Photometric and TiO modelling of the starspots on AG Dor and HU Vir

¹ Instituto de Astrofísica de Andalucía-CSIC, Apartado 3004, 18080 Granada, Spain
² Astronomical Institute, Tatranská Lomnica, 059 60, Slovakia

Corresponding author: P. J. Amado, pja@iaa.es

Received: 2 May 2001
Accepted: 19 October 2001

Abstract

In this work, spot parameters are determined for two stars, namely, AG Dor and HU Vir, from their photometric variability and λ7055 Å TiO band depth. Applying the photometric modelling code spotpic, we have found two modulating spots together with a non-modulating component on the photosphere of AG Dor in December 96/January 97. The spot temperatures are constrained to be between 4300 K and 4600 K for the modulating component, and cooler, viz., 4000 K, for the non-modulating one. Therefore, the non-modulating component of the spot distribution on AG Dor at this epoch is held to be totally responsible for the presence of the TiO band in the spectra of this K1 dwarf with photospheric temperature of 5000 K. AG Dor's total coverage of spots is determined to be between 4% and 7% for the modulating component and 26.5% for the non-modulating one. For HU Vir, the light and colour curves were modelled with two spots with temperatures of 4450 and 4050 K. In this case we did not include the non-modulating component in the model.