Epsilon Aquarii

Epsilon Aquarii
Location of ε Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 20h 47m 40.54957s[1]
Declination −09° 29′ 44.79693″[1]
Apparent magnitude (V) 3.77[2]
Characteristics
Evolutionary stage Main sequence[3] or subgiant[4]
Spectral type A1 V[2] + KV[4]
U−B color index +0.029[5]
B−V color index –0.001[5]
Variable type Constant[6]
Astrometry
Radial velocity (Rv)−19.82±0.58[1] km/s
Proper motion (μ) RA: +33.923 mas/yr[1]
Dec.: -34.926 mas/yr[1]
Parallax (π)13.3619 ± 0.3737 mas[1]
Distance244 ± 7 ly
(75 ± 2 pc)
Absolute magnitude (MV)−0.46[7]
Orbit[4]
PrimaryA
CompanionB
Period (P)1.2 years
Semi-major axis (a)25.9 mas
1.7 AU
Details
A
Mass2.98±0.03[3] M☉
Radius4.2[4] R☉
Luminosity161±9[8] L☉
Surface gravity (log g)3.66±0.14[9] cgs
Temperature9,622±327[9] K
Metallicity [Fe/H]−0.08±0.35[6] dex
Rotational velocity (v sin i)118.0±5.9[7] km/s
Age388[9] Myr
B
Mass0.61[4] M☉
Radius0.57[4] R☉
Temperature4,070[4] K
Other designations
Albali, ε Aqr, 2 Aquarii, BD–10°5506, FK5 781, HD 198001, HIP 102618, HR 7950, SAO 144810[10]
Database references
SIMBADdata

Epsilon Aquarii, Latinized from ε Aquarii, is a binary star in the equatorial zodiac constellation of Aquarius, located near the western constellation border with Capricornus. It has the proper name Albali /ælˈbeɪli/, now formally recognized by the IAU.[11][12] It is visible to the naked eye with an apparent visual magnitude of 3.77,[2] and has an absolute magnitude of −0.46.[7] Based upon parallax measurements taken by the Gaia spacecraft, it is located at a distance of approximately 244 light-years (75 pc) from Earth.[1] The star is drifting closer with a radial velocity of −20 km/s.[1]

The primary is an A-type main-sequence star with a stellar classification of A1 V.[2] It is estimated to be estimated 388[9] million years old with a high rate of spin, showing a projected rotational velocity of around 118 km/s.[7] The elemental abundances in the stellar atmosphere are close to solar, with pronounced underabundances of aluminium and strontium.[6] The star has three[3] times the mass of the Sun and about 4.2[4] times the Sun's radius. It is radiating 161[8] times the luminosity of the Sun from its photosphere at an effective temperature of 9,622 K.[9]

The secondary component is a K-type main-sequence star with 0.6 times the mass and 0.57 times the mass of the Sun. Located at a projected separation of 26 milliarcseconds from the primary, this translates to a physical separation of 1.7 astronomical units. Albali A and B complete an orbit around their center of mass each 1.2 years.[4]

  1. ^ a b c d e f g Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. ^ a b c d Cite error: The named reference pasp84_500_584 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference zorec2012 was invoked but never defined (see the help page).
  4. ^ a b c d e f g h i Cite error: The named reference waisberg was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference saooc8_59 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Kocer2003 was invoked but never defined (see the help page).
  7. ^ a b c d Cite error: The named reference vonEiff2012 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference baines was invoked but never defined (see the help page).
  9. ^ a b c d e Cite error: The named reference David2015 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Kunitzsch2006 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference IAU-LSN was invoked but never defined (see the help page).