4 Discussion of individual stars

We discuss now the results for the individual stars. Our classification work has greatly benefited from the data collected by the HIPPARCOSsatellite and presented by Perryman et al. (1997). In particular, for all stars the trigonometric parallax was often a key parameter for choosing between possible spectral classifications. Moreover, the magnitude difference between the components was very useful when studying visual binaries. Finally, the data from the variability annex to the HIPPARCOScatalogue (Perryman et al. 1997) were used for studying some of the variable stars.

HD2133: Burleigh et al. (1997) classified this binary system as F9V + WD. However, our colors and HIPPARCOSdistance are better matched by assuming a slightly evolved primary star. The constant RV indicates that the primary component is single.

HD 6628 = CS Cet: the colors are better matched by a binary system, in agreement with the HIPPARCOSdistance. We have indication of binary nature also from the RVs deduced by two high resolution spectra separated by three days. Only one system of lines is visible. The star is given as a suspected RS CVn by McGale et al. (1995). Optical variability was clearly detected, but the period appears to be longer than the observing window, in agreement with the v$\sin$i and the luminosity class IV classification of the primary component. A flare event was detected at HJD = 2449316.6145.

HD8357 = AR Psc: a well-known RS CVn-type variable, see Fekel (1996) and Cutispoto (1998) for the spectral classification. Our RV data are in agreement with the RV curve of Fekel (1996). We have no indication of SB2 nature.

HD8358 = BI Cet: a well-known RS CVn-type variable with similar components, both very fast rotators (Bopp et al. 1985). Due to the very high rotation rate the spectrum is difficult to interpret. However, we clearly detect the two Ca I 6717.7 Å lines.

HD9770 = BB Scl: a visual triple system. Components A and B are separated by 0.16 arcsec. Component C is 0.21 arcsec apart. Component B is also an eclipsing binary and is the most likely counterpart of the X-ray and EUV source (Cutispoto et al. 1997a). Due to its very fast rotation component B produces only clear depressions of the continuum in correspondence of the most prominent lines. The sharp lines that we see in our spectra are due to the single brighter A component. The spectral types of the A (K0/1V) and B (K3V + K3/4V) components, reported in Table 1, are slightly revised with respect to the classification given in Cutispoto et al. (1997a).

HD16699: at this position the SIMBAD database lists three stars separated by about 1.5 and 8.7 arcsec, with spectral type F8IV/V, K and K5, respectively. The first two are components A and B of HD16699, the third is SAO232842. We obtained combined optical photometry for HD16699AB + SAO232842 and separate spectra for HD16699 AB and SAO232842. The spectral types that better reproduce the observed colors, the distance and the $\Delta V$=0.57 magnitude difference between HD16699AB and SAO232842 reported by HIPPARCOSare F9V + K0:V and G1/2V for HD16699AB and SAO232842, respectively. In the spectrum of HD16699 AB we clearly see a system of sharp lines that we attribute to component A, with a superimposed broader system of lines that we attributed to component B. Constant RV indicates that HD16699AB is not a close binary. Also the RV of SAO 232842, for which we also measured a v$\sin$i of 21$\pm$2 kms^-1, is constant. The colors of HD16699AB are also consistent with the classification G2/3V + G2/3V, that implies a distance of 62 pc. However, this is not consistent with the spectral signatures.

HD 18131: Burleigh et al. (1997) and Vennes et al. (1998) classified this binary system as K0IV + WD, in good agreement with our results. However, the K star does not have indication of strong activity (see also Osten & Saar 1998). Therefore, the X-ray and EUV emission is most likely to be due to the WD. The RV measurements indicate that the system is not a close binary. The photometric distance results within the 92-120pc range measured by HIPPARCOS.

HD24916: a visual binary whose components are separated by 11.1 arcsec. The inferred spectral types are those that better fit the colors, the distance and the magnitude difference ($\Delta V$$\sim$3.2) between the two components. The K4/5V star shows no indications of activity, therefore the X-ray and EUV emissions are assigned to the active M2Ve stars (see also Hodgkin & Pye 1994). The RV and v$\sin$i data refer to the K4/5V component.

HD25457: a high proper motion star. The colors (Bessel 1990) and the HIPPARCOSdistance better agrees with an F5/6V spectral classification. Our RV measurements seem to give a constant value and also the CORAVEL data (Duquennoy & Mayor 1991) were not able to ascertain clear variability.

HD32008: a binary system including a WD. Landsman et al. (1993) and Vennes et al. (1998) classified the primary as a K0IV and a G5IV star, respectively. However, both the colors reported in the literature and the HIPPARCOS distance are in better agreement with a G7IV/III classification. The primary star does not show indications of activity, therefore, the X-ray and EUV emissions are most likely to be due to the WD companion (see also Barstow et al. 1994). The RV data indicate that this system is not a close binary.

HD33262: can be classified as an F7V star from the observed colors (Bessel 1990). The photometric distance is not in full agreement with the HIPPARCOSdata. A metallicity value [Fe/H] = -0.23 was obtained by Cayrel de Strobel et al. (1992).

HD35114: a very fast rotator for which we detected optical variability (Fig. 2). The period search analysis gives four possible values (i.e. 2.26 $\pm$ 0.04, 1.80 $\pm$ 0.02, 1.375 $\pm$ 0.015 and 0.690 $\pm$ 0.004 days). However, due to the very high v$\sin$i only the shortest of them yields a steller radius that is compatible with the inferred spectral type. The photometric distance is somewhat larger than the value measured by HIPPARCOS.

HD36869: we discovered optical variability (Fig. 3) with a period of 1.31$\pm$0.01days. The trigonometric parallax is from the Tycho catalogue. The distance, computed from the listed error, results in the 28-46pc range.

HD37572 = UY Pic: optical variability with a 4.52 day photometric period was reported in the SAAO Annual Report (1993) and is confirmed by us (Fig. 4). Soderblom et al. (1998) classified this star as ZAMS or younger. They obtained a v$\sin$i and an RV that are both consistent with our values. HD37572 is also a visual binary. The secondary component, SAO 217429, that lies about 18.3 arcsec apart, is not included in the photometry. From the magnitude difference measured by HIPPARCOS($\Delta V$$\sim$1.9) we infer a K6:V spectral type for SAO 217429.

HD41824: a close visual binary, with an angular separation of about 2.59 arcsec (Horch et al. 1997), whose primary component is a spectroscopic binary (Andersen et al. 1985), as confirmed by our RV measurements. We computed the spectral type of both the spectroscopic companion (K7:V) and the visual companion (G6V). The solution listed in Table 1 is the one that better fits simultaneously the distance and the magnitude difference ($\Delta V$$\sim$0.36) measured by HIPPARCOS, the observed colors and the spectral signatures. Our photometric observations (Fig. 5) also revealed low amplitude optical variability with a period of 3.3$\pm$0.1 days.

HD43162: low amplitude optical variability with a period of 7.2$\pm$0.2 days was detected by us (Fig. 6). Our RV measurements are in good agreement with those of Beavers & Eitter (1986) and Andersen et al. (1985) and indicate, within the errors, that the star is indeed single.

HD43989 = V1538 Ori: a variable star discovered by Cutispoto et al. (1995) that computed a photometric period of 3.63 days. However, such a period would imply a minimum radius of the order of 3.4$R_{\odot}$, that is not consistent with the luminosity class V ensured by the HIPPARCOSdistance. Hence, we performed a new period search and found that a period of 1.15$\pm$0.01 days fits equally well (Fig. 7) the data collected by Cutispoto et al. (1995). This shorter period yields a minimum radius that is consistent with an F9V star seen at an inclination of about 75 degrees. Our RV data show that the star is single. Osten & Saar (1998) inferred the two possible spectral classifications G0IV + G0IV and G0IV, however, from the above results, none of them can be accepted.

HD45081 = AO Men: was detected as un unsolved variable (i.e. a variable whose period has not been determined) by the HIPPARCOSsatellite. Our observations (Fig. 8) are consistent with a 2.65$\pm$0.04 day period. The photometric distance is smaller than the trigonometric one. This could be due to the fact that the star is probably a PMS object, as indicated by the inferred 0.9$R_{\odot}$ minimum radius. In fact, a K5V star should have a radius of the order of 0.68$R_{\odot}$. Actually, the period search analysis gives also a less significative peak corresponding to a photometric period of 0.722$\pm$0.003 days. However, by using this shorter period the inclination would result in 21 degrees, a value that seems too small to account for the rather large amplitude of the light curve we observed.

HD48189: a visual binary, whose components are separated by 0.76 arcsec, that are listed as a young, possibly PMS, star by Sterzik & Schmitt (1997). Schachter et al. (1996) and Jeffries & Jewell (1993) report the spectral types G0V + G8V and G0V + K3V, respectively. Our classification is in very good agreement with the latter and also fits the magnitude difference between the two components ($\Delta V$$\sim$2.3) measured by HIPPARCOS. We note that our data are not consistent with a PMS classification, as also noted by Micela et al. (1997). Both Andersen et al. (1985) and our RV data confirm that the primary G0V component is single. However, there is a difference between the mean values of the two RV data sets, that we think is due to the long-term effect due to the distant K2/3V secondary component. Finally, low amplitude light variability (Fig. 9) with a period of 2.60$\pm$0.04 days was detected.

HD71285: has an high rotation rate and is an SB system, as shown by our RV measurement. From the colors and the HIPPARCOSdistance we infer a G1V + G3V classification. Optical variability (Fig. 10) with a period of 1.35$\pm$0.01 days was discovered. Although the period search analysis gives also periods of 1.83 and 3.65 days, these longer values are non consistent with a dwarf classification and, hence, with the distance.

HD75997: has a very fast rotation rate, as confirmed also by our photometric data (Fig. 11) that revealed optical variability with a period of 0.4085$\pm$0.0011 days. The trigonometric parallax from HIPPARCOShas a large error, falling in the 22-55pc range.

HD78644: is an SB1 system, as revealed by our RV measurements, and has a very high rotation rate. Optical variability (Fig. 12) with a photometric period of 0.840$\pm$0.004 days was discovered. The inclination angle results of the order of 82 degrees and, in fact, the photometric data suggest the presence of an eclipse. Actually, the period search analysis gives also the photometric period of 0.551$\pm$0.002 days, but such shorter period would led to an inclination of about 40 degrees, making quite difficult to explain the shape of the light curve.

HD82159: is a fast rotator and, as inferred by our RV measurements, is an SB1 system. The HIPPARCOSdistance has a quite large error, falling into the 37 - 65 pc range. We have not performed photometric observations of this star, however, from the spectral characteristics and the B-V from the literature we infer a G9V + K4:V classification. There is a second star, SAO98614 (V=8.67), at about 13.9 arcsec, that has a v$\sin$i of 6 kms^-1. For this star we infer a K0:V spectral type. The resulting distance of 36 pc is in good agreement with the HIPPARCOSvalue, that falls into the 29-49pc range.

HD82558 = LQ Hya: a well-known very active rapidly rotating single star that has been classified as a very young star just arrived on the ZAMS, or even as a PMS object (see Cutispoto 1998 and references therein).

HD96064: a high proper-motion star that is also a triple visual system. Components B and C, which are 0.4 arcsec apart, lay 11.5 arcsec aside component A. We observed component A, which is an active G8V star showing low amplitude optical variability with a period of 6.9$\pm$0.3 days (Fig. 13). Components B (K9:V) and C (K7:V) constitute a very close pair of late type stars, whose spectral types were inferred from the magnitude difference with respect to component A reported by HIPPARCOS.

HD118100 = EQ Vir: a well-known flare star.

HD124672: we find it to be a short period variable star with a photometric period of 0.646$\pm$0.003 days (Fig. 14). The best fit of the colors is obtained by assuming an F5V + K4:V system, however, the spectral lines are too broad to give any further indication on the secondary component, whose spectral type is very uncertain.

HD140637 = KW Lup: a WTTS star and also a visual binary with a separation of 0.67 arcsec and a very faint companion (Brandner et al. 1996). It was classified as a 11Myr star with a mass of 1$M_\odot$ by Neuhäuser & Brandner (1998). Our photometry confirms the PMS nature of this object. In fact, the colors are not consistent with any class V star with a B-V close to the value expected for a K3V and a V-I similar to the value expected for a K5V. Moreover, if we assume a main sequence star the distance would be smaller than the value reported by HIPPARCOS. HD 140637 is listed as a semi-regular variable with an amplitude of about 0.16 magnitudes in the HIPPARCOS variability annex. Our observations (Fig. 15) are consistent with a 2.72$\pm$0.05 day period. The RV is constant in three spectra taken in consecutive nights. This indicates that HD140637 is effectively single, the effects due to the optical companion being not detectable over a three night interval.

HD141943: two photometric periods are possible. The shorter one (1.30$\pm$0.01 days) implies a luminosity class V classification and a distance of 46 pc. The longer one (2.20$\pm$0.03 days, see Fig. 16) yields a larger radius, adequate for a PMS or an evolved object. Although further photometric observations are needed to ascertain the true rotational period we regard this star as a PMS, due to its high rotational rate and to the high Li abundance inferred by Tagliaferri et al. (1999).

HD143937 = V1044 Sco: a visual binary with an angular separation of 10.25 arcsec. We find that the brighter A component is an SB2 and Cutispoto (1999) discovered that it is also an eclipsing binary with an orbital period of about 0.91 days. Our photometric observations (Fig. 17) included both components of the visual binary. The fainter B component has a v$\sin$i of 12$\pm$3 kms^-1. The best fit of the observed colors, spectral characteristics and distance is obtained by assuming the eclipsing binary as a G9V + M0:V system and component B as a K7:V star. This is also in agreement with the $\Delta V$$\simeq$2.8 magnitude difference between A and B components measured by HIPPARCOS. The data reported in Tables 1 and 2 refer to the out-of-eclipse light curve. The star is also reported as an unsolved variable in the HIPPARCOSvariability annex.

HD156498 = V2369 Oph: a close visual pair ($\rho$=0.31 arcsec, $\Delta V$$\simeq$1.4) whose primary component is an SB1 binary (Jeffries et al. 1995), as also confirmed by our spectra. The spectral classification that is reported in Table 1 is the only one that reproduce the observed colors, the HIPPARCOSdistance and the magnitude difference between the components. HD156498 is listed in the HIPPARCOSvariability annex as an unsolved variable with an amplitude of 0.08 magnitudes. Our observations (Fig. 18) show that the optical variability is consistent with the 0.655-day orbital period given by Jeffries et al. (1995). The G8:V B component has a v$\sin$i of only 8$\pm$2 kms^-1.

HD171488 = V889 Her: was discovered to be a short period variable by Henry et al. (1995), who reported a photometric period of 1.338 days and an amplitude of about 0.1 magnitudes in the V-band. For this star we only get few and sparse photometric data. However, the colors and the spectral signatures are consistent with a G2V classification, that results in very good agreement with both the distance measured by HIPPARCOSand the classification inferred by Osten & Saar (1998). The RV is constant, in agreement with the results of Fekel (1997). From the strength of the Li line Mullis & Bopp (1994) estimated for HD 171488 an age similar to or younger than the Pleiades.

HD195434 = MR Del: a visual binary ($\rho$=1.80 arcsec, $\Delta V$$\simeq$0.28) whose primary component (K2V + K6V) is an eclipsing binary with an orbital period of 0.52175 days, as first observed by Cutispoto et al. (1997a). It is a high proper-motion very old star which is still very active because of its tidally locked high rotation rate. For a detailed study see Cutispoto et al. (1997a). Here we note that there is a typo in the spectral classification given in Table 1 of the above-mentioned paper. The correct classification is the one reported in Table 2 of the present paper. The star is also present in the HIPPARCOSvariability annex, where a period of 0.521690 days is listed.

HD197890 = BO Mic: with a photometric period of 0.380 days (see Cutispoto et al. 1997b and references therein) it is the most rapidly rotating nearby single late-type star known to date. The spectral classification from the colors is quite difficult, probably owing to the very high level of activity and/or to the fact that probably HD197890 has not arrived on the MS, yet. From the v$\sin$i=170 kms^-1 computed by Anders et al. (1993) and the photometric period, Cutispoto et al. (1997b) inferred a minimun radius in the 1.13 - 1.43$R_{\odot}$ range, thus supporting the hypothesis that HD 197890 is a PMS star, as also confirmed by the now available HIPPARCOSdistance. The photometric period reported in the HIPPARCOS variability annex is in full agreement with the value given by Cutispoto et al. (1997b). The equivalent width of the Ca I 6717.7 Å line suggests a spectral type K5, later than the K2/3 proposed by the photometry. However, the noise of the spectra and the very high v$\sin$i of the star make the measurement of the Ca I line very difficult and hence the EW of the line is probably overestimated.

HD199143: the classification from the observed colors and the spectral signatures result in good agreement with the distance measured by HIPPARCOS. Very low amplitude optical variability is possible.

HD217411: has a WD companion as reported by Barstow et al. (1994) and by Vennes et al. (1998). The primary component shows only moderate signs of activity. It is a slow rotator (see also Fekel 1997), has no Ca II emission and shows only a partially filled H$\alpha$ line (Mullis & Bopp 1994). We do not see indications of RV variability, in agreement with Fekel (1997), hence the system is a wide binary. However, it should be noted that for this star we observe an anomalous strength of the Ca I 6717.7Å line, that would be consistent with being the primary component of HD 217411 a G2/3V + K4V system. On the other hand this circumstance appears in contrast with the RV measurements.

HD222259 = DS Tuc: is a close visual binary ($\rho$=5.3 arcsec, $\Delta V$$\sim$1.3) that is reported as an unsolved variable with an amplitude of 0.12 magnitudes in the HIPPARCOSvariability annex. Our photometry, in which the two components were observed together, shows a much smaller amplitude light curve (Fig. 19) with a period of 1.54$\pm$0.02 days. This system was also studied by Soderblom et al. (1998).

HD223816: was classified as a G0V + WD system by Barstow et al. (1994). Our colors agree best with those of an F5V star. This earlier classification for the primary component implies for the WD a temperature lower than the value computed by Barstow et al. (1994). Similarly to our results, also Vennes et al. (1998) observed a constant RV on short time-scale. The difference among the two data sets could be due to the long-term variability caused by the presence of the WD. Finally, Craig et al. (1997) classified the WD as metal-rich and the primary component as F5IV. However, we note that the latter classification gives a worse fit of the observed color than the F5V one. The best fit of the colors by assuming a class IV star, still somewhat worse than the fit with the F5V, is obtained by a F6/7 IV, whose distance results in 195pc.

HD291095 = V1355 ori: was found to be a variable star by Cutispoto et al. (1995), who computed a photometric period of 3.82 days and inferred, from the observed colors, the two possible spectral classifications K2/3 V and K2 IV + G2 V. More recently, this star was studied by Osten & Saar (1998) who rule out the dwarf classification. Given the 23-133pc distance range measured by HIPPARCOS, we revise the spectral types listed by Cutispoto et al. (1995) to K1 V/IV (d=88 pc) and K2 V/IV + G8 V (d=100 pc), respectively. However, we note that also the combination K3 V/IV + G6 V (d=102 pc) fits the observed colors. The RV measurements indicate that the star is indeed a binary, thus, we prefer the latter spectral classification because it better agrees with the minimum radius inferred for the primary component.

BD-001712: is an SB2 with an orbital period of 1.4 days (Jeffries et al. 1995). Optical variability with a photometric period of 1.412 days is reported by Robb & Gladders (1996). For this star we only got few and sparse photometric data. However, the colors and the spectral signatures are in agreement with a K3V + M0:V classification. Ca II K and H$\alpha$emission lines have been detected by Jeffries et al. (1995).

BD+08102 = BLPsc: has been extensively studied by Kellett et al. (1995) who report a K2V spectral type, optical variability with several possible photometric periods, v$\sin$i=90 kms^-1, the absence of Li and the presence of a WD companion at about 2 arcsec. Our photometric and spectroscopic data are in full agreement with these results, with the photometric observations (Fig. 20) in agreement with the 0.2937 day period found by Kellett et al. (1995). However, Kellett et al. (1995) also speculate that more than 90% of the EUV flux is due to the WD and that the two stars form a wide binary system with the high rotation rate of the K star explained by its young age. These conclusions are in contrast with: a) the K star is an extreme active fast rotator and as such it must have a very strong X-ray and EUV emission and b) the K star has a very low, if any, Li abundance and as such cannot be very young. The high rotation rate of the K star, instead, could be explained by tidally effects induced by close binarity. Indeed, there is a clear indication of RV variability in the two spectra we have of the K2V component.

BD+0973 = BKPsc: a high proper-motion star. Due to a blue excess in the U-B color, confirmed by us, the presence of a WD companion has been suggested by Weis (1991). Optical variability with a photometric period of 2.17 days was reported in the SAAO Annual Report (1993). Our observations (Fig. 21) confirm the optical variability but with a slightly longer period of 2.24$\pm$0.04 days. The SB1 nature, already noted by Jeffries et al. (1995), is confirmed by our RV measurements. The best fit of the observed colors and HIPPARCOSdistance is obtained by assuming a K5/6:V + M4:V + WD system.

SAO91772 = LN Peg: was reported as a SB1 Pop II binary with an orbital period of 1.84422 days by Latham et al. (1988). Optical variability with a period of 1.84 days was discovered by Rodonò et al. (1994). The observations presented in this paper (Fig. 22) are consistent with a shorter 1.820$\pm$0.015 day period. Pasquini & Lindgren (1994) estimated a magnitude difference $\Delta V$$\simeq$1.2 between the two components from the Wilson-Bappu relation. The color observed by us also suggest the presence of a late-type companion. The best spectral classification that agrees with both the observed colors and the HIPPARCOSdistance implies class V components, ruling out the subgiant classification reported, among others, by Ottmann et al. (1997). Finally, we note that the magnitude difference between the two components inferred by us is much larger than the value computed by Pasquini & Lindgren (1994). More recentely Fekel et al. (1999) discovered that SAO91772 is indeed a triple system.

SAO111210: a visual binary system ($\rho$=0.9 arcsec, $\Delta V$$\simeq$1.5) whose components were observed together both in photometry and spectroscopy. A low rotation rate is inferred for the secondary star, whose spectral type is computed to fit both the observed colors and the magnitude difference between the two components. We discovered optical variability with a period of 0.5473$\pm$0.0010 days (Fig. 23). Another possible photometric period is 0.844$\pm$0.002 days.

SAO150508: a star for which the HIPPARCOSsatellite gives a distance in the 14 - 88pc range. Our inferred spectral classification is consistent with the upper limit. We discovered optical variability with a period of 1.90$\pm$0.01 days (Fig. 24).

SAO150676: a star for which the two RV measurements we have show no sign of binarity. The colors are consistent with a G2 V classification and optical variability, with a period of 1.78$\pm$0.01 days (Fig. 25), has been discovered. Moreover, the very high v$\sin$i implies a minimum radius of 1.0$R_{\odot}$, so that we suggest that this star could be still in the PMS phase.

SAO151224 = HY CMa: an eclipsing binary (Cutispoto et al. 1995) that appears as SB2 in our spectra. The HIPPARCOSdistance has a large uncertainty and thus it is difficult to assign a well defined spectral classification. Osten & Saar (1998) inferred K3IV + K1IV spectral types. The v$\sin$i of the secondary component derived by us (11$\pm$2 kms^-1) is in agreement with the value reported by Osten & Saar (1998). However, we got a rather larger value for the v$\sin$i of the primary component and the resulting radii of 3.8 $R_{\odot}$ and 1.6 $R_{\odot}$ for the primary and the secondary components, respectively, seems to us more adequate for class V/IV than for class IV stars. We note that, although they fit the colors equally well, the tentative spectral classifications reported by Cutispoto et al. (1995) do not agree with the inferred radii.

SAO196024: we find it to be a variable star with a photometric period of 1.422$\pm$0.007 days (Fig. 26). The colors and the spectral signatures indicate a K0V classification. There is another possible photometric period of 2.47$\pm$0.02 days. However, such longer period would imply a radius that is too large for a K0 dwarf.

SAO234124 = XZ Pic: is an SB1 system, as shown by our RV measurements. This star is reported as an unsolved variable in the HIPPARCOSvariability annex. Our photometric observations (Fig. 27) detected variability with a period of 1.87$\pm$0.02 days. The inferred spectral classification is the one that best fits the spectral characteristics, the colors and the distance measured by HIPPARCOS.

SAO243278: ia a component of a triple visual system. Components A+B (= HD 143474) are two bright A-type stars separated by 0.191 arcsec, whose distance has been measured by HIPPARCOS. Component C, at about 11 arcsec from HD 143474 is SAO243278. It is reported to be a G8V+K4V binary with an orbital period of 0.82376 days (Mason et al. 1995); our spectroscopic observations confirm the SB2 nature (see also Tagliaferri et al. 1999). We assume that SAO243278 is physically linked to HD 143474. Consequentely, the HIPPARCOS distance, the spectral characteristics and the observed colors are better matched by a G6V+K0:V system.

Acknowledgements

Stellar activity research at Catania Astrophysical Observatory is supported by the Italian "Ministry for Universities and Research" (MURST) and the "National Research Council" (CNR: Gruppo Nazionale di Astronomia) that are gratefully acknowledged. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. A special thank is also due to the ESO staff for the collaboration and technical support during the observations, although the discouraging policy of ESO toward small telescopes will not make studies like the present one feasible in the future, and to Ms. Gina Santagati for revising the manuscript. Last but not least we thank the referee, Dr. M.F. Sterzik, for his usefull comments on the first version of this paper.