Site Map
Contacts
Follow us on Facebook Follow us on Twitter YouTube channel
Centro de Astrofísica da Universidade do Porto

The fundamental parameters of the roAp star α Circini

H. Bruntt, J. R. North, M. S. Cunha, I. M. Brandão, V. G. Elkin, D. W. Kurtz, C. J. Davis, T. R. Bedding, A. Jacob, S. M. Owens, J. G. Robertson, W. J. Tango, J. F. Gameiro, M. J. Ireland, P. G. Tuthill

Abstract
We have used the Sydney University Stellar Interferometer (SUSI) to measure the angular diameter of alpha Cir. This is the first detailed interferometric study of a rapidly oscillating A (roAp) star, alphaCir being the brightest member of its class.We used the new and more accurate Hipparcos parallax to determine the radius to be 1.967 ± 0.066R⊙. We have constrained the bolometric flux from calibrated spectra to determine an effective temperature of 7420±170K. 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.

Monthly Notices of the Royal Astronomical Society
Volume 386, Page 2039
June 2008

>> ADS>> DOI

Institute of Astrophysics and Space Sciences

Institute of Astrophysics and Space Sciences (IA) is a new but long anticipated research infrastructure with a national dimension. It embodies a bold but feasible vision for the development of Astronomy, Astrophysics and Space Sciences in Portugal, taking full advantage and fully realizing the potential created by the national membership of the European Space Agency (ESA) and the European Southern Observatory (ESO). IA resulted from the merging the two most prominent research units in the field in Portugal: the Centre for Astrophysics of the University of Porto (CAUP) and the Center for Astronomy and Astrophysics of the University of Lisbon (CAAUL). It currently hosts more than two-thirds of all active researchers working in Space Sciences in Portugal, and is responsible for an even greater fraction of the national productivity in international ISI journals in the area of Space Sciences. This is the scientific area with the highest relative impact factor (1.65 times above the international average) and the field with the highest average number of citations per article for Portugal.

Proceed on CAUP's website|Go to IA website