scholarly journals The Chromospheres of Carbon Stars

2000 ◽  
Vol 177 ◽  
pp. 105-114 ◽  
Author(s):  
Donald G. Luttermoser
Keyword(s):  
High Resolution ◽  
Carbon Star ◽  
High Dispersion ◽  
Late Type ◽  
Carbon Stars ◽  
Giant Stars ◽  
Show Evidence ◽  
Chromospheric Emission ◽  
Type Giant ◽  
Low Dispersion

Most oxygen-rich late-type giant stars show evidence for chromospheres in their visual spectra (e.g. Ca ii H & K emission features). Cool (i.e. N-type) non-Mira carbon stars, however, have never been observed to have chromospheric emission in their Ca ii H & K lines. However, faint Mg ii h & k lines were detected in emission in low-dispersion IUE spectra of the brightest cool carbon stars in the early 1980s. May 1984 saw the first (and only) successful high-dispersion IUE spectrum taken of a cool carbon star, TX Psc (N0; C6,2). Armed with this high-dispersion spectrum, as well as low-dispersion IUE and ground-based spectra, Luttermoser et al. (1989) made the first detailed attempt to semiempirically model the chromosphere of a cool carbon star. This model was successful in reproducing the Mg ii lines, but it was not well constrained due to the lack of other observed high-resolution chromospheric profiles for comparison. Modeling carbon star chromospheres can now be addressed more accurately with HST/GHRS high-resolution spectra. New fluoresced emission features have been discovered in the GHRS spectra of carbon stars that are not present in their oxygen-rich counterparts.

scholarly journals Why We Need a Deep Spectral Survey of the Milky Way

1995 ◽  
Vol 148 ◽  
pp. 337-343 ◽  
Author(s):  
Omar M. Kurtanidze ◽  
Miriam G. Nikolashvili
Keyword(s):  
Near Infrared ◽  
Milky Way ◽  
Short Review ◽  
Late Type ◽  
Giant Stars ◽  
Infrared Spectral ◽  
Objective Prism ◽  
Type Giant ◽  
Spectral Survey ◽  
Low Dispersion

AbstractIn this short review we briefly discuss all the extensive low dispersion objective-prism spectral surveys carried out in the last fifty years for the study of the surface and space distributions of late-type giant stars, namely C stars. In the light of data obtained and new discoveries, the expediency of undertaking a deep mI low dispersion spectral survey in the near-infrared spectral region is considered.

Magnesium emission variability among late-type giant stars

1982 ◽  
Vol 253 ◽  
pp. 716 ◽  
Author(s):  
D. J. Mullan ◽  
R. E. Stencel
Keyword(s):  
Late Type ◽  
Giant Stars ◽  
Type Giant

scholarly journals Stellar activity

1986 ◽  
Vol 118 ◽  
pp. 283-283
Author(s):  
D. K. Duncan
Keyword(s):  
Sunspot Cycle ◽  
Late Type ◽  
Stellar Activity ◽  
Giant Stars ◽  
Rotation Periods ◽  
Type Giant

We have been monitoring the CaII H and K emission in late-type giant stars using the Mt Wilson 60-inch telescope. It is a continuation of work that Olin Wilson began almost 20 years ago. As a result not only have starspot cycles been detected (equivalent to the solar sunspot cycle), but rotation periods have now been measured.

scholarly journals Chromospheres and Winds of Cool Stars

1992 ◽  
Vol 9 ◽  
pp. 477-479
Author(s):  
Kenneth G. Carpenter
Keyword(s):  
High Resolution ◽  
Complex Shape ◽  
The Self ◽  
Line Profiles ◽  
Late Type ◽  
Hybrid Star ◽  
Star Models ◽  
Cool Stars ◽  
Type Giant ◽  
Early Operations

I present data acquired during the early operations era of the HST with the Goddard High Resolution Spectrograph (GHRS) on three late-type giant and supergiant stars: α Tau (K5 III non-coronal), λ Dra (K5 III hybrid), and α Ori (M2 lab). Figure 1 shows fits to echelle (R=100,000) line profiles of three ions seen in the spectrum of α Tau. The Co II line can be fit with a single gaussian, the self-reversed Fe II line with a combination of an emission and absorption gaussian, but the unreversed C II lines require two emission gaussians of substantially different FWHM and maxima. The complex shape of the C II profiles suggests that the turbulent velocity distribution in the chromosphere is anisotropic (e.g. Gray 1988) or that the lines are formed in two regions characterized by significantly different Teff and Vturb, as in the hybrid star models of Harper (1991).

scholarly journals Evidence against Formation of the Stellar Bulge by Mergers Taking Place over a Hubble Time

1989 ◽  
Vol 136 ◽  
pp. 63-69
Author(s):  
R.M. Rich
Keyword(s):  
Simple Model ◽  
Chemical Evolution ◽  
Carbon Star ◽  
Infrared Photometry ◽  
Carbon Stars ◽  
Abundance Distribution ◽  
Giant Stars ◽  
Evolved Stars ◽  
The Galaxy ◽  
Hubble Time

Data on abundances and ages of stars in the nuclear bulge of the Galaxy are in conflict with a scenario in which the bulge has been slowly accumulated by mergers of Magellanic Cloud-like systems taking place over a Hubble Time.I review the abundance distribution of 88 K Giant stars in Baade's window, and show that the distribution is fit by the simple model of chemical evolution unmodified by gas infall. The metal rich stars in the bulge could not have formed in small galaxies of ≈ 1010 solar masses, which do not retain their metal-enriched gas.Two large surveys of luminous evolved stars in the bulge–the M giant surveys of Blanco, and the carbon star surveys of Azzopardi, Lequeux, and Rebeirot, find no luminous carbon stars or M supergiants which would signify the presence of an intermediate-age population. I present infrared photometry of 33 bulge carbon stars which shows that they are intrinsically faint, confirming the lack of an intermediate age population.The lack of young turnoff stars in the color-magnitude diagrams of bulge fields by Terndrup and Rich further strengthens the case against a substantial bulge population younger than 5 Gyr.

Luminosity and Temperature from Near-Infrared Spectra of Late-Type Giant Stars

1997 ◽  
Vol 113 ◽  
pp. 1411 ◽  
Author(s):  
S. V. Ramirez ◽  
D. L. Depoy ◽  
Jay A. Frogel ◽  
K. Sellgren ◽  
R. D. Blum
Keyword(s):  
Infrared Spectra ◽  
Near Infrared ◽  
Late Type ◽  
Giant Stars ◽  
Near Infrared Spectra ◽  
Type Giant
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