XB-NEWS confirms the new outburst from the black-hole candidate X-ray binary IGR J17091-3624

ATel #15284; 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 16 Mar 2022; 15:33 UT
Credential Certification: Payaswini Saikia (ps164@nyu.edu)

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IGR J17091–3624 is a transient Galactic black-hole candidate X-ray binary, discovered by the INTEGRAL observatory in 2003 April (Kuulkers et al. 2003, ATel #149). The source was in outburst in 1994, 2001, 2003, 2007, 2011 and 2016 (Katoch et al. 2020). Recently, X-ray monitoring with the Neil Gehrels Swift/BAT, and follow-up observations with NICER suggested that IGR J17091-3264 has started a new outburst (ATel #15282).

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 2008. On 2022 February 9 (MJD 59619.7), we detected an increase in the optical flux of the source, with r'= 20.41+/-0.03 mag, which is ~0.5 magnitudes brighter than the last measured quiescent magnitude before the Sun constraint (r'= 20.90+/-0.06 mag on 2021 October 10, MJD 59493.4). The most recent observation on 2022 March 13 (MJD 59651.7) confirms the outburst, with an optical increase of ~1 mag (r'= 19.3+/-0.01 mag).

We will continue monitoring the source at optical wavelengths with LCO. Further multi-wavelength observations are encouraged in the next few days/weeks to confirm the nature of this renewed activity, and monitor the rise of the outburst. 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 with LCO