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HD 138557


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A magnitude limited stellar X-ray survey and the F star X-ray luminosity function
An X-ray survey has been conducted of stars brighter than visualmagnitude 8.5 that have serendipitously fallen into the fields of viewof the Imaging Proportional Counter of the Einstein Observatory. Thesurvey includes 227 separate 1 x 1 deg fields, containing 274 stars witha visual magnitude of no more than 8.5 and covering a wide range ofspectral types and luminosity classes. X-ray emission was detected from33 stars, and upper limits have been determined for the remainder of thesample. F type stars dominate the detected sample, and most of these areshown to be dwarfs. An X-ray luminosity function for dF stars has beendeduced, and reveals that the average 0.2-4.0 keV luminosity of thesestars is around 10 to the 29th erg/sec. Constraints have been placed onthe high luminosity tails and medians of the X-ray luminosity functionsfor other types of stars.

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Observation and Astrometry data

Constellation:Serpent
Right ascension:15h32m23.64s
Declination:+15°37'25.9"
Apparent magnitude:8.331
Distance:271.739 parsecs
Proper motion RA:14.2
Proper motion Dec:-19.4
B-T magnitude:9.545
V-T magnitude:8.432

Catalogs and designations:
Proper Names
HD 1989HD 138557
TYCHO-2 2000TYC 1494-1853-1
USNO-A2.0USNO-A2 1050-07537401
HIPHIP 76088

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