LCO optical observations confirm the new outburst from EXO 0748-676
ATel #16646; M. C. Baglio (INAF-OAB), D. M. Russell, K. Alabarta, S. Rout, P. Saikia (NYUAD), L. Rhodes (U. Oxford), F. Lewis (Faulkes Telescope Project & Astrophysics Research Institute, LJMU)
on 11 Jun 2024; 10:26 UT
Credential Certification: Maria Cristina Baglio (cristina.baglio@brera.inaf.it)
Subjects: Optical, Binary, Neutron Star, Transient
The neutron star, low-mass X-ray binary EXO 0748-676 was discovered in 1985 (Parmar et al. 1985). It is a high inclination, eclipsing system, and its first outburst lasted more than 20 years, until in 2008 it decayed to quiescence (ATel #1812). A new outburst of EXO 0748-676 was recently reported from Swift/BAT and Swift/XRT observations (GCN #36653).
On MJD 60471 (2024 June 10) we observed the field of the source with the 1m telescope at SAAO, Sutherland in South Africa, part of the Las Cumbres Observatory (LCO) network. One 100-s observation was acquired with the g' and i' filters.
The optical counterpart of EXO 0748-676 is well detected at the following coordinates: RA=07:48:33.707, DEC=-67:45:07.41, consistent with the tabulated optical USNO position.
We performed aperture photometry and calibrated the magnitudes against field stars with magnitudes tabulated in the APASS catalogue.
We report the following calibrated magnitudes (in the AB system):
g'=17.60+/-0.05 on MJD 60471.6992
i'=17.66 +/- 0.07 on MJD 60471.6976.
These magnitudes are significantly brighter with respect to the average quiescent optical magnitude known for this source (R=22.4 mag; Hynes et al. 2009), therefore confirming the onset of a new outburst also at optical frequencies.
Optical monitoring of the source with LCO is ongoing. Further multiwavelength observations are encouraged to follow the evolution of the current outburst.
The LCO observations are part of an on-going monitoring campaign of ~ 50 low-mass X-ray binaries (Lewis et al. 2008) with LCO and the Faulkes Telescopes. This material is based upon work supported by Tamkeen under the NYU Abu Dhabi Research Institute grant CASS (Center for Astrophysics and Space Science).
