  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-rays 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 $L_{\mathrm x} \sim
4 \times 10^{28}$ 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.
