16 Sagittarii

16 Sagittarii
Observation data
Epoch J2000      Equinox J2000
Constellation Sagittarius
Right ascension 18h 15m 12.96915s[1]
Declination −20° 23′ 16.7021″[1]
Apparent magnitude (V) 6.02[2]
Characteristics
Spectral type O9.5 III[3]
B−V color index 0.02[4]
Astrometry
Radial velocity (Rv)−11.0±1.3[5] km/s
Proper motion (μ) RA: +1.60[1] mas/yr
Dec.: −1.51[1] mas/yr
Distance4,600 ly
(1,400[4] pc)
Orbit[6]
Period (P)12.76123±0.00022 d
Eccentricity (e)0.181±0.060
Periastron epoch (T)54005.3 ± 0.7
Argument of periastron (ω)
(secondary)		156±19°
Semi-amplitude (K1)
(primary)		22.1±2.8 km/s
Details
16 Sgr Aa
Mass50[7] M☉
Luminosity7×109[8] L☉
Temperature11,683[8] K
Rotational velocity (v sin i)51[7] km/s
16 Sgr Ab
Mass3.72[7] M☉
Other designations
16 Sgr, BD−20° 5055, HD 167263, HIP 89440, HR 6823, SAO 186544, WDS J18152-2023A[9]
Database references
SIMBADdata

16 Sagittarii is a multiple[6] star system in the southern zodiac constellation of Sagittarius. It is near the lower limit of brightness for stars that can be seen with the naked eye, having an apparent visual magnitude of 6.02.[2] The estimated distance to this system is about 4,600 light years.[4] It is a member of the Sgr OB7 cluster.[4] Along with the O-type star 15 Sgr, it is ionizing an H II region along the western edge of the molecular cloud L291.[10]

Mason et al. (1998) found this to be a member of a speckle binary with an estimated orbital period of roughly 130 years and a magnitude difference of 0.4. Both components show indications of a variable radial velocity, suggesting that they are spectroscopic binaries – making it a candidate quadruple star system.[6] However, Tokovinin (2008) considers it a triple star system.[7]

Orbital elements for the main spectroscopic binary, components Aa and Ab,[4] were published by Mayer et al. (2014), giving an orbital period of 12.76 days and an eccentricity of 0.18.[6] This system displays a merged stellar classification of O9.5 III,[3] matching a blue-hued O-type giant star. It shows a longitudinal magnetic field strength of −74±44 G and a projected rotational velocity of 51 km/s.[11] Tokovinin (2008) gives an estimated mass of 50 times the mass of the Sun for the primary, and 3.72 for the secondary. The tertiary member, component B, has 2.54 times the Sun's mass.[7]

  1. ^ a b c d Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference ducati was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference gosss was invoked but never defined (see the help page).
  4. ^ a b c d e Cite error: The named reference Aldoretta2015 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference Mayer2014 was invoked but never defined (see the help page).
  7. ^ a b c d e Cite error: The named reference Tokovinin2008 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference McDonald2012 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 Marti1993 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Grunhut2017 was invoked but never defined (see the help page).