Rahul Sharma, Manoj Mandal, Sabyasachi Pal, Biswajit Paul, G. K. Jaisawal, Ajay Ratheesh
The Be/X-ray binary pulsar RX J0440.9+4431 went through a giant outburst in December 2022 with a peak flux of $sim$2.3 Crab in 15--50 keV. We studied the broad-band timing and spectral properties of RX J0440.9+4431 using four $AstroSat$ observations, where the source transited between subcritical and supercritical accretion regimes. Pulsations were detected significantly above 100 keV. The pulse profiles were found to be highly luminosity- and energy-dependent. A significant evolution in the pulse profile shape near the peak of the outburst indicates a possible change in the accretion mode and beaming patterns of RX J0440.9+4431. The rms pulsed fraction was luminosity- and energy-dependent, with a concave-like feature around 20--30 keV. The depth of this feature varied with luminosity, indicating changes in the accretion column height and proportion of reflected photons. The broad-band continuum spectra were best fitted with a two-component Comptonization model with a blackbody component or a two-blackbody component model with a thermal Comptonization component. A quasi-periodic oscillation at 60 mHz was detected at a luminosity of $2.6 times 10^{37}$ erg s$^{-1}$, which evolved into 42 mHz at $1.5 times 10^{37}$ erg s$^{-1}$. The QPO rms were found to be energy dependent with an overall increasing trend with energy. For the first time, we found the QPO frequency varying with photon energy in an X-ray pulsar, which poses a challenge in explaining the QPO with current models such as the Keplarian and beat frequency model. Hence, more physically motivated models are required to understand the physical mechanism behind the mHz QPOs.
{"title":"Probing the energy and luminosity-dependent spectro-timing properties of RX J0440.9+4431 with AstroSat","authors":"Rahul Sharma, Manoj Mandal, Sabyasachi Pal, Biswajit Paul, G. K. Jaisawal, Ajay Ratheesh","doi":"arxiv-2409.11121","DOIUrl":"https://doi.org/arxiv-2409.11121","url":null,"abstract":"The Be/X-ray binary pulsar RX J0440.9+4431 went through a giant outburst in\u0000December 2022 with a peak flux of $sim$2.3 Crab in 15--50 keV. We studied the\u0000broad-band timing and spectral properties of RX J0440.9+4431 using four\u0000$AstroSat$ observations, where the source transited between subcritical and\u0000supercritical accretion regimes. Pulsations were detected significantly above\u0000100 keV. The pulse profiles were found to be highly luminosity- and\u0000energy-dependent. A significant evolution in the pulse profile shape near the\u0000peak of the outburst indicates a possible change in the accretion mode and\u0000beaming patterns of RX J0440.9+4431. The rms pulsed fraction was luminosity-\u0000and energy-dependent, with a concave-like feature around 20--30 keV. The depth\u0000of this feature varied with luminosity, indicating changes in the accretion\u0000column height and proportion of reflected photons. The broad-band continuum\u0000spectra were best fitted with a two-component Comptonization model with a\u0000blackbody component or a two-blackbody component model with a thermal\u0000Comptonization component. A quasi-periodic oscillation at 60 mHz was detected\u0000at a luminosity of $2.6 times 10^{37}$ erg s$^{-1}$, which evolved into 42 mHz\u0000at $1.5 times 10^{37}$ erg s$^{-1}$. The QPO rms were found to be energy\u0000dependent with an overall increasing trend with energy. For the first time, we\u0000found the QPO frequency varying with photon energy in an X-ray pulsar, which\u0000poses a challenge in explaining the QPO with current models such as the\u0000Keplarian and beat frequency model. Hence, more physically motivated models are\u0000required to understand the physical mechanism behind the mHz QPOs.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kayhan Gültekin, Karl Gebhardt, John Kormendy, Adi Foord, Ralf Bender, Tod R. Lauer, Jason Pinkney, Douglas O. Richstone, Scott Tremaine
We present IR photometry and HST imaging and spectroscopy of Sab galaxy NGC 4826. Schwarzschild dynamical modeling is used to measure its central black hole mass $M$. Photometric decomposition is used to enable a comparison of $M$ to published scaling relations between black hole masses and properties of host bulges. This decomposition implies that NGC 4826 contains classical and pseudo bulges of approximately equal mass. The classical bulge has best-fit S'ersic index $n=3.27$. The pseudobulge is made up of three parts, an inner lens ($n=0.18$ at $rlesssim4^{primeprime}$), an outer lens ($n=0.17$ at $r lesssim 45^{primeprime}$), and a $n=0.58$ component required to match the surface brightness between the lens components. The total $V$-band luminosity of the galaxy is $M_{VT}=-21.07$, the ratio of classical bulge to total light is $B/Tsimeq0.12$, and the ratio of pseudobulge to total light is $PB/Tsimeq0.13$. The outer disk is exponential ($n=1.07$) and makes up $D/T=0.75$ of the light of the galaxy. Our best-fit Schwarzschild model has a black hole mass with $1sigma$ uncertainties of $M=8.4^{+1.7}_{-0.6}times10^6 M_odot$ and a stellar $K$-band mass-to-light ratio of $Upsilon_K=0.46pm0.03 M_{odot} mathrm{L}_{odot}^{-1}$ at the assumed distance of 7.27 Mpc. Our modeling is marginally consistent with $M=0$ at the $3sigma$ limit. These best-fit parameters were calculated assuming the black hole is located where the velocity dispersion is largest; this is offset from the maximum surface brightness, probably because of dust absorption. The black hole mass -- one of the smallest measured by modeling stellar dynamics -- satisfies the well known correlations of $M$ with the $K$-band luminosity, stellar mass, and velocity dispersion of the classical bulge only in contrast to total (classical plus pseudo) bulge luminosity.
我们展示了 Sab 星系 NGC4826 的红外测光和 HST 成像与光谱。我们利用施瓦兹柴尔德动力学模型来测量其中心黑洞质量$M$。通过光度分解，可以将$M$与已公布的黑洞质量和宿主星系性质之间的比例关系进行比较。这种分解方法意味着 NGC 4826 包含质量大致相同的经典隆起和伪隆起。经典隆起的最佳拟合S/'ersic指数为$n=3.27$。伪凸起由三部分组成，一个内透镜（$n=0.18$，rlesssim4^{primeprime}$），一个外透镜（$n=0.17$，rlesssim 45^{primeprime}$），以及一个$n=0.58$的部分，用来匹配透镜部分之间的表面亮度。星系的总$V$波段光度为$M_{VT}=-21.07$，经典隆起与总光度的比值为$B/T（simeq0.12$），伪隆起与总光度的比值为$PB/T（simeq0.13$）。外圆盘是指数型的（$n=1.07$），占星系光量的$D/T=0.75$。我们的最佳拟合施瓦兹柴尔德模型的黑洞质量（1sigma$不确定度）为$M=8.4^{+1.7}_{-0.6}times10^6M_odot$，恒星的$K$波段质量光比为$Upsilon_K=0.46pm0.03M_{odot}mathrm{L}_{odot}^{-1}$，假定距离为7.27 Mpc。我们的模型在3sigma$极限下与$M=0$略微一致。这些最佳拟合参数是假设黑洞位于速度弥散最大的地方计算出来的；这与最大表面亮度有偏差，可能是因为尘埃的吸收。黑洞质量--通过恒星动力学建模测得的最小质量之一--满足众所周知的$M$与$K$波段光度、恒星质量和经典暴凸的速度色散之间的相关性，只是与总（经典加伪）暴凸光度不同。
{"title":"The Black Hole Mass and Photometric Components of NGC 4826","authors":"Kayhan Gültekin, Karl Gebhardt, John Kormendy, Adi Foord, Ralf Bender, Tod R. Lauer, Jason Pinkney, Douglas O. Richstone, Scott Tremaine","doi":"arxiv-2409.11575","DOIUrl":"https://doi.org/arxiv-2409.11575","url":null,"abstract":"We present IR photometry and HST imaging and spectroscopy of Sab galaxy NGC\u00004826. Schwarzschild dynamical modeling is used to measure its central black\u0000hole mass $M$. Photometric decomposition is used to enable a comparison of $M$\u0000to published scaling relations between black hole masses and properties of host\u0000bulges. This decomposition implies that NGC 4826 contains classical and pseudo\u0000bulges of approximately equal mass. The classical bulge has best-fit S'ersic\u0000index $n=3.27$. The pseudobulge is made up of three parts, an inner lens\u0000($n=0.18$ at $rlesssim4^{primeprime}$), an outer lens ($n=0.17$ at $r\u0000lesssim 45^{primeprime}$), and a $n=0.58$ component required to match the\u0000surface brightness between the lens components. The total $V$-band luminosity\u0000of the galaxy is $M_{VT}=-21.07$, the ratio of classical bulge to total light\u0000is $B/Tsimeq0.12$, and the ratio of pseudobulge to total light is\u0000$PB/Tsimeq0.13$. The outer disk is exponential ($n=1.07$) and makes up\u0000$D/T=0.75$ of the light of the galaxy. Our best-fit Schwarzschild model has a\u0000black hole mass with $1sigma$ uncertainties of $M=8.4^{+1.7}_{-0.6}times10^6\u0000M_odot$ and a stellar $K$-band mass-to-light ratio of $Upsilon_K=0.46pm0.03\u0000M_{odot} mathrm{L}_{odot}^{-1}$ at the assumed distance of 7.27 Mpc. Our\u0000modeling is marginally consistent with $M=0$ at the $3sigma$ limit. These\u0000best-fit parameters were calculated assuming the black hole is located where\u0000the velocity dispersion is largest; this is offset from the maximum surface\u0000brightness, probably because of dust absorption. The black hole mass -- one of\u0000the smallest measured by modeling stellar dynamics -- satisfies the well known\u0000correlations of $M$ with the $K$-band luminosity, stellar mass, and velocity\u0000dispersion of the classical bulge only in contrast to total (classical plus\u0000pseudo) bulge luminosity.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The recent observations by the James Webb Space Telescope (JWST) have revealed a larger number of bright galaxies at $zgtrsim10$ than was expected. The origin of this excess is still under debate, although several possibilities have been presented. We propose that gamma-ray bursts (GRBs) are a powerful probe to explore the origin of the excess and, hence, the star and galaxy formation histories in the early universe. Focusing on the recently launched mission, Einstein Probe (EP), we find that EP can detect several GRBs annually at $zgtrsim10$, assuming the GRB formation rate calibrated by events at $zlesssim6$ can be extrapolated. Interestingly, depending on the excess scenarios, the GRB event rate may also show an excess at $zsimeq10$, and its detection will help to discriminate between the scenarios that are otherwise difficult to distinguish. Additionally, we discuss that the puzzling, red-color, compact galaxies discovered by JWST, the so-called ``little red dots'', could host dark GRBs if they are dust-obscured star forming galaxies. We are eager for unbiased follow-up of GRBs and encourage future missions such as high-z GUNDAM to explore the early universe.
{"title":"Probing the Origin of the Star Formation Excess Discovered by JWST through Gamma-Ray Bursts","authors":"Tatsuya Matsumoto, Yuichi Harikane, Keiichi Maeda, Kunihito Ioka","doi":"arxiv-2409.11468","DOIUrl":"https://doi.org/arxiv-2409.11468","url":null,"abstract":"The recent observations by the James Webb Space Telescope (JWST) have\u0000revealed a larger number of bright galaxies at $zgtrsim10$ than was expected.\u0000The origin of this excess is still under debate, although several possibilities\u0000have been presented. We propose that gamma-ray bursts (GRBs) are a powerful\u0000probe to explore the origin of the excess and, hence, the star and galaxy\u0000formation histories in the early universe. Focusing on the recently launched\u0000mission, Einstein Probe (EP), we find that EP can detect several GRBs annually\u0000at $zgtrsim10$, assuming the GRB formation rate calibrated by events at\u0000$zlesssim6$ can be extrapolated. Interestingly, depending on the excess\u0000scenarios, the GRB event rate may also show an excess at $zsimeq10$, and its\u0000detection will help to discriminate between the scenarios that are otherwise\u0000difficult to distinguish. Additionally, we discuss that the puzzling,\u0000red-color, compact galaxies discovered by JWST, the so-called ``little red\u0000dots'', could host dark GRBs if they are dust-obscured star forming galaxies.\u0000We are eager for unbiased follow-up of GRBs and encourage future missions such\u0000as high-z GUNDAM to explore the early universe.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ealeal BearTechnion, Israel, Dmitry ShishkinTechnion, Israel, Noam SokerTechnion, Israel
We identify a point-symmetric morphology of three pairs of ears/clumps in the core-collapse supernova (CCSN) remnant (CCSNR) Puppis A, supporting the jittering jets explosion mechanism (JJEM). In the JJEM, the three pairs of jets that shaped the three pairs of ears/clumps in Puppis A are part of a large, about 10 to 30 pairs of jets that exploded Puppis A. Some similarities in morphological features between CCSNR Puppis A and three multipolar planetary nebulae considered to have been shaped by jets solidify the claim for shaping by jets. Puppis A has a prominent dipole structure, where one side is bright with a well-defined boundary, while the other is faint and defused. The neutron star (NS) remnant of Puppis A has a proper velocity, its natal kick velocity, in the opposite direction to the denser part of the dipole structure. We propose a new mechanism in the frame of the JJEM that imparts a natal kick to the NS, the kick-by-early asymmetrical pair (kick-BEAP) mechanism. At the early phase of the explosion process, the NS launches a pair of jets where one jet is much more energetic than the counter jet. The more energetic jet compresses a dense side to the CCSNR, and, by momentum conservation, the NS recoils in the opposite direction. Our study supports the JJEM as the primary explosion mechanism of CCSNe and enriches this explosion mechanism by introducing the novel kick-BEAP mechanism.
{"title":"The Puppis A supernova remnant: an early jet-driven neutron star kick followed by jittering jets","authors":"Ealeal BearTechnion, Israel, Dmitry ShishkinTechnion, Israel, Noam SokerTechnion, Israel","doi":"arxiv-2409.11453","DOIUrl":"https://doi.org/arxiv-2409.11453","url":null,"abstract":"We identify a point-symmetric morphology of three pairs of ears/clumps in the\u0000core-collapse supernova (CCSN) remnant (CCSNR) Puppis A, supporting the\u0000jittering jets explosion mechanism (JJEM). In the JJEM, the three pairs of jets\u0000that shaped the three pairs of ears/clumps in Puppis A are part of a large,\u0000about 10 to 30 pairs of jets that exploded Puppis A. Some similarities in\u0000morphological features between CCSNR Puppis A and three multipolar planetary\u0000nebulae considered to have been shaped by jets solidify the claim for shaping\u0000by jets. Puppis A has a prominent dipole structure, where one side is bright\u0000with a well-defined boundary, while the other is faint and defused. The neutron\u0000star (NS) remnant of Puppis A has a proper velocity, its natal kick velocity,\u0000in the opposite direction to the denser part of the dipole structure. We\u0000propose a new mechanism in the frame of the JJEM that imparts a natal kick to\u0000the NS, the kick-by-early asymmetrical pair (kick-BEAP) mechanism. At the early\u0000phase of the explosion process, the NS launches a pair of jets where one jet is\u0000much more energetic than the counter jet. The more energetic jet compresses a\u0000dense side to the CCSNR, and, by momentum conservation, the NS recoils in the\u0000opposite direction. Our study supports the JJEM as the primary explosion\u0000mechanism of CCSNe and enriches this explosion mechanism by introducing the\u0000novel kick-BEAP mechanism.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142269460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We study the observable spectral and temporal properties of kilonova remnants analytically, and showcase quantitative differences with respect to supernova remnants. We provide detection prospects of kilonova remnants in the context of ongoing radio surveys. We find that there is a good chance to expect 10s of such objects in future surveys with a flux threshold of $sim 0.1$ mJy. Kilonova remnants from a postulated population of long lived supramassive neutron star remnants of neutron star mergers are even more likely to be detected as they are extremely bright and peak earlier. For ongoing survey with threshold of $sim$ mJy, we expect to find 10-100s of such objects if they are a significant fraction of total kilonova population. Considering that there are no promising such kilonovae candidates in current surveys, we constrain the fraction of such extreme kilonova to be no more than 30 percent of the overall kilonovae rate, depending on the details of ejecta mass and external density distribution.
{"title":"Features and prospects for Kilonova remnant detection with current and future surveys","authors":"Sandeep Kumar Acharya, Paz Beniamini, Kenta Hotokezaka","doi":"arxiv-2409.11291","DOIUrl":"https://doi.org/arxiv-2409.11291","url":null,"abstract":"We study the observable spectral and temporal properties of kilonova remnants\u0000analytically, and showcase quantitative differences with respect to supernova\u0000remnants. We provide detection prospects of kilonova remnants in the context of\u0000ongoing radio surveys. We find that there is a good chance to expect 10s of\u0000such objects in future surveys with a flux threshold of $sim 0.1$ mJy.\u0000Kilonova remnants from a postulated population of long lived supramassive\u0000neutron star remnants of neutron star mergers are even more likely to be\u0000detected as they are extremely bright and peak earlier. For ongoing survey with\u0000threshold of $sim$ mJy, we expect to find 10-100s of such objects if they are\u0000a significant fraction of total kilonova population. Considering that there are\u0000no promising such kilonovae candidates in current surveys, we constrain the\u0000fraction of such extreme kilonova to be no more than 30 percent of the overall\u0000kilonovae rate, depending on the details of ejecta mass and external density\u0000distribution.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260100","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Joaquin Pelle, Carlos R. Argüelles, Florencia L. Vieyro, Valentina Crespi, Carolina Millauro, Martín F. Mestre, Oscar Reula, Federico Carrasco
Current images of the supermassive black hole (SMBH) candidates at the center of our Galaxy and M87 have opened an unprecedented era for studying strong gravity and the nature of relativistic sources. Very-long-baseline interferometry (VLBI) data show images consistent with a central SMBH within General Relativity (GR). However, it is essential to consider whether other well-motivated dark compact objects within GR could produce similar images. Recent studies have shown that dark matter (DM) halos modeled as self-gravitating systems of neutral fermions can harbor very dense fermionic cores at their centers, which can mimic the spacetime features of a black hole (BH). Such dense, horizonless DM cores can satisfy the observational constraints: they can be supermassive and compact and lack a hard surface. We investigate whether such cores can produce similar observational signatures to those of BHs when illuminated by an accretion disk. We compute images and spectra of the fermion cores with a general-relativistic ray tracing technique, assuming the radiation originates from standard $alpha$ disks, which are self-consistently solved within the current DM framework. Our simulated images possess a central brightness depression surrounded by a ring-like feature, resembling what is expected in the BH scenario. For Milky Way-like halos, the central brightness depressions have diameters down to $sim 35, mu$as as measured from a distance of approximately $8,$kpc. Finally, we show that the DM cores do not possess photon rings, a key difference from the BH paradigm, which could help discriminate between the models.
{"title":"Imaging fermionic dark matter cores at the center of galaxies","authors":"Joaquin Pelle, Carlos R. Argüelles, Florencia L. Vieyro, Valentina Crespi, Carolina Millauro, Martín F. Mestre, Oscar Reula, Federico Carrasco","doi":"arxiv-2409.11229","DOIUrl":"https://doi.org/arxiv-2409.11229","url":null,"abstract":"Current images of the supermassive black hole (SMBH) candidates at the center\u0000of our Galaxy and M87 have opened an unprecedented era for studying strong\u0000gravity and the nature of relativistic sources. Very-long-baseline\u0000interferometry (VLBI) data show images consistent with a central SMBH within\u0000General Relativity (GR). However, it is essential to consider whether other\u0000well-motivated dark compact objects within GR could produce similar images.\u0000Recent studies have shown that dark matter (DM) halos modeled as\u0000self-gravitating systems of neutral fermions can harbor very dense fermionic\u0000cores at their centers, which can mimic the spacetime features of a black hole\u0000(BH). Such dense, horizonless DM cores can satisfy the observational\u0000constraints: they can be supermassive and compact and lack a hard surface. We\u0000investigate whether such cores can produce similar observational signatures to\u0000those of BHs when illuminated by an accretion disk. We compute images and\u0000spectra of the fermion cores with a general-relativistic ray tracing technique,\u0000assuming the radiation originates from standard $alpha$ disks, which are\u0000self-consistently solved within the current DM framework. Our simulated images\u0000possess a central brightness depression surrounded by a ring-like feature,\u0000resembling what is expected in the BH scenario. For Milky Way-like halos, the\u0000central brightness depressions have diameters down to $sim 35, mu$as as\u0000measured from a distance of approximately $8,$kpc. Finally, we show that the\u0000DM cores do not possess photon rings, a key difference from the BH paradigm,\u0000which could help discriminate between the models.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260109","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Adaeze L. Ibik, Maria R. Drout, Bryan M. Gaensler, Paul Scholz, Navin Sridhar, Ben Margalit, Tracy E. Clarke, Shriharsh P. Tendulkar, Daniele Michilli, Tarraneh Eftekhari, Mohit Bhardwaj, Sarah Burke-Spolaor, Shami Chatterjee, Amanda M. Cook, Jason W. T. Hessels, Franz Kirsten, Ronniy C. Joseph, Victoria M. Kaspi, Mattias Lazda, Kiyoshi W. Masui, Kenzie Nimmo, Ayush Pandhi, Aaron B. Pearlman, Ziggy Pleunis, Masoud Rafiei-Ravandi, Kaitlyn Shin, Kendrick M. Smith
The identification of persistent radio sources (PRSs) coincident with two repeating fast radio bursts (FRBs) supports FRB theories requiring a compact central engine. However, deep non-detections in other cases highlight the diversity of repeating FRBs and their local environments. Here, we perform a systematic search for radio sources towards 37 CHIME/FRB repeaters using their arcminute localizations and a combination of archival surveys and targeted observations. Through multi-wavelength analysis of individual radio sources, we identify two (20181030A-S1 and 20190417A-S1) for which we disfavor an origin of either star formation or an active galactic nucleus in their host galaxies and thus consider them candidate PRSs. We do not find any associated PRSs for the majority of the repeating FRBs in our sample. For 8 FRB fields with Very Large Array imaging, we provide deep limits on the presence of PRSs that are 2--4 orders of magnitude fainter than the PRS associated with FRB,20121102A. Using Very Large Array Sky Survey imaging of all 37 fields, we constrain the rate of luminous ($gtrsim$10$^{40}$ erg s$^{-1}$) PRSs associated with repeating FRBs to be low. Within the context of FRB-PRS models, we find that 20181030A-S1 and 20190417A-S1 can be reasonably explained within the context of magnetar, hypernebulae, gamma-ray burst afterglow, or supernova ejecta models -- although we note that both sources follow the radio luminosity versus rotation measure relationship predicted in the nebula model framework. Future observations will be required to both further characterize and confirm the association of these PRS candidates with the FRBs.
{"title":"A search for persistent radio sources toward repeating fast radio bursts discovered by CHIME/FRB","authors":"Adaeze L. Ibik, Maria R. Drout, Bryan M. Gaensler, Paul Scholz, Navin Sridhar, Ben Margalit, Tracy E. Clarke, Shriharsh P. Tendulkar, Daniele Michilli, Tarraneh Eftekhari, Mohit Bhardwaj, Sarah Burke-Spolaor, Shami Chatterjee, Amanda M. Cook, Jason W. T. Hessels, Franz Kirsten, Ronniy C. Joseph, Victoria M. Kaspi, Mattias Lazda, Kiyoshi W. Masui, Kenzie Nimmo, Ayush Pandhi, Aaron B. Pearlman, Ziggy Pleunis, Masoud Rafiei-Ravandi, Kaitlyn Shin, Kendrick M. Smith","doi":"arxiv-2409.11533","DOIUrl":"https://doi.org/arxiv-2409.11533","url":null,"abstract":"The identification of persistent radio sources (PRSs) coincident with two\u0000repeating fast radio bursts (FRBs) supports FRB theories requiring a compact\u0000central engine. However, deep non-detections in other cases highlight the\u0000diversity of repeating FRBs and their local environments. Here, we perform a\u0000systematic search for radio sources towards 37 CHIME/FRB repeaters using their\u0000arcminute localizations and a combination of archival surveys and targeted\u0000observations. Through multi-wavelength analysis of individual radio sources, we\u0000identify two (20181030A-S1 and 20190417A-S1) for which we disfavor an origin of\u0000either star formation or an active galactic nucleus in their host galaxies and\u0000thus consider them candidate PRSs. We do not find any associated PRSs for the\u0000majority of the repeating FRBs in our sample. For 8 FRB fields with Very Large\u0000Array imaging, we provide deep limits on the presence of PRSs that are 2--4\u0000orders of magnitude fainter than the PRS associated with FRB,20121102A. Using\u0000Very Large Array Sky Survey imaging of all 37 fields, we constrain the rate of\u0000luminous ($gtrsim$10$^{40}$ erg s$^{-1}$) PRSs associated with repeating FRBs\u0000to be low. Within the context of FRB-PRS models, we find that 20181030A-S1 and\u000020190417A-S1 can be reasonably explained within the context of magnetar,\u0000hypernebulae, gamma-ray burst afterglow, or supernova ejecta models -- although\u0000we note that both sources follow the radio luminosity versus rotation measure\u0000relationship predicted in the nebula model framework. Future observations will\u0000be required to both further characterize and confirm the association of these\u0000PRS candidates with the FRBs.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"215 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alisa Galishnikova, Alexander Philippov, Eliot Quataert, Koushik Chatterjee, Matthew Liska
We study spherical accretion of magnetized plasma with low angular momentum onto a supermassive black hole, utilizing global General Relativistic Magnetohydrodynamic simulations. Black hole-driven feedback in the form of magnetic eruptions and jets triggers magnetized turbulence in the surrounding medium. We find that when the Bondi radius exceeds a certain value relative to the black hole's gravitational radius, this turbulence restricts the subsequent inflow of magnetic flux, strongly suppressing the strength of the jet. Consequently, magnetically arrested disks and powerful jets are not a generic outcome of accretion of magnetized plasma, even if there is an abundance of magnetic flux available in the system. However, if there is significant angular momentum in the inflowing gas, the eruption-driven turbulence is suppressed (sheared out), allowing for the presence of a powerful jet. Both the initially rotating and non-rotating flows go through periods of low and high gas angular momentum, showing that the angular momentum content of the inflowing gas is not just a feature of the ambient medium, but is strongly modified by the eruption and jet-driven black hole feedback. In the lower angular momentum states, our results predict that there should be dynamically strong magnetic fields on horizon scales, but no powerful jet; this state may be consistent with Sgr A* in the Galactic Center.
{"title":"Strongly magnetized accretion with low angular momentum produces a weak jet","authors":"Alisa Galishnikova, Alexander Philippov, Eliot Quataert, Koushik Chatterjee, Matthew Liska","doi":"arxiv-2409.11486","DOIUrl":"https://doi.org/arxiv-2409.11486","url":null,"abstract":"We study spherical accretion of magnetized plasma with low angular momentum\u0000onto a supermassive black hole, utilizing global General Relativistic\u0000Magnetohydrodynamic simulations. Black hole-driven feedback in the form of\u0000magnetic eruptions and jets triggers magnetized turbulence in the surrounding\u0000medium. We find that when the Bondi radius exceeds a certain value relative to\u0000the black hole's gravitational radius, this turbulence restricts the subsequent\u0000inflow of magnetic flux, strongly suppressing the strength of the jet.\u0000Consequently, magnetically arrested disks and powerful jets are not a generic\u0000outcome of accretion of magnetized plasma, even if there is an abundance of\u0000magnetic flux available in the system. However, if there is significant angular\u0000momentum in the inflowing gas, the eruption-driven turbulence is suppressed\u0000(sheared out), allowing for the presence of a powerful jet. Both the initially\u0000rotating and non-rotating flows go through periods of low and high gas angular\u0000momentum, showing that the angular momentum content of the inflowing gas is not\u0000just a feature of the ambient medium, but is strongly modified by the eruption\u0000and jet-driven black hole feedback. In the lower angular momentum states, our\u0000results predict that there should be dynamically strong magnetic fields on\u0000horizon scales, but no powerful jet; this state may be consistent with Sgr A*\u0000in the Galactic Center.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ruth M. E. Kelly, Denis González-Caniulef, Silvia Zane, Roberto Turolla, Roberto Taverna
Magnetars are neutron stars that host huge, complex magnetic fields which require supporting currents to flow along the closed field lines. This makes magnetar atmospheres different from those of passively cooling neutron stars because of the heat deposited by backflowing charges impinging on the star surface layers. This particle bombardment is expected to imprint the spectral and, even more, the polarisation properties of the emitted thermal radiation. We present solutions for the radiative transfer problem for bombarded plane-parallel atmospheres in the high magnetic field regime. The temperature profile is assumed a priori, and selected in such a way to reflect the varying rate of energy deposition in the slab (from the impinging currents and/or from the cooling crust). We find that thermal X-ray emission powered entirely by the energy released in the atmosphere by the magnetospheric back-bombardment is linearly polarised and X-mode dominated, but its polarisation degree is significantly reduced (down to $10-50%$) when compared with that expected from a standard atmosphere heated only from the cooling crust below. By increasing the fraction of heat flowing in from the crust the polarisation degree of the emergent radiation increases, first at higher energies ($sim 10$ keV) and then in the entire soft X-ray band. We use our models inside a ray-tracing code to derive the expected emission properties as measured by a distant observer and compare our results with recent IXPE observations of magnetar sources.
{"title":"X-ray polarisation signatures in bombarded magnetar atmospheres","authors":"Ruth M. E. Kelly, Denis González-Caniulef, Silvia Zane, Roberto Turolla, Roberto Taverna","doi":"arxiv-2409.11523","DOIUrl":"https://doi.org/arxiv-2409.11523","url":null,"abstract":"Magnetars are neutron stars that host huge, complex magnetic fields which\u0000require supporting currents to flow along the closed field lines. This makes\u0000magnetar atmospheres different from those of passively cooling neutron stars\u0000because of the heat deposited by backflowing charges impinging on the star\u0000surface layers. This particle bombardment is expected to imprint the spectral\u0000and, even more, the polarisation properties of the emitted thermal radiation.\u0000We present solutions for the radiative transfer problem for bombarded\u0000plane-parallel atmospheres in the high magnetic field regime. The temperature\u0000profile is assumed a priori, and selected in such a way to reflect the varying\u0000rate of energy deposition in the slab (from the impinging currents and/or from\u0000the cooling crust). We find that thermal X-ray emission powered entirely by the\u0000energy released in the atmosphere by the magnetospheric back-bombardment is\u0000linearly polarised and X-mode dominated, but its polarisation degree is\u0000significantly reduced (down to $10-50%$) when compared with that expected from\u0000a standard atmosphere heated only from the cooling crust below. By increasing\u0000the fraction of heat flowing in from the crust the polarisation degree of the\u0000emergent radiation increases, first at higher energies ($sim 10$ keV) and then\u0000in the entire soft X-ray band. We use our models inside a ray-tracing code to\u0000derive the expected emission properties as measured by a distant observer and\u0000compare our results with recent IXPE observations of magnetar sources.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pulsars are rotating neutron stars that are observed to be slowing down, implying a loss of their kinetic energy. There can be several different physical mechanisms involved in their spin-down process. The properties of fast-rotating pulsars depend on the nature of the neutron star matter, which can also affect the spin-down mechanisms. In this work, we examine three different physical phenomena contributing to the spin-down: magnetic dipole radiation, gravitational mass quadrupole radiation due to the ``mountain" formation, gravitational mass current quadrupole radiation or the r-modes, and calculate the expressions for the braking indices due to all of them. We have also considered jointly the implications of the uncertainties of the equation of the state of neutron star matter and rapid rotation on the braking indices corresponding to the aforementioned processes and their combinations. In all cases, the rapid rotation results in a departure from the standard values in the literature for the braking index when the rotational effects are ignored. If generated with a saturation amplitude within the range of $10^{-4} - 10^{-1}$, the r-mode oscillations dominate the spin-down of millisecond pulsars. We also explore the braking index in the context of millisecond magnetars. This study examines two braking index measurements in the context of newly born millisecond magnetars from two observed short $gamma$-ray bursts. The measured braking indices for these objects are consistent with our estimation, which allows us to conclude that the spin frequency of the remnants is within the range of $sim 550-850$ Hz.
{"title":"Structural response of neutron stars to rapid rotation and its impact on the braking index","authors":"Avishek Basu, Prasanta Char, Rana Nandi","doi":"arxiv-2409.11558","DOIUrl":"https://doi.org/arxiv-2409.11558","url":null,"abstract":"Pulsars are rotating neutron stars that are observed to be slowing down,\u0000implying a loss of their kinetic energy. There can be several different\u0000physical mechanisms involved in their spin-down process. The properties of\u0000fast-rotating pulsars depend on the nature of the neutron star matter, which\u0000can also affect the spin-down mechanisms. In this work, we examine three\u0000different physical phenomena contributing to the spin-down: magnetic dipole\u0000radiation, gravitational mass quadrupole radiation due to the ``mountain\"\u0000formation, gravitational mass current quadrupole radiation or the r-modes, and\u0000calculate the expressions for the braking indices due to all of them. We have\u0000also considered jointly the implications of the uncertainties of the equation\u0000of the state of neutron star matter and rapid rotation on the braking indices\u0000corresponding to the aforementioned processes and their combinations. In all\u0000cases, the rapid rotation results in a departure from the standard values in\u0000the literature for the braking index when the rotational effects are ignored.\u0000If generated with a saturation amplitude within the range of $10^{-4} -\u000010^{-1}$, the r-mode oscillations dominate the spin-down of millisecond\u0000pulsars. We also explore the braking index in the context of millisecond\u0000magnetars. This study examines two braking index measurements in the context of\u0000newly born millisecond magnetars from two observed short $gamma$-ray bursts.\u0000The measured braking indices for these objects are consistent with our\u0000estimation, which allows us to conclude that the spin frequency of the remnants\u0000is within the range of $sim 550-850$ Hz.","PeriodicalId":501343,"journal":{"name":"arXiv - PHYS - High Energy Astrophysical Phenomena","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142260072","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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