Swift/MAXI follow-up of recent outburst from X-ray pulsar 2S 1553-542
ATel #14308; Manoj Mandal (MCC), Sabyasachi Pal (MCC/ICSP) and Mangal Hazra (MCC)
on 8 Jan 2021; 20:39 UT
Credential Certification: Sabyasachi Pal (sabya.pal@gmail.com)
Subjects: X-ray, Neutron Star, Transient, Pulsar
The X-ray pulsar 2S 1553-542 was discovered using the rotation modulation collimator onboard Small Astronomy Satellite 3 in 1975 (Apparao et al., 1978, Nature, 271, 225). During the outburst of 2008, the pulsar was detected with a spin period of ~9.28 s with a single peak sinusoidal type pulse profile (ATEL #1373, Pahari & Pal 2012, MNRAS, 423, 3352).
Recently, an outburst is reported from the X-ray pulsar in hard X-ray band, after a long time (the last outburst detected by Fermi/GBM was in February 2014) using Fermi/GBM (ATEL #14301). The outburst started on 21st December 2020. The flux reached a maximum value of 0.06±0.01 Crab (15-50 keV) on MJD 59213 as detected by Swift/BAT. There is no available data points from SWIFT/BAT after MJD 59214. The flare was also detected by MAXI/GSC (2-20 keV), with a maximum flux of 0.024±0.004 Crab on 6th January 2021 (MJD 59220.5).
A follow-up observation was done by Swift/XRT on 7th January 2021 (MJD 59221.289). From the preliminary timing analysis, using the barycenter and background corrected light curve, we found the spin period of the X-ray pulsar is ~9.30±0.01 s. The pulse profile is nearly sinusoidal with single peak nature, which is more or less similar type to the previous outburst (Pahari & Pal, 2012, MNRAS, 423, 3352). The energy spectrum (2-8 keV) of 2S 1553-542 is well fitted with the model phabs×(powerlaw+bbody). The fitted photon index is 7.9±1.3 and kT is 1.5±0.1 with flux 1.55 × 10-8 ergs/cm2/s.
Further observations in all wavelengths are encouraged.
This research has made use of MAXI data provided by RIKEN, JAXA and the MAXI team.
