COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     Number 1352

                                  Konkoly Observatory
                                  Budapest
                                  1977 October 19




        HR 4665: A NEWER, BRIGHTER RS CVn BINARY




    The recent discovery of the interesting characteristics of
HR 1099 = V711 Tau (Bopp and Fekel, 1976; Bopp, Espenak, Hall,
Landis, Lovell and Reucroft, 1977; Owen, 1976) has given observers
a bright (V ~5.8m) readily accessible RS CVn binary that can be
studied in many different wavelength regions. To further aid 
satellite-UV observers, radio astronomers, and high dispersion 
spectroscopists, we have discovered a brighter RS CVn binary: HR 4665
(V ~ 5.4m according to the 1964 Yale Bright Star Catalogue).
    HR 4665 is listed by Bidelman (1954) as a spectroscopic
binary with CaII emission. Several spectra obtained by Young
(1945) had indicated a velocity variation of ~ 30 km/sec.
Spectroscopic observations by Doty (1975) with the 1-meter Ritter 
Observatory reflector revealed the Ca II H and K reversals to be 
exceptionally strong. In addition, his spectra (dispersion 30 Angstrom/mm)
exhibited variable line widths suggesting a double-line spectroscopic 
binary. Subsequent coude spectra (dispersion 8 Angstrom/mm) 
obtained at McDonald Observatory confirmed the suspected line 
doubling. On these high dispersion blue spectra the absorption lines
of both components are narrow, with approximately equal intensity.
Ca II emission is present in both components. The spectral types
are near K0. A few observations of the red region obtained at
Ritter show Halpha as a normal absorption feature. A spectroscopic
orbit has not yet been determined, but an orbital period in the
range 10d to 20d is suggested by the data.
    Recent photoelectric photometry at two observatories has
revealed the optical variability of HR 4665. Using the 60-cm
Cassegrain reflector at Dyer Observatory, Henry obtained 90 
differential V observations on 28 nights between JD 2,443,260 and
2,443,387. With his 20-cm Newtonian reflector Landis obtained 11
observations in the V on 5 nights from JD 2,443,316 to 2,443,335.
All observations were made with respect to the comparison star
HR 4659 and corrected for differential atmospheric extinction.
Nightly extinction coefficients were used whenever possible 
because of the rather wide angular separation of the variable and
the comparison (about 2degrees) and the large hour angles at which many
of observations were made. In addition, the observations were
transformed to V of the UBV system, but the corrections involved
were very small since Delta(B-V) is only -0.04m. As a check on the
constancy of the comparison star, HR 4740 was observed differentially 
with respect to HR 4659 on 5 nights by Henry. The resulting 
mean difference was DeltaV=0.613m, with a standard deviation of
+-0.007m for a single observation about that mean.
    Nightly means of the differential magnitudes of Henry and
Landis are plotted in the Figure as closed circles and open circles, 
respectively; Delta is in the sense variable minus comparison.

                          [FIGURE 1]

The uncertainties of these nightly means probably fall in the
range +-0.005m to +-0.015m. Although there are gaps in the light
curve, the simplest interpretation yields a photometric period
in the range 60d to 70d and an amplitude from maximum to minimum
of 0.08m.
    Since it seems that the photometric period and the spectroscopically 
determined orbital period are considerable different,
HR 4665 resembles lambda And (Landis, Lovell, Hall, and Henry, 1977)
more so than it does HR 1099. In lambda And the orbital period is
20.5d and the photometric period is in the range 48d to 57d. If
the orbital period of HR 4665 turns out to be greater than 14
days, it would not strictly be an RS CVn binary but would be a member 
of the long period group defined by Hall (1976).

    We are preparing to obtain additional observations of
HR 4665, both spectroscopic and photometric, as soon as it again
becomes observable in the sky.




        BERNARD W. BOPP              FRANCIS FEKEL, Jr.
        Ritter Observatory           Department of Astronomy
        University of Toledo         University of Texas
        Toledo, Ohio 43606           Austin, Texas 78712
 
        DOUGLAS S. HALL              HOWARD J. LANDIS
        GREGORY W. HENRY             Landis Observatory
        Dyer Observatory             2395 Wood Hill Lane
        Vanderbilt University        East Point, Georgia 30344
        Nashville, Tennessee 37235
 



References:

Bidelman, W.P. 1954, Astrophys.J.Suppl. 1, 175 [BIBCODE 1954ApJS....1..175B ]
Bopp, B.W. and Fekel, F. 1976, Astron.J. 80, 771 [BIBCODE 1976AJ.....81..771B ]
Bopp, B.W., Espenak, F., Hall, D.S., Landis, H.J., Lovell, L.P.,
    Reucroft, S. 1977, Astron.J. 82, 47 [BIBCODE 1977AJ.....82...47B ]
Doty, E. 1975, Master's Thesis, University of Toledo
Hall, D.S. 1976, I.A.U. Colloq. No. 29, part I, 287 [BIBCODE 1976ASSL...60..287H ]
Landis, H.J., Lovell, L.P., Hall, D.S., Henry, G.W. 1977,
    Bull.Am.Astron. Soc. 9, 351 [BIBCODE 1977BAAS....9..351L ]
Owen, F.N. 1976, I.A.U. Circ. No. 2929 [BIBCODE 1976IAUC.2929....2O ]
Young, R. 1945, Pub. David Dunlap Obs. 1, 1 [BIBCODE 1945PDDO....1..311Y ]