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Swift/BAT detects an outburst from the neutron star binary 1RXS J180408.9-342058

ATel #6997; H. A. Krimm (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC), W. Baumgartner (CRESST/GSFC/UMBC), J. Cummings (CRESST/GSFC/UMBC), N. Gehrels (GSFC), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), D. Palmer (LANL), T. Sakamoto (Aoyama Gakuin Univ.), M. Stamatikos (OSU/GSFC), T. Ukwatta (LANL)
on 27 Jan 2015; 13:31 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Hans A. Krimm (Hans.Krimm@nasa.gov)

Subjects: X-ray, Binary, Neutron Star, Transient

Referred to by ATel #: 7008, 7039, 7096, 7100, 7255, 7352

The Swift/BAT hard X-ray transient monitor has detected a bright outburst from a source consistent with the neutron star binary 1RXS J180408.9-342058. The outburst began on 2015 January 22 (MJD 57045) and has continued to brighten, reaching a level of 0.009 +/- 0.002 ct/s/cm^2 (~40 mCrab) in the 15-50 keV band on 2015 January 26. This source experienced a type-I X-ray burst on 2012 April 16, as detected by INTEGRAL and confirmed by Swift/XRT (Chenevez et al., ATel #4050). The 2012 burst was detected only in a short (45 s) bright burst and was not seen in longer exposures either by INTEGRAL or by BAT. The current outburst shows a very different time profile, with a slow rise over at least three days and no short outbursts detected by the BAT. Therefore, it is possible that the currently detected outburst is from an unrelated nearby object. The best BAT position (J2000) is

RA = 271.052 deg (18h 04m 12.42s)
dec = -34.313 deg (-34d 18m 47.6s),

which is 2.2' from 1RXS J180408.9-342058 (ATel #4050), within the estimated BAT error circle.

Swift target of opportunity observations have been approved, but since the source is currently in Sun constraint, the observations cannot be carried out until 2015 February 6 at the earliest.

Swift/BAT transient monitor light curve for 1RXS J180408.9-342058