A search of the first Data Release of the VISTA Variables in the Via Lactea (VVV) Survey discovered the exceptionally red transient VVV-WIT-01 (H−Ks=5.2). It peaked before March 2010, then faded by ∼9.5 mag over the following two years. The 1.6--22 μm spectral energy distribution in March 2010 was well fit by a highly obscured black body with T∼1000 K and AKs∼6.6 mag. The source is projected against the Infrared Dark Cloud (IRDC) SDC G331.062−0.294. The chance projection probability is small for any single event (p≈0.01 to 0.02) which suggests a physical association, e.g. a collision between low mass protostars. However, black body emission at T∼1000 K is common in classical novae (especially CO novae) at the infrared peak in the light curve, due to condensation of dust ∼30--60 days after the explosion. Radio follow up with the Australia Telescope Compact Array (ATCA) detected a fading continuum source with properties consistent with a classical nova but probably inconsistent with colliding protostars. Considering all VVV transients that could have been projected against a catalogued IRDC raises the probability of a chance association to p=0.13 to 0.24. After weighing several options, it appears likely that VVV-WIT-01 was a classical nova event located behind an IRDC.
@article{arxiv.2001.05536,
title = {VVV-WIT-01: highly obscured classical nova or protostellar collision?},
author = {P. W. Lucas and D. Minniti and A. Kamble and D. L. Kaplan and N. Cross and I. Dekany and V. D. Ivanov and R. Kurtev and R. K. Saito and L. C. Smith and M. Catelan and N. Masetti and I. Toledo and M. Hempel and M. A. Thompson and C. Contreras Peña and J. Forbrich and M. Krause and J. Dale and J. Borissova and J. Emerson},
journal= {arXiv preprint arXiv:2001.05536},
year = {2020}
}