Munari, U.; Henden, A.; Corradi, R. M. L.; Zwitter, T.
Bibliographical reference
CLASSICAL NOVA EXPLOSIONS: International Conference on Classical Nova Explosions. AIP Conference Proceedings, Volume 637, pp. 52-56 (2002).
Advertised on:
11
2002
Citations
21
Refereed citations
17
Description
V838 Mon has undergone one of the most mysterious stellar outbursts on
record. The spectrum at maximum closely resembled a cool AGB star,
evolving toward cooler temperatures with time, never reaching optically
thin conditions or showing increasing ionization and a nebular stage.
The latest spectral type recorded is M8-9. The amplitude peaked at
ΔV=9 mag, with the outburst evolution being characterized by a
fast rise, three maxima over four months, and a fast decay (possibly
driven by dust condensation). BaII, LiI and s-element lines were
prominent in the outburst spectra. Strong and wide (500 km/sec) P-Cyg
profiles affected low ionization species, while Balmer lines emerged to
modest emission only during the central phase of the outburst. A
light-echo discovered expanding around the object constrains its
distance to 790+/-30 pc, providing MV = +4.45 in quiescence and MV =
-4.35 at optical maximum (dependent on the still uncertain EB-V=0.5
reddening). The visible progenitor resembles a somewhat under-luminous
F0 main sequence star, that did not show detectable variability over the
last half century. V838 Mon together with M31-RedVar and V4332 Sgr seems
to define a new class of astronomical objects, Stars that Erupt into
Cool Supergiants (SECS). They do not develop optically thin or nebular
phases, and deep P-Cyg profiles denounce large mass loss at least in the
early outburst phases. Their progenitors are photometrically located
close to the Main Sequence, away from the post-AGB region. After the
outburst, the remnants still closely resemble the precursors (same
brightness, same spectral type). Many more similar objects could be
buried among poorly studied variable stars that have been classified as
Miras or SemiRegulars on the base of a single spectrum at maximum
brightness.