COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3361

                                          Konkoly Observatory
                                          Budapest
                                          31 July 1989

                                          HU ISSN 0374 - 0676


 AN IMPROVED PERIOD FOR THE ECLIPSING CATACLYSMIC VARIABLE UU AQUARII


UU Aqr, at alpha=22h06m29s, delta=-4d00'53" (1950.0) was first suggested
to be a semiregular variable, with a period of 66.2 days (Kholopov, 1985).
Stephenson (1986) included it in his list of H_alpha emission stars, giving it
the designation S196. Volkov, Shugarov, and Seregina (1986) (hereafter VSS)
found the star to be an eclipsing cataclysmic variable. They observed the star
over a period of 54 days in 1985, and found the orbital period to be 0.1635806
days, with a zero epoch of HJD 2446347.2667. Downes and Keyes (1988)
published a low-resolution spectrum of UU Aqr. The spectrum is typical for a
cataclysmic variable. Figure 1 is a finder chart for UU Aqr (Photograph (C) 
1960 National Geographic Society- Palomar Sky Survey).

We observed five eclipses of UU Aqr with a two-channel photometer mounted on
the University of Washington's 0.8m. telescope at the Manastash Ridge
Observatory in central Washington. The filter system used approximated the
Johnson V band. The comparison star used was SAO 145900, a 9th magnitude K5
star 7.3 arcminutes from UU Aqr (see Figure 1). The observed eclipses occurred
between September 10 and 18, 1988 UT (HJD 2447414 and HJD 2447422). Our
derived period was consistent, within our timing uncertainty, with that found
by VSS.


                             [FIGURE 1]
                             [FIGURE 2]


By combining our data with that of VSS, we determined that our first eclipse
was within 0.0039 days of the predicted time for epoch 6523. Taking our
uncertainty in the time estimate for minimum light of 0.0003 days and theirs,
estimated at 0.0001 days, we derived an improved ephemeris:

HJD=2446347.2667+E*(0.163579089+-0.000000061) days.

Figure 2 is a representative eclipse. The asymmetry seen on the egress side of
the eclipse, and evident in the VSS light curves, is probably due to the
eclipse of a hot spot on the accretion disk. This asymmetry is similar to that
observed in the UX UMa system by Warner and Nather (1972).

The authors wish to thank George Wallerstein and Paula Szkody, both with the
University of Washington, for helpful comments and discussions.


JEFFREY D. GOLDADER *      PETER GARNAVICH
Department of Astronomy    Department of Astronomy
University of Washington   University of Washington
Seattle, WA 98105          Seattle, WA 98105
USA                        USA

* Present address
University of Hawaii
Institute for Astronomy
2680 Woodlawn Drive
Honolulu, HI 96822
USA

References:

Downes, R. A., and Keyes, C. D., (1988), Astron J., 96, 777 [BIBCODE 1988AJ.....96..777D ]
Kholopov, P. N., ed., General Catalog of Variable Stars, Moscow, "Nauka"
   Publishing House, 1985
Stephenson, C. B. (1986), Astroyhys. J., 300, 779 [BIBCODE 1986ApJ...300..779S ]
Volkov, I. I., Shugarov, S. Yu., and Seregina, T. M. (1986), Astron. Tsirk. No.
   1418, 3 [BIBCODE 1986ATsir1418....3V ]
Warner, B., and Nather, R. E. (1972), Mon. Not. R. Astron. Soc., 159. 420 [BIBCODE 1972MNRAS.159..429W ]