The return to quiescence of Swift J1753.5-0127 in optical observed with LCO

ATel #16527; Kevin Alabarta, David M. Russell, D. M. Bramich, Payaswini Saikia and Sandeep Rout (NYU Abu Dhabi), M. Cristina Baglio (INAF-OAB), Jeroen Homan (Eureka Scientific), and Fraser Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU)
on 14 Mar 2024; 08:46 UT
Credential Certification: Kevin Alabarta (kalabarta@nyu.edu)

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The current outburst of Swift J1753.5-0127 was first detected on September 28, 2023 (MJD 60215.10) with the Las Cumbres Observatory (LCO) network (ATel #16262), when an increase of the optical brightness in the i'-band was observed with respect to the quiescence level (i' = 21.372 +/- 0.278 mag). Later, it was detected in X-rays with Chandra/ACIS-S, Swift/XRT (ATel #16272) and NICER (ATel #16318), and at radio wavelengths with MeerKAT (ATel #16281). The optical flux of Swift J1753.5-0127 remained approximately constant after October 4 (MJD 60222.87) at average magnitudes of V = 16.75 +/- 0.13, R = 16.50 +/- 0.12 and i' = 16.50 +/- 0.08 until the system was in Sun constraint (ATel #16314 and ATel #16318). New optical observations with ALFOSC/NOT on February 1, 2024 (MJD 60341.3) suggested that the outburst was in its decaying phase (ATel #16427). This was also observed with LCO, magnitudes of g' = 20.57 +/- 0.07, V = 20.60 +/- 0.12, r' = 19.65 +/- 0.04 and i' = 19.70 +/- 0.07 on February 12 (MJD 60352.24; ATel #16447).

We have continued our LCO optical monitoring of Swift J1753.5-0127 since then. The optical brightness of the system kept decreasing, and on March 01 (MJD 60370.63), the optical magnitudes (r' = 20.83 +/- 0.04, i' = 21.30 +/- 0.16, z_s = 20.05 +/- 0.12) were close to those of the system during quiescence (i' = 21.372 +/- 0.278 mag). The latest LCO observations occurred on March 08 (MJD 60377.79) and showed optical magnitudes of r' = 21.57 +/- 0.18 and i' = 20.96 +/- 0.20. These observations imply that Swift J1753.5-0127 has probably ended its outburst, which lasted ~150-160 days. A link to the LCO outburst light curve is included below.

Multi-wavelength observations of Swift J1753.5-0127 during quiescence are encouraged. We will continue to observe the system with LCO.

The LCO observations of Swift J1753.5-0127 are performed as part of an ongoing monitoring program of ~50 low-mass X-ray binaries (Lewis et al. 2008). LCO images are processed and reduced, and magnitudes are extracted and calibrated using a real-time data analysis pipeline, the "X-ray Binary New Early Warning System" (XB-NEWS; see Russell et al. 2019, Goodwin et al. 2020 and ATel #13451 for details).

This material is based upon work supported by Tamkeen under the NYU Abu Dhabi Research Institute grant CASS (Center for Astrophysics and Space Science).

LCO optical light curves of Swift J1753.5-0127