65 Ursae Majoris
65 Ursae Majoris, abbreviated as 65 UMa, is a star system in the constellation of Ursa Major. With an apparent magnitude of about 6.5,[2] it is at the limit of human eyesight and is just barely visible to the naked eye. Trigonometric parallax measurements made by the Hipparcos spacecraft put it at a distance of about 690 light years (210 parsecs);[1] this is in close agreement with the dynamical parallax value of 763 ± 95 light-years (234 ± 29 pc).[5]
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Ursa Major |
| 65 UMa ABC | |
| Right ascension | 11h 55m 05.74925s[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 | 11h 55m 11.33152s[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[1] mas |
| Distance | approx. 690 ly (approx. 210 pc) |
| 65 UMa D | |
| Radial velocity (Rv) | -7.00 ± 3.7[8] km/s |
| Proper motion (μ) | RA: 11.82[1] mas/yr Dec.: 0.39[1] mas/yr |
| 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 | 8000[5] K |
| 65 UMa Aa2 | |
| Mass | 1.71 ± 0.06[5] M☉ |
| Radius | 1.81 ± 0.08[5] R☉ |
| Temperature | 7948 ± 20[5] K |
| 65 UMa D | |
| Radius | 4.39–4.56[6] R☉ |
| Surface gravity (log g) | 3.5–3.6[6] cgs |
| Temperature | 9300–9500[6] K |
| Other designations | |
| 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 | |
| SIMBAD | 65 UMa |
| 65 UMa AB | |
| 65 UMa C | |
| 65 UMa D | |
65 Ursae Majoris is a sextuple star system. It contains six stars in a hierarchical orbit where each star orbits the central system. Such systems are fairly 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 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☉.[9] 65 Ursae Majoris Aa1 and Aa2 both have relatively low masses for an A-type main sequence star and have spectral types of A7V.[5] Both components periodically pass in front of each other while orbiting, so they form an eclipsing binary with the variable star designation DN Ursae Majoris. Therefore, the apparent magnitude of the system varies between 6.6 and 6.7 magnitudes.[10] Its orbital period of 1.73 days.[5]
The eclipsing 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 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 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″ away from the central system, respectively.[5] 65 Ursae Majoris D also appears to be a chemically peculiar star with higher amounts of chromium, strontium, and europium than normal.[11] Because of its unusual composition, determination of its stellar parameters is difficult; the effective temperature of this star may be 9300 or 9500 K, with the radius and the surface gravity of the star depending on the effective temperature.[6]
See also
- Castor, another multiple star system with six stars
- Zeta Phoenicis, a multiple star system including an eclipsing binary
References
- 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.
- Tolbert, C. R. (1964). "A UBV Study of 94 Wide Visual Binaries". Astrophysical Journal. 139: 1105. Bibcode:1964ApJ...139.1105T. doi:10.1086/147852.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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....1.2025S.
- 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.