Global InformationRR Ursae Minoris information
 A light curve for RR Ursae Minoris, plotted from Hipparcos data[1] | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 14h 57m 35.01625s[2] |
| Declination | +65° 55′ 56.9143″[2] |
| Apparent magnitude (V) | 4.44 - 4.85[3] |
| Characteristics | |
| Spectral type | M4.55 III[4] |
| B−V color index | 1.590±0.017[5] |
| Variable type | SRb[6] |
| Astrometry | |
| Radial velocity (Rv) | 6.21±0.30[7] km/s |
| Proper motion (μ) | RA: −82.191[2] mas/yr Dec.: +26.981[2] mas/yr |
| Parallax (π) | 10.0206 ± 0.6341 mas[2] |
| Distance | 330 ± 20 ly (100 ± 6 pc) |
| Absolute magnitude (MV) | −1.11[5] |
| Orbit[8] | |
| Period (P) | 748.9 d |
| Eccentricity (e) | 0.13±0.05 |
| Inclination (i) | 79.6±2.4[9]° |
| Longitude of the node (Ω) | 48.0±2.5[9]° |
| Periastron epoch (T) | 2,444,419±46 JD |
| Argument of periastron (ω) (secondary) | 212±22° |
| Semi-amplitude (K1) (primary) | 8.3±0.3 km/s |
| Details | |
| Mass | 1.15±0.1[10] M☉ |
| Radius | 59.8+15.1 −3.6[2] R☉ |
| Luminosity | 756.7±54.4[2] L☉ |
| Surface gravity (log g) | 0.00[11] cgs |
| Temperature | 3,464[12] K |
| Other designations | |
AAVSO 1456+66, RR UMi, BD+66°878, FK5 554, HD 132813, HIP 73199, HR 5589, SAO 16558[13] | |
| Database references | |
| SIMBAD | data |
RR Ursae Minoris, abbreviated RR UMi, is a binary star[11] system in the northern circumpolar constellation of Ursa Minor. It can be viewed with the naked eye, typically having an apparent visual magnitude of around 4.710.[9] Based upon an annual parallax shift of 10.0 mas[2] as seen from Earth's orbit, it is located 330 light years away. The system is moving further from the Sun with a heliocentric radial velocity of +6 km/s.[7]
This star was found to have a variable radial velocity by J. H. Moore in 1910. It is a single-lined spectroscopic binary system with an orbital period of 2.05 years and an eccentricity (ovalness) of 0.13. The a sin i value is 84 Gm (0.56 AU),[8] where a is the semimajor axis and i is the orbital inclination to the line of sight from the Earth. This gives a lower bound on the physical size of the orbit. The system is a source for X-ray and far-UV emission, with the latter most likely coming from the companion.[11]
The visible component is an aging red giant star on the asymptotic giant branch[11] with a stellar classification of M4.5 III.[4] It was found to be a variable star by J. Ashbrook in 1946,[14] and is catalogued as a semiregular variable of subtype SRb[6] that ranges from magnitude 4.44 to 4.85 over a period of 43.3 days.[3] However, variations in the period have been observed on a time scale of 30–60 days.[15] The star has 1.15[10] times the mass of the Sun and has expanded to 60 times the Sun's radius.[2] It is radiating 757[2] times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 3,464 K.[12]
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