The Spectrum of HD 965: Evidence for Anomalous Ionization

Details The Spectrum of HD 965: Evidence for Anomalous Ionization The Spectrum of HD 965: Evidence for Anomalous Ionization

Dec 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aas...203.9301b&link_type=abstract

American Astronomical Society Meeting 203, #93.01; Bulletin of the American Astronomical Society, Vol. 35, p.1357

Astronomy and Astrophysics

Astronomy

2

Scientific paper

Mathys, et al. (AAS, 123, 353, 1997) described the magnetically-resolved lines of the Ap star HD 965 discovered in 1993. The spectral classification for this object is Ap SrCrEu, the same designation given to the better-known Ap stars 53 Cam, 78 Vir, 73 Dra, HR 1217, and HR 4816. Of these stars, only HR 1217 is known to be a rapidly oscillating, or roAp star. The roAp stars fulfill the long-sought expectation of atmospheric abnormalities that might arise in photospheres where the magnetic energy density exceeds the thermal. Ionization anomalies are found in the lanthanide rare-earths in several roAp stars (Ryabchikova, et al. Astron. Reports, 45, 382, 2001), and the Balmer lines show a core-wing anomaly (CWA; Cowley, et al. A&A, 367, 939, 2001). HD 965 shows a CWA, but Kurtz, et al. (A&A, 398, 1117, 2003) report a null result for rapid oscillations in this star. In the present work, we show that ionization disequilibrium probably exists in HD 965 for Fe I and Fe II, as well as for Cr I and II, and Si I and II. These spectra give similar abundances only for models with effective temperatures of 8000 to 8200 K and log(g) = 3.0. These temperatures are considerably higher than the 7300-7500 K range inferred from reddening-corrected Geneva photometry. If the temperature is as high as would be necessary for iron equilibrium, the resulting iron abundance could be among the largest yet found for the Ap stars. Additional contrasts between the spectrum of HD 965 and its cool cogeners, including the observation that it may exhibit the richest set of Ce II features of any star known, will be presented.

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