Bibcode
Garcia-Lario, P.; Parthasarathy, M.; de Martino, D.; Sanz Fernandez de Cordoba, L.; Monier, R.; Manchado, A.; Pottasch, S. R.
Bibliographical reference
Astronomy and Astrophysics, v.326, p.1103-1110
Advertised on:
10
1997
Journal
Citations
29
Refereed citations
22
Description
We present the results from a multiwavelength analysis of LS II+34 26,
recently identified as a low mass post-AGB star and not a massive
population I B-type star, as previously thought. We confirm that the
central star is a carbon-poor post-AGB star surrounded by a very low
excitation and compact nebula. Spectroscopic monitoring carried out
since 1991 reveals variations which suggest that this star has had a
mass loss episode in the period 1993-1995. The asymmetric profiles in a
few absorption lines in high resolution optical spectra indicate the
presence of complex motions in the outer layers of the atmosphere. The
radial velocity variations (several tens of km/s) observed in spectra
taken in a single epoch can be attributed to stellar pulsation. For a
few lines stronger variations over the years (up to 70km/s) can be
explained if these lines are formed in the outflow. The anomalous
extinction observed in the UV suggests that part of the reddening is of
circumstellar origin and that the standard interstellar extinction law
is not applicable. On the other hand, the absence of a significant near
infrared excess in LS II+34 26 suggests that the mass loss enhancement
corresponds to a short-lived episode of modest intensity. Although
non-LTE effects prevent the accurate determination of the atmospheric
parameters and abundances of LS II+34 26, a comparative analysis with LS
IV-12 111 indicates that both stars are very similar. Both are
identified as low mass carbon-poor hot post-AGB stars belonging to the
halo population of our Galaxy.