SCYON Abstract

Received on September 30 2004

XMM-Newton observation of the young open cluster Blanco 1. II. X-ray variability and flares

Authors	I. Pillitteri (^1,2), G. Micela (²), F. Reale (¹), S. Sciortino (²)
Affiliation	¹ Università degli Studi di Palermo ² INAF- Oss. Astronomico di Palermo
Accepted by	Astronomy & Astrophysics
Contact	pilli@astropa.unipa.it
URL	www.astropa.unipa.it/Library/preprint.html
Links	Blanco 1

Abstract

We study the X-ray variability of the young open cluster Blanco 1 observed with th eEPIC camera on board of XMM-Newton X-ray observatory. The time coverage of EPIC observations has allowed us to address the short time scale (hours) variability, while the comparison with previous ROSAT observations has allowed us to investigate the variability on the time scale of six years. On the time scale of hours, dM stars of the cluster are more variable than solar-mass stars. The main feature of X-ray light curves in dM stars appear to be essentially flare-like events with typical duration of the order of a few ks, while dF-dG stars show smooth variations. Two intense flares were observed in the ZS76 cluster member. From the analysis of the light curves and of the time resolved X-ray spectroscopy we infer that hey occured in arcades. made of several similar coronal loops (~10¹⁰cm long), ignited at ~15 ks time delay. Minor heat pulses may occur in the firts flare. The similarity of the two flares and of the flaring inferred structures may suggest that the flares are physically connected to each other. Amplitude variations on the time scale of 6 years are smaller than a factor 2, whereas a factor 10 is observed on the Sun in the same band. This implies a smaller amplitude of any analog of the 11-yr cycle on these young active coronae.