COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Number 2937 Konkoly Observatory Budapest 23 September 1986 HU ISSN 0374 - 0676 H-ALPHA AND LiI OBSERVATIONS OF THE RS CVn TYPE BINARIES: sigma Gem, alpha Aur, 93 Leo and HR 6469 Variations in the H-alpha line profiles of RS CVn binaries have been reported by numerous authors, but only a few objects are known where the H-alpha variations are correlated with orbital phase. Weiler et al. (1978) suggested such a correlation for V711 Tau (P=2.838 days) whereas Bopp and Talcott (1978) do not. On the other hand Bopp and Talcott report coherent H_alpha variations with orbital phase in UX Ari (P=6.438 days). Vogt (1981) monitored the H_alpha region of II Peg (P=6.724 days) and found a correlation between enhanced H_alpha emission and spot visibility in this well-studied RS CVn star. The evidence of a LiI 6707.8 line is a qualitative indicator of stellar age. Lithium abundances have been used to estimate rough ages of solar-type stars, but deriving quantitative ages is much more difficult (Soderblom, 1983). The main reason is that the depletion time scale is extremely sensitive to stellar mass. Consequently, we only give equivalent widths. Because of RS CVn's are post-main sequence binaries (Popper and Ulrich, 1977) the amount of LiI should be very small. The observations were obtained on 1985 Feb. 5, 7 and 8, May 10, 11 and 14 and Oct. 28 with the Cassegrain echelle spectrograph (Weiss et al., 1981) of the 1.5 m Vienna RC telescope. The detector used was a dual, liquid nitrogen cooled, Reticon CP-1001 array with 936 pixel each row (Schalk et al., 1985). The 79 g/mm echelle grating used with the 900 lines/mm cross disperser gave a reciprocal dispersion of 10 A/mm at H_alpha in the 34th order which covered a spectral range of ~250 A centered at 6602 A. The mean FWHM of the Neon comparison lines covers about 2 pixels, corresponding to a resolution of ~0.65 A. In our averaged observing conditions (seeing ~3", slit width 300 micron) the integration times varied from 20-60 minutes for a uniform signal-to-noise ratio of typically ~200 (except of alpha Aur, where SNR ~400 with 2min). Table I H_alpha data EW (a) counts (lambda_c)/counts(cont.) FWHM [mA] [km/s] (S1) -1022 0.53 91 sigma Gem(S2) - 943 0.51 82 (S3) - 950 0.51 76 alpha Aur -1445 0.36 91 93 Leo -1249 0.48 87 HR 6469 -1360 0.38 74 V 711 Tau + 685 1.24 132 HR 5110(H1) - 780 0.77 100 HR 5110(H2) - 650 0.75 87 psi UMa -1069 0.32 59 (a) From that these are actually measured equivalent widths from the composite spectrum. sigma Gem (=HR 2973 = HD 62044): The single-line spectrum shows rotationally broadened lines. The H_alpha feature is clearly filled in by chromospheric emission as was mentioned by Smith and Bopp (1982). These emission is present during our February run as well as in the May-data, five epochs later. But there are still not enough data to look for season-to-season changes of these emissions. All H-alpha data are summarized in Table I. The LiI 6707.8 line seems to be present in all spectra but is strongly blended (W_lambda ~31 +-10 mA). [FIGURE 1] Fig. 1: Enlarged view of the Halpha region for our program stars along with the nonactive single star psi UMa. The spectra were shifted to be in accordance with the psi UMa spectrum. sigma Gem, HR6469 and 93 Leo show chromospherically filled in absorption cores. alpha Aur (= HR 1708 = HD 34029) is a double-line spectroscopic binary consisting of a G6III primary and an active F9III secondary. Shen et al. (1985) fitted two Gaussians to the line profiles to deconvolve both components from the composite spectrum near conjunction and found for the relative "dip"-strength G6/F9 = 1.7+-0.2. In our high SNR, 10 A/mm-spectrum taken at phase 0.091, the secondary spectrum can be clearly seen, but all lines (except of LiI) were blended by these broad F9-lines in a way which corresponds to a relative "dip"-velocity shift of ~30 km/s to the blue. The derived relative "dip"-strength is 1.69+-0.05 using the NiI 6643 line. The composite H_alpha absorption feature reaches down to ~0.4 that of the continuum. If any emission occurs it is surely a weak one, not comparable with sigma Gem. A visual comparison of the LiI 6707.8 region (Fig. 2) with the two spectra given by Boesgaard (1971) in her Figure 2, p. 513, showed a remarkable different intensity ratio between the nearby FeI lines from the G-component and the LiI 6707.8 line from the F-component. But this is probably due to larger blending in our spectrum. No LiI line from the G-star is seen, it is fully blended by the broad F-line and an FeI-line at 6707.44 A. The measured equivalent widths were corrected for the effect of composite continuum by multiplying with 1.67 for the G-star and 2.50 for the F-star. 93 Leo (=HR 4527 = HD 102509) exhibits a composite spectrum of a A7V and an G5III-IV component, with the presence of moderately strong emission in the H and K lines from the G-star. All lines are sharp and belong to the late-type component which contributes 0.67 of the total light in V. This corresponds to V-magnitudes of 5.52m for the A-, and 5.09m for the G-star. The actually measured equivalent widths were multiplied by a factor of 1.46 for correction of the composite continuous spectrum. The H_alpha line of the G-star is fully blended by the broad and shallow H_alpha feature of the A-component. The slight asymmetry of the blue wing is in accordance with a velocity shift of ~25 km/s relative to the G-component at phase 0.060. We used a H_alpha spectrum of Vega (A0V), also at 10 A/mm, to subtract it from the composite 93 Leo spectrum (after the Vega-spectrum was shifted to be in accordance with the early type component in 93 Leo). From this and from the composite spectrum follows that the high H_alpha core intensity is not due to rotational effects but indicating that the normal absorption line is filled in by emission. [FIGURE 2] Fig. 2: Reticon spectra of the LiIlambda6707 region (10 A/mm original dispersion and 0.65 A resolution). The spectra were shifted to be in accordance with the CaIlambda6717 line of psi UMa. As seen in Figure 2, a weak blended LiI line (W_lambda=70+-10 mA) from the G-star is observable. We derived a ratio EW (Li 6707)/EW(Ca 6717) = 0.44 and a relative abundance of Li/Ca = 1.2. Recently, Walter (1985) reported that the G-component is the X-ray source in the 93 Leonis system. HR 6469 (= HD 157482) is a double-lined F7V + 7 + G5IV binary with a third spectroscopic component. Two components were resolved by McAlister et al. (1983) at 0.04" separation using speckle interferometry techniques. We are not able to resolve the second component in our 10 A/mm-spectrum, although we have a good SNR, we are limited by a spectral resolution of ~25 km/s. The photospheric lines are sharp and similar to the lines of the G-star in 93 Leo. In comparison with the F9III secondary of the alpha Aurigae system, HR 6469 shows a very weak LiI 6707.8 feature (W_lambda ~61+-15 mA). Visual inspection of the H_alpha profile displayed in Figure 1 reveals as weak emission. K.G. STRASSMEIER (1) S. WEICHINGER (2) A. HANSLMEIER (1) (1) Institut für Astronomie, Universitat Graz, Universitatsplatz 5, A-8010 Graz, Austria (2) Institut für Astronomie, Universitat Wien, Turkenschanzstrasse 17, A-1180 Wien, Austria References: Boesgaard, A.M.: 1971, Astrophys. J. 167, 511. [BIBCODE 1971ApJ...167..511B ] Bopp, B.W., Talcott, J.C.: 1978, Astron. J. 83, 1517. [BIBCODE 1978AJ.....83.1517B ] Boyd, L.J., Genet, R.M., Hall, D.S., Persinger, W.T., Fried, R.E.: 1985, Inf. Bull. Var. Stars 2675. McAlister, H.A., Hendry, E.M., Hartkopf, W.I., Campbell, B.G., Fekel, F.C.: 1983, Astrophys. J. Suppl. 51, 309. [BIBCODE 1983ApJS...51..309M ] Popper, D.M., Ulrich, R.K.: 1977, Ap.J. 212, L131. [BIBCODE 1977ApJ...212L.131P ] Schalk, A., Weiss, W.W., Rainer-Harbach, U., Ogris, V.: 1985, preprint - Vienna Observatory. Shen, L.-Z., Beavers, W.I., Eitter, J.J., Salzer, J.J.: 1985, Astron. J. 90, 1503. [BIBCODE 1985AJ.....90.1503S ] Smith, S.E., Bopp, B.W.: 1982, Astrophys. Lett. 22, 127. [BIBCODE 1982ApL....22..127S ] Soderblom, D.R.: 1983, Astrophys. J. Suppl. 53, 1. [BIBCODE 1983ApJS...53....1S ] Vogt, S.S.: 1981, Astrophys. J. 247, 975. [BIBCODE 1981ApJ...247..975V ] Walter, F.M.: 1985, Publ. Astron. Soc. Pacific 97, 643. [BIBCODE 1985PASP...97..643W ] Weiler, E.J., Owen, F.N., Bopp, B.W., Schmitz,M., Hall, D.S., Fraquelli, D.A., Piirola, V., Ryle, M., Gibson, D.M.: 1978, Astrophys. J. 225, 919. [BIBCODE 1978ApJ...225..919W ] Weiss, W.W., Barylak, M., Hron, J., Schmiedmayer, J.: 1981, Publ. Astron. Soc. Pacific 93, 787. [BIBCODE 1981PASP...93..787W ]