X-ray detection, possible variability and spectral evolution of Nova Del 2013 observed with Swift
ATel #5408; D. Donato (NASA/GSFC)
on 22 Sep 2013; 03:50 UT
Credential Certification: Davide Donato (davide.donato-1@nasa.gov)
Referred to by ATel #: 5429
Nova Del 2013 has been the target of a monitoring campaign by Swift since 2013 August 14. In the first days the source was not detected by the XRT, both in the PC and WT modes (ATel #5283, #5305, #5318). Starting with an observation on 2013 August 27 (2 ks exposure), and then on September 6 (1 ks) and 8 (1 ks), a handful of counts have been recorded by the XRT/PC at the position of the Nova. Although in all these observations the significance of detection is less than 3 in the 0.3-10 keV range, we estimated a corrected count rate of ~(8+-3)x10^-3 c/s, but we noted that almost all the counts are in the soft band (<2 keV). On September 10, no counts has been detected in a 1 ks exposure (upper limit 4x10^-3 c/s), while on September 12 (2 ks observation) the nova is finally detected (S/N>3 sigma) with a corrected count rate of ~(7.9+-2.3)x10^-3 c/s, with counts in the soft and hard bands with a 2:1 ratio. The X-ray source is then again undetected in the following 3 observations (September 14, 16, and 18, all ~1 ks exposures, upper limits ~4x10^-3 c/s). On September 19, the nova is once again detected in the 0.3-10 keV range with a corrected count rate of ~(8.5+-1.9)x10^-3 c/s in a ~4 ks exposure. The counts are almost evenly split between the soft and the hard bands.
Based on these initial results, we strongly encourage a deeper monitoring in the X-rays to better constrain the spectral parameters.
We thank the Swift PI, Neil Gehrels, and the Swift mission operations team for scheduling these observations.