12 Aquarii

12 Aquarii is a triple star^[2] system in the zodiac constellation of Aquarius. 12 Aquarii is the Flamsteed designation. It is visible to the naked eye as a dim star with an apparent visual magnitude of 5.67.^[2] Parallax measurements by Hipparcos puts it at a distance of some 500 light-years, or 150 parsecs away.^[1] The system is moving further from the Earth with a heliocentric radial velocity of +1.1 km/s.^[5]

12 Aquarii

Observation data Epoch J2000      Equinox J2000
Constellation	Aquarius
Right ascension	21h 04m 04.72438s[1]
Declination	−05° 49′ 23.0347″[1]
Apparent magnitude (V)	5.67 (5.88 + 7.55)[2]
Characteristics
Spectral type	K0/1 III + A3 V[3] or G4 II + A3+ + (A4)[4]
Astrometry
Radial velocity (Rv)	+1.1±0.3[5] km/s
Proper motion (μ)	RA: +20.35[1] mas/yr Dec.: -6.67[1] mas/yr
Parallax (π)	6.50 ± 0.88 mas[1]
Distance	approx. 500 ly (approx. 150 pc)
Absolute magnitude (MV)	0.1 + 1.4 + 1.5[4]
Details
12 Aqr Aa/Ab
Mass	2.6/2.0[4] M☉
Temperature	5,012/8,511[4] K
12 Aqr B
Mass	1.9[4] M☉
Temperature	8,318[4] K
Other designations
12 Aqr, BD−06°5664, HIP 103981, ADS 14592, CCDM J21041-0549AB, WDS J21041-0549AB
12 Aqr A: HD 200497, HR 8059, SAO 145065
12 Aqr B: HD 200496, HR 8058, SAO 145064
Database references
SIMBAD	12 Aqr
	12 Aqr A
	12 Aqr B

The magnitude 5.88 primary,^[2] component A, is itself a binary star with a separation of 0.05″–0.07″ and an orbital period of around 18.5 yr. The brighter member of this duo is a G-type bright giant with a stellar classification of G4 II and 2.6 times the mass of the Sun. Its companion is an early A-type star with double the mass of the Sun.^[4] The tertiary component B is magnitude 7.55^[2] A-type main-sequence star^[3] at a separation of 2.44″ from the primary.^[2]

References

1. van Leeuwen, F. (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. Eggleton, P. P.; Tokovinin, A. A. (September 2008), "A catalogue of multiplicity among bright stellar systems", Monthly Notices of the Royal Astronomical Society, 389 (2): 869–879, arXiv:0806.2878, Bibcode:2008MNRAS.389..869E, doi:10.1111/j.1365-2966.2008.13596.x, S2CID 14878976.
3. Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey. 5. Bibcode:1999MSS...C05....0H.
4. Parsons, Sidney B. (May 2004), "New and Confirmed Triple Systems with Luminous Cool Primaries and Hot Companions", The Astronomical Journal, 127 (5): 2915–2930, Bibcode:2004AJ....127.2915P, doi:10.1086/383546.
5. 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.