SRG/ART-XC detection of the new outburst of XTE J1637-498

ATel #18023; I. Mereminskiy(1), A. Semena(1), A. Lutovinov(1), S. Molkov(1), A. Tkachenko(1) (1:IKI RAS, Moscow)
on 31 Aug 2026; 19:02 UT
Credential Certification: Sergei Molkov (molkov@hea.iki.rssi.ru)

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During the observations of the Galactic Plane on Aug. 31, 2026, the Mikhail Pavlinsky ART-XC telescope onboard the SRG observatory detected a bright X-ray source at the position of RA, Dec = 249.2598, -49.8590 (estimated 90% containment radius of 10''). The error region includes a location of the historical X-ray transient XTE J1637-498 (ATel #1699), which was detected in 2008 by RXTE during a bulge scan at a similar flux level (2-4 mCrab). Optical-NIR counterpart was identified based on the XRT localization (ATel #1700, #1704, Curran et al., 2011) although no spectroscopic observations were made during the active episode in 2008. No information on the source activity in X-rays has been available since then.

The source flux is 4.5(±0.2)x10^-11 erg/cm2/s in the 4-12 keV band, corresponding to the luminosity of about 4x10³⁵ erg/s for a fiducial 8 kpc distance.

We are encouraging multiwavelength observations of this source in order to confirm a previously proposed NIR-optical counterpart and study the nature of the source.

The Mikhail Pavlinsky ART-XC telescope is the X-ray telescope on board the SRG observatory which was launched from the Baikonur cosmodrome on 13 July 2019 by the Proton rocket.