J/ApJ/904/L21 NICER SGR 1935+2154 burst and persistent emission (Younes+, 2020)
NICER View of the 2020 Burst Storm and Persistent Emission of SGR 1935+2154.
Younes G., Guver T., Kouveliotou C., Baring M.G., Hu C.-P., Wadiasingh Z.,
Begicarslan B., Enoto T., Gogus E., Lin L., Harding A.K.,
van der Horst A.J., Majid W.A., Guillot S., Malacaria C.
<Astrophys. J., 904, L21 (2020)>
=2020ApJ...904L..21Y 2020ApJ...904L..21Y
ADC_Keywords: Stars, neutron; X-ray sources; GRB
Keywords: Neutron stars ; Magnetars ; Soft gamma-ray repeaters
Abstract:
We report on NICER observations of the magnetar SGR1935+2154, covering
its 2020 burst storm and long-term persistent emission evolution up to
∼90days postoutburst. During the first 1120s taken on April 28
00:40:58 UTC, we detect over 217 bursts, corresponding to a burst rate
of >0.2bursts/s. Three hours later, the rate was 0.008bursts/s,
remaining at a comparatively low level thereafter. The T90 burst
duration distribution peaks at 840ms; the distribution of waiting
times to the next burst is fit with a lognormal with an average of
2.1s. The 1-10keV burst spectra are well fit by a blackbody, with an
average temperature and area of kT=1.7keV and R2=53km2. The
differential burst fluence distribution over ∼3 orders of magnitude is
well modeled with a power-law form dN/dF ∝F-1.5±0.1. The
source persistent emission pulse profile is double-peaked hours after
the burst storm. We find that the burst peak arrival times follow a
uniform distribution in pulse phase, though the fast radio burst
associated with the source aligns in phase with the brighter peak. We
measure the source spin-down from heavy-cadence observations covering
days 21-39 postoutburst, ν=-3.72(3)x10-12Hz/s, a factor of 2.7
larger than the value measured after the 2014 outburst. Finally, the
persistent emission flux and blackbody temperature decrease rapidly in
the early stages of the outburst, reaching quiescence 40days later,
while the size of the emitting area remains unchanged.
Description:
NICER is a nonimaging X-ray timing and spectral instrument providing a
collecting area of 1900cm2 at 1.5keV. It consists of 56 coaligned
X-ray-concentrating optics covering a (30') field of view, 52 of which
are currently operating. We utilize all 52 detectors for our burst
analyses. NICER started observing SGR1935+2154 on 2020 April 28 at
00:40:58 UTC.
Objects:
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RA (2000) DE Designation(s)
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19 34 55.68 +21 53 48.2 SGR1935+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
table1.dat 80 43 Spectral properties of the persistent emission
table2.dat 98 223 *Burst properties
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Note on table2.dat : Times of bursts are from 2020-04-28 UTC.
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See also:
J/A+A/527/A139 : X-ray bursting neutron star atmos. models (Suleimanov+, 2011)
J/A+A/545/A120 : X-ray burst neutron star atmos. models II (Suleimanov+, 2012)
J/ApJS/218/11 : The 5 year Fermi/GBM magnetar burst catalog (Collazzi+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 10 I10 --- ObsID NICER observation identifier
12- 20 F9.3 d MJD [58967/59057] Modified Julian Date, exposure
midpoint, MJD-2400000.5
22- 28 F7.2 s Texp [222/5177] Exposure
30- 33 F4.2 /s CR [0.12/2.74] Count rate
35- 38 F4.2 /s e_CR [0.01/0.2] Uncertainty in CR
40- 43 F4.2 keV kT [0.34/0.79] Average temperature
45- 48 F4.2 keV e_kT [0.01/0.1] Lower uncertainty on kT
50- 53 F4.2 keV E_kT [0.01/0.1] Upper uncertainty on kT
55- 58 F4.2 10-14W/m2 Flux [0.14/2.2] 0.3-10keV flux, unabsorbed
60- 63 F4.2 10-14W/m2 e_Flux [0.01/0.1] Lower uncertainty on F
65- 68 F4.2 10-14W/m2 E_Flux [0.01/0.1] Upper uncertainty on F
70- 72 F3.1 km Rad [1.5/4] Radius
74- 76 F3.1 km e_Rad [0.1/2] Lower uncertainty on Rad
78- 80 F3.1 km E_Rad [0.1/3] Upper uncertainty on Rad
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 1 I1 --- GTI [1/4] uninterrupted good time interval
3- 5 I3 --- Burst [1/223] Burst number
7- 8 I2 h Tst.h [0/7] Burst Start time, hour UTC
10- 11 I2 min Tst.m Burst Start time, minute UTC
13- 18 F6.3 s Tst.s Burst Start time, second UTC
20- 21 I2 h Tet.h [0/7] Burst End time, hour UTC
23- 24 I2 min Tet.m Burst End time, minute UTC
26- 31 F6.3 s Tet.s Burst End time, second UTC
33- 34 I2 h Tpeak.h [0/7] Burst Peak time, hour UTC
36- 37 I2 min Tpeak.m Burst Peak time, minute UTC
39- 44 F6.3 s Tpeak.s Burst Peak time, second UTC
46- 51 F6.3 s T90 [0.06/30.9] burst duration
53- 56 F4.2 keV kT [0.5/3.9]? average temperature
58- 61 F4.2 keV e_kT [0.02/1]? Lower uncertainty on kT
63- 66 F4.2 keV E_kT [0.02/5]? Upper uncertainty on kT
68- 73 F6.2 km2 R2 [2/970]? emission area
75- 77 I3 km2 e_R2 [1/560]? Lower uncertainty on R2
79- 82 I4 km2 E_R2 [3/1300]? Upper uncertainty on R2
84- 88 F5.2 [10-3W/m2] logF [-9.6/-6.26]? log10, 0.5-10 keV Flux,
erg/s/cm2
90- 93 F4.2 [10-3W/m2] e_logF [0.01/0.2]? Lower uncertainty on logF
95- 98 F4.2 [10-3W/m2] E_logF [0.01/0.2]? Upper uncertainty on logF
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 25-Mar-2022