Post-outburst spectra of a stellar-merger remnant of V1309 Scorpii: from a twin of V838 Monocerotis to a clone of V4332 Sagittarii
Journal
Date Issued
2015
Author(s)
Abstract
We present optical and infrared spectroscopy of V1309 Sco, an object that
erupted in 2008 in a stellar-merger event. During the outburst, V1309 Sco
displayed characteristics typical of red transients, a class of objects similar
to V838 Mon. Our observations were obtained in 2009 and 2012, i.e. months and
years after the eruption of V1309 Sco, and illustrate severe changes in the
remnant, mainly in its circumstellar surroundings. In addition to atomic gas
observed in earlier epochs, we identified molecular bands of TiO, VO, H$_2$O,
ScO, AlO, and CrO. The infrared bands of CrO we analyse are the first
astronomical identification of the features. Over the whole period covered by
our data, the remnant was associated with a cool ($\lesssim$1000 K) outflow
with a terminal velocity of about 200 km/s. Signatures of warmer atomic gas,
likely to be still dissipating the energy of the 2008 outburst, dramatically
decreased their brightness between 2009 and 2012. In addition, the source of
optical continuum disappeared sometime before 2012, likely owing to the
formation of new dust. The final stage of V1309 Sco's evolution captured by our
spectra is an object remarkably similar to an older red transient, V4332 Sgr.
In addition to providing a detailed view on the settling of the eruptive
object, the observations presented here reinforce the conclusion that all the
Galactic red transients are a manifestation of the same phenomenon, i.e. a
stellar merger. The late spectra of V1309 Sco also suggest peculiarities in the
chemical composition of the remnant, which still need to be explored.
Volume
580
Start page
A34
Issn Identifier
0004-6361
Ads BibCode
2015A&A...580A..34K
Rights
open.access
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Post-outburst spectra of a stellar-merger remnant of V1309 Scorpii_ from a twin of V838 Monocerotis to a clone of V4332 Sagittarii.pdf
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