COMMISSION 27 AND 42 OF THE IAU
                   INFORMATION BULLETIN ON VARIABLE STARS
                               Number 3807

                                                         Konkoly Observatory
                                                         Budapest
                                                         18 November 1992

                                                         HU ISSN 0374 - 0676



          Mu Serpentis: A Doubled-Lined Spectroscopic Binary

For high dispersion spectroscopists who are studying elemental abundances, the
discovery that a star one is studying is a double-lined spectroscopic binary
can substantially increase the difficulty of analysis. But to those
researchers who are more concerned about other stellar properties, the star
then gains a new usefulness. With the use of electronic detectors capable of
obtaining high signal-to-noise spectra, the discovery of the lines of
companions to many known single-lined spectroscopic binaries should be
possible. This is important for understanding the frequencies of systems with
large mass ratios.
   The Bright Star Catalogue (Hoffleit 1982) indicates that Mu Ser (= HR 5881=
HD 141513) (spectral type A0 III; Gray and Garrison 1987) is a spectroscopic
binary. Campbell and Moore (1928) suspected that this star might be
double-lined. Frost, Barrett, and Struve (1929) found a variable radial
velocity and noted that Mu Ser might be a spectroscopic binary.
   Lambert, McKinley, and Roby (1986) noted that their spectrum of Mu Ser shows
"C I profiles to contain a sharp and a broad component, a likely signature of a
double-lined spectroscopic binary". Our spectra confirm this result. In
Figure 1 we illustrate one section from the three spectra we obtained with the
coude spectrograph of the 1.4-m telescope of the Dominion Astrophysical
Observatory with a reciprocal dispersion of 4.3 Angstrom mmE-1 using a 1872
element bare Reticon. We estimate that the rotational velocities of the two
components are 8 and 90 km s^-1. By comparison Slettebak (1954) found v sin i
= 80 km s^-1.  We hope that this example will encourage other high dispersion
spectroscopists to report their discoveries of lines due to companions.


                                [FIGURE 1]

 Fig. 1. A section of the spectrum of mu Ser obtain with the coude
 spectrograph of the DAO at 4.3 A mm^-1. Lines of two different
 widths produced by the components of this spectroscopic binary are evident.



          GRANT HILL
          Department of Astronomy, University of Western Ontario, London,
          ON N6A 3K7, Canada

          GRAHAM HILL
          Dominion Astrophysical Observatory, National Research Council of
          Canada, 5071 W. Saanich Road, Victoria, BC V8X 4M6 Canada

          SAUL J. ADELMAN
          Physics Department, The Citadel, Charleston, SC 29409 USA



References:

Campbell, W.W., and Moore, J.L., 1928, Publ. Lick Observatory, 16, 229.
Frost, E.B., Barrett, S.B., and Struve, O., 1929, Publ. Yerkes Obs., 7, 1. [BIBCODE 1929PYerO...7....1F ]
Gray, R.O., and Garrison, R.F., 1987, ApJS, 65, 581. [BIBCODE 1987ApJS...65..581G ]
Hoffleit, D., 1982, The Bright Star Catalogue, 4th edition (New Haven: Yale
      University Observatory).
Lambert, D.L., McKinley, L.K., and Roby, S.W., 1986, PASP, 98, 927. [BIBCODE 1986PASP...98..927L ]
Slettebak, A., 1954, ApJ, 119, 146. [BIBCODE 1954ApJ...119..146S ]