Astrophysical Applications of Delta Scuti Stars

Abstract

The δ Scuti stars pulsate with a large number of low-order radial and nonradial p-modes. There also exists some evidence for the presence of g-modes.The pulsational variability outside the classical δ Scuti star instability strip (A1V - F0V on the main sequence) is examined. New measurements do not confirm the short-period variability of the hot B9p star ET And. However, a number of cool, early-F stars shows variability around one day: the γ Dor variables. An explanation involving nonradial g modes appears the most promising.An examination of available information on the multi-periodicity of δ Scuti stars shows no systematic behaviour in which pulsation modes axe excited to an observable level with luminosity and temperature. The asteroseismological potential of δ Scuti vaxiables is briefly examined.So far, the period changes of five luminous Pop. I δ Scuti variables have been studied. While stellar evolution predicts period increases, decreases have been observed and reported for all five stars. The statistical significance of this result and alternative explanations axe briefly examined.

A revised catalogue of δ Sct stars

“…A number of reviews on δ Sct variables are available in the literature, e.g. Breger (1979Breger ( , 1995Breger ( , 1999Breger ( , 2000, Eggen (1979), Wolff (1983), Tsvetkov (1990), López de Coca et al (1990), Send offprint requests to: E. Rodríguez, e-mail: eloy@iaa.es Tables 1 and 2 will be accessible only in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.ustrasbg.fr/Abstract.html Kurtz (1994Kurtz ( , 1996, Rodríguez et al (1994;hereafter R94), García et al (1995), Garrido (2000), Jiang et al (2000).…”

A Photometric Study of ZZ Microscopium

“…The surface-gravity value of 3.94 is almost identical with the value one can estimate from the (log g, log P 0 ) diagram for dwarf Cepheids by Andreasen (1983, hereafter A83). The surface gravities for dwarf Cepheids are expected to be estimated by about 0.1 in log g. The calibration of log g from uvbyβ photometry was based upon standard stars (ordinary rotational velocity), while the dwarf Cepheids are slow rotators (McNamara & Feltz 1978, hereafter MF;Breger 1980;A83), and therefore the log g value needs to be corrected. The corrected value of 3.84 is not in agreement with either 4.1 or 4.0 for Population I and extreme Population II stars from the theoretical period-gravity relation for dwarf Cepheids by A83.…”

“…We utilized the evolutionary tracks of Schaller et al (1992). The dashed lines are the blue and red edges of the instability strip as defined by Breger (1995).…”