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The likely progenitor of Nova ASASSN-17hx (=ASASSN-17ib) detected by the VVVX Survey

ATel #10552; R. K. Saito (Universidade Federal de Santa Catarina), M. Hempel (Pontificia Universidad Catolica de Chile, Millennium Institute of Astrophysics), D. Minniti (Universidad Andres Bello, Millennium Institute of Astrophysics, Vatican Observatory)
on 2 Jul 2017; 04:05 UT
Credential Certification: Roberto Saito (saito@astro.ufsc.br)

Subjects: Infra-Red, Cataclysmic Variable, Nova

Referred to by ATel #: 10613, 10725

Stanek et al. (ATel #10523) recently reported on the rise of a likely Galactic Nova in the Milky Way disk, confirmed by spectroscopic observations (ATel #10527, #10542). Nova ASASSN-17hx is located at coordinates RA, DEC (J2000) = 18:31:45.918, -14:18:55.57, corresponding to l,b = 17.969, -2.232, within the area covered by the ESO VISTA Variables in the Via Lactea eXtended Survey (VVVX).

VVVX Ks-band observations taken during July and August 2016 show the presence of a faint source 0.84 arcsec apart from the reported target position. The likely progenitor of Nova ASASSN-17hx shows no significant variation in brightness with mean_Ks=16.71+/-0.11, which is within the VVVX photometric errors at these magnitudes. This is the only source down to the limiting magnitude of Ks=17.6 in the field and coincides within 0.65 arcs with the position of the G=19.10 mag Gaia source cited in Kurtenkov, Tomov and Pessev (ATel #10542). Also the coadded VVVX images show a source at these coordinates. Other nearby sources found in the VVVX data are 3 arcs apart from the reported target position.

According to Schlafly et al. (2011, ApJ 737, 103S) the mean extinction for the region around the source position is A_V=4.92 mag, corresponding to A_K=0.58 mag, assuming the Cardelli et al. (1989, ApJ, 345, 245)

The VVVX coordinates and Ks-band light-curve for the likely progenitor of Nova ASASSN-17hx are listed below. We note that the photometric flags indicate a stellar source in only two of the observed epochs, probably due to the contamination by an undetected blended source.

VVVX ID: VVVX J183145.86-141855.4
RA, DEC (J2000) = 18:31:45.86, -14:18:55.4
L,B = 17.97261, -2.22426

VVVX Ks-band variability data
MJD             Ks-mag       flag 
57578.11448876  16.833+/-0.170 +1 
57590.08239123  16.679+/-0.146 +1 
57591.29292707  16.742+/-0.173 +1 
57592.22676851  16.581+/-0.136 +1 
57596.09545291  16.621+/-0.141 +1 
57597.10955365  no detection              
57607.05180765  16.706+/-0.155 +1 
57607.14174894  16.953+/-0.193 -1 
57609.03246557  16.702+/-0.141 +1 
57609.05673931  16.667+/-0.133 +1 
57624.06533986  16.621+/-0.136 -1 
57625.12911430  no detection  

The VVVX data are in the natural VISTA Vegamag system. Photometric flags are similar to those found in the VVV data as described in Saito et al. 2012 (A&A, 537, A107): -1 corresponds to a stellar object, whereas +1 to a non-stellar source.

We gratefully acknowledge use of data from the ESO Public Survey programme ID 198.B-2004 taken with the VISTA telescope, and data products from the Cambridge Astronomical Survey Unit. R.K.S. acknowledges support from CNPq/Brazil.