RAS_WEB (Page 2)

Gravitational waves from nonradial oscillations of stochastically accreting neutron stars Wenhao Dong, Andrew Melatos arXiv:2404.11866v1 Announce Type: new Abstract: Oscillating neutron stars are sources of continuous gravitational waves. We study analytically the excitation of stellar oscillations by the mechanical impact on the stellar surface of ”clumps” of stochastically accreted matter. We calculate the waveform and spectrum of the gravitational wave signal emitted by the accretion-driven pulsations. Results are generated for an idealised model of a nonrotating, unmagnetised, one-component star with uniform polytropic index $n_{rm poly}$ assuming Newtonian gravity and the Cowling approximation. We find that the excited mode amplitudes grow with increasing $n_{rm poly}$ andRead More →

Finding the particularity of the active episode of SGR J1935+2154 during which FRB 20200428 occurred: Implication from a statistics of textit{Fermi}/GBM X-ray bursts Sheng-Lun Xie, Yun-Wei Yu, Shao-Lin Xiong, Lin Lin, Ping Wang, Yi Zhao, Yue Wang, Wen-Long Zhang arXiv:2404.11877v1 Announce Type: new Abstract: By using the textit{Fermi}/GBM data of the X-ray bursts (XRBs) of SGR J1935+2154, we investigate the temporal clustering of the bursts and the cumulative distribution of the waiting time and fluence/flux. It is found that the bursts occurring in the episode hosting FRB 20200428 have obviously shorter waiting times than those in the other episodes. The general statistical properties of theRead More →

Dark supernova remnant buried in the Galactic-Centre “Brick” G0.253+0.016 revealed by an expanding CO-line bubble Yoshiaki Sofue arXiv:2404.11892v1 Announce Type: new Abstract: We performed a $^{12}$CO- and $^{13}$CO($J=1-0$)-line study of the “Brick” (G0.253+0.016) in the Galactic Centre (GC) by analyzing the archival data obtained with the Nobeyama 45-m telescope. We present kinematics and molecular gas distributions in the longitude-velocity diagrams, and suggest that the Brick is located along the GC Arm I in the central molecular zone (CMZ) in front of the GC, which yields a distance of 8 kpc and GC radius 0.2 kpc. The major and minor-axis diameters of the Brick are $D_xtimesRead More →

A Self-Consistent Treatment of the Line-Driving Radiation Force for Active Galactic Nuclei Outflows: New Prescriptions for Simulations Aylecia S. Lattimer, Steven R. Cranmer arXiv:2404.11926v1 Announce Type: new Abstract: Flows driven by photons have been studied for almost a century, and a quantitative description of the radiative forces on atoms and ions is important for understanding a wide variety of systems with outflows and accretion disks, such as active galactic nuclei. Quantifying the associated forces is crucial to determining how these outflows enable interactive mechanisms within these environments, such as AGN feedback. The total number of spectral lines in any given ion of the outflow materialRead More →

MINDS: Mid-infrared atomic and molecular hydrogen lines in the inner disk around a low-mass star Riccardo Franceschi, Thomas Henning, Beno^it Tabone, Giulia Perotti, Alessio Caratti o Garatti, Giulio Bettoni, Ewine F. van Dishoeck, Inga Kamp, Olivier Absil, Manuel G"udel, G"oran Olofsson, L. B. F. M. Waters, Aditya M. Arabhavi, Valentin Christiaens, Danny Gasman, Sierra L. Grant, Hyerin Jang, Donna Rodgers-Lee, Matthias Samland, Kamber Schwarz, Milou Temmink, David Barrado, Anthony Boccaletti, Vincent Geers, Pierre-Olivier Lagage, Eric Pantin, Tom P. Ray, Silvia Scheithauer, Bart Vandenbussche, Gillian Wright arXiv:2404.11942v1 Announce Type: new Abstract: This work aims to measure the mass accretion rate, the accretion luminosity, and more generallyRead More →

Coherent Inverse Compton Scattering in Fast Radio Bursts Revisited Yuanhong Qu, Bing Zhang arXiv:2404.11948v1 Announce Type: new Abstract: Growing observations of temporal, spectral, and polarization properties of fast radio bursts (FRBs) indicate that the radio emission of the majority of bursts is likely produced inside the magnetosphere of its central engine, likely a magnetar. We revisit the idea that FRBs are generated via coherent inverse Compton scattering (ICS) off low-frequency X-mode electromagnetic waves (fast magnetosonic waves) by bunches at a distance of a few hundred times of the magnetar radius. Following findings are revealed: 1. Crustal oscillations during a flaring event would excite kHz Alfv’enRead More →

The Fireball of November 24, 1970, as the Most Probable Source of the Ischgl Meteorite Maria Gritsevich, Jarmo Moilanen, Jaakko Visuri, Matthias M. M. Meier, Colin Maden, J"urgen Oberst, Dieter Heinlein, Joachim Flohrer, Alberto J. Castro-Tirado, Jorge Delgado-Garc’ia, Christian Koeberl, Ludovic Ferri`ere, Franz Brandst"atter, Pavel P. Povinec, Ivan S’ykora, Florian Schweidler arXiv:2404.11989v1 Announce Type: new Abstract: In June 1976, a pristine meteorite stone weighing approximately 1 kg, fully covered with a fresh black fusion crust, was collected on a mountain road in the high-altitude Alpine environment. The recovery took place while clearing the remnants of a snow avalanche, 2 km northwest of Ischgl in Austria.Read More →

Comparing the three-dimensional morphological asymmetries in the ejecta of Kepler and Tycho in X-rays Adrien Picquenot, Tyler Holland-Ashford, Brian J. Williams arXiv:2404.12002v1 Announce Type: new Abstract: Recent simulations have shown that asymmetries in the ejecta distribution of supernova remnants (SNRs) may be a reflection of asymmetries left over from the initial supernova explosion. Thus, SNR studies provide a vital means for testing and constraining model predictions in relation to the distribution of heavy elements, which are key to improving our understanding of the explosion mechanisms in Type Ia supernovae. The use of a novel blind source separation method applied to the megasecond X-ray observations ofRead More →

Generation of relativistic electrons at the termination shock in the solar flare region G. Mann, A. M. Veronig, F. Schuller arXiv:2404.12005v1 Announce Type: new Abstract: Solar flares are accompanied by an enhanced emission of electromagnetic waves from the radio up to the gamma-ray range. The associated hard X-ray (HXR) and microwave radiation is generated by energetic electrons, which carry a substantial part of the energy released during a flare. The flare is generally understood as a manifestation of magnetic reconnection in the corona. The so-called standard CSHKP model is one of the most widely accepted models for eruptive flares. The solar flare on September 10,Read More →

Generation and annihilation of three dimensional magnetic nulls in extrapolated solar coronal magnetic field: Data-based Implicit Large Eddy Simulation Yogesh Kumar Maurya (Udaipur Solar Observatory, Physical Research Laboratory, Udaipur, Rajasthan 313001, India, Department of Physics, Indian Institute of Technology, Gandhinagar, Gujarat 382055, India), Ramit Bhattacharyya (Udaipur Solar Observatory, Physical Research Laboratory, Udaipur, Rajasthan 313001, India), David I. Pontin (School of Information and Physical Sciences, University of Newcastle, Callaghan, NSW 2308, Australia) arXiv:2404.12034v1 Announce Type: new Abstract: Three-dimensional magnetic nulls are the points where magnetic field vanishes and are preferential sites for magnetic reconnection: a process which converts magnetic energy into heat and accelerates charged particlesRead More →

Resolved magnetohydrodynamic wave lensing in the solar corona Xinping Zhou, Yuandeng Shen, Ding Yuan, Rony Keppens, Xiaozhou Zhao, Libo Fu, Zehao Tang, Jiaoyang Wang, Chengrui Zhou arXiv:2404.12044v1 Announce Type: new Abstract: Electromagnetic wave lensing, a common physical phenomenon recognized in visible light for centuries, finds extensive applications in manipulating light in optical systems such as telescopes and cameras. Magnetohydrodynamic wave is a common perturbation phenomenon in the corona. By using high spatio-temporal resolution observations from the Solar Dynamics Observatory, here, we report the observation of a magnetohydrodynamic wave lensing in the highly ionized and magnetized coronal plasma, where quasi-periodic wavefronts emanated from a flare convergedRead More →

A method for non-linear inversion of the stellar structure applied to gravity-mode pulsators Eoin Farrell, Ga"el Buldgen, Georges Meynet, Patrick Eggenberger, Marc-Antoine Dupret, Dominic M. Bowman arXiv:2404.12052v1 Announce Type: new Abstract: We present a method for a non-linear asteroseismic inversion suitable for gravity-mode pulsators and apply it to slowly pulsating B-type (SPB) stars. Our inversion method is based on the iterative improvement of a parameterised static stellar structure model, which in turn is based on constraints from the observed oscillation periods. We present tests to demonstrate that the method is successful in recovering the properties of artificial targets both inside and outside the parameter space.Read More →

Does dark energy really revive using DESI 2024 data? Youri Carloni, Orlando Luongo, Marco Muccino arXiv:2404.12068v1 Announce Type: new Abstract: We investigate the impact of the Dark Energy Spectroscopic Instrument (DESI) 2024 data on dark energy scenarios. We thus analyze three typologies of models, the first in which the cosmic speed up is related to thermodynamics, the second associated with Taylor expansions of the barotropic factor, whereas the third based on emph{ad hoc} dark energy parameterizations. In this respect, we perform Monte Carlo Markov chain analyses, adopting the Metropolis-Hastings algorithm, of 12 models. To do so, we first work at the background, inferring emph{a posteriori}Read More →

Big Bang equivalence of $f(R)$ gravity with no cosmological lithium problem Abhijit Talukdar, Sanjeev Kalita arXiv:2404.12084v1 Announce Type: new Abstract: $f(R)$ gravity is one of the serious alternatives of general relativity having large range of astronomical consequences. In this work, we study Big Bang Nucleosynthesis (BBN) in $f(R)$ gravity theory. We consider modification to gravity due to the existence of primordial black holes in the radiation era which introduce additional degrees of freedom known as scalarons. We calculate the light element abundances by using the BBN code PArthENoPE. It is found that for a range of scalaron mass $(2.2-3.5) times 10^4$ eV, the abundance ofRead More →

Data reconstruction of the dynamical connection function in $f(Q)$ cosmology Yuhang Yang, Xin Ren, Bo Wang, Yi-Fu Cai, Emmanuel N. Saridakise arXiv:2404.12140v1 Announce Type: new Abstract: We employ Hubble data and Gaussian Processes in order to reconstruct the dynamical connection function in $f(Q)$ cosmology beyond the coincident gauge. In particular, there exist three branches of connections that satisfy the torsionless and curvatureless conditions, parameterized by a new dynamical function $gamma$. We express the redshift dependence of $gamma$ in terms of the $H(z)$ function and the $f(Q)$ form and parameters, and then we reconstruct it using 55 $H(z)$ observation data. Firstly, we investigate the case whereRead More →

Euclid preparation. Improving cosmological constraints using a new multi-tracer method with the spectroscopic and photometric samples Euclid Collaboration, F. Dournac, A. Blanchard, S. Ili’c, B. Lamine, I. Tutusaus, A. Amara, S. Andreon, N. Auricchio, H. Aussel, M. Baldi, S. Bardelli, C. Bodendorf, D. Bonino, E. Branchini, S. Brau-Nogue, M. Brescia, J. Brinchmann, S. Camera, V. Capobianco, J. Carretero, S. Casas, M. Castellano, S. Cavuoti, A. Cimatti, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, A. M. Di Giorgio, J. Dinis, M. Douspis, F. Dubath, X. Dupac, S. Dusini, A. Ealet, M. Farina, S. Farrens,Read More →

The 2018 outburst of MAXI J1820+070 as seen by Insight-HXMT Ningyue Fan, Songyu Li, Rui Zhan, Honghui Liu, Zuobin Zhang, Cosimo Bambi, Long Ji, Xiang Ma, James F. Steiner, Shuang-Nan Zhang, Menglei Zhou arXiv:2404.12161v1 Announce Type: new Abstract: We present an analysis of the whole 2018 outburst of the black hole X-ray binary MAXI J1820+070 with Insight-HXMT data. We focus our study on the temporal evolution of the parameters of the source. We employ two different models to fit the thermal spectrum of the disk: the Newtonian model DISKBB and the relativistic model NKBB. These two models provide different pictures of the source in theRead More →

Detection and prebiotic chemistry of possible glycine precursor molecule methylenimine towards the hot molecular core G10.47+0.03 Arijit Manna, Sabyasachi Pal arXiv:2404.12212v1 Announce Type: new Abstract: Amino acids are essential for the synthesis of protein. Amino acids contain both amine (R$-$NH$_{2}$) and carboxylic acid (R$-$COOH) functional groups, which help to understand the possible formation mechanism of life in the universe. Among the 20 types of amino acids, glycine (NH$_{2}$CH$_{2}$COOH) is known as the simplest non-essential amino acid. In the last 40 years, all surveys of NH$_{2}$CH$_{2}$COOH in the interstellar medium, especially in the star-formation regions, have failed at the millimeter and sub-millimeter wavelengths. We aimed toRead More →

A Photoionization model for the Infrared Coronal Line Emission in the Classical Nova V1716 Scorpii C. E. Woodward, G. Shaw, S. Starrfield, A. Evans, K. L. Page arXiv:2404.12227v1 Announce Type: new Abstract: A near-infrared spectrum of nova V1716 Scorpii (PNV J17224490-4137160), a recent bright (V_max = 7.3 mag), Fermi-LAT detected gamma-ray source, was modeled using the photoionization code CLOUDY. Abundances were estimated for He, C, N, O, Si, Al, Mg, Fe, Ne, S, Ca, and P. Notably, P (a factor of 120) and N (a factor of 248) are highly overabundant. It was necessary to assume the ejecta consist of two components (with a cylindricalRead More →

The formation of transiting circumplanetary debris discs from the disruption of satellite systems during planet-planet scattering Alexander J. Mustill, Melvyn B. Davies, Matthew A. Kenworthy arXiv:2404.12239v1 Announce Type: new Abstract: Several stars show deep transits consistent with discs of roughly 1 Solar radius seen at moderate inclinations, likely surrounding planets on eccentric orbits. We show that this configuration arises naturally as a result of planet-planet scattering when the planets possess satellite systems. Planet-planet scattering explains the orbital eccentricities of the discs’ host bodies, while the close encounters during scattering lead to the exchange of satellites between planets and/or their destabilisation. This leads to collisions betweenRead More →