Chromospheric features of LQ Hydrae from Hα line profiles

¹ INAF - Catania Astrophysical Observatory, via S. Sofia 78, 95123 Catania, Italy e-mail: [antonio.frasca;katia.biazzo]@oact.inaf.it
² Konkoly Observatory, 1525 Budapest, PO Box 67, Hungary e-mail: kovari@konkoly.hu
³ Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany e-mail: kstrassmeier@aip.de

Received: 13 November 2007
Accepted: 3 January 2008

Abstract

We analyze the Hα spectral variability of the rapidly-rotating K1-dwarf LQ Hya using high-resolution Hα spectra recorded during April-May 2000. Chromospheric parameters were computed from the Hα profile as a function of rotational phase. We find that all these parameters vary in phase, with a higher chromospheric electron density coinciding with the maximum Hα emission. We find a clear rotational modulation of the Hα emission that is better emphasized by subtracting a reference photospheric template built up with a spectrum of a non-active star of the same spectral type. A geometrical plage model applied to the Hα variation curve allows us to derive the location of the active regions that come out to be close in longitude to the most pronounced photospheric spots found with Doppler imaging applied to the photospheric lines in the same spectra. Our analysis suggests that the Hα features observed in LQ Hya in 2000 are a scaled-up version of the solar plages as regards dimensions and/or flux contrast. No clear indication of chromospheric mass motions emerges.