Upsilon Ursae Majoris

Upsilon Ursae Majoris, Latinized from υ Ursae Majoris, is a binary star^[12] in the northern circumpolar constellation of Ursa Major. It is visible to the naked eye with an apparent visual magnitude of +3.79.^[4] Based upon an annual parallax shift of 13.24 mas,^[1] it is located roughly 246 light-years from the Sun.

A light curve for Upsilon Ursae Majoris, plotted from TESS data^[13]

Upsilon Ursae Majoris

Location of υ Ursae Majoris (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Ursa Major
Right ascension	09h 50m 59.35700s[1]
Declination	+59° 02′ 19.4486″[1]
Apparent magnitude (V)	3.68 – 3.86[2]
Characteristics
Spectral type	F2 IV[3]
U−B color index	+0.09[4]
B−V color index	+0.29[4]
Variable type	δ Sct[2]
Astrometry
Radial velocity (Rv)	27.3±4.1[5] km/s
Proper motion (μ)	RA: +42.97[1] mas/yr Dec.: −23.62[1] mas/yr
Parallax (π)	28.06±0.20 mas[1]
Distance	116.2 ± 0.8 ly (35.6 ± 0.3 pc)
Absolute magnitude (MV)	+1.11[6]
Details
υ UMa A
Mass	1.57[7] or 2.20[3] M☉
Radius	2.79±0.40[8] R☉
Luminosity	29.5[9] L☉
Surface gravity (log g)	3.79±0.14[7] cgs
Temperature	7,211±245[7] K
Rotation	1.2±0.30 d[8]
Rotational velocity (v sin i)	124.2[10] km/s
Age	1.168[7] Gyr
υ UMa B
Mass	0.44[3] M☉
Other designations
υ UMa, WDS J09510+5902[11]
A: 29 Ursae Majoris, BD+59°1268, FK5 368, HD 84999, HIP 48319, HR 3888, SAO 27401[11]
Database references
SIMBAD	data

The primary member of the system, component A, is an F-type subgiant star. It is a Delta Scuti variable^[8] with a period of 0.1327 day and an amplitude of 0.050 magnitude.^[14] With an estimated age of 1.168^[7] billion years, it is spinning rapidly with a projected rotational velocity of 124.2 km/s^[10] and a rotation period of 1.2 days.^[8] The star has about 1.57^[7] times the mass of the Sun and 2.79^[8] times the Sun's radius. (De Rosa and colleagues give a mass estimate of 2.2^[3] times the Sun's mass.) It is radiating around 29.5^[9] times the solar luminosity from its outer atmosphere at an effective temperature of 7,211 K.^[7]

The companion, component B, is a magnitude +11.0 star.^[12] As of 2008, it has an angular separation of 11.78 arcseconds along a position angle of 295.4°. This corresponds to a projected separation of 419.8 AU.^[3] It has a mass around 40% that of the Sun.^[3]

Naming

With τ, h, φ, θ, e and f, it composed the Arabic asterism Sarīr Banāt al-Na'sh, the Throne of the daughters of Na'sh, and Al-Haud, the Pond.^[15] According to the catalogue of stars in the Technical Memorandum 33-507 - A Reduced Star Catalog Containing 537 Named Stars, Al-Haud were the title for seven stars : f as Alhaud I, τ as Alhaud II, e as Alhaud III, h as Alhaud IV, θ as Alhaud V, this star (υ) as Alhaud VI and φ as Alhaud VII .^[16]

In Chinese, 文昌 (Wén Chāng), meaning Administrative Center, refers to an asterism consisting of υ Ursae Majoris, φ Ursae Majoris, θ Ursae Majoris, 15 Ursae Majoris and 18 Ursae Majoris. Consequently, the Chinese name for υ Ursae Majoris itself is 文昌一 (Wén Chāng yī, English: the first Star of Administrative Center.).^[17]