Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Ursa Major |
Right ascension | 11h 19m 07.89965s[1] |
Declination | +38° 11′ 08.0285″[1] |
Apparent magnitude (V) | 4.80[2] (4.78 / 5.3)[3] |
Characteristics | |
Spectral type | A2V[2] (A1V + A2V + A1V)[4] |
U−B color index | +0.04[5] |
B−V color index | +0.09[5] |
Astrometry | |
Radial velocity (Rv) | -3.0 ± 2[6] km/s |
Proper motion (μ) | RA: -58.80[1] mas/yr Dec.: -65.33[1] mas/yr |
Parallax (π) | 17.00 ± 0.34 mas[1] |
Distance | 192 ± 4 ly (59 ± 1 pc) |
Absolute magnitude (MV) | -0.09 ± 0.20[4] |
Orbit[4] | |
Primary | 55 UMa Aa |
Companion | 55 UMa Ab |
Period (P) | 2.5537985 d |
Eccentricity (e) | 0.323 |
Periastron epoch (T) | 2449602.368 |
Argument of periastron (ω) (secondary) | 116.8° |
Semi-amplitude (K1) (primary) | 79.1 km/s |
Semi-amplitude (K2) (secondary) | 89.1 km/s |
Orbit[4] | |
Primary | 55 UMa A |
Companion | 55 UMa B |
Period (P) | 1872.7 ± 7.4 d |
Semi-major axis (a) | 0.0913 ± 0.0009″ |
Eccentricity (e) | 0.126 ± 0.008 |
Inclination (i) | 64.8 ± 0.8° |
Longitude of the node (Ω) | 130.0 ± 0.8° |
Periastron epoch (T) | 2448805 ± 18 |
Argument of periastron (ω) (secondary) | 223.9 ± 3.7° |
Semi-amplitude (K1) (primary) | 8.4 ± 1.3 km/s |
Semi-amplitude (K2) (secondary) | 20.2 ± 6.9 km/s |
Details[4] | |
55 UMa Aa | |
Mass | 2.0 M☉ |
Surface gravity (log g) | 4.25 cgs |
Temperature | 9230 ± 230 K |
Rotational velocity (v sin i) | 30 ± 4 km/s |
55 UMa Ab | |
Mass | 1.8 M☉ |
Surface gravity (log g) | 4.25 cgs |
Temperature | 8810 ± 250 K |
Rotational velocity (v sin i) | 45 ± 5 km/s |
55 UMa B | |
Mass | 2.1 M☉ |
Surface gravity (log g) | 4.25 cgs |
Temperature | 9290 ± 190 K |
Rotational velocity (v sin i) | 55 ± 5 km/s |
Other designations | |
Database references | |
SIMBAD | data |
55 Ursae Majoris (55 UMa) is a triple star system in the constellation Ursa Major. Its apparent magnitude is 4.80. Two stars form a close spectroscopic binary with an orbital period of 2.55 days. The third star orbits the central pair every 1873 days.[4] All three stars are A-type main-sequence stars.[4]
References
[edit]- ^ a b c d e van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
- ^ a b "* 55 UMa". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 23 February 2013.
- ^ "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 1 August 2017. Retrieved 24 June 2017.
- ^ a b c d e f g Liu, Ning; Gies, Douglas R.; Xiong, Ying; Riddle, Reed L.; Bagnuolo, Jr., William G.; Barry, Donald J.; Ferrara, Elizabeth C.; Hartkopf, William I.; Hooda, Jagbir S.; Mason, Brian D.; McAlister, Harold A.; Roberts, Jr., Lewis C.; Sowers, Jon W. (1997). "Tomographic Separation of Composite Spectra. V. The Triple Star System 55 Ursae Majoris". The Astrophysical Journal. 485 (1): 350–358. Bibcode:1997ApJ...485..350L. doi:10.1086/304418.
- ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
- ^ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.