Issue |
Astron. Astrophys. Suppl. Ser.
Volume 140, Number 1, November II 1999
|
|
---|---|---|
Page(s) | 55 - 67 | |
DOI | https://doi.org/10.1051/aas:1999518 | |
Published online | 15 November 1999 |
Period–Luminosity–Colour distribution and classification of Galactic oxygen–rich LPVs*,**
I. Luminosity calibrations
1
Departament d'Astronomia i Meteorologia, Universitat de Barcelona, Avda. Diagonal 647, E–08028 Barcelona, Spain
2
Institut d'Astrophysique, CP 226, Université Libre de Bruxelles, Bd. du Triomphe, B–1050 Bruxelles, Belgium
3
GRAAL (UPRES-A 5024 CNRS), Université Montpellier II, F–34095 Montpellier Cedex 05, France
Received:
24
February
1999
Accepted:
6
September
1999
The absolute K magnitudes and kinematic parameters of about 350
oxygen–rich Long–Period Variable stars are calibrated, by means of an
up–to–date maxi mum–likelihood method, using Hipparcos parallaxes
and proper motions together with radial velocities and, as additional
data, periods and colour indices. Four groups, differing by
their kinematics and mean magnitudes, are found. For each of them, we also
obtain the distributions of magnitude, period and de-reddened colour of the
base population, as well as de-biased period–lumi nosity–colour relations
and their two–dimensional projections. The SRa semiregulars do not seem to
constitute a separate class of LPVs.
The SRb appear to belong to two populations of different ages. In a PL
diagram, they constitute two evolutionary sequences towards the Mira
stage. The Miras of the disk appear to pulsate on a lower–order mode. The
slopes of their de-biased PL and PC relations are found to be very different
from the ones of the Oxygen Miras of the LMC. This suggests that a significant
number of so–called Miras of the LMC are misclassified. This also suggests
that the Miras of the LMC do not constitute a homogeneous group, but include
a significant proportion of metal–deficient stars, suggesting a relatively
smooth star formation history. As a consequence, one may not trivially
transpose the LMC period–luminosity relation from one galaxy to the
other.
Key words: stars: variables: long period variables / AGB / fundamental parameters / kinematics / evolution
© European Southern Observatory (ESO), 1999