ART-XC/SRG observes the awakening of BHC 4U 1755-338

ATel #13606; I. Mereminskiy, A. Semena, M. Pavlinsky, A. Lutovinov, S. Molkov, I. Lapshov, A. Tkachenko (IKI RAS) on behalf of ART-XC collaboration
on 2 Apr 2020; 00:31 UT
Credential Certification: Ilya Mereminskiy (i.a.mereminskiy@gmail.com)

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In the course of the ongoing all-sky survey the ART-XC telescope on board the SRG observatory detected a bright X-ray source at a position of RA,Dec = 269.667, -33.806 (J2000, 90% error radius is 30") coinciding with the historical source 4U 1755-338, previously designated as a black hole candidate and microquasar. It is necessary to note that this source is thought to be in a quiescent state since the cease of the previous outburst in 1996.

Given the estimated source flux as 2.2±0.2x10^-10 erg/cm²/s in the 4-12 keV and 1.3±0.2x10^-10 erg/cm²/s in the 8-16 keV band we propose that 4U 1755-338 is again in the outburst.

We encourage observations in all wave bands to catch the development of this outburst.