Long-term J-band variability of the highly reddened X-ray transient SRGA J204318.2+443815 = SRGE J204319.0+443820 = PGIR20fah from Palomar Gattini-IR
ATel #14234; K. De (Caltech), M. Hankins (Caltech), M. M. Kasliwal (Caltech), J. Sokoloski (Columbia), M. Ashley (UNSW), A. Babul (Columbia), V. Karambelkar (Caltech), R. M. Lau (ISAS/JAXA), A. Moore (ANU), E. O. Ofek (Weizmann), M. Sharma (Columbia), J. Soon (ANU), R. Soria (NAOC), T. Travouillon (ANU) on behalf of the Palomar Gattini-IR team
on 30 Nov 2020; 23:05 UT
Credential Certification: Kishalay De (kde@astro.caltech.edu)
Subjects: Infra-Red, Optical, X-ray, Transient, Variables
We report on the detection of large amplitude J-band variability of
the Galactic X-ray transient SRGA J204318.2+443815 = SRGE
J204319.0+443820 reported by the SRG mission (ATel #14206). Palomar
Gattini-IR is a wide-field NIR transient survey scanning the entire
Northern sky to a median depth of J = 15.7 AB mag every two nights (De
et al. 2020; Moore & Kasliwal 2019).
The reported SRG transient is coincident with a bright 2MASS
counterpart of J ~ 12.7 Vega mag. Transient variability from the
source was first detected on UT 2020-07-24 after the source emerged
from solar conjunction and saved as the source PGIR20fah. Forced
photometry at the source location on unsubtracted images reveal a
highly variable IR counterpart (amplitude ~ 0.4 mag) with a mean
magnitude of ~ 12.3 mag in 2019. The source has systematically
brightened to a mean magnitude of ~ 12.0 mag in the 2020 data with
similar variability, confirming an association with the reported X-ray
transient.
The integrated extinction along the line of sight is ~ 9 mag in r band
and ~ 13 mag in g band (Schlafly et al. 2011), consistent with the
extremely red colors of the source. We encourage multi-wavelength
follow-up, in particular, infrared spectroscopy given the highly
reddened nature of the source.
