COMMISSION 27 OF THE I. A. U.
               INFORMATION BULLETIN ON VARIABLE STARS
                           Number 2710



                                           Konkoly Observatory
                                           Budapest
                                           23 April 1985

                                           HU ISSN 0374 - 0676


                    A NEW SHELL STAR : HD 50845


  The star HD 50845 (K0) = BD -1deg1447 = SAO 133883 (alpha1950 =6h52m16.57s,
delta1950=-1deg13'05.3", m_v=8.2) was observed by us with the 1.50m coude 
spectrograph of the Cerro Tololo Interamerican Observatory, in Chile, on February 18
and 19, 1984 (UT). The material obtained - which was rather weak - is listed
in Table I. The plates were calibrated by means of a spot sensitometer.

              Table I

      Spectrograms of HD 50845 

Date (UT)#   Exposure Time   Emulsion   Dispersion*
JD (2,445,000+) (minutes)    (Kodak)    (A mm^-1 )

748.633        177            IIIa-F      18.6/37.2
748.738         99            098-04      18.6/37.2
749.665        289            IIa-O+098-04 9.0/18.0

# Mid-exposure
* second order blue (3900-5000 A)/first order red (5700-7000 A)

  The striking feature on our spectra of HD 50845 is that Halpha displays a
complex structure (see Fig. 1): a broad, shallow absorption line with 
superimposed incipient emission cut into by a strong, deep, sharp absorption 
core.

  If we compare our spectra of HD 50845 with the reproductions of stellar
spectra published in An Atlas of Representative Stellar Spectra (Yamashita
et al. 1977), we find that the former resembles that of a K0 Ib object. The
strongest lines correspond to Fe I, Ca II and Na I - which are sharp - and
to H. The lines of Ca II display the deepest cores.
  The radial velocity values that we have derived from our material are
given in Table II. The mean square errors have been estimated in around +/- 4
km s^-1 .

  The line profiles of most of the spectral lines, the radial velocity 
behavior and the fact that the Fe I lines arising from metastable levels are
the most conspicuous ones, suggest that the spectrum of HD 50845, at least
in the region represented on our plates, is that of a shell. In consequence,


                            [FIGURE 1]

 Figure 1: The Halpha profile in the spectrum of HD 50845. We have
 schematically drawn the broad absorption and the incipient emission that 
 appear to be present.


                            [FIGURE 2]

 Figure 2: The Ca II-K and H lines in the spectrum of HD 50845.
 Each profile suggests the presence of a broad absorption component in 
 addition to the sharp core.


                            [FIGURE 3]

 Figure 3: The Na I-D lines in the spectrum of HD 50845.







the K0 spectral classification assigned to the object does not correspond to
a star, it merely describes, in a rough way, the physical characteristics of
the shell around HD 50845.


                        Table II
              Radial Velocities of HD 50845
            Element/Feature    Radial Velocity
                        (km s )

           Halpha sharp core +10.4
           Hgamma sharp core + 7.9
           Fe I              +10.4 average of 8 values
           Na I              + 9.9
           Ca II             -10.1

  The stellar spectrum appears to be represented by the broad Halpha absorption,
which seems to be red-displaced by approximately 1 A with respect to the
laboratory position. There is also some indication of a broad stellar component
at Ca II (see Fig. 2). It seems, therefore, in order to conclude that the
stellar object is probably on the main sequence or quite close to it; as for
its spectral type, it ought to be earlier than K0.

  Figure 3 illustrates the Na I-D lines.
  An attempt will be made to secure better exposed spectra of HD 50845 to
improve our knowledge of the object.
  We are indebted to the Director and staff of the Cerro Tololo Interamerican
Observatory for their hospitality and efficient help that permitted us to
secure the observations reported here. We are also indebted to the Centre de
Donnees Stellaires, Strasbourg, for informing us of the lack of previous
spectroscopic studies of the star. Mrs. Margarita Trotz kindly prepared the
illustrations.



   JORGE SAHADE*                         ADELA E. RINGUELET*
   Instituto Argentino de                Instituto de Astronomia
   Radioastronomia                       y Fisica del Espacio
   C.C. 5                                C.C. 67, Suc. 28
   1894 Villa Elisa (Bs. As.)            1428 Buenos Aires
   Argentina                             Argentina

* Visiting Astronomer, Cerro Tololo Interamerican Observatory, supported by
  the National Science Foundation under Contract No. AST 78-27879. Member of
  the Carrera del Investigador Cientifico, CONICET, Argentina.

Reference :
Yamashita, Y., Nariai, K., and Norimoto, Y. 1977, An Atlas of Representative 
    Stellar Spectra (U. of Tokyo Press).



                            [From IBVS 2788]


                              ERRATUM



  In Figure 2 of the announcement on HD 50845 in IBVS No. 2710, the
wavelength interval between the arrows is 30 Angstrom, and not 5 Angstrom, as 
indicated.



                                     J. SAHADE