Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000aas...197.4415l&link_type=abstract
American Astronomical Society, 197th AAS Meeting, #44.15; Bulletin of the American Astronomical Society, Vol. 32, p.1474
Astronomy and Astrophysics
Astronomy
3
Scientific paper
This preliminary study of the detailed chromospheric conditions of G-type Ib-supergiants provides a foundation for atmospheric models, complementing STIS and FUSE surveys of cool stars. We compare optical and near-UV high-resolution Utrecht Echelle Spectrograph (William Herschel Telescope), and SOFIN (Nordic Optical Telescope) echelle spectra of α Aqr (G2 Ib), 9 Peg (G5 Ib), and ɛ Gem (G8 Ib) with the Ia-supergiant HD 179821 (G2-G5). The latter has recently been proposed as a post-AGB star (with a detached dust shell), instead of a population I massive supergiant, for which we do not detect chromospheric emission in Ca ii H & K. The three Ib-supergiants reveal much stronger Hα absorption lines than HD 179821, while the core intensities of Hβ and Hδ (showing broad damping line wings) in α Aqr, ɛ Gem, and HD 179821 are similar. The Hα profile of HD 179821 has a weak absorption core with satellite emission, typically formed in a supersonic expanding wind. This is regularly observed in very luminous cool pulsating super- and hypergiants of the ρ Cas-type (F2-G Ia+), which lack H & K emission. Our spectral synthesis of these observations shows that the Hα absorption in G Ib-supergiants is strongly enhanced due to chromospheric excitation, whereas the higher Balmer lines are mainly of photospheric origin. This finding is parallel to the chromospheric nature of Hα absorption in α Ori (M2 Iab), recently discussed by Lobel & Dupree (ApJ, 545, Dec. 2000). This research is supported in part by STScI grant GO-08280.02-97A to the SAO.
Dupree Andrea K.
Lobel Alex
No associations
LandOfFree
The Chromospheres of G-type Ib Supergiants does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Chromospheres of G-type Ib Supergiants, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Chromospheres of G-type Ib Supergiants will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1724218