IUE and Einstein survey of late-type giant and supergiant stars and the dividing line

• Published in: The Astrophysical journal Vol. 361; no. 2; pp. 570 - 589
• Main Authors: Haisch, Bernhard M., Bookbinder, Jay A., Maggio, A., Vaiana, G. S., Bennett, Jeffrey O.
• Format: Journal Article
• Language: English
• Published: Legacy CDMS University of Chicago Press 01.10.1990
• Subjects: 640102 - Astrophysics & Cosmology- Stars & Quasi-Stellar, Radio & X-Ray Sources; Astronomy; Astrophysics; CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; DIAGRAMS; Earth, ocean, space; ELECTROMAGNETIC RADIATION; Exact sciences and technology; Giant and subgiant stars; GIANT STARS; HERTZSPRUNG-RUSSELL DIAGRAM; IONIZING RADIATIONS; Normal stars (by class): general or individual; RADIATIONS; SPECTRA; STAR EVOLUTION; STARS; STELLAR ACTIVITY; SUPERGIANT STARS; ULTRAVIOLET RADIATION; ULTRAVIOLET SPECTRA; X RADIATION; Data analysis; Stellar evolution; Flux density; Stellar corona; Ultraviolet spectrum; Emission line star; Data table; Giant; Ultraviolet observation; X ray emission; Photometry; Supergiant; Hertzsprung Russel diagram; Late type star
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/169221

Results are presented on an IUE UV survey of 255 late-type G, K, and M stars, complementing the Maggio et al. (1990) Einstein X-ray survey of 380 late-type stars. The large data sample of X-ray and UV detections make it possible to examine the activity relationship between the X-ray and the UV emissions. The results confirm previous finding of a trend involving a steeply-dropping upper envelope of the transition region line fluxes, f(line)/f(V), as the dividing line is approached. This suggests that a sharp decrease in maximum activity accompanies the advancing spectral type, with the dividing line corresponding to this steep gradient region. The results confirm the rotation-activity connection for stars in this region of the H-R diagram.