A ROSAT HRI study of the open cluster NGC 3532
Abstract
NGC 3532 is a very rich southern open cluster of age ~ 200-350 Myr; it is therefore a good candidate to investigate the X-ray activity-age-rotation relationship at ages intermediate between the Pleiades and the Hyades, where, to our knowledge, X-ray studies exist for only one cluster (NGC 6475). We have performed an X-ray study of NGC 3532 using HRI observations retrieved from the ROSAT archive. The observations have a limiting sensitivity Lx ~ 4 x 1028 erg sec-1 in the center of the field. We detected ~ 50 X-ray sources above a 4 sigma threshold, half of which have a known optical counterpart within 10 arcsec; 15 of the X-ray sources have at least one cluster member as optical counterpart. A comparison of NGC 3532 with the nearly coeval cluster NGC 6475 indicates that the former cluster is considerably X-ray underluminous with respect to NGC 6475. However, because of the existence of possible selection effects, additional X-ray and optical observations are needed before definitively concluding that the X-ray properties of NGC 3532 and NGC 6475 are significantly different.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- May 2000
- DOI:
- 10.48550/arXiv.astro-ph/0003091
- arXiv:
- arXiv:astro-ph/0003091
- Bibcode:
- 2000A&A...357..139F
- Keywords:
-
- GALAXY: OPEN CLUSTERS AND ASSOCIATIONS: INDIVIDUAL: NGC 3532;
- STARS: CORONAE;
- X-RAYS: STARS;
- Astrophysics
- E-Print:
- 6 pages, 3 figures, 3 tables, to appear in A&