59 Serpentis

59 Serpentis, also known as d Serpentis, is a multiple star in the constellation Serpens. The system shows irregular variations in brightness between magnitudes 5.17 and 5.29.

Components
59 Serpentis appears as a close pair of stars, of 5th magnitude and 7th magnitude respectively, separated by four arc-seconds. The brighter of the two is itself an even closer binary with the two stars separated by only $0.2 "$, and only $0.1 "$ when they were first detected. The stars are designated Aa, Ab, and B.

The primary star, component Aa, is a G0 giant. Component Ab is spectroscopic binary with a period of 1.85 days; the two stars are very similar A-class main sequence stars. Component B is an F5V possible astrometric binary, but with little known about the orbit or the possible companion.

A much fainter star $20 "$ away is also thought to be a member of the system, having a common proper motion and similar Gaia parallax, and is designated as component C.