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Preprint I/03

Feige 48: A model match for the coolest pulsating subdwarf B star

Reed M.D. (1), Kawaler S.D. (2), Zola S. (3), Jiang X.J. (4), The Whole Earth Telescope Xcov17, Xcov 19, Xcov21 teams (5)

(1) Department of Physics, Astronomy and Material Science, SW Missouri State University, 901 S. National Springfield, MO 65804 USA
(2) Department of Physics & Astronomy, Iowa State University, Ames, IA 50011 USA
(3) Astronomical Observatory, Jagiellonian University, ul. Orla 171, PL-30-244 Kracow, Poland, and Mt. Suhora Observatory of the Pedagogical University, ul. Podchorcazych 2, PL-30-084 Kracow, Poland
(4) National Astronomical Observatories and Joint Laboratory of Optical Astronomy, Chinese Academy of Sciences, Beijing, 100012, China
(5) Complete list available at http://wet.iitap.iastate.edu

In: Proc. XIII Workshop on White Dwarfs, Kluwer Academics NATO Science Series, eds. D. de Martino, R. Kalytis, R. Silvotti, J.E. Solheim, 105, 81

Abstract. Feige 48 was identified as a "faint blue star" as part of the Feige survey (Feige, 1958). It was re-categoized as an sdB star when it was observed as part of the Palomar-Green survey (Green, Schmidt, & Liebert, 1984). Heber, Reid, & Werner (2000) obtained a high-resolution (0.09A) spectrum of Feige 48 and determined log g=5.5+-0.05 and Teff=29500+-300K. This makes Feige 48 the coolest sdBV known to date with a surface gravity intermediate between PG1605+072 and the rest of the EC 14026 class. Koen et al. (1998) identified five pulsation periods in Feige 48 in six observing runs from May, 1997 to Febraury 1998. The periods range from 342 to 379 seconds with the largest amplitude being 6.4mmag. Amplitude variability led Koen et al. (1998) to conclude that mode beating was liekly present. This implied that other unresolved modes were present in their data and provided the motivation for our follow-up observations.
Our observations of Feige 48 began in November 1998, with our most recent observations acquired in April. 2002. We obtained a total of 340 hours of data in our four season program. Including the 30 hours of data from Koen et al. (1998) we have data from January, 1998 to April, 2002.

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