COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 1761 Konkoly Observatory Budapest 1980 March 24 SPECTROSCOPIC AND PHOTOELECTRIC MEASUREMENTS OF nu Eri Photometric observations (partly simultaneously with two telescopes) of the Beta Cep-star nu Eri (P~=4h10m) in 1974 at the ESO site in La Silla/Chile revealed a secondary hump in two out of three light curves. The hump is located in the ascending branch around maximum radial velocity. The data did not allow to decide whether this secondary hump repeats every cycle or not. Additional spectroscopic and photoelectric observations have been performed in 1977 at the same site though the position of the star was not favourable (maximum height above horizon approx. 40deg). All observational data are compiled in Table I and II. The reduction techniques concerning the photometry and scanner observations were the same as described by Haefner et al. (1975) and Schoembs et.al. (1976), respectively. Table I Photometric observations a) Photometry Time- Integr.- Res./ Time/ Telesc. Date Start Duration Filt. Filter Filter^*) (UT) (s) (s) 61 cm 1974,Nov.24/25 02^h33^m00^s 4^h17^m00^s 4 1 H_beta(w/n) 61 cm 1974,Nov.4/5 02 30 00 4 17 00 4 1 " 61 cm 1974,Nov.12/13 02 04 30 4 25 30 4 1 " 50 cm 1974,Nov.12/13 02 11 10 4 18 20 1 0.99 Int./H_alpha 50 cm 1977,March9/10 00 15 00 2 05 00 6 1 H_beta(w/n) 50 cm " 11/12 00 21 00 1 50 00 6 1 " 50 cm " 12/13 00 27 15 1 57 45 6 1 " 50 cm " 15/16 00 23 05 1 26 55 6 1 " 50 cm " 16/17 00 25 00 1 40 00 6 1 " ^*) H_beta(w/n): wide (delta lambda=175A), narrow(delta lambda=29A), quasisimultaneously used by means of a rotating filter wheel, cycle time 2s (1974) or 3s (1977), Int./H_alpha: white light, H_alpha(delta lambda=3A), two channel photometer. b) Scanner Band Spectr. Time Telesc. Date Start Duration Line width Res. Res. (A) (A) (s) 50 cm 1974,Nov.24/25 02^h33^m00^s 4^h15^m H_alpha 230 7 8.192 Table II Spectroscopic observations Plate^*) Midexposure Exposure Phase No. HJD 2440000+ Time(min) G 8315 3229.5189 4 0.875 G 8332 3230.5057 8 0.562 G 8333 3230.5157 9 0.620 G 8334 3230.5265 10 0.682 G 8335 3230.5383 12 0.750 G 8361 3231.5209 12 0.413 G 8362 3231.5348 10 0.494 G 8363 3231.5500 12 0.581 G 8386 3232.4944 8 0.024 G 8387 3232.5020 7 0.068 G 8389 3232.5250 10 0.200 G 8390 3232.5364 11 0.266 G 8438 3234.4852 8 0.498 G 8439 3234.4929 6 0.542 G 8440 3234.5036 15 0.604 G 8441 3234.5192 18 0.694 G 8442 3234.5317 10 0.766 G 8443 3234.5415 12 0.822 ^*) 1.5m telescope, Coude, dispersion 12.4 A/mm, emulsion 098-2. [FIGURE 1] Fig. 1. Part of the light curves (not corrected for extinction) of 1974 Dec. 4/5 in H_beta-w (2) and the simultaneous runs of Dec. 12/13 in H_beta-w (3) and white light (4) showing the secondary peak. Fig. 1 shows some light curves of Dec. 1974. The duration of the small secondary peak is approx. 1000s~=0.06P and the relative amplitude between approx. 1.0 and 1.5% in H_beta(w/n) and somewhat smaller in white light, indicating a connection with the H-lines (see also Fig.3). The photometric runs of March 1977 are generally of worse quality because of the appreciable air mass during the observations. Mostly they cover less than half a period. In order to isolate the secondary hump in these data too, all proposed periods including overtones and resonance oscillations according to Van Hoof (1961) and Saito (1976) have been tested, but without success. Unfortunately the beat period, which would approx. be consistent with the data of Dec. 1974, cannot be checked with the present observations. [FIGURE 2] Fig. 2. Radial velocity curve. Average error of the weighted means is +-1.5 km/s. Symbols: (nabla) G 8315, (square) G 8332-35, (triangle) G 8361-63, (circle) G 8386, 87, 89, 90, (dot) G 8438-43. Fig.2 shows the weighted mean radial velocities as determined from the lines listed in Table III. The phases have been computed using the time of minimum radial velocity given by Laskarides et al. (1971) and a period of 0.1735089d. The scatter is due to the Blashko-effect. No Van Hoof-effect could be detected and no unusual behaviour around the time of maximum radial velocity (approx. position of the secondary hump) can be seen. According to Laskarides et al. (1971) and Laskarides (1973) a "filling in" of the H-lines by emission in the ascending branch of the radial velocity curve (around minimum light) should be observed. A careful examination of the H_alpha-profiles and equivalent widths did not reveal this effect though especially this line should strongly be affected by possible emission. The equivalent widths remained constant and the line profile variations was the same for all the lines. The failure of the "filling in"-test may be explained by the scanty data around this special phases. Furthermore it might be that the "filling in" only is present with varying strength in different cycles. This is confirmed by the scanner equivalent widths of H_alpha, which cover one complete cycle. As shown in Fig. 3 there is a slight variability which exceeds the error of the measurements. But only the second minimum around maximum radial velocity phase 0.6 - 0.7 found by Laskarides et al. (1971) is clearly present whereas around phase 0.2 (expected "filling in") no minimum can be noticed. The radial velocity and equivalent widths for the interstellar D1 and D2-lines are (22.0+-0.5) and (21.3+-0.3) km/s and (103+-4) and (138+-5) mA, respectively. These values are in good agreement with values given for D1 by Hobbs (1978). Table III Lines used for radial velocity and equivalent width determinations on all plates. Wavelength (A) Identification Weight for RV-det. 6678.149 HeI 1 6582.85 CII 0.5 6578.03 CII 0.5 6562.817 H_alpha 1 5875.618 HeI 1 .650 5739.762 SiIII 0.5 5722.65 AlIII 0.5 5696.47 AlIII 0.5 5679.56 NII 0.5 5666.64 NII 0.5 5895.923 NaI D1 interst. 5889.953 NaI D2 interst. [FIGURE 3] Fig. 3. Variation of the H_alpha-equivalent widths from scanner observations. Each point is the average of approx. 40 foreward and backward scans of 8.192 s. Vertical bar: mean error. The phases refer to the radial velocity curve (minimum: phase 0). R. HAEFNER R. SCHOEMBS Universitats-Sternwarte Scheinerstr. 1 D-8000 Munchen 80 Germany (W) References: Haefner, R., Metz, K., Schoembs, R., 1975, Astron. Astrophys. 38, 203 [BIBCODE 1975A&A....38..203H ] Hobbs, L.M., 1978, Astrophys. J. Suppl. 38, 129 [BIBCODE 1978ApJS...38..129H ] Laskarides, P.Q. 1973, Astron. Astrophys. 26, 91 [BIBCODE 1973A&A....26...91L ] Laskarides, P.Q., Odgers, G.J., Climenhaga, J.L. 1971, Astron. J. 76, 363 [BIBCODE 1971AJ.....76..363L ] Schoembs, R., Spannagl, C. 1976, Astron. Astrophys. Suppl. 26, 55 [BIBCODE 1976A&AS...26...55S ] Saito, K., 1976, in Multiple Periodic Variable Stars (ed. W. Fitch) Contributed Papers p. 47 [BIBCODE 1976mpvs.conf...47S ] Van Hoof, A., 1961, Zeitschrift f. Astrophys. 53 106 [BIBCODE 1961ZA.....53..106V ]