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VVV-NOV-001: the first Galactic nova candidate discovered by the VVV Survey in the Milky Way bulge

ATel #4426; R. K. Saito (Pontificia Universidad Catolica de Chile, Universidad de Valparaiso, The Milky Way Millennium Nucleus), D. Minniti (Pontificia Universidad Catolica de Chile, Vatican Observatory, The Milky Way Millennium Nucleus), R. Angeloni (Pontificia Universidad Catolica de Chile, The Milky Way Millennium Nucleus) and M. Catelan (Pontificia Universidad Catolica de Chile, The Milky Way Millennium Nucleus)
on 26 Sep 2012; 16:37 UT
Distributed as an Instant Email Notice Novae
Credential Certification: Roberto Saito (rsaito@astro.puc.cl)

Subjects: Infra-Red, Nova, Transient

Referred to by ATel #: 7124

We report the discovery of a likely Galactic nova in the VVV Survey data (vvvsurvey.org; Minniti et al. 2010, New Astronomy, 15, 433). VVV observations taken during 2010 and 2011 show the presence of a red stellar source fading in brightness from July 1st 2010 to May 29 2012 (see table below). The fading of the light curve follows the expected behavior of the late stages of a nova outburst, with VVV-NOV-001 fading by Delta_Ks>2.5 over 698 days, with a roughly constant fading rate.

The coordinates of VVV-NOV-001 are RA, DEC= 18:06:03.18, -21:19:47.31 (J2000), corresponding to (l,b)=8.897,-0.158 deg. Quasi simultaneous VVV JHKs observations taken on July 1st 2010 show VVV-NOV-001 with (J-Ks)=8.06 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)=2.45 mag, which corresponds to AV=10.97 mag.

2MASS data show a stellar source in the same position of VVV-NOV-001 that can be the candidate nova progenitor. The source is detected in the K-band only, with K=12.08 mag. In the other two 2MASS bands the object is flagged as "U" (upper limit on magnitude, see table below).

We recommend further observations in order to discard the hypothesis of a rare Long Period Variable or OH/IR star with P>700 days and Delta_Ks>2.5mag.

VVV-NOV-001 Observations: 
Date  (UT)      filter      mag 
2010-07-01.2564   H   13.057+/-0.010 
2010-07-01.2594   Ks   9.951+/-0.010 
2010-07-01.2624   J   18.008+/-0.140 
Date  (UT)      filter      mag 
2010-10-25.0056   Ks  10.329+/-0.010 
2011-08-05.2277   Ks  11.425+/-0.010 
2011-09-24.0377   Ks  11.641+/-0.010 
2011-09-26.0465   Ks  11.606+/-0.010 
2012-03-04.3779   Ks  12.306+/-0.010 
2012-03-07.3688   Ks  12.313+/-0.010 
2012-03-09.3475   Ks  12.304+/-0.010 
2012-03-10.3607   Ks  12.320+/-0.010 
2012-03-27.3614   Ks  12.333+/-0.010 
2012-03-28.3163   Ks  12.365+/-0.010 
2012-04-03.3479   Ks  12.361+/-0.010 
2012-05-07.3701   Ks  12.400+/-0.010 
2012-05-17.3756   Ks  12.427+/-0.010 
2012-05-28.3162   Ks  12.459+/-0.010 
2012-05-29.3413   Ks  12.476+/-0.010 
The VVV data are in the natural VISTA Vegamag system.
2MASS data (possible VVV-NOV-001 progenitor) 
filter    mag         Qflag 
J       16.030          U^ 
H       14.593          U^ 
K       12.078+/-0.019  A 
^U = upper limit on magnitude 
Acknowledgements: 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.