Omega Ophiuchi

Omega Ophiuchi
Location of ω Ophiuchi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 16h 32m 08.19983s[1]
Declination −21° 27′ 59.0120″[1]
Apparent magnitude (V) 4.45[2] (4.44 – 4.51)[3]
Characteristics
Evolutionary stage main sequence[4]
Spectral type ApSrEuCr[5] or A2 Vp(SrCrEu st, K sn)[4]
U−B color index +0.13[6]
B−V color index +0.130±0.002[2]
Variable type α2 CVn[3]
Astrometry
Radial velocity (Rv)+2.5±0.7[7] km/s
Proper motion (μ) RA: +21.12[1] mas/yr
Dec.: +35.26[1] mas/yr
Parallax (π)19.34 ± 0.21 mas[1]
Distance169 ± 2 ly
(51.7 ± 0.6 pc)
Absolute magnitude (MV)0.88[2]
Details[8]
Mass2.25+0.13
−0.35 M☉
Radius2.97±0.19 R☉
Luminosity34.7±1.6 L☉
Surface gravity (log g)3.85+0.65
−0.69 cgs
Temperature8,150±250 K
Metallicity [Fe/H]−0.47[9] dex
Rotation2.3205±0.0002[10]
Rotational velocity (v sin i)32.2±1.4 km/s
Age860+150
−110 Myr
Other designations
ω Oph, 9 Ophiuchi, BD−21°4381, FK5 3307, GC 22221, HD 148898, HIP 80975, HR 6153, SAO 184450[11]
Database references
SIMBADdata

Omega Ophiuchi, which is Latinized from ω Ophiuchi, is a single,[12] variable star in the equatorial constellation of Ophiuchus, located just to the north of the ecliptic near the western constellation border with Scorpius. It is a white-hued star that is faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 4.45.[2] Parallax measurements indicate it lies at a distance of about 168.6 light years from the Sun.[1] It is drifting further away with a radial velocity of +2.5 km/s.[7]

This object is an Ap star with a stellar classification of ApSrEuCr,[5] displaying strong abundance anomalies of the elements strontium, europium, and chromium. Abt and Morrell (1995) found a class of A2 Vp(SrCrEu st, K sn),[4] showing further an A-type main-sequence star with a Ca II line (single-ionized calcium) having both sharp and broad components. It is an Alpha2 Canum Venaticorum variable, with its brightness ranging from magnitude 4.44 down to 4.51 over a period of 2.99 days.[3] A strong magnetic field has been measured on the surface.[10] A 2022 study detected no companion stars, but found an anomaly in its proper motion, suggesting it is potentially orbited by a compact star such as a white dwarf.[13]

Omega Ophiuchi is around 860 million years old with a projected rotational velocity of 32.2 km/s[8] and a rotation period of 2.3 days.[10] It has 2.3 times the mass of the Sun and 3.0 times the Sun's radius. The star is radiating 35 times the luminosity of the Sun from its photosphere at an effective temperature of 8,150 K.[8] It is a source of X-ray emission.[14]

  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 XHIP was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference Samus2017 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference abt1995 was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference houk1978 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Ducati2002 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  8. ^ a b c Cite error: The named reference Sikora2019a was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference Soubiran2016 was invoked but never defined (see the help page).
  10. ^ a b c Cite error: The named reference Sikora2019b was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).
  13. ^ Waisberg, Idel; Klein, Ygal; Katz, Boaz (2023). "Binarity and beyond in a stars – I. Survey description and first results of VLTI/GRAVITY observations of VAST targets with high Gaia–Hipparcos accelerations". Monthly Notices of the Royal Astronomical Society. 521 (4): 5232–5254. arXiv:2206.05251. Bibcode:2023MNRAS.521.5232W. doi:10.1093/mnras/stad872.
  14. ^ Cite error: The named reference Schröder2008 was invoked but never defined (see the help page).