15 Ursae Majoris
15 Ursae Majoris is a star in the northern circumpolar constellation Ursa Major, located 94 light-years away from the Sun. It has the Bayer designation f Ursae Majoris; 15 Ursae Majoris is the Flamsteed designation. It is visible to the naked eye as a white-hued star with an apparent visual magnitude of 4.46. 15 Ursae Majoris is a suspected member of the Castor stellar kinematic group, a 200-million-year-old association of co-moving stars.
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Ursa Major |
| Right ascension | 09h 08m 52.25763s |
| Declination | +51° 36′ 16.7330″ |
| Apparent magnitude (V) | 4.46 |
| Characteristics | |
| Spectral type | kA3VmF5IIISr |
| B−V color index | 0.288±0.013 |
| Astrometry | |
| Radial velocity (Rv) | −0.1±0.7 km/s |
| Proper motion (μ) | RA: −136.33 mas/yr Dec.: −32.60 mas/yr |
| Parallax (π) | 34.70 ± 0.24 mas |
| Distance | 94.0 ± 0.7 ly (28.8 ± 0.2 pc) |
| Absolute magnitude (MV) | 2.16 |
| Details | |
| Mass | 1.86 M☉ |
| Radius | 1.3 R☉ |
| Luminosity | 11.31 L☉ |
| Surface gravity (log g) | 3.77±0.08 cgs |
| Temperature | 7,519±98 K |
| Metallicity [Fe/H] | 0.55±0.05 dex |
| Rotational velocity (v sin i) | 42 km/s |
| Age | 220 Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
According to Eggleton and Tokovinin (2008), this is a suspected binary star system with an orbital period of 4.9 days and an eccentricity of 0.2. However, De Rosa et al. (2014) did not find a companion. The primary is metallic-lined (Am) star, meaning it has unusually strong absorption lines of metals in its spectrum. Classification of the spectrum is difficult due to the peculiarities. An MK classification of 15 UMa using the calcium K line is A3 V, but using metallic spectral lines it can appear as a cooler and more luminous star. Spectral lines in the blue region give a classification of F5 Ib, while in the violet region the lines suggest F5 III/IV.