CN Boötis (HD 124953, HR 5343), or simply CN Boo, is a white-hued variable star in the northern constellation of Boötes. With an apparent magnitude of 5.957, it can be faintly seen from Earth by the naked eye, just south-southwest of the much brighter Arcturus. It is located at a distance of 150.7ly according to Gaia EDR3 parallax measurements, and is receding at a radial velocity of . It is a member of the Ursa Major Stream, a group of stars with similar velocities that all formed around 300 million years ago.
CN Boo is a late A-type star with an effective temperature of 7388K, and has been classified as either a main-sequence star (spectral type A8V/A9V) or a giant star (spectral type A8III). A 2023 estimate places its radius at a modest 1.6, which seems to suggest the former.
The star was known to be an Am star since at least 1964, when the Bright Star Catalogue classified it as such. It was first discovered to be a δ Scuti variable in 1979 by Costa et al., with a period of 0.04d and an amplitude of 0.03 mag. This went against the notion that main-sequence Am stars do not pulsate, something that was accepted as fact at the time, so the team considered the Am classification to be erroneous. A more recent study, however, accepts CN Boo as a pulsating Am star, since it shows a metal abundance pattern archetypal of Am stars, and has a minimum rotation speed (82 km/s) that allows for diffusion processes that cause Am characteristics.
In 1991, CN Boo was found to be a soft X-ray source, meaning that the X-rays it emits are of lower energies, i.e., longer wavelengths. It radiates energy at a rate of 2 ergs per second in X-rays, chiefly at an energy range of below 0.5 keV (wavelength >2.48 nm).
The 1991 edition of the Bright Star Catalogue lists CN Boo as a potential spectroscopic binary. A 2008 study, however, did not detect significant radial velocity variations or any signals of the companion star in the spectrum of CN Boo, meaning that if a secondary star exists, it likely has a flux below 5% that of the primary star.