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| Paper: |
Photometric and Spectroscopic Study of the Brightest Northern Cepheids |
| Volume: |
135, A Half Century of Stellar Pulsation Interpretations: a Tribute to Arthur N. Cox |
| Page: |
173 |
| Authors: |
Kiss, L. L. |
| Abstract: |
Recently we have carried out simultaneous UBV and uvby photometry of the brightest northern Cepheids at Szeged Observatory using the 0.4 m telescope. The two year-long photometry contains about 3500 individual data points for 17 stars. We have handled the standard transformations very carefully, therefore the final accuracy is about 0.01-0.02 for V, B-V, U-B, b-y, and for m1, c1, respectively. Due to the simultaneity of the data series it has been possible to determine the transformations between the two photometric systems. The slope of the (B-V)-(b-y) conversion differs significantly from the widely used value. This may explain the color-dependent differences between several reddening determinations which have been based on different photometric systems. We have applied a few empirical methods to obtain Cepheid reddenings and we have shown that Stromgren photometry gives more consistent values.Temperature and log g determinations are presented using the recent model atmospheres and synthetic colors. We show that the few published calibrations (Teff and log g via Stromgren photometry) is in a fairly good agreement with our conclusions. The period-Teff, period-log g and period-[Fe/H] relations show only weak trends with a quite large scatter, therefore they give us only rough estimates for these parameters. Almost simultaneously with the photometric measurements, we have taken high resolution (R = 30000) spectra between 6200-6600 at the David Dunlap Observatory using the 1.88 m telescope and the echelle spectrograph. The close simultaneity enabled us to compute precise Baade-Wesselink radii because there was no phase shift between light and radial velocity curves due to the long-term period changes. Our results are generally in good agreement with the previously published values. This indicates that the phase mismatch has been correctly handled in the earlier studies. |
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