The likely progenitor of Nova ASASSN-17nj

ATel #10857; R. K. Saito (Universidade Federal de Santa Catarina), D. Minniti (Univ. Andres Bello, Millennium Institute of Astrophysics, Vatican Observatory)
on 16 Oct 2017; 23:00 UT
Credential Certification: Roberto Saito (saito@astro.ufsc.br)

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Stanek et al. (ATel #10850) recently reported on the emergence of a likely Galactic Nova in the Milky Way disk, confirmed by near-IR spectroscopic observations (Joshi, Banerjee and Srivastava 2017, ATel #10852). Nova ASASSN-17nj is located near the Galactic center at coordinates RA, DEC (J2000) = 17:30:34.18, -31:06:06.80, corresponding to l, b = -3.576, 1.586, within the area covered by the VVV Survey (vvvsurvey.org; Minniti et al. 2010, New Astronomy, 15, 433).

Multiband near-IR VVV observations taken in 2010 show the presence of a source 0.77 arcsec apart from the reported target position. During the 2010-2012 seasons VVV Ks-band observations of the likely progenitor of Nova ASASSN-17nj shows no significant variation in brightness with mean_Ks=13.699+/-0.036, which is within the VVV photometric errors at these magnitudes. Other nearby sources found in the VVV data down to the limiting magnitude of Ks=16.9 mag in the field are 3 arcs apart from the reported target position. Taking into consideration the near-IR magnitudes obtained in UT 2017-10-15.58 (ATel #10852) the outburst presents an amplitude of Delta_Ks=8.3 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 A_K=0.47, corresponding to A_V=3.95 mag.

The VVV coordinates and magnitudes for the likely progenitor of Nova ASASSN-17nj are listed below.

  
VVV coordinates 
 
VVV ID: VVV J173034.12-310607.02 
RA, DEC(J2000) = 17:30:34.12, -31:06:07.02 
L,B = -3.576, 1.586 
 
VVV multi-band data 
 
Z  = 17.548+/-0.030 -2 
Y  = 16.427+/-0.025 -2 
J  = 15.257+/-0.022 -2 
H  = 14.140+/-0.022 -2 
Ks = 13.659+/-0.024 -2 
 
VVV Ks-band variability data 
 
MJD  Ks-mag  Ks-err  flag 
55301.37258067 13.735 0.027 -2 
55411.17924066 13.659 0.024 -2 
55769.22033243 13.725 0.026 -2 
55795.09304408 13.726 0.029 -2 
55815.04445549 13.672 0.023 -2 
55826.00325150 13.656 0.023 -1 
55844.00668243 13.660 0.024 -2 
55999.29414374 13.626 0.024 -2 
56020.23876937 13.635 0.023 -2 
56094.15932638 13.689 0.025 -2 
56101.20199736 13.680 0.024 -2 
56112.12678338 13.689 0.024 -2 
56121.24650492 13.719 0.028 -2 
56124.18451104 13.720 0.026 -2 
56125.06823743 13.764 0.031 -2 
56126.05350363 13.702 0.025 -2 
56131.18224686 13.674 0.024 -2 
56134.10318971 13.672 0.024 -2 
56135.00903390 13.717 0.025 -2 
56139.98387464 13.728 0.026 -2 
56141.01641587 13.672 0.023 -2 
56144.09435948 13.743 0.030 -1 
56160.08622026 13.642 0.023 -2 
56168.03793009 13.764 0.032 -1 
56176.03232580 13.742 0.030 -2 
56178.06595274 13.731 0.026 -2 
56178.99871600 13.693 0.025 -2 
56187.01453601 13.715 0.025 -2 
56187.06209230 13.738 0.033 -2 
56187.98781654 13.670 0.023 -2 
56189.06117375 13.704 0.026 -2 
56200.01698636 13.703 0.025 -2 

The VVV data are in the natural VISTA Vegamag system. Photometric flags are described in Saito et al. 2012 (A&A, 537, A107): -1 corresponds to a stellar object, whereas -2 to a borderline stellar source.

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. R.K.S. acknowledges support from CNPq/Brazil.