,0}$$\\end{document} and highlights the crucial role of DM fluctuations in obtaining more precise measurements.

Backsplash galaxies and their impact on galaxy evolution: a three-stage, four-type perspective

ABSTRACT We study the population of backsplash galaxies at z = 0 in the outskirts of massive, isolated clusters of galaxies taken from the mdpl2-sag semi-analytical catalogue. We consider four types of backsplash galaxies according to whether they are forming stars or passive at three stages in their lifetimes: before entering the cluster, during their first incursion through the cluster, and after they exit the cluster. We analyse several geometric, dynamic, and astrophysical aspects of the four types at the three stages. Galaxies that form stars at all stages account for the majority of the backsplash population (58 per cent) and have stellar masses typically below $M_\star \sim 3\times 10^{10} \ h^{-1}\, {\rm {M_\odot }}$ that avoid the innermost cluster’s regions and are only mildly affected by it. In a similar mass range, galaxies that become passive after exiting the cluster (26 per cent) follow orbits characterized by small pericentric distance and a strong deflection by the cluster potential well while suffering a strong loss of both dark matter and gas content. Only a small fraction of our sample (4 per cent) becomes passive while orbiting inside the cluster. These galaxies have experienced heavy pre-processing and the cluster’s tidal stripping and ram pressure provide the final blow to their star formation. Finally, galaxies that are passive before entering the cluster for the first time (12 per cent) are typically massive and are not affected significantly by the cluster. Using the bulge/total mass ratio as a proxy for morphology, we find that a single incursion through a cluster does not result in significant morphological changes in all four types.

Preface: 2nd International Forum on Mathematical Statistics, Physical Sciences and Telecommunication System (IFMPT 2023)

We are glad to introduce you that the 2023 2nd International Forum on Mathematical Statistics, Physical Sciences and Telecommunication System (IFMPT 2023) was successfully held on June 24-25, 2023 in Guangzhou, China. This forum aims to bring together academic scientists, leading engineers, industry researchers, and scholar students to exchange and share their experiences and research results about all aspects of mathematical statistics, mathematical model, physical sciences, quantum mechanics, astrophysics, 5G networking, and telecommunication system. This forum also discusses the practical challenges encountered and the solutions adopted.
 This scientific event brings together more than 50 national and international researchers. During the conference, the conference model was divided into three sessions, including oral presentations, keynote speeches, and online Q&A discussion. In the first part, some scholars, whose submissions were selected as the excellent papers, were given about 8-10 minutes to perform their oral presentations one by one. Then in the second part, keynote speakers were each allocated 30-40 minutes to hold their speeches.
 Lastly, we would like to express our sincere gratitude to the distinguished keynote speakers, as well as all the participants. We also want to thank the publisher for publishing the proceedings. We are expecting more and more experts and scholars from all over the world to join this international event next year.
 The Committee of IFMPT 2023
 Guangzhou, China

Aspects of Quantum Gravity Phenomenology and Astrophysics

With the discovery of gravitational waves, the search for the quantum of gravity, the graviton, is imminent. We discuss the current status of the bounds on graviton mass from experiments as well as the theoretical understanding of these particles. We provide an overview of current experiments in astrophysics such as the search for Hawking radiation in gamma-ray observations and neutrino detectors, which will also shed light on the existence of primordial black holes. Finally, the semiclassical corrections to the image of the event horizon are discussed.

Integrable teleparallel gravity in the presence of boundaries

Symmetric teleparallel gravity is shown to be integrable in the presence of boundaries, given the consistent implementation of constraints in the covariant phase space formalism.Received 14 October 2022Accepted 3 January 2023DOI:https://doi.org/10.1103/PhysRevD.107.024019© 2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlternative gravity theoriesGeneral relativityRelativistic aspects of cosmologyGravitation, Cosmology & Astrophysics

Main group cyanides: from hydrogen cyanide to cyanido-complexes

Abstract Homoleptic cyanide compounds exist of almost all main group elements. While the alkali metals and alkaline earth metals form cyanide salts, the cyanides of the lighter main group elements occur mainly as covalent compounds. This review gives an overview of the status quo of main group element cyanides and cyanido complexes. Information about syntheses are included as well as applications, special substance properties, bond lengths, spectroscopic characteristics and computations. Cyanide chemistry is presented mainly from the field of inorganic chemistry, but aspects of chemical biology and astrophysics are also discussed in relation to cyano compounds.

Anisotropic stars in modified gravity: An extended gravitational decoupling approach* *SKM and SR acknowledge that this work is carried out under TRC Project (Grant No. BFP/RGP/CBS-/19/099), the Sultanate of Oman. SKM and RN are thankful for continuous support and encouragement from the administration of University of Nizwa

In this study, we conduct an investigation on decoupling gravitational sources under the framework of gravity. Basically, the complete geometric deformation technique is employed, which facilitates finding the exact solutions to the anisotropic astrophysical system smoothly without imposing any particular ansatz for the deformation function. In addition, we used 5-dimensional Euclidean spacetime in order to describe the embedding Class I spacetime in order to obtain a solvable spherical physical system. The resulting solutions are both physically interesting and viable with new possibilities for investigation. Notably, the present investigation demonstrates that the mixture of + CGD translates to a scenario beyond the pure GR realm and helps to enhance the features of the interior astrophysical aspects of compact stellar objects. To determine the physical acceptability and stability of the stellar system based on the obtained solutions, we conducted a series of physical tests that satisfied all stability criteria, including the nonsingular nature of density and pressure.

Incorporation of class I charged generalized polytropes with Karmarkar and complexity factor

In the present paper, we will incorporate three very useful aspects of astrophysics, generalized polytropes, Karmarkar condition and complexity factor to study the compact objects. For this purpose a charged anisotropic fluid distribution is used under static spherical symmetry. We develop a framework for class I generalized charged Lane–Emden equations for non-isothermal and isothermal regimes. Generalized polytropic equation of state with its two cases, mass density and energy density along with complexity factor lead us to the systems of differential equations and these systems are solved numerically. Finally, solutions of these systems are discussed graphically.

A Search for Photons with Energies Above 2 × 1017 eV Using Hybrid Data from the Low-Energy Extensions of the Pierre Auger Observatory

Ultra-high-energy photons with energies exceeding 1017 eV offer a wealth of connections to different aspects of cosmic-ray astrophysics as well as to gamma-ray and neutrino astronomy. The recent observations of photons with energies in the 1015 eV range further motivate searches for even higher-energy photons. In this paper, we present a search for photons with energies exceeding 2 × 1017 eV using about 5.5 yr of hybrid data from the low-energy extensions of the Pierre Auger Observatory. The upper limits on the integral photon flux derived here are the most stringent ones to date in the energy region between 1017 and 1018 eV.

X-Ray and Ultraviolet Observations of the Eclipsing Binary V471 Tauri with XMM-Newton: X-Ray-Cycles, Eclipse Timings and Further Evidence of a Substellar Tertiary Companion

Few stars offer as much toward understanding fundamental aspects of stellar astrophysics and binary star evolution than the eclipsing binary V471 Tauri (DAZ+K2V; P = 12.52 hr). V471 Tauri (Tau) is the product of common-envelope binary evolution and a pre-cataclysmic variable. X-ray and UV (291 nm) observations were secured with XMM-Newton over ∼ 62 ks during 2019 September. X-ray and UV photometry show variations over the binary's orbit as well as flares. A precise eclipse timing was obtained from the UV photometry with the Optical Monitor. The timing was added to prior measures and fit with a 35.6 yr Light-Travel-Time-Effect (LTTE) Keplerian orbit of a substellar, tentative brown dwarf companion. However, this companion was not detected by VLT/SPHERE. The LTTE third-body solution appears reliable, now covering ∼50 yr of timings. The non-detection of the companion may be due to changes in its physical properties during the high-mass loss common envelope stage.

Galactic Anomalies and Particle Dark Matter

This is a brief review of aspects of galactic astrophysics and astronomy which have a possible bearing on particle dark matter. It is still quite normal for particle physicists to try to solve “well known anomalies“ that are apparently seen in observations of galaxies (missing satellites, cusp vs. core, etc.) whereas a lot of these anomalies have actually been resolved many years ago. We will try to briefly review the field and discuss many of the areas in question.

Editorial to the Special Issue “Advances in the Physics of Stars—In Memory of Prof. Yuri N. Gnedin”

This Special Issue collects articles devoted to various aspects of astrophysics which can be understood as a science investigating stars, galaxies, their types and properties, stages of their evolution, distribution in the Universe and the interstellar and intergalactic media [...]

Preface

This special issue of the Arabian Journal of Mathematics consists of research articles on some interesting topics in Theoretical & Mathematical Physics as well as theoretical aspects of Relativistic Astrophysics. These research articles were presented in an International Conference on Relativistic Astrophysics and Gravitation (ICRAG) held in Ulugh Beg Astronomical Institute of Uzbekistan during May 12–14, 2021.

Estimating cluster masses from SDSS multiband images with transfer learning

ABSTRACTThe total masses of galaxy clusters characterize many aspects of astrophysics and the underlying cosmology. It is crucial to obtain reliable and accurate mass estimates for numerous galaxy clusters over a wide range of redshifts and mass scales. We present a transfer-learning approach to estimate cluster masses using the ugriz-band images in the SDSS Data Release 12. The target masses are derived from X-ray or SZ measurements that are only available for a small subset of the clusters. We designed a semisupervised deep learning model consisting of two convolutional neural networks. In the first network, a feature extractor is trained to classify the SDSS photometric bands. The second network takes the previously trained features as inputs to estimate their total masses. The training and testing processes in this work depend purely on real observational data. Our algorithm reaches a mean absolute error (MAE) of 0.232 dex on average and 0.214 dex for the best fold. The performance is comparable to that given by redMaPPer, 0.192 dex. We have further applied a joint integrated gradient and class activation mapping method to interpret such a two-step neural network. The performance of our algorithm is likely to improve as the size of training data set increases. This proof-of-concept experiment demonstrates the potential of deep learning in maximizing the scientific return of the current and future large cluster surveys.

Geophysical and astrophysical aspects of the ecological condition of Transcarpathia

Geophysical and astrophysical aspects of the ecological condition of Transcarpathia

Potential model within a bound-to-continuum approach for low-energy nucleon radiative capture by C12 and O16

The nucleon radiative capture reactions are important in pure and applied nuclear physics, especially in nuclear astrophysics. The keV-nucleon radiative capture reactions are studied with $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$ targets using the bound-to-continuum potential model in which both scattering and bound states are treated simultaneously and based on the Skyrme Hartree-Fock approximation. The obtained results are shown to be in good agreement with the available experimental data. Alongside astrophysical aspects, the nuclear structure features were revisited for enlarging the prospect of adopting the nucleon radiative capture processes as a spectroscopic tool.