COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1892

                                   Konkoly Observatory
                                   Budapest
                                   1980 December 18

                                   HU ISSN 0374-0676



        PHOTOMETRY OF TWO SUSPECTED LONG PERIOD CEPHEIDS


   Van Genderen and The (1978) show that the G0Ia supergiant HD159378
(=Tr 27-102), a member of the open cluster Trumpler 27, varies in brightness 
and colour with a period of 70 to 90 days.   Since it is situated at
the blue edge of the Cepheid strip it may be a very long period cepheid.
However, its light curve shows minima of unequal depth similar to that
seen in RV Tauri stars.
   Eichendorf and Reipurth (1980) suggest that another G0Ia star, V810
Cen, (= HD101947 = HR5411) may be a cepheid with a period of 125 days.
They find it lies on the blue edge of the instability strip and near the
period-luminosity relation for cepheids.  The phase between the light and
colour variations and the lack of IR excess in JHKL indicate that it is unlikely
to be an RV Tauri, even though it also has unequal minima.
   Both stars were usually monitored once or twice each week spent by the
authors on the 0.5 (or 1.0 metre) telescopes at Sutherland SAAO.  Both
stars were observed by the author in the Cape Kron BVRI system using an
extended S20 phototube.  The observations were transformed to the system
of Cousins (1976) using E region standards, and two "local standards" near
to HR4511, the adopted values for which are given in Table I. Since the
apertures used were in the range, 20" - 33", the faint companion to HD159378
mentioned by van Genderen and The was usually included.
   Several observations of HR4511 were also made in the Johnson UBV
system using S11 phototubes. These were tied to the standards given
in Table I.

   The observations are given in Table II (HR4511) and Table III (HD159378).
                            Table I

Standard   V    B-V  U-B   V-R   V-I
HR 4475 5.140 1.110 1.068 0.558 1.063
HR 4485 5.937 1.022 0.850 0.512 0.986

                 Table II
                 Photometry of HR 4511 
HJD
-2440000 V       B-V    U-B    V-R      V-I
3682.30 5.10     0.85   0.41
3716.25 5.07     0.81          0.46     0.88
3911.57 5.02     0.80          0.46     0.79
3914.54 4.99     0.79          0.46     0.77
3969.41 4.95     0.75          0.42     0.82
3978.50 4.95     0.77          0.42     0.79
3979.43 4.97     0.76          0.44     0.81
4038.32 5.05     0.82          0.46     0.86
4039.27 5.04     0.83          0.46     0.86
4060.29 4.98     0.79          0.44     0.83
4249.59 5.04     0.78          0.42     0.87
4250.59 5.03     0.79          0.42     0.87
4270.58 5.02     0.82          0.44     0.85
4278.62 5.03     0.81   0.42
4279.61 5.04     0.81   0.42
4281.53 5.04     0.81   0.42
4297.45 5.04     0.80          0.45     0.86
4298.57 5.03     0.80          0.44     0.85
4301.53 5.04     0.80          0.45     0.86
4312.46 5.03     0.79   0.41
4368.39 4.96     0.75   0.40
4390.22 4.99     0.75   0.40   0.42     0.82
4391.23 5.00     0.76   0.41   0.42     0.82
4392.24 5.00     0.76   0.41   0.43     0.83
4393.23 5.00     0.76   0.40   0.43     0.82
4422.26 5.09     0.81          0.45     0.87
4424.27 5.08     0.81          0.44     0.85

                 Table III                
            Photometry of HD 159378
HJD
-2440000         V      B-V    V-R      V-I
3970.65          8.50   1.97   1.21     2.39
4036.49          8.53   2.04   1.18     2.39
4039.46          8.52   2.06   1.19     2.39
4059.50          8.48   1.93   1.19     2.38
4060.41          8.45   1.89   1.19     2.37
4094.28          8.40   1.90   1.20     2.34
4096.31          8.37   1.91   1.19     2.33
4099.42          8.36   1.88   1.18     2.32
4114.27          8.35   1.88   1.18     2.33
4115.31          8.36   1.88   1.19     2.33
4422.45          8.46   1.91   1.20     2.32
4423.42          8.45   1.91   1.21     2.33


(a)HD159378 became gradually brighter and bluer between Julian Dates
   244 4037 and 2444115.  There is insufficient data and too large a
   time gap to be able to improve on the periods given by van Genderen
   and The; however the period may exceed 100 days.


(b)   HR4511 appears to have varied irregularly between V= 4.95 and 5.08
   during the period JD 2443910 - 2444423. There is no evidence for
   Eichendorf and Reipurth's period of 125 days. The star is bluest
   at maximum.

  Both these stars appear similar to the superluminous supergiants
HR5171 and 6392 (Dean 1980) in that they show irregular long period
fluctuations. They are thus unlikely to be cepheids.


   I would like to thank Dr J.W.Menzies and Mr J.D.Laing for their UBV
observations of HR4511.





                               J.F. DEAN

                               S.A.A.O.,
                               Observatory
                               Cape
                               South Africa





References:
Cousins, A.W.J., 1976. Mon.Not.R.astr.Soc.S.Africa, 35, 70. [BIBCODE 1976MNSSA..35...70C ]
Dean, J.F., 1980.    I.B.V.S. 1796.
Eichendorf, W. and Reipurth, B., 1979. Astron. Astrophys. 77, 227. [BIBCODE 1979A&A....77..227E ]
Van Genderen, A.M. and The, P.S., 1978. Astron. Astrophys 64, L1. [BIBCODE 1978A&A....64L...1V ]