Periodic variability in the archival OGLE light curve of X-ray transient SRGA J124404.1-632232 (SRGE J124403.8-632231)

ATel #14361; P. Mroz (Caltech), A. Udalski (Warsaw U.), on behalf of the OGLE team
on 31 Jan 2021; 18:48 UT
Credential Certification: Przemek Mroz (pmroz@astrouw.edu.pl)

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A new X-ray source SRGA J124404.1-632232 (SRGE J124403.8-632231) (ATel #14357) detected by the Mikhail Pavlinsky ART-XC telescope on board the SRG observatory is located in the field GD1296 that has been regularly observed since 2013 by the OGLE survey as part of the OGLE Galaxy Variability Survey (Udalski et al. 2015, Acta Astron. 65, 1).

Semena et al. (ATel #14357) noted that the position of the X-ray source is consistent with that of a reddened star 2MASS 12440380-6322320. The archival I-band OGLE light curve of that source reveals long-term variability with a peak-to-peak amplitude of 0.4 mag, which is similar to that observed in other X-ray sources. In addition, the object exhibits low-amplitude (0.1 mag peak-to-peak) semi-regular variability with a period of 138 +/- 1 days.

The mean brightness (I=13.68 mag) and color (V-I=2.88 mag) of the star are consistent with those of a highly reddened HMXB as proposed by Semena et al. (ATel #14357) (interstellar reddening toward the object is approximately E(V-I)=2.44 as estimated from the extinction maps of Bovy et al. 2015 and Marshall et al. 2006). The 138 +/- 1 d periodicity in the archival OGLE light curve can be interpreted as the orbital period of the binary.

OGLE-IV Real Time Monitoring of X-ray Variables