b Persei (which is not the same as beta Persei, Algol) is an exciting triple star system with a hierarchical structure. The main part of the system is made up of two stars that orbit without eclipsing each other, but because they are so close together they produce ellipsoidal variations of 0.06 magnitudes in the light we receive from the system with a period of 1.53 days. But the AAVSO has discovered that a third star produces eclipses with the main binary system. These eclipses can be primary (the third star partially blocks the light we receive from the binary system) or secondary (the binary system partially or totally blocks the third star).
Last September 2022 a secondary eclipse occurred and a team of astronomers (Dr. Donald F. Collins (AAVSO), Dr. Robert Zavala (US Naval Observatory, Flagstaff Station), Jason Sanborn (Lowell Observatory), and Dr. Anatoly Miroshnichenko (University N. Carolina, Greensboro) requested observers to follow it. The duration of the eclipse, which was several days long, required coverage of the phenomenon in different time zones.
Between 18 and 29 September I made more than 400 photometer measurements, in fact every night when the weather permitted, capturing continuous series throughout the night. The aim of the measurements was, on the days before and after the eclipse, to determine the ellipsoidal light curve, and during the eclipse itself to capture as much of the eclipse as possible.
The following graph shows the result of the campaign, indicating the participating observers (in my case J DeElias). The solid line is the experts' deduction of the ellipsoidal light curve. The secondary eclipse is clearly visible with an extra dip of the order of a tenth of a magnitude.
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