We investigate with relativistic MHD simulations the dissipation physics of BL Lac jets, by studying the synchrotron polarization signatures of particles accelerated by the kink instability in a magnetically-dominated plasma column. The nonlinear stage of the kink instability generates current sheets, where particles can be efficiently accelerated via magnetic reconnection. We identify current sheets as regions where s = J d/B is above some predefined threshold (where B is the field strength, J the current density and d the grid scale), and assume that the particle injection efficiency scales as proportional to the square of the current. X-ray emitting particles have short cooling times, so they only probe the field geometry of their injection sites. In contrast, particles emitting in the optical band, which we follow self-consistently as they propagate away from their injection sites while cooling, sample a larger volume, and so they may be expected to produce different polarimetric signatures. We find that the degree of polarization is roughly the same between X-ray and optical bands, because even the optical-emitting particles do not travel far from the current sheet where they were injected, due to lack of sufficient kink-generated turbulence. The polarization angle shows a different temporal evolution between the two bands, due to the different regions probed by X-ray and optical emitting particles. In view of the upcoming IXPE satellite, our results can help constrain whether kink-induced reconnection (as opposed to shocks) can be the source of multi-wavelength emission from BL Lacs.
{"title":"Kink-driven magnetic reconnection in relativistic jets: consequences for X-ray polarimetry of BL Lacs","authors":"G. Bodo, Fabrizo Tavecchio, L. Sironi","doi":"10.1093/mnras/staa3620","DOIUrl":"https://doi.org/10.1093/mnras/staa3620","url":null,"abstract":"We investigate with relativistic MHD simulations the dissipation physics of BL Lac jets, by studying the synchrotron polarization signatures of particles accelerated by the kink instability in a magnetically-dominated plasma column. The nonlinear stage of the kink instability generates current sheets, where particles can be efficiently accelerated via magnetic reconnection. We identify current sheets as regions where s = J d/B is above some predefined threshold (where B is the field strength, J the current density and d the grid scale), and assume that the particle injection efficiency scales as proportional to the square of the current. X-ray emitting particles have short cooling times, so they only probe the field geometry of their injection sites. In contrast, particles emitting in the optical band, which we follow self-consistently as they propagate away from their injection sites while cooling, sample a larger volume, and so they may be expected to produce different polarimetric signatures. We find that the degree of polarization is roughly the same between X-ray and optical bands, because even the optical-emitting particles do not travel far from the current sheet where they were injected, due to lack of sufficient kink-generated turbulence. The polarization angle shows a different temporal evolution between the two bands, due to the different regions probed by X-ray and optical emitting particles. In view of the upcoming IXPE satellite, our results can help constrain whether kink-induced reconnection (as opposed to shocks) can be the source of multi-wavelength emission from BL Lacs.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"88 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77634625","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}
A. Mushtukov, V. Suleimanov, S. Tsygankov, S. Portegies Zwart
It has been recently discovered that the transition of X-ray pulsars to the low luminosity state ($Llesssim 10^{35},{rm erg,s^{-1}}$) is accompanied by a dramatic spectral changes. Namely, the typical power-law-like spectrum with high energy cutoff transforms into a two-component structure with a possible cyclotron absorption feature on top of it. It was proposed that these spectral characteristics can be explained qualitatively by the emission of cyclotron photons in the atmosphere of the neutron star caused by collisional excitation of electrons to upper Landau levels and further comptonization of the photons by electron gas. The latter is expected to be overheated in a thin top layer of the atmosphere. In this paper, we perform Monte Carlo simulations of the radiative transfer in the atmosphere of an accreting neutron star while accounting for a resonant scattering of polarized X-ray photons by thermally distributed electrons. The spectral shape is shown to be strongly polarization-dependent in soft X-rays ($lesssim 10,{rm keV}$) and near the cyclotron scattering feature. The results of our numerical simulations are tested against the observational data of X-ray pulsar A 0535+262 in the low luminosity state. We show that the spectral shape of the pulsar can be reproduced by the proposed theoretical model. The applications of the discovery to the observational studies of accreting neutron stars are discussed.
{"title":"Spectrum formation in X-ray pulsars at very low mass accretion rate: Monte Carlo approach","authors":"A. Mushtukov, V. Suleimanov, S. Tsygankov, S. Portegies Zwart","doi":"10.1093/MNRAS/STAB811","DOIUrl":"https://doi.org/10.1093/MNRAS/STAB811","url":null,"abstract":"It has been recently discovered that the transition of X-ray pulsars to the low luminosity state ($Llesssim 10^{35},{rm erg,s^{-1}}$) is accompanied by a dramatic spectral changes. Namely, the typical power-law-like spectrum with high energy cutoff transforms into a two-component structure with a possible cyclotron absorption feature on top of it. It was proposed that these spectral characteristics can be explained qualitatively by the emission of cyclotron photons in the atmosphere of the neutron star caused by collisional excitation of electrons to upper Landau levels and further comptonization of the photons by electron gas. The latter is expected to be overheated in a thin top layer of the atmosphere. In this paper, we perform Monte Carlo simulations of the radiative transfer in the atmosphere of an accreting neutron star while accounting for a resonant scattering of polarized X-ray photons by thermally distributed electrons. The spectral shape is shown to be strongly polarization-dependent in soft X-rays ($lesssim 10,{rm keV}$) and near the cyclotron scattering feature. The results of our numerical simulations are tested against the observational data of X-ray pulsar A 0535+262 in the low luminosity state. We show that the spectral shape of the pulsar can be reproduced by the proposed theoretical model. The applications of the discovery to the observational studies of accreting neutron stars are discussed.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"32 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78270545","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}
By assuming the formation of a black hole soon after the merger event of GW170817, Shibata et al. updated the constraints on the maximum mass ($M_textrm{max}$) of a stable neutron star within $lesssim$ 2.3 $M_{odot}$, but there is no solid evidence to rule out $M_textrm{max}>2.3~M_{odot}$ from the point of both microphysical and astrophysical views. In order to explain massive pulsars, it is naturally expected that the equation of state (EOS) would become stiffer beyond a specific density. In this paper, we consider the possibility of EOSs with $M_textrm{max}>2.3~M_{odot}$, investigating the stiffness and the transition density in a polytropic model. Two kinds of neutron stars are considered, i.e., normal neutron stars (the density vanishes on gravity-bound surface) and strange stars (a sharp density discontinuity on self-bound surface). The polytropic model has only two parameter inputs in both cases: ($rho_{rm t}$, $gamma$) for gravity-bound objects, while ($rho_{rm s}$, $gamma$) for self-bound ones, with $rho_{rm t}$ the transition density, $rho_{rm s}$ the surface density and $gamma$ the polytropic exponent. In the matter of $M_textrm{max}>2.3~M_{odot}$, it is found that the smallest $rho_{rm t}$ and $gamma$ should be $sim 0.50~rho_0$ and $sim 2.65$ for normal neutron stars, respectively, whereas for strange star, we have $gamma > 1.40$ if $rho_{rm s} > 1.0~rho_0$ and $rho_{rm s} < 1.58~rho_0$ if $gamma <2.0$ ($rho_0$ is the nuclear saturation density). These parametric results could guide further research of the real EOS with any foundation of microphysics if a pulsar mass higher than $2.3~M_{odot}$ is measured in the future. We also derive rough results of common neutron star radius range, which is $9.8~rm{km} < R_{1.4} < 13.8~rm{km}$ for normal neutron stars and $10.5~rm{km} < R_{1.4} < 12.5~rm{km}$ for strange stars.
{"title":"What if the neutron star maximum mass is beyond ∼2.3 M⊙?","authors":"Xuhao Wu, S. Du, Renxin Xu","doi":"10.1093/mnras/staa3145","DOIUrl":"https://doi.org/10.1093/mnras/staa3145","url":null,"abstract":"By assuming the formation of a black hole soon after the merger event of GW170817, Shibata et al. updated the constraints on the maximum mass ($M_textrm{max}$) of a stable neutron star within $lesssim$ 2.3 $M_{odot}$, but there is no solid evidence to rule out $M_textrm{max}>2.3~M_{odot}$ from the point of both microphysical and astrophysical views. In order to explain massive pulsars, it is naturally expected that the equation of state (EOS) would become stiffer beyond a specific density. In this paper, we consider the possibility of EOSs with $M_textrm{max}>2.3~M_{odot}$, investigating the stiffness and the transition density in a polytropic model. Two kinds of neutron stars are considered, i.e., normal neutron stars (the density vanishes on gravity-bound surface) and strange stars (a sharp density discontinuity on self-bound surface). The polytropic model has only two parameter inputs in both cases: ($rho_{rm t}$, $gamma$) for gravity-bound objects, while ($rho_{rm s}$, $gamma$) for self-bound ones, with $rho_{rm t}$ the transition density, $rho_{rm s}$ the surface density and $gamma$ the polytropic exponent. In the matter of $M_textrm{max}>2.3~M_{odot}$, it is found that the smallest $rho_{rm t}$ and $gamma$ should be $sim 0.50~rho_0$ and $sim 2.65$ for normal neutron stars, respectively, whereas for strange star, we have $gamma > 1.40$ if $rho_{rm s} > 1.0~rho_0$ and $rho_{rm s} < 1.58~rho_0$ if $gamma <2.0$ ($rho_0$ is the nuclear saturation density). These parametric results could guide further research of the real EOS with any foundation of microphysics if a pulsar mass higher than $2.3~M_{odot}$ is measured in the future. We also derive rough results of common neutron star radius range, which is $9.8~rm{km} < R_{1.4} < 13.8~rm{km}$ for normal neutron stars and $10.5~rm{km} < R_{1.4} < 12.5~rm{km}$ for strange stars.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83036985","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}
Pub Date : 2020-06-19DOI: 10.1051/0004-6361/202038165
J. Kajava, M. Giustini, R. Saxton, G. Miniutti
Stars that pass too close to a super-massive black hole may be disrupted by strong tidal forces. OGLE16aaa is one such tidal disruption event (TDE) which rapidly brightened and peaked in the optical/UV bands in early 2016 and subsequently decayed over the rest of the year. OGLE16aaa was detected in an XMM-Newton X-ray observation on June 9, 2016 with a flux slightly below the Swift/XRT upper limits obtained during the optical light curve peak. Between June 16-21, 2016, Swift/XRT also detected OGLE16aaa and based on the stacked spectrum, we could infer that the X-ray luminosity had jumped up by more than a factor of ten in just one week. No brightening signal was seen in the simultaneous optical/UV data to cause the X-ray luminosity to exceed the optical/UV one. A further XMM-Newton observation on November 30, 2016 showed that almost a year after the optical/UV peak, the X-ray emission was still at an elevated level, while the optical/UV flux decay had already leveled off to values comparable to those of the host galaxy. In all X-ray observations, the spectra were nicely modeled with a 50-70 eV thermal component with no intrinsic absorption, with a weak X-ray tail seen only in the November 30 XMM-Newton observation. The late-time X-ray behavior of OGLE16aaa strongly resembles the tidal disruption events ASASSN-15oi and AT2019azh. We were able to pinpoint the time delay between the initial optical TDE onset and the X-ray brightening to $182 pm 5$ days, which may possibly represent the timescale between the initial circularization of the disrupted star around the super-massive black hole and the subsequent delayed accretion. Alternatively, the delayed X-ray brightening could be related to a rapid clearing of a thick envelope that covers the central X-ray engine during the first six months.
{"title":"Rapid late-time X-ray brightening of the tidal disruption event OGLE16aaa","authors":"J. Kajava, M. Giustini, R. Saxton, G. Miniutti","doi":"10.1051/0004-6361/202038165","DOIUrl":"https://doi.org/10.1051/0004-6361/202038165","url":null,"abstract":"Stars that pass too close to a super-massive black hole may be disrupted by strong tidal forces. OGLE16aaa is one such tidal disruption event (TDE) which rapidly brightened and peaked in the optical/UV bands in early 2016 and subsequently decayed over the rest of the year. OGLE16aaa was detected in an XMM-Newton X-ray observation on June 9, 2016 with a flux slightly below the Swift/XRT upper limits obtained during the optical light curve peak. Between June 16-21, 2016, Swift/XRT also detected OGLE16aaa and based on the stacked spectrum, we could infer that the X-ray luminosity had jumped up by more than a factor of ten in just one week. No brightening signal was seen in the simultaneous optical/UV data to cause the X-ray luminosity to exceed the optical/UV one. A further XMM-Newton observation on November 30, 2016 showed that almost a year after the optical/UV peak, the X-ray emission was still at an elevated level, while the optical/UV flux decay had already leveled off to values comparable to those of the host galaxy. In all X-ray observations, the spectra were nicely modeled with a 50-70 eV thermal component with no intrinsic absorption, with a weak X-ray tail seen only in the November 30 XMM-Newton observation. The late-time X-ray behavior of OGLE16aaa strongly resembles the tidal disruption events ASASSN-15oi and AT2019azh. We were able to pinpoint the time delay between the initial optical TDE onset and the X-ray brightening to $182 pm 5$ days, which may possibly represent the timescale between the initial circularization of the disrupted star around the super-massive black hole and the subsequent delayed accretion. Alternatively, the delayed X-ray brightening could be related to a rapid clearing of a thick envelope that covers the central X-ray engine during the first six months.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74391920","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}
Blazars can be divided into two subtypes, flat spectrum radio quasars (FSRQs) and BL Lac objects, which have been distinguished phenomenologically by the strength of their optical emission lines, while their physical nature and relationship are still not fully understood. In this paper, we focus on the differences in their variability. We characterize the blazar variability using the Ornstein-Uhlenbeck (OU) process, and investigate the features that are discriminative for the two subtypes. We used optical photometric and polarimetric data obtained with the 1.5-m Kanata telescope for 2008-2014. We found that four features, namely the variation amplitude, characteristic timescale, and non-stationarity of the variability obtained from the light curves and the median of the degree of polarization (PD), are essential for distinguishing between FSRQs and BL Lac objects. FSRQs are characterized by rare and large flares, while the variability of BL Lac objects can be reproduced with a stationary OU process with relatively small amplitudes. The characteristics of the variability are governed not by the differences in the jet structure between the subtypes, but by the peak frequency of the synchrotron emission. This implies that the nature of the variation in the jets is common in FSRQs and BL Lac objects. We found that BL Lac objects tend to have high PD medians, which suggests that they have a stable polarization component. FSRQs have no such component, possibly because of a strong Compton cooling effect in sub-pc scale jets.
{"title":"Feature selection for classification of blazars based on optical photometric and polarimetric time-series data","authors":"M. Uemura, T. Abe, Yurika Yamada, Shiro Ikeda","doi":"10.1093/pasj/psaa063","DOIUrl":"https://doi.org/10.1093/pasj/psaa063","url":null,"abstract":"Blazars can be divided into two subtypes, flat spectrum radio quasars (FSRQs) and BL Lac objects, which have been distinguished phenomenologically by the strength of their optical emission lines, while their physical nature and relationship are still not fully understood. In this paper, we focus on the differences in their variability. We characterize the blazar variability using the Ornstein-Uhlenbeck (OU) process, and investigate the features that are discriminative for the two subtypes. We used optical photometric and polarimetric data obtained with the 1.5-m Kanata telescope for 2008-2014. We found that four features, namely the variation amplitude, characteristic timescale, and non-stationarity of the variability obtained from the light curves and the median of the degree of polarization (PD), are essential for distinguishing between FSRQs and BL Lac objects. FSRQs are characterized by rare and large flares, while the variability of BL Lac objects can be reproduced with a stationary OU process with relatively small amplitudes. The characteristics of the variability are governed not by the differences in the jet structure between the subtypes, but by the peak frequency of the synchrotron emission. This implies that the nature of the variation in the jets is common in FSRQs and BL Lac objects. We found that BL Lac objects tend to have high PD medians, which suggests that they have a stable polarization component. FSRQs have no such component, possibly because of a strong Compton cooling effect in sub-pc scale jets.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74671810","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}
Pub Date : 2020-06-07DOI: 10.4236/JMP.2020.1111111
Hujeirat, A.A, Samtaney
Our bimetric spacetime model of glitching pulsars is applied to the remnant of GW170817. Accordingly, pulsars are born with embryonic incompressible superconducting gluon-quark superfluid cores (SuSu-matter) that are embedded in Minkowski spacetime, whereas the ambient compressible and dissipative media (CDM) are imbedded in curved spacetime. As pulsars cool down, the equilibrium between both spacetime is altered, thereby triggering the well-observed glitch phenomena. Based thereon and assuming all neutron stars (NSs) to be born with the same initial mass of $M_{NS}(t=0) approx 1.25,mathcal{M}_{odot},$ we argue that the remnant of GW170817 should be a relatively faint NS with a hypermassive central core made of SuSu-matter. The effective mass and radius of the remnant are predicted to be $[2.8 mathcal{M}_{odot} < mathcal{M}_{rem} le 3.351 mathcal{M}_{odot}]$ and $R_{rem}=10.764$ km, whereas the mass of the enclosed SuSu-core is $mathcal{M}_{core}=1.7 mathcal{M}_{odot}.$ Here, about $1/2~ mathcal{M}_{core}$ is an energy enhancement triggered by the phase transition of the gluon-quark-plasma from the microscopic into macroscopic scale. The current compactness of the remnant is $alpha_c = 0.918,$ but predicted to increase as the CDM and cools down, rendering the remnant an invisible dark energy object, and therefore to an excellent black hole candidate.
{"title":"The Remnant of GW170817: A Trapped Neutron Star with a Massive Incompressible Superfluid Core","authors":"Hujeirat, A.A, Samtaney","doi":"10.4236/JMP.2020.1111111","DOIUrl":"https://doi.org/10.4236/JMP.2020.1111111","url":null,"abstract":"Our bimetric spacetime model of glitching pulsars is applied to the remnant of GW170817. Accordingly, pulsars are born with embryonic incompressible superconducting gluon-quark superfluid cores (SuSu-matter) that are embedded in Minkowski spacetime, whereas the ambient compressible and dissipative media (CDM) are imbedded in curved spacetime. As pulsars cool down, the equilibrium between both spacetime is altered, thereby triggering the well-observed glitch phenomena. \u0000Based thereon and assuming all neutron stars (NSs) to be born with the same initial mass of $M_{NS}(t=0) approx 1.25,mathcal{M}_{odot},$ we argue that the remnant of GW170817 should be a relatively faint NS with a hypermassive central core made of SuSu-matter. The effective mass and radius of the remnant are predicted to be $[2.8 mathcal{M}_{odot} < mathcal{M}_{rem} le 3.351 mathcal{M}_{odot}]$ and $R_{rem}=10.764$ km, whereas the mass of the enclosed SuSu-core is $mathcal{M}_{core}=1.7 mathcal{M}_{odot}.$ Here, about $1/2~ mathcal{M}_{core}$ is an energy enhancement triggered by the phase transition of the gluon-quark-plasma from the microscopic into macroscopic scale. \u0000The current compactness of the remnant is $alpha_c = 0.918,$ but predicted to increase as the CDM and cools down, rendering the remnant an invisible dark energy object, and therefore to an excellent black hole candidate.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81844016","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}
A. Jana, J.-R. Shang, D. Debnath, S. Chakrabarti, D. Chatterjee, Hsiang-Kuang Chang
The 2015 Outburst of V404 Cygni is an unusual one with several X-ray and radio flares and rapid variation in the spectral and timing properties. The outburst occurred after $26$ years of inactivity of the black hole. We study the accretion flow properties of the source during its initial phase of the outburst using {it Swift}/XRT and {it Swift}/BAT data in the energy range of $0.5-150$ keV. We have done spectral analysis with the two-component advective flow (TCAF) model fits file. Several flow parameters such as two types of accretion rates (Keplerian disk and sub-Keplerian halo), shock parameters (location and compression ratio) are extracted to understand the accretion flow dynamics. We calculated equipartition magnetic field $B$ for the outburst and found that the highest $B sim 900$~Gauss. Power density spectra (PDS) showed no break, which indicates no or very less contribution of the Keplerian disk component, which is also seen from the result of the spectral analysis. No signature of prominent quasi-periodic oscillations (QPOs) is observed in the PDS. This is due to the mismatch of the cooling timescale and infall timescale of the post-shock matter.
{"title":"Study of Accretion Flow Dynamics of V404 Cygni during Its 2015 Outburst","authors":"A. Jana, J.-R. Shang, D. Debnath, S. Chakrabarti, D. Chatterjee, Hsiang-Kuang Chang","doi":"10.3390/GALAXIES9020039","DOIUrl":"https://doi.org/10.3390/GALAXIES9020039","url":null,"abstract":"The 2015 Outburst of V404 Cygni is an unusual one with several X-ray and radio flares and rapid variation in the spectral and timing properties. The outburst occurred after $26$ years of inactivity of the black hole. We study the accretion flow properties of the source during its initial phase of the outburst using {it Swift}/XRT and {it Swift}/BAT data in the energy range of $0.5-150$ keV. We have done spectral analysis with the two-component advective flow (TCAF) model fits file. Several flow parameters such as two types of accretion rates (Keplerian disk and sub-Keplerian halo), shock parameters (location and compression ratio) are extracted to understand the accretion flow dynamics. We calculated equipartition magnetic field $B$ for the outburst and found that the highest $B sim 900$~Gauss. Power density spectra (PDS) showed no break, which indicates no or very less contribution of the Keplerian disk component, which is also seen from the result of the spectral analysis. No signature of prominent quasi-periodic oscillations (QPOs) is observed in the PDS. This is due to the mismatch of the cooling timescale and infall timescale of the post-shock matter.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86965852","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}
Abstract Blazar TXS 0506+056 is the main candidate for a coincident neutrino and gamma-ray flare event. In this paper, we compose a detailed kinetic lepto-hadronic emission model capable of producing a photon and neutrino spectrum given a set of parameters. Our model includes a range of large-scale geometries and both dynamical and steady-state injection models for electrons and protons. We link this model with a Markov Chain Monte Carlo sampler to obtain a powerful statistical tool that allows us to both fit the Spectral Energy Distribution and study the probability density functions and correlations of the parameters. Assuming a fiducial neutrino flux, we demonstrate how multi-messenger observations can be modelled jointly in a Bayesian framework. We find the best parameters for each of the variants of the model tested and report on their cross-correlations. Additionally, we confirm that reproducing the neutrino flux of TXS 0506+056 requires an extreme proton to electron ratio either in the local acceleration process or from external injection.
{"title":"A Bayesian approach to modelling multimessenger emission from blazars using lepto-hadronic kinetic equations","authors":"Bruno Jim'enez-Fern'andez, H. van Eerten","doi":"10.1093/mnras/staa3163","DOIUrl":"https://doi.org/10.1093/mnras/staa3163","url":null,"abstract":"Abstract Blazar TXS 0506+056 is the main candidate for a coincident neutrino and gamma-ray flare event. In this paper, we compose a detailed kinetic lepto-hadronic emission model capable of producing a photon and neutrino spectrum given a set of parameters. Our model includes a range of large-scale geometries and both dynamical and steady-state injection models for electrons and protons. We link this model with a Markov Chain Monte Carlo sampler to obtain a powerful statistical tool that allows us to both fit the Spectral Energy Distribution and study the probability density functions and correlations of the parameters. Assuming a fiducial neutrino flux, we demonstrate how multi-messenger observations can be modelled jointly in a Bayesian framework. We find the best parameters for each of the variants of the model tested and report on their cross-correlations. Additionally, we confirm that reproducing the neutrino flux of TXS 0506+056 requires an extreme proton to electron ratio either in the local acceleration process or from external injection.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87407510","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}
Recently, repeating fast radio bursts (FRBs) with a period of $P_{rm FRB}=16.35pm0.18$ days from FRB 180916.J0158+65 had been reported. It still remains controversial how to give rise to such a periodicity of this FRB. In this Letter, based on an assumption of a young pulsar surrounding by a debris disk, we attempt to diagnose whether the Lense-Thirring precession of the disk on the emitter can produce the observed periodicity. Our calculations indicate that the Lense-Thirring effect of a tilted disk can result in a precession period of 16 days for a mass inflow rate of $0.5-1.5times10^{18}~rm g,s^{-1}$, a spin period of 1-20 ms of the pulsar, and an extremely low viscous parameter $alpha=10^{-8}$ in the disk. The disk mass and the magnetic field of the pulsar are also constrained to be $sim10^{-3}~rm M_{odot}$ and $< 2.5times 10^{13}~rm G$. In our model, a new born pulsar with normal magnetic field and millisecond period would successively experience accretion phase, propeller phase, and is visible as a strong radio source in the current stage. The rotational energy of such a young NS can provide the observed radio bursting luminosity for $400$ years.
{"title":"Periodically repeating fast radio bursts: Lense–Thirring precession of a debris disk?","authors":"Wen-Cong Chen","doi":"10.1093/pasj/psaa060","DOIUrl":"https://doi.org/10.1093/pasj/psaa060","url":null,"abstract":"Recently, repeating fast radio bursts (FRBs) with a period of $P_{rm FRB}=16.35pm0.18$ days from FRB 180916.J0158+65 had been reported. It still remains controversial how to give rise to such a periodicity of this FRB. In this Letter, based on an assumption of a young pulsar surrounding by a debris disk, we attempt to diagnose whether the Lense-Thirring precession of the disk on the emitter can produce the observed periodicity. Our calculations indicate that the Lense-Thirring effect of a tilted disk can result in a precession period of 16 days for a mass inflow rate of $0.5-1.5times10^{18}~rm g,s^{-1}$, a spin period of 1-20 ms of the pulsar, and an extremely low viscous parameter $alpha=10^{-8}$ in the disk. The disk mass and the magnetic field of the pulsar are also constrained to be $sim10^{-3}~rm M_{odot}$ and $< 2.5times 10^{13}~rm G$. In our model, a new born pulsar with normal magnetic field and millisecond period would successively experience accretion phase, propeller phase, and is visible as a strong radio source in the current stage. The rotational energy of such a young NS can provide the observed radio bursting luminosity for $400$ years.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91362220","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}
S. Ide, K. Hayashida, H. Noda, Hiroyuki Kurubi, T. Yoneyama, Hironori Matsumoto Dept. of Earth, S. Science, O. Univ., Project Research Center, Isasjaxa
We report the serendipitous discovery of a transient X-ray source, Suzaku J1305$-$4930, $sim$3 kpc southwest of the nucleus of the Seyfert 2 galaxy NGC 4945. Among the seven Suzaku observations of NGC 4945 from 2005 to 2011, Suzaku J1305$-$4930 was detected four times in July and August in 2010. The X-ray spectra are better approximated with a multi-color disk model than a power-law model. At the first detection on 2010 July 4--5, its X-ray luminosity was $(8.9^{+0.2}_{-0.4}) times 10^{38}$ erg s$^{-1}$ and the temperature at the inner-disk radius ($kT_{rm in}$) was $1.12pm0.04$ keV. At the last detection with Suzaku on 2010 August 4--5, the luminosity decreased to $(2.2^{+0.3}_{-0.8}) times10^{38}$ erg s$^{-1}$ and $kT_{rm in}$ was $0.62pm0.07$ keV. The source was not detected on 2011 January 29, about six months after the first detection, with a luminosity upper limit of $2.4times10^{38}$ erg s$^{-1}$. We also find an absorption feature which is similar to that reported in Cyg X-1. Assuming the standard disk, we suggest that Suzaku J1305$-$4930 consists of a black hole with a mass of $sim$10 $M_{odot}$. The relation between the disk luminosity and $kT_{rm in}$ is not reproduced with the standard model of a constant inner radius but is better approximated with a slim-disk model.
{"title":"Discovery of a transient X-ray source Suzaku J1305−4930 in NGC 4945","authors":"S. Ide, K. Hayashida, H. Noda, Hiroyuki Kurubi, T. Yoneyama, Hironori Matsumoto Dept. of Earth, S. Science, O. Univ., Project Research Center, Isasjaxa","doi":"10.1093/pasj/psaa023","DOIUrl":"https://doi.org/10.1093/pasj/psaa023","url":null,"abstract":"We report the serendipitous discovery of a transient X-ray source, Suzaku J1305$-$4930, $sim$3 kpc southwest of the nucleus of the Seyfert 2 galaxy NGC 4945. Among the seven Suzaku observations of NGC 4945 from 2005 to 2011, Suzaku J1305$-$4930 was detected four times in July and August in 2010. The X-ray spectra are better approximated with a multi-color disk model than a power-law model. At the first detection on 2010 July 4--5, its X-ray luminosity was $(8.9^{+0.2}_{-0.4}) times 10^{38}$ erg s$^{-1}$ and the temperature at the inner-disk radius ($kT_{rm in}$) was $1.12pm0.04$ keV. At the last detection with Suzaku on 2010 August 4--5, the luminosity decreased to $(2.2^{+0.3}_{-0.8}) times10^{38}$ erg s$^{-1}$ and $kT_{rm in}$ was $0.62pm0.07$ keV. The source was not detected on 2011 January 29, about six months after the first detection, with a luminosity upper limit of $2.4times10^{38}$ erg s$^{-1}$. We also find an absorption feature which is similar to that reported in Cyg X-1. Assuming the standard disk, we suggest that Suzaku J1305$-$4930 consists of a black hole with a mass of $sim$10 $M_{odot}$. The relation between the disk luminosity and $kT_{rm in}$ is not reproduced with the standard model of a constant inner radius but is better approximated with a slim-disk model.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83021993","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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