The Vienna-KPNO search for Doppler-imaging candidate stars^*

I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars

Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, A-1180 Wien, Austria e-mail: name@astro.univie.ac.at

Received: 2 November 1999
Accepted: 22 December 1999

Abstract

We present the results from a spectroscopic Ca ii H&K survey of 1058 late-type stars selected from a color-limited subsample of the Hipparcos catalog. Out of these 1058 stars, 371 stars were found to show significant H&K emission, most of them previously unknown; 23% with strong emission, 36% with moderate emission, and 41% with weak emission. These spectra are used to determine absolute H&K emission-line fluxes, radial velocities, and equivalent widths of the luminosity-sensitive Sr ii line at 4077 Å. Red-wavelength spectroscopic and Strömgren y photometric follow-up observations of the 371 stars with H&K emission are used to additionally determine the absolute Hα-core flux, the lithium abundance from the Li i 6708 Åequivalent width, the rotational velocity , the radial velocity, and the light variations and its periodicity. The latter is interpreted as the stellar rotation period due to an inhomogeneous surface brightness distribution. 156 stars were found with photometric periods between 0.29 and 64 days, 11 additional systems showed quasi-periodic variations possibly in excess of ≈50 days. Further 54 stars had variations but no unique period was found, and four stars were essentially constant. Altogether, 170 new variable stars were discovered. Additionally, we found 17 new SB1 (plus 16 new candidates) and 19 new SB2 systems, as well as one definite and two possible new SB3 systems. Finally, we present a list of 21 stars that we think are most suitable candidates for a detailed study with the Doppler-imaging technique.