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VVV-WIT-05: An Extreme Transient of Unknown Nature in the VVV Survey

ATel #8869; R. K. Saito (Universidade Federal de Sergipe), D. Minniti (Univ. Andres Bello, Millennium Institute of Astrophysics, Vatican Observatory), M. Catelan (Pontificia Univ. Catolica de Chile, Millennium Institute of Astrophysics), J. C. Beamin (Univ. de Valparaiso, Millennium Institute of Astrophysics), R. Contreras Ramos (Millennium Institute of Astrophysics, Pontificia Univ. Catolica de Chile)
on 25 Mar 2016; 17:27 UT
Credential Certification: Roberto Saito (saito@ufs.br)

Subjects: Infra-Red, Neutrinos, Nova, Supernovae, Variables

Referred to by ATel #: 8873

We report the discovery of a high amplitude erupting variable, possibly a large amplitude nova or even a supernova, very close to the Galactic center. VVV-WIT-05 peaked on Aug 2011 when it appeared as a saturated source with =8.15 mag and (Z-Ks)~10 mag. The object remained in a plateau during Aug 04 - Sep 28 2011 and in the last epoch of 2011 on Oct 10 the object was seen at Ks=8.42 mag. In the 2012 season VVV-WIT-05 fades from Ks=12.24 mag on Feb 26 to Ks=12.76 mag on Apr 29.

Observations taken during 2010 as well in 2013-2015 seasons show no detection at the source position and taking into consideration the detection limit of Ks~16.6 mag in the field we can infer a total variation of Delta_Ks>8.5 mag. The amplitude is almost as large as that of VVV-WIT-01 (ATel #4041). This is another example of the occurrence of large amplitude transients in our own Galaxy that have remained hidden by dust. The coordinates of VVV-WIT-05 are RA,DEC=17:43:05.20,-28:27:39.4, corresponding to L,B=0.114,0.722.

Importantly, the VVV-WIT-05 burst coincides, both spatially and in time, with a strong neutrino event reported by the IceCube Neutrino Observatory on Aug 18 2011 in a position just about 35 arcmin apart from the coordinates of VVV-WIT-05. This coincidence suggests a possible association between VVV-WIT-05 and the neutrino detection.

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 mean extinction for a 2 arcmin region around the source position is A_K=1.1 mag, corresponding to A_V=9.3 mag.

A visual inspection on the VVV images shows the presence of two nearby sources within less than 1 arcsec from the position of VVV-WIT-05. These sources probably blend with VVV-WIT-05 when the object is in a faint stage. We encourage further observations of VVV-WIT-05 at other wavelengths.