Astron. Astrophys. 355, 681-687 (2000)

The active binary star II Pegasi with Beppo SAX

S. Covino ¹, G. Tagliaferri ¹, R. Pallavicini ², R. Mewe ³ and E. Poretti <sup>1

1</sup> Brera Astronomical Observatory, Via Bianchi 46, 23807 Merate, Italy
² Palermo Astronomical Observatory, P.za del Parlamento 1, 90134 Palermo, Italy
³ SRON Laboratory for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

Received 28 May 1999 / Accepted 10 November 1999

Abstract

II Peg is an ideal target to study stellar activity and flares, since intense and long lasting flares have been frequently detected from this system at all wavelengths. We report here about a Beppo SAX observation of II Peg. We followed the system for hours on December 5 and 6 1997 with Beppo SAX and the X-ray light curve resembles the typical behavior of a decay phase of a long-lasting flare. The spectral analysis shows that the II Peg X-ray spectrum is described by a two-temperature components, with the two dominant temperatures centered in the range of 9-11 and 24-26 MK. The derived coronal metal abundance is low () compared to recent determinations of the photospheric abundance (). Some possible explanations for this phenomenology are reviewed. As for most other stellar coronal sources observed with Beppo SAX, we find that in order to fit the Beppo SAX spectra an interstellar column density about a factor ten higher than previously determined is required.

Key words: stars: activity stars: coronae stars: flare stars: individual: II Peg X-rays: stars

Send offprint requests to: S. Covino

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Contents

• 1. Introduction
• 2. The data
• 3. Results
• 4. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: March 9, 2000
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