Abundance analysis of roAp stars
III. Equulei *
T.A. Ryabchikova 1,
S.J. Adelman 2, 3,
W.W. Weiss 4 and
R. Kuschnig 4
Received 7 October 1996 / Accepted 18 November 1996
A spectroscopic analysis of the rapidly oscillating chemically peculiar star Equ yields = 7700 K, = 4.20, a microturbulence and which cannot be determined reliably, but which must be close to zero, because line broadening can be modelled by magnetic field effects alone. A mean magnetic field modulus of B = 4.0 kG is estimated by comparing synthetic Zeeman pattern with observations. This value provides another phase point for magnetic field variations of Equ, a CP2 star with the longest hitherto known magnetic field period of about 77 years. For a simple dipolar field geometry, the angle between the line of sight and the magnetic axis .
We discuss in some detail the problems for abundance determinations in the presence of a strong magnetic field and we increase substantially the number of ions to 42, for which abundances are now available. In particular, we obtain a more reliable abundance of = -10.24, and find Fe and the light elements, C to Ca, to have nearly solar abundances. Co is clearly overabundant, and Nb and Mo are the most overabundant elements in Equ relative to the Sun.
Key words: stars: abundances; chemically peculiar; magnetic field; oscillations; individual (fl Equ)
* Based on observations obtained at the European Southern Observatory (La Silla, Chile), Dominion Astrophysical Observatory, Observatoire de Haute-Provence, and at the Crimean Astrophysical Observatory
Send offprint requests to: Werner W. Weiss
© European Southern Observatory (ESO) 1997
Online publication: June 30, 1998