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Swift observation of LSQ12dyw

ATel #4346; R. C. Reis, M . T. Reynolds, J. M. Miller, B. P. Miller (University of Michigan), E. Hadjiyska (Yale University)
on 29 Aug 2012; 20:39 UT
Credential Certification: Rubens C. Reis (rdosreis@umich.edu)

Subjects: Ultra-Violet, X-ray, AGN, Black Hole, Supernovae, Transient

We report on a Swift TOO observation of the potential tidal disruption candidate LSQ12dyw (ATEL #4299, #4329). Swift observed this source on 2012-08-28 for 955s. In this time, the X-ray telescope (0.2-10keV) did not detect any significant emission at the coordinates of the SDSS galaxy. The count rate in a 47’’ circular region centered at 23:29:24.82 | -07:23:20.4 (J2000, ATEL #4299) is 2.15E-3 count/s. Assuming a Gamma=1.8 powerlaw, this gives an unabsorbed upper limit on the flux of ~8.2E-14 erg/cm2/s. If LSQ12dyw contains a 10E6 solar-mass black hole, the radiative output must be <0.012Ledd (i.e. ~1.6E42erg/s assuming a luminosity distance for z=0.09 of DL=406.5 Mpc, Ho = 71, OmegaM=0.270, OmegaVac = 0.730). Data were simultaneously collected by the UVOT and a source was clearly present at the position of the SDSS galaxy with a V-band (AB) mag of 18.58 +/- 0.34. The magnitudes in the other bands are: 18.82 +\-0.24 at b 18.87 +\-0.15 at u 19.11 +\- 0.13 at uvw1 (2600A) 19.41+\- 0.10 at uvw2 (1928A) This detection is consistent with there being an excess in the UV flux in comparison to GALEX J232924.7-072320, with a FUV (1500A) magnitude of 22+\-0.24. Multi-wavelength observations are encouraged to fully reveal the nature of this transient. We thank the Swift team for having performed this observation.