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.[2]

V1054 Ophiuchi

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Ophiuchus
Right ascension	16^h 55^m 32.0^s
Declination	−08° 21′ 30″
Other designations
V1054 Oph, BD−08°4352, GJ 644, HD 152751, HIP 82817, SAO 141439, Wolf 630[1]
Database references
SIMBAD	The system
	ABab
	A
	Bab
	GJ 643
	C (vB 8)
	vB 8B (artifact)

Overview

V1054 Ophiuchi/Gliese 643 has the largest number of stars of all star systems located within 10 pc from Earth.[3] It is also the nearest quintuple star system[4] (the next nearest star systems with at least five stars are GJ 2069 (quintuple)[3] at 41.8 light-years, and Castor[4] (sextuple) at 51.6 light-years), and only quintuple star system within 10 pc.[3][5]

The system consists of three widely separated parts:

• close triple subsystem V1054 Ophiuchi A-Bab (including very close binary subsystem V1054 Ophiuchi Bab)
• Gliese 643
• V1054 Ophiuchi C (vB 8)

Hierarchy of the system is following:[4]

V1054 Ophiuchi/Gliese 643 V1054 Ophiuchi/Gliese 643 (without V1054 Ophiuchi C) V1054 Ophiuchi A‑Bab V1054 Ophiuchi Bab   V1054 Ophiuchi Ba     V1054 Ophiuchi Bb       V1054 Ophiuchi A       Gliese 643       V1054 Ophiuchi C (vB 8)

System's five components are:

Star	Mass, M☉	Spectral class	Absolute magnitude (MV)	Apparent magnitude (V)
V1054 Ophiuchi A	0.4155 ± 0.0057[3]	M3 V[3]	10.69 ± 0.02[4][note 1]	9.74[4]
V1054 Ophiuchi Ba	0.3466 ± 0.0047[3]	M4 Ve[note 2]	11.29 ± 0.05[4][note 1]	10.34[4]
V1054 Ophiuchi Bb	0.3143 ± 0.0040[3]	M4 Ve[note 2]	11.79 ± 0.05[4][note 1]	10.84[4]
Gliese 643	0.19[4]	M3.5 V[3]	12.69[4]	11.74[4]
V1054 Ophiuchi C	0.08[4]	M7.0 V[4]	17.75[4]	16.80[4]

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.[4]

Total apparent magnitude of V1054 Ophiuchi A-Bab triple subsystem is 9.02.[4][6]

Despite V1054 Ophiuchi/Gliese 643 consists of small low-mass stars, system's total mass, due large number of components, exceeds Solar mass,[4] (it is about 1.35 M_☉).

Distance

Currently, the most accurate distance estimate of V1054 Ophiuchi/Gliese 643 (apart from weighted mean distance, see below) is trigonometric parallax of V1054 Ophiuchi AB from YPC (Yale Parallax Catalog), 4th edition, published in 1995 (van Altena, Lee & Hoffleit):[7] 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:

Source	Paper	Parallax, mas	Distance, pc	Distance, ly	Ref.
Woolley	Woolley et al. 1970	156 ± 4	6.41 ± 0.17	20.9 ± 0.6	[8]
GJ, 3rd version	Gliese & Jahreiß 1991	153.9 ± 2.6	6.50 ± 0.11	21.19 ± 0.36	[9]
YPC, 4th edition	van Altena et al. 1995	154.8 ± 0.6	6.460 ± 0.025	21.07 ± 0.08	[7]
Hipparcos	Perryman 1997	174.23 ± 3.90	5.74 ± 0.13	18.7 ± 0.4	[6]
Soederhjelm	Soederhjelm 1999	155.63 ± 1.81	6.43 ± 0.08	20.96 ± 0.25	[10]
Hipparcos2	van Leeuwen 2007	161.41 ± 5.64	6.20 ± 0.22	20.21 ± 0.73	[11]

Gliese 643:

Source	Paper	Parallax, mas	Distance, pc	Distance, ly	Ref.
Woolley	Woolley et al. 1970	169 ± 5	5.92 ± 0.18	19.3 ± 0.6	[8]
GJ, 3rd version	Gliese & Jahreiß 1991	171.9 ± 7.3	5.82 ± 0.26	19.0 ± 0.8	[9]
YPC, 4th edition	van Altena et al. 1995	169.8 ± 6.6	5.89 ± 0.24	19.2 ± 0.8	[7]
Hipparcos	Perryman 1997	153.96 ± 4.04	6.50 ± 0.18	21.2 ± 0.6	[6]
Hipparcos2	van Leeuwen 2007	148.92 ± 4.00	6.72 ± 0.19	21.9 ± 0.6	[11]

V1054 Ophiuchi C (vB 8):

Source	Paper	Parallax, mas	Distance, pc	Distance, ly	Ref.
CTIOPI 1.5 m	TSN 14 (Costa et al. 2005)	155.43 ± 1.33	6.43 ± 0.06	20.98 ± 0.18	[12]

The most accurate estimate is marked in bold.

Weighted mean distance

Weighted mean parallax,[13] considering YPC (V1054 Ophiuchi A-Bab and Gliese 643), Hipparcos (Soederhjelm — V1054 Ophiuchi A-Bab and van Leeuwen — Gliese 643) and CTIOPI (V1054 Ophiuchi C) data, is 154.96 ± 0.52 mas,[14] 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,[3][4] or 1.72 years.[4] V1054 Ophiuchi Bab components are orbiting each other with period 2.9655 days.[3][4] Both outer and inner orbits are nearly circular and, probably, coplanar[3][4] (in keeping with a general tendency of close triple systems).[3]

V1054 Ophiuchi A-Bab pair is also visually resolved (for nearly 50 years it was the shortest-period resolved by visual means binary, since its binarity was discovered by G. P. Kuiper in 1934),[4] whereas V1054 Ophiuchi Ba-Bb pair is still unresolved).[3][4][note 3]

Outer orbit (V1054 Ophiuchi A - V1054 Ophiuchi Bab):

Period P (yr)	1.717267 ± 0.000039[4]
Period P (days)	627.0 ± 0.2,[3] 627.232 ± 0.014[4]
Semi-major axis a, arcsec	0.2273 ± 0.0004,[3] 0.2256 ± 0.0011[4]
Semi-major axis a, a.u.	1.46683,[3][note 4] 1.45586[4][note 4]
Eccentricity e	0.042 ± 0.001,[3] 0.0433 ± 0.0018[4]
Inclination i, °	160.3 ± 0.1,[3] 163.1 ± 1.6[4]
Longitude of the periastron ω, °	306.0 ± 1.5,[3] 115.6 ± 5.1[4]
Position angle of the ascending node Ω, °	-10.2 ± 0.2,[3] 163.2 ± 3.1[4]
Time of periastron passage T0	MJD 53943. ± 3.,[3] 1988.143 ± 0.011[4]

The most accurate estimates are marked in bold.

Inner orbit (V1054 Ophiuchi Ba - V1054 Ophiuchi Bb):

Period P (days)	2.965509 ± 0.000006,[3] 2.965522 ± 0.000014[4]
Semi-major axis a, arcsec	0.00687[note 5]
Semi-major axis a, a.u.	0.04432[note 6]
Eccentricity e	0.0209 ± 0.0008,[3] 0.026 ± 0.007[4]
Inclination i, °	164.18 ± 0.08,[3] 16.3 ± 0.3 or 163.7 ± 0.3[4]
Longitude of the periastron ω, °	150.0 ± 3.0,[3] 166 ± 16[4]
Position angle of the ascending node Ω, °
Time of periastron passage T0	MJD 50919.48 ± 0.03,[3] HJD 2447337.3 ± 0.14[4]

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,[3] 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,[3][4] 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,[4] that real separation of V1054 Ophiuchi C from V1054 Ophiuchi A-Bab is much larger, at least by factor two,[4] 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.[15]

Notes

1. From apparent magnitude and parallax.
2. Referred to entire V1054 Ophiuchi Bab subsystem.
3. At least it was not resolved by 2001.
4. Assuming weighted mean parallax 154.96 mas.
5. From masses, period and parallax.
6. From masses and period. According to Mazeh et al. 2001, of order of 0.05 a. u.

References

1. "HD 152751". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-25.
2. Bubar, Eric J.; King, Jeremy R. (August 2010). "Spectroscopic Abundances and Membership in the Wolf 630 Moving Group". The Astronomical Journal. 140 (2): 293–318. arXiv:1005.1205. Bibcode:2010AJ....140..293B. doi:10.1088/0004-6256/140/2/293.
3. Ségransan, D.; Delfosse, X.; Forveille, T.; Beuzit, J.-L.; Udry, S.; Perrier, C.; Mayor, M. (2000). "Accurate masses of very low mass stars. III. 16 new or improved masses". Astronomy and Astrophysics. 364: 665–673. arXiv:astro-ph/0010585. Bibcode:2000A&A...364..665S.
4. Mazeh, Tsevi; Latham, David W.; Goldberg, Elad; Torres, Guillermo; Stefanik, Robert P.; Henry, Todd J.; Zucker, Shay; Gnat, Orly; Ofek, Eran O. (2001). "Studies of multiple stellar systems - IV. The triple-lined spectroscopic system V1054 Ophiuchi". Monthly Notices of the Royal Astronomical Society. 325: 343–357. arXiv:astro-ph/0102451. Bibcode:2001MNRAS.325..343M. doi:10.1046/j.1365-8711.2001.04419.x.
5. RECONS CENSUS OF OBJECTS NEARER THAN 10 PARSECS
6. Vizier, The Hipparcos and Tycho Catalogues (ESA 1997)
7. VizieR, Yale Trigonometric Parallaxes, Fourth Edition (van Altena+ 1995)
8. Vizier, Stars within 25 pc of the Sun (Woolley+ 1970)
9. Vizier, Nearby Stars, Preliminary 3rd Version (Gliese+ 1991)
10. Vizier, Visual binary orbits and masses (Soederhjelm 1999)
11. Vizier, Hipparcos, the New Reduction (van Leeuwen 2007)
12. Costa, Edgardo; Méndez, René A.; Jao, W.-C.; Henry, Todd J.; Subasavage, John P.; Brown, Misty A.; Ianna, Philip A.; Bartlett, Jennifer (2005). "The Solar Neighborhood. XIV. Parallaxes from the Cerro Tololo Inter-American Observatory Parallax Investigation-First Results from the 1.5 m Telescope Program". The Astronomical Journal. 130: 337–349. Bibcode:2005AJ....130..337C. CiteSeerX 10.1.1.573.7563. doi:10.1086/430473.
13. DENSE Project. 25 pc White Dwarf Sample (see formulae below)
14. THE ONE HUNDRED NEAREST STAR SYSTEMS brought to you by RECONS (Research Consortium On Nearby Stars)
15. Reid, Neill I.; Hawley, Suzanne L., New Light on Dark Stars: Red Dwarfs, Low-Mass Stars, Brown Dwarfs, Astronomy and Planetary Sciences, Springer Science & Business Media, 2013, p. 344, ISBN 1447136632.