COMMISSION 27 OF THE I. A. U.
       INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 260

                                     Konkoly Observatory
                                     Budapest
                                     1968 March 18


    ROTATIONAL VELOCITY OF RS (23) SEXTANTIS


This star was tentatively identified as a Beta Cephei variable (1) or "related
to the Beta Canis Majoris stars" (2) because of the observed light and radial
velocity changes. I have determined the projected velocity of rotation of RS
Sex by using the two-prism spectrograph of 

                        [FIGURE 1]

the 48" reflector of the Astrophysical Observatory at Asiago, Italy. 
The line-widths of neutral helium
at Lambda 4471 and Lambda 4026 at half central depth have been measured on
direct intensity tracings of 5 spectra (dispersion at H Gamma 42 A/mm) for RS
Sex, and on 45 spectra (dispersion at H Gamma 42 and 13 A/mm) of 7 standard
B2-3 stars (Iota Her, Eta Lyr, Theta Oph, Gamma Ori, 42 Cam, Eta Hya, Eta UMa).
The reduced rotational velocities of the comparison stars have been plotted
against known v.sin i values given by Huang (3), Slettebak and Howard (4)
(Fig.1). Using a linear correlation we obtained v.sin i=260 km/s for RS Sex,
which is an exceptionally high rotational velocity if the star is considered a
Beta Cephei variable. Recently, however, Hill (5) observed Beta Cephei-type
light variations in several broad-lined B stars in associations and galactic
clusters; RS Sex probably belongs to this new kind of variables.


I. ALMAR
Konkoly Observatory
Budapest

References:

1. de Jager, C. 1953, BAN 12, 91. [BIBCODE 1953BAN....12...91D ]
   Walker, M.F. 1952, AJ 57, 227. [BIBCODE 1952AJ.....57..227W ]
2. Underhill, A.B. 1966, The Early Type Stars. D. Reidel Publ. Co. Dordrecht,
   p. 259. [BIBCODE 1966ASSL....6.....U ]
3. Su-Shu Huang. 1953, ApJ, 118, 258. [BIBCODE 1953ApJ...118..285H ]
4. Slettebak, A., Howard, R.F. 1955, ApJ, 121, 102. [BIBCODE 1955ApJ...121..102S ]
5. Hill, G. 1967, ApJ Supp. Ser. 14, 263. [BIBCODE 1967ApJS...14..263H ]