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A. G. Davis Philip (ISO and Union College), R. P. Boyle (Vatican Obs. Research Group), V. Strai\v{z}ys (ITPA, Lithuania)
The Strömvil Photometric system was devised by Straizys et al. (1996) to create photometric system that would allow the classification of stars by temperature, luminosity and metallicity types even in regions of high interstellar reddening. It is a combination of Strömgren and Vilnius photometry, employing the four filters of the Strömgren system and filters S, Z and P of the Vilnius system. Observations in the new system are being carried out at the Vatican Advanced Technology Telescope on Mt. Graham, Arizona. This paper reports on preliminary results of photometric measures made in the globular cluster, M 5. Using the VATT CCD, a 2k by 2k Loral chip with high quantum efficiency, even in the ultraviolet, the telescope images an area of six arcminutes square. This allowed us to image the central region of M 5 as well as the less populated areas surrounding the core. At the present time the y and b filters have been processed allowing us to prepare a color-magnitude diagram for the cluster. As in the case for M 92, a group of blue stars were found below the horizontal branch by about 0.5 mag. The majority of these stars are located in the cluster core. The next step in the reduction process is to reduce the u and v frames so the c1 index can be computed. In M 92, the stars below the BHB fell below the ZAMS in the c1, (b-y) diagram, confirming their lower luminosity and it will be interesting to see if this is true in M 5 as well.
REFERENCE
Straizys, V., Crawford, D. L. & Philip, A. G. D. 1996 Baltic Astronomy 5, 83
The author(s) of this abstract have provided an email address for comments about the abstract: AGDP@UNION.EDU