COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                    Number 3120


                                    Konkoly Observatory
                                    Budapest
                                    11 December 1987

                                    HU ISSN 0374-0676


            HD30861, A NEW ELLIPSOIDAL VARIABLE *

The first announcement for variability of HD30861 (spectral type according to
the Michigan catalogue: A2V, Houk, 1978) was given by Hensberge et. al. (1981).
They used this star as a comparison for the CP2 star HD30849, but rejected it
later due to evident variability


                             [FIGURE 1]


 * Based on observations obtained at ESO, La Silla/Chile.

  In order to check independently the variability and to determine the period we observed
HD30861 in 1981 and 1986 at La Silla/Chile. The ESO 50cm (Stromgren photometry) and
the Dutch 90cm (simultaneous Walraven photometry) telescope, respectively, were used.
The comparison star was HD31640 (spectral type according to the Michigan catalogue:
A3/5m, A5-7, derived from CaII K, Hydrogen and metal lines, respectively), for which the
constancy was already well established (Hensberge et al.).

  Our investigations were successful. We found a double wave variation and estimated a
preliminary period of 0.852 days. The phase relation, referring to the first observation, is
given by
               JD = 2446775.5520 + E 0.852 d.

Figure 1 presents the light curve in Walraven V. Notice that Walraven V is given as log10
intensity (multiply with -2.5 to be on a magnitude scale). The fit was obtained by a
function of the type

            

with phi = phase and phi0 = 0.28. In the case of Walraven V we obtained a0 = 0.2420, a1 =
.0072 and a2 = .0236. It seems that a2 is independent of wavelength (0.0234+/0.0002 in all
Walraven passbands), while al reaches a maximum near the Balmer jump (a1 = 0.0090 in
Walraven L). The standard deviation for individual V measurements, as computed from
the scatter of the absolute Walraven V for the comparison star (relative to their average),
is sigma v = .0019.

  The final analysis of the complete photometry is under way and will be published
elsewhere.



      W. VERSCHUREN                     University of Antwerp (RUCA)
                                        Theoretical Mechanics and Astrophysics
      H. HENSBERGE                      Groenenborgerlaan 171
                                        B-2020 ANTWERP


      H. SCHNEIDER                      Universitats-Sternwarte
                                        Geismarlandstr. 11
                                        D-3400 GOTTINGEN


      K. PAVLOVSKI                      Faculty of Geodesy
                                        Hvar Observatory
                                        Kariceva 26 
                                        YU-41000 ZAGREB


References :

Houk, N. 1978: "Michigan catalogue of two-dimensional spectral types for the HD stars"
  Vol. 2, Dept. Astron., Univ. Michigan [BIBCODE 1978mcts.book.....H ]
Hensberge, H., Maitzen, H.M., Deridder, G., Gerbaldi, M., Delmas, F. Renson, P., Doom, C.
  Weiss, W.W., Morguleff, N. 1981: Astron.Astrophys. Suppl. 46, 151 [BIBCODE 1981A&AS...46..151H ]