COMMISSION 27 OF THE I.A.U.
              INFORMATION BULLETIN ON VARIABLE STARS
                           Number 1411

                                                     Konkoly Observatory
                                                     Budapest
                                                     1978 April 5


       UBV OBSERVATIONS OF HR 1099 ON FEBRUARY 22nd, 1977

Alerted by telephone calls from D. Fraquelli (University of Toronto)
and D.S. Hall (Vanderbilt University) that a radio flare was in progress,
we observed HR 1099 in optical wavelengths at the first opportunity with the
41-cm telescope at the RAO. The photometer was equipped with a DCO2-cooled,
selected EMI 6256 PMT operated at - 1200V. Although the night was not of the
highest quality and no night extinction and transformation coefficients were
obtainable, mean coefficients appear to satisfy the observations adequately.
The (Hardie) coefficients employed were: k_y' = 0.156, k_by' = 0.098,
k_ub' = 0.271, k_y" = 0.00, k_by" = -0.03, k_vb" = 0.00, epsilon = -0.026,
mu = 1.002, psi = 1.004. HR 1099 and its visual companion were observed
together using a 30 arc-sec diaphragm.
   Differential observations relative to the comparison star, 10 Tau, are
given in Table I. Phases were computed using the ephemeris of Bopp et al.
(1977).


       TABLE I - DIFFERENTIAL OBSERVATIONS OF HR 1099

JD hel         phi        dV    d(B-V)   d(U-B)  DeltaX    X
2443561+

 0.6486      278.7346    1.55    0.38     0.39   -0.007   2.018
 0.6621         .7394    1.59    0.33     0.43   -0.007   2.086
 0.6663         .7408    1.57    0.33     0.44   -0.007   2.144
 0.6757         .7442    1.57    0.35     0.42   -0.008   2.277
 0.6809         .7460    1.58    0.32     0.44   -0.008   2.376
 0.6897         .7491    1.53    0.36     0.42   -0.009   2.515
 0.6946         .7508    1.51    0.39     0.40   -0.009   2.616

   X is the air mass of the variable star and deltaX is the difference in air
mass between the variable and comparison stars at the instant of the variable
star observations. The mean standard errors of five comparison star
observations were found to be +- 0.019, +- 0.009, and +- 0.010 in V, 
(B-V), and (U-B) respectively.
   The results appear to be fainter than those reported by Bopp et al (1977)
for the same phase, but a secular variation of the phase is suspected; the
results are in fact consistent with Bopp et al's minimum-light data. In
light of the reports that HR 1099 is an x-ray variable (Walter, Charles and
Bowyer: 1978) and has been producing very high intensity ratio levels
(Feldman, et al, 1978 and Feldman, 1978) observations at all wavelengths are
evidently desirable.


                                        E.F. MILONE
                                        R. M. ROBB

                                   Rothney Astrophysical Observatory
                                   The University of Calgary
                                   Canada


References:

Bopp, B.W., Espenak, F., Hall, D.S., Landis, H.J., Lovell, L.P.
   and Reucroft, S: 1977, Astron. J. 82, 47. [BIBCODE 1977AJ.....82...47B ]
Feldman, P.A., Gregory, P.C., Taylor, A.R., and Seaquist, E.R.: 1978,
   IAU Circ. 3176. [BIBCODE 1978IAUC.3176....1F ]
Feldman, P.A.: 1978, IAU Circ. 3180. [BIBCODE 1978IAUC.3180....3F ]
Walter, F., Charles, P., and Bowyer, S.: 1978, IAU Circ. 3173. [BIBCODE 1978IAUC.3173....3W ]