Cool half of the H-R diagram in soft X-rays

Journal Article · Sun Nov 01 04:00:00 EST 1981 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159374· OSTI ID:5655641

Ayres, T R; Linsky, J L; Vaiana, G S; Golub, L; Rosner, R

We report results of an Einstein Guest Observing program to map the occurrence of soft x-ray emission, which is a signature of hot stellar coronae (T>10/sup 6/ K), in the cool half of the Hertzsprung Russell (H-R) diagram. We detect X-rays from F--M dwarfs and late F through early K giants, but not from the cooler giants, other than the spectroscopic binary epsilon Car (K0 II+B), or from any supergiants, other than Canopus (F0IB--II). The empirical separation of the cool half of the H-R diagram into a region where stellar soft X-ray emission is a common phenomenon, and a region where hot coronae are rare, if present at all among single stars, is similar to that found previously by Linsky and Haisch for C IV lambdalambda1548,1551 emission (Troughly-equal10/sup 5/ K) and by Stencel and Mullan for the onset of rapid mass loss in strong, cool (T< or approx. =10/sup 4/ K) stellar winds. We discuss the energy balance in the outer atmospheres of the coronal stars, the likely absorption of X-ray emission by cool winds in the ''hybrid-spectrum'' supergiants, a rotation-activity connection among the G dwarfs, and possible evolutionary origins of the structure seen in the cool half of the X-ray H-R diagram.

• Research Organization: Laboratory for Atmospheric and Space Physics, University of Colorado
• OSTI ID: 5655641
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 250:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640103* -- Astrophysics &amp; Cosmology-- Quasi-Stellar
Radio
&amp; X-Ray Sources-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
DIAGRAMS
DWARF STARS
ELECTROMAGNETIC RADIATION
EMISSION
ENERGY BALANCE
GIANT STARS
HERTZSPRUNG-RUSSELL DIAGRAM
IONIZING RADIATIONS
MOTION
RADIATIONS
ROTATION
SOFT X RADIATION
SPECTRA
STAR EVOLUTION
STARS
STELLAR ATMOSPHERES
STELLAR RADIATION
STELLAR WINDS
SUPERGIANT STARS
X RADIATION
X-RAY SPECTRA