Upsilon Ursae Majoris
Binary star in the constellation Ursa Major
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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.
  | |
| 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]