Phi Ophiuchi

φ Ophiuchi
Location of φ Ophiuchi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 16h 31m 08.36732s[1]
Declination −16° 36′ 45.8306″[1]
Apparent magnitude (V) 4.27[2]
Characteristics
Spectral type G8+IIIa[3]
U−B color index +0.71[2]
B−V color index +0.92[2]
Astrometry
Radial velocity (Rv)–33.46[4] km/s
Proper motion (μ) RA: –45.35[1] mas/yr
Dec.: –37.34[1] mas/yr
Parallax (π)13.39 ± 0.24 mas[1]
Distance244 ± 4 ly
(75 ± 1 pc)
Absolute magnitude (MV)–0.08[5]
Details[6]
Mass3.16±0.04 M☉
Radius13.40±0.31 R☉
Luminosity111.8±4.3 L☉
Surface gravity (log g)2.72±0.02 cgs
Temperature5,131±32 K
Metallicity [Fe/H]0.16±0.10 dex
Rotational velocity (v sin i)3.6[7] km/s
Age330±10 Myr
Other designations
φ Oph, 8 Ophiuchi, BD−16 4298, GC 22200, HD 148786, HIP 80894, HR 6147, SAO 159963, CCDM J16311-1636A, WDS J16311-1637A[8]
Database references
SIMBADdata

Phi Ophiuchi, a name Latinized from φ Ophiuchi, is a single[9] star in the equatorial constellation of Ophiuchus.[8] It has a yellow hue and is faintly visible to the naked eye with an apparent visual magnitude of 4.27.[2] The star is located at a distance of approximately 244 light-years from the Sun based on parallax,[1] but it is drifting closer with a radial velocity of −33.5 km/s.[4]

The stellar classification of Phi Opiuchi is G8+IIIa,[3] an evolved giant star that has exhausted the supply of hydrogen at its core. In 2000, D. R. Alves identified it as a red clump giant on the horizontal branch that is generating energy by core helium fusion.[10] However, S. Reffert and associates in 2015 instead placed it on the red-giant branch.[6] A 2018 study by S. Stock and associates used Bayesian estimates to arrive at a 94% chance the star is on the horizontal branch.[11]

The star is around 360[12] million years old with an estimated 3.16 times the mass of the Sun and 13.4 times the Sun's radius. It is radiating 112 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 5,131 K.[6]

It has two visual companions, component B, at magnitude 12.9 and separation 41.3", and component C, at magnitude 10.8 and separation 119.8".[13]

  1. ^ a b c d e f Cite error: The named reference vanLeeuwen2007 was invoked but never defined (see the help page).
  2. ^ a b c d Cite error: The named reference Ducati2002 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Keenan_McNeil_1989 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Massarotti2008 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference XHIP was invoked but never defined (see the help page).
  6. ^ a b c Cite error: The named reference Reffert2015 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference deMedeiros2014 was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Eggleton_Tokovinin_2008 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Alves2000 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Stock_et_al_2018 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Luck2015 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference WDS was invoked but never defined (see the help page).