Swift UVOT detection of the black hole transient 4U 1543-47

ATel #14715; Gayathri Raman, Jamie A. Kennea (Penn State) and Jon M. Miller (Univ. of Michigan)
on 15 Jun 2021; 02:52 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)

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We report the detection of a UV transient candidate at the location of the black hole binary 4U 1543-47 with the Ultraviolet/Optical Telescope (UVOT) on board the Neil Gehrels Swift Observatory. The source is detected in all the three UV filters - uvw1, uvw2 and uvm2 in the observation sequence 00014374002 with an exposure of 841.3 s starting at 07:56:36 on 2021-06-14 UT (MJD 59379.33).  The source is located at  RA = 15h 47m 08.19s, Dec = -47d 40m 10.0s (J2000). UV magnitudes and flux densities in all filters are given below:

Filter                lambda (A)         AB mag         Flux den (erg/s/cm^2/A)
uvw1                2500                15.77+/-0.10        7.84(70)x10^-15
uvw2                1800                16.87+/-0.04        4.72(16)x10^-15
uvm2                2200                17.05+/-0.04        3.33(11)x10^-15

The BH transient at this source location has been showing increased X-ray emission (ATels #14701, #14708) reaching a flux of 1.96e-7 erg/cm2/s (~8.2 Crab) in the 2-10 keV MAXI/GSC band. Multi-band follow up observations are encouraged.

We acknowledge the use of public data from the Swift data archive.