65 Ursae Majoris

65 Ursae Majoris

Location of 65 Ursae Majoris (circled)
Observation data Epoch J2000      Equinox J2000
Constellation	Ursa Major
65 UMa ABC
Right ascension	11^h 55^m 05.74925^s[1]
Declination	+46° 28′ 36.6408″[1]
Apparent magnitude (V)	+6.54[2] (A/B/C = 6.7 / 8.5 / 8.32)[3]
65 UMa D
Right ascension	11^h 55^m 11.33152^s[1]
Declination	+46° 28′ 11.2150″[1]
Apparent magnitude (V)	+6.965[4]
Characteristics
65 UMa ABC
Spectral type	A7 / A7 / A3 / ? / ?[5]
U−B color index	+0.08[2]
B−V color index	+0.11[2]
Variable type	Algol[5]
65 UMa D
Spectral type	A0p[6]
U−B color index	+0.01[2]
B−V color index	+0.02[2]
Astrometry
65 UMa ABC
Radial velocity (Rv)	−3.90±4.4[7] km/s
Proper motion (μ)	RA: 10.41[1] mas/yr Dec.: 2.38[1] mas/yr
Parallax (π)	4.72 ± 0.58 mas[1]
Distance	approx. 690 ly (approx. 210 pc)
Absolute magnitude (MV)	−0.05[8]
65 UMa D
Radial velocity (Rv)	−7.00±3.7[9] km/s
Proper motion (μ)	RA: 11.82[1] mas/yr Dec.: 0.39[1] mas/yr
Parallax (π)	3.37 ± 0.56 mas[1]
Distance	approx. 1,000 ly (approx. 300 pc)
Absolute magnitude (MV)	−0.1[10]
Orbit[5]
Primary	65 UMa Aa1
Companion	65 UMa Aa2
Period (P)	1.73043 d
Inclination (i)	86.5±0.2°
Semi-amplitude (K1) (primary)	133.3±4.2 km/s
Semi-amplitude (K2) (secondary)	135.7±4.2 km/s
Orbit[5]
Primary	65 UMa Aa
Companion	65 UMa Ab
Period (P)	641.5±16.7
Eccentricity (e)	0.169±0.048
Inclination (i)	47°
Semi-amplitude (K1) (primary)	13.7[3] km/s
Semi-amplitude (K2) (secondary)	19.9±2.7 km/s
Orbit[5]
Primary	65 UMa A
Companion	65 UMa B
Period (P)	118.209±0.690 yr
Semi-major axis (a)	208.2±9.7 mas
Eccentricity (e)	0.504±0.006
Inclination (i)	38.1±2.4°
Longitude of the node (Ω)	92.1±4.2°
Periastron epoch (T)	2447516.9±126.8
Argument of periastron (ω) (secondary)	202.7±1.3°
Details
65 UMa Aa1
Mass	1.74±0.06[5] M☉
Radius	1.86±0.08[5] R☉
Temperature	8,000[5] K
65 UMa Aa2
Mass	1.71±0.06[5] M☉
Radius	1.81±0.08[5] R☉
Temperature	7,948±20[5] K
65 UMa Ab
Mass	2.4±0.4[5] M☉
65 UMa B
Mass	2.4±2.0[5] M☉
65 UMa C
Mass	2.01[3] M☉
65 UMa D
Mass	2.31[11](3.02 + 1.64[3]) M☉
Radius	2.93[11] R☉
Luminosity	79[11] L☉
Surface gravity (log g)	3.85[11] cgs
Temperature	8,600[11] K
Age	525[11] Myr
Other designations
65 UMa, ADS 8347, CCDM J11551+4629
65 UMa ABC: DN UMa, BD+47°1913, HD 103483, HIP 58112, HR 4560, SAO 43945
65 UMa D: BD+47°1914, HD 103498, HIP 58117, HR 4561, SAO 43946
Database references
	65 UMa AB
	65 UMa C
	65 UMa D

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,^[2] 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.

65 Ursae Majoris is a sextuple star system. It contains six stars in a hierarchical orbit where each star orbits its inner stars. Such systems are uncommon, with only a few sextuple stars known.^[5] Higher-multiplicity star systems are uncommon because they are less stable than their simpler counterparts, and often decay into smaller systems.

Multiplicity

Aa1

Period = 1.73d a = 0.2 mas

Aa2

Period = 641d a = 11 mas

Ab

Period = 118y a = 0.18″

B

3.4″ separation

C

63″ separation

D

Hierarchy of orbits in the 65 Ursae Majoris system

The central pair of stars, 65 Ursae Majoris Aa1 and Aa2, are both A-type main-sequence stars. These are relatively bright, white-colored stars that typically have masses from 1.6 M_☉ to 2.4 M_☉.^[12] They have relatively low masses for A-type main sequence stars and have spectral types of A7V.^[5] Its orbital period is 1.73 days.^[5]

The innermost binary pair 65 Ursae Majoris Aa is orbited by another star, designated 65 Ursae Majoris Ab. It is a spectroscopic binary: while the pair cannot be resolved, periodic Doppler shifts in their spectra indicate that there must be orbital motion. 65 Ursae Majoris Ab orbits the inner pair with a period of 641 days (1.76 years) and an eccentricity of 0.169.^[5]

65 Ursae Majoris B orbits the three inner stars every 118 years. It is separated from the triple by 0.18″, and an astrometric orbit has been calculated. 65 Ursae Majoris C and D are common proper motion companions and are separated 4″ and 63″ respectively from the central system.^[5] 65 Ursae Majoris D also appears to be a chemically peculiar star with higher amounts of chromium, strontium, and europium than normal.^[13] Because of its unusual composition, determination of its stellar parameters is difficult; the effective temperature of this star may be 9,300 or 9,500 K, with the radius and the surface gravity determined for the star dependent on the effective temperature.^[6] Speckle interferometry results have resolved 65 Ursae Majoris D into two components separated by 138 mas but this has not been confirmed by other observers. The two stars resolved differ in brightness by about two magnitudes.^[14] An orbit for two stars has been estimated to have a period of about 79 years.^[3]

Variability

A light curve for DN Ursae Majoris, plotted from TESS data^[15]

65 Ursae Majoris A is a variable star with the variable star designation DN Ursae Majoris. The pair Aa1 and Aa2 form an eclipsing binary as they periodically pass in front of each other while orbiting. The primary and secondary eclipses are almost identical and the apparent magnitude of the system varies between 6.55 and 6.65 twice during each orbit of 1.73 days.^[16] The brightness variation is very small because the non-eclipsing component Ab is the brightest of the three stars and contributes 80% of the visible light.^[5]

Distance

Trigonometric parallax measurements made by the Hipparcos spacecraft put the 65 Ursae Majoris ABC system at a distance of about 690 light years (210 parsecs), and component D at about 1,000 light years (300 parsecs).^[1] The dynamical parallax determined from the calculated orbits of the stars gives a distance of 763 ± 95 light-years (234 ± 29 pc).^[5] Gaia has published measurements for the AB system and for component D, but they are both highly uncertain. Gaia Early Data Release 3 includes a somewhat more reliable measurement for the parallax of component C at 4.3897±0.0245 mas,^[17] implying a distance of about 740 light years.^[18]

See also

• Castor, another multiple star system with six stars
• Zeta Phoenicis, a multiple star system including an eclipsing binary

References

1. 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. Tolbert, C. R. (1964). "A UBV Study of 94 Wide Visual Binaries". Astrophysical Journal. 139: 1105. Bibcode:1964ApJ...139.1105T. doi:10.1086/147852.
3. Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". Astronomy & Astrophysics Supplement Series. 124: 75–84. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181.
4. Høg, E.; et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. Bibcode:2000A&A...355L..27H.
5. Zasche, P.; Uhlář, R.; Šlechta, M.; Wolf, M.; Harmanec, P.; Nemravová, J. A.; Korčáková, D. (2012). "Unique sextuple system: 65 Ursae Majoris". Astronomy & Astrophysics. 542: A78. arXiv:1207.0651. Bibcode:2012A&A...542A..78Z. doi:10.1051/0004-6361/201219134. S2CID 56328797.
6. Pandey, Chhavi P.; Shulyak, Denis V.; Ryabchikova, Tanya; Kochukhov, Oleg (2012). "Abundance and stratification analysis of the CP star HD 103498". Astronomical Society of India Conference Series. 6: 225. arXiv:1106.3727. Bibcode:2012ASInC...6..225P. doi:10.1111/j.1365-2966.2011.19281.x. S2CID 56288919.
7. Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
8. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
9. Kharchenko, N. V.; et al. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ~55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. arXiv:0705.0878. Bibcode:2007AN....328..889K. doi:10.1002/asna.200710776. S2CID 119323941.
10. Gomez, A. E.; Luri, X.; Grenier, S.; Figueras, F.; North, P.; Royer, F.; Torra, J.; Mennessier, M. O. (1998). "The HR-diagram from HIPPARCOS data. Absolute magnitudes and kinematics of BP - AP stars". Astronomy and Astrophysics. 336: 953. Bibcode:1998A&A...336..953G.
11. Glagolevskij, Yu. V. (2019). "On Properties of Main Sequence Magnetic Stars". Astrophysical Bulletin. 74 (1): 66. Bibcode:2019AstBu..74...66G. doi:10.1134/S1990341319010073. S2CID 149900274.
12. Adelman, Saul J. (2004). "The physical properties of normal A stars". Proceedings of the International Astronomical Union. 2004: 1–11. Bibcode:2004IAUS..224....1A. doi:10.1017/S1743921304004314.
13. Abt, Helmut A.; Morrell, Nidia I. (1995). "The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars". Astrophysical Journal Supplement. 95: 135. Bibcode:1995ApJS...99..135A. doi:10.1086/192182.
14. Balega, Yu. Yu; Dyachenko, V. V.; Maksimov, A. F.; Malogolovets, E. V.; Rastegaev, D. A.; Romanyuk, I. I. (2012). "Speckle interferometry of magnetic stars with the BTA. I. First results". Astrophysical Bulletin. 67 (1): 44. Bibcode:2012AstBu..67...44B. doi:10.1134/S199034131201004X. S2CID 122554107.
15. "MAST: Barbara A. Mikulski Archive for Space Telescopes". Space Telescope Science Institute. Retrieved 8 December 2021.
16. Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
17. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
18. Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021). "Estimating Distances from Parallaxes. V. Geometric and Photogeometric Distances to 1.47 Billion Stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv:2012.05220. Bibcode:2021AJ....161..147B. doi:10.3847/1538-3881/abd806. S2CID 228063812.