  We present the analysis of a 38.4 ks and a 23.6 ks observation of the core of
the Pleiades open cluster. The Advanced CCD Imaging Spectrometer on board the
Chandra X-ray Observatory detected 99 X-ray sources in a 17'X17' region,
including 18 of 23 Pleiades members. Five candidate Pleiades members have also
been detected, confirming their cluster membership. Fifty-seven sources have no
optical or near-infrared counterparts to limiting magnitudes V=22.5 and J=14.5.
The unidentified X-ray sources are probably background AGN and not stars. The
Chandra field of view contains seven intermediate mass cluster members. Five of
these, HII 980 (B6 + G), HII 956 (A7 + F6), HII 1284 (A9 + K), HII 1338 (F3 +
F6), and HII 1122 (F4 + K), are detected in this study. All but HII 1284 have
high X-ray luminosity and soft X-ray spectra. HII 1284 has X-ray properties
comparable to non-flaring K-type stars. Since all five stars are visual or
spectroscopic binaries with X-ray properties similar to F-G stars, the
late-type binary companions are probably producing the observed coronal X-ray
emission. Strengthening this conclusion is the nondetection by Chandra of two A
stars, HII 1362 (A7, no known companion) and HII 1375 (A0 + A SB) with X-ray
luminosity upper limits 27-54 times smaller than HII 980 and HII 956, the B6-A7
stars with cooler companions. Despite the low number statistics, the Chandra
data appear to confirm the expectation that late-B and A stars are not strong
intrinsic X-ray sources. The ACIS spectra and hardness ratios suggest a gradual
increase in coronal temperature with decreasing mass from F4 to K. M stars
appear to have somewhat cooler coronae than active K stars.
