The fundamental parameters of the roAp star alpha Circini

• Type: Article in International Scientific Journal
• Date: 2008

Authors

Bruntt, H (Author) Other; North, JR (Author) Other; Cunha, M (Author) FCUP; Brandao, IM (Author) Other; Elkin, VG (Author) Other; Kurtz, DW (Author) Other; Davis, J (Author) Other; Bedding, TR (Author) Other; Jacob, AP (Author) Other; Owens, SM (Author) Other; Robertson, JG (Author) Other; Tango, WJ (Author) Other; Gameiro, JF (Author) FCUP; Ireland, MJ (Author) Other; Tuthill, PG (Author) Other

Journal

Title: Monthly Notices of the Royal Astronomical Society

Vol. 386

Pages: 2039-2046

ISSN: 0035-8711

Publisher: Oxford University Press

Indexing

ISI Web of Knowledge - 40 Citations

Scopus - 39 Citations

Scientific classification

FOS: Natural sciences > Physical sciences

Other information

Authenticus ID: P-003-Z4F

DOI: 10.1111/j.1365-2966.2008.13167.x

Abstract (EN): We have used the Sydney University Stellar Interferometer to measure the angular diameter of alpha Cir. This is the first detailed interferometric study of a rapidly oscillating A (roAp) star, alpha Cir being the brightest member of its class. We used the new and more accurate Hipparcos parallax to determine the radius to be 1.967 +/- 0.066 R(circle dot). We have constrained the bolometric flux from calibrated spectra to determine an effective temperature of 7420 +/- 170 K. This is the first direct determination of the temperature of an roAp star. Our temperature is at the low end of previous estimates, which span over 1000 K and were based on either photometric indices or spectroscopic methods. In addition, we have analysed two high-quality spectra of alpha Cir, obtained at different rotational phases and we find evidence for the presence of spots. In both spectra we find nearly solar abundances of C, O, Si, Ca and Fe, high abundance of Cr and Mn, while Co, Y, Nd and Eu are overabundant by about 1 dex. The results reported here provide important observational constraints for future studies of the atmospheric structure and pulsation of alpha Cir.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 8