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Astron. Astrophys. 344, 83-96 (1999)

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X-ray observations of the young open cluster Blanco 1

G. Micela 1, S. Sciortino 1, F. Favata 2, R. Pallavicini 1 and J. Pye 3

1 Osservatorio Astronomico di Palermo, Palazzo dei Normanni, I-90134 Palermo, Italy (gmicela; ssciortino; pallavic@oapa.astropa.unipa.it)
2 Astrophysics Division - Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG, Noordwijk, The Netherlands (ffavata@astro.estec.esa.nl)
3 Department of Physics and Astronomy, Leicester University, UK (pye@star.le.ac.uk)

Received 18 August 1998 / Accepted 1 December 1998


We present results from two deep ROSAT HRI exposures on the Blanco 1 open cluster. Blanco 1 is one of the few open clusters at large distance from the Galactic Plane. This circumstance has suggested that it may have formed through a mechanism different from that responsible for the other nearby clusters. The age of Blanco 1 is rather uncertain since, depending on the adopted age indicator, it ranges between 30 and 90 Myr. Many cluster members show chromospheric emission typical of young stars. The X-ray observations presented here reveal a high number of X-ray sources, consistent with the young age of the cluster. The typical X-ray luminosity of the cluster members is consistent with that of the Pleiades and significantly lower than the [FORMULA] Per members. These results suggest than the age of Blanco 1 is more similar to the age of the Pleiades than to that of [FORMULA] Per.

The time sampling of the X-ray observations allows us to study the variability of the sources on time scales from hours to 6 months - 1 year.

Key words: X-rays: stars – stars: coronae – Galaxy: open clusters and associations: individual: Blanco 1

Send offprint requests to: G. Micela

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© European Southern Observatory (ESO) 1999

Online publication: March 10, 1999