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Searching for old neutron stars with ROSAT. II. Soft X-ray sources in galactic dark clouds
This is the second in a series of three papers constraining the numberof detectable old neutron stars in the Galaxy. Here, I present thestatistical analysis of a sample of X-ray sources coincident with areasof dark clouds in the Galactic plane. I compare this sample with allsources in the ROSAT All-Sky Survey bright source catalog within 20(deg)of the Galactic plane. I present the results of an identificationprogram of a subset of sources that are compatible with a soft, thermalX-ray spectrum and an effective source temperature of less than 70eV.The three brightest sources in this sample form an intriguing subgroup.One of them is a previously identified candidate for an accretingneutron star. I identify the other two sources with hot white dwarfstars. I find no new accreting neutron star candidate in this sample.Based on this result, I derive an upper limit to the space density ofaccreting neutron stars in fields of Galactic dark clouds of ~ 2sr(-1)at a count rate >0.05s(-1) .
| Hyades and Sirius supercluster members brighter than magnitude (V) 7.1. II - Right ascension six to twelve hours
The present star sample is contained in the Bright Star Catalogue andits Supplement, augmented with a further supplement of 788 stars foundduring various observing programs over the past 40 years. Accurate,four-color and H-beta, or (RI), photometry is available for most of thesupercluster members. The criteria for membership are the comparisons ofthe proper motion, radial velocity, and luminosity obtained from thesupercluster parameters with the observed motions and the luminosityderived from the photometric parameters. New proper motions, based onall available catalogs, have been derived for the additional 788 starsdiscussed here, as well as all supercluster members.
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