Red Subluminous Stars

Abstract

(UBVRI) observations of known subluminous stars were published in a previous discussion (Eggen, 1970a) where the bulk of the objects, both red (RSL) and blue (BSL) populated a sequence extending for M (I) near + 11 ^m_. 5 at (R — I) near 0 ^m_. 0 to M (I) of + 15^m near R —I= + 0 ^m_. 3. However, four RSL stars appeared to form a separate sequence near M(I)= +11^m and R — I between +0 ^m_. 3 and + 0 ^m_. 7. These four stars, plus an additional object (LTT 2236) are listed in Table I together with the source of luminosity; the weights of the trigonometric parallaxes are given in parentheses following the parallax. These five stars are represented in Figure 1 by crosses; the top of the steep sequence of subluminous stars is shown as the hatched region in the figure. For reference, Figure 1 also contains (1) the Hyades main sequence (Eggen, 1969b), indicated by a broken curve, (2) the evolved main sequence of the old disk population (Eggen, 1970b), shown by open circles, and (3) the subdwarfs, which are listed in Table II. In addition to the photometric results, Table II contains the Yale Parallax Catalogue number, the mean trigonometric parallax and its weight, in parentheses, as well as the resulting values of M (I).