7 Aquarii, abbreviated 7 Aqr, is a binary star[3] system in the zodiac constellation of Aquarius. 7 Aquarii is the Flamsteed designation. It is visible to the naked eye with an apparent visual magnitude of 5.5;[2] the brighter component is baseline magnitude 5.62 while the faint secondary is magnitude 11.4.[3] As of 2002, the pair had an angular separation of 2.10″ along a position angle of 165°.[10] The distance to this system, based upon an annual parallax shift of 4.9 mas,[1] is around 660 light years. It is moving closer to the Earth with a heliocentric radial velocity of −32 km/s.[7]
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Aquarius |
| Right ascension | 20h 56m 54.02626s[1] |
| Declination | −09° 41′ 51.1610″[1] |
| Apparent magnitude (V) | 5.499[2] (5.62 + 11.4)[3] |
| Characteristics | |
| Spectral type | K4 III[4] |
| B−V color index | +1.474±0.006[5] |
| Variable type | Suspected[6] |
| Astrometry | |
| Radial velocity (Rv) | −32.4±1.6[7] km/s |
| Proper motion (μ) | RA: −5.577[1] mas/yr Dec.: −10.245[1] mas/yr |
| Parallax (π) | 4.9495 ± 0.1309 mas[1] |
| Distance | 660 ± 20 ly (202 ± 5 pc) |
| Absolute magnitude (MV) | −0.61[5] |
| Details | |
| Radius | 46[8] R☉ |
| Luminosity | 403.66[5] L☉ |
| Surface gravity (log g) | 1.650[2] cgs |
| Temperature | 3,990[2] K |
| Metallicity [Fe/H] | −0.17[2] dex |
| Other designations | |
| Database references | |
| SIMBAD | data |
The primary component is an aging giant star with a stellar classification of K4 III.[4] It is a suspected variable star of unknown type with a maximum magnitude of 5.48.[6] The interferometry-measured angular diameter of this star, after correcting for limb darkening, is 2.14±0.02 mas,[11] which, at its estimated distance, equates to a physical radius of about 46 times the radius of the Sun.[8] The star is radiating 404[5] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,990 K.[2]
References
edit- ^ a b c d e f Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051.
- ^ a b c d e f McWilliam, Andrew (December 1990), "High-resolution spectroscopic survey of 671 GK giants. I. Stellar atmosphere parameters and abundances", Astrophysical Journal Supplement Series, 74: 1075–1128, Bibcode:1990ApJS...74.1075M, doi:10.1086/191527.
- ^ a b c 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.
- ^ a b Houk, Nancy; Smith-Moore, M. (1978), Michigan catalogue of two-dimensional spectral types for the HD stars, vol. 4, Ann Arbor: Dept. of Astronomy, University of Michigan, Bibcode:1988mcts.book.....H.
- ^ a b c d 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.
- ^ a b Samus, N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017), "General Catalogue of Variable Stars", Astronomy Reports, GCVS 5.1, 61 (1): 80–88, Bibcode:2017ARep...61...80S, doi:10.1134/S1063772917010085, S2CID 125853869.
- ^ a b 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.
- ^ a b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R*) is given by:
- ^ "7 Aqr". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 22, 2018.
- ^ Mason, B. D.; et al. (2014), "The Washington Visual Double Star Catalog", The Astronomical Journal, 122 (6): 3466, Bibcode:2001AJ....122.3466M, doi:10.1086/323920.
- ^ Richichi, A.; et al. (February 2005), "CHARM2: An updated Catalog of High Angular Resolution Measurements", Astronomy and Astrophysics, 431 (2): 773–777, Bibcode:2005A&A...431..773R, doi:10.1051/0004-6361:20042039.
