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Session 26 - Stars in the Visible & IR.
Display session, Tuesday, June 10
South Main Hall,
The identification of a group of stars found below the horizontal branch in the globular cluster M 92 has been described in earlier papers. A review paper (Philip, 1996, Baltic Astronomy 5, 425) presents some four-color plots showing the location of various types of stars on, and near the horizontal branch. A natural group of less luminous stars has been found in plots of the four-color data. Additional studies have ruled out random errors in the photometry causing this grouping of stars about half a magnitude below the horizontal branch. If a BHB star forms an optical pair with one of the fainter, redder stars on the main-sequence, the combination would result in a star with a somewhat higher luminosity and a redder color. The new position of the star in the HR diagram does not go through the positions occupied by the new group below the HB. Also, the distribution of such points does not scatter near the HB and thin out as one gets further away from the HB. Instead the HR diagram shows a region empty of points and then a distinct group of stars. Recently I have found some new CM-Diagrams of M 92, by other investigators, which show the same distribution of stars. Investigations are now underway at the VATT, on Mt. Graham, Arizona, to investigate these stars in the Strömvil system (Strai\vzys, Crawford and Philip, 1996, Baltic Astronomy 5, 84).
