55 Ursae Majoris

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55 Ursae Majoris
Ursa Major constellation map.svg
Red circle.svg
Location of 55 Ursae Majoris (circled in red)
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]
Primary55 UMa Aa
Companion55 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]
Primary55 UMa A
Companion55 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
BD+38 2225, FK5 1293, HD 98353, HIP 55266, HR 4380, SAO 62491
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

  1. 1 2 3 4 5 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.
  2. 1 2 "* 55 UMa". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 23 February 2013.
  3. ↑ "Sixth Catalog of Orbits of Visual Binary Stars". United States Naval Observatory. Archived from the original on 1 August 2017. Retrieved 24 June 2017.
  4. 1 2 3 4 5 6 7 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 .
  5. 1 2 Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  6. ↑ Wilson, Ralph Elmer (1953). "General catalogue of stellar radial velocities". Washington. Bibcode:1953GCRV..C......0W.


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