Swift J1910.2-0546 returns to quiescence : optical monitoring of the 2022 outburst
ATel #15303; Payaswini Saikia, David M. Russell, Kevin Alabarta, M. C. Baglio, D. M. Bramich (NYU Abu Dhabi), Fraser Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU)
on 29 Mar 2022; 13:35 UT
Credential Certification: Payaswini Saikia (ps164@nyu.edu)
Subjects: Optical, Black Hole, Transient
The black-hole candidate X-ray binary Swift J1910.2-0546 (also known as MAXI J1910-057) was first detected by Swift/BAT (ATel #4139) and MAXI/GSC (ATel #4140) on 2012 May 31 (MJD 56078) during an outburst. It was recently found to be in outburst again with significant X-ray enhancement detected by MAXI/GSC on 2022 February 4 (ATel #15214). Renewed activity of the source was also observed at radio wavelengths with the Arcminute Microkelvin Imager Large Array (ATel #15219) and optical wavelengths with the MITSuME 50 cm telescope Akeno (ATel #15226) and the Zwicky Transient Facility (ATel #15229).
We have been monitoring the source at optical wavelengths with the Las Cumbres Observatory (LCO) 2-m and 1-m robotic telescopes, as part of a monitoring campaign of ~50 low-mass X-ray binaries (Lewis et al. 2008), since its discovery in 2012. We first detected the source during the recent activity after it came out of the Sun constraint, on 2022 February 13 (MJD 59623.3). At that time, it was already at the peak, or at the early decline stage of the outburst (with B=17.80+/-0.02 mag, V=17.08+/-0.01 mag, R=16.57+/-0.01 mag, i'=16.46+/-0.01 mag and Y=16.17+/-0.05 mag). This was ~1 mag fainter than its 2012 outburst, which had peak magnitudes of V=15.71+/-0.01 mag, R=15.38+/-0.01 mag and i'=15.41+/-0.01 on 2012 June 25 (MJD 56103.6). After its detection, it had a steady decline in all the optical bands (with an average decline of ~0.1 mags/day). The most recent observation of the source is consistent with being in quiescence, with i'= 20.70+/-0.14 mag on 2022 March 20 (MJD 59658.8) and R=20.76+/-0.24 mag on 2022 March 28 (MJD 59666.4). We note that during quiescence the optical magnitudes of the source with LCO remain in the range of i'=20.7-21.7 mags, but this includes some flux within the aperture from a couple of nearby faint stars (Lopez et al. 2019).
The optical monitoring with LCO is ongoing; multiwavelength observations in order to confirm the end of the outburst are encouraged. All LCO photometric analysis and data calibration were performed using the "X-ray Binary New Early Warning System" pipeline (XB-NEWS; see Russell et al. 2019 and Goodwin et al. 2020 for details).
Optical light curve of the 2022 outburst
