Sigma Aquarii

Sigma Aquarii
Location of σ Aquarii (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Aquarius
Right ascension 22h 30m 38.82286s[1]
Declination −10° 40′ 40.7031″[1]
Apparent magnitude (V) 4.81[2]
Characteristics
Spectral type A0 IVs[3]
U−B color index −0.14[2]
B−V color index −0.08[2]
Astrometry
Radial velocity (Rv)+11.7±0.6[4] km/s
Proper motion (μ) RA: −5.708[1] mas/yr
Dec.: −25.626[1] mas/yr
Parallax (π)18.6424 ± 0.6871 mas[1]
Distance175 ± 6 ly
(54 ± 2 pc)
Absolute magnitude (MV)0.29±0.23[5]
Details
Mass2.87[6] M☉
Radius2.87[5] R☉
Luminosity105[6] L☉
Surface gravity (log g)4.07[7] cgs
Temperature10,115[6] K
Metallicity [Fe/H]+0.44[7] dex
Rotational velocity (v sin i)21[8] km/s
Age30[5] Myr
Other designations
σ Aqr, 57 Aquarii, BD–11°5850, FK5 1591, HD 213320, HIP 111123, HR 8573, SAO 165134[9]
Database references
SIMBADdata

Sigma Aquarii, Latinized from σ Aquarii, is a double star in the equatorial constellation of Aquarius, positioned about 1.3° to the south of the ecliptic.[10] Due to its proximity to the ecliptic, this star is subject to occultation by the Moon.[11] It has a white hue and is visible to the naked eye with an apparent visual magnitude of 4.81.[2] Based upon parallax measurements, the distance to this star is approximately 175 light-years (54 parsecs).[1] It is drifting further away with a radial velocity of +11 km/s.[12]

The stellar classification of Sigma Aquarii is A0 IVs,[3] indicating that it is a subgiant star. The s qualifier means that its absorption lines are sharp (narrow) in comparison with standard stars, caused by a relatively slow rotation. It has been categorized as a hot Am star,[13] meaning that it is a chemically peculiar, although this is now considered doubtful.[14] The spectrum displays at least double the normal abundances of elements like magnesium, aluminum and silicon, while helium and scandium are under-abundant. Calcium, normally deficient in Am stars, has near-normal abundance.[13]

The Hipparcos catalogue identified Sigma Aquarii as a possible astrometric binary with an orbital period of 654 days.[15]

  1. ^ a b c d e f Cite error: The named reference GaiaDR2 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference clpl4_99 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference aj74_375 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Gerbaldi1999 was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference zorec was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference gebran was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference royer was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Sinnott1997 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Trunkovsky2010 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference gcsrv was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference adelman1984 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference renson was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference hipparcos was invoked but never defined (see the help page).