VVV-NOV-004: the innermost nova candidate in the Galactic bulge

ATel #6022; R. K. Saito (Universidade Federal de Sergipe), I. Dekany (Millennium Institute of Astrophysics, Pontificia Universidad Catolica de Chile), D. Minniti (Pontificia Universidad Catolica de Chile, Vatican Observatory, Millennium Institute of Astrophysics), M. Catelan (Pontificia Universidad Catolica de Chile, Millennium Institute of Astrophysics), R. Angeloni (Pontificia Universidad Catolica de Chile, Max-Planck-Institut fur Astronomie)
on 28 Mar 2014; 18:17 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Roberto Saito (rsaito@astro.puc.cl)

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We report the discovery of a likely Galactic nova in the VVV Survey data (vvvsurvey.org; Minniti et al. 2010, New Astronomy, 15, 433). Observations taken during 2010-2013 show the presence of a stellar source fading in brightness from April 21 2010 to September 25 2013 (see table below). The light-curve of VVV-NOV-004 follows the expected behavior of a nova during the late stages of an outburst, fading by Delta_Ks>2.2 mag over 1253 days.

The coordinates of VVV-NOV-004 are (RA,DEC)=17:43:33.52, -30:30:29.10 or (l,b) =1.57391,-0.44046, with an accuracy of ~0.35 arc seconds. Previous near-IR observations from UKIDSS (Lucas et al. 2008, MNRAS, 391, 136) and 2MASS (Skrutskie et al. 2006, AJ, 131, 1163) show no detection at the object position. The possible nova outburst occurred before April 21 2010, when the object is first detected as a stellar source with Ks=13.17 mag and (J-Ks)=4.32 mag. In the latest data-point currently available the object has Ks=15.40 mag.

According to the VVV reddening maps (Gonzalez et al., 2012, A&A, 543, 13) assuming the Nishiyama et al. (2009, ApJ, 696, 1407) extinction law, the extinction for a 2 arcmin region around the target position is E(J-Ks)=2.77, corresponding to AV=12.4 mag.

There are no previous entries in the literature for the target position. Confirming the nature of the object, VVV-NOV-004 would become the innermost known nova in the Galactic bulge. We recommend further observations in order to discard the hypotheses of a rare long period variable or an OH/IR star with P>1250 days.

 
VVV-NOV-004 Table of Observations 
 
Date  (UT)     filter   mag    flag 
2010-04-22.26165 H  14.93+/-0.03 -1 
2010-04-22.26387 Ks 13.17+/-0.01 -1 
2010-04-22.26670 J  17.49+/-0.08  1 
2010-09-12.08719 Ks 13.70+/-0.02 -1 
2011-08-02.16921 Y  beyond detection 
2011-08-02.17273 Z  beyond detection 
2011-08-18.13316 Ks 14.51+/-0.05 -1 
2011-09-25.07396 Ks 14.51+/-0.05 -1 
2011-10-05.03677 Ks 14.60+/-0.05 -1 
2012-03-21.29173 Ks 14.93+/-0.06 -1 
2012-03-22.32199 Ks 14.91+/-0.06 -1 
2012-06-08.16173 Ks 15.01+/-0.07 -1 
2012-06-16.11515 Ks 14.86+/-0.06 -1 
2012-06-23.14674 Ks 14.86+/-0.06 -1 
2012-07-04.08586 Ks 14.93+/-0.06 -1 
2012-07-06.05816 Ks 14.92+/-0.07 -1 
2012-07-08.19765 Ks 14.90+/-0.06 -1 
2012-07-21.13991 Ks 14.95+/-0.06 -1 
2012-07-22.16774 Ks 14.91+/-0.07 -1 
2012-07-24.18613 Ks 14.95+/-0.07 -1 
2012-08-01.06683 Ks 15.02+/-0.07 -1 
2012-08-02.04930 Ks 15.09+/-0.07 -1 
2012-08-04.98966 Ks 15.05+/-0.08 -1 
2012-08-15.04089 Ks 15.10+/-0.07 -1 
2012-09-25.02155 Ks 15.13+/-0.08 -1 
2012-09-26.00644 Ks 15.12+/-0.08 -1 
2012-09-27.00439 Ks 15.05+/-0.07 -1 
2012-09-28.04242 Ks 15.11+/-0.08 -1 
2013-03-15.31145 Ks 15.24+/-0.09 -1 
2013-03-16.30112 Ks 15.16+/-0.08 -1 
2013-03-22.35854 Ks 15.20+/-0.08 -1 
2013-06-18.13819 Ks 15.28+/-0.09 -1 
2013-07-11.15499 Ks 15.34+/-0.10 -1 
2013-07-14.18371 Ks 15.32+/-0.09 -1 
2013-08-02.97208 Ks 15.38+/-0.10 -1 
2013-08-03.03426 Ks 15.41+/-0.10 -1 
2013-08-03.14690 Ks 15.40+/-0.10 -1 
2013-08-04.02615 Ks 15.35+/-0.10 -1 
2013-08-05.07738 Ks 15.41+/-0.10 -1 
2013-08-19.01484 Ks 15.37+/-0.10 -1 
2013-09-24.02190 Ks 15.40+/-0.10 -1 
2013-09-26.03900 Ks 15.40+/-0.10 -1 

The VVV data are in the natural VISTA Vegamag system. Photometric flags are described in Saito et al. 2012 (A&A, 537, A107)

Acknowledgments: We gratefully acknowledge use of data from the ESO Public Survey programme ID 179.B-2002 taken with the VISTA telescope, and data products from the Cambridge Astronomical Survey Unit.