作者机构：
[Yu, Yun-Wei] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;[Yu, Yun-Wei] Cent China Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Peoples R China.;[Zou, Yuan-Chuan] Huazhong Univ Sci & Technol, Sch Phys, Wuhan 430074, Peoples R China.;[Dai, Zi-Gao] Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Peoples R China.;[Yu, Wen-Fei] Chinese Acad Sci, Shanghai Astron Observ, Key Lab Res Galaxies & Cosmol, 80 Nandan Rd, Shanghai 200030, Peoples R China.
通讯机构：
[Yu, Yun-Wei] C;Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Peoples R China.
关键词：
stars: magnetar;stars: neutron;radio continuum: general
摘要：
<jats:title>Abstract</jats:title>
<jats:p>Neutron star mergers are believed to occur in accretion disks around supermassive black holes. Here we show that a putative jet launched from the merger of a binary neutron star (BNS) or a neutron star–black hole (NSBH) merger occurring at the migration trap in an active galactic nucleus (AGN) disk would be choked. The jet energy is deposited within the disk materials to power a hot cocoon. The cocoon is energetic enough to break out from the AGN disk and produce a bright X-ray shock breakout transient peaking at ∼0.15 days after the merger. The peak luminosity is estimated as <jats:inline-formula>
<jats:tex-math>
<?CDATA $\sim {10}^{46}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabd412ieqn1.gif" xlink:type="simple" />
</jats:inline-formula>, which can be discovered by the Einstein Probe from <jats:inline-formula>
<jats:tex-math>
<?CDATA $z\lesssim 0.5$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjlabd412ieqn2.gif" xlink:type="simple" />
</jats:inline-formula>. Later on, the nonrelativistic ejecta launched from the merger would break out the disk, powering an X-ray/UV flare peaking at ∼0.5 days after the merger. This second shock breakout signal may be detected by UV transient searches. The cocoon cooling emission and kilonova emission are outshone by the disk emission and are difficult to detect. Future joint observations of gravitational waves from BNS/NSBH mergers and associated two shock breakout signatures can provide strong support for the compact binary coalescence formation channel in AGN disks.</jats:p>
摘要：
A rapidly rotating and highly magnetized neutron star (NS) could be formed from explosive phenomena such as superluminous supernovae and gamma-ray bursts. This newborn NS can substantially influence the emission of these explosive transients through its spin-down. The spin-down evolution of the NS can sometimes be affected by fallback accretion, although it is usually regulated by the magnetic dipole radiation and gravitational wave radiation of the NS. Under appropriate conditions, the accreting material can be first ejected and subsequently recycled back, so that the accretion disk can remain in a quasi-steady state for a long time. Here we describe the interaction of the NS with such a propeller-recycling disk and their coevolution. Our result shows that the spin-down of the NS can be initially dominated by the propeller, which prevents the disk material from falling onto the NS until hundreds or thousands of seconds later. It is suggested that the abrupt fall of the disk material onto the NS could significantly suppress the magnetic dipole radiation and then convert the NS from a normal magnetar to a low-field magnetar. This evolution behavior of the newborn NS can help us understand the very different influence of the NS on the early GRB afterglows and the late supernova/kilonova emission.
关键词：
Radio bursts;Radio transient sources;Neutron stars;Magnetars;X-ray transient sources;Non-thermal radiation sources
摘要：
The nature of fast radio bursts (FRBs) is currently unknown. Repeating FRBs offer better observation opportunities than nonrepeating FRBs because their simultaneous multiwavelength counterparts might be identified. The magnetar flare model of FRBs is one of the most promising models that predict high-energy emission in addition to radio burst emission. To investigate such a possibility, we have searched for simultaneous and quasi-simultaneous short-term hard X-ray bursts in all Swift/BAT event mode data, which covered the periods when FRB detections were reported in the repeating FRB 121102, by making use of BAT's arcminute-level spatial resolution and wide field of view. We did not find any significant hard X-ray bursts that occurred simultaneously with those radio bursts. We also investigated potential short X-ray bursts that occurred quasi-simultaneously with those radio bursts (occurrence time differs in the range from hundreds of seconds to thousands of seconds) and concluded that even the best candidates are consistent with background fluctuations. Therefore, our investigation concluded that there were no hard X-ray bursts detectable with Swift/BAT that occurred simultaneously or quasi-simultaneously with those FRBs in the repeating FRB 121102.
作者机构：
[Dai, Z. G.; Wang, F. Y.; Wang, Y. Y.] Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Peoples R China.;[Dai, Z. G.; Wang, F. Y.] Nanjing Univ, Minist Educ, Key Lab Modern Astron & Astrophys, Nanjing 210093, Peoples R China.;[Yang, Yuan-Pei] Yunnan Univ, South Western Inst Astron Res, Kunming, Yunnan, Peoples R China.;[Yu, Y. W.] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;[Zuo, Z. Y.] Xi An Jiao Tong Univ, Sch Sci, Xian 710049, Peoples R China.
通讯机构：
[Wang, F. Y.] N;Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Peoples R China.;Nanjing Univ, Minist Educ, Key Lab Modern Astron & Astrophys, Nanjing 210093, Peoples R China.
关键词：
Radio bursts;Gamma-ray bursts;Magnetars;Binary stars;Gravitational waves
摘要：
<jats:title>Abstract</jats:title>
<jats:p>Young neutron stars (NSs) born in core-collapse explosions are promising candidates for the central engines of fast radio bursts (FRBs), since the first localized repeating burst FRB 121102 occurs in a star-forming dwarf galaxy similar to the host galaxies of superluminous supernovae and long gamma-ray bursts. However, FRB 180924 and FRB 190523 are localized to massive galaxies with low rates of star formation, compared with the host of FRB 121102. The offsets between the bursts and host centers are about 4 and 29 kpc for FRB 180924 and FRB 190523, respectively. These host properties are similar to those of short gamma-ray bursts (GRBs), which are produced by binary neutron star (BNS) or NS–black hole mergers. Therefore, the NSs powering FRBs may be formed in BNS mergers. In this paper, we study BNS merger rates and merger times, and predict the most likely merger locations for different types of host galaxies using the population synthesis method. We find that the BNS merger channel is consistent with the recently reported offsets of FRB 180924 and FRB 190523. The offset distribution of short GRBs is well reproduced by population synthesis using a galaxy model similar to that of GRB hosts. The event rate of FRBs (including non-repeating and repeating), is larger than those of BNS mergers and short GRBs, and requires a large fraction of observed FRBs emitting several bursts. Using curvature radiation by bunches in NS magnetospheres, we also predict the observational properties of FRBs from BNS mergers, including the dispersion measure and rotation measure. At late times (<jats:italic>t</jats:italic>≥1 yr), the contribution to dispersion measure and rotation measure from BNS merger ejecta can be neglected.</jats:p>
作者机构：
[Yu, Yun-Wei] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;[Yu, Yun-Wei] Cent China Normal Univ, Key Lab Quark & Lepton Phys, Minist Educ, Wuhan 430079, Peoples R China.
通讯机构：
[Yu, Yun-Wei] C;Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys, Minist Educ, Wuhan 430079, Peoples R China.
摘要：
<jats:title>Abstract</jats:title>
<jats:p>It is believed that the relativistic jets of gamma-ray bursts (GRBs) should initially propagate through a heavy envelope of the massive progenitor stars or through merger ejecta formed from compact binary mergers. The interaction of a jet with a stellar envelope or merger ejecta can lead to the deceleration of the head material of the jet and simultaneously the formation of a hot cocoon. However, this jet-envelope/ejecta interaction is actually undetectable with electromagnetic radiation and can only be inferred indirectly by the structure of the breakout jet. Therefore, as a solution to this phenomenon, we suggest the jet-envelope/ejecta interaction can produce a gravitational-wave (GW) memory of an amplitude of <jats:inline-formula>
<jats:tex-math>
<?CDATA $h\sim {10}^{-26}\mbox{--}{10}^{-23}$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjab93ccieqn1.gif" xlink:type="simple" />
</jats:inline-formula>, which could be detected with some future GW detectors sensitive in the frequency range from sub-Hertz to several tens of Hertz. This provides a potential direct way to probe the jet propagation and then the interior of the GRB progenitors.</jats:p>
作者机构：
[Tan, Wei-Wei] Hubei Univ Educ, Sch Phys & Mech Elect Engn, Wuhan 430205, Peoples R China.;[Tan, Wei-Wei] Hubei Univ Educ, Res Ctr Astron, Wuhan 430205, Peoples R China.;[Yu, Yun-Wei] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.
通讯机构：
[Yu, Yun-Wei] C;Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.
关键词：
Gamma-ray bursts (629)
摘要：
The joint observation of GW170817 and GRB 170817A indicated that short gamma-ray bursts (SGRBs) can originate from binary neutron star mergers. Moreover, some SGRBs could be detected off axis, while the SGRB jets are highly structured. Then, by assuming a universal angular distribution of the jet emission for all SGRBs, we reproduce the flux and redshift distributions of the cosmological SGRBs detected by Swift and Fermi. For self-consistency, this angular distribution is simultaneously constrained by the luminosity and event rate of GRB 170817A. As a result, it is found that the universal jet structure of SGRBs could approximately have a two-Gaussian profile. Meanwhile, the intrinsic luminosity function (LF) of the on-axis emission of the jets can be simply described by a single power law with a low-luminosity exponential cutoff. The usually discovered broken-power-law apparent LF for relatively high luminosities can naturally result from the coupling of the intrinsic LF with the angular distribution of the jet emission, as the viewing angles to the SGRBs are arbitrarily distributed.
作者机构：
[Yu Yun-wei] College of Physical Science and Technology, Central China Normal University, Wuhan 430079
摘要：
The neutron star-neutron star and neutron star-black hole mergers may cause the intense radiation of high-frequency gravitational waves (GWs), they can also produce various electromagnetic emissions by ejecting materials outwards. Therefore, these merger events are the most important targets of current multi-messenger astronomical studies. The thermal transient radiation emitted from merger ejecta is called the kilonova or, more generally, the mergernova, which is powered by the radioactive decays of r-process elements, and the energy injection from the central merger product. This phenomenon was first predicted theoretically by Li and Paczynski in 1998, and confirmed by the optical-infrared observations of the GW170817 event in 2017. As a result, the kilonova/mergernova observation had played a crucial role in locating GW170817, identifying its astrophysical origin, and even constraining the nature of the merger product of this event. This paper briefly reviews the primary progress of kilonova/mergernova researches, including the initiative, improvement, and development of the model, the observational discoveries of candidates, and the optical electromagnetic counterpart of GW170817.
作者机构：
[Yu, Yun-Wei] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.
通讯机构：
[Yu, Yun-Wei] C;Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Hubei, Peoples R China.
关键词：
gamma ray bursts: general;gravitational waves
摘要：
<jats:title>Abstract</jats:title>
<jats:p>During the in-spiral stage of a compact binary, a wind bubble could be blown into the interstellar medium, if electromagnetic radiation due to the binary orbital motion is strong enough. Therefore, short-duration gamma-ray bursts (SGRBs) due to double neutron star mergers would in principle happen in a wind bubble environment, which can influence the propagation of the SGRB jet and consequent afterglow emission. By calculating the dynamics and synchrotron radiation of the jet-driven external shock, we reveal that an abrupt jump could appear in the afterglow light curves of SGRBs and the observational time of the jump is dependent on the viewing angle. This light curve jump provides an observational signature to constrain the radius of the wind bubble and thus the power of the electromagnetic radiation of the binary, by combining with gravitational wave detection.</jats:p>
作者机构：
[Yu, Yun-Wei; Li, Shao-Ze; Chen, Aming] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;[Liu, Liang-Duan; Dai, Zi-Gao] Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Peoples R China.;[Zhu, Jin-Ping] Peking Univ, Kavli Inst Astron & Astrophys, Beijing 100871, Peoples R China.;[Zhu, Jin-Ping] Peking Univ, Dept Astron, Beijing 100871, Peoples R China.
通讯机构：
[Yu, Yun-Wei] C;Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.
会议名称：
XIAMEN-CUSTIPEN WORKSHOP ON THE EQUATION OF STATE OF DENSE NEUTRON-RICH MATTER IN THE ERA OF GRAVITATIONAL WAVE ASTRONOMY
摘要：
The formation of neutron stars (NSs), both from collapses of massive stars and mergers of compact objects, can be usually indicated by bright transients emitted from explosively-ejected material. In particular, if the newborn NSs can rotate at a millisecond period and have a sufficiently high magnetic field, then the spin-down of the NSs would provide a remarkable amount of energy to the emitting material. As a result, super-luminous supernovae could be produced in the massive stellar collapse cases, while some unusual fast evolving and luminous optical transients could arise from the cases of NS mergers and accretion-induced collapses of white dwarfs. In all cases, if the dipolar magnetic fields of the newborn NSs can be amplified to be as high as 1015 G, a relativistic jet could be launched and then a gamma-ray burst can be produced as the jet successfully breaks out from the surrounding nearly-isotropic ejected material.
关键词：
Radio bursts;Radio transient sources;Neutron stars;Magnetars;X-ray transient sources;Non-thermal radiation sources
摘要：
<jats:title>Abstract</jats:title>
<jats:p>The nature of fast radio bursts (FRBs), which occur on millisecond timescales in the radio band, is well-understood. Among their unknown observational properties are their broadband spectra, and persistent and transient multiwavelength counterparts. Well-localized FRBs provide the opportunity to address these issues in archival observations. We performed searches for 15–150 keV hard X-ray bursts on timescales as short as 1 ms in the direction of the repeating FRB 121102 (with a spacial resolution of a few arcminutes) in the archival <jats:italic>Swift</jats:italic>/BAT data between 2016 October and 2017 September. We found no significant (5<jats:italic>σ</jats:italic>) hard X-ray bursts in the direction of the repeating FRB. We derived an upper limit of the hard X-ray (15–150 keV) flux of any X-ray bursts on a 1 ms timescale of around 1.01×10<jats:sup>−7</jats:sup> erg cm<jats:sup>−2</jats:sup> s<jats:sup>−1</jats:sup>, if assuming a photoindex of 2 for potential X-ray flares in the X-ray band. A plausible scenario for the repeating FRB as being associated with a <jats:italic>magnetar giant flare</jats:italic> is still far below the upper limit.</jats:p>
作者：
Chen, A. M.*;Takata, J.;Yi, S. X.;Yu, Y. W.（俞云伟）;Cheng, K. S.
期刊：
ASTRONOMY AND ASTROPHYSICS,2019年627:A87- ISSN：0004-6361
通讯作者：
Chen, A. M.
作者机构：
[Yu, Y. W.; Chen, A. M.] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Hubei, Peoples R China.;[Chen, A. M.; Yi, S. X.; Cheng, K. S.] Univ Hong Kong, Dept Phys, Pokfulam Rd, Hong Kong, Peoples R China.;[Takata, J.] Huazhong Univ Sci & Technol, Sch Phys, Wuhan 430074, Hubei, Peoples R China.;[Yi, S. X.] Radboud Univ Nijmegen, Dept Astrophys, POB 9010, NL-6500 GL Nijmegen, Netherlands.
通讯机构：
[Chen, A. M.] C;[Chen, A. M.] U;Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Hubei, Peoples R China.;Univ Hong Kong, Dept Phys, Pokfulam Rd, Hong Kong, Peoples R China.
关键词：
Binaries: close;Gamma rays: stars;Pulsars: individual: PSR B1259-63;X-rays: binaries
摘要：
<jats:title>Abstract</jats:title>
<jats:p>Super-Chandrasekhar remnants of double white dwarf mergers could sometimes collapse into a rapidly rotating neutron star (NS), accompanying with a mass ejection of a few times 0.01 <jats:italic>M</jats:italic>
<jats:sub>⊙</jats:sub>. Bright optical transient emission can be produced by the ejecta due to heating by radioactivities and particularly by energy injection from the NS. Since the merger remnants before collapse resemble a star evolving from the asymptotic giant branch phase to the planetary nebula phase, an intense dusty wind is considered to be driven about several thousand years ago before the collapse and surround the remnant at large radii. Therefore, the optical transient emission can be somewhat absorbed and scattered by the dusty wind, which can suppress the peak emission and cause a scattering plateau in optical light curves. Several years later, as the ejecta finally catches up with the wind material, the shock interaction between them can further give rise to a detectable radio transient emission on a timescale of several tens of days. Discovery of and observations to such dust-affected optical transients and shock-driven radio transients can help to explore the nature of super-Chandrasekhar merger remnants and as well as the density and type ratios of double white dwarf systems, which is beneficial in assessing their gravitational wave contributions.</jats:p>
作者机构：
[Yu, Yun-Wei; Chen, Aming] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Hubei, Peoples R China.;[Yu, Yun-Wei; Chen, Aming] Cent China Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.;[Li, Xiang-Dong] Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Jiangsu, Peoples R China.;[Li, Xiang-Dong] Nanjing Univ, Minist Educ, Key Lab Modern Astron & Astrophys, Nanjing, Jiangsu, Peoples R China.
通讯机构：
[Yu, Yun-Wei] C;Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Hubei, Peoples R China.;Cent China Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Hubei, Peoples R China.
关键词：
stars: neutron;supernovae: general;white dwarfs;X-rays: general
摘要：
<jats:title>Abstract</jats:title>
<jats:p>The accretion-induced collapse (AIC) of a white dwarf in a binary with a nondegenerate companion can sometimes lead to the formation of a rapidly rotating and highly magnetized neutron star (NS). The spin-down of this NS can drive a powerful pulsar wind (PW) and bring out some detectable multi-wavelength emissions. On the one hand, the PW can evaporate the companion in a few days to form a torus surrounding the NS. Then, due to the blockage of the PW by the torus, a reverse shock can be formed in the wind to generate intense hard X-rays. This emission component disappears in a few weeks’ time, after the torus is broken down at its inner boundary and scoured into a very thin disk. On the other hand, the interaction between the PW with an AIC ejecta can lead to a termination shock of the wind, which can produce a long-lasting soft X-ray emission component. In any case, the high-energy emissions from deep inside the system can be detected only after the AIC ejecta becomes transparent for X-rays. Meanwhile, by absorbing the X-rays, the AIC ejecta can be heated effectively and generate a fast-evolving and luminous ultraviolet (UV)/optical transient. Therefore, the predicted hard and soft X-ray emissions, associated by an UV/optical transient, provide a clear observational signature for identifying AIC events in current and future observations (e.g., AT 2018cow).</jats:p>
