J/ApJ/902/L43 Fermi/GBM 2019 and 2020 bursts of SGR J1935+2154 (Lin+, 2020)
Fermi/GBM view of the 2019 and 2020 burst active episodes of SGR J1935+2154.
Lin L., Gogus E., Roberts O.J., Baring M.G., Kouveliotou C., Kaneko Y.,
van der Horst A.J., Younes G.
<Astrophys. J., 902, L43 (2020)>
=2020ApJ...902L..43L 2020ApJ...902L..43L
ADC_Keywords: Pulsars; Gamma rays
Keywords: Magnetars ; Soft gamma-ray repeaters
Abstract:
We present temporal and time-integrated spectral analyses of
148 bursts from the latest activation of SGR J1935+2154, observed with
the Fermi/Gamma-ray Burst Monitor from 2019-October-4 through
2020-May-20, excluding an ∼130s segment with a very high burst density
on 2020-April-27. The 148 bursts presented here are slightly longer
and softer than bursts from earlier activations of SGR J1935+2154, as
well as from other magnetars. The long-term spectral evolution trend
is interpreted as being associated with an increase in the average
plasma loading of the magnetosphere during bursts. We also find a
trend of increased burst activity from SGR J1935+2154 since its
discovery in 2014. Finally, we find no association of typical radio
bursts with X-ray bursts from the source. This contrasts the
association of FRB 200428 with an SGR J1935+2154 X-ray burst, which is
to-date unique among the magnetar population.
Description:
Our analysis of magnetar bursts, which typically emit at energies
<200keV, is based on the continuous time-tagged event (CTTE) data of
NaI detectors of the Fermi/Gamma-ray Burst Monitor (GBM), which
provide the highest temporal (2µs) and spectral (128 channels)
resolutions.
We searched for bursts in the intervals from 2019 September 25 through
2019 November 20 (22 bursts) and 2020 April 1 through 2020 May 31
(126 bursts).
Objects:
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RA (ICRS) DE Designation(s)
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19 34 55.68 +21 53 48.2 SGR J1935+2154 = PSR J1935+2154
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 149 148 The SGR J1935+2154 burst list
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See also:
J/ApJS/212/6 : The McGill magnetar catalog (Olausen+, 2014)
J/ApJS/218/11 : The 5yr Fermi/GBM magnetar burst catalog (Collazzi+, 2015)
J/ApJ/901/L7 : NIR obs. of Gal. magnetar SGR 1935+215 with PGIR (De+, 2020)
J/ApJ/904/L21 : NICER SGR 1935+2154 burst & persistent emission (Younes+, 2020)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/148] Running sequence number
5 A1 --- f_Seq [T] T = Burst triggered GBM
7- 10 I4 yr Str.Y [2019/2020] Year of burst start time (UTC)
12- 14 A3 "month" Str.M Month of burst start time (UTC)
16- 17 I2 d Str.D Day of burst start time (UTC)
19- 20 I2 h Str.h Hour of burst start time (UTC)
22- 23 I2 min Str.m Minute of burst start time (UTC)
25- 30 F6.3 s Str.s Second of burst start time (UTC)
32- 36 F5.3 s tau-bb [0.013/2.61] Bayesian block duration
38- 43 F6.2 10-14J/cm2 F [0.17/189.8] Fluence in 8-200keV range
45- 48 F4.2 10-14J/cm2 e_F [0.02/0.7] Uncertainty in F
50- 54 F5.2 keV Epeak [13.6/56.5]? Peak energy
56- 61 F6.3 keV e_Epeak [0.1/10.2]? Lower uncertainty in Epeak
63- 68 F6.3 keV E_Epeak [0.1/14]? Upper uncertainty in Epeak
70- 75 F6.3 --- Gamma [-2.71/0.85]? Photon index
77- 82 F6.4 --- e_Gamma [0.03/0.6]? Lower uncertainty in Gamma
84- 89 F6.4 --- E_Gamma [0.03/0.72]? Upper uncertainty in Gamma
91- 97 F7.3 --- C-Stat1 [71.7/640]? C-Stat for model 1 (1)
99-101 I3 --- DoF1 [64/337]? Degrees of Freedom for
model 1 (1)
103-107 F5.3 keV kTlow [1.9/9.8]? Low BB temperature
109-113 F5.3 keV e_kTlow [0.15/2.6]? Lower uncertainty in kTlow
115-119 F5.3 keV E_kTlow [0.17/1.9]? Upper uncertainty in kTlow
121-125 F5.2 keV kThigh [9.18/20.1]? High BB temperature
127-131 F5.3 keV e_kThigh [0.2/5.3]? Lower uncertainty in kThigh
133-137 F5.3 keV E_kThigh [0.25/7.1]? Upper uncertainty in kThigh
139-145 F7.3 --- C-Stat2 [70.7/631]? C-Stat for model 2 (2)
147-149 I3 --- DoF2 [63/336]? Degrees of Freedom for
model 2 (2)
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Note (1): The Comptonized model (COMPT) model fit or optically thin
thermal bremsstrahlung (OTTB)/power law (PL) fit.
The Comptonized model is an exponentially cutoff power law with the
photon number flux F∝EΓexp[-E(2+Γ)/Epeak, where
Epeak is the peak energy and Γ is the photon index.
Note (2): The sum of two blackbody functions (BB+BB) model fit or BB fit.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Apr-2022