Spectral Classification for New or Unclassified Late-Type Variables, Emission-Line Stars, S Stars, and Planetary Nebulae.

1964 ◽  
Vol 139 ◽  
pp. 864 ◽  
Author(s):  
J. J. Nassau ◽  
C. B. Stephenson ◽  
G. Caprioli
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
Spectral Classification ◽  
Late Type

scholarly journals Weak emission line central stars of planetary nebulae

2011 ◽  
Vol 7 (S283) ◽  
pp. 510-511
Author(s):  
Helga Todt ◽  
Miriam Peña ◽  
Julia Zühlke ◽  
Lida Oskinova ◽  
Wolf-Rainer Hamann ◽  
...  
Keyword(s):  
Mass Loss ◽  
Emission Line ◽  
Hydrogen Content ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
Detailed Knowledge ◽  
Spectral Classification ◽  
Balmer Lines ◽  
Formation And Evolution ◽  
Central Stars

AbstractTo understand the evolution and morphology of planetary nebulae, a detailed knowledge of their central stars is required. Central stars that exhibit emission lines in their spectra, indicating stellar mass-loss allow to study the evolution of planetary nebulae in action. Emission line central stars constitute about 10 % of all central stars. Half of them are practically hydrogen-free Wolf-Rayet type central stars of the carbon sequence, [WC], that show strong emission lines of carbon and oxygen in their spectra. In this contribution we address the weak emission-lines central stars (wels). These stars are poorly analyzed and their hydrogen content is mostly unknown. We obtained optical spectra, that include the important Balmer lines of hydrogen, for four weak emission line central stars. We present the results of our analysis, provide spectral classification and discuss possible explanations for their formation and evolution.

scholarly journals An atlas of cool supergiants from the Magellanic Clouds and typical interlopers

2018 ◽  
Vol 618 ◽  
pp. A137 ◽  
Author(s):  
Ricardo Dorda ◽  
Ignacio Negueruela ◽  
Carlos González-Fernández ◽  
Amparo Marco
Keyword(s):  
Photographic Plate ◽  
Magellanic Clouds ◽  
Spectral Classification ◽  
Late Type ◽  
Spectral Ranges ◽  
Work Done

We present an atlas composed of more than 1500 spectra of late-type stars (spectral types from G to M) observed simultaneously in the optical and calcium triplet spectral ranges. These spectra were obtained as part of a survey to search for cool supergiants in the Magellanic Clouds and were taken over four epochs. We provide the spectral and luminosity classification for each spectrum (71% are supergiants, 13% are giants or luminous giants, 4% are carbon or S stars, and the remaining 12% are foreground stars of lesser luminosities). We also provide a detailed guide for the spectral classification of luminous late-type stars, the result of the extensive classification work done for the atlas. Although this guide is based on classical criteria, we have put them together and re-elaborated them for modern CCD-spectra as these criteria were scattered among many different works and mainly conceived for use with photographic plate spectra. The result is a systematic, well-tested process for identifying and classifying luminous late-type stars, illustrated with CCD spectra of standard stars and the classifications of our own catalogue.

scholarly journals Hybrid 3-D Spectrophotometry of Emission-Line Nebulae at Ohio State

1995 ◽  
Vol 149 ◽  
pp. 167-171
Author(s):  
Richard W. Pogge ◽  
Nancy Joanne Lame
Keyword(s):  
Emission Line ◽  
Planetary Nebulae ◽  
Hii Regions ◽  
Ohio State University ◽  
State University ◽  
Considerable Success ◽  
Fabry Perot ◽  
The Ohio State University ◽  
Scientific Results ◽  
Narrowband Filter

AbstractA program of 3-D spectrophotometry of emission nebulae being carried out at the Ohio State University will be described. We have had considerable success combining Fabry-Perot imaging, long-slit spectroscopy, and narrowband filter imaging into a hybrid 3-D spectroscopic approach that we have used to obtain detailed spectrophotometric maps of the density, temperature, extinction, and ionization in HII regions and Planetary Nebulae. The centerpiece instrument of this effort, the OSU Imaging Fabry-Perot Spectrograph (IFPS), will be described, and scientific results illustrative of our work will be presented.

scholarly journals Spectral classification of emission-line galaxies

1987 ◽  
Vol 63 ◽  
pp. 295 ◽  
Author(s):  
Sylvain Veilleux ◽  
Donald E. Osterbrock
Keyword(s):  
Emission Line ◽  
Spectral Classification ◽  
Emission Line Galaxies

scholarly journals The Ionization of Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 190-204 ◽  
Author(s):  
Robert E. Williams
Keyword(s):  
Ionizing Radiation ◽  
Emission Line ◽  
Radiation Field ◽  
Planetary Nebulae ◽  
Model Atmosphere ◽  
Evolutionary Sequence ◽  
Lyman Continuum ◽  
The Mean ◽  
Central Stars

The ionization of the most abundant elements in planetary nebulae has been determined for a number of models of nebulae at different epochs in their expansion. The values used for the temperatures and radii of the central stars and the sizes and densities of the shells have come from Seaton's evolutionary sequence. The ionizing radiation field has been taken from model atmosphere calculations of the central stars by Gebbie and Seaton, and Böhm and Deinzer. Emission-line fluxes have been calculated for the models and compared with observations of planetary nebulae by O'Dell, Osterbrock's group, and Aller and his collaborators. Results indicate that the central stars have strong He+ Lyman continuum excesses, similar to those predicted by Gebbie and Seaton. The mean abundance determinations for the nebulae made by Aller are confirmed, with the exception of nitrogen, which appears to be 3 or 4 times more abundant than his value. It is also seen that the electron temperatures of the nebulae are higher than previous theoretical determinations, providing better agreement with empirically derived values.

scholarly journals Spectral Anomalies in the Hyades and Pleiades and in Field Stars with Active Chromospheres

1985 ◽  
Vol 111 ◽  
pp. 415-416
Author(s):  
James A. Rose
Keyword(s):  
Wavelength Range ◽  
Classification System ◽  
Three Dimensional ◽  
Spectral Classification ◽  
Atmospheric Parameters ◽  
Late Type ◽  
Image Tube ◽  
Photographic Image ◽  
Normal Field ◽  
Diagnostic Indices

Widened photographic image-tube spectra at 50 Å mm−1 dispersion have been obtained for a large number of late-type field dwarfs and giants with well-determined atmospheric parameters and for 35 Hyades dwarfs and 31 Pleiades dwarfs. The spectra have a resolution of 2.5 Å and cover the wavelength range λλ3400–4500 Å. A new quantitative three-dimensional spectral classification system is derived for late-type stars and is calibrated using the sample of field dwarfs and giants with known atmospheric parameters. Diagnostic indices are defined by comparing the counts in the bottoms of two neighboring absorption lines or by comparing the counts in two neighboring pseudocontinuum peaks.It is found that the Hyades and Pleiades dwarfs and field dwarfs with strong Ca II H and K emission reversals exhibit well-defined anomalies in their diagnostic indices when compared with normal field dwarfs. These results are summarized in Rose (1984). In LaBonte and Rose (1984), it is shown, from spectra of solar magnetic plages, that all spectral and photometric peculiarities of the Hyades discovered to date, including the original “Hyades anomaly” (Crawford 1969; Strömgren et al. 1982), are manifestations of plage activity.

scholarly journals OH masers in envelopes of late type stars

1987 ◽  
Vol 122 ◽  
pp. 243-244
Author(s):  
A.M. Le Squeren ◽  
P. Sivagnanam ◽  
F. Tran Minh ◽  
M. Dennefeld ◽  
F. Foy
Keyword(s):  
Radio Telescope ◽  
Detection Rate ◽  
Point Sources ◽  
Spectral Classification ◽  
Late Type ◽  
Maser Emission ◽  
Galactic Longitude

Two studies of OH maser emission in envelopes of late type stars -miras (3) and OH/IR objects- have been performed with the Nancay radio-telescope. Mainly, the OH miras are found with thicker dust envelopes than the non OH ones. A sample of unidentified IRAS point sources selected on their colors has been observed. We have detected 46 new OH sources. The OH detection rate is a function of the galactic longitude and of the IRAS spectral classification.

scholarly journals Photometry of AM Her Stars – Line and Continuum Emission

1979 ◽  
Vol 53 ◽  
pp. 324-328
Author(s):  
Paula Szkody
Keyword(s):  
Emission Line ◽  
White Dwarf ◽  
Main Sequence ◽  
Close Binary ◽  
Line Spectrum ◽  
Continuum Emission ◽  
Late Type ◽  
Emission Line Spectrum ◽  
Orbital Periods

The 4 known AM Her stars or polars (AM Her, ANUMa, W Pup, and 2A0311-227) are characterized by large circular polarizations of 10-35%, (Tapia 1977a, b, Krzeminski and Serkowski 1977), an emission line spectrum with strong H and He lines (Crampton and Cowley 1977, Greenstein et al. 1977), complex photometric variations (Szkody 1978, Priedhorsky and Krzeminski 1978, Warner & Nather 1972), long term high and low states and short orbital periods (80-180 min.). Models of these systems envision a close binary containing a magnetic white dwarf primary (B ~ 108G) and late type main sequence secondary transferring material into an accretion funnel over one or both poles of the white dwarf (Stockman et al. 1977, Lamb & Masters 1979, Liebert et al. 1978).

scholarly journals Emission-Line Profiles in Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 267-269
Author(s):  
Donald E. Osterbrock
Keyword(s):  
Velocity Distribution ◽  
Emission Line ◽  
Observational Data ◽  
Planetary Nebulae ◽  
Line Profiles ◽  
Measured Velocity ◽  
Hydrodynamical Models ◽  
Internal Velocity ◽  
First Time

This research was undertaken with the idea of measuring as accurately as possible the internal-velocity distribution in planetary nebulae, in order to compare the observational measurements with hydrodynamical models of expanding nebulae. Much of the work was done in collaboration with J. S. Miller and D.W. Weedman. All the observational data were obtained photographically with the Coudé spectrograph of the 100-inch telescope at Mt. Wilson, using an image rotator, a 900 line/mm grating, and an F/5-2 camera, giving a dispersion of about 4 Å/mm in the blue and about 6 Å/mm in the red. The measured velocity resolution is approximately 5–6 km/sec. The data for five nebulae have been published (Osterbrock et al., 1966) while data for three more, NGC 2392, NGC 3242, and IC 418 are discussed here for the first time.

Sign in / Sign up

Export Citation Format

Share Document