V1054 Ophiuchi


V1054 Ophiuchi, together with the star Gliese 643, is a nearby quintuple star system, in constellation Ophiuchus at 21.05 light-years. It consists of five stars, all of which are red dwarfs. The alternative designation of Wolf 630 forms the namesake of a moving group of stars that share a similar motion through space.

Overview

V1054 Ophiuchi/Gliese 643 has the largest number of stars of all star systems located within 10 pc from Earth. It is also the nearest quintuple star system at 41.8 light-years, and Castor, and only quintuple star system within 10 pc.
The system consists of three widely separated parts:
Hierarchy of the system is following:
System's five components are:
StarMass, Spectral
class		Absolute
magnitude 		Apparent
magnitude
V1054 Ophiuchi A0.4155 ± 0.0057M3 V10.69 ± 0.029.74
V1054 Ophiuchi Ba0.3466 ± 0.0047M4 Ve11.29 ± 0.0510.34
V1054 Ophiuchi Bb0.3143 ± 0.0040M4 Ve11.79 ± 0.0510.84
Gliese 6430.19M3.5 V12.6911.74
V1054 Ophiuchi C0.08M7.0 V17.7516.80

The brightest and most massive of this five stars is V1054 Ophiuchi A. Close binary subsystem V1054 Ophiuchi B is more massive than V1054 Ophiuchi A, however, its total visual magnitude is 0.1 mag fainter than V1054 Ophiuchi A's visual magnitude.
Total apparent magnitude of V1054 Ophiuchi A-Bab triple subsystem is 9.02.
Despite V1054 Ophiuchi/Gliese 643 consists of small low-mass stars, system's total mass, due large number of components, exceeds Solar mass,.

Distance

Currently, the most accurate distance estimate of V1054 Ophiuchi/Gliese 643 is trigonometric parallax of V1054 Ophiuchi AB from YPC, 4th edition, published in 1995 : 154.8 ± 0.6 mas, corresponding to a distance 6.460 ± 0.025 pc, or 21.07 ± 0.08 ly.
V1054 Ophiuchi/Gliese 643 distance estimates
V1054 Ophiuchi A-Bab:
SourcePaperParallax, masDistance, pcDistance, lyRef.
the Sun ">Woolley156 ± 46.41 ± 0.1720.9 ± 0.6
GJ, 3rd version153.9 ± 2.66.50 ± 0.1121.19 ± 0.36
YPC, 4th edition154.8 ± 0.66.460 ± 0.02521.07 ± 0.08
Hipparcos174.23 ± 3.905.74 ± 0.1318.7 ± 0.4
Soederhjelm155.63 ± 1.816.43 ± 0.0820.96 ± 0.25
Hipparcos2161.41 ± 5.646.20 ± 0.2220.21 ± 0.73

Gliese 643:
SourcePaperParallax, masDistance, pcDistance, lyRef.
Woolley169 ± 55.92 ± 0.1819.3 ± 0.6
GJ, 3rd version171.9 ± 7.35.82 ± 0.2619.0 ± 0.8
YPC, 4th edition169.8 ± 6.65.89 ± 0.2419.2 ± 0.8
Hipparcos153.96 ± 4.046.50 ± 0.1821.2 ± 0.6
Hipparcos2148.92 ± 4.006.72 ± 0.1921.9 ± 0.6

V1054 Ophiuchi C :
SourcePaperParallax, masDistance, pcDistance, lyRef.
CTIOPI 1.5 mTSN 14 155.43 ± 1.336.43 ± 0.0620.98 ± 0.18

The most accurate estimate is marked in bold.

Weighted mean distance

parallax, considering YPC, Hipparcos and CTIOPI data, is 154.96 ± 0.52 mas, corresponding to a distance 6.453 ± 0.022 pc, or 21.05 ± 0.07 ly.

V1054 Ophiuchi A-Bab (inner triple subsystem)

V1054 Ophiuchi A-Bab is a close spectroscopic triple subsystem, consisting of brighter component V1054 Ophiuchi A and more massive binary subsystem V1054 Ophiuchi Bab, orbiting each other with period 627 days, or 1.72 years. V1054 Ophiuchi Bab components are orbiting each other with period 2.9655 days. Both outer and inner orbits are nearly circular and, probably, coplanar.
V1054 Ophiuchi A-Bab pair is also visually resolved.
Outer orbit :
Period P 1.717267 ± 0.000039
Period P 627.0 ± 0.2,
627.232 ± 0.014
Semi-major axis a, arcsec0.2273 ± 0.0004,
0.2256 ± 0.0011
Semi-major axis a, a.u.1.46683,
1.45586
Eccentricity e0.042 ± 0.001,
0.0433 ± 0.0018
Inclination i, °160.3 ± 0.1,
163.1 ± 1.6
Longitude of the
periastron ω, °		306.0 ± 1.5,
115.6 ± 5.1
Position angle of the
ascending node Ω, °		-10.2 ± 0.2,
163.2 ± 3.1
Time of periastron
passage T0		MJD 53943. ± 3.,
1988.143 ± 0.011

The most accurate estimates are marked in bold.
Inner orbit :
Period P 2.965509 ± 0.000006,
2.965522 ± 0.000014
Semi-major axis a, arcsec0.00687
Semi-major axis a, a.u.0.04432
Eccentricity e0.0209 ± 0.0008,
0.026 ± 0.007
Inclination i, °164.18 ± 0.08,
16.3 ± 0.3 or 163.7 ± 0.3
Longitude of the
periastron ω, °		150.0 ± 3.0,
166 ± 16
Position angle of the
ascending node Ω, °
Time of periastron
passage T0		MJD 50919.48 ± 0.03,
HJD 2447337.3 ± 0.14

The most accurate estimates are marked in bold.

Distant components

Gliese 643

The projected separation of Gliese 643 from V1054 Ophiuchi A-Bab is 72 arcsec, corresponding at 21.05 light-years to 465 a.u.

V1054 Ophiuchi C (vB 8)

vB 8 is the smallest, faintest, and most separated component of the V1054 Ophiuchi system. The projected separation of the red dwarf from the primary triple system is about 220 arcsec, corresponding at 21.05 light-years to 1420 a.u. Since it is only three times larger than projected separation between Gliese 643 and V1054 Ophiuchi A-Bab, and such a small ratio should render triple system dynamically unstable, it was suggested, that real separation of V1054 Ophiuchi C from V1054 Ophiuchi A-Bab is much larger, at least by factor two, i. e. at least 2840 a.u.
In 1984, the apparent detection of an infrared source near vB 8 suggested it had a low mass companion. The low mass of this candidate led to speculation that it may be a brown dwarf; the first such to be detected. This discovery was later found to be spurious, but it produced much interest in this class of astronomical object.