Gliese 412


Gliese 412 is a binary star system in the constellation Ursa Major. Among the nearest stars, they lie at a distance of. The pair have an angular separation of 31.4″ at a position angle of 126.1°. Both components are relatively dim red dwarf stars.

History of observations

This system, also known as Lalande 21258, was announced in 1860 as a high apparent proper motion star by Friedrich Wilhelm Argelander as a result of work on the Bonner Durchmusterung. Adalbert Krueger, an assistant to the BD project, was tasked with measuring its parallax. In Krueger's paper reporting the result, he dubbed it Argelander's Third Star.
The primary star was monitored for radial velocity variations caused by a Jupiter-mass companion in a short-period orbit. It displayed no significant excess of RV variation that could be attributed to a planet. A search of the system using near-infrared speckle interferometry also failed to detect a companion orbiting at distances of 1–10 AU. Nor has a brown dwarf been detected orbiting within this system.

Characteristics

The two stellar components of this system have a projected separation of about 152 AU, and an estimated orbital semimajor axis of 190 AU.
The primary has 0.387 times the mass of the Sun, 0.398 times the Sun's radius and 2.23% of the Sun's luminosity. It is spinning at a rotation velocity at the equator of less than 3 km/s. The secondary is smaller and fainter, at 9.52% of the Sun's mass, 12.62% of the Sun's radius and luminosity only 0.09% solar. It is spinning at a rotation velocity of km/s. Gliese 412 A has a temperature of 3,639K, while Gliese 412 B has 2,863 K.
The space velocity components of this system are U = 141, V = –7 and W = 7. They are members of the halo population of the Milky Way galaxy.

X-ray source

The secondary is a flare star that is referred to as WX Ursae Majoris. It is characterized as a UV Ceti-type variable star that displays infrequent increases in luminosity. This star was observed to flare as early as 1939 by the Dutch astronomer Adriaan van Maanen.
Component B has been identified as an X-ray source, while no significant X-ray emission was detected from component A. This system had not been studied in X-rays prior to ROSAT.