1 Aquarii

1 Aquarii
Location of 1 Aqr (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 20h 39m 24.8927s[1]
Declination +00° 29′ 11.155″[1]
Apparent magnitude (V) 5.151[2]
Characteristics
Evolutionary stage horizontal branch[3]
Spectral type K1III[4]
U−B color index 0.936[2]
B−V color index 1.060[2]
Astrometry
Radial velocity (Rv)−40.93(3)[5] km/s
Proper motion (μ) RA: 96.805(120) mas/yr[1]
Dec.: −10.140(94) mas/yr[1]
Parallax (π)12.3852 ± 0.1134 mas[1]
Distance263 ± 2 ly
(80.7 ± 0.7 pc)
Absolute magnitude (MV)0.77[6]
Orbit[5]
Primary1 Aquarii A
Companion1 Aquarii B
Period (P)1966.7±2.9 days
Eccentricity (e)0.368±0.009
Periastron epoch (T)54740±7
Argument of periastron (ω)
(secondary)		150.7±1.6°
Semi-amplitude (K1)
(primary)		3.24±0.04 km/s
Details
Mass1.50±0.43[7] M☉
Radius11[8] R☉
Luminosity53.7[8] L☉
Surface gravity (log g)2.63±0.11[7] cgs
Temperature4715±15[9] K
Metallicity−0.12[6]
Rotational velocity (v sin i)1.8[6] km/s
Age1.26[7] Gyr
Other designations
1 Aqr, BD+0°4064, FK5 3651, HD 196758, HIP 101936, HR 7897, SAO 126062, CCDM J20394+0029, WDS J20394+0029[10]
Database references
SIMBADdata

1 Aquarii is a binary star[5] system in the zodiac constellation of Aquarius, about 263 light years away from the Sun.[1] 1 Aquarii is the Flamsteed designation. It is visible to the naked eye as a faint, orange-hued star with an apparent visual magnitude of 5.151,[2] located a degree north of the celestial equator.[5] The system is moving closer to the Earth with a heliocentric radial velocity of −41 km/s.[5]

Systematic observation for determining the orbit of this system began in 2002, some eighty years following the first radial velocity measurements. It is a single-lined spectroscopic binary with an orbital period of 5.385 yr and an eccentricity of 0.368.[5] The visible component is an aging giant star with a stellar classification of K1III.[4] At the age of 1.26[7] billion years old it is a red clump giant, which indicates it is on the horizontal branch and is generating energy through helium fusion at its core.[3] The star has 1.5[7] times the mass of the Sun and has expanded to 11[8] times the Sun's radius. It is radiating 53.7[8] times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,715 K.[9]

The mass of the companion appears small, suggesting a red dwarf no higher than class M5.[5] In addition to the spectroscopic companion there are two faint optical companions that have no physical relation to 1 Aqr.[11]

  1. ^ a b c d e Cite error: The named reference Gaia DR3 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Cousins1984 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Alves2000 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Roman1952 was invoked but never defined (see the help page).
  5. ^ a b c d e f g Cite error: The named reference Griffin2014 was invoked but never defined (see the help page).
  6. ^ a b c Pace, G.; Pasquini, L.; Ortolani, S. (2003). "The Wilson-Bappu effect: A tool to determine stellar distances". Astronomy and Astrophysics. 401 (3): 997–1008. arXiv:astro-ph/0301637. Bibcode:2003A&A...401..997P. doi:10.1051/0004-6361:20030163. S2CID 17029463.
  7. ^ a b c d e Cite error: The named reference Feuillet2016 was invoked but never defined (see the help page).
  8. ^ a b c d Cite error: The named reference Massarotti2008 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Luck2015 was invoked but never defined (see the help page).
  10. ^ "11 Per". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-03-28.
  11. ^ Cite error: The named reference WDSC2014 was invoked but never defined (see the help page).