New Galactic Center Transient is a nearby late-type dwarf star flare
ATel #12932; Thomas J. Maccarone (Texas Tech), Arash Bahramian (Curtin University of Technology), Greg Sivakoff, Craig Heinke (University of Alberta) on behalf of a larger collaboration
on 12 Jul 2019; 18:06 UT
Credential Certification: Tom Maccarone (thomas.maccarone@ttu.edu)
Subjects: Optical, Ultra-Violet, X-ray, Star, Transient
A new X-ray transient was reported in ATel #12927 at RA=266.20167, DEC=-29.124663. Our Swift Galactic Bulge Survey (Atel #10265, ATel #12751) obtained X-ray data on MJD 58675.67592, about 12 hours after the data for the Swift Galactic Center monitoring program, and detected no photons from the position of this source in 110 seconds.
We searched Vizier around the position of this source and note the presence of a star in Gaia DR2 at 266.2002622051860, -29.1256269167355, with a parallax of 17.28+-0.14 milli-arcseconds (i.e. a distance of 58 pc), extremely red colors, and a K-band absolute magnitude using the 2MASS photometry corresponding to an M5 star.
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We then looked at the UVOT data from the time of the X-ray source flare detection and find that this star is at UVW1=18.54 according to the standard catalog pipeline (for comparison the star is at 19.8 in the BJ filter in the Initial Gaia Source Catalog, and has consistently red colors in other filters). In a slightly longer UVW1 observation made on September 23, 2014, there was no detection of this star in the UVW1 image. The late type dwarf star was thus flaring in UV during the Swift Galactic Center observations.
