Anthony Mallama

Light curve model for the Galilean satellites during Jovian eclipse

Abstract A model for the light curve of a Galilean satellite eclipsed by Jupiters shadow is developed. This model allows center-of-figure information on the satellites position to be derived from photometric eclipse data. The major features of the model are the satellite-Jupiter-Sun-Earth geometry, limb-darkening and albedo features of the satellite, and refraction of light in the Jovian atmosphere. Sample output from the model reveals that tens of seconds may elapse between the time of half-phase in the eclipse and that of half-luminosity of the satellite. The model fits eclipse photometry to less than 1% rms luminosity. Furthermore, much of the scatter in O − C (observed minus calculated) residuals, for eclipse times compared to modern ephemeris predictions, is reduced when the model is used to correct the times of half-luminosity to half-phase.

Detection of very high altitude fallout from the comet Shoemaker-Levy 9 explosions in Jupiter's atmosphere

A comparison between visible light charge-coupled device (CCD) photometry and model light curves for several Jovian satellite eclipses reveals that significant attenuating material was present in Jupiters atmosphere up to about 300 km (relative to the 1-bar pressure level) over the comet Shoemaker-Levy 9 impact sites a month after the explosions occurred.

MINIMA AND PHOTOMETRY FOR SOUTHERN HEMISPHERE ECLIPSING BINARIES.

Photoelectric data for ten prominent systems are reported in this paper. The heliocentric tisnes of minimum determined from V and B observations, respectively, were at JD hel. 2444400 plus the following: DW Aps 29.8()05, .7984; V379 Ceo 34.5381, .5377; RS Cha 28.8047, .8037; RZ Cha 40.5973, .5979; YZ Cha 34.7244, .7240; BW Cha 32.6317, .6319; RW CrA 35.5945, .5946; Phe 28.8690, .8687; RS Sgr 31.6083, .6087; and HO Tel 29.7676, .7686.

Photoelectric light curve and period study for RZ Draconis

Photoelectric observations in V and B are presented. The magnitudes and color indices at the four phases of principal interest are V = 11m.01, (B-V) = 0m.31 at phase 0.0; V = 10m.14, (B-V) = 0m.25 at phase 0.25; V = 10m.38, (B-V) = 0m.25 at phase 0.5; and V = 10m.14, (B-V) = 0m.24 at phase 0.75.The (0- C) diagram indicates that the orbital period was constant from the time of the stars discovery as a variable in 1907 until about 1968. At that time the period suddenly decreased by about 2.9 × 10-6 days.The current period is 0d.95508738, and the time of minimum derived from the observations in this paper is JD (hel.) 2444177.5555.

PHOTOMETRY AND PERIOD STUDY OF YY GEM.

Photoelectric observations were made with the 91-cm reflector at NASAs Goddard Space Flight Center in 1979. These show a second-order light variation superposed on the eclipse light curve, such that the maximum at phase 0.75 is brighter than that at phase 0.25 by about 0.06 in V light. The (B-V) color curve is about 0.08 redder at phase 0.0 than at phase 0.5. Two times of secondary minimum light and one time of primary were observed at the following heliocentric Julian Dates: 2443960.6731, 2443969.6277, and 2443949.679, respectively. An analysis of these and other recent timings indicate that the orbital period has remained constant between van Ghents photographic observations in the 1920s and the present time. Implications of these observations are discussed.

BD -6° 4932: A NEW DELTA SCUTI VARIABLE

During the course of photoelectric photometry of the eclipsing binary BS Scuti in 1968, we discovered that our comparison star BD-6°4932 (= HD 174553) was variable (Hall and Mallama 1969). A subsequent photoelectric study of the new variable was begun, the results of which are presented here. Although one purpose of the study was to allow the BS Set observations to be salvaged, this aspect will be dealt with in a separate paper on BS Set.

AUTOMATION OF A COMMERCIAL ASTRONOMICAL TELESCOPE

A computer program for automation of the Meade LX-200 Schmidt-Cassegrain telescope is described. The code has been extensively tested and observations have been obtained. The telescope automation program is available in the C and Basic programming languages, along with complete documentation.

Eclipses of Saturn's moons

CCD photometric data for eclipses of Tethys, Dione, and Rhea are fit to model light curves that represent the geometry and radiometry of the events. Comparison of our midevent timings with modern ephemerides indicates that the predictions are typically accurate to about 300 km. We also present results from our model that allow eclipse and occultation photometry of Mimas through Phoebe to be used for precise astrometry of those satellites.