COMMISSION 27 OF THE I.A.U.
              INFORMATION BULLETIN ON VARIABLE STARS
                           Number 1220

                                             Konkoly Observatory
                                             Budapest
                                             1976 December 20


     AN EXTREME REDDENING OF THE CARBON STAR RW LMi=CIT 6

The photographic observations of RW LMi=CIT 6 made at the
Radioastrophysical Observatory at the end of the last October,
J.D. 2443073 to 2443080, show that since the end of the previous
observing season, J.D. 2442873 to 2887, the colour index B-V of
this infrared carbon star has increased from the value B-V=1.5m
to B-V=2.5m, while at only a little earlier time interval, J.D.
2442760 to 2868, the mean of the colour index values for 10 nights
was B-V=1.0m.
   The blue-red (lambda_eff.=0.63micron) colour index at the same time
has increased from B-R=2.6m to B-R=4.2m, while at the interval
J.D. 2442760 to 2868 it was B-R=2.2m.
   The range of the B-V variations according to our observations 
made in B and V magnitudes since J.D. 2441060. as well as
others published and made in B and V since J.D. 2439889 by
Kruszewski (1971, 1973) is B-V=0.9m to B-V=1.6m. The observations
in B and G filters by Kruszewski and Coyne (1976) show that sometimes 
the colour index of CIT 6 was even smaller.
   The usual range of colour index B-R variations was 1.9m-2.9m.
   Only the first ever made (probably in May, 1966) and published 
observations of B and V magnitudes by Wisniewski et al.,
(1967) also show similar colour index: B-V=2.47m extremely large
for this star (but still very small to compare with other infrared 
carbon stars).
   The other, third, occasion when CIT 6 is known to be 
unusually red was in April-May 1970, J.D. 2440677 to 0713, when
our blue-red observations indicated the value of the colour index 
B-R=4.1m (Alksnis and Eglitis, 1973).
     On all three occasions of extreme reddening the star was
near its maximum phase according to the elements Max.=J.D.
2441880 + 640 E (Alksnis and Khozov, 1975), the epochs and phases
being 5.9 (?), 2.16 and 1.87. In the latest reddening, however,
the star is more than 1 magnitude fainter than in the other two
previous cases, B magnitude being at its faintest value, 17.4m.
   The B and R (0.63) magnitude long period variations for
RW LMi based on our observations are shown in Fig. 1 where dots
represent the mean values for time intervals 0.1 P; period P=
=640 days.
   Polarization measurements of CIT 6 (Khozov, unpubl.,
Kruszewski 1971, 1973, Kruszewski and Coyne, 1976) have never
been made at the intervals of extreme redness of the star, 
although they might be of great importance for studying the 
processes taking place in the object. Thus polarization measurements
in blue, visual and red are now urgently needed.
   It is difficult to tell how long this state of extreme
redness will last; the observations of the last two cycles of
long period variations of the star, however, give evidence, that
after the calculated phase of maximum brightness, colour indices
of the star decrease (Fig. 2). But the next predicted maximum
time is at the middle of January 1977.
   Finding chart of RW LMi=CIT 6 can be found in our previous 
paper (Alksnis and Eglitis, 1975).


                                A. ALKSNIS
                                I. EGLITIS

                         Radioastrophysical Observatory
                         Latvian Academy of Sciences,
                         Riga, Latvia, U.S.S.R.


                              [FIGURE 1]

   Fig. 1. Long period variations of RW LMi according to the mean
   values of the magnitude R(0.63) and B for time intervals 0.1 P=64
   days. Calculated times of maxima are indicated at the top.


                              [FIGURE 2]

   Fig. 2. Colour index B-R(0.63) variations. Dots - one day mean
   values of B-R(0.63) averaged over time intervals 0.1 P; circles
   - differences between B - and R(0.63)- magnitude 64 day-means or
   sum of B-V and V-R(0.63) 64-day-means. Abscissa - time in periods.


References:

Alksnis, A., Eglitis, I., 1973, I.B.V.S. No. 812
Alksnis, A., Eglitis, I., 1975, Investigations of the Sun and Red Stars, Riga,
   No. 3, 35 [BIBCODE 1975ISKZ....3...35A ]
Alksnis, A.K., Khozov, G.V., 1975, Soviet Astron. J. Letters, 1, No. 7, 23
Kruszewski, A., 1971, Astron. J. 76, 576 [BIBCODE 1971AJ.....76..576K ]
Kruszewski, A., 1973, I.B.V.S. No. 781
Kruszewski, A., Coyne, G.V., 1976, Astron. J. 81, 641 [BIBCODE 1976AJ.....81..641K ]
Wisniewski, W.Z., Wing, R.F., Spinrad, H., Johnson, H.L., 1967, Astrophys. J.
   (Letters), 148, L29 [BIBCODE 1967ApJ...148L..29W ]