VVV-WIT-01: highly obscured classical nova or protostellar collision?

• Published in: Monthly notices of the Royal Astronomical Society Vol. 492; no. 4; pp. 4847 - 4857
• Main Authors: Lucas, P W, Minniti, D, Kamble, A, Kaplan, D L, Cross, N, Dekany, I, Ivanov, V D, Kurtev, R, Saito, R K, Smith, L C, Catelan, M, Masetti, N, Toledo, I, Hempel, M, Thompson, M A, Contreras Peña, C, Forbrich, J, Krause, M, Dale, J, Borissova, J, Emerson, J
• Format: Journal Article
• Language: English
• Published: Oxford University Press 11.03.2020
• Subjects: stars: formation; ISM: clouds; infrared: stars; novae, cataclysmic variables
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/staa155

ABSTRACT 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 2 yr. The 1.6–22 μm spectral energy distribution in March 2010 was well fit by a highly obscured blackbody with T ∼ 1000 K and $A_{K_s} \sim 6.6$ 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 ≈ 0.01–0.02), which suggests a physical association, e.g. a collision between low mass protostars. However, blackbody 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 d after the explosion. Radio follow-up with the Australia Telescope Compact Array 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 = 0.13–0.24. After weighing several options, it appears likely that VVV-WIT-01 was a classical nova event located behind an IRDC.