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Excess Mid-Infrared Flux: An Indicator Of Mass Loss In Cepheids?, Edward G. Schmidt
Excess Mid-Infrared Flux: An Indicator Of Mass Loss In Cepheids?, Edward G. Schmidt
Edward Schmidt Publications
Spectral energy distributions for 132 classical and type II Cepheids were searched for evidence of excess flux above the photospheric level in the mid-infrared. Eight of them were found to have unambiguously strong excess emission while a further 13 showed evidence of weak emission. The presence of emission appears to be unrelated to either the pulsational amplitude or the effective temperature while strong emission is limited to stars with periods longer than 11 days, with a single exception. For the stars with strong emission we attempted to fit the energy distribution with a stellar wind model. No acceptable fit could …
Type Ii Cepheid Candidates. Iv. Objects From The Northern Sky Variability Survey, Edward G. Schmidt
Type Ii Cepheid Candidates. Iv. Objects From The Northern Sky Variability Survey, Edward G. Schmidt
Edward Schmidt Publications
We have obtained VR photometry of 447 Cepheid variable star candidates with declinations north of −14°30’, most of which were identified using the Northern Sky Variability Survey (NSVS) data archive. Periods and other photometric properties were derived from the combination of our data with the NSVS data. Atmospheric parameters were determined for 81 of these stars from low-resolution spectra. The identification of type II Cepheids based on the data presented in all four papers in this series is discussed. On the basis of spectra, 30 type II Cepheids were identified while 53 variables were identified as cool, main sequence stars …
Spectra Of Type Ii Cepheid Candidates And Related Stars, Edward G. Schmidt, Danielle Rogalla, Lauren Thacker-Lynn
Spectra Of Type Ii Cepheid Candidates And Related Stars, Edward G. Schmidt, Danielle Rogalla, Lauren Thacker-Lynn
Edward Schmidt Publications
We present low-resolution spectra for variable stars in the Cepheid period range from the ROTSE-I Demonstration Project and the All Sky Automated Survey, some of which were previously identified as type II Cepheid candidates. We have derived effective temperatures, gravities, and metallicities from the spectra. Based on this, three types of variables were identified: Cepheid strip stars, cool stars that lie along the red subgiant and giant branch, and cool main-sequence stars. Many fewer type II Cepheids were found than expected and most have amplitudes less than 0.4 mag. The cool variables include many likely binaries as well as intrinsic …
V371 Per — A Thick-Disk, Short-Period F/1o Cepheid, P. Wils, A. A. Henden, S. Kleidis, Edward G. Schmidt, D. L. Welch
V371 Per — A Thick-Disk, Short-Period F/1o Cepheid, P. Wils, A. A. Henden, S. Kleidis, Edward G. Schmidt, D. L. Welch
Edward Schmidt Publications
V371 Per was found to be a double-mode Cepheid with a fundamental mode period of 1.738 days, the shortest among Galactic beat Cepheids, and an unusually high period ratio of 0.731, while the other Galactic beat Cepheids have period ratios between 0.697 and 0.713. The latter suggests that the star has a metallicity [Fe/H] between −1 and −0.7. The derived distance from the Galactic plane places it in the thick disk or the Halo, while all other Galactic beat Cepheids belong to the thin disk. There are indications from historical data that both the fundamental and first overtone periods have …
Mining Sky Surveys For Astrophysically Interesting Variable Stars: The Cepheid Period Range, Edward G. Schmidt
Mining Sky Surveys For Astrophysically Interesting Variable Stars: The Cepheid Period Range, Edward G. Schmidt
Edward Schmidt Publications
We have undertaken a project to discover new type II Cepheids in two large-area sky surveys. However, most of the candidates from the surveys differ from type II Cepheids in their amplitude and period distributions and they form a separate, cooler sequence relative to the Cepheids in a temperature-gravity plot. We refer to these objects as "Cepheid-lke" stars. Many exhibit unstable pulsation which we illustrate with representative light curves.
Photometry Of Type Ii Cepheid Candidates From The Rotse-I Demonstration Project, Edward G. Schmidt, Shawn Langan, Danielle Rogalla, Lauren Thacker-Lynn
Photometry Of Type Ii Cepheid Candidates From The Rotse-I Demonstration Project, Edward G. Schmidt, Shawn Langan, Danielle Rogalla, Lauren Thacker-Lynn
Edward Schmidt Publications
We have obtained VR photometry of 205 Cepheid variable star candidates that were discovered in a small section of the Northern Sky Variability Survey. Given their locations and apparent magnitudes, any stars in this sample that are Cepheids are very likely to be type II Cepheids. On the basis of the regularity of variation, revised periods, light-curve morphology, slope of the color-magnitude relation, and color, we have identified 97 probable Cepheids and 17 possible Cepheids. While some of the photometric properties, particularly the colors, are consistent with the identification of these stars as Cepheids, the amplitudes are small compared to …
Four-Color And Hβ Photometry Of Stars In Ngc 7654 And M25, Edward G. Schmidt
Four-Color And Hβ Photometry Of Stars In Ngc 7654 And M25, Edward G. Schmidt
Edward Schmidt Publications
Four-color and Hβ photometry has been obtained of stars in the galactic clusters NGC 7654 and M25. An analysis of these data shows variable extinction in both clusters. The distance modnlus of NGC 7654 is found to be 10m.99 ± 0.2 and that of M25 is 8m.68 ± 0.1.