Other
Scientific paper
Dec 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004aas...20517408e&link_type=abstract
American Astronomical Society Meeting 205, #174.08; Bulletin of the American Astronomical Society, Vol. 37, p.378
Other
Scientific paper
We report on the results of an ongoing study of the light and radial velocity observations of bright classical cepheids over time. The older photometry and spectroscopy are combined with recent observations to determine possible changes in the pulsation period, mean brightness, and light and radial velocity amplitudes with time. In many cases over 100 yrs. years of observations have been collected and analyzed in a uniform way. The cepheids selected for the initial study are those that are already known to have significant period changes. The program stars include SV Vul, Polaris (alpha UMi), SZ Tau, S Vul, and X Cyg as well as several other stars. For example, Polaris has undergone a decrease in its light and radial velocity amplitudes during the last century as well as showing an increase in its pulsation period of dP/dt = +3.2 sec/yr. Studies of 19th and 20th century photometry also indicate that Polaris has increased in brightness from about mv = +2.2 mag to +2.0 mag over the last 150 yrs. Another interesting star in the program is the (P = 45d) classical cepheid SV Vul, which has been found to have a very rapid decrease of its pulsation period of dP/dt = -214 sec/yr. (e.g. see Turner and Berdnikov 2004; A&A 423,335). Photometric studies over the last 100 yrs (including our uvby photometry made in 2004) show that the light amplitude of SV Vul undergoes large changes. For example, the (yellow) light amplitude of SV Vul varies from about 0.8-1.2 mag (visual) between 1910-2004.
A study of the changes of the light and radial velocity curves as well as the pulsation periods for these stars provide important clues on what may be discernable evolutionary changes for classical cepheids. The period changes are especially sensitive to variations in the internal structure of the stars from evolutionary effects. The results for these and other stars will be discussed.
This research is supported by NSF/RUI (AST00-71260) to Villanova University that we gratefully acknowledge.
Engle Scott G.
Guinan Edward F.
Kim Chung Wook
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