المؤلفون: Meng, Yan-Zhi, Wang, Xiangyu Ivy, Liu, Zi-Ke

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: The radiation mechanism (thermal photosphere or magnetic synchrotron) and the progenitor of gamma-ray burst (GRB) are under hot debate. Recently discovered, the prompt long-duration ($\sim$ 10 s, normally from the collapse of massive stars) property of GRB 211211A strongly conflicts with its association with a kilonova (normally from the merger of two compact objects, NS-NS, NS-BH, or NS-WD, duration $\lesssim$ 2 s). In this paper, we find the probability photosphere model with a structured jet can satisfactorily explain this peculiar long duration, through the duration stretching effect ($\sim$ 3 times) on the intrinsic longer ($\sim$ 3 s) duration of NS-BH (neutron star and black hole) merger, the observed empirical 2SBPL spectrum (with soft low-energy index $\alpha$ of $\sim$ -1) and its evolution. Also, much evidence of the NS-BH merger origin is found, especially the well fit of the afterglow-subtracted optical-NIR light curves by the significant thermal cocoon emission and the sole thermal red kilonova component. Finally, a convincing new explanation for the X-ray afterglow plateau is revealed.
Comment: 38 pages, 17 figures, 2 tables. Under review at Nature Communications

الوصول الحر: http://arxiv.org/abs/2304.00893Test

المؤلفون: Yang, Jun, Zhao, Xiao-Hong, Yan, Zhenyu, Wang, Xiangyu I., Zhang, Yan-Qiu, An, Zheng-Hua, Cai, Ce, Li, Xin-Qiao, Li, Zihan, Liu, Jia-Cong, Liu, Zi-Ke, Ma, Xiang, Meng, Yan-Zhi, Peng, Wen-Xi, Qiao, Rui, Shao, Lang, Song, Li-Ming, Tan, Wen-Jun, Wang, Ping, Wang, Chen-Wei, Wen, Xiang-Yang, Xiao, Shuo, Xue, Wang-Chen, Yang, Yu-han, Yin, Yihan, Zhang, Bing, Zhang, Fan, Zhang, Shuai, Zhang, Shuang-Nan, Zheng, Chao, Zheng, Shi-Jie, Xiong, Shao-Lin, Zhang, Bin-Bin

المصدر: ApJL 947 L11 (2023)

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: The brightest Gamma-ray burst, GRB 221009A, has spurred numerous theoretical investigations, with particular attention paid to the origins of ultra-high energy TeV photons during the prompt phase. However, analyzing the mechanism of radiation of photons in the $\sim$MeV range has been difficult because the high flux causes pile-up and saturation effects in most GRB detectors. In this letter, we present systematic modeling of the time-resolved spectra of the GRB using unsaturated data obtained from Fermi/GBM (precursor) and SATech-01/GECAM-C (main emission and flare). Our approach incorporates the synchrotron radiation model, which assumes an expanding emission region with relativistic speed and a global magnetic field that decays with radius, and successfully fits such a model to the observational data. Our results indicate that the spectra of the burst are fully in accordance with a synchrotron origin from relativistic electrons accelerated at a large emission radius. The lack of thermal emission in the prompt emission spectra supports a Poynting-flux-dominated jet composition.
Comment: 12 pages, 6 figures, 2 tables. Accepted for publication in ApJL

الوصول الحر: http://arxiv.org/abs/2303.00898Test

المؤلفون: Zhang, Zijian, Yin, Yihan, Wang, Chenyu, Wang, Xiangyu Ivy, Yang, Jun, Meng, Yan-Zhi, Liu, Zi-Ke, Chen, Guo-Yin, Fu, Xiaoping, Gao, Huaizhong, Li, Sihao, Liu, Yihui, Long, Xiangyun, Ma, Yong-Chang, Pan, Xiaofan, Sun, Yuanze, Wu, Wei, Yang, Zirui, Ye, Zhizhen, Yu, Xiaoyu, Zhao, Shuheng, Zheng, Xutao, Zhou, Tao, Tang, Qing-Wen, Yan, Qiurong, Zhou, Rong, Wang, Zhonghai, Feng, Hua, Zeng, Ming, Zhang, Bin-Bin

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Jet precession has previously been proposed to explain the apparently repeating features in the light curves of a few gamma-ray bursts (GRBs). In this {\it Letter}, we further apply the precession model to a bright GRB 220408B by examining both its temporal and spectral consistency with the predictions of the model. As one of the recently confirmed GRBs observed by our GRID CubeSat mission, GRB 220408B is noteworthy as it exhibits three apparently similar emission episodes. Furthermore, the similarities are reinforced by their strong temporal correlations and similar features in terms of spectral evolution and spectral lags. Our analysis demonstrates that these features can be well explained by the modulated emission of a Fast-Rise-Exponential-Decay (FRED) shape light curve intrinsically produced by a precessing jet with a precession period of $18.4 \pm 0.2$ seconds, a nutation period of $11.1 \pm 0.2$ seconds and viewed off-axis. This study provides a straightforward explanation for the complex yet similar multi-episode GRB light curves.
Comment: 11 pages, 3 tables, 8 figures

الوصول الحر: http://arxiv.org/abs/2302.03215Test

المؤلفون: Wei, Jin-Nan, Liu, Zi-Ke, Wei, Jun-Jie, Zhang, Bin-Bin, Wu, Xue-Feng

المصدر: Universe 2022, 8(10), 519

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology

الوصف: The observed spectral lags of gamma-ray bursts (GRBs) have been widely used to explore possible violations of Lorentz invariance. However, these studies were generally performed by concentrating on the rough time lag of a single highest-energy photon and ignoring the intrinsic time lag at the source. A new way to test nonbirefringent Lorentz-violating effects has been proposed by analyzing the multi-photon spectral-lag behavior of a GRB that displays a positive-to-negative transition. This method gives both a plausible description of the intrinsic energy-dependent time lag and comparatively robust constraints on Lorentz-violating effects. In this work, we conduct a systematic search for Lorentz-violating photon dispersion from the spectral-lag transition features of 32 GRBs. By fitting the spectral-lag data of these 32 GRBs, we place constraints on a variety of isotropic and anisotropic Lorentz-violating coefficients with mass dimension $d=6$ and $8$. While our dispersion constraints are not competitive with existing bounds, they have the promise to complement the full coefficient space.
Comment: 17 pages, 2 figures, 2 tables. Published by Universe. Constribution to the Special Issue "Advances in Astrophysics and Cosmology-in Memory of Prof. Tan Lu"

الوصول الحر: http://arxiv.org/abs/2210.03897Test

المؤلفون: Yang, Jun, Ai, Shunke, Zhang, Bin-Bin, Zhang, Bing, Liu, Zi-Ke, Wang, Xiangyu Ivy, Yang, Yu-Han, Yin, Yi-Han, Li, Ye, Lü, Hou-Jun

المصدر: Nature, 612, 232-235 (2022)

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: It is generally believed that long-duration gamma-ray bursts (GRBs) are associated with massive star core-collapse, whereas short-duration GRBs are associated with mergers of compact star binaries. However, growing observations have suggested that oddball GRBs do exist, and multiple criteria (prompt emission properties, supernova/kilonova associations, and host galaxy properties) rather than burst duration only are needed to classify GRBs physically. A previously reported long-duration burst, GRB 060614, could be viewed as a short GRB with extended emission if it were observed at a larger distance and was associated with a kilonova-like feature. As a result, it belongs to the Type-I (compact star merger) GRB category and is likely of the binary neutron star merger origin. Here we report a peculiar long-duration gamma-ray burst, GRB 211211A, whose prompt emission properties in many aspects differ from all known Type-I GRBs, yet its multi-band observations suggest a non-massive-star origin. In particular, significant excess emission in both optical and near-infrared wavelengths has been discovered, which resembles kilonova emission as observed in some Type-I GRBs. These observations point towards a new progenitor type of GRBs. A scenario invoking a white dwarf-neutron star merger with a post-merger magnetar engine provides a self-consistent interpretation for all the observations, including prompt gamma-rays, early X-ray afterglow, as well as the engine-fed kilonova emission.
Comment: Updated; Authors' version. 44 pages, 8 figures, 6 tables

الوصول الحر: http://arxiv.org/abs/2204.12771Test

المؤلفون: Tu, Zuo-Lin, Wu, Qin, Wang, Wenbo, Zhang, G. Q., Liu, Zi-Ke, Wang, F. Y.

مصطلحات موضوعية: Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics

الوصف: In this work, six convolutional neural networks (CNNs) have been trained based on %different feature images and arrays from the database including 15,638 superflare candidates on solar-type stars, which are collected from the three-years observations of Transiting Exoplanet Survey Satellite ({\em TESS}). These networks are used to replace the artificially visual inspection, which was a direct way to search for superflares, and exclude false positive events in recent years. Unlike other methods, which only used stellar light curves to search superflare signals, we try to identify superflares through {\em TESS} pixel-level data with lower risks of mixing false positive events, and give more reliable identification results for statistical analysis. The evaluated accuracy of each network is around 95.57\%. After applying ensemble learning to these networks, stacking method promotes accuracy to 97.62\% with 100\% classification rate, and voting method promotes accuracy to 99.42\% with relatively lower classification rate at 92.19\%. We find that superflare candidates with short duration and low peak amplitude have lower identification precision, as their superflare-features are hard to be identified. The database including 71,732 solar-type stars and 15,638 superflare candidates from {\em TESS} with corresponding feature images and arrays, and trained CNNs in this work are public available.
Comment: Published in ApJ, 27 pages, 11 figures, 3 tables

الوصول الحر: http://arxiv.org/abs/2204.04019Test

المؤلفون: Liu, Zi-Ke, Zhang, Bin-Bin, Meng, Yan-Zhi

المصدر: 2022,ApJ,935,79

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: The positive-to-negative transition of spectral lag is an uncommon feature reported in a small number of GRBs. An application of such a feature has been made to constrain the critical quantum gravity energy ($E_{\rm QG}$) of the light photons under the hypothesis that the Lorentz invariance might be violated. Motivated by previous case studies, this paper systematically examined the up-to-date Fermi/GBM GRB sample for the lag transition feature to establish a comprehensive physical limit on the Lorentz Invariance Violation (LIV). This search resulted in 32 GRBs with redshift available, which exhibit the lag-transition phenomenon. We first fit each of the lag-E relations of the 32 GRBs with an empirical smoothly broken power law function, and found that the lag transition occurs typically at about 400 keV. We then implemented the LIV effect into the fit, which enabled us to constrain the lower limit of the linear and quadratic values of $E_{\rm QG}$, which are typically distributed at $1.5\times 10^{14}$ GeV and $8\times 10^{5}$ GeV, respectively.
Comment: 12 pages, 3 tables, 39 figures

الوصول الحر: http://arxiv.org/abs/2202.09999Test

المؤلفون: Lin, Shi-Jie, Li, An, Gao, He, Lin, Lin, Zhang, Bin-Bin, Liu, Zi-Ke, Zou, Jin-Hang, Zhang, Zhao, Zhou, Huan, Li, Zheng-Xiang, Lan, Lin

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: Millilensing of Gamma-Ray Bursts (GRBs) is expected to manifest as multiple emission episodes in a single triggered GRB with similar light-curve patterns and similar spectrum properties. Identifying such lensed GRBs could help improve constraints on the abundance of compact dark matter. Here we present a systemic search for millilensing among 3000 GRBs observed by the \textit{Fermi} GBM up to 2021 April. Eventually we find 4 interesting candidates by performing auto-correlation test, hardness test, and time-integrated/resolved spectrum test to the whole sample. GRB 081126A and GRB 090717A are ranked as the first class candidate based on their excellent performance both in temporal and spectrum analysis. GRB 081122A and GRB 110517B are ranked as the second class candidates (suspected candidates), mainly because their two emission episodes show clear deviations in part of the time-resolved spectrum or in the time-integrated spectrum. Considering a point mass model for the gravitational lens, our results suggest that the density parameter of lens objects with mass $M_{\rm L}\sim10^{6} M_{\odot}$ is larger than $1.5\times10^{-3}$.
Comment: Accepted for publication in The Astrophysical Journal

الوصول الحر: http://arxiv.org/abs/2112.07288Test

المؤلفون: Peng, Zong-Kai, Liu, Zi-Ke, Zhang, Bin-Bin, Gao, He

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: The Type II gamma-ray burst (GRB) 200826A challenges collapsar models by questioning how they can generate a genuinely short-duration event. The other Type I GRB 211211A confused us with a kilonova signature observed in the afterglow of a \textit{long} burst. Here, we propose a comprehensive model in which both bursts are the results of the collapse of Thorne-\.Zytkow-like Objects (TZlOs). The TZlO consists of a central neutron star (NS), with a dense white dwarf (WD) material envelope, which is formed as the aftermath of a WD-NS coalescence. We find that the characteristics of the resultant GRBs depend on whether the TZlO collapses immediately following the WD-NS merger or not. Additionally, the observational properties of the consequent GRBs manifest variations contingent upon whether the collapse of the TZlO results in a magnetar or a black hole. We also show that our model is consistent with the observations of GRB 211211A and GRB 200826A. Specifically, the optical excess in GRB 211211A can be attributed to an engine-fed kilonova, while the \textit{supernova bump} in GRB 200826A is likely due to the collision between the ejecta and the disk wind shell.
Comment: 16 pages, 3 figures, 2 tables. Accepted for publication in ApJ

الوصول الحر: http://arxiv.org/abs/2109.06041Test

المؤلفون: Wang, Xiangyu Ivy, Zheng, Xutao, Xiao, Shuo, Yang, Jun, Liu, Zi-Ke, Yang, Yu-Han, Zou, Jin-Hang, Zhang, Bin-Bin, Zeng, Ming, Xiong, Shao-Lin, Feng, Hua, Song, Xin-Ying, Wen, Jiaxing, Xu, Dacheng, Chen, Guo-Yin, Ni, Yang, Wu, Yu-Xuan, Zhang, Zi-Jian, Cai, Ce, Cang, Jirong, Deng, Yun-Wei, Gao, Huaizhong, Kong, De-Feng, Huang, Yue, Li, Cheng-kui, Li, Hong, Li, Xiao-Bo, Liang, En-Wei, Lin, Lin, Liu, Yihui, Long, Xiangyun, Lu, Dian, Luo, Qi, Ma, Yong-Chang, Meng, Yan-Zhi, Peng, Wen-Xi, Qiao, Rui, Song, Li-Ming, Tian, Yang, Wang, Pei-Yuan, Wang, Ping, Wang, Xiang-Gao, Xu, Sheng, Yang, Dongxin, Yin, Yi-Han, Zeng, Weihe, Zeng, Zhi, Zhang, Ting-Jun, Zhang, Yuchong, Zhang, Zhao, Zhang, Zhen

المصدر: 2021, ApJ, 922, 237

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena

الوصف: The Chinese CubeSat Mission, Gamma Ray Integrated Detectors (GRID), recently detected its first gamma-ray burst, GRB 210121A, which was jointly observed by the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM). This burst is confirmed by several other missions, including \fermi and \textit{Insight}-HXMT. We combined multi-mission observational data and performed a comprehensive analysis of the burst's temporal and spectral properties. Our results show that the burst is relatively special in its high peak energy, thermal-like low energy indices, and large fluence. By putting it to the $E_{\rm p}$-$E_{\rm\gamma, iso}$ relation diagram with assumed distance, we found this burst can be constrained at the redshift range of [0.3,3.0]. The thermal spectral component is also confirmed by the direct fit of the physical models to the observed spectra. Interestingly, the physical photosphere model also constrained a redshift of $z\sim$ 0.3 for this burst, which help us to identify a host galaxy candidate at such a distance within the location error box. Assuming the host galaxy is real, we found the burst can be best explained by the photosphere emission of a typical fireball with an initial radius of $r_0\sim$ 3.2 $\times 10^7$ cm.
Comment: ApJ accpeted; 12 pages, 11 figures, 3 tables

الوصول الحر: http://arxiv.org/abs/2107.10452Test