Swift observations of the transient near PGC143111
ATel #8171; Daniele Malesani (DARK/NBI), Samantha R. Oates (IAA/CSIC and UCL/MSSL)
on 15 Oct 2015; 14:43 UT
Credential Certification: Daniele Malesani (email@example.com)
Subjects: Optical, Ultra-Violet, X-ray, Transient
The Swift satellite observed the field of the unusual MASTER transient close to PGC143111 (2MASX J00000895-3341350), between 2015 Oct 14.74 and 14.77 UT, that is approximately 0.77 days after the initial detection reported by Popova et al. (ATel #8166), for a total of 2 ks with both the XRT and UVOT instruments.
No source is detected at the location of the transient (Popova et al., ATel #8166), in either the UV and X-ray bands. In the 0.3-10 keV band, an upper limit can be set of 5*10-3 c s-1, roughly corresponding to 2*10-13 erg cm-2 s-1 assuming a power-law spectrum with photon index of 2. The limits derived from UVOT are U > 20.8 and UVM2 > 20.8 (Vega magnitudes).
The MASTER transient lies at a distance of ~21 arcsec from the center of the galaxy PGC143111 at z = 0.0572, which corresponds to ~24 kpc in projection. Based on probabilistic arguments (e.g. Bloom et al. 2002, AJ, 123, 1111), the chance probability to find a galaxy this bright (R ~ 15.5) is around 1%. As such, the association between the MASTER transient and PGC143111 is not firmly established.
We thank the Swift PI, Neil Gehrels, and the Swift Operations Team, in particular Kim L. Page, for rapidly carrying out these observations.