2 Goals and observing procedure

We have selected a subsample of late-type stars from the ESA Hipparcos catalog (ESA [1997]) in the brightness range $7\hbox{$.\!\!^{\rm m}$ }0-9\hbox{$.\!\!^{\rm m}$ }5$ and declination $-30^\circ$ through +70$^\circ$. B-V colors between 0.67 and 1.0 for stars with parallaxes $\pi>20$ milli-arcsec (i.e. G5-K3 dwarfs) and between 0.87 and 1.2 for $3<\pi<20$ milli-arcsec (i.e. G5-K2 giants and subgiants) select the range of stars with convective envelopes and thus likely magnetic activity. Out of this sample of 6440 stars, 460 were observed in September 1998 in the right-ascension range 18$^{\rm h}$-6$^{\rm h}$, and 598 in February 1999 in the right-ascension range 6$^{\rm h}$-18$^{\rm h}$. Generelly, we excluded stars that already had a published moderate-to-high resolution Ca II spectrum but in some interesting cases we reobserved them. Previously known H&K emission-line stars came mostly from the following sources: the original Wilson sample of photographic-plate spectra (e.g. Wilson [1976]), the spectrophotometric Mt. Wilson H&K survey (e.g. Duncan et al. [1991]), Bidelman's catalogue and bibliography of emission-line stars of types later than B (Bidelman [1954]), the Michigan-University southern and northern sky objective-prism survey (Bidelman & MacConnell [1973]; Bidelman [1981], [1983], [1985], [1988]), the lists of Fekel and collaborators (e.g. Fekel et al. [1986]), the CDS data base collected by Lastennet & Freire Ferrero ([1994]), and our own Ca II data of active stars (Strassmeier et al. [1990], [1993]; Strassmeier [1994]).

Our observing procedure was as follows. After H&K emission was detected from a short-exposure spectrum centered near 4000 Å, we reobserved the star at red wavelengths. These spectra include the H$\alpha$ line and the lithium line at 6707 Å and are used to determine their respective line properties and a more precise value for the rotational broadening as is possible from the blue spectra. The additional radial velocity from the red spectrum may also indicate whether the star is an unknown spectroscopic binary. It is also of higher precision due to lesser line blending in the red. If the star had H&K emission, we added it to the observing menu of one of our two automatic photoelectric telescopes (APTs) in southern Arizona. These data are used to search for light variations and to determine a photometric period that is then assumed to be the stellar rotation period. Figure 1 shows the sky coverage and galactic distribution of all target stars observed. Large dots denote the stars that were found to exhibit H&K emission, small dots those without emission. Figure 2 plots the distribution of stellar parameters within the entire sample. V magnitudes and B-V colors were taken from the Tycho catalog and trigonometric parallaxes from the Hipparcos catalog (ESA [1997]). The effective temperatures are based on the B-V calibration from Flower ([1996]). Table A1 lists the stars with H&K emission, Table A2 those without emission. Both tables are available only in electronic form.