A spectroscopic analysis of the chemically peculiar star HD207561

Abstract

In this paper we present a high-resolution spectroscopic analysis of the chemically peculiar star HD207561. During a survey programme to search for new rapidly oscillating Ap (roAp) stars in the Northern hemisphere, Joshi et al. observed significant photometric variability on two consecutive nights in the year 2000. The amplitude spectra of the light curves obtained on these two nights showed oscillations with a frequency of 2.79 mHz(P∼6 min). However, subsequent follow-up observations could not confirm any rapid variability. In order to determine the spectroscopic nature of HD207561, high-resolution spectroscopic and spectropolarimetric observations were carried out. A reasonable fit of the calculated Hβ line profile to the observed one yields an effective temperature (Teff ) and surface gravity (log g) of 7300K and 3.7 dex, respectively. The derived projected rotational velocity (v sin i) for HD207561 is 74 km per second, indicative of a relatively fast rotator. The position of HD207561 in the Hertzsprung–Russell diagram implies that this is slightly evolved from the main-sequence and located well within the δ-Scuti instability strip. The abundance analysis indicates the star has slight underabundances of Ca and Sc and mild overabundances of iron-peak elements. The spectropolarimetric study of HD207561 shows that the effective magnetic field is within the observational error of 100 G. The spectroscopic analysis revealed that the star has most of the characteristics similar to an Am star, rather than an Ap star, and that it lies in the δ-Scuti instability strip; hence roAp pulsations are not expected in HD207561, but low-overtone modes might be excited.