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  • Oxford University Press (OUP)  (5)
  • Li, Xin-Qiao  (5)
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  • Oxford University Press (OUP)  (5)
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  • 1
    Online Resource
    Online Resource
    Discovery of the linear energy dependence of the spectral lag of X-ray bursts from SGR J1935+2154
    Oxford University Press (OUP) ; 2023
    In:  Monthly Notices of the Royal Astronomical Society Vol. 521, No. 4 ( 2023-03-31), p. 5308-5333
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 521, No. 4 ( 2023-03-31), p. 5308-5333
    Abstract: Spectral lag of the low-energy photons with respect to the high-energy ones is a common astrophysical phenomenon (such as gamma-ray bursts and the Crab Pulsar) and may serve as a key probe to the underlying radiation mechanism. However, spectral lag in keV range of the magnetar bursts has not been systematically studied yet. In this work, we perform a detailed spectral lag analysis with the Li et al.’s Cross-Correlation Function (Li-CCF) method for SGR J1935+2154 bursts observed by Insight-Hard X-ray Modulation Telescope (HXMT), Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor (GECAM), and Fermi/Gamma-ray Burst Monitor (GBM) from 2014 July to 2022 January. We discover that the spectral lags of about 61 per cent (non-zero significance & gt;1σ) bursts from SGR J1935+2154 are linearly dependent on the photon energy (E) with tlag(E) = α(E/keV) + C, which may be explained by a linear change of the temperature of the blackbody-emitting plasma with time. The distribution of the slope (α) approximately follows a Gaussian function with mean and standard deviation of 0.02 ms keV−1 (i.e. high-energy photons arrive earlier) and 0.02 ms keV−1, respectively. We also find that the distribution can be well fitted with three Gaussians with mean values of ∼−10.009, 0.013, and 0.039 ms keV−1, which may correspond to different origins of the bursts. These spectral lag features may have important implications on the magnetar bursts.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stad885
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 2
    Online Resource
    Online Resource
    Revisit the periodicity of SGR J1935+2154 bursts with updated sample
    Oxford University Press (OUP) ; 2022
    In:  Monthly Notices of the Royal Astronomical Society Vol. 517, No. 3 ( 2022-10-28), p. 3854-3863
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 517, No. 3 ( 2022-10-28), p. 3854-3863
    Abstract: 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 ∼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.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stac2918
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 3
    Online Resource
    Online Resource
    Ground-based calibration and characterization of LaBr3-SiPM-based gamma-ray detector on GECAM satellite: 8–160 keV
    Oxford University Press (OUP) ; 2023
    In:  Monthly Notices of the Royal Astronomical Society Vol. 525, No. 3 ( 2023-09-01), p. 3399-3412
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 525, No. 3 ( 2023-09-01), p. 3399-3412
    Abstract: As the main detector of the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor mission (GECAM), the calibration of the energy response and detection efficiency of the gamma-ray detector (GRD) is the main content of the ground-based calibration. This article mainly focuses on the calibration of the energy response and detection efficiency in the 8–160 keV with a refined measurement around the absorption edges of the lanthanum bromide crystal ($\rm {LaBr_3}$). The GRD performances for different crystal types, data acquisition modes, working modes, and incident positions are also analysed in detail. We show that the calibration campaign is comprehensive, the detector performance meets the flight requirements, and the calibration results generally agree with simulations as expected. The detector’s model was corrected by the ground-based calibration, which led to the establishment of the calibration data base.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stad2439
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
    Location Call Number Limitation Availability
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  • 4
    Online Resource
    Online Resource
    Burst search method based on likelihood ratio in Poisson statistics
    Oxford University Press (OUP) ; 2022
    In:  Monthly Notices of the Royal Astronomical Society Vol. 518, No. 2 ( 2022-11-24), p. 2005-2014
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 518, No. 2 ( 2022-11-24), p. 2005-2014
    Abstract: Searching for X-ray and gamma-ray bursts, including Gamma-ray bursts (GRBs), Soft Gamma-ray Repeaters (SGRs), and high energy transients associated with Gravitational wave (GW) events or Fast radio bursts (FRBs), is of great importance in the multimessenger and multiwavelength era. Although a coherent search based on the likelihood ratio and Gaussian statistics has been established and utilized in many studies, this Gaussian-based method could be problematic for weak and short bursts which usually have very few counts. To deal with all bursts including weak ones, here we propose the coherent search in Poisson statistics. We studied the difference between Poisson-based and Gaussian-based search methods by Monte Carlo simulations, and find that the Poisson-based search method has advantages compared to the Gaussian case, especially for weak bursts. Our results show that, for very weak bursts with very low number of counts, the Poisson-based search can provide higher significance than the Gaussian-based search, and its likelihood ratio (for background fluctuation) still generally follows the χ2 distribution, making the significance estimation of searched bursts very convenient. Thus, we suggest that the coherent search based on Poisson-likelihood ratio is more appropriate in the search for generic transients including very weak ones.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stac3075
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
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  • 5
    Online Resource
    Online Resource
    Energetic transients joint analysis system for multi-INstrument (ETJASMIN) for GECAM – I. Positional, temporal, and spectral analyses
    Oxford University Press (OUP) ; 2022
    In:  Monthly Notices of the Royal Astronomical Society Vol. 514, No. 2 ( 2022-06-17), p. 2397-2406
    Details
    In: Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP), Vol. 514, No. 2 ( 2022-06-17), p. 2397-2406
    Abstract: Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) is a dedicated mission, launched in December 2020, for gamma-ray transients, including gamma-ray bursts (GRBs) and soft gamma repeater (SGR) bursts in the multimessenger and multiwavelength astronomy era. Since GECAM consists of two independent spacecrafts (or say instruments), and the framework of data analysis for multiple spacecrafts is distinctive from that for only one spacecraft, which is the case for most GRB missions, we developed a dedicated pipeline called Energetic Transients Joint Analysis System for Multi-INstrument (ETJASMIN) for GECAM mission. This pipeline has been naturally extended to incorporate data from other gamma-ray instruments, including the operating missions, such as Insight-HXMT/HE, Fermi/GBM, Swift/BAT, INTEGRAL/SPI-ACS, Konus-Wind, and GRID, as well as the forthcoming missions, such as SVOM/GRM and HEBS. In this paper, we present this pipeline with a focus on the data analysis procedures, methodology, and results in terms of the localization, verification (classification), spectral, and temporal analyses of gamma-ray transients. We show that this pipeline could provide more accurate, reliable, and comprehensive results than that of individual spacecraft, which is beneficial for gamma-ray transients observation.
    Type of Medium: Online Resource
    ISSN: 0035-8711 , 1365-2966
    URL: Article
    DOI: 10.1093/mnras/stac999
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2022
    detail.hit.zdb_id: 2016084-7
    SSG: 16,12
    Location Call Number Limitation Availability
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