Swift J1845.7-0037: Comparison of X-ray and optical positions

ATel #13219; J. A. Kennea (PSU)
on 23 Oct 2019; 14:54 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)

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Following up the ATEL #13218, which determined that the reported optical counterpart of the transient Swift J1845.7-0037 (e.g. ATELs #4130, #13191, #13195) is a combination of two stars, we derived the most accurate position based on Swift XRT and UVOT data, utilizing the methods described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 2009, 397, 1177). We find a refined position of RA/Dec(J2000) = 281.47783, -0.65966, which is equivalent to:

RA(J2000) = 18h 45m 54.68s,
Dec(J2000) = 00d 39m 34.8s,

with an estimated uncertainty of 1.5 arc-seconds radius (90% confidence). This position lies 0.49 arc-seconds from "Object A" reported in ATEL #13218, and 1.68 arc-seconds from "Object B". Although neither optical counterpart can be definitely ruled out, the Swift position clearly favors Object A as the counterpart of Swift J1845.7-0037.

This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.