SIMBAD references

We present the results of ROSAT PSPC observations of the 30Myr old IC 2602 cluster; for the X-ray detected objects the results of a CCD photometric survey are also given. In X-rays, we detect a total of 110 objects within a 11deg² area, above a threshold of typically 3-5x10²⁸erg/sec. 68 of the detected objects have been identified with at least one optical counterpart; 44 of these are new optical candidates for cluster membership provided by our CCD photometry. Stars of all spectral types have been detected, from the very early- types to the late-M dwarfs. Soft X-ray luminosities range between about 10²⁹erg/sec to a few 10³⁰erg/sec, with the maximum and average L_X decreasing with spectral type for B-V larger than ∼0.8. Many of the stars redder than B-V∼0.8 show a L_X/L_bol ratio at about the saturation level of 10^–3. We construct X-ray luminosity distribution functions for objects in different color ranges and we compare them with those for the Pleiades. F, G, and early-K type candidates in IC 2602 appear to be more X-ray luminous than in the Pleiades, while no significant difference is seen among late-K and M dwarfs. Under the assumption that our IC 2602 sample is not severely affected by incompleteness, we argue that the above finding is related to the distribution of rotational velocities in the two clusters, with most of the late-type stars being fast rotators in both clusters, while, due to different spin-down timescales, the earlier type stars in IC 2602 are likely to rotate more rapidly than their counterparts in the Pleiades.