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Astron. Astrophys. 348, 161-169 (1999)


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X-ray emission from A0-F6 spectral type stars

M.R. Panzera 1, G. Tagliaferri 1, L. Pasinetti 2 and E. Antonello 1

1 Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (LC), Italy
2 Dipartimento di Fisica, Universita degli Studi di Milano, Via Celoria 16, I-20133 Milano, Italy

Received 7 August 1998 / Accepted 9 June 1999

Abstract

We use the ROSAT public data archive to study the X-ray emission of a sample of supposedly single A0-F6 spectral type stars from the Bright Star Catalogue. We detected X-ray emission from 19 A- and 33 F-type stars. However, our results are not sufficient to associate with certainty the X-ray emission to the A-type stars themselves, since the usual argument that it may originate from a binary companion cannot be excluded. A spectral analysis was conducted for 14 sources (3 A and 11 F), finding that for 12 of them a two temperature thermal plasma model is needed to reproduce the observed spectra. The two temperatures are centered at 0.13 and 0.54 keV, respectively. The values found for the higher temperature are lower than that ones of X-ray selected single late-type stars. The X-ray luminosities are in the range [FORMULA] erg s-1, with a distribution similar to that of active late-type stars. No correlation is found between [FORMULA] and B-V color, [FORMULA] and [FORMULA], while a positive correlation is found between the X-ray luminosity and the hardness ratio.

Key words: X-rays: stars – stars: coronae – stars: chromospheres – stars: activity – stars: binaries: general

Send offprint requests to: M.R. Panzera (panzera@merate.mi.astro.it)

© European Southern Observatory (ESO) 1999

Online publication: July 16, 1999

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