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ATEL # 1088; R. Starling, J.P. Osborne, P.T. O'Brien, M.R. Goad and P.A. Evans (University of Leicester)
on 30 May 2007; 18:14 UT
Password Certification: Rhaana Starling (email@example.com)
Subjects: Optical, X-ray, Transients
The unidentified optical transient PQT 070519 reported in ATel #1083 has been observed with Swift for a total of 9.8 ks over 3 epochs on 2007 May 24, 2007 May 27 and 2007 May 28.
The source is not detected in the 0.3-10 keV X-ray band down to a 3-sigma limiting flux of 3E-13 erg/cm2/s (assuming a nearby Gamma = 2 intrinsically unabsorbed power law source, and taking into account the Galactic absorption at this position of nH = 1.5E20 cm-2).
The source is marginally detected in the UVOT V-band filter with the following magnitudes:
|Date-obs||Texp (s)||mag||detection significance|
The long duration optical transient (>9 days), together with the X-ray non-detection suggests that this is not a Gamma-ray Burst or AGN, while the large distance between the source and the nearby galaxy does not favour a stellar capture event, ULX or supernova origin.
The faint pre-outburst limit suggests that any Galactic object must be in the halo or of very late spectral type. The duration and the >3 magnitude amplitude suggest a stellar flare is unlikely. Rather, we propose that a distant nova or dwarf nova eruption is consistent with the data to hand.
No further Swift observations are planned. We thank the Swift team for performing this ToO observation.