Surface features of the lower atmosphere of HD 82558(= LQ Hydrae)

Details Surface features of the lower atmosphere of HD 82558(= LQ Hydrae) Surface features of the lower atmosphere of HD 82558(= LQ Hydrae)

Feb 1993

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...268..671s&link_type=abstract

Astronomy and Astrophysics (ISSN 0004-6361), vol. 268, no. 2, p. 671-684.

Astronomy and Astrophysics

Astrophysics

59

Early Stars, K Stars, Stellar Atmospheres, Stellar Spectrophotometry, Charge Coupled Devices, Chromosphere, H Alpha Line, Light Curve, Starspots, Ubv Spectra

Scientific paper

We present simultaneous high-resolution CCD spectra and UBVRI photometry of the very active young single K2 dwarf star LQ Hya. The star displays extreme chromospheric activity as well as having a large and variable spot distribution. We applied the Doppler-imaging technique to nine different photospheric absorption lines of various strengths. By averaging all individual maps together spurious surface features from one spectral line are suppressed in the final map and only consistent features show up. This greatly enhances the reliability of our Doppler image of LQ Hya. Individual images obtained from the weak line profiles together with the photometry yielded mainly low-latitude surface features. The strongest lines together with photometry yielded large features at the rotation pole. The surface temperature range is only a few hundred degrees. Four starspot regions were detected from Doppler imaging. Extended regions of lesser temperature depression are also evident. Additionally we found rotational modulation of certain temperature-sensitive line ratios in agreement with simultaneous NIR continuum photometry, verifying the 'cool' nature of the starspots on LQ Hya. Chromospheric parameters were computed from H-alpha as a function of rotational phase. We present evidence that lower electron densities occur at times when a cool starspot is in view, indicating a less dense chromosphere above a spotted region.

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