COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1640

                                    Konkoly Observatory
                                    Budapest
                                    1979 July 16



     INFRARED OBSERVATIONS OF LR Sco, AN RCB STAR


   LR Sco (HV 6539) is classed as an SR variable of 104.4 day period
(10.9m - 12.3m pg) (Shapley and Swope 1934, Kukarkin et al, 1970).
However recently Stephenson (1978) has classified its spectrum as
similar to that of R CrB at maximum, using objective prism plates.

   Table I lists JHKL (1.2, 1.6, 2.2 and 3.5micron) photometry of LR Sco.
These were obtained with the Mk II SAAO infrared photometer (similar
to the one described by Glass 1973) and using an In Sb detector on the
0.75m telescope at Sutherland. The results indicate an infrared excess
for LR Sco which is very similar to that of other RCB type stars. If
we take M_v ~ -4 (cf. Feast 1979) then A_v ~ 1.6 on the absorption model
of the galaxy used by van Herk (1965). Correcting the observations for
this reddening it is found that LR Sco lies in the region of other RCB
stars in the J-H/H-K and H-K/K-L diagrams (cf. Feast 1979),
   LR Sco can therefore be classified as an RCB star with some
certainly though typical RCB type minima have not been recorded. It
would be particularly valuable to confirm the 104.4 day period derived
by Shapley and Swope. RY Sgr which has a similar temperature to R CrB
has a pulsation period of 39 days (cf. Alexander et al.) and both R CrB
itself (Fernie et al. 1972) and UW Cen (Bateson 1972) have been reported
to have pulsation periods near 40 days. 104 days would be a very long
pulsation period for a star of the same temperature (and luminosity) as
R CrB. Longer periods may however exist for cooler RCB stars (e.g,
S Aps for which a period of 120 days has been reported (Waters 1966).


                  Table I

  Date             J             H             K             L
1979 May 8    8.20 +- .07   7.47 +- .05   6.52 +- .04   4.77 +- .05

    June 1    8.21 +- .06   7.50 +- .05   6.53 +- .04   4.70 +- .05


                    B.S. CARTER, G. ROBERTS, M.W. FEAST
                    South African Astronomical Observatory,
                    Cape, South Africa.
                    1979 June 26


References:

Alexander, J.B., Andrews, P.J., Catchpole, R.M., Feast, M.W.,
 Lloyd Evans, T., Menzies, J.W., Wisse, P.N.J., Wisse, M., 1972.
 Mon. Not. R. astr. Soc. 158, 305. [BIBCODE 1972MNRAS.158..305A ]
Bateson, F.M., 1972. Inf. Bull. Var. Stars No. 661.
Feast, M.W., 1979. I.A.U. Colloquium No. 46, Hamilton, New Zealand-
 in press. [BIBCODE 1979ctvs.conf..246F ]
Fernie, J.D., Sherwood, V. & Dupuy, D.L., 1972. Astrophys. J. 172, 383. [BIBCODE 1972ApJ...172..383F ]
Glass, I.S., 1973. Mon. Not. R. astr. Soc. 164, 155. [BIBCODE 1973MNRAS.164..155G ]
Kukarkin, B.V., Kholopov, P.N., Efremov, Yu. N., Kukarkina, N.P.,
 Kurochkin, N.E., Medredeva, G.I., Perova, N.B., Fedorovich, V.P.,
 Frolov, M.S., 1969.  General Catalogue of Variable Stars (Third Ed.)
 Moscow. [BIBCODE 1969gcvs.book.....K ]
Shapley, H. & Swope, H.H., 1934.    Harvard Ann. 90, No. 5. [BIBCODE 1940AnHar..90..177S ]
Stephenson, C.B., 1978.    Inf. Bull. Var. Stars No. 1453.
van Herk, G., 1965,    Bull. Ast. Inst. Neth, 18, 71. [BIBCODE 1965BAN....18...71V ]
Waters, B.H.J., 1966.    R.A.S. New Zealand Circ. 119.