55 Ursae Majoris

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55 Ursae Majoris
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]

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<span class="mw-page-title-main">65 Ursae Majoris</span> Star system in the constellation Ursa Major

65 Ursae Majoris, abbreviated as 65 UMa, is a star system in the constellation of Ursa Major. With a combined apparent magnitude of about 6.5, it is at the limit of human eyesight and is just barely visible to the naked eye in ideal conditions. It is about 760 light years away from Earth.

References

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  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. 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 .
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