COMMISSIONS 27 AND 42 OF THE IAU 
            INFORMATION BULLETIN ON VARIABLE STARS 
                          Number 3795 
 
                                           Konkoly Observatory 
                                           Budapest 
                                           27 October 1992 
 
                                           HU ISSN 0374 - 0676 
 
 
             A Probable RV Tauri Star Near HR Del 
 
 
   The Indiana University 16-inch automated CCD photometric telescope 
(Honeycutt et al., 1989; 1990; 1992) acquires about 100 exposures each 
clear night, mostly on a program involving nightly monitoring of nova-like 
and SU UMa CV's. The photometric reduction technique used for ensemble 
photometry on inhomogeneous data sets (Honeycutt, 1992) provides, as a 
by-product, the light curve of all stars in the field. 
Consequently, the program is discovering a number of new 
variable stars, one of which is described here.  A 
computer-generated finding chart for the new variable is shown 
in Figure 1. A photographic finding chart of this. same field 
can be found in Duerbeck (1987). The coordinates of the variable 
are 20:42:12, +19:09:22 (2000.0), with an accuracy of about 5 
arc- seconds.  The light curve in Figure 2 shows variations of 
about one magnitude with a complicated behavior. As described in 
Honeycutt (1992), the error bars correctly represent the 
uncertainty of the differential photometry, but the zeropoint of 
the magnitude scale has an uncertainty of about +- 0.2 mag. The 
portion of the light curve beyond JD = 2448700 is quite 
sinusoidal with a best fit 
 
 
              V = V_0 + A*sin(2 pi*(JD-JD_0)/P) 
 
  where V_0 = 14.7 (+- 0.02) mag (+- 0.2 mag including zeropoint error), 
          A = 0.5 (+- 0.02) mag, 
       JD_0 = 2448778 (+- 1) days, 
          P = 97 (+- 1) days. 
 
This sine wave also fits some of the data before JD = 2448700, 
but data near JD = 2448450 are discrepant. 
 

                           [FIGURE 1]

 Figure 1: Finding chart with HR Del and the new variable marked. 
 The field is 7.2 arc minutes on a side.

                           [FIGURE 2]

 Figure 2: V-band CCD photometry of the new variable in the years 
 1990-1992 with a sine curve fit. The arrow marks the time of the 
 spectrum in Figure 3.

                           [FIGURE 3]

 Figure 3. A blue spectrum of the new variable.


  Figure 3 is a blue spectrum of the new variable obtained on 
August 22(UT),1992 with the Ohio State CCD spectrograph on the 
Perkins 1.8-meter telescope of the Ohio Wesleyan and Ohio State 
Universities at the Lowell Observatory. The resolution is 2.5 
Angstroms. The spectrum was obtained through clouds and the S/N 
is consequently poor. Nevertheless, enough features are visible 
to conclusively identify the spectral type as K. The arrow in 
Figure 2 marks the date when the spectrum was obtained.  The 
photometry and spectroscopy are consistent with this star being 
an intrinsic variable of the RV Tauri type (Rosino, 1951; Joy, 
1952; Preston et al., 1963). These stars have periods of 50-150 
days, are of spectral type F,G or K, and usually display 
alternating deep and shallow minima and/or erratic light curve 
variations. The complicated light curves likely arise from more 
than one atmospheric layer in motion, with accompanying 
interactions and shocks (Baird, 1982; Wallerstein and Elgar, 
1992).  HR Del will remain on our observing program, so we 
expect light curve points on this new variable will continue to 
accumulate. 
 
 
R. K. Honeycutt                 J. R. Pier* 
J. W. Robertson 
D. N. Vesper                    U.S. Naval Observatory 
B. D. Kern                      Flagstaff Station 
G. W. Turner                    P.O. 1149 
                                Flagstaff, AZ 86002-1149 
Indiana University              USA 
Astronomy Department 
Swain Hall West 
Bloomington, IN 47405 
USA 
 
   *Visiting Observer, Lowell Observatory, Flagstaff, Arizona 
 
 
References: 
 
Baird, S.R.: 1982, Pub. A.S.P., 94, 850  [BIBCODE 1982PASP...94..850B ]
Duerbeck, H.W.: 1987, Sp. Sci. Rev., 45, 1  [BIBCODE 1987SSRv...45....1D ]
Honeycutt, R.K.: 1992, Pub. A.S.P., 104, 435  [BIBCODE 1992PASP..104..435H ]
Honeycutt, R.K., Adams, B., Grabbhorn, R., Turner, G., White, J., 
  and Vesper, D.: 1989, in Remote Access Automatic Telescopes, 
  eds. D.S. Hayes and R.M. Genet (Mesa, Fairborn), p. 105 
Honeycutt, R.K. Vesper D., Turner, G.W. and Adams, B.: 
  1990, in CCDs in Astronomy II: New Methods and Applications of CCD 
  Technology, eds. A.G.D. Philip, D.S. Hayes 
  and S.J. Adelman (Schenectady, L. Davis), p.177  [BIBCODE 1990ccd2.proc..177H ]
Honeycutt, R.K. and Turner, G.W.: 1992, to appear in Robotic Telescopes 
  in the 1990's, ed.  A. Filippenko (San Francisco, ASP) [BIBCODE 1992ASPC...34...77H ]
Joy, A.: 1952, Ap. J., 115, 25  [BIBCODE 1952ApJ...115...25J ]
Preston, G.W., Krzeminski, W., Smak, J., and Williams, J.A.: 1963, 
  Ap. J., 137, 401  [BIBCODE 1963ApJ...137..401P ]
Rosino, L.: 1951, Ap. J., 113, 60  [BIBCODE 1951ApJ...113...60R ]
Wallerstein, G. and Elgar, S.: 1992, Science, 256, 1531  [BIBCODE 1992Sci...256.1531W ]