γ Velorum

From our work in culminating in Jeffries (2009) it is now clear that the Wolf-Rayet binary γ2 Vel is the brightest member of the Vel OB2 association, and that around it there is a sub-group of low-mass stars. From that paper we will soon put on these pages the BVI optical catalogue (Table 2, in cluster format), and the results for the stars for which we have spectroscopy (Table 3). In addition there are tables of parameters for the X-ray sources with optical counterparts which lie in the pre-main-sequence parts of the CMD (Table 4a), and those that lie in the background region (Table 4b). (E-mail Rob if you want these tables before we place them on the web.)

We first discovered the pre-main-sequence stars around γ Vel in ROSAT data combined with an optical catalogue which we presented in Pozzo et al. At the time were the limited field-of-view of ROSAT meant we were concerned as to whether this represented an real over density of PMS stars or not. Fortunately there were similar ROSAT observations of a nearby field at similar galactic latitude (IX Vel) which we could use as an offset field. In his thesis Ben Burningham shows that the density of PMS stars in the offset field is much lower than in the γ Vel field, supporting the idea there is a real "cluster" around γ Vel. Ben's optical catalogue is available here. Also available are the catalogues of ROSAT X-ray sources, optical counterparts to ROSAT sources and X-ray selected PMS candidates. Details of how optical counterparts for X-ray sources were identified may be found in chapter 2 of Ben's thesis.