γ暴高能辐射的研究一直是天体物理和宇宙线物理的研究热点,但在100 Ge V及以上能区至今尚未获得确定的观测结果。位于西藏羊八井宇宙线观测站(海拔4 300 m)的ARGO-YBJ实验具有高海拔、大视场等特点,其阈能约几百个Ge V,在探测高能γ暴...γ暴高能辐射的研究一直是天体物理和宇宙线物理的研究热点,但在100 Ge V及以上能区至今尚未获得确定的观测结果。位于西藏羊八井宇宙线观测站(海拔4 300 m)的ARGO-YBJ实验具有高海拔、大视场等特点,其阈能约几百个Ge V,在探测高能γ暴方面具有独特的优势。利用ARGO-YBJ实验中的"双前峰面"事例,可降低探测器的阈能达几十个Ge V,提高实验探测γ暴的灵敏度。作者研究了ARGO-YBJ实验中的"双前峰面"事例,并通过Monte Carlo模拟,估算出利用该类事例探测高能区(10—100 Ge V)γ暴所需要的最低能流为10-4—10-3erg.cm^(-2)。展开更多
[Objective] Grb-AST7 concatemer including 17 copies of Grb-AST7 was constructed by ＂self template-primer＂ PCR. [Method] Two primers of which were synthesized based on the amino acid sequence of Gryllus bimaculatus’...[Objective] Grb-AST7 concatemer including 17 copies of Grb-AST7 was constructed by ＂self template-primer＂ PCR. [Method] Two primers of which were synthesized based on the amino acid sequence of Gryllus bimaculatus’ Grb-AST7. [Result] Through splicing, a length of 570 bp, containing 17 copies of the Grb-AST7 gene repeats were obtained. Appropriate primer splicing conditions were as follows：splice time 20 min, 25 μl PCR system, containing 2 μl template. [Conclusion] The results laid foundation for the future studies on Grb-AST7 gene expression and bio-activity analysis.展开更多
With the successful launch of Swift satellite, more and more data of early X-ray afterglows from short gamma-ray bursts have been collected. Some interesting features such as unusual afterglow light curves and unexpec...With the successful launch of Swift satellite, more and more data of early X-ray afterglows from short gamma-ray bursts have been collected. Some interesting features such as unusual afterglow light curves and unexpected X-ray flares are revealed. Especially, in some cases, there is a flat segment in the X-ray afterglow light curve. Here we present a simplified model in which we believe that the flattening part is due to energy injection from the central engine. We assume that this energy injection arises from the magnetic dipole radiation of a millisecond pulsar formed after the merger of two neutron stars. We check this model with the short GRB 060313. Our numerical results suggest that energy injection from a millisecond magnetar could make part of the X-ray afterglow light curve flat.展开更多
The angular distribution of gamma-ray burst（GRB）jets is not yet clear.The observed luminosity of GRB 170817A is the lowest among all known short GRBs,which is best explained by the fact that our line of sight is out...The angular distribution of gamma-ray burst（GRB）jets is not yet clear.The observed luminosity of GRB 170817A is the lowest among all known short GRBs,which is best explained by the fact that our line of sight is outside of the jet opening angle,θ_（obs）〉θ_j,whereθ_（obs） is the angle between our line of sight and the jet axis.As inferred by gravitational wave observations,as well as radio and X-ray afterglow modeling of GRB 170817A,it is likely that θ_（obs）~20°–28°.In this work,we quantitatively consider two scenarios of angular energy distribution of GRB ejecta：a top-hat jet and a structured jet with a power law index s.For the top-hat jet model,we get a large θ_j（e.g.,θ_j〉10°）,a rather high local （i.e., z 〈 0.01） short GRB rate ~8–15×10~3 Gpc^（-3）yr~（-1（（estimated to be 90~1850 Gpc^（-3）yr^（-1） in Fong et al.）and an extremely high（on-axis,V（~500 ke V for a typical short GRB）.For the structured jet model,we use θ_（obs） to give limits on s and θ_j for typical on-axis luminosity of a short GRB（e.g.,10^（49）erg s（-1） 1051erg s（-1））,and a low on-axis luminosity case（e.g.,1049erg s（-1））gives more reasonable values of s.The structured jet model is more feasible for GRB170817A than the top-hat jet model due to the rather high local short GRB rate,and the extremely high on-axis E_（peak,0） almost rules out the top-hat jet model.GRB 170817A is likely a low on-axis luminosity GRB（1049erg s（-1））with a structured jet.展开更多
We report the optical observations of GRB 121011 A by the 0.8m TNT facility at Xinglong observatory, China. The light curve of the optical afterglow shows a smooth and featureless bump during the epoch of;30 s and;000...We report the optical observations of GRB 121011 A by the 0.8m TNT facility at Xinglong observatory, China. The light curve of the optical afterglow shows a smooth and featureless bump during the epoch of;30 s and;000 s with a rising index of 1.57 ± 0.28 before the break time of 539 ± 44 s, and a decaying index of about 1.29 ± 0.07 up to the end of our observations. Moreover, the X-ray light curve decays in a single power-law with a slope of about 1.51 ± 0.03 observed by XRT onboard Swift from 100 s to about 10 000 s after the burst trigger. The featureless optical light curve could be understood as an onset process under the external-shock model. The typical frequency has been below or near the optical one before the deceleration time, and the cooling frequency is located between the optical and X-ray wavelengths. The external medium density has a transition from a mixed stage of ISM and wind-type medium before the peak time to the ISM at the later phase. The joint-analysis of X-ray and optical light curves shows that the emissions from both frequencies are consistent with the prediction of the standard afterglow model without any energy injections, indicating that the central engine has stopped its activity and does not restart anymore after the prompt phase.展开更多
This paper is the second instalment in our study of the observed time delay in the arrival times of radio photons emanating from Gamma Ray Bursts (GRBs). The mundane assumption in contemporary physics as to the cause ...This paper is the second instalment in our study of the observed time delay in the arrival times of radio photons emanating from Gamma Ray Bursts (GRBs). The mundane assumption in contemporary physics as to the cause of these pondersome time delays is that they are a result of the photon being endowed with a non-zero mass. While we do not rule out the possibility of a non-zero mass for the photon, our working assumption is that the major cause of these time delays may very well be that these photons are travelling in a rarefied cosmic plasma in which the medium’s electrons interact with the electric component of the Photon, thus generating tiny currents that lead to dispersion, hence, a frequency-dependent speed of Light (FDSL). In the present instalment, we “improve” on the model presented in the first instalment by dropping the assumption that the resultant pairs of these radio photons leave the shock front simultaneously. The new assumption of a non-simultaneous— albeit systematic—emission of these photon pairs allows us to obtain a much more convincing and stronger correlation in the time delay. This new correlation allows us to build a unified model for the four GRBs in our sample using a relative distance correction mechanism. The new unified model allows us to obtain as our most significant result a value for the frequency equivalence of the interstellar medium (ISM)’s conductance ν* ~ 1.500 ± 0.009 Hzand also an independent distance measure to the GRBs where we obtain for our four GRB samples an average distance of: ~69.40 ± 0.10, 40.00 ± 0.00, 58.40 ± 0.40, and 86.00 ± 1.00 Mpc, for GRB 030329, 980425, 000418 and 021004 respectively.展开更多
Swift GRB 100418A is a long burst at z = 0.624 without detection of any associated supernova （SN）. Its light curves in both the prompt and afterglow phases are similar to GRB 060614, a nearby long GRB without an ass...Swift GRB 100418A is a long burst at z = 0.624 without detection of any associated supernova （SN）. Its light curves in both the prompt and afterglow phases are similar to GRB 060614, a nearby long GRB without an associated SN. We analyze the observational data of this event and discuss the possible origins of its multiwavelength emission. We show that its joint light curve at 1 keV derived from Swift BAT and XRT observations is composed of two distinguished components. The first component, whose spectrum is extremely soft （Γ = 4.32）, ends with a steep decay segment, indicating the internal origin of this component. The second component is a slowly-rising, broad bump which peaks at ～ 10 5 s post the BAT trigger. Assuming that the late bump is due to onset of the afterglow, we derive the initial Lorentz factor （Γ 0 ） of the GRB fireball and find that it significantly deviates from the relation between the Γ 0 and isotropic gamma-ray energy derived from typical GRBs. We also check whether it follows the same anti-correlation between X-ray luminosity and the break time observed in the shallow decay phase of many typical GRBs, which is usually regarded as a signal of late energy injection from the GRB central engine. However, we find that it does not obey this correlation. We propose that the late bump could be contributed by a two-component jet. We fit the second component with an off-axis jet model for a constant medium density and find the late bump can be represented by the model. The derived jet half-opening angle is 0.30 rad and the viewing angle is 0.315 rad. The medium density is 0.05 cm 3 , possibly suggesting that it may be from a merger of compact stars. The similarity between GRBs 060614 and 100418A may indicate that the two GRBs are from the same population and the late bump observed in the two GRBs may be a signal of a two-component jet powered by the GRB central engine.展开更多
The optical emission of GRB 110205A is distinguished by two flares. We examine two possible scenarios for the optical afterglow emission. In the first scenario, the first optical flare is the reverse shock emission of...The optical emission of GRB 110205A is distinguished by two flares. We examine two possible scenarios for the optical afterglow emission. In the first scenario, the first optical flare is the reverse shock emission of the main outflow and the second one is powered by the prolonged activity of the central engine. However, we find that it is rather hard to reasonably interpret the late （t〉0.1 d） afterglow data unless the GRB efficiency is very high （~0.95）. In the second scenario, the first optical flare is the low energy prompt emission and the second one is the reverse shock of the initial outflow. Within this scenario we can interpret the late afterglow emission self-consistently. The reverse shock region may be weakly magnetized and the decline of the second optical flare may be dominated by the high latitude emission, for which strong polarization evolution accompanying the quick decline is possible, as suggested by Fan et al. in 2008. Time-resolved polarimetry by RINGO2-like polarimeters will directly test our prediction.展开更多
The gamma-ray burst GR170817 A associated with GW170817 is subluminous and subenergetic compared with other typical short gamma-ray bursts. It may be due to a relativistic jet viewed off-axis, or a structured jet or c...The gamma-ray burst GR170817 A associated with GW170817 is subluminous and subenergetic compared with other typical short gamma-ray bursts. It may be due to a relativistic jet viewed off-axis, or a structured jet or cocoon emission. Giant flares from magnetars may possibly be ruled out.However, the luminosity and energetics of GRB 170817 A are coincident with those of magnetar giant flares. After the coalescence of a binary neutron star, a hypermassive neutron star may be formed. The hypermassive neutron star may have a magnetar-strength magnetic field. During the collapse of this hypermassive neutron star, magnetic field energy will also be released. This giant-flare-like event may explain the luminosity and energetics of GRB 170817 A. Bursts with similar luminosity and energetics are expected in future neutron star-neutron star or neutron star-black hole mergers.展开更多
The observations with Swift X-ray telescope （XRT） challenge the conventional gamma-ray burst model in many aspects. The XRT light curves are generally composed of four consecutive segments, i.e., a steep decay segme...The observations with Swift X-ray telescope （XRT） challenge the conventional gamma-ray burst model in many aspects. The XRT light curves are generally composed of four consecutive segments, i.e., a steep decay segment, a shallow decay segment, a normal decay segment, a jet-like steep decay segment, and sometimes erratic flares as well. The physical origin of the X-ray emission is highly debatable. We focus here on the physical origin of the X-ray emissions of GRBs 050318 and 060124. We present the XRT light curves and spectra of the two bursts. The light curve decay slopes of the two bursts are normal, and their relations to the spectral indices are consistent with the prediction of the standard forward shock model. The multi-wavelength light curves at 0.5 keV, 1.0 keV, 2.0 keV and 4.0 keV can be reproduced by this model with an isotropic kinetic energy Ek = 2.2 × 10^52 erg, εe = 0.04, εB = 0.01 for GRB 050318 and Ek = 4.2 × 10^53 erg, εe = 0.05, εB = 0.01 for GRB 060124. These facts suggest that the normal decay phases of the X-rays for the two bursts are of the forward shock origin.展开更多
文摘γ暴高能辐射的研究一直是天体物理和宇宙线物理的研究热点,但在100 Ge V及以上能区至今尚未获得确定的观测结果。位于西藏羊八井宇宙线观测站(海拔4 300 m)的ARGO-YBJ实验具有高海拔、大视场等特点,其阈能约几百个Ge V,在探测高能γ暴方面具有独特的优势。利用ARGO-YBJ实验中的"双前峰面"事例,可降低探测器的阈能达几十个Ge V,提高实验探测γ暴的灵敏度。作者研究了ARGO-YBJ实验中的"双前峰面"事例,并通过Monte Carlo模拟,估算出利用该类事例探测高能区(10—100 Ge V)γ暴所需要的最低能流为10-4—10-3erg.cm^(-2)。
基金Supported by National Science and Technology Support Projects(No.2007BAD48B02)Agriculture Science and Technology Achievement Transformation Project(No.2007GB23260410)Basic Research Operating Expenses in Central Public Research Institutes(2007HZS1J007)~~
文摘[Objective] Grb-AST7 concatemer including 17 copies of Grb-AST7 was constructed by ＂self template-primer＂ PCR. [Method] Two primers of which were synthesized based on the amino acid sequence of Gryllus bimaculatus’ Grb-AST7. [Result] Through splicing, a length of 570 bp, containing 17 copies of the Grb-AST7 gene repeats were obtained. Appropriate primer splicing conditions were as follows：splice time 20 min, 25 μl PCR system, containing 2 μl template. [Conclusion] The results laid foundation for the future studies on Grb-AST7 gene expression and bio-activity analysis.
基金Supported by the National Natural Science Foundation of China.
文摘With the successful launch of Swift satellite, more and more data of early X-ray afterglows from short gamma-ray bursts have been collected. Some interesting features such as unusual afterglow light curves and unexpected X-ray flares are revealed. Especially, in some cases, there is a flat segment in the X-ray afterglow light curve. Here we present a simplified model in which we believe that the flattening part is due to energy injection from the central engine. We assume that this energy injection arises from the magnetic dipole radiation of a millisecond pulsar formed after the merger of two neutron stars. We check this model with the short GRB 060313. Our numerical results suggest that energy injection from a millisecond magnetar could make part of the X-ray afterglow light curve flat.
基金supported by the National Natural Science Foundation of China (NSFC, Grant Nos. 11633007 and 11661161010)supported by NSFC (Grant No. 11673078)
文摘The angular distribution of gamma-ray burst（GRB）jets is not yet clear.The observed luminosity of GRB 170817A is the lowest among all known short GRBs,which is best explained by the fact that our line of sight is outside of the jet opening angle,θ_（obs）〉θ_j,whereθ_（obs） is the angle between our line of sight and the jet axis.As inferred by gravitational wave observations,as well as radio and X-ray afterglow modeling of GRB 170817A,it is likely that θ_（obs）~20°–28°.In this work,we quantitatively consider two scenarios of angular energy distribution of GRB ejecta：a top-hat jet and a structured jet with a power law index s.For the top-hat jet model,we get a large θ_j（e.g.,θ_j〉10°）,a rather high local （i.e., z 〈 0.01） short GRB rate ~8–15×10~3 Gpc^（-3）yr~（-1（（estimated to be 90~1850 Gpc^（-3）yr^（-1） in Fong et al.）and an extremely high（on-axis,V（~500 ke V for a typical short GRB）.For the structured jet model,we use θ_（obs） to give limits on s and θ_j for typical on-axis luminosity of a short GRB（e.g.,10^（49）erg s（-1） 1051erg s（-1））,and a low on-axis luminosity case（e.g.,1049erg s（-1））gives more reasonable values of s.The structured jet model is more feasible for GRB170817A than the top-hat jet model due to the rather high local short GRB rate,and the extremely high on-axis E_（peak,0） almost rules out the top-hat jet model.GRB 170817A is likely a low on-axis luminosity GRB（1049erg s（-1））with a structured jet.
基金supported by the National Basic Research Program of China (973 program,2014CB845800)the National Natural Science Foundation of China (NSFC,Grant No.U1331202)+1 种基金the NSFC (Nos.11103036 and U1331101)supported by the NSFC (No.U1231115)
文摘We report the optical observations of GRB 121011 A by the 0.8m TNT facility at Xinglong observatory, China. The light curve of the optical afterglow shows a smooth and featureless bump during the epoch of;30 s and;000 s with a rising index of 1.57 ± 0.28 before the break time of 539 ± 44 s, and a decaying index of about 1.29 ± 0.07 up to the end of our observations. Moreover, the X-ray light curve decays in a single power-law with a slope of about 1.51 ± 0.03 observed by XRT onboard Swift from 100 s to about 10 000 s after the burst trigger. The featureless optical light curve could be understood as an onset process under the external-shock model. The typical frequency has been below or near the optical one before the deceleration time, and the cooling frequency is located between the optical and X-ray wavelengths. The external medium density has a transition from a mixed stage of ISM and wind-type medium before the peak time to the ISM at the later phase. The joint-analysis of X-ray and optical light curves shows that the emissions from both frequencies are consistent with the prediction of the standard afterglow model without any energy injections, indicating that the central engine has stopped its activity and does not restart anymore after the prompt phase.
文摘This paper is the second instalment in our study of the observed time delay in the arrival times of radio photons emanating from Gamma Ray Bursts (GRBs). The mundane assumption in contemporary physics as to the cause of these pondersome time delays is that they are a result of the photon being endowed with a non-zero mass. While we do not rule out the possibility of a non-zero mass for the photon, our working assumption is that the major cause of these time delays may very well be that these photons are travelling in a rarefied cosmic plasma in which the medium’s electrons interact with the electric component of the Photon, thus generating tiny currents that lead to dispersion, hence, a frequency-dependent speed of Light (FDSL). In the present instalment, we “improve” on the model presented in the first instalment by dropping the assumption that the resultant pairs of these radio photons leave the shock front simultaneously. The new assumption of a non-simultaneous— albeit systematic—emission of these photon pairs allows us to obtain a much more convincing and stronger correlation in the time delay. This new correlation allows us to build a unified model for the four GRBs in our sample using a relative distance correction mechanism. The new unified model allows us to obtain as our most significant result a value for the frequency equivalence of the interstellar medium (ISM)’s conductance ν* ~ 1.500 ± 0.009 Hzand also an independent distance measure to the GRBs where we obtain for our four GRB samples an average distance of: ~69.40 ± 0.10, 40.00 ± 0.00, 58.40 ± 0.40, and 86.00 ± 1.00 Mpc, for GRB 030329, 980425, 000418 and 021004 respectively.
基金supported by the National Natural Science Foundation of China (Grants Nos.11025313, 10873002 and 11078008)National Basic Research Program of China (973 Program, Grant No.2009CB824800)+2 种基金Chinese Academy of Sciences (Grant KJCXZ-YW-T19)Guangxi SHI-BAI-QIAN project (Grant No.2007201)Guangxi Science Foundation (2010GXNSFC013011, 2011-135)
文摘Swift GRB 100418A is a long burst at z = 0.624 without detection of any associated supernova （SN）. Its light curves in both the prompt and afterglow phases are similar to GRB 060614, a nearby long GRB without an associated SN. We analyze the observational data of this event and discuss the possible origins of its multiwavelength emission. We show that its joint light curve at 1 keV derived from Swift BAT and XRT observations is composed of two distinguished components. The first component, whose spectrum is extremely soft （Γ = 4.32）, ends with a steep decay segment, indicating the internal origin of this component. The second component is a slowly-rising, broad bump which peaks at ～ 10 5 s post the BAT trigger. Assuming that the late bump is due to onset of the afterglow, we derive the initial Lorentz factor （Γ 0 ） of the GRB fireball and find that it significantly deviates from the relation between the Γ 0 and isotropic gamma-ray energy derived from typical GRBs. We also check whether it follows the same anti-correlation between X-ray luminosity and the break time observed in the shallow decay phase of many typical GRBs, which is usually regarded as a signal of late energy injection from the GRB central engine. However, we find that it does not obey this correlation. We propose that the late bump could be contributed by a two-component jet. We fit the second component with an off-axis jet model for a constant medium density and find the late bump can be represented by the model. The derived jet half-opening angle is 0.30 rad and the viewing angle is 0.315 rad. The medium density is 0.05 cm 3 , possibly suggesting that it may be from a merger of compact stars. The similarity between GRBs 060614 and 100418A may indicate that the two GRBs are from the same population and the late bump observed in the two GRBs may be a signal of a two-component jet powered by the GRB central engine.
基金supported by the National Natural Science Foundation of China(Grant No.11073057)
文摘The optical emission of GRB 110205A is distinguished by two flares. We examine two possible scenarios for the optical afterglow emission. In the first scenario, the first optical flare is the reverse shock emission of the main outflow and the second one is powered by the prolonged activity of the central engine. However, we find that it is rather hard to reasonably interpret the late （t〉0.1 d） afterglow data unless the GRB efficiency is very high （~0.95）. In the second scenario, the first optical flare is the low energy prompt emission and the second one is the reverse shock of the initial outflow. Within this scenario we can interpret the late afterglow emission self-consistently. The reverse shock region may be weakly magnetized and the decline of the second optical flare may be dominated by the high latitude emission, for which strong polarization evolution accompanying the quick decline is possible, as suggested by Fan et al. in 2008. Time-resolved polarimetry by RINGO2-like polarimeters will directly test our prediction.
基金supported by the National Natural Science Foundation of China (NSFC, No. 11773008)supported by the NSFC (Nos. 11373064, 11521303 and 11733010)+2 种基金the Yunnan Natural Science Foundation (2014HB048)supported by the NSFC (Nos. 11173046, 11590784, 11203055 and 11773054)Key Research Program of Frontier Sciences, CAS (No. QYZDJ-SSW-SLH057)
文摘The gamma-ray burst GR170817 A associated with GW170817 is subluminous and subenergetic compared with other typical short gamma-ray bursts. It may be due to a relativistic jet viewed off-axis, or a structured jet or cocoon emission. Giant flares from magnetars may possibly be ruled out.However, the luminosity and energetics of GRB 170817 A are coincident with those of magnetar giant flares. After the coalescence of a binary neutron star, a hypermassive neutron star may be formed. The hypermassive neutron star may have a magnetar-strength magnetic field. During the collapse of this hypermassive neutron star, magnetic field energy will also be released. This giant-flare-like event may explain the luminosity and energetics of GRB 170817 A. Bursts with similar luminosity and energetics are expected in future neutron star-neutron star or neutron star-black hole mergers.
基金the National Natural Science Foundation of China.
文摘The observations with Swift X-ray telescope （XRT） challenge the conventional gamma-ray burst model in many aspects. The XRT light curves are generally composed of four consecutive segments, i.e., a steep decay segment, a shallow decay segment, a normal decay segment, a jet-like steep decay segment, and sometimes erratic flares as well. The physical origin of the X-ray emission is highly debatable. We focus here on the physical origin of the X-ray emissions of GRBs 050318 and 060124. We present the XRT light curves and spectra of the two bursts. The light curve decay slopes of the two bursts are normal, and their relations to the spectral indices are consistent with the prediction of the standard forward shock model. The multi-wavelength light curves at 0.5 keV, 1.0 keV, 2.0 keV and 4.0 keV can be reproduced by this model with an isotropic kinetic energy Ek = 2.2 × 10^52 erg, εe = 0.04, εB = 0.01 for GRB 050318 and Ek = 4.2 × 10^53 erg, εe = 0.05, εB = 0.01 for GRB 060124. These facts suggest that the normal decay phases of the X-rays for the two bursts are of the forward shock origin.
