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Series

1984

Edward Schmidt Publications

Articles 1 - 6 of 6

Full-Text Articles in Physics

Yellow Giants In Young Clusters. Ii. A Comparison Of Observation With Theory, Edward G. Schmidt Dec 1984

Yellow Giants In Young Clusters. Ii. A Comparison Of Observation With Theory, Edward G. Schmidt

Edward Schmidt Publications

Luminosities and effective temperatures are calculated for 17 nonvariable yellow giants and supergiants and nine Cepheids which were previously identified as members of open clusters. These stars are identified as being in the helium core burning stage of evolution. A comparison with the predictions of pulsation theory does not show any disagreement. On the other hand, several comparisons with the theory of stellar evolution produce discrepancies which suggest that effects neglected in the calculations may play an important role in the evolution of these stars.


The Luminosity Scale Of Cepheid Variable Stars: A Revision, Edward G. Schmidt Oct 1984

The Luminosity Scale Of Cepheid Variable Stars: A Revision, Edward G. Schmidt

Edward Schmidt Publications

The period-luminosity-color relation for classical Cepheids is discussed in terms of a recent re-determinations of the distance moduli of open clusters with Cepheid members. The distance moduli of eight clusters with well established Cepheid members were determined from Stromgren four-color and Hβ photometry of the B stars. Possible sources of systematic errors in these distance moduli are discussed. Zero points are derived from these data for the period-luminosity-color (PLC) relation on the UBV system and the period-luminosity relations for near-infrared magnitudes. The present relations yield absolute magnitudes which are fainter by 0.4-0.6 mag than those now commonly used ...


Yellow Giants In Young Clusters. I. Photometric Observations, Edward G. Schmidt Jul 1984

Yellow Giants In Young Clusters. I. Photometric Observations, Edward G. Schmidt

Edward Schmidt Publications

To enable a study of the properties of luminous yellow stars, a list has been compiled of 84 stars which appear to be in the appropriate region in the color-magnitude diagrams of 41 young clusters. Proper motions, radial velocities, UBV photometry, and spectral types from the literature have been used in those cases where such data are available to assign membership probabilities. DDO and uvby photometry have also been obtained of most of the stars in the list, and these data are analyzed to remove stars from the sample which have the wrong luminosity or the wrong color excess for ...


The Chromospheres Of Classical Cepheids. 111. A Search For Transition Region Emission Lines, Edward G. Schmidt, Sidney B. Parsons Apr 1984

The Chromospheres Of Classical Cepheids. 111. A Search For Transition Region Emission Lines, Edward G. Schmidt, Sidney B. Parsons

Edward Schmidt Publications

In previous studies of Cepheid chromospheres with the IUE, we found that the chromospheric emission is strongly dependent on the period of the star and varies substantially through the cycle. For the shortest period star in our sample, δ Cep, we were able to detect little significant chromospheric emission in the short wavelength region, and we were only able to detect transition region emission in the longest period star, 1 Car. However, the upper limits on these emissions were slightly above expected flux levels for nonvariable stars. To detect them or place lower and physically more interesting limits on the ...


A Search For Chromospheric Emission In Tu Cassiopeiae Spectra, Arne A. Henden, Robert H. Cornett, Edward G. Schmidt Apr 1984

A Search For Chromospheric Emission In Tu Cassiopeiae Spectra, Arne A. Henden, Robert H. Cornett, Edward G. Schmidt

Edward Schmidt Publications

We have searched high-resolution spectra of the multimode cepheid TU Cas for evidence of chromospheric emission. Spectral regions covered include the Ca II near-IR triplet near 8600 Å, Hα, CanII H and K, Mg II h and k; phase coverage in both primary and secondary modes was reasonably complete. There was no evidence for changes other than those caused by temperature variation. The observed lack of emission makes unlikely current mass loss (and resulting helium enrichment) by means of stellar winds.


The Chromospheres Of Classical Cepheids. 11. High-Resolution Profiles Of The Mg Ii H And K Lines, Edward G. Schmidt, Sidney B. Parsons Apr 1984

The Chromospheres Of Classical Cepheids. 11. High-Resolution Profiles Of The Mg Ii H And K Lines, Edward G. Schmidt, Sidney B. Parsons

Edward Schmidt Publications

High-resolution spectra have been obtained with the long-wavelength camera of the International Ultraviolet Explorer for five Cepheids at a number of phases each. These data were used to study the profiles of the Mg II h and k lines near 2900 Å. An emission feature often appears at the centers of the two lines. There are also central absorption features due to circumstellar or interstellar gas. They are often multiple and may or may not divide the emission into two peaks. The velocities of the circumstellar absorption components imply that they originate in a region which is at least several ...