COMMISSION 27 OF THE I. A. U. INFORMATION BULLETIN ON VARIABLE STARS Number 2284 Konkoly Observatory Budapest 1983 March 1 HU ISSN 0374-0676 SPECTROSCOPIC EVIDENCE FOR SHORT PERIOD AND HIGH ECCENTRICITY OF THE BINARY ORBIT OF omicron ANDROMEDAE omicron And is an eclipsing spectroscopic single lined binary. Guthnick (1941) suggested a light variation period of 1.5765 days. Schmidt (1959) gave a period of 1.5998398 days from his much more accurate photoelectric measurements. But Bossi et al. (1977), Pastori et al. (1982) and Baade et al. (1982) disagreed with this period. Pastori et al. (1982) gave a period of 23.5 years from spectroscopic analysis. Baade et al. (1982) have concluded that short term quasiperiodic radial velocity variations are not present during the initial stage of the new shell phase. Further, there is no spectroscopic evidence for omicron And to be a short period spectroscopic binary. o And underwent a shell phase in 1981 and is still in shell phase (Bossi et al. /1982/, Hayes /1982/). We have been continuously observing this shell spectrum since 15 October 1981, in Halpha at a dispersion of 17.2 angstrom/mm on 09802 Kodak Plates. We report here our observations from 15 October 1981 to 5 October 1982 taken at the 100 cm reflecting telescope of Kavalur Observatory at its Cassegrain focus. In Table I we present, in order, date of observation, JD. phase (calculated from JD 2444948.147), measured radial velocity, calculated radial velocity and residual O-C from the elements adopted. Table I Radial Radial Date JD Phase Velocity Velocity O-C observed calculated km/s km/sec 15 Oct.1981 4893.166 0.167 -41.13 - - 16 Oct.1981 4894.094 0.278 -39.07 -39.06 -.01 8 Dec.1981 4947.092 0.369 -0.66 -5.95 5.29 9 Dec.1981 4948.109 0.977 22.00 21.98 .02 9 Dec.1981 4948.132 0.991 29.26 - - 9 Dec.1981 4948.147 0.000 38.26 - - 9 Dec.1981 4948.157 0.006 22.00 23.71 -1.71 11 Dec.1981 4950.063 0.144 1.12 6.97 -5.85 9 Jan.1982 4979.102 0.485 21.59 22.34 -0.75 23 Jan.1982 5144.430 0.213 -11.85 -14.74 2.89 5 Oct.1982 5248.188 0.174 -27.06 - - 5 Oct.1982 5248.261 0.217 -19.11 -15.97 -3.14 The orbital elements obtained are as follows: K = 34.165 km T0 = JD 2444894.0905 V0 = 13.50 km/sec P = 1.67458d e = 0.539 a sin i = 662437.8 km omega =177.046d f(m) = 0.004 [FIGURE 1] Figure 1 Radial Velocity Diagram The radial velocity curve is shown in Figure 1. We omitted four observations, in deriving the orbital elements. These observations do not lie on the RV curve adopted and differ in computed values from the elements adopted. The eclipse of the bright star occurs at E on the decreasing branch of the RV. curve where it intersects the V0 axis. Just before E, two observed RV are + ve differing the RV curve and just after E, two observed RV are - ve differing the RV curve. This is explained by the rotation effect and the gas stream present around the binaries. The binaries in which this effect has been found are all very close so that one can expect interactions like tidal waves or more violent phenomena. The gas streaming distorts the RV curve, in the sense that we have a positive amount of distortion just before eclipse and a negative amount just after eclipse. Without applying the proper correction we may thus find incorrect orbital elements. This explains the omission of the four observed RV for calculating the orbit. MAHIPAL SINGH Indian Institute of Astrophysics Bangalore - 560 034 India References: Baade, D., Pollok, H., Schumann, J.D., and Duerbeck, H.W., 1982, IBVS No. 2125 Bossi, M., Guerrero, G., and Mantegazza, L., 1977, Astron. Astrophys. Suppl. 29, 327 [BIBCODE 1977A&AS...29..327B ] Bossi, M., Guerrero, G., Mantegazza, L., and Scardia, M., 1982, IBVS No. 2082 Guthnick, P., 1941, Vierteljahrsschrift d. Astron. Gesell. 76, 62 Hayes, D.P., 1982, IBVS No. 2160 Pastori, L., Antonello, E., Fracassini, M., and Pasinetti, L.E., 1982, Astrophysics and Space Science, 86, 179 [BIBCODE 1982Ap&SS..86..179P ] Schmidt, H., 1959, Zeitschrift f. Astrophys. 48, 249 [BIBCODE 1959ZA.....48..249S ]