COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 2389

                                 Konkoly Observatory
                                 Budapest
                                 22 August 1983

                                 HU ISSN 0374-0676


           HR 5 = ADS 61: A NEW VARIABLE STAR


   We obtained differential photoelectric photometry of the bright (V =
6.0m) visual binary HR 5 = ADS 61 in late 1981 and in late 1982 at five 
different observatories, finding it to be variable with a period of 1.08d. All
observers used HD 225257 as the comparison star.
   Fried observed with the 16-inch at Braeside Observatory in Flagstaff,
Arizona. Brettman observed with the 10-inch at the Braeside-Midwest Observatory 
in Huntley, Illinois. DuVall observed with the 16-inch at the Modine-
Benstead Observatory in Racine, Wisconsin. Poe observed with the 24-inch
at Dyer Observatory in Nashville, Tennessee. Shaw observed with the 24-
inch at the University of Georgia Observatory in Athens, Georgia. Poe 
observed in V and B of the UBV system. Shaw observed in the five bandpasses
of the Washington photometric system, which includes ultraviolet (c), blue
(m), visual (v), red (T1), and infrared (T2). All of the others observed
only in the V of the UBV system.

                            [FIGURE 1]

   Figure 1  Differential visual magnitudes on 11 nights observed at the
   Braeside and Braeside-Midwest Observatories. Phase is computed with
   the period 1.082d. Zero phase correspond to JD 2444900.0

   Analysis of the Braeside and Braeside-Midwest data, including observations 
on 11 nights between JD 2444901.7 and 2444948.7, indicated a period
of 1.082d +- 0.002d. Fourier analysis of that light curve, shown in Figure 1,
with a sine-curve fit indicated a total amplitude of DeltaV = 0.066m +- 0.012m.
Zero phase in that light curve is placed arbitrarily at JD 2444900.0 but
the Fourier analysis indicated a minimum at 0.592P  0.036P, which corresponds
to 2444915.79 +- 0.04d.
   Shaw observed only on two consecutive nights, shown in Figure 2, but
those two nights defined a minimum very clearly at JD 2445270.66 +- 0.01d.
Because the two minima thus determined are separated by almost precisely
328 cycles, it seems that cycle count has not been lost. This lets us take
advantage of the long baseline between the two years and refine the period
to 1.0819d +- 0.0001d. If the separation was 327 or 329 cycles, however, the
implied period would be 1.085d or 1.079d, both marginally consistent with the
1981 determination of 1.082d +- 0.002d.

                            [FIGURE 2]

   Figure 2  Differential visual magnitudes on two consecutive nights 
   observed at the University of Georgia Observatory. Phase is the same as
   in Figure 1. Crosses are the first night, circles are the second.

   Although Shaw's photometry evidently did not cover the full range of
the light variation, we can say how the amplitude depends on wavelength.
The ratios in the sense ultraviolet : blue : visual : red : infrared are
1.41 : 0.99 : 1.00 : 0.74 : 0.48, respectively. Thus we see that, compared
to the infrared, the variation is about twice as large in the visual and
about three times as large in the ultraviolet.
   The comparison star HD 225257 is a good choice in that it is only a
few arcminutes away from the variable. The color match, however, is not
good, with Poe's photometry showing Delta(B-V) = +0.64m. The data plotted in
Figures 1 and 2 have not been transformed to V of the UBV system, but that
is not important here since they have been used primarily to determine the
period.
   According to Lippincott (1963) HR 5 = ADS 61 is a visual binary with
a semi major axis of 1'43 and an orbital period of 106.83 years. The two
components are dG4 and dG8, differing in visual magnitude by 0.75m. She
derived a total mass of 2.8 +- 0.6 M_Sun. According to the Fourth Edition of
the Yale Bright Star Catalogue, HR 5 is of additional interest in that an
invisible companion may be orbiting the dG8 component with a period of 6.9
years. Since both the dG4 and the dG8 components were measured together in
our photometry, we have no way of knowing which one is responsible for the
1.08-day variability we have discovered. Spectroscopic observations may
help determine the mechanism for the photometric variability. One of the
two stars may be a rapidly-rotating unevenly-spotted star, or one of the two
may be a spectroscopic binary with an orbital period of 1.08d.
                                 



ORVILLE H. BRETTMAN            DOUGLAS S. HALL
Braeside-Midwest Observatory   CLINT H. POE
Huntley, Illinois              Dyer Observatory
                               Vanderbilt University
ROBERT E. FRIED                Nashville, Tennessee
Braeside Observatory
Flagstaff, Arizona             J. SCOTT SHAW
                               Department of Physics and Astronomy
WILLIAM M. DUVALL              University of Georgia
Modine-Benstead Observatory    Athens, Georgia
Racine, Wisconsin




Reference :

Lippincott, S. L. 1963, A.J. 68, 45. [BIBCODE 1963AJ.....68...45L ]