Worldwide Photometry of the January 1989 τ Persei Eclipse

We present new UBV photoelectric photometry of τ Persei obtained at 19 different observatories during its recent January 1989 eclipse. Mideclipse occurred at JD 2 447 542.31 ± 0d.01. The resulting light curve, though not complete at all phases, is solved for the elements with the help of two quantities derived from spectroscopy: the eclipse is 84% total at mideclipse and the ratio of the radii is 0.135 ± 0.01. Radii relative to the semimajor axis are 0.0236 for the G5 giant and 0.0032 for the A2 star. With a reasonable total mass assumed, the absolute radii say the A2 star could be luminosity class V or somewhat evolved and the G5 star is between III and II but could be closer to II. The G5 giant is brighter than the A2 star by 1m.72 in V and the color excess in B - V is 0m.06, both quantities consistent (within uncertainties) with earlier estimates of Ake. The eclipse duration, from first to fourth contact, is 2d.09. The orbital inclination is 88○.74, consistent with what McAlister derived from speckle interferometry. Because of the large (e = 0.73) eccentricity, there is no secondary eclipse at all