7 Aquarii

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7 Aquarii
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
7 Aqr, NSV 13419, BD−10°5553, HD 199345, HIP 103401, HR 8015, SAO 144968, ADS 14449, WDS J20569-0942 [9]
Database references
SIMBAD data

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]

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

  1. 1 2 3 4 5 6 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 .
  2. 1 2 3 4 5 6 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 .
  3. 1 2 3 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.
  4. 1 2 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.
  5. 1 2 3 4 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.
  6. 1 2 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.
  7. 1 2 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.
  8. 1 2 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:
  9. ↑ "7 Aqr". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved October 22, 2018.
  10. ↑ 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 .
  11. ↑ 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 .
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