Initial NICER observations of the GRB 200205A = Swift J0840.7-3516 and detection of short X-ray flaring activity
ATel #13456; W. Iwakiri (Chuo U.), K. Gendreau (NASA/GSFC), T. Enoto, T. Mihara (RIKEN), M. Nakajima, H. Negoro (Nihon U.), M. Serino (AGU), N. Kawai (Tokyo Tech), M. Ng (MIT), D. Chakrabarty (MIT), C. Malacaria (NASA-MSFC/USRA), D. Altamirano (University of Southampton)
on 7 Feb 2020; 05:02 UT
Credential Certification: Wataru Iwakiri (wataru.iwakiri@riken.jp)
Subjects: X-ray, Transient, Variables
Referred to by ATel #: 13495
We report the initial NICER observations of the Swift J0840.7-3516 (ATel #13452) , formerly called as GRB 200205A (GCN #26982).
First NICER observation of Swift J0840.7-3516 was carried out on 2020-02-05, from 14:44:47 to 21:08:59 UT (from 29336 to 52388 sec after the Swift/BAT trigger GCN #26982), with 1.9 ksec exposure intermittently. The lightcurve shows a slow decay with a powerlaw index of -0.17. The NICER count rate was 2.9 cps averaged over the first observation, which corresponds to 4.7 x 10-12 erg/cm2/s in 0.3-10 keV.
Second NICER observation was carried out on 2020-02-06, from 15:30:26 to 20:14:49 UT, with 1.6 ksec exposure intermittently. We found that Swift J0840.7-3516 showed short X-ray flaring activity with duration of several tens of seconds whose peak count rates reached about 4 times higher than the average rate (4.6 cps) over the second observation.
Although an 8.96 sec periodicity was reported by Swift (ATel #13452), no significant periodicity has been detected by NICER in either first or second observation.
NICER will continue to monitor this source. Multi wavelength followup observations are strongly encouraged.
