Ultraviolet observations of cool stars. III. Chromospheric and coronal lines in $alpha$ Tauri, $beta$ Geminorum, and $alpha$ Bootis

Journal Article · Sat Nov 15 04:00:00 EST 1975 · Astrophys. J., v. 202, no. 1, pp. 165-182

DOI:https://doi.org/10.1086/153961· OSTI ID:4108283

McClintock, W; Linsky, J L; Henry, R C; Moos, H W; Gerola, H

The ultraviolet spectrometer of the Princeton Experiment Package aboard the Copernicus satellite has been used to obtain high-resolution measurements of L$alpha$, the Mg ii lambda2800 doublet, and upper limits on the Si iii lambda1206 line in the K giants $alpha$ Tau and $beta$ Gem. The intensities and line shapes are compared with earlier observations of $alpha$ Boo. The L$alpha$ and Mg ii profiles for $alpha$ Tau resemble those for $alpha$ Boo, in that they are highly asymmetrical, while $beta$ Gem shows much more symmetrical profiles. The asymmetries for all lines except for those of $alpha$ Boo and Mg ii lines of $alpha$ Tau could be due to interstellar absorption. In the case of $beta$ Gem only, the O v intercombination line at 1218 A is observed, suggesting a well- developed corona substantially cooler than that of the Sun. The L$alpha$ profiles of $alpha$ Tau and $beta$ Gem are consistent with the low interstellar hydrogen abundance in the solar neighborhood previously obtained from a similar observation of the $alpha$ Boo L$alpha$ profile. The strength of the Mg ii lambda2796 line can be used to measure transition region and coronal pressures, and indicates a decrease in both with later spectral type and/or increasing luminosity. (AIP)

• Research Organization: Johns Hopkins Univ., Baltimore, MD
• Sponsoring Organization: USDOE
• NSA Number: NSA-33-018036
• OSTI ID: 4108283
• Journal Information: Astrophys. J., v. 202, no. 1, pp. 165-182, Journal Name: Astrophys. J., v. 202, no. 1, pp. 165-182; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

*GIANT STARS-- ULTRAVIOLET SPECTRA
640102* --Physics Research--Astrophysics & Cosmology--Stars
ABSORPTION
CHROMOSPHERE
HYDROGEN
MAGNESIUM
N56200* --Physics (Astrophysics & Cosmology)--Stars
OXYGEN
SILICON
TEMPERATURE DEPENDENCE