The recent discovery of a fast radio burst (FRB 200428) from the Galactic magnetar SGR 1935+2154 robustly indicated that FRB phenomena can sometimes be produced by magnetars, although it is uncertain whether the cosmological FRBs can share the same origin with this Galactic event. The association of FRB 200428 with an X-ray burst (XRB) further offers important implications for the physical processes responsible for the FRB phenomena. By assuming that the XRB emission is produced in the magnetosphere of the magnetar, we investigate the possibility of that the FRB emission is produced by the synchrotron maser (SM) mechanism, which is powered by a shock due to the collision of an $e^{pm}$ ejecta with a baryonic cloud. It is found that this shock-powered SM model can in principle account for the FRB 200428 observations, if the collision just occurred on the line of sight and the ejecta lunched by magnetar bursts can have appropriate ingredients and structures. To be specific, a burst ejecta should consist of an ultra-relativistic and extremely highly collimated $e^{pm}$ component and a sub-relativistic and wide-spreading baryonic component. The cloud blocking the $e^{pm}$ ejecta is just a remnant of a previous baryonic ejecta. Meanwhile, as a result of the synchrotron emission of the shocked material, an intense millisecond X-ray pulse is predicted to overlap the magnetosphere XRB emission, which in principle provides a way to test the model. Additionally, the peak frequency of the SM radiation is constrained to be about a few hundred MHz and the radiation efficiency is around $10^{-4}$.
{"title":"The confrontation of the shock-powered synchrotron maser model with the Galactic FRB 200428","authors":"Yun-Wei Yu, Y. Zou, Z. Dai, Wenfei Yu","doi":"10.1093/mnras/staa3374","DOIUrl":"https://doi.org/10.1093/mnras/staa3374","url":null,"abstract":"The recent discovery of a fast radio burst (FRB 200428) from the Galactic magnetar SGR 1935+2154 robustly indicated that FRB phenomena can sometimes be produced by magnetars, although it is uncertain whether the cosmological FRBs can share the same origin with this Galactic event. The association of FRB 200428 with an X-ray burst (XRB) further offers important implications for the physical processes responsible for the FRB phenomena. By assuming that the XRB emission is produced in the magnetosphere of the magnetar, we investigate the possibility of that the FRB emission is produced by the synchrotron maser (SM) mechanism, which is powered by a shock due to the collision of an $e^{pm}$ ejecta with a baryonic cloud. It is found that this shock-powered SM model can in principle account for the FRB 200428 observations, if the collision just occurred on the line of sight and the ejecta lunched by magnetar bursts can have appropriate ingredients and structures. To be specific, a burst ejecta should consist of an ultra-relativistic and extremely highly collimated $e^{pm}$ component and a sub-relativistic and wide-spreading baryonic component. The cloud blocking the $e^{pm}$ ejecta is just a remnant of a previous baryonic ejecta. Meanwhile, as a result of the synchrotron emission of the shocked material, an intense millisecond X-ray pulse is predicted to overlap the magnetosphere XRB emission, which in principle provides a way to test the model. Additionally, the peak frequency of the SM radiation is constrained to be about a few hundred MHz and the radiation efficiency is around $10^{-4}$.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74207283","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 : 2020-05-29DOI: 10.1103/PHYSREVC.103.035806
Ashadul Halder, Shibaji Banerjee, S. Ghosh, S. Raha
The limiting mass is a significant characteristic for compact exotic stars including quark stars and can be expressed in terms of fundamental constants and the Bag constant. In the present work, using bag model description, maximum mass of a rotating quark star is found to depend on the rotational frequency apart from other fundamental parameters. The analytical results obtained agrees with the result of several relevant numerical estimates as well as observational evidences.
{"title":"Chandrasekhar limit for rotating quark stars","authors":"Ashadul Halder, Shibaji Banerjee, S. Ghosh, S. Raha","doi":"10.1103/PHYSREVC.103.035806","DOIUrl":"https://doi.org/10.1103/PHYSREVC.103.035806","url":null,"abstract":"The limiting mass is a significant characteristic for compact exotic stars including quark stars and can be expressed in terms of fundamental constants and the Bag constant. In the present work, using bag model description, maximum mass of a rotating quark star is found to depend on the rotational frequency apart from other fundamental parameters. The analytical results obtained agrees with the result of several relevant numerical estimates as well as observational evidences.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"109 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78066546","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}
K. Ohashi, H. Menjo, Y. Itow, T. Sako, K. Kasahara
The mass composition of ultra-high-energy cosmic rays is important for understanding their origin. Owing to our limited knowledge of the hadronic interaction, the interpretations of the mass composition from observations have several open problems, such as the inconsistent interpretations of $langle X_{mathrm{max}}rangle $ and $langle X_{mathrm{max}}^{mu}rangle $ and the large difference between the predictions by the hadronic interaction models. Diffractive collision is one of the proposed sources of the uncertainty. In this paper, we discuss the effect of the detailed characteristics of diffractive collisions on the observables of ultra-high-energy cosmic-ray experiments by focusing on three detailed characteristics. These are the cross-sectional fractions of different collision types, diffractive-mass spectrum, and diffractive-mass-dependent particle productions. We demonstrated that the current level of the uncertainty in the cross-sectional fraction can affect 8.9$mathrm{g/cm^2}$ of $langle X_{mathrm{max}}rangle $ and 9.4$mathrm{g/cm^2}$ of $langle X_{mathrm{max}}^{mu}rangle $, whereas the other details of the diffractive collisions exhibit relatively minor effects.
{"title":"Simulation study on the effects of diffractive collisions on the prediction of the observables in ultra-high-energy cosmic-ray experiments","authors":"K. Ohashi, H. Menjo, Y. Itow, T. Sako, K. Kasahara","doi":"10.1093/PTEP/PTAB013","DOIUrl":"https://doi.org/10.1093/PTEP/PTAB013","url":null,"abstract":"The mass composition of ultra-high-energy cosmic rays is important for understanding their origin. Owing to our limited knowledge of the hadronic interaction, the interpretations of the mass composition from observations have several open problems, such as the inconsistent interpretations of $langle X_{mathrm{max}}rangle $ and $langle X_{mathrm{max}}^{mu}rangle $ and the large difference between the predictions by the hadronic interaction models. Diffractive collision is one of the proposed sources of the uncertainty. In this paper, we discuss the effect of the detailed characteristics of diffractive collisions on the observables of ultra-high-energy cosmic-ray experiments by focusing on three detailed characteristics. These are the cross-sectional fractions of different collision types, diffractive-mass spectrum, and diffractive-mass-dependent particle productions. We demonstrated that the current level of the uncertainty in the cross-sectional fraction can affect 8.9$mathrm{g/cm^2}$ of $langle X_{mathrm{max}}rangle $ and 9.4$mathrm{g/cm^2}$ of $langle X_{mathrm{max}}^{mu}rangle $, whereas the other details of the diffractive collisions exhibit relatively minor effects.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"57 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83113181","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 : 2020-05-24DOI: 10.1051/0004-6361/202037580
Xiao-Na Sun, Rui-zhi Yang, Yun-Feng Liang, F. Peng, Hai-ming Zhang, Xiang-Yu Wang, F. Aharonian
We report the detection of high-energy gamma-ray signal towards the young star-forming region, W40. Using 10-year Pass 8 data from the Fermi Large Area Telescope (Fermi-LAT), we extracted an extended gamma-ray excess region with a significance of about 18sigma. The radiation has a spectrum with a photon index of 2.49 +/- 0.01. The spatial correlation with the ionized gas content favors the hadronic origin of the gamma-ray emission. The total cosmic-ray (CR) proton energy in the gamma-ray production region is estimated to be the order of 10^47 erg. However, this could be a small fraction of the total energy released in cosmic rays (CRs) by local accelerators, presumably by massive stars, over the lifetime of the system. If so, W40, together with earlier detections of gamma-rays from Cygnus cocoon, Westerlund 1, Westerlund 2, NGC 3603, and 30 Dor C, supports the hypothesis that young star clusters are effective CR factories. The unique aspect of this result is that the gamma-ray emission is detected, for the first time, from a stellar cluster itself, rather than from the surrounding "cocoons".
我们报告了对年轻恒星形成区域W40的高能伽马射线信号的探测。利用费米大面积望远镜(Fermi- lat) 10年的Pass 8数据，我们提取了一个显著性约为18sigma的扩展伽马射线过量区域。该辐射的光谱光子指数为2.49 +/- 0.01。与电离气体含量的空间相关性有利于伽玛射线发射的强子起源。伽玛射线产生区的总宇宙射线(CR)质子能量估计为10^47 erg数量级。然而，这可能只是局部加速器释放的宇宙射线(cr)总能量的一小部分，这些加速器可能是由大质量恒星在系统的生命周期中释放的。如果是这样的话，W40和早期从天鹅座茧、韦斯特隆德1号、韦斯特隆德2号、NGC 3603和30 Dor C探测到的伽马射线一起，支持了年轻星团是有效的CR工厂的假设。这个结果的独特之处在于，伽马射线的发射是第一次从一个星团本身，而不是从周围的“茧”中探测到的。
{"title":"Diffuse γ-ray emission toward the massive star-forming region, W40","authors":"Xiao-Na Sun, Rui-zhi Yang, Yun-Feng Liang, F. Peng, Hai-ming Zhang, Xiang-Yu Wang, F. Aharonian","doi":"10.1051/0004-6361/202037580","DOIUrl":"https://doi.org/10.1051/0004-6361/202037580","url":null,"abstract":"We report the detection of high-energy gamma-ray signal towards the young star-forming region, W40. Using 10-year Pass 8 data from the Fermi Large Area Telescope (Fermi-LAT), we extracted an extended gamma-ray excess region with a significance of about 18sigma. The radiation has a spectrum with a photon index of 2.49 +/- 0.01. The spatial correlation with the ionized gas content favors the hadronic origin of the gamma-ray emission. The total cosmic-ray (CR) proton energy in the gamma-ray production region is estimated to be the order of 10^47 erg. However, this could be a small fraction of the total energy released in cosmic rays (CRs) by local accelerators, presumably by massive stars, over the lifetime of the system. If so, W40, together with earlier detections of gamma-rays from Cygnus cocoon, Westerlund 1, Westerlund 2, NGC 3603, and 30 Dor C, supports the hypothesis that young star clusters are effective CR factories. The unique aspect of this result is that the gamma-ray emission is detected, for the first time, from a stellar cluster itself, rather than from the surrounding \"cocoons\".","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90643041","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 : 2020-05-22DOI: 10.21203/rs.3.rs-62191/v1
C.K. Li, Lin Lin, S. Xiong, M. Ge, X.B. Li, Tipei Li, F. Lu, S. Zhang, Y. Tuo, Y. Nang, B. Zhang, S. Xiao, Yao-Tseng Chen, L. Song, Y.P. Xu, C.Z. Liu, S. Jia, X. Cao, J. Qu, Shu Zhang, Y. Gu, J. Liao, X.F. Zhao, Y. Tan, J. Nie, H.S. Zhao, S. Zheng, Y.G. Zheng, Q. Luo, C. Cai, B. Li, W. Xue, Q. Bu, Z. Chang, G. Chen, T.X. Chen, Yu-Peng Chen, Yongwei Dong, Y.Y. Du, H. Gao, G. Gao, M. Gao, Y. Gu, J. Huo, D. Han, L.H. Jiang, Y. Huang, Weichun Jiang, J. Jin, L. Kong, Gang Li, J. Guan, M.S. Li, W. Li, X. Li, X. Li, Y.G. Li, Z.W. Li, X. Liang, B. Liu, H.W. Liu, X.J. Liu, B. Lu, X.F. Lu, T. Luo, X. Ma, B. Meng, G. Ou, N. Sai, X.Y. Song, L. Sun, L. Tao, J. Wang, G.F. Wang, W. Wang, Y. Wang, X. Wen, B.B. Wu, B.Y. Wu, M. Wu, G. Xiao, H. Xu, J. Yang, S. Yang, Yi-Jung Yang, Y. Yang, Q. Yi, Q. Yin, Y. You, C. Zhang, A. Zhang, F. Zhang, H.M. Zhang, J. Zhang, T. Zhang, Wei Zhang, W. Zhang, Y. Zhang, Yue Zhang, Y.F. Zhang, Y.J. Zhang, Z.L. Zhang, D. Zhou, Y. Zhu, Y.X. Zhu, L. Chen, W.Z. Zhang, Y.B. Chen, W. Cui, J.K. Deng
Fast radio bursts (FRBs) are short pulses observed in radio band from cosmological distances, some of which emit repeating bursts. The physical origins of these mysterious events have been subject to wide speculations and heated debates. One class of models invoke soft gamma-ray repeaters (SGRs), or magnetars, as the sources of FRBs. Magnetars are rotating neutron stars with extremely strong magnetic field and can sporadically emit bursts from X-ray (keV) to soft gamma-ray (sub-MeV) with duration from 102 s to 102 s. However, even though some bright radio bursts have been observed from some magnetars, no FRB-like events had been detected to be associated with any magnetar burst, including one giant flare, and no radio burst has been associated with any X-ray event from any magnetar. Therefore, there is still no observational evidence for magnetar-FRB association up to today. Recently, a pair of FRB-like bursts (FRB~200428 hereafter) separated by 30 milliseconds (ms) were detected from the general direction of the Galactic magnetar SGR~J1935+2154. Here we report the detection of a non-thermal X-ray burst in the 1--250,keV energy band with the Insight-HXMT satellite, which we identify as emitted from SGR~J1935+2154. The burst showed two hard peaks with a separation of ms, consistent with the separation between the two bursts in FRB~200428. The delay time between the double radio and X-ray peaks is 8:57s, fully consistent with the dispersion delay of FRB~200428. We thus identify the non-thermal X-ray burst is associated with FRB~200428 whose high energy counterpart is the two hard peaks in X-ray. Our results suggest that the non-thermal X-ray burst and FRB~200428 share the same physical origin in an explosive event from SGR~J1935+2154.
{"title":"Identification of a non-thermal X-ray burst with the Galactic magnetar SGR J1935+2154 and a fast radio burst using Insight-HXMT","authors":"C.K. Li, Lin Lin, S. Xiong, M. Ge, X.B. Li, Tipei Li, F. Lu, S. Zhang, Y. Tuo, Y. Nang, B. Zhang, S. Xiao, Yao-Tseng Chen, L. Song, Y.P. Xu, C.Z. Liu, S. Jia, X. Cao, J. Qu, Shu Zhang, Y. Gu, J. Liao, X.F. Zhao, Y. Tan, J. Nie, H.S. Zhao, S. Zheng, Y.G. Zheng, Q. Luo, C. Cai, B. Li, W. Xue, Q. Bu, Z. Chang, G. Chen, T.X. Chen, Yu-Peng Chen, Yongwei Dong, Y.Y. Du, H. Gao, G. Gao, M. Gao, Y. Gu, J. Huo, D. Han, L.H. Jiang, Y. Huang, Weichun Jiang, J. Jin, L. Kong, Gang Li, J. Guan, M.S. Li, W. Li, X. Li, X. Li, Y.G. Li, Z.W. Li, X. Liang, B. Liu, H.W. Liu, X.J. Liu, B. Lu, X.F. Lu, T. Luo, X. Ma, B. Meng, G. Ou, N. Sai, X.Y. Song, L. Sun, L. Tao, J. Wang, G.F. Wang, W. Wang, Y. Wang, X. Wen, B.B. Wu, B.Y. Wu, M. Wu, G. Xiao, H. Xu, J. Yang, S. Yang, Yi-Jung Yang, Y. Yang, Q. Yi, Q. Yin, Y. You, C. Zhang, A. Zhang, F. Zhang, H.M. Zhang, J. Zhang, T. Zhang, Wei Zhang, W. Zhang, Y. Zhang, Yue Zhang, Y.F. Zhang, Y.J. Zhang, Z.L. Zhang, D. Zhou, Y. Zhu, Y.X. Zhu, L. Chen, W.Z. Zhang, Y.B. Chen, W. Cui, J.K. Deng","doi":"10.21203/rs.3.rs-62191/v1","DOIUrl":"https://doi.org/10.21203/rs.3.rs-62191/v1","url":null,"abstract":"\u0000 Fast radio bursts (FRBs) are short pulses observed in radio band from cosmological distances, some of which emit repeating bursts. The physical origins of these mysterious events have been subject to wide speculations and heated debates. One class of models invoke soft gamma-ray repeaters (SGRs), or magnetars, as the sources of FRBs. Magnetars are rotating neutron stars with extremely strong magnetic field and can sporadically emit bursts from X-ray (keV) to soft gamma-ray (sub-MeV) with duration from 102 s to 102 s. However, even though some bright radio bursts have been observed from some magnetars, no FRB-like events had been detected to be associated with any magnetar burst, including one giant flare, and no radio burst has been associated with any X-ray event from any magnetar. Therefore, there is still no observational evidence for magnetar-FRB association up to today. Recently, a pair of FRB-like bursts (FRB~200428 hereafter) separated by 30 milliseconds (ms) were detected from the general direction of the Galactic magnetar SGR~J1935+2154. Here we report the detection of a non-thermal X-ray burst in the 1--250,keV energy band with the Insight-HXMT satellite, which we identify as emitted from SGR~J1935+2154. The burst showed two hard peaks with a separation of ms, consistent with the separation between the two bursts in FRB~200428. The delay time between the double radio and X-ray peaks is 8:57s, fully consistent with the dispersion delay of FRB~200428. We thus identify the non-thermal X-ray burst is associated with FRB~200428 whose high energy counterpart is the two hard peaks in X-ray. Our results suggest that the non-thermal X-ray burst and FRB~200428 share the same physical origin in an explosive event from SGR~J1935+2154.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86714778","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}
Andrea Derdzinski, D. D’Orazio, Paul C. Duffell, Z. Haiman, A. MacFadyen
Among the potential gravitational wave (GW) sources for the upcoming space-based interferometer LISA are extreme- or intermediate-mass ratio inspirals (EMRI/IMRIs). These events involve the coalescence of supermassive black holes in the mass range $10^5M_{odot}lesssim M lesssim 10^7M_{odot}$ with companion BHs of much lower masses. A subset of E/IMRIs are expected to occur in the accretion discs of active galactic nuclei (AGN). Previous work has shown that torques exerted by the disc can interfere with the inspiral and cause a phase shift in the GW waveform detectable by LISA. Here we use a suite of two-dimensional hydrodynamical simulations with the moving-mesh code DISCO to present a systematic study of disc torques. We measure torques on an inspiraling BH and compute the corresponding waveform deviations as a function of the binary mass ratio $qequiv M_2/M_1$, the disc viscosity ($alpha$), and gas temperature (or equivalently Mach number; $mathcal{M}$). We find that the absolute value of the gas torques is within an order of magnitude of previously determined planetary migration torques, but their precise value and sign depends non-trivially on the combination of these parameters, the inspiral rate, and the accretion rate onto the satellite BH. The gas imprint is generally detectable by LISA for binaries embedded in AGN discs with surface densities above $Sigma_0ge10^{4-6} rm , g , cm^{-2}$, depending on $q$, $alpha$ and $mathcal{M}$. We find that the deviations are most pronounced in discs with higher viscosities, and for E/IMRIs detected at frequencies where LISA is most sensitive. Torques in colder discs exhibit a noticeable dependence on the GW-driven inspiral rate as well as strong fluctuations at late stages of the inspiral. Our results further suggest that LISA may be able to place constraints on AGN disc parameters and the physics of disc-satellite interaction.
在即将到来的天基干涉仪LISA的潜在引力波(GW)源中，有极或中质量比激发(EMRI/IMRIs)。这些事件涉及到质量范围为$10^5M_{odot}lesssim M lesssim 10^7M_{odot}$的超大质量黑洞与质量低得多的伴星黑洞的合并。E/ imri的一个子集预计会发生在活动星系核(AGN)的吸积盘中。先前的工作表明，圆盘施加的扭矩会干扰吸气，并导致LISA探测到的GW波形相移。在这里，我们使用一套二维流体动力学模拟与运动网格代码DISCO来呈现一个系统的研究圆盘扭矩。我们测量了一个激励黑洞上的扭矩，并计算了相应的波形偏差，作为二元质量比$qequiv M_2/M_1$、圆盘粘度($alpha$)和气体温度(或等效马赫数;$mathcal{M}$)。我们发现，气体扭矩的绝对值与先前确定的行星迁移扭矩在一个数量级之内，但它们的精确值和符号很大程度上取决于这些参数的组合，即吸入率和对卫星黑洞的吸积率。对于表面密度高于$Sigma_0ge10^{4-6} rm , g , cm^{-2}$(取决于$q$, $alpha$和$mathcal{M}$)的AGN圆盘中嵌入的双星，通常可以用LISA检测到气体印记。我们发现，在粘度较高的圆盘中，以及在LISA最敏感的频率上检测到的E/IMRIs中，偏差最为明显。在较冷的圆盘中，扭矩表现出明显的依赖于gw驱动的吸气率，以及在吸气后期的强烈波动。我们的结果进一步表明，LISA可能能够对AGN圆盘参数和圆盘-卫星相互作用的物理特性施加约束。
{"title":"Evolution of gas disc–embedded intermediate mass ratio inspirals in the LISA band","authors":"Andrea Derdzinski, D. D’Orazio, Paul C. Duffell, Z. Haiman, A. MacFadyen","doi":"10.1093/mnras/staa3976","DOIUrl":"https://doi.org/10.1093/mnras/staa3976","url":null,"abstract":"Among the potential gravitational wave (GW) sources for the upcoming space-based interferometer LISA are extreme- or intermediate-mass ratio inspirals (EMRI/IMRIs). These events involve the coalescence of supermassive black holes in the mass range $10^5M_{odot}lesssim M lesssim 10^7M_{odot}$ with companion BHs of much lower masses. A subset of E/IMRIs are expected to occur in the accretion discs of active galactic nuclei (AGN). Previous work has shown that torques exerted by the disc can interfere with the inspiral and cause a phase shift in the GW waveform detectable by LISA. Here we use a suite of two-dimensional hydrodynamical simulations with the moving-mesh code DISCO to present a systematic study of disc torques. We measure torques on an inspiraling BH and compute the corresponding waveform deviations as a function of the binary mass ratio $qequiv M_2/M_1$, the disc viscosity ($alpha$), and gas temperature (or equivalently Mach number; $mathcal{M}$). We find that the absolute value of the gas torques is within an order of magnitude of previously determined planetary migration torques, but their precise value and sign depends non-trivially on the combination of these parameters, the inspiral rate, and the accretion rate onto the satellite BH. The gas imprint is generally detectable by LISA for binaries embedded in AGN discs with surface densities above $Sigma_0ge10^{4-6} rm , g , cm^{-2}$, depending on $q$, $alpha$ and $mathcal{M}$. We find that the deviations are most pronounced in discs with higher viscosities, and for E/IMRIs detected at frequencies where LISA is most sensitive. Torques in colder discs exhibit a noticeable dependence on the GW-driven inspiral rate as well as strong fluctuations at late stages of the inspiral. Our results further suggest that LISA may be able to place constraints on AGN disc parameters and the physics of disc-satellite interaction.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82641763","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 : 2020-05-19DOI: 10.1051/0004-6361/202037502
V. Suleimanov, J. Poutanen, K. Werner
Neutron stars (NSs) in low-mass X-ray binaries rotate at frequencies high enough to significantly deviate from sphericity ($nu_* sim$ 200--600 Hz). We investigate the effects of rapid rotation on the observational appearance of a NS. We propose analytical formulae relating gravitational mass and equatorial radius of the rapidly rotating NS to the mass $M$ and radius $R$ of a non-rotating NS of the same baryonic mass using accurate fully relativistic computations. We compute spectra from an oblate rotating NS observed at different inclination angles using the modified oblate Schwarzschild (MOS) approximation, where light bending is computed in Schwarzschild metric, but frame dragging and quadrupole moment of a NS are approximately accounted for in the photon redshift calculations. We generalize the cooling tail method to the case of a rapidly rotating NS to obtain the most probable values of $M$ and $R$ of the corresponding non-rotating NS with the same baryonic mass. We approximate the local spectra from the NS surface by a diluted blackbody using previously computed NS atmosphere models. We show that the NS radius could be overestimated by 3--3.5 km for face-on stars of $Rapprox 11$ km rotating at $nu_* =$ 700 Hz if the version of the cooling tail method for a non-rotating NS is used. We apply the method to an X-ray burst observed from the NS rotating at $nu_* approx$ 532 Hz in SAX J1810.8$-$2609. The resulting radius of the non-rotating NS (assuming $M=1.5 M_odot$) becomes $11.8pm0.5$ km if it is viewed at inclination i=60 deg and $R=11.2pm0.5$ km for a face-on view, which are smaller by 0.6 and 1.2 km than the radius obtained using standard cooling tail method ignoring rotation. The corresponding equatorial radii of these rapidly rotating NSs are 12.3$pm 0.6$ km (for i=60 deg) and 11.6$pm 0.6$,km (for i=0 deg).
{"title":"Observational appearance of rapidly rotating neutron stars","authors":"V. Suleimanov, J. Poutanen, K. Werner","doi":"10.1051/0004-6361/202037502","DOIUrl":"https://doi.org/10.1051/0004-6361/202037502","url":null,"abstract":"Neutron stars (NSs) in low-mass X-ray binaries rotate at frequencies high enough to significantly deviate from sphericity ($nu_* sim$ 200--600 Hz). We investigate the effects of rapid rotation on the observational appearance of a NS. We propose analytical formulae relating gravitational mass and equatorial radius of the rapidly rotating NS to the mass $M$ and radius $R$ of a non-rotating NS of the same baryonic mass using accurate fully relativistic computations. We compute spectra from an oblate rotating NS observed at different inclination angles using the modified oblate Schwarzschild (MOS) approximation, where light bending is computed in Schwarzschild metric, but frame dragging and quadrupole moment of a NS are approximately accounted for in the photon redshift calculations. We generalize the cooling tail method to the case of a rapidly rotating NS to obtain the most probable values of $M$ and $R$ of the corresponding non-rotating NS with the same baryonic mass. We approximate the local spectra from the NS surface by a diluted blackbody using previously computed NS atmosphere models. We show that the NS radius could be overestimated by 3--3.5 km for face-on stars of $Rapprox 11$ km rotating at $nu_* =$ 700 Hz if the version of the cooling tail method for a non-rotating NS is used. We apply the method to an X-ray burst observed from the NS rotating at $nu_* approx$ 532 Hz in SAX J1810.8$-$2609. The resulting radius of the non-rotating NS (assuming $M=1.5 M_odot$) becomes $11.8pm0.5$ km if it is viewed at inclination i=60 deg and $R=11.2pm0.5$ km for a face-on view, which are smaller by 0.6 and 1.2 km than the radius obtained using standard cooling tail method ignoring rotation. The corresponding equatorial radii of these rapidly rotating NSs are 12.3$pm 0.6$ km (for i=60 deg) and 11.6$pm 0.6$,km (for i=0 deg).","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"37 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88169303","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 : 2020-05-17DOI: 10.1103/PHYSREVD.103.043011
T. Tsutsui, K. Cannon, L. Tsukada
Multi-messenger astronomy is of great interest since the success of the electromagnetic follow up of the neutron star merger GW170817. However, the information that was learned from GW170817 was limited by the long delay in finding the optical transient. Even in the best-case scenario, the current gravitational-wave source localization method is not sufficient for some frequency bands. Therefore, one needs a more rapid localization method even if it is less accurate. Building upon an Excess power method, we describe a new localization method for compact object collisions that produces posterior probability maps in only a few hundred milliseconds. Some accuracy is lost, with the searched sky areas being approximately $10$ times larger. We imagine this new technique playing a role in a hierarchical scheme were fast early location estimates are iteratively improved upon as better analyses complete on longer time scales.
{"title":"High speed source localization in searches for gravitational waves from compact object collisions","authors":"T. Tsutsui, K. Cannon, L. Tsukada","doi":"10.1103/PHYSREVD.103.043011","DOIUrl":"https://doi.org/10.1103/PHYSREVD.103.043011","url":null,"abstract":"Multi-messenger astronomy is of great interest since the success of the electromagnetic follow up of the neutron star merger GW170817. However, the information that was learned from GW170817 was limited by the long delay in finding the optical transient. Even in the best-case scenario, the current gravitational-wave source localization method is not sufficient for some frequency bands. Therefore, one needs a more rapid localization method even if it is less accurate. Building upon an Excess power method, we describe a new localization method for compact object collisions that produces posterior probability maps in only a few hundred milliseconds. Some accuracy is lost, with the searched sky areas being approximately $10$ times larger. We imagine this new technique playing a role in a hierarchical scheme were fast early location estimates are iteratively improved upon as better analyses complete on longer time scales.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82661256","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 : 2020-05-15DOI: 10.5506/APhysPolBSupp.13.261
Ishika Palit, A. Janiuk, P. Suková
We prescribe a method to study the effects of self-gravity of accretion disk around a black hole associated with long Gamma Ray Bursts (GRBs) in an evolving background Kerr metric. This is an extension to our previous work where we presented possible constraints for the final masses and spins of these astrophysical black holes. Incorporating the self-force of the accreting cloud around the black hole is a very important aspect due to the transient nature of the event, in which a huge amount of mass is accreted and changes the fundamental black hole parameters i.e. its mass and spin, during the process. Understanding of the GRBs engine is important because they are possible sources of high-energy particles and gravitational waves as most of the energy released from the dynamical evolution is in the form of gravitational radiation. Here, we describe the analytical framework we developed to employ in our numerical model. The numerical studies are planned for the future work.
{"title":"Effects of Self-gravity of the Accretion Disk Around Rapidly Rotating Black Hole in Long Gamma Ray Bursts","authors":"Ishika Palit, A. Janiuk, P. Suková","doi":"10.5506/APhysPolBSupp.13.261","DOIUrl":"https://doi.org/10.5506/APhysPolBSupp.13.261","url":null,"abstract":"We prescribe a method to study the effects of self-gravity of accretion disk around a black hole associated with long Gamma Ray Bursts (GRBs) in an evolving background Kerr metric. This is an extension to our previous work where we presented possible constraints for the final masses and spins of these astrophysical black holes. Incorporating the self-force of the accreting cloud around the black hole is a very important aspect due to the transient nature of the event, in which a huge amount of mass is accreted and changes the fundamental black hole parameters i.e. its mass and spin, during the process. Understanding of the GRBs engine is important because they are possible sources of high-energy particles and gravitational waves as most of the energy released from the dynamical evolution is in the form of gravitational radiation. Here, we describe the analytical framework we developed to employ in our numerical model. The numerical studies are planned for the future work.","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77582253","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 : 2020-05-14DOI: 10.18154/RWTH-2020-02650
N. Zimmermann
This thesis presents an analysis of the cosmic-ray electron and positron flux using the AMS-02 detector on the International Space Station as a function of time and energy. The time-averaged flux is integrated over 6.5 years of AMS-02 science data and provides the electron and positron flux with unprecedented accuracy, covering the energy range from 0.5 GeV to 1 TeV. In total 28.39 million events were identified as electrons and 1.95 million as positrons. For each of the 88 Bartels rotation periods (27 days), within the 6.5 years, an individual electron and positron flux is derived spanning the energy range from 1 - 50 GeV. The challenge of the analysis is to extract the small electron and positron signal in the overwhelming proton background present in cosmic rays. A detailed description of the analysis techniques is presented, including a thorough derivation of the systematic uncertainties. The main motivation for measuring the cosmic-ray electron and positron flux in a time-averaged way is to explore the energy dependence up to high energies in detail and search for structures in the spectrum. The traditional understanding is that electrons are primary cosmic rays, whereas positrons are believed to be secondaries, produced by collisions of primary protons with the interstellar medium. A clear deviation from the traditional understanding was discovered: the positron flux cannot be described by a single power law, nor by the sum of two power laws. The secondary production term plus an additional source term, with a finite cut-off energy, is necessary to describe the positron data. Above the cut-off energy, the positron flux is rapidly decreasing. The cut-off is established with a significance of 4σ, providing strong evidence that a new source of cosmic-ray positrons was discovered, which is responsible for the rise of the positron flux, and its decrease at high energies when the source term contribution is vanishing. The origin of the source term remains unclear: both astrophysical sources, such as pulsars, and dark-matter annihilation are candidates to describe the positron flux data. The majority of the electrons is believed to come from one of the several astrophysical sources, each making a power law contribution to the electron flux. The electron flux was found to be well described by the sum of two power laws over the whole energy range, supporting the observation that more than one astrophysical source is responsible for the measured electron flux. For the first time, the charge-sign dependent modulation during solar maximum has been investigated by electrons and positrons alone, using the time-dependent fluxes derived in this thesis. Short-term effects such as Forbush decreases and solar flares were identified simultaneously in the electron and positron flux that cancel in the positron/electron ratio. Long-term effects are revealed in the positron/electron ratio: A smooth transition from one value to another, after the polarity reversal
{"title":"Precision measurement of the cosmic-ray electron and positron fluxes as a function of time and energy with the Alpha Magnetic Spectrometer on the International Space Station","authors":"N. Zimmermann","doi":"10.18154/RWTH-2020-02650","DOIUrl":"https://doi.org/10.18154/RWTH-2020-02650","url":null,"abstract":"This thesis presents an analysis of the cosmic-ray electron and positron flux using the AMS-02 detector on the International Space Station as a function of time and energy. The time-averaged flux is integrated over 6.5 years of AMS-02 science data and provides the electron and positron flux with unprecedented accuracy, covering the energy range from 0.5 GeV to 1 TeV. In total 28.39 million events were identified as electrons and 1.95 million as positrons. For each of the 88 Bartels rotation periods (27 days), within the 6.5 years, an individual electron and positron flux is derived spanning the energy range from 1 - 50 GeV. The challenge of the analysis is to extract the small electron and positron signal in the overwhelming proton background present in cosmic rays. A detailed description of the analysis techniques is presented, including a thorough derivation of the systematic uncertainties. The main motivation for measuring the cosmic-ray electron and positron flux in a time-averaged way is to explore the energy dependence up to high energies in detail and search for structures in the spectrum. The traditional understanding is that electrons are primary cosmic rays, whereas positrons are believed to be secondaries, produced by collisions of primary protons with the interstellar medium. A clear deviation from the traditional understanding was discovered: the positron flux cannot be described by a single power law, nor by the sum of two power laws. The secondary production term plus an additional source term, with a finite cut-off energy, is necessary to describe the positron data. Above the cut-off energy, the positron flux is rapidly decreasing. The cut-off is established with a significance of 4σ, providing strong evidence that a new source of cosmic-ray positrons was discovered, which is responsible for the rise of the positron flux, and its decrease at high energies when the source term contribution is vanishing. The origin of the source term remains unclear: both astrophysical sources, such as pulsars, and dark-matter annihilation are candidates to describe the positron flux data. The majority of the electrons is believed to come from one of the several astrophysical sources, each making a power law contribution to the electron flux. The electron flux was found to be well described by the sum of two power laws over the whole energy range, supporting the observation that more than one astrophysical source is responsible for the measured electron flux. For the first time, the charge-sign dependent modulation during solar maximum has been investigated by electrons and positrons alone, using the time-dependent fluxes derived in this thesis. Short-term effects such as Forbush decreases and solar flares were identified simultaneously in the electron and positron flux that cancel in the positron/electron ratio. Long-term effects are revealed in the positron/electron ratio: A smooth transition from one value to another, after the polarity reversal ","PeriodicalId":8437,"journal":{"name":"arXiv: High Energy Astrophysical Phenomena","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85169560","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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