Issue |
A&A
Volume 434, Number 3, May II 2005
|
|
---|---|---|
Page(s) | 1107 - 1116 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20041751 | |
Published online | 18 April 2005 |
On the distance, reddening and progenitor of V838 Mon
1
INAF – Osservatorio Astronomico di Padova, Sede di Asiago, 36012 Asiago (VI), Italy e-mail: munari@pd.astro.it
2
Univ. Space Research Assoc./US Naval Observatory, PO Box 1149, Flagstaff AZ 86002-1149, USA
3
INAF – Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 8, 35122 Padova, Italy
4
Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 USA
5
Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de La Palma, Canarias, Spain
6
South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
7
Dept. of Physics and Astronomy, Arizona State Univ., PO Box 871504 Tempe, AZ 85287-1504, USA
8
Centre for Astronomy, Nicolaus Copernicus University, ul. Gagarina 11, 87-100 Torun, Poland
9
Dipartimento di Astronomia, Universitá di Padova, 35122 Padova, Italy
10
University of Ljubljana, Department of Physics, Jadranska 19, 1000 Ljubljana, Slovenia
11
Large Binocular Telescope Observatory, Univ. of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
Received:
29
July
2004
Accepted:
19
January
2005
Extensive optical and infrared photometry as well as
low and high resolution spectroscopy are used as inputs in deriving robust
estimates of the reddening, distance and nature of the progenitor of
V838 Mon, the 2002 outbursting event that produced a most spectacular
light-echo. The reddening affecting V838 Mon is found to obey
the RV=3.1 law and amounts to (i) from the interstellar NaI and KI lines; (ii)
from the energy distribution of the B3 V component; and (iii)
from the progression of extinction along the
line of sight. The adopted
is also the amount
required by fitting the progenitor with theoretical isochrones of
appropriate metallicity. The distance is estimated from (a) the galactic
kinematics of the three components of the interstellar lines; (b) the
amount of extinction vs. the HI column density and vs. the dust emission
through the whole Galaxy in that direction; from (c) spectrophotometric
parallax to the B3 V companion; from (d) comparison of the observed
color-magnitude diagram of field stars with 3D stellar population models of
the Galaxy; from (e) comparison of theoretical isochrones with the
components of the binary system in quiescence and found to be around 10 kpc.
Pre-outburst optical and IR energy distributions show that the component
erupting in 2002 was brighter and hotter than the B3 V companion. The best
fit is obtained for a 50 000 K source, 0.5 mag brighter than the B3 V companion. The latter passed unaffected through the outburst, which implies
an orbital separation wide enough to avoid mass exchange during the
evolution of the binary system, and to allow a safe comparison with
theoretical isochrones for single stars. Such a comparison suggests that the
progenitor of the outbursting component had an initial mass ~65
, that it was approaching the carbon ignition stage in its
core at the time it erupted in 2002 and that the age of the V838 Mon binary
system is close to 4 million yr. The 2002 event is probably just a shell
thermonuclear event in the outer envelope of the star.
Key words: stars: evolution / stars: early-type / stars: individual: V838 Mon / stars: winds, outflows / ISM: lines and bands / stars: peculiar
© ESO, 2005
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