Swift detects rapid outburst decay from MAXI J1957+032
ATel #15457; Amar Deo Chandra (IISER Kolkata)
on 23 Jun 2022; 07:37 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Amar Deo Chandra (amar.deo.chandra@gmail.com)
Subjects: X-ray, Binary, Neutron Star, Transient, Pulsar
A new outburst of the faint X-ray transient MAXI J1957+032 was detected by the MAXI/GSC nova alert system which triggered on this source at 17:26 UT on June 18, 2022 (ATel #15440). Follow-up NICER observations detected 314 Hz coherent pulsations from this transient source making it a new accreting millisecond X-ray pulsar (ATel #15444). No indication of decrease in flux was detected during early observations of this source (ATel #15440, #15444, #15446). However, suggestions of decrease in the source intensity had been detected in NICER monitoring observations of this source (ATel #15456).
The source had been observed for a total duration of ~1.5 ks with Swift/XRT in Photon Counting (PC) mode from 01:47 UT to 14:43 UT on 22 June, 2022. The source is faintly detected in the PC mode Swift/XRT observations. The source was detected in Swift/XRT observations performed in Windowed Timing Mode on June 21, 2022 having averaged count rate of ~0.6 cts/s. The estimated timescale of rapid decay of the outburst is about 0.4 days. This decay timescale is similar to the timescale obtained during the May 2015 outburst of the source (ATel #7520). The inferred duration of the June 2022 outburst of this source is at least about 3.9 days.
Further Swift observations are planned to monitor the activity of the source.
We thank the Swift team for scheduling ToO observations.
