COMMISSIONS 27 AND 42 OF THE IAU 
            INFORMATION BULLETIN ON VARIABLE STARS 
                         Number 3773 
 
                                          Konkoly Observatory 
                                          Budapest 
                                          21 September 1992 

                                          HU ISSN 0374 - 0676 
 
 
          A NEW SUPERGIANT VARIABLE: HD 186841 (B1 Ia) 
 
 
 A large number of supergiants show optical variations (see e.g. 
Maeder 1980, Percy & Welch 1983). Several of them have been observed 
with the 1-m and 50-cm telescopes of Konkoly Observatory in 
Piszkesteto in order to search for light variation. The 
variability of two supergiants has already been reported (Zsoldos 
1990). 
 
 HD 186841 is a B1 supergiant in the Vul OB1 association (Humphreys 
1978). It was observed earlier by Hiltner (1956), The & van Paradijs 
(1971) and Fernie (1983). These observations do not indicate any 
light variation except for the two V-I and V-R measurements of Fernie 
(1983, 1992) which differ by 0.1 mag. 
 
 HD 186841 was observed between 1983 and 1987 in the UBV-system. The 
observations were made relative to HD 186379 (V=6.85m; B-V=0.62m; 
U-B=0.01m ) and BD+23d3759 (V=8.77m; B-V=0.77m; U-B=-0.34m) was 
the check star except for the first measurement in Table I where 
BD+23d3759 was the comparison. The observations are given in Table I. 
The average errors are 0.007m in V, 0.010m in B-V and 0.013m in 
U-B. 
 
 
                               Table I 
                      Observations of HD 186841 
 
                    J.D.      V       B-V       U-B 
              2440000+ 
                 5536.459    7.890    0.817    -0.302 
                 6159.590    7.900    0.796    -0.291 
                 6181.526    7.906    0.805    -0.302 
                 6196.539    7.924    0.819    -0.327 
                 6315.378    7.862    0.801    -0.303 
                 6678.368    7.839    0.824    -0.299 
                 6985.432    7.898    0.788    -0.362 
 
 
 The light and colour curves of HD 186841 are plotted in Fig. 1. 
Though the observations listed in Table I are rather sporadic, they 
clearly show the variation in V. The P-L-relation of Maeder (1980) 
predicts a period of about 4 days (log T_eff = 4.32 and M_bol = 
-8.6 was used (Peppel 1984)). There is, however, no possibility to 
check this prediction since the number of observations is low. The 
amplitude in V is about 0.07m which is the expected value for a B 
supergiant (Maeder 1980). There are marked colour changes, too, 
though they do not necessarily follow the course of the variation in 
V. 
 

                            [FIGURE 1]

        Figure 1. The light and colour curves of HD 186841


 This research has made use of the Simbad database, operated at CDS, 
Strasbourg, France. 

 
                      E. ZSOLDOS 
                      Konkoly Observatory 
                      Budapest XII, P.O.Box 67 
                      1525 Hungary 
 
 
 
References: 
 
Fernie J.D. 1983, Astrophys. J. Suppl. 52, 7  [BIBCODE 1983ApJS...52....7F ]
 
Fernie J.D. 1992, personal communication 
 
Hiltner W.A. 1956, Astrophys. J. Suppl. 2, 389  [BIBCODE 1956ApJS....2..389H ]
 
Humphreys R.M. 1978, Astrophys. J. Suppl. 38, 309  [BIBCODE 1978ApJS...38..309H ]
 
Maeder A. 1980, Astron. Astrophys. 90, 311  [BIBCODE 1980A&A....90..311M ]
 
Peppel U. 1984, Astron. Astrophys. Suppl. 57, 107  [BIBCODE 1984A&AS...57..107P ]
 
Percy J.R., Welch D.L. 1983, Publ. Astron. Soc. Pacific 95, 491  [BIBCODE 1983PASP...95..491P ]
 
The P.S., van Paradijs J.A. 1971, Astron. Astrophys. 13, 274  [BIBCODE 1971A&A....13..274T ]
 
Zsoldos E. 1990, Inf. Bull. Var. Stars No. 3525