Current date: 2024-04-19
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Created/updated limit: 2024-04-12 (7 days ago)
Suggested sets: physics, physics:astro-ph, physics:gr-qc, physics:physics
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OAI-PMH request: http://export.arxiv.org/oai2?verb=ListRecords&from=2024-04-19&until=2024-04-19&set=physics&metadataPrefix=arXiv
Number of records retrieved: 526
Keyword score statistics
score 5 -- 4 abstracts
score 4 -- 5 abstracts
score 3 -- 4 abstracts
score 2 -- 9 abstracts
score 1 -- 16 abstracts
in total -- 38 abstracts
Articles that appeared on 2024-04-19
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[abstract 1 / 38] Yes (score: 5)
- Title: Coherent Inverse Compton Scattering in Fast Radio Bursts RevisitedAuthors: Yuanhong Qu, Bing Zhang,Comments: 19 pages, 8 figuresSubjects: astro-ph.HECreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
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\'en waves. Fast MAGNETosonic waves with the same frequency can be generated directly or be converted from Alfv\'en waves at a large radius, with an amplitude large enough to power FRBs via the ICS process. 2. The cross section increases rapidly with radius and significant ICS can occur at $r \gtrsim 100 R_\star$ with emission power much greater than the curvature radiation power but still in the linear scattering regime. 3. The low-frequency fast MAGNETosonic waves naturally redistribute a fluctuating RELATIVISTIC plasma in the charge-depleted region to form bunches with the right size to power FRBs. 4. The required bunch net charge density can be sub-Goldreich-Julian, which allows a strong parallel electric field to accelerate the charges, maintain the bunches, and continuously power FRB emission. 5. This model can account for a wide range of observed properties of repeating FRB bursts, including high degrees of linear and circular POLARIZATION and narrow spectra as observed in many bursts from repeating FRB sources.
[abstract 2 / 38] Yes (score: 5) - Title: Generation of RELATIVISTIC electrons at the termination shock in the solar flare regionAuthors: G. Mann, A. M. Veronig, F. Schuller,Comments: Accepted for publication in A&ASubjects: astro-ph.SR astro-ph.HECreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
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, 2017 offers a unique opportunity to study this model. The observations from the Expanded Owens Valley Solar Array (EOVSA) show that 1.6x10^4 electrons with energies >300 keV were generated in the flare region. There are signatures in solar radio and extreme ultraviolet observations as well as numerical simulations that a termination shock (TS) appears in the MAGNETic RECONNECTion outflow region. Electrons accelerated at the TS can be considered to generate the loop-top HXR sources. In contrast to previous studies, we investigate whether the heating of the plasma at the TS provides enough RELATIVISTIC electrons needed for the HXR and microwave emission observed during the X8.2 solar flare on September 10, 2017. We studied the heating of the plasma at the TS by evaluating the jump in the temperature across the shock by means of the Rankine-Hugoniot relationships under coronal circumstances measured during that event. The part of RELATIVISTIC electrons was calculated in the heated downstream region. In the MAGNETic RECONNECTion outflow region, the plasma is strongly heated at the TS. Thus, there are enough energetic electrons in the tail of the electron distribution function needed for the microwave and HXR emission observed during that event. The generation of RELATIVISTIC electrons at the TS is a possible mechanism to explain the enhanced microwave and HXR radiation emitted during flares.
[abstract 3 / 38] Yes (score: 5) - Title: Generation and annihilation of three dimensional MAGNETic nulls in extrapolated solar coronal MAGNETic field: Data-based Implicit Large Eddy SimulationAuthors: Yogesh Kumar Maurya, Ramit Bhattacharyya, David I. Pontin,Comments:Subjects: astro-ph.SRCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
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 particles along with a rearrangement of MAGNETic field lines. In the solar corona, the RECONNECTions manifest as coronal transients including solar flares, coronal mass ejections and coronal JETs. The nulls are generally found to be collocated with complex active regions on the solar photosphere. Extrapolation of MAGNETic field from corresponding photospheric MAGNETogram indicate an abundance of these nulls in solar atmosphere. Nevertheless, their generation is still not well understood. Recently, Maurya et al. (2023) have demonstrated MAGNETic RECONNECTion to be a cause for generation and annihilation of MAGNETic nulls through MAGNETohydrodynamics simulation, where the initial MAGNETic field is idealized to have a single radial null. This article further extends the study in a more realistic scenario where the initial MAGNETic field is constructed by extrapolating photospheric MAGNETogram data and hence, incorporates field line complexities inherent to a complex active region. For the purpose, the active region NOAA 11977 hosting a C6.6 class flare is selected. The simulation is initiated using non-force-free extrapolated MAGNETic field from the photospheric vector MAGNETogram at around 02:48:00 UT on 17 February 2014, 16 minutes before the flare peak. The generation, annihilation and dynamics of nulls are explored by a complimentary usage of trilinear null detection technique and tracing of MAGNETic field line dynamics. It is found that the nulls can spontaneously generate/annihilate in pairs while preserving the topological degree and can have observational implications like footpoint brightenings. Magnetic RECONNECTion is found to be the cause of such generation and annihilation.
[abstract 4 / 38] Yes (score: 5) - Title: The 2018 outburst of MAXI J1820+070 as seen by Insight-HXMTAuthors: Ningyue Fan, Songyu Li, Rui Zhan, Honghui Liu, Zuobin Zhang, Cosimo Bambi, Long Ji, Xiang Ma, James F. Steiner, Shuang-Nan Zhang, Menglei Zhou,Comments: 15 pages, 10 figures, submitted to ApJ, comments welcomeSubjects: astro-ph.HECreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
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 the soft state. With DISKBB, we find that the inner edge of the disk is close to the innermost stable circular orbit of a fast-rotating BLACK HOLE and the corona changes geometry from the hard to the soft state, probably becoming compact and close to the BLACK HOLE. With NKBB, we find that the disk is truncated in the soft state and that the coronal geometry does not change significantly during the whole outburst. However, we find that the model with NKBB can predict an untruncated disk around a fast-rotating BLACK HOLE if we assume that the inclination angle of the disk is around 30 degrees (instead of 60 degrees, which is the inclination angle of the JET and is usually adopted as the inclination angle of the disk in the literature) and we employ a high-density reflection model. In such a case, we measure a high value of the BLACK HOLE spin parameter with observations in the soft state, in agreement with the high spin value found from the analysis of the reflection features and in disagreement with the low spin value found by previous continuum-fitting method measurements with the inclination angle of the disk set to the value of the inclination angle of the JET.
[abstract 5 / 38] Yes (score: 4) - Title: The Host Galaxy of a Dormant, Overmassive Black Hole at $z=6.7$ May Be Restarting Star FormationAuthors: Fabio Pacucci, Abraham Loeb, Ignas Juodžbalis,Comments: Accepted on Research Notes of the AAS. This is a concise note (3 pages, 1 figure) regarding the direct application of the model described in arXiv:2401.04159 to the source presented in arXiv:2403.03872Subjects: astro-ph.GA astro-ph.CO astro-ph.HECreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
JWST is discovering a large population of $z>4$ supermassive BLACK HOLEs (SMBHs) that are overmassive with respect to the stellar content of their hosts. A previous study developed a physical model to interpret this overmassive population as the result of QUASAR feedback acting on a compact host galaxy. In this Note, we apply this model to JADES GN 1146115, a dormant supermassive BLACK HOLE at $z=6.7$ whose mass is $\sim40\%$ of the host's mass in stars and accreting at $\sim2\%$ of the Eddington limit. The host has been forming stars at the low rate of $\sim 1 \, \rm M_\odot \,yr^{-1}$ for the past $\sim 100$ Myr. Our model suggests that this galactic system is on the verge of a resurgence of global STAR FORMATION activity. This transition comes after a period of domination by the effect of its overmassive BLACK HOLE, whose duration is comparable to typical QUASAR lifetimes.
[abstract 6 / 38] Yes (score: 4) - Title: IMBH Progenitors from Stellar Collisions in Dense Star ClustersAuthors: Elena González Prieto, Newlin C. Weatherford, Giacomo Fragione, Kyle Kremer, Frederic A. Rasio,Comments: Accepted for ApJ. Comments welcome. 19 pages, 10 figuresSubjects: astro-ph.GA astro-ph.HECreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
Very massive stars (VMSs) formed via a sequence of stellar collisions in dense star clusters have been proposed as the progenitors of massive BLACK HOLE seeds. VMSs could indeed collapse to form intermediate-mass BLACK HOLEs (IMBHs), which would then grow by accretion to become the supermassive black holes observed at the centers of galaxies and powering high-redshift QUASARs. Previous studies have investigated how different cluster initial conditions affect the formation of a VMS, including mass segregation, stellar collisions, and binaries, among others. In this study, we investigate the growth of VMSs with a new grid of Cluster Monte Carlo (CMC) star cluster simulations -- the most expansive to date. The simulations span a wide range of initial conditions, varying the number of stars, cluster density, stellar initial mass function (IMF), and primordial binary fraction. We find a gradual shift in the mass of the most massive collision product across the parameter space; in particular, denser clusters born with top-heavy IMFs provide strong collisional regimes that form VMSs with masses easily exceeding 1000 solar masses. Our results are used to derive a fitting formula that can predict the typical mass of a VMS formed as a function of the star cluster properties. Additionally, we study the stochasticity of this process and derive a statistical distribution for the mass of the VMS formed in one of our models, recomputing the model 50 times with different initial random seeds.
[abstract 7 / 38] Yes (score: 4) - Title: 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 burstsAuthors: Sheng-Lun Xie, Yun-Wei Yu, Shao-Lin Xiong, Lin Lin, Ping Wang, Yi Zhao, Yue Wang, Wen-Long Zhang,Comments: Accepted for publication in ApJSubjects: astro-ph.HECreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
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 the XRBs further indicate they could belong to a self-organized critical (SOC) system (e.g., starquakes), making them very similar to the earthquake phenomena. Then, according to a unified scaling law between the waiting time and energy of the earthquakes as well as their aftershocks, we implement an analogy analysis on the XRBs and find that the FRB episode owns more dependent burst events than the other episodes. It is indicated that the FRB emission could be produced by the interaction between different burst events, which could correspond to a collision between different seismic/Alfven waves or different explosion outflows. Such a situation could appear when the MAGNETar enters into a global intensive activity period.
[abstract 8 / 38] Yes (score: 4) - Title: A Self-Consistent Treatment of the Line-Driving Radiation Force for Active Galactic Nuclei Outflows: New Prescriptions for SimulationsAuthors: Aylecia S. Lattimer, Steven R. Cranmer,Comments:Subjects: astro-ph.GA astro-ph.HECreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
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 material must be tabulated in order to give a complete characterization of this force. Here we provide calculations of the dimensionless line force multiplier for AGN environments. For a wide array of representative AGN sources, we explicitly calculate the photoionization balance at the proposed wind-launching region above the accretion disk, compute the strength of the line-driving force on the gas, and revisit and formalize the role of the commonly-used ionization parameter $\xi$ in ultimately determining the line-driving force. We perform these computations and analyses for a variety of AGN central source properties, such as BLACK HOLE mass, initial wind velocity, and number density. We find that, while useful, the ionization parameter provides an incomplete description of the overall ionization state of the outflow material. We use these findings to provide an updated method for calculating the strength of the radiative line-driving using both the X-ray spectral index $\Gamma_X$ and the ionization parameter.
[abstract 9 / 38] Yes (score: 4) - Title: Images of Kerr-MOG BLACK HOLEs surrounded by geometrically thick MAGNETized equilibrium toriAuthors: Zelin Zhang, Songbai Chen, Jiliang Jing,Comments: 13 pages,7 figuresSubjects: gr-qc astro-ph.GACreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
We adopt general RELATIVISTIC ray-tracing (GRRT) schemes to study images of Kerr-MOG BLACK HOLEs surrounded by geometrically thick MAGNETized equilibrium tori, which belong to steady-state solutions of thick accretion disks within the framework of general RELATIVISTIC MAGNETohydrodynamics (GRMHD). The black hole possesses an extra dimensionless MOG parameter described its deviation from usual Kerr one. Our results show that the presence of the MOG parameter leads to smaller disks in size, but enhances the total flux density and peak brightness in their images. Combining with observation data of BLACK HOLE M87* from the Event Horizon Telescope (EHT), we make a constraint on parameters of the Kerr-MOG BLACK HOLE and find that the presence of the MOG parameter broadens the allowable range of BLACK HOLE spin.
[abstract 10 / 38] Yes (score: 3) - Title: Semiclassical bremsstrahlung from a charge radially falling into a Schwarzschild BLACK HOLEAuthors: João P. B. Brito, Rafael P. Bernar, Atsushi Higuchi, Luís C. B. Crispino,Comments: 17 pages, 15 figures, published versionSubjects: gr-qc astro-ph.HECreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
A semiclassical investigation of the electroMAGNETic radiation emitted by a charged particle in a radially freely falling motion in Schwarzschild spacetime is carried out. We use quantum field theory at tree level to obtain the one-particle-emission amplitudes. We analyze and compare the energy spectrum and total energy released, which are calculated from these amplitudes, for particles with varying initial positions and for particles originating from infinity with varying kinetic energy. We also compare the results with those due to a falling charged "string" extended in the radial direction.
[abstract 11 / 38] Yes (score: 3) - Title: Efficient Identification of Broad Absorption Line Quasars using Dimensionality Reduction and Machine LearningAuthors: Wei-Bo Kao, Yanxia Zhang, Xue-Bing Wu,Comments: 17 pages, 6 figures, accepted for publication in PASJSubjects: astro-ph.GACreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
Broad Absorption Line Quasars (BALQSOs) displaying distinct blue-shifted broad absorption lines. These serve as invaluable probes for unraveling the intricate structure and evolution of QUASARs, shedding light on the profound influence exerted by supermassive BLACK HOLEs on galaxy formation. The proliferation of large-scale spectroscopic surveys such as LAMOST, SDSS, and DESI has exponentially expanded the repository of QUASAR spectra at our disposal. In this study, we present an innovative approach to streamline the identification of BALQSOs, leveraging the power of dimensionality reduction and machine learning algorithms. Our dataset is curated from the SDSS DR16, amalgamating QUASAR spectra with classification labels sourced from the DR16Q QUASAR catalog. We employ a diverse array of dimensionality reduction techniques, including Principal Component Analysis (PCA), t-Distributed Stochastic Neighbor Embedding (t-SNE), Locally Linear Embedding (LLE), and Isometric Mapping (ISOMAP), to distill the essence of the original spectral data. The resultant low-dimensional representations serve as inputs for a suite of machine learning classifiers, including XGBoost and Random Forest models. Through experimentation, we unveil PCA as the most effective dimensionality reduction methodology, adeptly navigating the intricate balance between dimensionality reduction and preservation of vital spectral information. Notably, the synergistic fusion of PCA with the XGBoost classifier emerges as the pinnacle of efficacy in the BALQSO classification endeavor, boasting impressive accuracy rates of 97.60% by 10-cross validation and 96.92% on the outer test sample. This study not only introduces a novel machine learning-based paradigm for QUASAR classification but also offers invaluable insights transferrable to a myriad of spectral classification challenges pervasive in the realm of astronomy.
[abstract 12 / 38] Yes (score: 3) - Title: A New Computational Method for Energetic Particle Acceleration and Transport with its FeedbackAuthors: Jeongbhin Seo, Fan Guo, Xiaocan Li, Hui Li,Comments: 15 pages, 8 figuresSubjects: astro-ph.HE astro-ph.GACreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
We have developed a new computational method to explore astrophysical and heliophysical phenomena, especially those considerably influenced by non-thermal energetic particles. This novel approach considers the backreaction from these energetic particles by incorporating the non-thermal fluid pressure into Magnetohydrodynamics (MHD) equations. The pressure of the non-thermal fluid is evaluated from the energetic particle distribution evolved through Parker's transport equation, which is solved using stochastic differential equations. We implement this method in the HOW-MHD code (Seo \& Ryu 2023), which achieves 5th-order accuracy. We find that without spatial diffusion, the method accurately reproduces the Riemann solution in the hydrodynamic shock tube test when including the non-thermal pressure. Solving Parker's transport equation allows the determination of pressure terms for both RELATIVISTIC and non-RELATIVISTIC non-thermal fluids with adiabatic indices $\gamma_{\rm{NT}}=4/3$ and $\gamma_{\rm{NT}}=5/3$, respectively. The method also successfully replicates the Magnetohydrodynamic shock tube test with non-thermal pressure, successfully resolving the discontinuities within a few cells. Introducing spatial diffusion of non-thermal particles leads to marginal changes in the shock but smooths the contact discontinuity. Importantly, this method successfully simulates the energy spectrum of the non-thermal particles accelerated through shock, which includes feedback from the non-thermal population. These results demonstrate that this method is very powerful for studying particle acceleration when a significant portion of the plasma energy is taken by energetic particles.
[abstract 13 / 38] Yes (score: 3) - Title: Gemini Near Infrared Spectrograph -- Distant Quasar Survey: Rest-Frame Ultraviolet-Optical Spectral Properties of Broad Absorption Line QuasarsAuthors: Harum Ahmed, Ohad Shemmer, Brandon Matthews, Cooper Dix, Trung Ha, Gordon T. Richards, Michael S. Brotherton, Adam D. Myers, W. N. Brandt, Sarah C. Gallagher, Richard Green, Paulina Lira, Jacob N. McLane, Richard M. Plotkin, Donald P. Schneider,Comments: 18 pages (AASTeX 6.3.1), 5 figures, accepted for publication in ApJSubjects: astro-ph.GACreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
We present the rest-frame ultraviolet-optical spectral properties of 65 broad absorption line (BAL) QUASARs from the Gemini Near Infrared Spectrograph-Distant Quasar Survey (GNIRS-DQS). These properties are compared with those of 195 non-BAL QUASARs from GNIRS-DQS in order to identify the drivers for the appearance of BALs in QUASAR spectra. In particular, we compare equivalent widths and velocity widths, as well as velocity offsets from systemic redshifts, of principal emission lines. In spite of the differences between their rest-frame ultraviolet spectra, we find that luminous BAL QUASARs are generally indistinguishable from their non-BAL counterparts in the rest-frame optical band at redshifts $1.55 \lesssim z \lesssim 3.50$. We do not find any correlation between BAL trough properties and the H$\beta$-based supermassive BLACK HOLE masses and normalized accretion rates in our sample. Considering the Sloan Digital Sky Survey QUASAR sample, which includes the GNIRS-DQS sample, we find that a monochromatic luminosity at rest-frame 2500 A of $\gtrsim 10^{45}$ erg s$^{-1}$ is a necessary condition for launching BAL outflows in QUASARs. We compare our findings with other BAL QUASAR samples and discuss the roles that accretion rate and orientation play in the appearance of BAL troughs in QUASAR spectra.
[abstract 14 / 38] (score: 2) - Title: Supermassive BLACK HOLEs from runaway mergers and accretion in nuclear star clustersAuthors: Konstantinos Kritos, Emanuele Berti, Joseph Silk,Comments: 4 pages, 3 figuresSubjects: astro-ph.HE gr-qcCreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
Rapid formation of supermassive BLACK HOLEs occurs in dense nuclear star clusters that are initially gas-dominated. Stellar-mass BLACK HOLE remnants of the most massive cluster sink into the core, where a massive runaway BLACK HOLE forms as a consequence of combined effects of repeated mergers and Eddington-limited gas accretion. The associated gravitational-wave signals of high-redshift extreme mass-ratio inspirals are a unique signature of the nuclear star cluster scenario.
[abstract 15 / 38] (score: 2) - Title: Evidence for a nearly orthogonal rotator in GX 301--2 with phase-resolved cyclotron resonant scattering featuresAuthors: Xiao Chen, Yuanze Ding, Wei Wang, Osamu Nishimura, Qi Liu, Shuang-Nan Zhang, Mingyu Ge, Fangjun Lu, Jinlu Qu, Liming Song, Shu Zhang,Comments: 17 pages, 15 figures, 3 tables, MNRAS in press. The early version of this work has been submitted in 2022, which provided the first measurement of the magnetic inclination angle for an accreting pulsar before IXPESubjects: astro-ph.HE astro-ph.SRCreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
Cyclotron resonant scattering features (CRSFs) are the absorption features in the X-ray spectra of strongly MAGNETized accretion neutron stars (NSs), which are probably the most reliable probe to the surface MAGNETic fields of NSs. The high mass X-ray binary GX 301--2 exhibits a very wide, variable and complicated CRSF in the average spectra, which should be two absorption lines based on NuStar and Insight-HXMT observations. With the Insight-HXMT frequent observations, we performed the phase-resolved spectroscopy and confirmed two cyclotron absorption lines in the phase-resolved spectra, with their centroid energy ratio $\sim 1.6-1.7$ in the super-critical luminosity case. A major hindrance in understanding those CRSFs is the very poorly constrained MAGNETic inclination angle, which is also a fundamental property of a NS and key to understanding the emission characteristics of a pulsar. Comparing the phase-resolved CRSF with simulated X-ray spectra, the MAGNETic inclination angle is found to be $\gtrsim 70^{\circ}$, i.e., nearly orthogonal between the NS's spin and MAGNETic axies. The implications of an orthogonal rotator and MAGNETic structure evolution in the accreting X-ray binary are also discussed.
[abstract 16 / 38] (score: 2) - Title: Gravitational waves from nonradial oscillations of stochastically accreting neutron starsAuthors: Wenhao Dong, Andrew Melatos,Comments: 18 pages, 8 figures. accepted in MNRASSubjects: astro-ph.HE gr-qcCreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
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 $n_{\rm poly}$ and mode order $n$. The gravitational wave signal forms a sequence of amplitude-modulated packets for $n_{\rm poly}=1$, lasting $\sim 10^{-3}$s after each impact. The gravitational wave strain increases with increasing $n_{\rm poly}$, but decreases with increasing $n$ and increasing multipole order $l$ for $n_{\rm poly}=1$. In the observing band of current long-baseline interferometers, $g$-modes emit higher, narrower peaks in the amplitude spectral density than $f$- and $p$-modes, with the highest peaks reaching $\sim 10^{-26}$Hz$^{-1/2}$ for modes with damping time $\tau_{nl} \sim 10^{8}$yr. The root-mean-square strain $h_{\text{rms}}$, calculated by summing over modes with $2\leq l\leq4$ and $\tau_{nl} \leq 10^{8}$yr, spans the range $10^{-33} \leq h_{\text{rms}} \leq 10^{-32}$ for $1\leq n_{\text{poly}}\leq 2$.
[abstract 17 / 38] (score: 2) - Title: Even-parity stability of hairy BLACK HOLEs in $U(1)$ gauge-invariant scalar-vector-tensor theoriesAuthors: Chao Zhang, Ryotaro Kase,Comments: 30 pages, 4 figuresSubjects: gr-qcCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
The $U(1)$ gauge-invariant scalar-vector-tensor theories, which catches five degrees of freedom, are valuable for its implications to inflation problems, generation of primordial MAGNETic fields, new BLACK HOLE (BH) and neutron star solutions, etc. In this paper, we derive conditions for the absence of ghosts and Laplacian instabilities of nontrivial BH solutions dressed with scalar hair against both odd- and even-parity perturbations on top of the static and spherically symmetric background in the most general $U(1)$ gauge-invariant scalar-vector-tensor theories with second-order equations of motion. In addition to some general discussions, several typical concrete models are investigated. Specially, we show that the stability against even-parity perturbations is ensured outside the event horizon under certain constraints to these models. This is a crucial step to check the self-consistency of the theories and to shed light on the physically accessible models of such theories for future studies.
[abstract 18 / 38] (score: 2) - Title: Saturation of the compression of two interacting MAGNETic flux tubes evidenced in the laboratoryAuthors: A. Sladkov, C. Fegan, W. Yao, A. F. A. Bott, S. N. Chen, H. Ahmed, E. D. Filippov, R. Lelièvre, P. Martin, A. McIlvenny, T. Waltenspiel, P. Antici, M. Borghesi, S. Pikuz, A. Ciardi, E. d'Humières, A. Soloviev, M. Starodubtsev, J. Fuchs,Comments:Subjects: physics.plasm-phCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
Interactions between MAGNETic fields advected by matter play a fundamental role in the Universe at all possible scales. A crucial role these interactions play is in making turbulent fields highly anisotropic, leading to observed ordered fields. These in turn, are important evolutionary factors for all the systems within and around. Despite scant evidence, due to the difficulty in measuring even near-Earth events, the MAGNETic field compression factor in these interactions, measured at very varied scales, is limited to a few. However, compressing matter in which a MAGNETic field is embedded, results in compression up to several thousands. Here we show, using laboratory experiments and matching three-dimensional hybrid simulations, that there is indeed a very effective saturation of the compression when two independent MAGNETic fields are advected by plasmas encounter. We found that the observed saturation is linked to a build-up of the MAGNETic pressure at the inflows encounter point, which decelerates them and thereby stops further compression. Moreover, the growth of an electric field, induced by the incoming flows and the MAGNETic field, acts in redirecting the inflows transversely, further hampering field compression.
[abstract 19 / 38] (score: 2) - Title: Robust and Adaptive Deep Reinforcement Learning for Enhancing Flow Control around a Square Cylinder with Varying Reynolds NumbersAuthors: Wang Jia, Hang Xu,Comments:Subjects: physics.flu-dynCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
The present study applies a Deep Reinforcement Learning (DRL) algorithm to Active Flow Control (AFC) of a two-dimensional flow around a confined square cylinder. Specifically, the Soft Actor-Critic (SAC) algorithm is employed to modulate the flow of a pair of synthetic JETs placed on the upper and lower surfaces of the confined squared cylinder in flow configurations characterized by Re of 100, 200, 300, and 400. The investigation starts with an analysis of the baseline flow in the absence of active control. It is observed that at Re = 100 and Re = 200, the vortex shedding exhibits mono-frequency characteristics. Conversely, at Re = 300 and Re = 400, the vortex shedding is dominated by multiple frequencies, which is indicative of more complex flow features. With the application of the SAC algorithm, we demonstrate the capability of DRL-based control in effectively suppressing vortex shedding, while significantly diminishing drag and fluctuations in lift. Quantitatively, the data-driven active control strategy results in a drag reduction of approximately 14.4%, 26.4%, 38.9%, and 47.0% for Re = 100, 200, 300, and 400, respectively. To understand the underlying control mechanism, we also present detailed flow field comparisons, which showcase the adaptability of DRL in devising distinct control strategies tailored to the dynamic conditions at varying Re. These findings substantiate the proficiency of DRL in controlling chaotic, multi-frequency dominated vortex shedding phenomena, underscoring the robustness of DRL in complex AFC problems.
[abstract 20 / 38] (score: 2) - Title: Improving inference on neutron star properties using information from binary merger remnantsAuthors: Tamanna Jain, Michalis Agathos,Comments: 5 figures and 2 tablesSubjects: gr-qc astro-ph.HECreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
The gravitational-wave signal GW170817 is a result of a binary neutron star coalescence event. The observations of electroMAGNETic counterparts suggest that the event didn't led to the prompt formation of a black-hole. In this work, we first classify the GW170817 LIGO-Virgo data sample into prompt collapse to a black-hole using the $q$-dependent threshold mass fits and then remove these cases from the data sample. We find that the cases without a prompt black-hole formation do not support radii $ <$ 10 km unlike the LIGO-Virgo data sample. This is consistent with the maximum mass constraint, based on the binary pulsar J0348+0432, imposed LIGO-Virgo data sample. Additionally, we find that the cases without the prompt collapse to a black-hole improve the uncertainty range of neutron star radii from 3.3 km to 2.6 km for the data sample without the mass constraint and from 2.8 km to 2.5 km for the data sample with the mass constraint, implying improved constraints on the neutron star radii and hence the equation-of-state.
[abstract 21 / 38] (score: 2) - Title: A Photoionization model for the Infrared Coronal Line Emission in the Classical Nova V1716 ScorpiiAuthors: C. E. Woodward, G. Shaw, S. Starrfield, A. Evans, K. L. Page,Comments: 17 pages, 8 figures, 5 tablesSubjects: astro-ph.SRCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
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 cylindrical geometry): a dense component from which the bulk of the H, He, and neutral O~I and N emission arises and a more diffuse component from which most of the coronal lines arise. Some of the coronal lines are found to originate from both the dense and diffuse components. The mass of the ejecta, including neutral and ionized gas, is ~ 4.19e-4 solar masses. Our analysis indicates that in the case of V1716 Sco (which has a carbon-oxygen white dwarf), a fraction of 25% white dwarf matter rather than 50% is favored for the mixing between white dwarf and the accreted envelope before the outburst. This mixing ratio is like that found for Oxygen-Neon novae where a 25% mixing fraction is also indicated. Helium hydride -- the first molecule to form after the Big Bang -- may have formed in the ejecta of V1716 Sco based on photoionization modeling. This prediction suggests that novae may be potential formation sites of this important molecular ion.
[abstract 22 / 38] (score: 2) - Title: Gravitational wave luminosity distance-weighted anisotropiesAuthors: A. Begnoni, L. Valbusa Dall Armi, D. Bertacca, A. Raccanelli,Comments: 23 pages, 7 figures (+ appendices)Subjects: astro-ph.CO gr-qcCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
Measurements of the luminosity distance of propagating gravitational waves can provide invaluable information on the geometry and content of our Universe. Due to the clustering of cosmic structures, in realistic situations we need to average the luminosity distance of events coming from patches inside a volume. In this work we evaluate, in a gauge-invariant and fully-RELATIVISTIC treatment, the impact of cosmological perturbations on such averaging process. We find that clustering, lensing and peculiar velocity effects impact estimates for future detectors such as Einstein Telescope, Cosmic Explorer, the Big Bang Observer and DECIGO. The signal-to-noise ratio of the angular power spectrum of the average luminosity distance over all the redshift bins is 17 in the case of binary BLACK HOLEs detected by Einstein Telescope and Cosmic Explorer. We also provide fitting formulas for the corrections to the average luminosity distance due to general RELATIVISTIC effects.
[abstract 23 / 38] (score: 1) - Title: Study of the $\sim 50$ kpc circumgalactic environment around the merger system J2057-0030 at $z$ $\sim$ 4.6 using ALMAAuthors: M. Fuentealba-Fuentes, P. Lira, T. Díaz-Santos, B. Trakhtenbrot, H. Netzer, L. Videla,Comments: 16 pages, 11 figures, 3 tables, accepted for publication in Astronomy and AstrophysicsSubjects: astro-ph.GACreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
We present ALMA band-7 observations of J2057-0030, a multi-component merger system at $z$ $\sim$ 4.68 spanning at least 50 kpc in size, using the [CII] $\lambda$157.74 $\mu$m line and underlying far-infrared (FIR) continuum. We find two main components, the QUASAR (QSO) and a dusty star-forming galaxy (DSFG), both detected in [CII] and continuum emission as well as multiple neighboring clumps detected only in [CII]. Three of these clumps form a (tidal) tail that extends from the QSO in a straight direction to the west, covering a projected distance of $\sim$ 10 kpc. This perturbed morphology, added to a spatial distance of $\sim$ 20 kpc and a velocity offset of $\Delta{v}$ = 68 km s$^{-1}$ between the QSO and the DSFG, strongly supports a merging scenario. By fitting a spectral energy distribution model to the continuum data, we estimate STAR FORMATION rates of $\approx$ 402 $M_{\odot}$ yr$^{-1}$ for the QSO host and $\approx$ 244 $M_{\odot}$ yr$^{-1}$ for the DSFG, which locate them on or close to the main sequence of star-forming galaxies. The J2057-0030 QSO was selected for being one of the brightest unobscured QUASARs at its redshift while presenting a rather modest STAR FORMATION rate. Based on a commonly accepted paradigm regarding the formation of QUASARs, this result is expected for a QUASAR that has already passed an obscured phase of rapid STAR FORMATION during a major merger. However, we see that the merger event in this system is far from being finished, and it is rather likely somewhere between the first pericenter and subsequent close passages. This is presumably another case of a high-$z$ QUASAR residing in a high-density environment with a companion obscured galaxy.
[abstract 24 / 38] (score: 1) - Title: Boltzmannian state counting for Black Hole Entropy in Causal Set TheoryAuthors: Vid Homšak, Stefano Veroni,Comments: 18 pages, 9 figuresSubjects: gr-qcCreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
This paper presents the first numerical study of BLACK HOLE thermodynamics in Causal Set Theory, focusing on the entropy of a Schwarzschild BLACK HOLE as embodied in the distribution of proposed horizon molecules. To simulate causal sets we created a highly parallelized computational framework in \texttt{C++} which allowed for the generation of causal sets with over a million points, the largest causal sets in a non-conformally flat spacetime to date. Our results confirm that the horizon molecules model is consistent with the Bekenstein-Hawking formula up to a dimensionless constant that can be interpreted as the fundamental discreteness scale in the order of a Planck length. Furthermore, the molecules are found to straddle the horizon of the BLACK HOLE to within a few Planck lengths, indicating that entropy lives on the surface of the BLACK HOLE. Finally, possible implications for the information paradox are drawn. In particular, we show how the horizon molecules model could yield a finite BLACK HOLE temperature cut-off or even prevent full BLACK HOLE evaporation.
[abstract 25 / 38] (score: 1) - Title: Future Perspectives for Gamma-ray Burst Detection from SpaceAuthors: Enrico Bozzo, Lorenzo Amati, Wayne Baumgartner, Tzu-Ching Chang, Bertrand Cordier, Nicolas De Angelis, Akihiro Doi, Marco Feroci, Cynthia Froning, Jessica Gaskin, Adam Goldstein, Diego Götz, Jon E. Grove, Sylvain Guiriec, Margarita Hernanz, C. Michelle Hui, Peter Jenke, Daniel Kocevski, Merlin Kole, Chryssa Kouveliotou, Thomas Maccarone, Mark L. McConnell, Hideo Matsuhara, Paul O'Brien, Nicolas Produit, Paul S. Ray, Peter Roming, Andrea Santangelo, Michael Seiffert, Hui Sun, Alexander van der Horst, Peter Veres, Jianyan Wei, Nicholas White, Colleen Wilson-Hodge, Daisuke Yonetoku, Weimin Yuan, Shuang-Nan Zhang,Comments: Accepted for publication on Universe. Invited review, contribution to the Universe Special Issue "Recent Advances in Gamma Ray Astrophysics and Future Perspectives", P. Romano eds. (https://www.mdpi.com/journal/universe/special_issues/7299902Z97)Subjects: astro-ph.IM astro-ph.HECreated: 2024-04-17; Updated: ; Datestamp: 2024-04-19
Since their first discovery in the late 1960s, Gamma-ray bursts have attracted an exponentially growing interest from the international community due to their central role in the most highly debated open questions of the modern research of astronomy, astrophysics, cosmology, and fundamental physics. These range from the intimate nuclear composition of high density material within the core of ultra-dense neuron stars, to stellar evolution via the collapse of massive stars, the production and propagation of gravitational waves, as well as the exploration of the early Universe by unveiling first stars and galaxies (assessing also their evolution and cosmic re-ionization). GRBs have stimulated in the past $\sim$50 years the development of cutting-edge technological instruments for observations of high energy celestial sources from space, leading to the launch and successful operations of many different scientific missions (several of them still in data taking mode nowadays). In this review, we provide a brief description of the GRB-dedicated missions from space being designed and developed for the future. The list of these projects, not meant to be exhaustive, shall serve as a reference to interested readers to understand what is likely to come next to lead the further development of GRB research and associated phenomenology.
[abstract 26 / 38] (score: 1) - Title: Does spacetime have memories? Searching for gravitational-wave memory in the third LIGO-Virgo-KAGRA gravitational-wave transient catalogueAuthors: Shun Yin Cheung, Paul D. Lasky, Eric Thrane,Comments: 9 pages, 5 figures. Accepted for publicationSubjects: gr-qcCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
Gravitational-wave memory is a non-linear effect predicted by general relativity that remains undetected. We apply a Bayesian analysis framework to search for gravitational-wave memory using binary BLACK HOLE mergers in LIGO-Virgo-KAGRA's third gravitational-wave transient catalogue. We obtain a Bayes factor of $\ln \text{BF}=0.01$, in favour of the no-memory hypothesis, which implies that we are unable to measure memory with currently available data. This is consistent with previous work, suggesting that a catalogue of $\mathcal{O}(2000)$ binary BLACK HOLE mergers is needed to detect memory. We look for new physics by allowing the memory amplitude to deviate from the prediction of general relativity by a multiplicative factor $A$. We obtain an upper limit of $A<23$ ($95\%$ credibility).
[abstract 27 / 38] (score: 1) - Title: Analytical calculation of Kerr and Kerr-Ads BLACK HOLEs in $f(R)$ theoryAuthors: Ping Li, Yong-qiang Liu, Jiang-he Yang, Siwei Xu, Xiang-hua Zhai,Comments:Subjects: gr-qcCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
In this paper, we extend Chandrasekhar's method of calculating rotating black holes into $f(R)$ theory. We consider the Ricci scalar is a constant and derive the Kerr and Kerr-Ads metric by using the analytical mathematical method. Suppose that the spacetime is a 4-dimensional Riemannian manifold with a general stationary axisymmetric metric, we calculate Cartan's equation of structure and derive the Einstein tensor. In order to reduce the solving difficulty, we fix the gauge freedom to transform the metric into a more symmetric form. We solve the field equations in the two cases of the Ricci scalar $R=0$ and $R\neq 0$. In the case of $R=0$, the Ernst's equations are derived. We give the elementary solution of Ernst's equations and show the way to obtain more solutions including Kerr metric. In the case of $R\neq 0$, we reasonably assume that the solution to the equations consists of two parts: the first is Kerr part and the second is introduced by the Ricci scalar. Giving solution to the second part and combining the two parts, we obtain the Kerr-Ads metric. The calculations are carried out in a general $f(R)$ theory, indicating the Kerr and Kerr-Ads BLACK HOLEs exist widely in general $f(R)$ models. Furthermore, the whole solving process can be treated as a standard calculation procedure to obtain rotating BLACK HOLEs, which can be applied to other modified gravities.
[abstract 28 / 38] (score: 1) - Title: Acceleration of electroMAGNETic shower development and enhancement of light yield in oriented scintillating crystalsAuthors: Mattia Soldani, Pietro Monti-Guarnieri, Alessia Selmi, Nicola Argiolas, Luca Bomben, Claudia Brizzolari, Nicola Canale, Stefano Carsi, Nikolaos Charitonidis, Davide De Salvador, Vincenzo Guidi, Viktar Haurylavets, Mikhail Korzhik, Giulia Lezzani, Alexander Lobko, Lorenzo Malagutti, Sofia Mangiacavalli, Valerio Mascagna, Andrea Mazzolari, Vitaly Mechinsky, Matthew Moulson, Riccardo Negrello, Gianfranco Paternò, Leonardo Perna, Christian Petroselli, Michela Prest, Marco Romagnoni, Federico Ronchetti, Giosué Saibene, Francesco Sgarbossa, Alexei Sytov, Viktor Tikhomirov, Erik Vallazza, Laura Bandiera,Comments:Subjects: hep-exCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
We observed a substantial increase of the scintillation light output of lead tungstate (PbWO$_4$) at a small incidence angle with respect to two main lattice axes. This reflects the acceleration of electroMAGNETic shower development that occurs in the crystalline Strong Field. We measured the scintillation light generated by $120$-$\mathrm{GeV}$ electrons and $10$-$100$-$\mathrm{GeV}$ $\gamma$ rays on thick samples. This result deepens the knowledge of the shower development mechanisms in crystal scintillators and could pave the way to the development of innovative accelerator- and space-borne calorimeters.
[abstract 29 / 38] (score: 1) - Title: First 2D electron density measurements using Coherence Imaging Spectroscopy in the MAST-U Super-X divertorAuthors: N. Lonigro, R. Doyle, J. S. Allcock, B. Lipschultz, K. Verhaegh, C. Bowman, D. Brida, J. Harrison, O. Myatra, S. Silburn, C. Theiler, T. A. Wijkamp, MAST-U Team, the EUROfusion Tokamak Exploitation Team,Comments:Subjects: physics.plasm-phCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
2D profiles of electron density and neutral temperature are inferred from multi-delay Coherence Imaging Spectroscopy data of divertor plasmas using a non-linear inversion technique. The inference is based on imaging the spectral line-broadening of Balmer lines and can differentiate between the Doppler and Stark broadening components by measuring the fringe contrast at multiple interferometric delays simultaneously. The model has been applied to images generated from simulated density profiles to evaluate its performance. Typical mean absolute errors of 30 percent are achieved, which are consistent with Monte Carlo uncertainty propagation accounting for noise, uncertainties in the calibrations, and in the model inputs. The analysis has been tested on experimental data from the MAST-U Super-X divertor, where it infers typical electron densities of 2-3 $10^{19}$ m$^{-3}$ and neutral temperatures of 0-2 eV during beam-heated L-mode discharges. The results are shown to be in reasonable agreement with the other available diagnostics.
[abstract 30 / 38] (score: 1) - Title: Deep learning to detect gravitational waves from binary close encounters: Fast parameter estimation using normalizing flowsAuthors: Federico De Santi, Massimiliano Razzano, Francesco Fidecaro, Luca Muccillo, Lucia Papalini, Barbara Patricelli,Comments: 49 pages, 14 figures, accepted for publication in Physical Review D (PRD)Subjects: gr-qcCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
A yet undetected class of GW signals is represented by the close encounters between compact objects in highly-eccentric e~1 orbits, that can occur in binary systems formed in dense environments such as globular clusters. The expected gravitational signals are short-duration pulses that would repeat over a much longer time scale in case of multiple passages at periastron. These sources represent a unique opportunity of exploring astrophysical formation channels as well as a different way of testing GR. In the case of binary systems containing neutron stars, the observation of these sources could help to constrain the EOS, thanks to the signature left in the GW signal by the f-modes excitation that can occur during the encounter. The detection and PE of these signals is challenging given the short duration of expected signals and the sensitivities of current ground-based GW interferometers. We present a novel approach that exploits Probabilistic ML. We have used Conditional Normalizing Flows to model complex probability distributions and therefore infer posterior distributions for the source parameters. Fast detection and PE is very important as it could trigger electroMAGNETic follow-up campaigns and offer the possibility to study these events in a multimessenger context. To develop and test the algorithm, we have focused on the simulations of single bursts emission obtained using the Effective Fly-by formalism and embedded in the noise of aLIGO and Virgo during O3. Our proposed model outperforms standard Bayesian methods in accuracy and is 5 orders of magnitude faster, being able to produce 5x10^4 posterior samples in just 0.5s. The results are extremely promising and constitute the first successful attempt for a fast and complete parameter estimation of binary CEs using deep learning, offering a new approach to study the evolution of orbital parameters of compact binary systems.
[abstract 31 / 38] (score: 1) - Title: Resolved MAGNETohydrodynamic wave lensing in the solar coronaAuthors: Xinping Zhou, Yuandeng Shen, Ding Yuan, Rony Keppens, Xiaozhou Zhao, Libo Fu, Zehao Tang, Jiaoyang Wang, Chengrui Zhou,Comments: 24 pages, 9 figures, 1 table, published in Nature CommunicationsSubjects: astro-ph.SR astro-ph.GACreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
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 converged at a specific point after traversing a coronal hole. The entire process resembles an electroMAGNETic wave lensing from the source to the focus. Meanwhile, the MAGNETohydrodynamic wave lensing is well reproduced through a MAGNETohydrodynamic numerical simulation with full spatio-temporal resolution. We further investigate potential applications for coronal seismology, as the lensing process encodes information on the Alfv\'en speed, in conjunction with favorable geometric and density variations.
[abstract 32 / 38] (score: 1) - Title: Big Bang equivalence of $f(R)$ gravity with no cosmological lithium problemAuthors: Abhijit Talukdar, Sanjeev Kalita,Comments: 14 pages, 1 figure, 2 subfigures, Comments are welcomedSubjects: astro-ph.COCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
$f(R)$ 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 of lithium is lowered by $3-4$ times the value predicted by general RELATIVISTIC BBN which is a level desired to address the cosmological lithium problem. For the above scalaron mass range helium abundance is within observed bound. However, deuterium abundance is found to be increased by $3-6$ times the observed primordial abundance which calls for high efficiency of stellar formation and evolution processes for destruction of the same. A novel relation between scalaron mass and BLACK HOLE mass has been used to estimate that the above scalaron mass range corresponds to primordial BLACK HOLEs of sub-planetary mass ($\sim 10^{19}$ g) serving as one of the potential non-baryonic DARK MATTER candidates. We infer Big Bang equivalence of power law $f(R)$ gravity with primordial BLACK HOLEs.
[abstract 33 / 38] (score: 1) - Title: Scale Separation Effects on Simulations of Plasma TurbulenceAuthors: Jago Edyvean, Tulasi N. Parashar, Tom Simpson, James Juno, Gian Luca Delzanno, Fan Guo, Oleksandr Koshkarov, William H Matthaeus, Michael Shay, Yan Yang,Comments: 13 pages (including bibliography), 11 figures and 2 tablesSubjects: physics.plasm-phCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
Understanding plasma turbulence requires a synthesis of experiments, observations, theory, and simulations. In the case of kinetic plasmas such as the solar wind, the lack of collisions renders the fluid closures such as viscosity meaningless and one needs to resort to higher order fluid models or kinetic models. Typically, the computational expense in such models is managed by simulating artificial values of certain parameters such as the ratio of the Alfv\'en speed to the speed of light ($v_A/c$) or the relative mass ratio of ions and electrons ($m_i/m_e$). Although, typically care is taken to use values as close as possible to realistic values within the computational constraints, these artificial values could potentially introduce unphysical effects. These unphysical effects could be significant at sub-ion scales, where kinetic effects are the most important. In this paper, we use the ten-moment fluid model in the Gkeyll framework to perform controlled numerical experiments, systematically varying the ion-electron mass ratio from a small value down to the realistic proton-electron mass ratio. We show that the unphysical mass ratio has a significant effect on the kinetic range dynamics as well as the heating of both the plasma species. The dissipative process for both ions and electrons become more compressive in nature, although the ions remain nearly incompressible in all cases. The electrons move from being dominated by incompressive viscous like heating/dissipation, to very compressive heating/dissipation dominated by compressions/rarefactions. While the heating change is significant for the electrons, a mass ratio of $m_i/m_e \sim 250$ captures the asymptotic behaviour of electron heating.
[abstract 34 / 38] (score: 1) - Title: Energetic particle acceleration and transport with the novel Icarus$+$PARADISE modelAuthors: Edin Husidic, Nicolas Wijsen, Tinatin Baratashvili, Stefaan Poedts, Rami Vainio,Comments: 20 pages, 8 figuresSubjects: physics.space-ph astro-ph.SR physics.comp-phCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
With the rise of satellites and mankind's growing dependence on technology, there is an increasing awareness of space weather phenomena related to high-energy particles. Shock waves driven by coronal mass ejections (CMEs) and corotating interaction regions (CIRs) occasionally act as potent particle accelerators, generating hazardous solar energetic particles (SEPs) that pose risks to satellite electronics and astronauts. Numerical simulation tools capable of modelling and predicting large SEP events are thus highly demanded. We introduce the new Icarus$+$PARADISE model as an advancement of the previous EUHFORIA$+$PARADISE model. Icarus, based on the MPI-AMRVAC framework, is a three-dimensional MAGNETohydrodynamic code that models solar wind configurations from 0.1 au onwards, encompassing transient structures like CMEs or CIRs. Differing from EUHFORIA's uniform-only grid, Icarus incorporates solution adaptive mesh refinement (AMR) and grid stretching. The particle transport code PARADISE propagates energetic particles as test particles through these solar wind configurations by solving the focused transport equation in a stochastic manner. We validate our new model by reproducing EUHFORIA+PARADISE results. This is done by modelling the acceleration and transport of energetic particles in a synthetic solar wind configuration containing an embedded CIR. Subsequently, we illustrate how the simulation results vary with grid resolution by employing different levels of AMR. The resulting intensity profiles illustrate increased particle acceleration with higher levels of AMR in the shock region, better capturing the effects of the shock.
[abstract 35 / 38] (score: 1) - Title: Metamaterial-induced-transparency engineering through quasi-bound states in the continuum by using dielectric cross-shaped trimersAuthors: Maryam Ghahremani, Carlos J. Zapata-Rodriguez,Comments:Subjects: physics.opticsCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
This study presents a novel approach to activate a narrowband transparency line within a reflecting broadband window in all-dielectric metasurfaces, in analogy to the electroMAGNETically-induced transparency effect, by means of a quasi-bound state in the continuum (qBIC). We demonstrate that the resonance overlapping of a bright mode and a qBIC-based nearly-dark mode with distinct Q-factor can be fully governed by a silicon trimer-based unit cell with broken-inversion-symmetry cross shape, thus providing the required response under normal incidence of a linearly-polarized light. Our analysis that is derived from the far-field multipolar decomposition and near-field electroMAGNETic distributions uncovers the main contributions of different multipoles on the qBIC resonance, with governing MAGNETic dipole and electric quadrupole terms supplied by distinct parts of the dielectric ``molecule.'' The findings extracted from this research open up new avenues for the development of POLARIZATION-dependent technologies, with particular interest in its capabilities for sensing and biosensing.
[abstract 36 / 38] (score: 1) - Title: Understanding FERMIonic Generalized SymmetriesAuthors: Federico Ambrosino, Ran Luo, Yi-Nan Wang, Yi Zhang,Comments: 5 pages plus 2 appendicesSubjects: hep-thCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
We explore new aspects of internal fermionic shifting symmetries, present in physical systems such as free Dirac spinors and p-form tensor-spinor fields. We propose a novel procedure to gauge these global symmetries, which also introduces a new St\"uckelberg mechanism to give a mass to free fermionic fields. Furthermore, we find new MAGNETic fermionic symmetries in these physical systems whose charged objects are disorder operators. For the case of a Dirac spinor, we discuss an dual description, where the MAGNETic symmetry acts on the holonomies of a dual 2-form tensor-spinor. Further generalizations such as higher-group-like structures are also discussed.
[abstract 37 / 38] (score: 1) - Title: A link to the past: characterizing wandering BLACK HOLEs in Milky Way-type galaxiesAuthors: Julen Untzaga, Silvia Bonoli, David Izquierdo-Villalba, Mar Mezcua, Daniele Spinoso,Comments: Submitted to Monthly Notices of the Royal Astronomical Society, 13 pages, 9 figuresSubjects: astro-ph.GACreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
A population of non-stellar BLACK HOLEs ($\gtrsim$100 M$_{\odot}$) has been long predicted to wander the Milky Way. We aim to characterize this population by using the L-Galaxies semi-analytical model applied on top of the high resolution Millennium-II merger trees. Our results predict $\sim$10 wandering BLACK HOLEs with masses $\sim$2 $\times$ 10$^{3}$ M$_{\odot}$ in a typical $z$ = 0 Milky Way galaxy, accounting for $\sim$2$\%$ of the total non-stellar black hole mass budget of the galaxy. We find that the locations of these wanderers correlate with their formation scenario. While the ones concentrated at $\lesssim$1 kpc from the galactic nucleus on the disk come from past galactic mergers, the ones formed as a consequence of ejections due to gravitational recoils or the disruption of satellite galaxies are typically located at $\gtrsim$100 kpc. Such small and large distances might explain the absence of strong observational evidence for wandering BLACK HOLEs in the Milky Way. Our results also indicate that $\sim$67$\%$ of the wandering population is conformed by the leftovers of BLACK HOLE seeds that had little to no growth since their formation. We find that wandering BLACK HOLEs that are leftover seeds become wanderers at an earlier time with respect to grown seeds, and also come from more metal-poor galaxies. Finally, we show that the number of wandering BLACK HOLEs in a Milky Way-type galaxy depends on the seeding efficiency.
[abstract 38 / 38] (score: 1) - Title: CRIRES$^+$ transmission spectroscopy of WASP-127b. Detection of the resolved signatures of a supersonic equatorial JET and cool poles in a hot planetAuthors: L. Nortmann, F. Lesjak, F. Yan, D. Cont, S. Czesla, A. Lavail, A. D. Rains, E. Nagel, L. Boldt-Christmas, A. Hatzes, A. Reiners, N. Piskunov, O. Kochukhov, U. Heiter, D. Shulyak, M. Renge, U. Seemann,Comments: 18 pages 13 figures, submitted to Astronomy & Astrophysics (A&A)Subjects: astro-ph.EPCreated: 2024-04-18; Updated: ; Datestamp: 2024-04-19
General circulation models of gas giant exoplanets predict equatorial JETs that drive inhomogeneities across the planetary atmosphere. We studied the transmission spectrum of the hot Jupiter WASP-127b during one transit in the K band with CRIRES+. Telluric and stellar signals were removed from the data using SYSREM and the planetary signal was investigated using the cross-correlation (CCF) technique. After detecting a spectral signal indicative of atmospheric inhomogeneities, we employed a Bayesian retrieval framework with a 2D modelling approach tailored to address this scenario. We detected strong signals of H$_2$O and CO, which exhibited not one but two distinct CCF peaks. The double peaked signal can be explained by a supersonic equatorial JET and muted signals at the poles, with the two peaks representing the signals from the planet's morning and evening terminators, respectively. We calculated an equatorial JET velocity of $7.7\pm0.2$km/s from our retrieved overall equatorial velocity and the planet's tidally locked rotation, and derive distinct atmospheric properties for the two terminators as well as the polar region. The evening terminator is found to be hotter than the morning terminator by $175^{+116}_{-133}$K and the muted signals from the poles can be explained by significantly lower temperatures or a high cloud deck. Our retrieval yields a solar C/O ratio and metallicity and challenges previous studies of WASP-127b's atmosphere. The presence of a double peaked signal highlights the importance of accounting for planetary 3D structure during interpretation of atmospheric signals. The measured supersonic JET velocity and the lack of signal from the polar regions, representing a detection of latitudinal inhomogeneity in a spatially unresolved target, showcases the power of high-resolution transmission spectroscopy for the characterization of global circulation in exoplanets.
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arXiv:2404.12200 [pdf, ps, other]
arXiv:2404.12301 [pdf, ps, other]
arXiv:2404.12354 [pdf, ps, other]
arXiv:2404.12363 [pdf, ps, other]