KS Persei is a

binary system A binary system is a system of two astronomical bodies which are close enough that their gravitational attraction causes them to orbit each other around a barycenter ''(also see Barycenter#Gallery, animated examples)''. More restrictive definitio ...

in the

equatorial Equatorial may refer to something related to: *Earth's equator **the tropics, the Earth's equatorial region **tropical climate *the Celestial equator **equatorial orbit **equatorial coordinate system **equatorial mount, of telescopes * equatorial b ...

constellation of

Perseus In Greek mythology, Perseus (Help:IPA/English, /ˈpɜːrsiəs, -sjuːs/; Greek language, Greek: Περσεύς, Romanization of Greek, translit. Perseús) is the legendary founder of Mycenae and of the Perseid dynasty. He was, alongside Cadmus ...

. It is sometimes known as Bidelman's Star, named after

William P. Bidelman William Pendry Bidelman ( ; September 25, 1918 – May 3, 2011)apparent visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's lig ...

of 7.70. As of 2018, the structure and evolutionary history of this system remain uncertain, although some form of mass transfer is likely to have occurred to explain the observed properties. The peculiar nature of the

spectra Spectra may refer to: * The plural of spectrum, conditions or values that vary over a continuum, especially the colours of visible light * ''Spectra'' (journal), of the Museum Computer Network (MCN) * The plural of spectrum (topology), an object ...

for this star was noted in the '' Henry Draper Catalogue'' and was the subject of a study by W. P. Bidelman published in 1950. He found extremely weak

lines Line most often refers to: * Line (geometry), object with zero thickness and curvature that stretches to infinity * Telephone line, a single-user circuit on a telephone communication system Line, lines, The Line, or LINE may also refer to: Arts ...

of hydrogen, similar to those for

Upsilon Sagittarii Upsilon Sagittarii (Upsilon Sgr, υ Sagittarii, υ Sgr) is a spectroscopic binary star system in the constellation Sagittarius. Upsilon Sagittarii is the prototypical hydrogen-deficient binary (HdB), and one of only f ...

but at a lower temperature. The data strongly suggested the star has an abnormally low abundance of hydrogen in the

stellar atmosphere The stellar atmosphere is the outer region of the volume of a star, lying above the stellar core, radiation zone and convection zone. Overview The stellar atmosphere is divided into several regions of distinct character: * The photosphere, wh ...

. Bidelman noted that the

radial velocity The radial velocity or line-of-sight velocity, also known as radial speed or range rate, of a target with respect to an observer is the rate of change of the distance or range between the two points. It is equivalent to the vector projection ...

of the star is variable, demonstrating that it has an unseen companion. Preliminary

orbital elements Orbital elements are the parameters required to uniquely identify a specific orbit. In celestial mechanics these elements are considered in two-body systems using a Kepler orbit. There are many different ways to mathematically describe the same ...

for this single-lined spectroscopic binary were published in 1955 by J. F. Heard and O. Boshko, giving an

orbital period The orbital period (also revolution period) is the amount of time a given astronomical object takes to complete one orbit around another object. In astronomy, it usually applies to planets or asteroids orbiting the Sun, moons orbiting planets ...

of 359.7 days and with

eccentricity Eccentricity or eccentric may refer to: * Eccentricity (behavior), odd behavior on the part of a person, as opposed to being "normal" Mathematics, science and technology Mathematics * Off- center, in geometry * Eccentricity (graph theory) of a ...

of 0.27. They found a large mass function of 4.5, suggesting that the supergiant has lost mass and the companion is relatively massive. The mass function was revised to 3.6 in 1988, suggesting the secondary is five times more massive than the primary. Although the

Gaia In Greek mythology, Gaia (; from Ancient Greek , a poetical form of , 'land' or 'earth'),, , . also spelled Gaea , is the personification of the Earth and one of the Greek primordial deities. Gaia is the ancestral mother—sometimes parthe ...

parallax is small (and the

Hipparcos ''Hipparcos'' was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial obj ...

parallax is negative), KS Persei is thought to be less than away. Older studies have suggested distances up to . An analysis by G. Wallerstein and associates in 1967 showed that nitrogen is the second most abundant element in the primary, likely as a result of

carbon cycling The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth. Carbon is the main component of biological compounds as well as a major component ...

. G. A. Bakos attempted to photometrically detect an eclipse but was unsuccessful. However, he did tentatively detect semiregular variation with a period of ~30 days and an amplitude of 0.1 magnitude. This variability was confirmed by K. Morrison and G. P. H. Willingale in 1987, and they discovered an additional five day cycle. In 1982, J. S. Drilling and D. Schönberner detected a hot companion from spectra collected by the

International Ultraviolet Explorer International Ultraviolet Explorer (IUE or Explorer 57, formerly SAS-D), was the first space observatory primarily designed to take ultraviolet (UV) electromagnetic spectrum. The satellite was a collaborative project between NASA, the United K ...

. The system is an infrared source, and models of the infrared flux suggest it is being emitted by circumstellar dust heated to . It is possible that the companion is obscured by dust.

References

Further reading