Merging supermassive black hole binaries produce low frequency gravitational waves which pulsar timing experiments are searching for. Much of the current theory is developed within the plane-wave formalism, and here we develop the more general Fresnel formalism. We show that Fresnel corrections to gravitational wave timing residual models allow novel new measurements to be made, such as direct measurements of the source distance from the timing residual phase and frequency, as well as direct measurements of chirp mass from a monochromatic source. Probing the Fresnel corrections in these models will require that future pulsar timing arrays include more distant pulsars across our galaxy, and greatly decrease the uncertainty on these pulsar distances (to within the order of the gravitational wavelength). However, we find that with these conditions met the measured source distance uncertainty can be made less than 10 per cent of the distance to the source for sources out to $sim 100$ Mpc, source sky localization can be reduced to sub-arcminute precision, and source volume localization can be made to less than $1 text{Mpc}^3$ for sources out to $1$ Gpc distances.
{"title":"Fresnel models for gravitational wave effects on pulsar timing","authors":"C. McGrath, J. Creighton","doi":"10.1093/mnras/stab1417","DOIUrl":"https://doi.org/10.1093/mnras/stab1417","url":null,"abstract":"Merging supermassive black hole binaries produce low frequency gravitational waves which pulsar timing experiments are searching for. Much of the current theory is developed within the plane-wave formalism, and here we develop the more general Fresnel formalism. We show that Fresnel corrections to gravitational wave timing residual models allow novel new measurements to be made, such as direct measurements of the source distance from the timing residual phase and frequency, as well as direct measurements of chirp mass from a monochromatic source. Probing the Fresnel corrections in these models will require that future pulsar timing arrays include more distant pulsars across our galaxy, and greatly decrease the uncertainty on these pulsar distances (to within the order of the gravitational wavelength). However, we find that with these conditions met the measured source distance uncertainty can be made less than 10 per cent of the distance to the source for sources out to $sim 100$ Mpc, source sky localization can be reduced to sub-arcminute precision, and source volume localization can be made to less than $1 text{Mpc}^3$ for sources out to $1$ Gpc distances.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76584285","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 modelled the Chandra and RXTE X-ray spectra of the massive binary WR 140 in the framework of the standard colliding stellar wind (CSW) picture. Models with partial electron heating at the shock fronts are a better representation of the X-ray data than those with complete temperature equalization. Emission measure of the X-ray plasma in the CSW region exhibits a considerable decrease at orbital phases near periastron. This is equivalent to variable effective mass-loss rates over the binary orbit. At orbital phases near periastron, a considerable X-ray absorption in excess to that from the stellar winds in WR 140 is present. The standard CSW model provides line profiles that in general do not match well the observed line profiles of the strong line features in the X-ray spectrum of WR 140. The variable effective mass-loss rate could be understood qualitatively in CSW picture of clumpy stellar winds where clumps are efficiently dissolved in the CSW region near apastron but not at periastron. However, future development of CSW models with non-spherically-symmetric stellar winds might be needed to get a better correspondence between theory and observations.
{"title":"Colliding stellar wind modelling of the X-ray emission from WR 140","authors":"S. Zhekov","doi":"10.1093/mnras/staa3591","DOIUrl":"https://doi.org/10.1093/mnras/staa3591","url":null,"abstract":"We modelled the Chandra and RXTE X-ray spectra of the massive binary WR 140 in the framework of the standard colliding stellar wind (CSW) picture. Models with partial electron heating at the shock fronts are a better representation of the X-ray data than those with complete temperature equalization. Emission measure of the X-ray plasma in the CSW region exhibits a considerable decrease at orbital phases near periastron. This is equivalent to variable effective mass-loss rates over the binary orbit. At orbital phases near periastron, a considerable X-ray absorption in excess to that from the stellar winds in WR 140 is present. The standard CSW model provides line profiles that in general do not match well the observed line profiles of the strong line features in the X-ray spectrum of WR 140. The variable effective mass-loss rate could be understood qualitatively in CSW picture of clumpy stellar winds where clumps are efficiently dissolved in the CSW region near apastron but not at periastron. However, future development of CSW models with non-spherically-symmetric stellar winds might be needed to get a better correspondence between theory and observations.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"24 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82025221","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 : 2020-11-13DOI: 10.1103/PhysRevD.103.083005
Leo Tsukada, R. Brito, W. East, Nils Siemonsen
Ultralight bosons, which are predicted in a variety of beyond-Standard-Model scenarios as dark-matter candidates, can trigger the superradiant instability around spinning black holes. This instability gives rise to oscillating boson condensates which then dissipate through the emission of nearly monochromatic gravitational waves. Such systems are promising sources for current and future gravitational-wave detectors. In this work, we consider minimally-coupled, massive vector bosons, which can produce a significantly stronger gravitational-wave signal compared to the scalar case. We adopt recently obtained numerical results for the gravitational-wave flux, and astrophysical models of black hole populations that include both isolated black holes and binary merger remnants, to compute and study in detail the stochastic gravitational-wave background emitted by these sources. Using a Bayesian framework, we search for such a background signal emitted using data from the first and second observing runs of Advanced LIGO. We find no evidence for such a signal. Therefore, the results allow us to constrain minimally coupled vector fields with masses in the range $0.8times10^{-13}mathrm{eV}leq m_bleq 6.0times10^{-13}mathrm{eV}$ at 95% credibility, assuming optimistically that the dimensionless spin distribution for the isolated black hole population is uniform in the range $[0,1]$. With more pessimistic assumptions, a narrower range around $m_bapprox 10^{-13}mathrm{eV}$ can still be excluded as long as the upper end of the uniform distribution for dimensionless black hole spin is $gtrsim 0.2$.
超轻玻色子被预测为各种超越标准模型的暗物质候选者，它可以引发旋转黑洞周围的超辐射不稳定性。这种不稳定性产生了振荡玻色子凝聚体，然后通过发射几乎单色的引力波而消散。这样的系统是当前和未来引力波探测器很有希望的来源。在这项工作中，我们考虑了最小耦合的大质量矢量玻色子，与标量情况相比，它可以产生更强的引力波信号。我们采用最近获得的引力波通量的数值结果，以及包括孤立黑洞和二元合并残余物在内的黑洞群体的天体物理模型，对这些源发射的随机引力波背景进行了详细的计算和研究。使用贝叶斯框架，我们使用高级LIGO第一次和第二次观测运行的数据来搜索这样的背景信号。我们没有发现这种信号存在的证据。因此，结果允许我们约束质量在$0.8times10^{-13}mathrm{eV}leq m_bleq 6.0times10^{-13}mathrm{eV}$范围内的最小耦合向量场% credibility, assuming optimistically that the dimensionless spin distribution for the isolated black hole population is uniform in the range $[0,1]$. With more pessimistic assumptions, a narrower range around $m_bapprox 10^{-13}mathrm{eV}$ can still be excluded as long as the upper end of the uniform distribution for dimensionless black hole spin is $gtrsim 0.2$.
{"title":"Modeling and searching for a stochastic gravitational-wave background from ultralight vector bosons","authors":"Leo Tsukada, R. Brito, W. East, Nils Siemonsen","doi":"10.1103/PhysRevD.103.083005","DOIUrl":"https://doi.org/10.1103/PhysRevD.103.083005","url":null,"abstract":"Ultralight bosons, which are predicted in a variety of beyond-Standard-Model scenarios as dark-matter candidates, can trigger the superradiant instability around spinning black holes. This instability gives rise to oscillating boson condensates which then dissipate through the emission of nearly monochromatic gravitational waves. Such systems are promising sources for current and future gravitational-wave detectors. In this work, we consider minimally-coupled, massive vector bosons, which can produce a significantly stronger gravitational-wave signal compared to the scalar case. We adopt recently obtained numerical results for the gravitational-wave flux, and astrophysical models of black hole populations that include both isolated black holes and binary merger remnants, to compute and study in detail the stochastic gravitational-wave background emitted by these sources. Using a Bayesian framework, we search for such a background signal emitted using data from the first and second observing runs of Advanced LIGO. We find no evidence for such a signal. Therefore, the results allow us to constrain minimally coupled vector fields with masses in the range $0.8times10^{-13}mathrm{eV}leq m_bleq 6.0times10^{-13}mathrm{eV}$ at 95% credibility, assuming optimistically that the dimensionless spin distribution for the isolated black hole population is uniform in the range $[0,1]$. With more pessimistic assumptions, a narrower range around $m_bapprox 10^{-13}mathrm{eV}$ can still be excluded as long as the upper end of the uniform distribution for dimensionless black hole spin is $gtrsim 0.2$.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76855857","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 hydrodynamics of an ultrarelativistic flow, enclosed by a strong shock wave, are described by the well known Blandford-McKee solutions in spherical geometry. These solutions, however, become inaccurate at a distance $sim R/2$ behind the shock wave, where $R$ is the shock radius, as the flow approaches Newtonian velocities. In this work we find a new self-similar solution which is an extension to the Blandford-McKee solutions, and which describes the interior part of the blast wave, where the flow reaches mildly relativistic to Newtonian velocities. We find that the velocity profile of the internal part of the flow does not depend on the value of the shock Lorentz factor, $Gamma$, and is accurate from $r=0$ down to a distance of $R/Gamma^2$ behind the shock. Despite the fact that the shock wave is in causal contact with the entire flow behind it, a singular point appears in the equations. Nevertheless, the solution is not required to pass through the singular point: for ambient density that decreases slowly enough, $rho propto r^{-k}$ with $k
{"title":"The non-relativistic interiors of ultra-relativistic explosions: Extension to the Blandford–McKee solutions","authors":"T. Faran, R. Sari","doi":"10.1063/5.0037299","DOIUrl":"https://doi.org/10.1063/5.0037299","url":null,"abstract":"The hydrodynamics of an ultrarelativistic flow, enclosed by a strong shock wave, are described by the well known Blandford-McKee solutions in spherical geometry. These solutions, however, become inaccurate at a distance $sim R/2$ behind the shock wave, where $R$ is the shock radius, as the flow approaches Newtonian velocities. In this work we find a new self-similar solution which is an extension to the Blandford-McKee solutions, and which describes the interior part of the blast wave, where the flow reaches mildly relativistic to Newtonian velocities. We find that the velocity profile of the internal part of the flow does not depend on the value of the shock Lorentz factor, $Gamma$, and is accurate from $r=0$ down to a distance of $R/Gamma^2$ behind the shock. Despite the fact that the shock wave is in causal contact with the entire flow behind it, a singular point appears in the equations. Nevertheless, the solution is not required to pass through the singular point: for ambient density that decreases slowly enough, $rho propto r^{-k}$ with $k<frac{1}{2}(5-sqrt{10})cong0.92$, a secondary shock wave forms with an inflow at the origin.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82167124","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 report results from the analysis of data from two observations of the accreting binary X-ray pulsar Cen X-3 carried out with the broadband X-ray observatories Suzaku and NuSTAR. The pulse profile is dominated by a broad single peak and show some energy dependence with two additional weak pulse peaks at energies below 15 and 25 keV respectively. The broadband X-ray spectrum for 0.8-60.0 keV for Suzaku and 3.0-60.0 keV for NuSTAR is fitted well with high energy cut-off power-law model along with soft-excess, multiple iron emission lines and a cyclotron absorption. The cyclotron line energy is found to be $30.29^{+0.68}_{-0.61}$ keV and $29.22^{+0.28}_{-0.27}$ keV respectively in the Suzaku and NuSTAR spectra. We make a comparison of these two measurements with four previous measurements of CRSF in Cen X-3 obtained with Ginga, BeppoSAX and RXTE. We find no evidence for a dependence of the CRSF on luminosity. Except for one CRSF measurement with BeppoSAX, the remaining measurements are consistent with a CRSF energy in the range of 29.5 - 30.0 keV over a luminosity range of 1.1-5.4 $times 10^{37}$ ergs s$^{-1}$ different from several other sources that show considerable CRSF variation in the same luminosity range.
{"title":"New measurements of the cyclotron line energy in Cen X-3","authors":"Gunjan Tomar, P. Pradhan, B. Paul","doi":"10.1093/mnras/staa3477","DOIUrl":"https://doi.org/10.1093/mnras/staa3477","url":null,"abstract":"We report results from the analysis of data from two observations of the accreting binary X-ray pulsar Cen X-3 carried out with the broadband X-ray observatories Suzaku and NuSTAR. The pulse profile is dominated by a broad single peak and show some energy dependence with two additional weak pulse peaks at energies below 15 and 25 keV respectively. The broadband X-ray spectrum for 0.8-60.0 keV for Suzaku and 3.0-60.0 keV for NuSTAR is fitted well with high energy cut-off power-law model along with soft-excess, multiple iron emission lines and a cyclotron absorption. The cyclotron line energy is found to be $30.29^{+0.68}_{-0.61}$ keV and $29.22^{+0.28}_{-0.27}$ keV respectively in the Suzaku and NuSTAR spectra. We make a comparison of these two measurements with four previous measurements of CRSF in Cen X-3 obtained with Ginga, BeppoSAX and RXTE. We find no evidence for a dependence of the CRSF on luminosity. Except for one CRSF measurement with BeppoSAX, the remaining measurements are consistent with a CRSF energy in the range of 29.5 - 30.0 keV over a luminosity range of 1.1-5.4 $times 10^{37}$ ergs s$^{-1}$ different from several other sources that show considerable CRSF variation in the same luminosity range.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"40 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80954858","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}
T. Morokuma, Y. Utsumi, K. Ohta, M. Yamanaka, K. Kawabata, Y. Inoue, Masaomi Tanaka, Michitoshi Yoshida, R. Itoh, M. Sasada, N. Tominaga, Hiroki Mori, M. Kawabata, T. Nakaoka, Maiko Chogi, T. Abe, Ruochen Huang, N. Kawahara, Hiroki Kimura, H. Nagashima, K. Takagi, Y. Yamazaki, Wei Liu, R. Ohsawa, S. Sako, K. Murata, K. Morihana, C. Gilligan, K. Isogai, M. Kimura, Yasuyuki Wakamatsu, Ryuhei Ohnishi, M. Takayama, S. Honda, Y. Matsuoka, T. Yamashita, S. Nagataki, Yasuyuki T. Tanaka
We present our follow-up observations to search for an electromagnetic counterpart of the IceCube high-energy neutrino, IceCube-170922A. Monitoring observations of a likely counterpart, TXS 0506+056, are also described. First, we quickly took optical and near-infrared images of 7 flat-spectrum radio sources within the IceCube error region right after the neutrino detection and found a rapid flux decline of TXS 0506+056 in Kanata/HONIR J-band data. Motivated by this discovery, intensive follow-up observations of TXS 0506+056 are continuously done, including our monitoring imaging observations, spectroscopic observations, and polarimetric observations in optical and near-infrared wavelengths. TXS 0506+056 shows a large amplitude (~1.0 mag) variability in a time scale of several days or longer, although no significant variability is detected in a time scale of a day or shorter. TXS 0506+056 also shows a bluer-when-brighter trend in optical and near-infrared wavelengths. Structure functions of variabilities are examined and indicate that TXS 0506+056 is not a special blazar in terms of optical variability. Polarization measurement results of TXS 0506+056 are also discussed.
{"title":"Follow-up observations for IceCube-170922A: Detection of rapid near-infrared variability and intensive monitoring of TXS 0506+056","authors":"T. Morokuma, Y. Utsumi, K. Ohta, M. Yamanaka, K. Kawabata, Y. Inoue, Masaomi Tanaka, Michitoshi Yoshida, R. Itoh, M. Sasada, N. Tominaga, Hiroki Mori, M. Kawabata, T. Nakaoka, Maiko Chogi, T. Abe, Ruochen Huang, N. Kawahara, Hiroki Kimura, H. Nagashima, K. Takagi, Y. Yamazaki, Wei Liu, R. Ohsawa, S. Sako, K. Murata, K. Morihana, C. Gilligan, K. Isogai, M. Kimura, Yasuyuki Wakamatsu, Ryuhei Ohnishi, M. Takayama, S. Honda, Y. Matsuoka, T. Yamashita, S. Nagataki, Yasuyuki T. Tanaka","doi":"10.1093/PASJ/PSAA110","DOIUrl":"https://doi.org/10.1093/PASJ/PSAA110","url":null,"abstract":"We present our follow-up observations to search for an electromagnetic counterpart of the IceCube high-energy neutrino, IceCube-170922A. Monitoring observations of a likely counterpart, TXS 0506+056, are also described. First, we quickly took optical and near-infrared images of 7 flat-spectrum radio sources within the IceCube error region right after the neutrino detection and found a rapid flux decline of TXS 0506+056 in Kanata/HONIR J-band data. Motivated by this discovery, intensive follow-up observations of TXS 0506+056 are continuously done, including our monitoring imaging observations, spectroscopic observations, and polarimetric observations in optical and near-infrared wavelengths. TXS 0506+056 shows a large amplitude (~1.0 mag) variability in a time scale of several days or longer, although no significant variability is detected in a time scale of a day or shorter. TXS 0506+056 also shows a bluer-when-brighter trend in optical and near-infrared wavelengths. Structure functions of variabilities are examined and indicate that TXS 0506+056 is not a special blazar in terms of optical variability. Polarization measurement results of TXS 0506+056 are also discussed.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88570502","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 nature of the intense X-ray emission from powerful extragalactic jets at large ($>1$ kpc) scale is still debated. The scenario that invokes the inverse Compton scattering of the CMB by electrons is challenged by the lack of gamma-ray emission in the GeV band. An alternative assumes synchrotron emission by a distinct population of ultra-high energy electrons. Here we present a concrete attempt to apply this scenario, exploring the specific model in which the ultra-high energy electrons are accelerated in a shear layer surrounding the jet. We limit the study to non-relativistic flows and particle acceleration is treated by a Fokker-Planck equation. The strict spatial coincidence between low energy (radio, optical) and X-ray emission prompts us to assume that the required population of pre-accelerated particles is provided by a shock responsible for the acceleration of the electrons emitting at low frequencies. We apply the model to the emission of the principal knots of the jets of PKS 0637-752 and PKS 1136-135, two of the best studied objects. For the set of fiducial parameters adopted, the condition that the jet power does not exceeds a limiting value of $10^{48}$ erg s$^{-1}$ constrains the magnetic field above $10$ $mu$G and indicates moderate beaming ($deltasimeq 2$) for PKS 0637-752. For both sources, the requirement that acceleration of the electrons proceeds faster than radiative cooling can be met if the magnetic turbulence in the shear layer follows a Kolmogorov spectrum, $I(k)propto k^{-q}$ with $q=5/3$, but cannot satisfied in the Bohm-like case ($q=1$).
{"title":"Constraining the shear acceleration model for the X-ray emission of large-scale extragalactic jets","authors":"F. Tavecchio","doi":"10.1093/mnras/staa4009","DOIUrl":"https://doi.org/10.1093/mnras/staa4009","url":null,"abstract":"The nature of the intense X-ray emission from powerful extragalactic jets at large ($>1$ kpc) scale is still debated. The scenario that invokes the inverse Compton scattering of the CMB by electrons is challenged by the lack of gamma-ray emission in the GeV band. An alternative assumes synchrotron emission by a distinct population of ultra-high energy electrons. Here we present a concrete attempt to apply this scenario, exploring the specific model in which the ultra-high energy electrons are accelerated in a shear layer surrounding the jet. We limit the study to non-relativistic flows and particle acceleration is treated by a Fokker-Planck equation. The strict spatial coincidence between low energy (radio, optical) and X-ray emission prompts us to assume that the required population of pre-accelerated particles is provided by a shock responsible for the acceleration of the electrons emitting at low frequencies. We apply the model to the emission of the principal knots of the jets of PKS 0637-752 and PKS 1136-135, two of the best studied objects. For the set of fiducial parameters adopted, the condition that the jet power does not exceeds a limiting value of $10^{48}$ erg s$^{-1}$ constrains the magnetic field above $10$ $mu$G and indicates moderate beaming ($deltasimeq 2$) for PKS 0637-752. For both sources, the requirement that acceleration of the electrons proceeds faster than radiative cooling can be met if the magnetic turbulence in the shear layer follows a Kolmogorov spectrum, $I(k)propto k^{-q}$ with $q=5/3$, but cannot satisfied in the Bohm-like case ($q=1$).","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74251376","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 : 2020-11-03DOI: 10.1051/0004-6361/202038566
A. Noutsos, G. Desvignes, M. Kramer, N. Wex, P. Freire, I. Stairs, M. Mclaughlin, R. Manchester, A. Possenti, M. Burgay, A. Lyne, R. Breton, B. Perera, R. Ferdman
The double pulsar (PSR J0737-3039A/B) provides some of the most stringent tests of general relativity (GR) and its alternatives. The success of this system in tests of GR is largely due to the high-precision, long-term timing of its recycled-pulsar member, pulsar A. On the other hand, pulsar B is a young pulsar that exhibits significant short-term and long-term timing variations due to the electromagnetic-wind interaction with its companion and geodetic precession. Improving pulsar B's timing precision is a key step towards improving the precision in a number of GR tests with PSR J0737-3039A/B. In this paper, red noise signatures in the timing of pulsar B are investigated using roughly a four-year time span, from 2004 to 2008, beyond which time the pulsar's radio beam precessed out of view ... The timing of pulsar B presented in this paper depends on the size of the pulsar's orbit, which was calculated from GR, in order to precisely account for orbital timing delays. Consequently, our timing cannot directly be used to test theories of gravity. However, our modelling of the beam shape and radial wind of pulsar B can indirectly aid future efforts to time this pulsar by constraining part of the additional red noise observed on top of the orbital delays. As such, we conclude that, in the idealised case of zero covariance between our model's parameters and those of the timing model, our model can bring about a factor 2.6 improvement on the measurement precision of the mass ratio, R = mA/mB, between the two pulsars: a theory-independent parameter, which is pivotal in tests of GR.
{"title":"Understanding and improving the timing of PSR J0737−3039B","authors":"A. Noutsos, G. Desvignes, M. Kramer, N. Wex, P. Freire, I. Stairs, M. Mclaughlin, R. Manchester, A. Possenti, M. Burgay, A. Lyne, R. Breton, B. Perera, R. Ferdman","doi":"10.1051/0004-6361/202038566","DOIUrl":"https://doi.org/10.1051/0004-6361/202038566","url":null,"abstract":"The double pulsar (PSR J0737-3039A/B) provides some of the most stringent tests of general relativity (GR) and its alternatives. The success of this system in tests of GR is largely due to the high-precision, long-term timing of its recycled-pulsar member, pulsar A. On the other hand, pulsar B is a young pulsar that exhibits significant short-term and long-term timing variations due to the electromagnetic-wind interaction with its companion and geodetic precession. Improving pulsar B's timing precision is a key step towards improving the precision in a number of GR tests with PSR J0737-3039A/B. In this paper, red noise signatures in the timing of pulsar B are investigated using roughly a four-year time span, from 2004 to 2008, beyond which time the pulsar's radio beam precessed out of view ... The timing of pulsar B presented in this paper depends on the size of the pulsar's orbit, which was calculated from GR, in order to precisely account for orbital timing delays. Consequently, our timing cannot directly be used to test theories of gravity. However, our modelling of the beam shape and radial wind of pulsar B can indirectly aid future efforts to time this pulsar by constraining part of the additional red noise observed on top of the orbital delays. As such, we conclude that, in the idealised case of zero covariance between our model's parameters and those of the timing model, our model can bring about a factor 2.6 improvement on the measurement precision of the mass ratio, R = mA/mB, between the two pulsars: a theory-independent parameter, which is pivotal in tests of GR.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80142781","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 : 2020-11-02DOI: 10.1103/PhysRevD.103.063042
J. Christian, J. Schaffner-Bielich
We investigate the implications of a hypothetical $2.5,mathrm{M_odot}$ neutron star in regard to the possibility of a strong phase transition to quark matter. We use equations of state (EoS) of varying stiffness provided by a parameterizable relativistic mean filed model transitioning in a first order phase transition to quark matter with a constant speed of sound. We find a strong connection between the discontinuity in energy density and the maximal mass generated by the EoS. We demonstrate, that high maximal masses cannot be realized for large discontinuities in energy density, which are necessary for visible twin stars, especially for soft EoSs. As a result twin stars and maximal masses of $M_{max}gtrsim2.2,M_odot$ are mutually exclusive.
{"title":"Supermassive neutron stars rule out twin stars","authors":"J. Christian, J. Schaffner-Bielich","doi":"10.1103/PhysRevD.103.063042","DOIUrl":"https://doi.org/10.1103/PhysRevD.103.063042","url":null,"abstract":"We investigate the implications of a hypothetical $2.5,mathrm{M_odot}$ neutron star in regard to the possibility of a strong phase transition to quark matter. We use equations of state (EoS) of varying stiffness provided by a parameterizable relativistic mean filed model transitioning in a first order phase transition to quark matter with a constant speed of sound. We find a strong connection between the discontinuity in energy density and the maximal mass generated by the EoS. We demonstrate, that high maximal masses cannot be realized for large discontinuities in energy density, which are necessary for visible twin stars, especially for soft EoSs. As a result twin stars and maximal masses of $M_{max}gtrsim2.2,M_odot$ are mutually exclusive.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86760768","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 : 2020-11-02DOI: 10.1103/PHYSREVD.103.083019
Hengrui Xing, Y. Levin, A. Gruzinov, A. Vilenkin
We consider the evolution of a cosmic string loop that is captured by a much more massive and compact black hole. We show that after several reconnections that produce ejections of smaller loops, the loop that remains bound to the black hole moves on a nearly-periodic non-self-intersecting trajectory, "the orbit". The orbit evolves due to an energy and angular momentum exchange between the loop and the spinning black hole. We show that such evolution is mathematically equivalent to a certain continuous deformation of an auxiliary closed curve in a 3-dimensional space; for zero black-hole spin this deformation is curve-shortening that has been extensively studied by mathematicians. The evolution features competing effects of loop growth by the superradiant extraction of the black-hole spin energy, and loop decay by the friction of the moving string against the horizon. A self-intersection of an auxiliary curve corresponds to a capture by the black hole of a new string segment and thus an addition of a new captured loop. Possible asymptotic states of such evolution are shown to be strong emitters of gravitational waves. Whether reconnections prevent reaching the asymptotic states remains to be explored. Additionally, the orbit's shape also evolves due to an emission of gravitational waves, and a recoil of the black hole that changes the orbit and likely leads to self-intersections. We argue that for a significant range of the dimensionless tension $mu$, string loops are captured by supermassive black holes at the centers of galaxies. This strongly motivates further study of interaction between string loops and black holes, especially the influence of this process on the black hole spindown and on the production of gravitational waves by strings created in galactic nuclei. We also discuss potential loop captures by primordial black holes.
{"title":"Spinning black holes as cosmic string factories","authors":"Hengrui Xing, Y. Levin, A. Gruzinov, A. Vilenkin","doi":"10.1103/PHYSREVD.103.083019","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.083019","url":null,"abstract":"We consider the evolution of a cosmic string loop that is captured by a much more massive and compact black hole. We show that after several reconnections that produce ejections of smaller loops, the loop that remains bound to the black hole moves on a nearly-periodic non-self-intersecting trajectory, \"the orbit\". The orbit evolves due to an energy and angular momentum exchange between the loop and the spinning black hole. We show that such evolution is mathematically equivalent to a certain continuous deformation of an auxiliary closed curve in a 3-dimensional space; for zero black-hole spin this deformation is curve-shortening that has been extensively studied by mathematicians. The evolution features competing effects of loop growth by the superradiant extraction of the black-hole spin energy, and loop decay by the friction of the moving string against the horizon. A self-intersection of an auxiliary curve corresponds to a capture by the black hole of a new string segment and thus an addition of a new captured loop. Possible asymptotic states of such evolution are shown to be strong emitters of gravitational waves. Whether reconnections prevent reaching the asymptotic states remains to be explored. Additionally, the orbit's shape also evolves due to an emission of gravitational waves, and a recoil of the black hole that changes the orbit and likely leads to self-intersections. \u0000We argue that for a significant range of the dimensionless tension $mu$, string loops are captured by supermassive black holes at the centers of galaxies. This strongly motivates further study of interaction between string loops and black holes, especially the influence of this process on the black hole spindown and on the production of gravitational waves by strings created in galactic nuclei. We also discuss potential loop captures by primordial black holes.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78150902","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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