Swift-XRT detection of a new X-ray transient, Swift J103441.7-571527

ATel #15878; P. A. Evans (U. Leicester), S. Campana (INAF-OAB), K. L. Page (U. Leicester)
on 30 Jan 2023; 17:41 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Phil Evans (pae9@star.le.ac.uk)

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Title: Swift-XRT detection of a new X-ray transient, Swift J103441.7-571527 Authors: P.A. Evans (U. Leicester), S. Campana (INAF-OAB), K.L. Page (U. Leicester)

The LSXPS transient search facility (Evans et al., 2023) has detected a new X-ray transient in a Swift-XRT observation beginning at 2023-01-27 15:55 UT. The transient is located at: RA, Dec = 158.67137, -57.25824 degrees which is equivalent to:

RA (J2000): 10h 34m 41.13s
Dec(J2000): -57d 15' 29.7"


with an uncertainty of 2.6" (radius, 90% confidence). This equates to (285.2374, 0.8387) in Galactic coordinates.

We find no catalogued source at this position in SIMBAD or Vizier.

The source count-rate in the initial observation was 0.057 +/- 0.011 ct/sec. Three target-of-opportunity follow-up observations have been obtained with XRT, which reveal the source to have decayed steadily to 0.016 +/- 0.004 ct/sec by 2023-01-30 07:00 UT.

The source is heavily absorbed; a spectrum created from 7.1 ks data (the initial discovery observation and subsequent ToO data) can be fitted with an absorbed power-law, with NH = 1.8 (+0.9, -0.7)e22 cm^-2, and a photon index of 1.7 (+0.6, -0.5).

The object is undetected in UVOT, with 3-sigma upper limits (AB magnitudes):

u > 21.75
m2 > 22.20
w2 > 22.07

Given the hard spectrum and location in the Galactic plane, we suggest a cataclysmic variable as the most plausible explanation of this object; however, follow-up observations are encouraged.