Properties of Two Late-Type Variable Stars of the Halo Population.

Abstract

view Abstract Citations (32) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Properties of Two Late-Type Variable Stars of the Halo Population. Preston, George ; Wallerstein, George Abstract Photoelectric and spectroscopic observations show that SX Her and TV Vir are similar to red giants in halo-type globular clusters in three respects: (1) they lie near the M3 giant sequence in the U - B, B - V plane; (2) they are metal-poor by factors of about 50; and (3) absolute magnitudes based on widths of the Ca ii emissions features are similar to those of the reddest giants in globular clusters if the Wilson-Bappu calibration is applicable. In addition, both stars have large space motions with respect to the sun. Radial-velocity and photometric data for SX Her indicate that maximum radius occurs at minimum light and vice versa. However, Wesselink's method leads to spurious estimates of the radius. No definite velocity variation was found for TV Vir. The hydrogen emission lines in SX Her arise below the region that produces the metallic absorption spectrum. The emissions are about 2 A wide and strong central reversals are present. At minimum light the emission at He is enhanced. In TV Vir hydrogen emission has been seen only at Ha. The metal deficiency of about a factor of 50 in both stars is shared by most elements, including oxygen and the elements heavier than strontium. In both stars manganese, and in TV Vir vanadium as well, is deficient by an additional factor of about 4. Publication: The Astrophysical Journal Pub Date: October 1963 DOI: 10.1086/147688 Bibcode: 1963ApJ...138..820P full text sources ADS | data products SIMBAD (4)