Issue |
A&A
Volume 374, Number 1, July IV 2001
|
|
---|---|---|
Page(s) | 105 - 115 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20010665 | |
Published online | 15 July 2001 |
The problem of the Pleiades distance
Constraints from Strömgren photometry of nearby field stars
Institute of Physics and Astronomy (IFA), University of Aarhus, 8000 Aarhus, Denmark e-mail: pen@ifa.au.dk
Corresponding author: D. Stello, stello@ifa.au.dk
Received:
3
April
2001
Accepted:
7
May
2001
The discrepancy between the Pleiades cluster distance based on
Hipparcos parallaxes and main sequence fitting is investigated on the
basis of Strömgren photometry of F-type stars. Field stars with the
same metallicity as the Pleiades have been selected from the m1
index and a technique has been developed to locate the ZAMS of
these field stars in color-magnitude diagrams based on the
color/temperature indices
,
, and β. Fitting the Pleiades to these ZAMS
relations results in a distance modulus of
mag in contrast to
the Hipparcos modulus of
mag. Hence, we cannot confirm the
recent claim by Grenon ([CITE]) that the distance problem
is solved by adopting a low metallicity of the Pleiades
(
) as determined from Geneva photometry.
The metallicity sensitivity of the ZAMS determined by the field stars is
investigated, and by combining this sensitivity in all three
color/temperature indices
,
, and β we get a
independent test of the Pleiades
distance modulus which support our value of 5.61 mag.
Furthermore, the field star sample used for the comparison is tested
against theoretical isochrones of different ages to show that
evolutionary effects in the field star sample are not biasing
our distance modulus estimate significantly.
Possible explanations of the Pleiades distance problem are discussed
and it is suggested that the discrepancy in the derived moduli may be
linked to a non-spherical shape of the cluster.
Key words: open clusters and associations: individual: Pleiades / stars: Hertzsprung-Russell (HR) and C / M diagrams / stars: distances / stars: evolution / stars: abundances
© ESO, 2001
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