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2. IC 2602

The cluster IC 2602 (tex2html_wrap_inline1261, tex2html_wrap_inline1263, J2000.0) is a group of stars distributed about the B0Vp star tex2html_wrap_inline1265 Carinae. Early studies (Whiteoak 1961; Braes 1962) determined the cluster to be at a distance of tex2html_wrap_inline1267. They estimated the cluster to be approximately tex2html_wrap_inline1269 old, derived both from the nuclear age of tex2html_wrap_inline1265 Car, and the contraction of cluster members on to the main sequence. More recent studies (Mermilliod 1981) estimate the age to be nearer 36 Myr.

The reddening has been determined to be EB-V=0.04 (Whiteoak 1961; Braes 1962) corresponding to EV-I=0.044 (Randich et al. 1995). Photometric measurements for the brighter stars were obtained (Braes 1962; Whiteoak 1961 and Hill & Perry 1969), and some of these stars have been studied spectroscopically (Whiteoak 1961; Abt & Morgan 1972). From measurements of 22 confirmed members, Braes (1962) has estimated the mean cluster proper motion to be tex2html_wrap_inline1277 1.0 mas/yr, tex2html_wrap_inline1279 mas/yr.

More recently the cluster has been studied in the X-ray wavelength region (Randich et al. 1995). The X-ray data from ROSAT PSPC pointings detected 110 objects, 68 of which were identified with optical counterparts. The study also included CCD photometry in V and I of the central 3.3 square degrees of cluster, with a magnitude limit of V<18, and the photometry of the optical counterparts was used to determine the likelihood of the counterparts being cluster members. Additional photometry was published by Prosser et al. (1996). 44 of the X-ray sources were deemed to be possible cluster members. The X-ray luminosity distribution function for the F, G and early K stars showed the cluster to be more X-ray luminous than the Pleiades. There was little difference for the late K and M-type stars. Randich et al. argue that, unless their sample is affected by incompleteness, their result is consistent with the younger age of IC 2602 compared with the Pleiades, the younger earlier type stars having had less time to spin down and thereby decrease X-ray luminosity. The later types, having longer braking timescales, would be rapid rotators in both clusters and hence have similar X-ray luminosities.


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