Bibcode
Hünsch, M.; Randich, S.; Weidner, C.; Hempel, M.; Schmitt, J. H. M. M.
Bibliographical reference
Stars as suns : activity, evolution and planets, Proceedings of the 219th symposium of the International Astronomical Union held during the IAU General Assembly XXV, Sydney, Australia, 21-25 July 2003. Edited by A.K. Dupree and A.O. Benz. San Francisco, CA: Astronomical Society of the Pacific (ASP), 2004. Available on companion CD-ROM., p.980
Advertised on:
1
2004
Citations
1
Refereed citations
1
Description
We have conducted a detailed study of the open clusters NGC 2451 A and B
which are located along the same line of sight at 206pc and 370pc
distance respectively. Although belonging to the nearest clusters they
have not been much investigated until present due to strong
contamination by field stars. ROSAT X-ray observations and optical UBVR
photometry are used to identify cluster members by means of X-ray
emission and colour-magnitude diagrams. For the first time the range of
known probable cluster members has been extended to main sequence stars
of spectral class M. Isochrone fitting yields an age of 50 to 80 Myrs
for NGC 2451 A and about 50 Myrs for NGC 2451 B consistent with the
X-ray luminosity distribution functions. Except from the occurence of
four flares the stars of both clusters do not show strong long-term
X-ray variability exceeding a factor 5 over a time span of 1 to 3 years.
High-resolution spectra obtained with FEROS confirmed membershipof most
of the X-ray selected cluster member candidates by means of radial
velocity and allowed to obtain rotational velocities as well as
metallicities and lithium abundances.