Spectroscopic Binary 1 Persei

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The variable star 1 Persei is located near the boundary of Cassiopeia in the northeastern corner of Perseus. This binary system has a rich history that began at the Mount Wilson Solar Observatory using the 60-inch reflector outfitted with a three-prism spectrograph (The three-prism stellar spectrograph of the Mount Wilson Solar Observatory, Walter S. Adams, Astrophysical Journal 35, 1912, pp. 163-182). The spectrograph was tasked to investigate radial velocities of selected stars with magnitudes between 4.4 and 6.4. There were 19 A stars, 30 B stars, and  2 O stars found to have variable radial velocities. The velocity for 1 Persei ranged from +77 km/s to -23 km/s. The reason for the variable velocities would not be solved for several decades.

In 1975, photometric measurements were made using the Volksphotometer and reflectors at the University of Texas McDonald Observatory (The photometric variability of 1 Persei, Donald W. Kurtz, Publications of the Astronomical Society of the Pacific 89, 1977, pp. 939-940). Kurtz concluded that 1 Persei was likely an eclipsing binary with the usual primary and secondary eclipses.

In April 2018, the Transiting Exoplanet Survey Satellite (TESS) was launched using the SpaceX Falcon 9 medium-lift launch vehicle. Its mission was to discover exoplanets orbiting around bright dwarf stars (Transiting Exoplanet Survey Satellite, Journal of Astronomical Telescopes, Instruments, and Systems, George R. Ricker et al., 11(1), 2015, pp. 014003-1 to 014003-10). The light curves produced by TESS could also be used to study pulsations in eclipsing binary systems with high-mass stars. A study was carried out by John Southworthy and Dominic M. Bowman in the UK and Belgium, respectively, on 18 such stars, one of them being 1 Persei (High-mass pulsators in eclipsing binaries observed using TESS, John Southworth and Dominic M. Bowman, MNRAS 513, 2022, pp. 3191-3209). As expected, the TESS light curve exhibited one primary and one secondary drop in magnitude with a flat region in between the two. Combining their results with other measurements in the literature, they were able to fully determine the physical properties of the two components such as masses, radii, and effective temperatures.