作者机构：
[Ren, Jia; Yang, Jun; Wang, Xiangyu Ivy; Zou, Ze-Cheng] Nanjing Univ, Sch Astron & Space Sci, Nanjing 210093, Peoples R China.;[Yu, Yun-Wei; Yu, YW] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;[Yu, Yun-Wei; Yu, YW] Cent China Normal Univ, Key Lab Quark & Lepton Phys, Minist Educ, Wuhan 430079, Peoples R China.;[Zhu, Jin-Ping] Monash Univ, Sch Phys & Astron, Clayton, Vic 3800, Australia.;[Zhu, Jin-Ping] OzGrav, ARC Ctr Excellence Gravitat Wave Discovery, Clayton, Vic 3800, Australia.
通讯机构：
[Yu, YW ] 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：
The second brightest gamma-ray burst, GRB 230307A (with a duration T 90 similar to 40 s), exhibited characteristics indicative of a magnetar engine during the prompt emission phase. Notably, a suspected kilonova was identified in its follow-up optical and infrared observations. Here we propose that the origin of GRB 230307A is a neutron star-white dwarf (NS-WD) merger as this could naturally explain the long duration and the large physical offset from the center of its host galaxy. In the framework of such an NS-WD merger event, the late-time kilonova-like emission is very likely to be powered by the spin-down of the magnetar and the radioactive decay of 56Ni, rather than by the decay of r-process elements as these heavy elements may not easily be synthesized in an NS-WD merger. It is demonstrated that the above scenario can be supported by our fit to the late-time observational data, where a mass of similar to 10-3 M circle dot 56Ni is involved in the ejecta of a mass of similar to 0.1 M circle dot. Particularly, the magnetar parameters required by the fit are consistent with those derived from the early X-ray observation.
作者机构：
[Zhu, Jin-Ping; Liu, Chang; Kang, Yacheng] Peking Univ, Sch Phys, Dept Astron, Beijing 100871, Peoples R China.;[Wu, Shichao] Albert Einstein Inst, Max Planck Inst Gravitat Phys, D-30167 Hannover, Germany.;[Wu, Shichao] Leibniz Univ Hannover, D-30167 Hannover, Germany.;[Yang, Yuan-Pei] Yunnan Univ, South Western Inst Astron Res, Kunming, Yunnan, Peoples R China.;[Shao, Lijing; Liu, Chang; Kang, Yacheng] Peking Univ, Kavli Inst Astron & Astrophys, Beijing 100871, Peoples R China.
摘要：
In the second work of this series, we explore the optimal search strategy for serendipitous and gravitational-wave-triggered target-of-opportunity (ToO) observations of kilonovae and optical short-duration gamma-ray burst (sGRB) afterglows from binary neutron star (BNS) mergers, assuming that cosmological kilonovae are AT2017gfo-like (but with viewing-angle dependence) and that the properties of afterglows are consistent with those of cosmological sGRB afterglows. A one-day cadence serendipitous search strategy with an exposure time of similar to 30 s can always achieve an optimal search strategy of kilonovae and afterglows for various survey projects. We show that the optimal detection rates of the kilonovae (afterglows) are similar to 0.3/0.6/1/20 yr(-1) (similar to 50/60/100/800 yr(-1)) for Zwicky the Transient Facility (ZTF)/Multi-channel Photometric Survey Telescope (Mephisto)/Wide Field Survey Telescope (WFST)/Large Synoptic Survey Telescope (LSST), respectively. A better search strategy for SiTian than the current design is to increase the exposure time. In principle, a fully built SiTian can detect similar to 7(2000) yr(-1) kilonovae (afterglows). Population properties of electromagnetic (EM) signals detected by serendipitous observations are studied in detail. For ToO observations, we predict that one can detect similar to 11 yr(-1) BNS gravitational wave (GW) events during the fourth observing run (O4) by considering an exact duty cycle of the third observing run. The median GW sky localization area is expected to be similar to 10 deg(2) for detectable BNS GW events. For O4, we predict that ZTF/Mephisto/WFST/LSST can detect similar to 5/4/3/3 kilonovae (similar to 1/1/1/1 afterglows) per year, respectively. The GW detection rates, GW population properties, GW sky localizations, and optimistic ToO detection rates of detectable EM counterparts for BNS GW events at the Advanced Plus, LIGO Voyager, and ET&CE eras are detailedly simulated in this paper.
作者机构：
[Wang, N.; Wang, S. Q.; Yao, J. M.] Chinese Acad Sci, Xinjiang Astron Observ, Urumqi 830011, Xinjiang, Peoples R China.;[Wang, N.; Wang, S. Q.; Yao, J. M.] Chinese Acad Sci, Key Lab Radio Astron, Urumqi 830011, Xinjiang, Peoples R China.;[Wang, N.; Wang, S. Q.; Yao, J. M.] Xinjiang Key Lab Radio Astrophys, Urumqi 830011, Xinjiang, Peoples R China.;[Wang, J. B.] Lishui Univ, Inst Optoelect Technol, Lishui 323000, Zhejiang, Peoples R China.;[Li, D. Z.] CALTECH, Cahill Ctr Astron & Astrophys, 1216 E Calif Blvd, Pasadena, CA 91125 USA.
通讯机构：
[Wang, SQ ] C;Chinese Acad Sci, Xinjiang Astron Observ, Urumqi 830011, Xinjiang, Peoples R China.;Chinese Acad Sci, Key Lab Radio Astron, Urumqi 830011, Xinjiang, Peoples R China.;Xinjiang Key Lab Radio Astrophys, Urumqi 830011, Xinjiang, Peoples R China.
期刊：
ASTRONOMY AND ASTROPHYSICS,2023年675 ISSN：0004-6361
通讯作者：
Yu, YW
作者机构：
[Yu, Yun-Wei; Zhang, Zi-Liang; Yu, YW] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;[Yu, Yun-Wei; Zhang, Zi-Liang; Yu, YW] Cent China Normal Univ, Key Lab Quark & Lepton Phys, Minist Educ, Wuhan 430079, Peoples R China.;[Cao, Xiao-Feng] Hubei Univ Educ, Sch Phys & Elect Informat, Wuhan 430205, Peoples R China.
通讯机构：
[Yu, YW ] 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.
作者机构：
[Yu, Yun-Wei; Zheng, Xiao-Ping; Du, Ze-Xin; Yu, YW] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;[Yu, Yun-Wei; Zheng, Xiao-Ping; Yu, YW] Cent China Normal Univ, Key Lab Quark & Lepton Phys, Minist Educ, Wuhan 430079, Peoples R China.;[Chen, A-Ming] Shanghai Jiao Tong Univ, Tsung Dao Lee Inst, Shanghai 201210, Peoples R China.;[Zhou, Xia; Wang, Shuang-Qiang] Chinese Acad Sci, Xinjiang Astron Observ, Urumqi 830011, Peoples R China.;[Zhou, Xia] Chinese Acad Sci, Key Lab Radio Astron, Nanjing 210008, Peoples R China.
通讯机构：
[Yu, YW ] 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：
Black widows (BWs) are millisecond pulsars ablating their companion stars. The out-flowing material from the companion can block the radio emission of the pulsar, resulting in eclipses. In this paper, we construct a model for the radio eclipse by calculating the geometry of the bow shock between the winds of the pulsar and companion, where the shock shapes the eclipsing medium but had not been described in detail in previous works. The model is further used to explain the variations of the flux density and dispersion measure of three BW pulsars (i.e., PSR B1957+20, J2055+3829, and J2051-0827) detected by the Five-hundred-meter Aperture Spherical radio Telescope. Consequently, we constrained the parameters of the three BW systems such as the inclination angles and true anomalies of the observer as well as the mass-loss rates and wind velocity of the companion stars. With the help of these constraints, it is expected that magnetic fields of companion stars and even masses of pulsars could further be determined as some extra observation can be achieved in the future.
摘要：
FRB 180916.J0158+65 is a well-known repeating fast radio burst with a period (|$16.35~\rm d$|) and an active window (|$5.0~\rm d$|). We give out the statistical results of the dispersion measures and waiting times of bursts of FRB 180916.J0158+65. We find the dispersion measures at the different frequencies show a bimodal distribution. The peaking dispersion measures of the left mode of the bimodal distributions increase with frequency, but the right one is inverse. The waiting times also present the bimodal distribution, peaking at 0.05622 and 1612.91266 s. The peaking time is irrelevant to the properties of bursts, either for the preceding or subsequent burst. By comparing the statistical results with possible theoretical models, we suggest that FRB 180916.J0158+65 suffered from the plasma lensing effects in the propagation path. Moreover, this source may be originated from a highly magnetized neutron star in a high-mass X-ray binary.
摘要：
短时标伽马射线暴(简称短暴) GRB 170817A是人类发现的第一个与引力波事件成协的伽马暴,为深入研究短暴的发生机制提供了宝贵的机会,其中它的多波段余辉辐射很可能展示了喷流的角向结构.而有关短暴的大样本统计研究表明,如果用高斯函数来唯象描述喷流结构,很可能需要引入两个高斯函数才能够把GRB 170817A的辐射和其他普通的短暴统一起来.换言之, GRB 170817A的瞬时辐射很可能来自具有更大张角的额外喷流成分.因此,为了检验这种双高斯喷流结构和GRB 170817A余辉数据的相容性,本文计算了该喷流结构在偏轴观测下的多波段余辉,发现外高斯成分的引入能够很好地解释GRB 170817A余辉数据的早期上扬趋势.在此基础上,我们还计算了喷流在并合抛射物中的传播和突破过程,表明这些过程可以自然导致观测限制所得的双高斯喷流结构,从而展现出了模型的整体自洽性.此外,对喷流传播过程的观测限制也为我们了解并合抛射物的性质提供了新的线索.
作者机构：
[Yu, Yun-Wei; Wu, Guang-Lei] 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.;[Li, Shao-Ze] Hebei Univ, Coll Phys Sci & Technol, Baoding 071002, Peoples R China.
通讯机构：
[Yun-Wei Yu] K;Key Laboratory of Quark and Lepton Physics (Central China Normal University), Ministry of Education, Wuhan 430079, China<&wdkj&>Institute of Astrophysics, Central China Normal University, Wuhan 430079, China<&wdkj&>Author to whom correspondence should be addressed.
关键词：
kilonova/mergernova;magnetar;shock breakout
摘要：
A rapidly rotating and highly magnetized remnant neutron star (NS; magnetar) could survive from a merger of double NSs and drive a powerful relativistic wind. The early interaction of this wind with the previous merger ejecta can lead to shock breakout (SBO) emission mainly in ultraviolet and soft X-ray bands, which provides an observational signature for the existence of the remnant magnetar. Here, we investigate the effect of an anisotropic structure of the merger ejecta on the SBO emission. It is found that the bolometric light curve of the SBO emission can be broadened, since the SBO can occur at different times for different directions. In more detail, the profile of the SBO light curve can be highly dependent on the ejecta structure and, thus, we can in principle use the SBO light curves to probe the structure of the merger ejecta in future.
作者机构：
[Yu, Yun-Wei; Liu, Liang-Duan; Zhang, Zhen-Dong] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;[Yu, Yun-Wei; Liu, Liang-Duan] Cent China Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Peoples R China.
摘要：
A millisecond magnetar engine has been widely suggested to exist in gamma-ray burst (GRB) phenomena, in view of its substantial influences on the GRB afterglow emission. In this paper, we investigate the effects of the magnetar engine on the supernova (SN) emission, which is associated with long GRBs and, specifically, confront the model with the observational data of SN 2006aj/GRB 060218. SN 2006aj is featured by its remarkable double-peaked ultraviolet-optical (UV-opt) light curves. By fitting these light curves, we demonstrate that the first peak can be well accounted for by the breakout emission of the shock driven by the magnetar wind, while the primary supernova emission is also partly powered by the energy injection from the magnetar. The magnetic field strength of the magnetar is constrained to be similar to 10(15) G, which is in good agreement with the common results inferred from the afterglow emission of long GRBs. In more detail, it is further suggested that the UV excess in the late emission of the supernova could also be due to the leakage of the nonthermal emission of the pulsar wind nebula, if some ad hoc conditions can be satisfied. The consistency between the model and the SN 2006aj observation indicates that the magnetar engine is likely to be ubiquitous in the GRB phenomena and even further intensify their connection with the phenomena of superluminous supernovae.
作者机构：
[Zhu, Jin-Ping] Peking Univ, Sch Phys, Dept Astron, Beijing 100871, Peoples R China.;[Yang, Yuan-Pei] Yunnan Univ, South Western Inst Astron Res, Kunming 650500, Yunnan, Peoples R China.;[Zhang, Bing] Univ Nevada, Nevada Ctr Astrophys, Las Vegas, NV 89154 USA.;[Zhang, Bing] Univ Nevada, Dept Phys & Astron, Las Vegas, NV 89154 USA.;[Gao, He] Beijing Normal Univ, Dept Astron, Beijing 100875, Peoples R China.
摘要：
In the first work of this series, we adopt a GW170817-like viewing-angle-dependent kilonova model and the standard afterglow model with a light-curve distribution based on the properties of cosmological short gamma-ray burst afterglows to simulate the luminosity functions and color evolution of both kilonovae and optical afterglow emissions from binary neutron star (BNS) mergers. We find that similar to 10% of the nearly-on-axis afterglows are brighter than the associated kilonovae at the peak time. These kilonovae would be significantly polluted by the associated afterglow emission. Only at large viewing angles with sin theta(v) greater than or similar to 0.20, the electromagnetic signals of most BNS mergers would be kilonova-dominated and some off-axis afterglows may emerge at similar to 5-10 days after the mergers. At a brightness dimmer than similar to 23-24 mag, according to their luminosity functions, the number of afterglows is much larger than that of kilonovae. Because the search depth of the present survey projects is <22 mag, the number of afterglow events that are detected via serendipitous observations would be much higher than that of kilonova events, consistent with the current observations. For the foreseeable survey projects (e.g., Mephisto, WFST, and LSST), whose search depths can reach greater than or similar to 23-24 mag, the detection rate of kilonovae could have the same order of magnitude as afterglows. We also find that it may be difficult to use the fading rate in a single band to directly identify kilonovae and afterglows among various fast-evolving transients by serendipitous surveys. However, the color evolution between the optical and infrared bands can identify them because the color evolution patterns of these phenomena are unique compared with those of other fast-evolving transients.
作者机构：
[Yu, Yun-Wei; Liu, Liang-Duan; Liu, Jian-Feng] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.;[Yu, Yun-Wei; Liu, Liang-Duan; Liu, Jian-Feng] Cent China Normal Univ, Minist Educ, Key Lab Quark & Lepton Phys, Wuhan 430079, Peoples R China.;[Zhu, Jin-Ping] Peking Univ, Sch Phys, Dept Astron, Beijing 100871, Peoples R China.;[Zhang, Bing] Univ Nevada, Nevada Ctr Astrophys, Las Vegas, NV 89154 USA.;[Zhang, Bing] Univ Nevada, Dept Phys & Astron, Las Vegas, NV 89154 USA.
摘要：
We fit the multiband lightcurves of 40 fast blue optical transients (FBOTs) with the magnetar engine model. The mass of the FBOT ejecta, the initial spin period, and the polar magnetic field of the FBOT magnetars are respectively constrained to , , and . The wide distribution of the value of Bp spreads the parameter ranges of the magnetars from superluminous supernovae (SLSNe) to broad-line Type Ic supernovae (SNe Ic-BL; some are observed to be associated with long-duration gamma-ray bursts), which are also suggested to be driven by magnetars. Combining FBOTs with the other transients, we find a strong universal anticorrelation of , indicating they could share a common origin. To be specific, it is suspected that all of these transients originate from the collapse of extremely stripped stars in close binary systems, but with different progenitor masses. As a result, FBOTs distinguish themselves by their small ejecta masses with an upper limit of ∼1 M⊙, which leads to an observational separation in the rise time of the lightcurves of ∼10 days. In addition, FBOTs together with SLSNe can be separated from SNe Ic-BL by an empirical line in the Mpeak–trise plane corresponding to an energy requirement of the mass of 56Ni of ∼0.3Mej, where Mpeak is the peak absolute magnitude of the transients and trise is the rise time.
通讯机构：
[Shao-Lin Xiong] K;[Yun-Wei Yu] I;Institute of Astrophysics, Central China Normal University , Wuhan 430079, China<&wdkj&>Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences , 19B Yuquan Road, Beijing 100049, China
关键词：
methods: data analysis;stars: magnetars;X-ray: bursts
摘要：
Since FRB 200428 has been found to be associated with an X-ray burst from the Galactic magnetar SGR J1935+2154, it is interesting to explore whether the magnetar bursts also follow the similar active periodic behaviour as some repeating FRBs. Previous studies show that there is possible period of about 230 days in SGR J1935+2154 bursts. Here, we collected an updated burst sample from SGR J1935+2154, including all bursts reported by Fermi/GBM and GECAM till 2022 January. We also developed a targeted search pipeline to reveal more bursts from SGR J1935+2154 in the Fermi/GBM data from 2008 August to 2014 December (i.e. before the first burst detected by Swift/BAT). With this burst sample, we re-analysed the possible periodicity of SGR J1935+2154 bursts using the Period Folding and Lomb-Scargle Periodogram methods. Our results show that the periodicity similar to 238 days reported in literature is probably fake and the observation effects may introduce false periods (i.e. 55 days) according to simulation tests. We find that, for the current burst sample, the most probable period is 126.88 +/- 2.05 days, which could be interpreted as the precession of the magnetar. However, we note that the whole burst history is very complicated and difficult to be perfectly accommodated with any period reported thus far, therefore more monitoring observations of SGR J1935+2154 are required to test any periodicity hypothesis.
作者机构：
[Zhu, Jin-Ping] Peking Univ, Sch Phys, Dept Astron, Beijing 100871, Peoples R China.;[Yang, Yuan-Pei] Yunnan Univ, South Western Inst Astron Res, Kunming, Yunnan, Peoples R China.;[Zhang, Bing] Univ Nevada, Dept Phys & Astron, Las Vegas, NV 89154 USA.;[Liu, Liang-Duan; Gao, He] Beijing Normal Univ, Dept Astron, Beijing 100875, Peoples R China.;[Yu, Yun-Wei] Cent China Normal Univ, Inst Astrophys, Wuhan 430079, Peoples R China.
摘要：
White dwarfs (WDs) embedded in the gaseous disks of active galactic nuclei (AGNs) can rapidly accrete materials from these disks and grow in mass to reach, or even exceed, the Chandrasekhar limit. Binary WD (BWD) mergers are also believed to occur in AGN accretion disks. We study observational signatures from these events. We suggest that mass-accreting WDs and BWD mergers in AGN disks can lead to thermonuclear explosions that drive an ejecta shock breakout from the disk surface and power a slow-rising, relatively dim Type Ia supernova (SN). It is possible that such SNe Ia may be outshone by the emission of the AGN disk around a supermassive black hole (BH) with a mass of M (SMBH) greater than or similar to 10(8) M (circle dot). In addition, accretion-induced collapses (AICs) of WDs in AGN disks may sometimes occur, which may form highly magnetized millisecond neutron stars (NSs). The subsequent spindown process of this nascent magnetar can deposit its rotational energy into the disk materials, resulting in a magnetar-driven shock breakout and a luminous magnetar-powered transient. We show that such an AIC event could power a rapidly evolving and luminous transient for a magnetic field of B similar to 10(15) G. The rising time and peak luminosity of the transient, powered by a magnetar with B similar to 10(14) G, are predicted to have similar properties to those of superluminous SNe. AIC events taking place in the inner parts of disks around relatively less massive supermassive BHs (M (SMBH) less than or similar to 10(8) M (circle dot)) are more likely to power transients that are much brighter than the AGN disk emission, and hence easily identified.
作者机构：
[Xiao-Yu Lai] Department of Physics and Astronomy,Hubei University of Education,Wuhan 430205,China;[Xiao-Yu Lai] Research Center for Astronomy,Hubei University of Education,Wuhan 430205,China;[Cheng-Jun Xia] School of Information Science and Engineering,NingboTech University,Ningbo 315100,China;Institute of Astrophysics,Central China Normal University,Wuhan 430079,China;School of Physics,Peking University,Beijing 100871,China
关键词：
dense matter-equation of state;pulsars: general
摘要：
The state of supranuclear matter in compact stars remains puzzling, and it is argued that pulsars could be strangeon stars. The consequences of merging double strangeon stars are worth exploring, especially in the new era of multi-messenger astronomy. To develop the "strangeon kilonova" scenario proposed in Paper I, we make a qualitative description about the evolution of ejecta and light curves for merging double strangeon stars. In the hot environment of the merger, the strangeon nuggets ejected by tidal disruption and hydrodynamical squeezing would suffer from evaporation, in which process particles, such as strangeons, neutrons and protons, are emitted. Taking into account both the evaporation of strangeon nuggets and the decay of strangeons, most of the strangeon nuggets would turn into neutrons and protons, within dozens of milliseconds after being ejected. The evaporation rates of different particles depend on temperature, and we find that the ejecta could end up with two components, with high and low opacity respectively. The high opacity component would be in the directions around the equatorial plane, and the low opacity component would be in a broad range of angular directions. The bolometric light curves show that the spin-down power of the long-lived remnant would account for the whole emission of kilonova AT2017gfo associated with GW170817, if the total ejected mass ∼ 10−3 M⊙. The detailed picture of merging double strangeon stars is expected to be tested by future numerical simulations.
摘要：
1FGL J1018.6–5856 is a high mass gamma-ray binary containing a compact object orbiting around a massive star with a period of 16.544 d. If the compact object is a pulsar, non-thermal emissions are likely produced by electrons accelerated at the termination shock, and may also originate from the magnetosphere and the un-shocked wind of the pulsar. In this paper, we investigate the non-thermal emissions from the wind and the shock with different viewing geometries and study the multi-wavelength emissions from 1FGL J1018.6–5856. We present the analysis results of the Fermi/LAT using nearly 10 years of data. The phase-resolved spectra indicate that the Ge V emissions comprise a rather steady component that does not vary with orbital motion and a modulated component that shows flux maximum around inferior conjunction. The ke V/Te V light curves of 1FGL J1018.6–5856 also exhibit a sharp peak around inferior conjunction, which are attributed to the boosted emission from the shock, while the broad sinusoidal modulations could be originating from the deflected shock tail at a larger distance. The modulations of Ge V flux are likely caused by the boosted synchrotron emission from the shock and the IC emission from the unshocked pulsar wind, while the steady component comes from the outer gap of the pulsar magnetosphere.Finally, we discuss the similarities and differences of 1FGL J1018.6–5856 with other binaries, like LS 5039.
