POSTER PAPER 4.01
Chandra Observations of the Pleiades Open Cluster: X-ray emission from
late-B and A type Pleiades members
Kathryne J. Daniel, Jeffrey L. Linsky, Marc Gagne
Institute: JILA, University of Colorado
Institute: Dept. of Geology & Astronomy, West Chester University
Contact Email: kdaniel@pha.jhu.edu
Abstract:
We present the analysis of 38.4 ks and 23.6 ks ACIS-I observations of the core
of the Pleiades open cluster. Of the 101 sources detected in the
17'x17' region, 53 have not been cataloged at any other
wavelength. Eighteen of 23 Pleiades members in the ACIS-I FOV
were detected as X-ray sources with moderate to high time variability.
Two of the early-type Pleiades members, HII 980 (B6 IV) and HII 956 (A7 V), are
very bright X-ray sources, show soft X-ray spectra, and are variable with no
obvious signs of flaring. K- and M-type cluster members with comparable X-ray
luminosities have hard X-ray spectra and display strong flares. For
non-flaring K- and M-type stars, Lx is 1--2 orders of magnitude lower.
One A-type star, HII 1284 (A9 V), has X-ray properties comparable to these
non-flaring K-type stars. One star, HII 1338 (F3 V), exhibits an X-ray flare
and two others, HII 1362 (A7 V) and HII 1375 (A0 V) are not detected. Despite
the low number statistics, this pattern among late-B to early-F stars suggests
that some early-type stars like HII 980 and HII 956 are intrinsic X-ray
emitters. Some, like HII 1284 and HII 1338, may have late-type companions and
some, like HII 1362 and HII 1375, may be single, inactive stars. X-ray spectra
and light curves of a larger sample of intermediate-mass stars are needed to
confirm this trend.
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Manuscript submitted: 2001-Sep-10
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.