Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM),consisting of two microsatellites,is designed to detect gamma-ray bursts associated with gravitational-wave events.Here,we introduce th...Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM),consisting of two microsatellites,is designed to detect gamma-ray bursts associated with gravitational-wave events.Here,we introduce the real-time burst alert system of GECAM,with the adoption of the BeiDou-3 short message communication service.We present the post-trigger operations,the detailed ground-based analysis,and the performance of the system.In the first year of the in-flight operation,GECAM was triggered by 42 gamma-ray bursts.The GECAM real-time burst alert system has the ability to distribute the alert within~1 minute after being triggered,which enables timely follow-up observations.展开更多
On 2020 April 27,the soft gamma-ray repeater SGR J1935+2154 entered its intense outburst episode again.Insight-HXMT carried out about one month observation of the source.A total number of 75 bursts were detected durin...On 2020 April 27,the soft gamma-ray repeater SGR J1935+2154 entered its intense outburst episode again.Insight-HXMT carried out about one month observation of the source.A total number of 75 bursts were detected during this activity episode by Insight-HXMT,and persistent emission data were also accumulated.We report on the spin period search result and the phase distribution of burst start times and burst photon arrival times of the Insight-HXMT high energy detectors and Fermi/Gamma-ray Burst Monitor(GBM).We find that the distribution of burst start times is uniform within its spin phase for both Insight-HXMT and Fermi/GBM observations,whereas the phase distribution of burst photons is related to the type of a burst’s energy spectrum.The bursts with the same spectrum have different distribution characteristics in the initial and decay episodes for the activity of magnetar SGR J1935+2154.展开更多
We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations of Insight-HXMT,NICER and MAXI.This outburst can be class...We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations of Insight-HXMT,NICER and MAXI.This outburst can be classified roughly into four different states.Type-C quasi-periodic oscillations(QPOs)observed by NICER(about 0.1-6 Hz)and Insight-HXMT(about 0.7-8 Hz)are also reported in this work.Meanwhile,we study various physical quantities related to QPO frequency.The QPO rms-frequency relationship in the energy band 1-10 keV indicates that there is a turning pointing in frequency around2 Hz,which is similar to that of GRS 1915+105.A possible hypothesis for the relationship above may be related to the inclination of the source,which may require a high inclination to explain it.The relationships between QPO frequency and QPO rms,hardness,total fractional rms and count rate have also been found in other transient sources,which can indicate that the origin of type-C QPOs is non-thermal.展开更多
Fast and reliable localization of high-energy transients is crucial for characterizing the burst properties and guiding the follow-up observations.Localization based on the relative counts of different detectors has b...Fast and reliable localization of high-energy transients is crucial for characterizing the burst properties and guiding the follow-up observations.Localization based on the relative counts of different detectors has been widely used for all-sky gamma-ray monitors.There are two major methods for this count distribution localization:χ^(2)minimization method and the Bayesian method.Here we propose a modified Bayesian method that could take advantage of both the accuracy of the Bayesian method and the simplicity of the χ^(2)method.With comprehensive simulations,we find that our Bayesian method with Poisson likelihood is generally more applicable for various bursts than the χ^(2)method,especially for weak bursts.We further proposed a location-spectrum iteration approach based on the Bayesian inference,which could alleviate the problems caused by the spectral difference between the burst and location templates.Our method is very suitable for scenarios with limited computation resources or timesensitive applications,such as in-flight localization software,and low-latency localization for rapidly follow-up observations.展开更多
Realtime trigger and localization of bursts are the key functions of GECAM,an all-sky gamma-ray monitor launched on 2020 December 10.We developed a multifunctional trigger and localization software operating in the CP...Realtime trigger and localization of bursts are the key functions of GECAM,an all-sky gamma-ray monitor launched on 2020 December 10.We developed a multifunctional trigger and localization software operating in the CPU of the GECAM Electronic Box.This onboard software has the following features:high trigger efficiency for real celestial bursts with a suppression of false triggers caused by charged particle bursts and background fluctuation,dedicated localization algorithm optimized for both short and long bursts,and low time latency of the trigger information which is downlinked through the Global Short Message Communication service of the global BeiDou navigation system.This paper provides a detailed description of the design and development of the trigger and localization software system for GECAM.It covers the general design,workflow,the main functions,and the algorithms used in the system.The paper also includes on-ground trigger tests using simulated gamma-ray bursts generated by a dedicated X-ray tube,as well as an overview of the performance for real celestial bursts during its in-orbit operation.展开更多
The Gravitational wave burst high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)is a dedicated mission for monitoring high-energy transients.Here we report the design of the GECAM Scientific Ground Segment(...The Gravitational wave burst high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)is a dedicated mission for monitoring high-energy transients.Here we report the design of the GECAM Scientific Ground Segment(GSGS)in terms of the scientific requirements,including the architecture,the external interfaces,the main function,and workflow.Judging from the analysis and verification results during the commissioning phase,the GSGS functions well and is able to monitor the status of the payloads,adjust the parameters,develop the scientific observation plans,generate the scientific data products,analyze the data,etc.Thus,the on-orbit operation and scientific researches of GECAM are guaranteed.展开更多
In October 2022,the magnetar SGR J1935+2154 entered the active outburst state.During the episode,the InsightHXMT satellite carried out a long observation that lasted for 20 days.More than 300 bursts were detected,and ...In October 2022,the magnetar SGR J1935+2154 entered the active outburst state.During the episode,the InsightHXMT satellite carried out a long observation that lasted for 20 days.More than 300 bursts were detected,and a certain amount of persistent radiation signals were also accumulated.This paper mainly introduces the results of persistent radiation profile folding and period search based on Insight-HXMT data.At the same time,the burst phase distribution characteristics,spectral lag results of burst,the spectral characteristics of zero-lag bursts and the time-resolved spectral evolution characteristics of high-flux bursts are reported.We found that there is no significant delay feature during different energy bands for the bursts of SGR J1935+2154.The observed zero-lag burst does not have a unique spectrum.The time-resolved spectrum of the individual burst has consistent spectral types and spectral parameters at different time periods of the burst.We also find that the burst number phase distribution and the burst photon phase distribution have the same tendency to concentrate in specific regions of the persistent emission profile.展开更多
The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)mission is designed to monitor the Gamma-Ray Bursts(GRBs)associated with gravitational waves and other high-energy transient sources...The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)mission is designed to monitor the Gamma-Ray Bursts(GRBs)associated with gravitational waves and other high-energy transient sources.The mission consists of two microsatellites which are planned to operate at the opposite sides of the Earth.Each GECAM satellite could detect and localize GRBs in about 8 keV-5 MeV with its 25 Gamma-Ray Detectors(GRDs).In this work,we report the in-flight energy calibration of GRDs using the characteristic gamma-ray lines in the background spectra,and show their performance evolution during the commissioning phase.Besides,a preliminary cross-calibration of energy response with Fermi GBM data is also presented,validating the energy response of GRDs.展开更多
Fast radio bursts(FRBs) are highly dispersed millisecond-duration radio bursts,[1,2]of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, ...Fast radio bursts(FRBs) are highly dispersed millisecond-duration radio bursts,[1,2]of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, we present the collection of 1863 burst dynamic spectra of FRB 20201124A measured with the Five-hundred-meter Aperture Spherical radio Telescope(FAST). The current collection, taken from the observation during the FRB active phase from April to June 2021, is the largest burst sample detected for any FRB so far. The standard PSRFITs format is adopted, including dynamic spectra of the burst, and the time information of the dynamic spectra, in addition, mask files help readers to identify the pulse positions are also provided. The dataset is available in Science Data Bank, with the link https://www.doi.org/10.57760/sciencedb.j00113.00076.展开更多
As one of three primary scientific payloads of Insight-Hard X-ray Modulation Telescope(Insight-HXMT),the High Energy Xray telescope(HE)consists of 18 Nal/CsI phoswich detectors,and the CsI detectors can detect gamma-r...As one of three primary scientific payloads of Insight-Hard X-ray Modulation Telescope(Insight-HXMT),the High Energy Xray telescope(HE)consists of 18 Nal/CsI phoswich detectors,and the CsI detectors can detect gamma-rays that penetrate the satellite from all directions,with an energy range of about 60 keV to 3.2 MeV and a total geometric area of about 5100 cm^(2).These characteristics make the CsI detectors suitable for monitoring GRBs and other high-energy transients.Initial calibration and performance studies of the CsI detectors'instrumental response were conducted during the early operation phase before2020.In this work,we refine the cross-calibration of CsI detectors using a large sample of 85 bright GRBs.Our analysis reveals that the effective area is inversely proportional to the incident angle(θ),with no correlation observed with the azimuthal angle(θ).We subsequently incorporated this relationship into the calibration database to correct for systematic biases in the initial calibration.Furthermore,we demonstrate that joint spectral analyses incorporating CsI data provide better constraints on highenergy spectral parameters for most GRBs.Additionally,we evaluate,for the first time,the energy response of CsI detectors for pointing observation by measuring the Crab Nebula using the Earth occultation technique.This effort extends the energy range of the Insight-HXMT telescope from 1-250 to 1-750 keV for pointing observations.Those results show that the spectra measured by CsI detectors are consistent with other well-calibrated instruments,validating the reliability and accuracy of the CsI detectors'performance.Our work will contribute to Insight-HXMT's capacity to generate more scientific outputs in the field of time-domain astronomy.展开更多
Charged particle precipitation typically manifests as a gradual increase and decrease of flux observed by space detectors.Cases with rapid flux variation are very rare,while periodic events are even more extraordinary...Charged particle precipitation typically manifests as a gradual increase and decrease of flux observed by space detectors.Cases with rapid flux variation are very rare,while periodic events are even more extraordinary.These oscillating particle precipitation(OPP)events are usually attributed to the bounce motion of electrons probably induced by lightning.However,the origin of these oscillation events is still on debate.Here we report three peculiar charged particle precipitation events detected by GECAM during a geomagnetic storm on March 21,2024,with two exhibiting significant periodicity.These events were observed around the same region during three consecutive orbits with a life time of more than 3.5 h.Through comprehensive temporal and spectral analyses,we find that one of the OPP events exhibited a transition in spectral lag of mini-pulses,shifting from“softer-earlier”to“softer-later”while showing no significant time evolution in overall frequency characteristics,and that there is no association found between these two OPP events and lightning activity nearby.Finally,we discussed possible scenarios to explain these GECAM-detected OPP events,and we found that they may represent a new type of particle precipitation event or a peculiar lightning-induced electron precipitation(LEP).展开更多
As the brightest gamma-ray burst ever observed,GRB 221009A provided a precious opportunity to explore spectral line features.In this article,we performed a comprehensive spectroscopy analysis of GRB 221009A jointly wi...As the brightest gamma-ray burst ever observed,GRB 221009A provided a precious opportunity to explore spectral line features.In this article,we performed a comprehensive spectroscopy analysis of GRB 221009A jointly with GECAM-C and Fermi/GBM data to search for emission and absorption lines.For the first time we investigated the line feature throughout this GRB including the most bright part where many instruments suffered problems,and identified prominent emission lines in multiple time intervals.The central energy of the Gaussian emission line evolves from about 37 to 6 MeV,with a nearly constant ratio(about 10%)between the line width and central energy.Particularly,we find that both the central energy and the energy flux of the emission line evolve with time as a power law decay with power law index of–1 and–2,respectively.We suggest that the observed emission lines most likely origin from the blue-shifted electron positron pair annihilation 511 ke V line.We find that a standard high latitude emission scenario cannot fully interpret the observation,thus we propose that the emission line comes from some dense clumps with electron positron pairs traveling together with the jet.In this scenario,we can use the emission line to directly,for the first time,measure the bulk Lorentz factor of the jet(Γ)and reveal its time evolution(i.e.,Γ~t^(-1))during the prompt emission.Interestingly,we find that the flux of the annihilation line in the co-moving frame keeps constant.These discoveries of the spectral line features shed new and important lights on the physics of GRB and relativistic jet.展开更多
In the era of time-domain,multi-messenger astronomy,the detection of transient events on the high-energy electromagnetic sky has become more important than ever.The gravitational wave high-energy electromagnetic count...In the era of time-domain,multi-messenger astronomy,the detection of transient events on the high-energy electromagnetic sky has become more important than ever.The gravitational wave high-energy electromagnetic counterpart all-sky monitor(GECAM)is a dedicated mission to monitor gamma-ray transients,launched in December,2020.A real-time on-board trigger and location software,using the traditional signal-to-noise ratio(SNR)method for blind search,is constrained to relatively bright signals due to the limitations in on-board computing resources and the need for real-time search.In this work,we developed a ground-based pipeline for GECAM to search for various transients,especially for weak bursts missed by on-board software.This pipeline includes both automatic and manual mode,offering options for blind search and targeted search.The targeted search is specifically designed to search for interesting weak bursts,such as gravitational wave-associated gamma-ray bursts(GRBs).From the ground search of the data in the first year,GECAM has been triggered by 54 GRBs and other transients,including soft gamma-ray repeaters,X-ray binaries,solar flares,terrestrial gamma-ray flashes.We report the properties of each type of triggers,such as trigger time and light curves.With this search pipeline and assuming a soft Band spectrum,the GRB detection sensitivity of GECAM is increased to about 1.1×10^(-8)erg cm^(-2)s^(-1)(10-1000 ke V,burst duration of 20 s).These results demonstrate that the GECAM ground search system(both blind search and targeted search)is a versatile pipeline to recover true astrophysical signals which were too weak to be found in the on-board search.展开更多
As China's first X-ray astronomy satellite,the hard X-ray modulation telescope(Insight-HXMT)carries three sets of X-ray telescopes.The high energy X-ray telescope(Insight-HXMT/HE)could serve as an all-sky gamma-ra...As China's first X-ray astronomy satellite,the hard X-ray modulation telescope(Insight-HXMT)carries three sets of X-ray telescopes.The high energy X-ray telescope(Insight-HXMT/HE)could serve as an all-sky gamma-ray monitor with a detection area of up to 5000 cm2and energy range from about 200 ke V to 3 Me V.These characteristics,together with the high orbital inclination angle(43°)of the satellite,make the HE very suitable for detecting terrestrial gamma-ray flashes(TGFs).In this work,we implemented a dedicated TGF search algorithm for Insight-HXMT/HE,and identified 282 bright TGFs in its first four years of operation.We made a systematic study on the properties of these TGFs,including trigger time,duration,intensity,as well as the lightning association.We found that TGFs detected in mid-latitude regions(30°to 43°)are rare and they do not exhibit significantly different properties compared with TGFs in low-latitude(within 30°).Interestingly,the hardness ratio of TGF measured by Insight-HXMT/HE seems to be independent of the TGF duration,which differs from previous studies.These results show that,despite the dedicated design for astronomical observation,Insight-HXMT/HE is a versatile instrument to study energetic radiation phenomena from the Earth.展开更多
We investigate high time resolution data obtained by the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)during the flare event on 2022 April 21 at 01:52 UT.Several subpeaks with durat...We investigate high time resolution data obtained by the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)during the flare event on 2022 April 21 at 01:52 UT.Several subpeaks with durations of 4-6 s have been detected in the hard X-ray precursor phase,and the key feature is that they appear in pairs and seem like double-peak struc-tures.These subpeaks are rarely observed in hard X-ray band and confirmed by the microwave obtained by Nobeyama Radio Polarimeters(NoRP)and Radio Solar Telescope Network(RSTN).While an exponential function can describe the continuum component of the time profile from the precursor to part of the impulsive phase.The periods of quasi-periodic pulsations(QPPs)are detected to be about 7.3 and 12.8 s for the precursor and impulsive phase,respectively,with at least 95%confidence level.The paired QPPs are assumed to be double-peak QPPs and then the scenario of current loop coalescence model is found to be in good agreement with our observation.The precursor phase can be interpreted as the oscillating coalescence of two islands,while the impulsive phase can be interpreted as more islands to coalesce one by one to form larger islands.展开更多
基金supported by the National Key R&D Program of China(2021YFA0718500,2022YFF0711404)the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(grant Nos.XDA15360300,XDA15052700 and E02212A02S)+1 种基金the National Natural Science Foundation of China(grant Nos.U2031205,12133007)supported by the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences,grant No.XDA15360000。
文摘Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM),consisting of two microsatellites,is designed to detect gamma-ray bursts associated with gravitational-wave events.Here,we introduce the real-time burst alert system of GECAM,with the adoption of the BeiDou-3 short message communication service.We present the post-trigger operations,the detailed ground-based analysis,and the performance of the system.In the first year of the in-flight operation,GECAM was triggered by 42 gamma-ray bursts.The GECAM real-time burst alert system has the ability to distribute the alert within~1 minute after being triggered,which enables timely follow-up observations.
基金partially supported by International Partnership Program of Chinese Academy of Sciences(Grant No.113111KYSB20190020)the National Key R&D Program of China(2021YFA0718500)from the Minister of Science and Technology of China(MOST)The authors thank supports from the National Natural Science Foundation of China under Grants U1938109,U1838201,U1838202,12173103,U2038101,U1938103,12133007,U1938201 and 11733009。
文摘On 2020 April 27,the soft gamma-ray repeater SGR J1935+2154 entered its intense outburst episode again.Insight-HXMT carried out about one month observation of the source.A total number of 75 bursts were detected during this activity episode by Insight-HXMT,and persistent emission data were also accumulated.We report on the spin period search result and the phase distribution of burst start times and burst photon arrival times of the Insight-HXMT high energy detectors and Fermi/Gamma-ray Burst Monitor(GBM).We find that the distribution of burst start times is uniform within its spin phase for both Insight-HXMT and Fermi/GBM observations,whereas the phase distribution of burst photons is related to the type of a burst’s energy spectrum.The bursts with the same spectrum have different distribution characteristics in the initial and decay episodes for the activity of magnetar SGR J1935+2154.
基金the HXMT mission,a project funded by China National Space Administration(CNSA)and the Chinese Academy of Sciences(CAS)supported by the National Key R&D Program of China(2016YFA0400800)the National Natural Science Foundation of China(Grant Nos.11673023,U1838201,U1838115,U1838111,U1838202,11733009 and U1838108)。
文摘We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846-031 during its outburst in 2019 with the observations of Insight-HXMT,NICER and MAXI.This outburst can be classified roughly into four different states.Type-C quasi-periodic oscillations(QPOs)observed by NICER(about 0.1-6 Hz)and Insight-HXMT(about 0.7-8 Hz)are also reported in this work.Meanwhile,we study various physical quantities related to QPO frequency.The QPO rms-frequency relationship in the energy band 1-10 keV indicates that there is a turning pointing in frequency around2 Hz,which is similar to that of GRS 1915+105.A possible hypothesis for the relationship above may be related to the inclination of the source,which may require a high inclination to explain it.The relationships between QPO frequency and QPO rms,hardness,total fractional rms and count rate have also been found in other transient sources,which can indicate that the origin of type-C QPOs is non-thermal.
基金supported by the National Key R&D Program of China(2021YFA0718500)support from the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(grant Nos.XDA15360102,XDA15360300,XDA15052700 and E02212A02S)+1 种基金the National Natural Science Foundation of China(grant Nos.12173038 and U2038106)the National HEP Data Center(grant No.E029S2S1)。
文摘Fast and reliable localization of high-energy transients is crucial for characterizing the burst properties and guiding the follow-up observations.Localization based on the relative counts of different detectors has been widely used for all-sky gamma-ray monitors.There are two major methods for this count distribution localization:χ^(2)minimization method and the Bayesian method.Here we propose a modified Bayesian method that could take advantage of both the accuracy of the Bayesian method and the simplicity of the χ^(2)method.With comprehensive simulations,we find that our Bayesian method with Poisson likelihood is generally more applicable for various bursts than the χ^(2)method,especially for weak bursts.We further proposed a location-spectrum iteration approach based on the Bayesian inference,which could alleviate the problems caused by the spectral difference between the burst and location templates.Our method is very suitable for scenarios with limited computation resources or timesensitive applications,such as in-flight localization software,and low-latency localization for rapidly follow-up observations.
基金supported by the Strategic Priority Research Program on Space Science of the Chinese Academy of Sciences,the support from the Strategic Priority Research Program on Space Science(grant Nos.XDA15360300,XDA15360000,XDA15360102,XDA15052700 and E02212A02S)of the Chinese Academy of Sciencesthe National Natural Science Foundation of China(NSFC,Grant No.12173038)and BeiDou navigation system。
文摘Realtime trigger and localization of bursts are the key functions of GECAM,an all-sky gamma-ray monitor launched on 2020 December 10.We developed a multifunctional trigger and localization software operating in the CPU of the GECAM Electronic Box.This onboard software has the following features:high trigger efficiency for real celestial bursts with a suppression of false triggers caused by charged particle bursts and background fluctuation,dedicated localization algorithm optimized for both short and long bursts,and low time latency of the trigger information which is downlinked through the Global Short Message Communication service of the global BeiDou navigation system.This paper provides a detailed description of the design and development of the trigger and localization software system for GECAM.It covers the general design,workflow,the main functions,and the algorithms used in the system.The paper also includes on-ground trigger tests using simulated gamma-ray bursts generated by a dedicated X-ray tube,as well as an overview of the performance for real celestial bursts during its in-orbit operation.
基金supported by the National Key R&D Program of China(2022YFF0711404,2021YFA0718500)International Partnership Program of Chinese Academy of Sciences(grant No.113111KYSB20190020)+2 种基金the National Natural Science Foundation of China(NSFC,Grant No.U1938106)the open subject of the National HEP Data Center(E029S2S1)support from the Strategic Priority Research Program on Space Science,the Chinese Academy of Sciences(grant Nos.XDA15360102,XDA15360300,XDA15052700 and E02212A02S)。
文摘The Gravitational wave burst high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)is a dedicated mission for monitoring high-energy transients.Here we report the design of the GECAM Scientific Ground Segment(GSGS)in terms of the scientific requirements,including the architecture,the external interfaces,the main function,and workflow.Judging from the analysis and verification results during the commissioning phase,the GSGS functions well and is able to monitor the status of the payloads,adjust the parameters,develop the scientific observation plans,generate the scientific data products,analyze the data,etc.Thus,the on-orbit operation and scientific researches of GECAM are guaranteed.
基金supported by International Partnership Program of Chinese Academy of Sciences(grant No.113111KYSB20190020)by the National Key R&D Program of China(2021YFA0718500)from the Minister of Science and Technology of China(MOST)supports from the National Natural Science Foundation of China under Grants U1938109,12333007,12173103,U2038101,U1938103,12333007,12303045,U1938201 and 11733009。
文摘In October 2022,the magnetar SGR J1935+2154 entered the active outburst state.During the episode,the InsightHXMT satellite carried out a long observation that lasted for 20 days.More than 300 bursts were detected,and a certain amount of persistent radiation signals were also accumulated.This paper mainly introduces the results of persistent radiation profile folding and period search based on Insight-HXMT data.At the same time,the burst phase distribution characteristics,spectral lag results of burst,the spectral characteristics of zero-lag bursts and the time-resolved spectral evolution characteristics of high-flux bursts are reported.We found that there is no significant delay feature during different energy bands for the bursts of SGR J1935+2154.The observed zero-lag burst does not have a unique spectrum.The time-resolved spectrum of the individual burst has consistent spectral types and spectral parameters at different time periods of the burst.We also find that the burst number phase distribution and the burst photon phase distribution have the same tendency to concentrate in specific regions of the persistent emission profile.
基金supported by the Strategic Priority Program on Space Science,the Chinese Academy of Sciences,grant Nos.XDA15360102,XDA15360300 and E02212A02Sthe National Natural Science Foundation of China(Project:12061131007)。
文摘The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)mission is designed to monitor the Gamma-Ray Bursts(GRBs)associated with gravitational waves and other high-energy transient sources.The mission consists of two microsatellites which are planned to operate at the opposite sides of the Earth.Each GECAM satellite could detect and localize GRBs in about 8 keV-5 MeV with its 25 Gamma-Ray Detectors(GRDs).In this work,we report the in-flight energy calibration of GRDs using the characteristic gamma-ray lines in the background spectra,and show their performance evolution during the commissioning phase.Besides,a preliminary cross-calibration of energy response with Fermi GBM data is also presented,validating the energy response of GRDs.
基金supported by the National SKA Program of China (Grant Nos. 2020SKA0120100 and 2020SKA0120200)the National Natural Science Foundation of China (Grant Nos. 12041304, 11873067, 11988101, 12041303, 11725313, 11725314, 11833003, 12003028, 12041306, 12103089, U2031209, U2038105, and U1831207)+8 种基金the National Key Research and Development Program of China (Grant Nos. 2019YFA0405100, 2017YFA0402602, 2018YFA0404204, and 2016YFA0400801)Key Research Program of the Chinese Academy of Sciences (Grant No. QYZDJ-SSW-SLH021)Natural Science Foundation of Jiangsu Province (Grant No. BK20211000)Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS, the Strategic Priority Research Program on Space Science, the Western Light Youth Project of Chinese Academy of Sciences (Grant Nos. XDA15360000, XDA15052700, and XDB23040400)funding from the MaxPlanck Partner Group, the science research grants from the China Manned Space Project (Grant Nos. CMS-CSST2021-B11 and CMS-CSST-2021-A11)PKU development (Grant No. 7101502590)support from the XPLORER PRIZEsupported by Fundamental Research Funds for the Central Universities (Grant No. 14380046)the Program for Innovative Talents, Entrepreneur in Jiangsu。
文摘Fast radio bursts(FRBs) are highly dispersed millisecond-duration radio bursts,[1,2]of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, we present the collection of 1863 burst dynamic spectra of FRB 20201124A measured with the Five-hundred-meter Aperture Spherical radio Telescope(FAST). The current collection, taken from the observation during the FRB active phase from April to June 2021, is the largest burst sample detected for any FRB so far. The standard PSRFITs format is adopted, including dynamic spectra of the burst, and the time information of the dynamic spectra, in addition, mask files help readers to identify the pulse positions are also provided. The dataset is available in Science Data Bank, with the link https://www.doi.org/10.57760/sciencedb.j00113.00076.
基金the support from the National Key Research and Development Program of China(Grant No.2021YFA0718500)the Strategic Priority Research Program+1 种基金the Chinese Academy of Sciences(Grant Nos.XDB0550300 and XDA30050000)the National Natural Science Foundation of China(Grant Nos.12273042,12494572,12373047,12273043,and 12103055)。
文摘As one of three primary scientific payloads of Insight-Hard X-ray Modulation Telescope(Insight-HXMT),the High Energy Xray telescope(HE)consists of 18 Nal/CsI phoswich detectors,and the CsI detectors can detect gamma-rays that penetrate the satellite from all directions,with an energy range of about 60 keV to 3.2 MeV and a total geometric area of about 5100 cm^(2).These characteristics make the CsI detectors suitable for monitoring GRBs and other high-energy transients.Initial calibration and performance studies of the CsI detectors'instrumental response were conducted during the early operation phase before2020.In this work,we refine the cross-calibration of CsI detectors using a large sample of 85 bright GRBs.Our analysis reveals that the effective area is inversely proportional to the incident angle(θ),with no correlation observed with the azimuthal angle(θ).We subsequently incorporated this relationship into the calibration database to correct for systematic biases in the initial calibration.Furthermore,we demonstrate that joint spectral analyses incorporating CsI data provide better constraints on highenergy spectral parameters for most GRBs.Additionally,we evaluate,for the first time,the energy response of CsI detectors for pointing observation by measuring the Crab Nebula using the Earth occultation technique.This effort extends the energy range of the Insight-HXMT telescope from 1-250 to 1-750 keV for pointing observations.Those results show that the spectra measured by CsI detectors are consistent with other well-calibrated instruments,validating the reliability and accuracy of the CsI detectors'performance.Our work will contribute to Insight-HXMT's capacity to generate more scientific outputs in the field of time-domain astronomy.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12273042, and 12303045)the National Key R&D Program of China (Grant No. 2021YFA0718500)+2 种基金the Natural Science Foundation of Hebei Province (Grant No. A2023205020)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant Nos. XDB0550300, and XDA30050000)supported by the Strategic Priority Research Program on Space Science of the Chinese Academy of Sciences (Grant No. XDA15360000)
文摘Charged particle precipitation typically manifests as a gradual increase and decrease of flux observed by space detectors.Cases with rapid flux variation are very rare,while periodic events are even more extraordinary.These oscillating particle precipitation(OPP)events are usually attributed to the bounce motion of electrons probably induced by lightning.However,the origin of these oscillation events is still on debate.Here we report three peculiar charged particle precipitation events detected by GECAM during a geomagnetic storm on March 21,2024,with two exhibiting significant periodicity.These events were observed around the same region during three consecutive orbits with a life time of more than 3.5 h.Through comprehensive temporal and spectral analyses,we find that one of the OPP events exhibited a transition in spectral lag of mini-pulses,shifting from“softer-earlier”to“softer-later”while showing no significant time evolution in overall frequency characteristics,and that there is no association found between these two OPP events and lightning activity nearby.Finally,we discussed possible scenarios to explain these GECAM-detected OPP events,and we found that they may represent a new type of particle precipitation event or a peculiar lightning-induced electron precipitation(LEP).
基金supported by the National Key R&D Program of China(Grant Nos.2021YFA0718500,and 2023YFE0101200)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA15360102,XDA15360300,and XDA15052700)+3 种基金the National Natural Science Foundation of China(Grant Nos.12273042,61234003,61434004,61504141,11673062,12393813,2333007,12027803,and 12303045)the CAS Interdisciplinary Project(Grant No.KJZD-EW-L11-04)supported by the Strategic Priority Research Program on Space Science(Grant No.XDA15360000)of the Chinese Academy of Sciencessupported by the Yunnan Revitalization Talent Support Program(Yun Ling Scholar Award)。
文摘As the brightest gamma-ray burst ever observed,GRB 221009A provided a precious opportunity to explore spectral line features.In this article,we performed a comprehensive spectroscopy analysis of GRB 221009A jointly with GECAM-C and Fermi/GBM data to search for emission and absorption lines.For the first time we investigated the line feature throughout this GRB including the most bright part where many instruments suffered problems,and identified prominent emission lines in multiple time intervals.The central energy of the Gaussian emission line evolves from about 37 to 6 MeV,with a nearly constant ratio(about 10%)between the line width and central energy.Particularly,we find that both the central energy and the energy flux of the emission line evolve with time as a power law decay with power law index of–1 and–2,respectively.We suggest that the observed emission lines most likely origin from the blue-shifted electron positron pair annihilation 511 ke V line.We find that a standard high latitude emission scenario cannot fully interpret the observation,thus we propose that the emission line comes from some dense clumps with electron positron pairs traveling together with the jet.In this scenario,we can use the emission line to directly,for the first time,measure the bulk Lorentz factor of the jet(Γ)and reveal its time evolution(i.e.,Γ~t^(-1))during the prompt emission.Interestingly,we find that the flux of the annihilation line in the co-moving frame keeps constant.These discoveries of the spectral line features shed new and important lights on the physics of GRB and relativistic jet.
基金supported by the National Natural Science Foundation of China(Grant Nos.12303045,12273042,and 12373047)the National Key R&D Program of China(Grant No.2022YFF0711404)+3 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA15360102,XDA15360300,and XDA15052700)The GECAM(Huairou-1)mission was supported by the Strategic Priority Research Program on Space Science(Grant No.XDA15360000)of the Chinese Academy of Sciencesthe support from the Natural Science Foundation of Hebei Province(Grant No.A2023205020)the Science Foundation of Hebei Normal University(Grant No.L2023B11)。
文摘In the era of time-domain,multi-messenger astronomy,the detection of transient events on the high-energy electromagnetic sky has become more important than ever.The gravitational wave high-energy electromagnetic counterpart all-sky monitor(GECAM)is a dedicated mission to monitor gamma-ray transients,launched in December,2020.A real-time on-board trigger and location software,using the traditional signal-to-noise ratio(SNR)method for blind search,is constrained to relatively bright signals due to the limitations in on-board computing resources and the need for real-time search.In this work,we developed a ground-based pipeline for GECAM to search for various transients,especially for weak bursts missed by on-board software.This pipeline includes both automatic and manual mode,offering options for blind search and targeted search.The targeted search is specifically designed to search for interesting weak bursts,such as gravitational wave-associated gamma-ray bursts(GRBs).From the ground search of the data in the first year,GECAM has been triggered by 54 GRBs and other transients,including soft gamma-ray repeaters,X-ray binaries,solar flares,terrestrial gamma-ray flashes.We report the properties of each type of triggers,such as trigger time and light curves.With this search pipeline and assuming a soft Band spectrum,the GRB detection sensitivity of GECAM is increased to about 1.1×10^(-8)erg cm^(-2)s^(-1)(10-1000 ke V,burst duration of 20 s).These results demonstrate that the GECAM ground search system(both blind search and targeted search)is a versatile pipeline to recover true astrophysical signals which were too weak to be found in the on-board search.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFA0718500)the National Natural Science Foundation of China(Grant No.12273042)the Science Research Program of Dezhou University(2024xjrc142)。
文摘As China's first X-ray astronomy satellite,the hard X-ray modulation telescope(Insight-HXMT)carries three sets of X-ray telescopes.The high energy X-ray telescope(Insight-HXMT/HE)could serve as an all-sky gamma-ray monitor with a detection area of up to 5000 cm2and energy range from about 200 ke V to 3 Me V.These characteristics,together with the high orbital inclination angle(43°)of the satellite,make the HE very suitable for detecting terrestrial gamma-ray flashes(TGFs).In this work,we implemented a dedicated TGF search algorithm for Insight-HXMT/HE,and identified 282 bright TGFs in its first four years of operation.We made a systematic study on the properties of these TGFs,including trigger time,duration,intensity,as well as the lightning association.We found that TGFs detected in mid-latitude regions(30°to 43°)are rare and they do not exhibit significantly different properties compared with TGFs in low-latitude(within 30°).Interestingly,the hardness ratio of TGF measured by Insight-HXMT/HE seems to be independent of the TGF duration,which differs from previous studies.These results show that,despite the dedicated design for astronomical observation,Insight-HXMT/HE is a versatile instrument to study energetic radiation phenomena from the Earth.
基金supported by the National Natural Science Foundation of China (Grant Nos. U1938102, and 11973092)the National Program on Key Research and Development Project (Grant No. 2016YFA0400802)supported by the Surface Project of Jiangsu Province (Grant No. BK20211402)
文摘We investigate high time resolution data obtained by the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)during the flare event on 2022 April 21 at 01:52 UT.Several subpeaks with durations of 4-6 s have been detected in the hard X-ray precursor phase,and the key feature is that they appear in pairs and seem like double-peak struc-tures.These subpeaks are rarely observed in hard X-ray band and confirmed by the microwave obtained by Nobeyama Radio Polarimeters(NoRP)and Radio Solar Telescope Network(RSTN).While an exponential function can describe the continuum component of the time profile from the precursor to part of the impulsive phase.The periods of quasi-periodic pulsations(QPPs)are detected to be about 7.3 and 12.8 s for the precursor and impulsive phase,respectively,with at least 95%confidence level.The paired QPPs are assumed to be double-peak QPPs and then the scenario of current loop coalescence model is found to be in good agreement with our observation.The precursor phase can be interpreted as the oscillating coalescence of two islands,while the impulsive phase can be interpreted as more islands to coalesce one by one to form larger islands.
