J/ApJS/277/5 GECAM obs. of SGR J1935+2154. I. Burst catalog (Xie+, 2025)
GECAM observations of the Galactic magnetar SGR J1935+2154 during the 2021 and
2022 burst active episodes.
I. Burst catalog.
Xie S.-L., Cai Ce, Yu Y.-W., Xiong S.-L., Lin L., Zhao Yi, Zhang S.-N.,
Song L.-M., Wang P., Li X.-B., Xue W.-C., Zhang P., Zheng C., Zhang Y.-Q.,
Liu J.-C., Wang C.-W., Tan W.-J., Wang Y., Yu Z.-H., Feng P.-Y.,
Zhang J.-P., Xiao S., Zhao H.-S., Zhang W.-L., Zhang Y.-T., Huang Y.,
Zhao X.-Y., Ma X., Zheng S.-J., Li X.-Q., Wen X.-Y., Gong Ke, An Z.-H.,
Zhang D.-L., Yang S., Liu X.-J., Zhang F.
<Astrophys. J. Suppl. Ser., 277, 5 (2025)>
=2025ApJS..277....5X 2025ApJS..277....5X
ADC_Keywords: Stars, neutron; Gamma rays
Keywords: Magnetars ; Neutron stars ; Soft gamma-ray repeaters
Abstract:
Magnetars are neutron stars with ultrahigh magnetic fields
(∼1014-1015G). The magnetar SGR J1935+2154 is not only one of the
most active magnetars detected so far, but also the unique confirmed
source of fast radio bursts. The Gravitational Wave High-energy
Electromagnetic Counterpart All-sky Monitor (GECAM) is dedicated to
monitor gamma-ray transients all over the sky, including magnetar
short bursts. Here we report the GECAM observations of the burst
activity of SGR J1935+2154 from 2021 January to 2022 December, which
results in a unique and valuable data set for this important magnetar.
With a targeted search of GECAM data, 159 bursts from SGR J1935+2154
are detected by GECAM-B while 97 bursts are detected by GECAM-C,
including the X-ray burst associated with a bright radio burst. We
find that both the burst duration and the waiting time between two
successive bursts follow lognormal distributions. The period of burst
activity is 134±20 days, thus the burst activity could be generally
divided into four active episodes over these two years. Interestingly,
the hardness ratio of X-ray bursts tends to be softer during these two
years, especially during the active episode with radio bursts
detected.
Description:
As of writing this paper, the Gravitational Wave High-energy
Electromagnetic Counterpart All-sky Monitor (GECAM) constellation is
composed of four instruments: GECAM-A/B (launched in 2020 December),
GECAM-C (i.e., SATech-01/HEBS, launched in 2022 July), and GECAM-D
(i.e., DRO/GTM, launched in 2024 March). These four satellites are
all-sky monitors with a large field of view that can monitor various
gamma-ray transients, except for the area blocked by Earth. Both
GECAM-A and GECAM-B feature a dome-shaped array of 25 gamma-ray
detectors (GRDs) and eight charged particle detectors (CPDs), while
GECAM-C has 12 GRDs and two CPDs. All GECAM-B's GRDs and most of
GECAM-C's GRDs operate in two readout channels: high gain (HG,
6-300keV) and low gain (LG, 300keV-5MeV), which are independent in
terms of data processing, transmission, and dead time. The
event-by-event (EVT) data from GECAM's GRD detectors is used for
further analysis. GECAM achieves a high time resolution of 0.1us, with
a dead time of 4us for normal events and exceeding 69us for overflow
events. We note that in this work only GECAM-B/C data are used.
A total of 159 bursts for GECAM-B and 97 bursts for GECAM-C are
identified and listed in Tables 2 and 3. Among them there are
14 bursts that both GECAM-B and GECAM-C could observe, and a short
X-ray burst (2022-10-14T19:21:39.130 UTC) observed by GECAM-B and C is
associated with a bright radio burst FRB 20221014.
It is worth noting that about one-third of the GECAM bursts (i.e.,
60 bursts for GECAM-B and 36 bursts for GECAM-C) are invisible to
Fermi/GBM.
Objects:
---------------------------------------------------------------
RA (ICRS) DE Designation(s)
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19 34 55.67 +21 53 48.1 SGR 1935+2154 = NAME Sgr 1935+2154
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 86 159 SGR J1935+2154 burst list observed by GECAM-B
from 2021 January to 2022 December
table3.dat 86 97 SGR J1935+2154 burst list observed by GECAM-C
from 2022 October to December
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See also:
J/ApJS/212/6 : The McGill magnetar catalog (Olausen+, 2014)
J/ApJ/901/L7 : NIR obs. of the magnetar SGR 1935+215 with PGIR (De+, 2020)
J/ApJ/902/L43 : Fermi/GBM 2019 and 2020 bursts of SGR J1935+2154 (Lin+, 2020)
J/ApJ/904/L21 : NICER SGR 1935+2154 burst & persistent emission (Younes+, 2020)
J/A+A/675/A99 : FRBs search with Fermi-LAT (Principe+, 2023)
http://gecamweb.ihep.ac.cn/dailydatadownload.jhtml : GECAM continuous data
http://fermi.gsfc.nasa.gov/ : NASA Fermi homepage
http://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html : Fermi/GBM burst
catalog
Byte-by-byte Description of file: table[23].dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/159] Running sequence number
5- 14 A10 "Y/M/D" T.date Trigger date (UTC)
15 A1 --- --- [T]
16- 17 I2 h T.h Trigger hour (UTC)
18 A1 --- --- [:]
19- 20 I2 min T.m Trigger minute (UTC)
21 A1 --- --- [:]
22- 27 F6.3 s T.s Trigger second (UTC)
29- 36 A8 --- Template Template (1)
38- 43 F6.2 deg RAdeg [275.9/312.2] Right ascension (J2000)
45- 49 F5.2 deg DEdeg [2.2/42.4] Declination (J2000)
51- 55 F5.2 deg errPos [0.15/29.7] Position uncertainty
57- 61 F5.2 --- sigma [5/89.2] sigma value
63- 69 F7.2 ms Tbb [1.9/2662] Burst duration derived by
the Bayesian blocks algorithm
71- 78 F8.2 ms Tst [-1051/805.01] Burst start time relative
to the trigger time using the Bayesian
blocks algorithm
80- 82 A3 --- GBM Visible to GBM
84- 86 A3 --- GECAM Visible to GECAM (-C for Table 2 or
-B for Table 3)
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Note (1): We utilize the following spectral model templates:
the SoftBand function (default softer template for GRB searching), CPL
(a power law with high-energy exponential cutoff), OTTB (optically
thin thermal bremsstrahlung), Blackbody (BB), and Powerlaw.
See Section 2.1.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 22-Jan-2026