A Bright Supernova Candidate Detected by the VVV Survey

ATel #10140; D. Minniti (Universidad Andres Bello, The Milky Way Millennium Nucleus, Center for Astrophysics and Associated Technologies, Vatican Observatory), R. K. Saito (Universidade Federal de Santa Catarina)
on 3 Mar 2017; 01:27 UT
Credential Certification: Roberto Saito (saito@astro.ufsc.br)

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We report the discovery of a large-amplitude near-IR transient event observed by the VVV Survey (vvvsurvey.org; Minniti et al. 2010, New Astronomy, 15, 433). The light curve has a clear eruption peaking in July 2013, reaching Ks~9 mag. Previous ZYJHKs observations taken in 2010, and Ks-band observations taken during during the 2010, 2011, and 2012 seasons show no detection of the progenitor at the source position. Taking into consideration that the detection limit in the field is of Ks~18.5 mag we can infer a total amplitude of Delta_Ks>9.5 mag. There is a nearby saturated star (~90 arcsec away to the West), but it does not seem to be responsible for producing the observed variation in brightness.

We derived an accurate position of this object using the VVV Ks-band images. The Equatorial coordinates are RA=17h07m18.917s, DEC=-39d06m26.45s (J2000), corresponding to Galactic coordinates l=347.14539, b=+0.88522. The approximate colours are (J-Ks)=2.146, (H-Ks)=0.952, (J-H)=1.194, measured at the decline phase in 27 July 2015. The object is located in a very reddened field, and we estimate a total extinction of A_V=10-15 mag depending on the shape of the reddening law.

The large amplitude, and the light curve shape and decline slope are consistent with a supernova. The amplitude is larger than those of VVV-WIT-01 (ATel #4041), and VVV-WIT-05 (ATel #8869). However, there are no published neutrino detections in the area at that time. Our search for earlier data of this object shows that it had no observable counterpart (within a distance of 5") in previous images from 2MASS, GLIMPSE, Spitzer, WISE, nor MSX. We encourage further observations of this object at other wavelengths.

The tables below report the Cambridge Astronomical Survey Unit (CASU) photometry for this object.

 
Ks-band observations: 
 
HJD mag merr flag 
55285.39108101 beyond detection   
55374.18025550 beyond detection 
55692.31379194 beyond detection 
55695.32765782 beyond detection 
55697.37805366 beyond detection 
55711.32512609 beyond detection 
55795.07494736 beyond detection 
55810.07695970 beyond detection 
55840.00604085 beyond detection 
56105.05465843 beyond detection 
56111.03293386 beyond detection 
56112.00600012 beyond detection 
56113.96733594 beyond detection 
56115.05587517 beyond detection 
56473.09881128 10.001 0.01  -9  
56474.04973095  9.604 0.01  -9  
56475.19182240  9.693 0.01  -9  
56484.11403293  9.300 0.01  -9  
56496.04942542  9.096 0.01  -9  
56497.13131776  9.196 0.01  -9  
56498.06406656  9.359 0.01  -9  
56498.09551678  9.499 0.01  -9  
56508.98402608 10.825 0.01  -9  
56509.10667710 10.897 0.01  -9  
56509.17817734 10.834 0.01  -9  
56510.03239554 10.862 0.01  -1  
56510.16380074 10.803 0.01  -9  
56511.05712890 10.814 0.01  -9  
56521.98026580 11.528 0.01  -9  
56522.05744970 11.544 0.01  -9  
56522.99287532 11.560 0.01  -1  
56525.03867764 11.601 0.01  -1  
56526.07011642 11.535 0.01  -1  
56534.98473180 11.516 0.01  -1  
56535.05776775 11.507 0.01  -9  
56535.99602704 11.540 0.01  -1 
56837.98565643 14.894 0.036 -1 
56850.02943426 14.938 0.041 -1 
56850.15113615 14.895 0.031 -1 
56878.03521206 15.100 0.043 -1 
56887.99337296 15.102 0.042 -1 
56888.00700966 15.142 0.045 -1 
56888.02052799 15.179 0.045 -1 
56888.04609087 15.096 0.040 -1 
57113.22871432 16.071 0.094 -1 
57162.21248616 16.251 0.123 -1 
57228.09581258 16.301 0.122 -1 
57228.10790160 16.257 0.120 -1 
57228.11917881 16.495 0.153 -1 
57231.10604126 16.165 0.079 -1 
 
Multicolour observations: 
 
Filter Date HJD mag merr flag 
Z  20150422 57135.37095248 beyond detection 
Y  20150422 57135.36738701 19.633 0.188 -1 
J  20150727 57231.11120670 18.311 0.111 -1 
H  20150727 57231.10081079 17.117 0.083 -1 
Ks 20150727 57231.10604126 16.165 0.079 -1 

Photometric flags are described in Saito et al. 2012 (A&A, 537, A107): -1 corresponds to a stellar object, whereas -9 to a saturated source.