Issue |
A&A
Volume 368, Number 3, March IV 2001
|
|
---|---|---|
Page(s) | 873 - 879 | |
Section | Galactic structure, stellar clusters, and populations | |
DOI | https://doi.org/10.1051/0004-6361:20010069 | |
Published online | 15 March 2001 |
Internal kinematics and binarity of X-ray stars in the Pleiades open cluster
1
Copenhagen University Observatory, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
2
DASGAL, Observatoire de Paris-Meudon, bât. 11, 5 place Jansen, 92195 Meudon Cedex, France
Corresponding author: V. V. Makarov, makarov@astro.ku.dk
Received:
27
November
2000
Accepted:
10
January
2001
The classical convergent point analysis is implemented for the Pleiades stars
with proper motions in the Tycho-2 Catalogue and X-ray fluxes measured
by the ROSAT satellite. It is demonstrated that, with
the standard astrometric errors as given in Tycho-2, strong X-ray
sources in the cluster (, where LX is in erg s-1)
exhibit a velocity dispersion in
one component of only 0.20 km s-1,
while the distributions of velocity components of moderate (
)
sources and stars not detected by ROSAT at all are consistent with
a velocity dispersion of 0.64 km s-1. The difference is statistically
significant at the level of
, or 0.95 confidence limit.
This result is a clue to the
kinematics/X-ray luminosity segregation, similar to that previously
discovered in the Hyades open cluster. It is discussed that the
segregation may be caused by a wide spread of
ages of the member stars. The occurrence of high X-ray luminosities is
found to correlate very well with visual binarity and multiplicity (separations
AU).
Key words: open clusters and associations: individual: Pleiades / stars: kinematics / astrometry
© ESO, 2001
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