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ROSAT Observations of the Pleiades. I. X-Ray Characteristics of a Coeval Stellar Population

1996; Institute of Physics; Volume: 102; Linguagem: Inglês

10.1086/192252

1538-4365

G. Micela, S. Sciortino, V. Kashyap, Jr. Harnden F. R., R. Rosner,

Astro and Planetary Science

view Abstract Citations (116) References (84) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS ROSAT Observations of the Pleiades. I. X-Ray Characteristics of a Coeval Stellar Population Micela, G. ; Sciortino, S. ; Kashyap, V. ; Harnden, F. R., Jr. ; Rosner, R. Abstract We report the results of a deep X-ray survey of the core region of the Pleiades carried out with ROSA T. In a single PSPC field (∼1° radius), we detect 99 of 214 Pleiades stars, and we compute upper limits for the remainder. We have detected all early dM stars that fell within 20' of the field's center, where the instrument's sensitivity is highest. We have computed maximum-likelihood integral X-ray luminosity functions in various B - V intervals and compared the results with previous studies of the Pleiades. Our results support the contention that B and dA star "detections" are likely due to X-ray emission from lower mass companions; we confirm the existence of a stellar age versus X-ray luminosity relation found with the Einstein Observatory for dG stars and extend it to dK and dM stars, and we construct an essentially statistically complete X-ray luminosity function for Pleiades dG stars and an almost complete X-ray luminosity function for dK stars. We have verified the stellar rotation versus X-ray luminosity relation for Pleiades dG stars and also show that a similar relation does not hold for dK stars. Indeed, it appears that some stellar parameters other than age and/or rotation rate must affect the level of X-ray emission of Pleiades dG and dK stars. We demonstrate the lack of measurable variability in X-ray emission at timescales of ∼6 months (except for flares) and the presence of variability by a factor of 2 on timescales of ∼10 yr in at least 15% of Pleiades members. The magnitude of this variability (by a factor of ∼2) is too small to account for the spread of the X-ray luminosity functions. Publication: The Astrophysical Journal Supplement Series Pub Date: January 1996 DOI: 10.1086/192252 Bibcode: 1996ApJS..102...75M Keywords: GALAXY: OPEN CLUSTERS AND ASSOCIATIONS: INDIVIDUAL NAME: PLEIADES; STARS: LATE-TYPE; STARS: ROTATION; SURVEYS; X-RAYS: STARS full text sources ADS | data products SIMBAD (238) CDS (2) HEASARC (1) Related Materials (1) Catalog: 1998yCat..21020075M