COMMISSION 27 OF THE I. A. U.
       INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 489


                                Konkoly Observatory
                                Budapest
                                1970 November 19


 ON THE VARIABILITY OF THE CARBON STARS CIT 5 AND CIT 13

     Among the 14 extremely cool stars found at the
California Institute of Technology (1) at least three are
carbon stars and possibly variables (2,3). P. Pesch (3) has
shown that two of them, CIT 5 and CIT 13, had been identified
as N-type stars at the Dearborn observatory and listed
as Nos 259 and 228 respectively (4,5), Do 228 having been
noted as variable (4). The last one has No 5438 in the 
Catalogue of Suspected Variable Stars (6).
      In order to find out the type of variability of the
two stars they have been observed since autumn 1968 
photographically with a Schmidt camera mainly in m_R (magnitudes
similar to R of W. Becker) as well as in V (and in B, when
possible). By now, some conclusions can be made.
      CIT 5 = Do 259 = IRC +50096 (7) had two flat maxima,
m_R = 10.1m, and one minimum, m_R = 11.7m. The range of changes
in V was from 11.8m to 14.1m. In B the star was fainter than
the plate limit (18m-19m) even at maximum light, thus
B-V > 6m. The cycle of light variations was about 550d. The
star probably belongs to the variables of Mira Ceti type.
If so, it is a carbon star of this type of variability 
possessing the longest period known.
     CIT 13 = Do 228 = CSVS 5438 (6) = IRC +40485 had
two minima, m_R ~ 11.5m, V ~ 13.5m, and one maximum, m_R = 9.5m
at J.D. 2440457. Its colour indices at J.D. 2440586 were
B-V ~ 5m, V-m_R = 1.7m. The cycle of variations of CIT 13 is
about 470d. Such a period of variability contradicts neither
the few observations of K-magnitudes published in (1,2,7)
nor the early two observations given in (4). The star evidently
is of Mira Ceti type. The light of CIT 13 is now increasing,
somewhat slower, however, than in the previous cycle, and will
reach its maximum in December 1970.
      The results of observations for both stars in magnitudes
m_R are given in the Figure.

			[FIGURE 1]

Radioastrophysical Observatory
Latvian Academy of Sciences              Z. ALKSNE
October 22, 1970                         A. ALKSNIS


References
1. B. T. Ulrich, G. Neugebauer, D. McCammon, R. B. Leighton,
   E. E. Hughes, E. Becklin, 1966, Ap. J. 146, 238 [BIBCODE 1966ApJ...146..288U ] 
2. W. Z. Wisniewski, R. F. Wing, H. Spinrad and H. L. Johnson,
   1987, Ap. J. 148, L 29 [BIBCODE 1967ApJ...148L..29W ]
3, P. Pesch, 1987, Ap. J. 149, L 65 [BIBCODE 1967ApJ...149L..65P ]
4. O. J. Lee, T. J. Bartlett, 1945, Ann. Dearborn Obs., 5, P.3
5. O. J. Lee, G. D. Gore, T. J. Bartlett, 1946, Ann. Dearborn
   Obs., 5, P. 7.
6. B. V. Kukarkin, P. P. Parenago, Yu. I. Efremov, P. N. Kholopov,
   1951, Catalogue of Suspected Variable Stars, Moscow. [BIBCODE 1951CSV...C......0K ]
7. G. Neugebauer, R. B. Leighton, 1969, Two-Micron Sky Survey,
   A Preliminary Catalogue, NASA SP-3074, Washington. [BIBCODE 1969tmss.book.....N ]