Examinando por Autor "Smith, L."

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    The Emergence of the Infrared Transient VVV-WIT-06
    (Institute of Physics Publishing, 2017-11) Minniti, D.; Saito, R.K.; Forster, F.; Pignata, G.; Ivanov, V.D.; Lucas, P.W.; Beamin, J.C.; Borissova, J.; Catelan, M.; Gonzalez, O.A.; Hempel, M.; Hsiao, E.; Kurtev, R.; Majaess, D.; Masetti, N.; Morrell, N.I.; Phillips, M.M.; Pullen, J.B.; Rejkuba, M.; Smith, L.; Surot, F.; Valenti, E.; Zoccali, M.
    We report the discovery of an enigmatic large-amplitude (ΔKs >10.5 mag) transient event in near-IR data obtained by the VISTA Variables in the Via Lactea (VVV) ESO Public Survey. The object (designated VVV-WIT- 06) is located at R.A.=17:07:18.917, decl.=-39:06:26.45 (J2000), corresponding to Galactic coordinates l=347.14539, b=0.88522. It exhibits a clear eruption, peaking at Ks=9 mag during 2013 July and fading to Ks ∼ 16.5 in 2017. Our late near-IR spectra show post-outburst emission lines, including some broad emission lines (upward of FWHM ∼ 3000 km s-1). We estimate a total extinction of AV = 10-15 mag in the surrounding field, and no progenitor was observed in ZYJHKs images obtained during 2010-2012 (down to Ks > 18.5mag). Subsequent deep near-IR imaging and spectroscopy, in concert with the available multiband photometry, indicate that VVV-WIT-06 may be either: (i) the closest Type I SN observed in about 400 years, (ii) an exotic highamplitude nova that would extend the known realm of such objects, or (iii) a stellar merger. In all of these cases, VVV-WIT-06 is a fascinating and curious astrophysical target under any of the scenarios considered.
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    VVV-WIT-01: Highly obscured classical nova or protostellar collision?
    (Royal Astronomical Society [Associate Organisation] Oxford University Press [Commercial Publisher], 2020-01) Lucas, P.; Minniti, D.; Kamble, A.; Kaplan, D.; Cross, N.; Dekany, I.; Ivanov, V.; Kurtev, R.; Saito, R.; Smith, L.; Catelan, M.; Masetti, N.
    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 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 ≈ 0.01-0.02), 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.