An X-ray source associated with a Vista Variables Survey nova candidate nova
ATel #8625; M. Orio (INAF-Padova, Italy and University of Wisconsin, USA), K. Mukai (NASA-Goddard Space Flight center and University of Maryland-Baltimore County, MD, USA) and M. Della Valle (INAF-Napoli, Italy)
on 2 Feb 2016; 08:43 UT
Credential Certification: Marina Orio (orio@astro.wisc.edu)
Subjects: Infra-Red, X-ray, Cataclysmic Variable, Nova, Transient, Variables
We report that one of the ten Galactic transients proposed to be novae, discovered in the Vista-Variables-Via Lactea (VVV) Survey disk area by Saito et al. (ATel 8602), VVV-NOV-13, is spatially coincident with a faint, hard X-ray source observed in 2011 June 16 and 17 for 19700 s in a survey of the NORMA spiral arm with the Chandra ACIS-I camera (P.I. Tomskick). The source is detected in the archival image with a count rate 0.0011+-0.0003 cts s(-1), despite the large extinction in this region of the sky (A_V=71.72 is estimated in the Schlegel et al. 1998 maps for a 5 arcminutes region around the target's position). No X-ray source was observed at the putative nova's position with the ROSAT PSPC in a 12450 s long exposure on January 6 1990, and with the ASCA GIS and SIS instruments in exposures of 8300 and 7500 s respectively on April 9 1997. Although the early exposures do not match in depth, spatial resolution and, in ROSAT's case, energy range, the Chandra observation, the previous non-detection and the position coincidence suggests that the objected detected in 2011 was a transient source associated with a nova event, since many classical and recurrent novae are observed as transient X-ray sources in the 1-10 keV energy band. There were no sufficiently deep X-ray observations of this field after 2011 June, and no other deep X-ray observations of the fields of the other VVV Survey nova candidates are available for the year after the VISTA detections. We (Mukai et al. 2008, ApJ 677, 1248) suggested that many transients in the Galactic center region are novae. This detection of an X-ray source associated with a nova in a region of the sky affected by high extinction is consistent with our suggestion.
