Swift Observations of 2MASS J070931-353746

ATel #11664; Dirk Grupe (Morehead State University) Norbert Schartel (ESA - ESAC) and S. Komossa (MPI f. Radioastronomie)
on 22 May 2018; 20:50 UT
Credential Certification: Dirk Grupe (dgrupe007@gmail.com)

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We report of Swift observations of 2MASS J070931-353746 which was discovered as a bright X-ray source during an XMM slew on 2018-April-26. Compared with the flux seen during the ROSAT All Sky Survey (Voges et al. 1999) the source appeared to be brighter by a factor of about 16. We performed a short 1ks Swift observation of 2MASS J070931-353746 on 2018-May-18. The X-ray spectral analysis found a rather flat X-ray spectrum with Gamma=1.55+/-0.25 and a flux in the 0.3-10 keV band of (5.27+/-0.81)e-15 W m^-2, which is comparable to the flux found during the XMM slew. 2MASS J070931.8-353746 had previously been observed by Swift as part of a fillin program to follow sources detected in the Second Palermo BAT survey (Cusumano et al. 2010, A&A 524, 64) in 2013 July. During these observations the source appeared to be brighter by a factor of 2 compared with our most recent observation. The UVOT enhanced X-ray position (Goad et al. 2007, A&A 476, 1401; Evans et al., 2009, MNRAS 397, 1177) based on all XRT observation is Ra-2000=07 09 31.8, Dec-2000= -35 37 47.8 with an uncertainty of 2.0". We observed in all 6 UVOT filters and found the following observed magnitudes in the Vega system (uncorrected for Galactic reddening): V=16.49+/-0.09, B=17.17+/-0.08, U=16.42+/-0.07. UVW1=16.61+/-0.08, UVM2=17.28+/-0.11, UVW2=17.30+/-0.08. During the observations in 2013 July 2MASS J070931-353746 was observed only in U, W1, and M2 and appeared to be fainter by 0.3mag, 0.4mag, and 0.2mag, respectively. The Galactic reddening in the direction of 2MASS J070931-353746 is E(B-V) = 0.350 mag (Schlafly & Finkbeiner 2011, ApJ 737, 103). We would like to thank Brad Cenko for approving our Swift ToO request and the Swift team for scheduling and executing the ToO quickly.