COMMISSION 27 OF THE I.A.U.
              INFORMATION BULLETIN ON VARIABLE STARS
                           Number 1246

                                                    Konkoly Observatory
                                                    Budapest
                                                    1977 March 1


         RADIAL VELOCITIES OF Me-TYPE STARS

The kinematical studies available on Mira Ceti Me-type
stars have not yet allowed to obtain a clear idea of the 
distribution of these objects in our own Galaxy. Furthermore, these
studies are not complete enough as to permit deriving the main
properties of such stars considered as subsystems: Merrill (1),
Merrill and Wilson (2), Kukarkin (3) and Ikaunieks (4). All this
is mainly due to the scarcity of data on these peculiar stars.
Therefore, it is evidently desirable to contribute with more and
better data of these stars.
   The method proposed by Stock and Osborn (5) offers the 
possibility of obtaining approximate radial velocities of numerous
stars, with an accuracy of about 20 km/sec. Furthermore, the
method is advantageous because it permits to analyse all the
stars in a given plate and to detect high radial velocity stars.
   A total of five plates covering 5x5 deg in the sky have
been taken in Ara (RA = 17h35m, Dec. = -53.0deg, 1950) using the 24-in.
Curtis Schmidt telescope of the Cerro Tololo Inter-American 
Observatory (Chile). The telescope-prism combination used yields
a dispersion of 225 A/mm at H-gamma. Kodak IIa-O plates were exposed
for twenty minutes, widening the spectra to about 0.2 millimeters. 
The measurement of the positions of 13 Me-type stars
found in the plates have been carried out using an Ascorecord
Zeiss Jena machine and standard astrometric methods.
   In the thirteen Me-type stars only the emission lines H-gamma
and H-delta are visible. For comparison purposes approximately 100
A and F-type stars were selected and measured in the field of
each plate. In addition, radial velocities of the Me-type stars
were obtained using the method described by Stock and Osborn (5).
It should be pointed out that the method developed by these 
authors for obtaining radial velocities using pairs of objective
prism plates, gives only radial velocities relative to the average 
velocity of the comparison stars. The discrepancies between
these velocities and the heliocentric ones are due mainly to the
solar motion toward the Apex. However, this effect is practically 
zero at the surveyed. region Consequently, radial velocities
from slit spectrograms and the present relative velocities may
be directly compared.
   For each Me-type star an independent radial velocity was
derived from the H-gamma and H-delta lines, respectively. Finally,
an average velocity was obtained for each star. Unfortunately, when
determining radial velocities of Me-type stars we must take into
account the intrinsic kinematical properties of such stars. In
fact, radial velocities of Me stars determined from emission
lines are generally different from those obtained from absorption 
lines, this difference being about 20 km/sec. (6).


                       Table 1

No      alpha         delta      Phot.   mag.   Radial v.  N
     h  m  s        d  '  "       max.   min.    km/sec.
 
 1   17 16 31.21   -53 49 41.2   13.2   16.5     -117      1
 2   17 17 14.14   -53 40 46.0   13.0   17.5     -156      4
 3   17 19 32.73   -51 37 12.1                   +102      4
 4   17 21 48.19   -51 56 12.6                   -191      2
 5   17 22 23.98   -55 14 44.5   13.8   16.5     - 37      1
 6   17 24 55.39   -54  6 43.8   12.4   18.      - 22      4
 7   17 26 20.52   -50 59  0.8                   +  9      4
 8   17 29 58.83   -53  7 34.4                   - 47      4
 9   17 31 48.32   -55 25 41.1                   + 56      4
10   17 34 16.77   -52 32  1.9   13.5   16.7     - 80      4
11   17 38  8.77   -50 59 51.5   12.0   14.5     + 21      4
12   17 44 25.59   -52 56  3.8                   -108      4
13   17 36 22.74   -51 32 33.4                   - 52      1

Results
   The results are listed in Table 1, whose successive columns
give: Star identification, right ascension and declination for
the equinox 1950.0 (the accuracy in these coordinates are: 0.05s
and 0.2", respectively), the apparent photographic magnitude for
the maximum and minimum, respectively, taken from Kukarkin et al.
(7), the radial velocities, and number of measurements used for
determining the positions and radial velocities.


                                      M. IBANEZ
                                 Physics Department,
                                 Los Andes University,
                                 Merida, Venezuela *



References:

1. Merrill, P., Ap. J., 94, 171 (1941) [BIBCODE 1941ApJ....94..171M ]
2. Merrill, P. and Wilson, R., Ap. J., 95, 248 (1942) [BIBCODE 1942ApJ....95..248W ]
3. Kukarkin, B.V., Investigation of the Structure and Evolution of Stellar
    Systems on the Basis of Variable Stars Studies, G.I.T.T.L., Moscow (1942)
4. Ikaunieks, J., Trans. Astrophys. Lab. Acad. Sci. Latvian SSR, 11, 58 (1963)
5. Stock, J. and Osborn, W., 1971; I.A.U. Symposium No. 50, 290
6. Rosseland, S., The Pulsation Theory of Variable Stars, Dover Publication,
    Inc. (1964)
7. Kukarkin, B. et al., General Catalogue of Variable Stars, 3rd edition
    Moscow,(1969)

* Now at Department of Astronomy, University of Edinburgh,
  Edinburgh, U.K.