Optical observations of the optical and X-ray transient ATLAS19bcxp = SRGA J043520.9+552226 = SRGE J043523.3+552234: a likely BL Lac object
ATel #13576; A. Lyapin (IKI), I. Zaznobin (IKI), G. Khorungev (IKI), G. Uskov (IKI), I. Mereminskiy (IKI), R. Burenin (IKI), S. Sazonov (IKI), M. Eselevich (ISZF SO RAN), M. Gilfanov (IKI, MPA), A. Lutovinov (IKI), M. Pavlinsky (IKI), R. Sunyaev (IKI, MPA)
on 21 Mar 2020; 18:36 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Ilya Mereminskiy (i.a.mereminskiy@gmail.com)
Subjects: Optical, X-ray, Request for Observations, Blazar, Transient
The optical transient ATLAS19bcxp associated with the X-ray transient SRGA J043520.9+552226 = SRGE J043523.3+552234 (I. Mereminskiy et al., ATel #13571) has been observed with the Sayan Observatory's AZT-33IK 1.6-m telescope using the ADAM medium- and low-resolution spectrograph and the Andor iKon imaging camera. The observations started on March 19, 2020, at 13:40 UTC. A spectrum with ~7A resolution in the 4000-9500A band with S/N~20 and a series of exposures in the SDSS gri filters with a total exposure of 240 s per filter were obtained.
The observed magnitudes for the transient are g=18.41, r=17.73, i=17.34, calibrated against secondary standards taken from the Pan-STARRS survey database. The optical spectrum, corrected for Galactic extinction, A(V)=2.798 (Schlafly et al., 2011), is nearly a power law F_lambda ~ lambda^-2.3, and does not show any readily distinguishable emission or absorption lines.
The extinction corrected optical flux and the unabsorbed X-ray flux are similar, ~a few 10^-11 erg/s/cm2. We also note that no host galaxy is detected in archival Pan-STARRS and WISE images.
Based on the combination of optical and X-ray properties, we suggest that this transient is most likely a BL Lac type object in an active state, with the optical and X-ray emission having the same synchrotron origin.
Further observations of this transient are encouraged.
