GAPHE, Département AGO, Université de Liège, Allée du 6 Août 17, Bat. B5C, 4000
2 Astronomical Institute Anton Pannekoek, Amsterdam University, Science Park 904, 1098 XH Amsterdam, The Netherlands
3 CRESST/NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771; Univ. Space Res. Ass., Columbia, MD, USA
Received: 14 January 2013
Accepted: 15 May 2013
Using XMM-Newton data, we study for the first time the X-ray emission of HM1 and IC 2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both clusters display the usual high-energy properties of that type of objects, though with log [LX/LBOL] apparently lower in HM1 than in IC 2944/2948. Compared with studies of other clusters, it seems that a low signal-to-noise ratio at soft energies, due to the high extinction, may be the main cause of this difference. In HM1, the two Wolf-Rayet stars show contrasting behaviors: WR89 is extremely bright, but much softer than WR87. It remains to be seen whether wind-wind collisions or magnetically confined winds can explain these emissions. In IC 2944/2948, the X-ray sources concentrate around HD 101205; a group of massive stars to the north of this object is isolated, suggesting that there exist two subclusters in the field-of-view.
Key words: open clusters and associations: individual: HM1 / open clusters and associations: individual: IC 2944 / stars: early-type / open clusters and associations: individual: IC 2948 / X-rays: stars
Tables 2, 5, and Figs. 5, 9 are available in electronic form at http://www.aanda.org
Based on observations collected with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).
Tables 1, 3 and 4 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/555/A83
© ESO, 2013