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Analyses of the Short-Period Cepheid SU Cassiopeiae
Baade-Wesselink analyses of this important Galactic classical Cepheidprovide new values for the radius, luminosity, distance, and mass andshow SU Cas likely to be pulsating in the first overtone. Application ofa modified Baade-Wesselink technique and the maximum likelihood method,which we have previously applied to δ Scuti-type variables, yieldvalues of R=33.0+/-1.1 Rsolar, L=1536+/-291Lsolar, MV=-3.28-0.19+0.23, r=486+/-52 pc,mass (from the Baade-Wesselink radius), M=6.5+/-0.6 Msolar(assuming first-overtone pulsation), and evolutionary mass,Mev=5.5+/-0.3 Msolar. The results are consistentwith the Hipparcos satellite parallax, 2.31+/-0.58 mas(433+145-87 pc), providing further support forovertone pulsation of SU Cas. In the course of the analyses, amodification to the maximum likelihood method, devised by one of us (W.J. F. W.), is presented as an alternative to the modifications of Laney& Stobie and Coulson, Caldwell, & Gieren. We dedicate this paper toAdriaan J. Wesselink, a dedicated scientist and teacher, and inventor of``the method.''
| Estimation of spectral classifications for bright northern stars with interesting Stromgren indices
The purpose of this investigation is to provide spectroscopic observerswith finding lists of potentially interesting objects. From anunpublished UVBY catalogue of 7026 northern stars (mostly brighter than8.3m) 1094 objects with interesting combinations of UVBY indices havebeen selected. Most stars with post-HD classifications have beenexcluded, as well as late F dwarfs belonging to the intermediatepopulation II. For the 792 remaining stars estimated spectralclassifications are given. The techniques and experience from a previouspaper dealing with southern stars have been utilized here. Among thepredicted spectral classifications are 40 OB stars; 262 Ap, Am, or Fmstars; 16 supergiants of types A to G; 110 bright giants of types A to K(class II); 156 double stars or objects with composite spectra; 26 lateF dwarfs; 91 weak-lined dwarf and giant stars of types F to K, includingearly F-type population II field blue stragglers; and a few possiblefield horizontal branch stars, lambda Bootis-type stars, and late-typehalo giants.
| An investigation of radius anomalies among short-period Cepheids
Simultaneous photometric and spectroscopic observations have beenobtained of two short-period Cepheids, SU Cas and TU Cas. The Wesselinkmethod of Barnes et al. was used to obtain radii. The radii are found toagree, within the expected error, with evolutionary values. Thisstrengthens the argument that the beat Cepheids are normal Cepheids inmixed-mode behavior rather than a separate class of objects and thatevolutionary masses and radii are correct.
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