PHOTOMETRY OF RW DRACONIS
AT KONKOLY OBSERVATORY

Seventy years ago Dr. Julia Balázs and Prof. L. Detre started a comprehensive study of RR Lyrae stars (Balázs & Detre, 1938). They paid special attention to the stars that showed light curve variation (i.e. Blazhko effect using modern terminology). One of their program stars was RW Dra. Their early study based on more than 6000 photographic observations has already been published (Balázs & Detre, 1952). Since that time the star has been intensively observed both by photographic and photoelectric methods at the Konkoly Observatory. In this paper we publish these observations. A comprehensive investigation of all published data of RW Dra will be published elsewhere.

The variability of RW Dra was discovered by Ceraski (1906) on Moscow plates and the preliminary name 87.1906 was given the star. Blazhko (1907) carried out the first intensive investigation of the light variation of RW Dra. He determined the star's pulsation period and found the evidence for the phase oscillation of light maximum with a period of 41.6 days. A historically important fact is that S. Blazhko was the very first who recognized long period phase oscillation in an RR Lyrae star (namely in RW Dra itself) and the phenomenon is deservedly called Blazhko effect.

OBSERVATIONS

Photographic observations

Photographic photometry was made at the Konkoly Observatory with the 16 cm astrograph from September 10, 1952 through November 23, 1957 on 95 nights. In the years 1952 and 1953 Eastman 40, and in the subsequent years Guilleminot Superfulgur plates were used with either 3 or 4 min. exposure times depending on the sky condition. The plates were measured with the observatory's Cuffey-type iris photometer. The comparison stars and their magnitudes used were taken from the paper of Balázs and Detre (1952). The 2863 photographic observations obtained are presented in Table 2. The time of the observations are converted to HJD. The estimated error of the observations is 0.05-0.10 magn.

Photoelectric observations in integrated light

The early photoelectric photometry was conducted by L. Detre with the observatory's 60 cm telescope without using any filter. From 1954 an RCA 1P21 photomultiplier tube was employed in the photometer. Although these observations are on an indefinite photometric system, they may be useful in investigating the period changes and the Blazhko effect of RW Dra. The 373 observations published here in the sense variable minus comparison (s. Table 3) were made on 8 nights. The comparison star used was GSC 03885-00893 (=USNO 1425- 08562266), the star labelled e in Balázs and Detre's (1938, 1952) papers.

UBV photometry

The UBV photoelectric observations were carried out with the 60 cm Newton telescope at Budapest from April 24, 1958 till October 15, 1972 and with the 50 cm Cassegrain telescope at Piszkéstetô mountain station between August 3, 1973 and February 11, 1975. Before 1963 the mirror of the 60 cm telescope had a silver coating, and an RCA 1P21 multiplier was employed with Schott filters UG1 in U, BG12+GG13 in B and GG11 in V. Thereafter an EMI 9052 B tube with the same filter combinations as in the previous years was used and the mirror was aluminized. The 50 cm telescope was equipped with an unrefrigerated photometer. This photometer contained an EMI 9058 QB multiplier tube and the colour filters matched closely the UBV system: in ultraviolet light UG2, in blue light BG12+GG13 and in yellow light GG11 Schott filters were used. The observations of the variable were reduced in the usual way. The UT values have been converted to HJD. Correction for atmospheric extinction was not applied as the comparison star is very close to the variable. The instrumental observations have been transformed into the UBV system in the traditional way. The comparison star used during the UBV observations was the same as used in the photoelectric observations in integrated light. During 146 nights between 1958 and 1975 4114 V, 3962 B and 63 U observations were collected. Since the star is too faint for our telescopes, U observations were made only on four nights with the 60 cm telescope. The observations are presented in Tables 4, 5 and 6 in the sense variable minus comparison.

TIMES AND BRIGHTNESS OF LIGHT MAXIMUM

For further studies we determined times and brightness of light maxima from our observations. Although the times of light maximum in B and in V may differ from each other, the difference between them is usually less than or is about the error of their determination. Therefore we give the mean values of the times of B and V light maximum. The brightness of the photoelectrically observed maxima is given in differential magnitudes to the comparison star. We wish to continue the investigation of Balázs and Detre (1952) and therefore we also determined the times of the "middle" (at m=11.5^m) of the ascending branch of the photographic light curves and the times of two points (at {Delta}m=0.0^m and {Delta}m=-0.5^m) on the ascending branch of the photoelectrically observed light curves. The results of the photographic, the white light and the B and V observations are presented in Tables 1a, 1b and 1c, respectively.

ACKNOWLEDGEMENTS

We are grateful to the late director of the Konkoly Observatory, Prof. L. Detre, who made the early photoelectric observations. We would like to express our thanks to the staff of the Konkoly Observatory for having taken share in the observations. Thanks are due to Dr. J. Benko and to Mr. A. Holl for their help in preparing the manuscript. This work was partly supported by the Hungarian OTKA Research Grants No. T-30954 and T-30955.

REFERENCES