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66 Ophiuchi

66 Ophiuchi
Location of 66 Ophiuchi (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ophiuchus
Right ascension 18h 00m 15.79825s[1]
Declination 04° 22′ 07.0163″[1]
Apparent magnitude (V) 4.60[2]
Characteristics
Evolutionary stage main sequence
Spectral type B2Ve[3]
U−B color index −0.81[2]
B−V color index −0.02[2]
Variable type γ Cas[4]
Astrometry
Radial velocity (Rv)−12.80[5] km/s
Proper motion (μ) RA: +1.23[1] mas/yr
Dec.: −12.73[1] mas/yr
Parallax (π)5.01 ± 0.26 mas[1]
Distance650 ± 30 ly
(200 ± 10 pc)
Absolute magnitude (MV)−2.8 + −0.2[6]
Orbit[6]
Period (P)23421.1 ± 4.1 d
Semi-major axis (a)178.36 ± 1.37 mas
Eccentricity (e)0.142 ± 0.006
Inclination (i)75.90 ± 0.69°
Longitude of the node (Ω)338.87 ± 0.31°
Periastron epoch (T)JD 2452658.5 ± 50.2
Argument of periastron (ω)
(secondary)		115.24 ± 0.95°
Details
66 Oph A
Mass9.6[6] M☉
Luminosity1524.63[7] L☉
Surface gravity (log g)3.69[8] cgs
Temperature22,000[9] K
Metallicity [Fe/H]0.00[8] dex
Rotational velocity (v sin i)250[10] km/s
Age14.0±3.2[11] Myr
66 Oph B
Mass3.8[6] M☉
Other designations
66 Oph, V2048 Oph, BD+04°3570, GC 24500, HD 164284, HIP 88149, HR 6712, SAO 123005, WDS J18003+0422AB[12]
Database references
SIMBADdata

66 Ophiuchi is a binary[6] variable star[13] in the equatorial constellation of Ophiuchus. It has the variable star designation V2048 Ophiuchi, while 66 Ophiuchi is the Flamsteed designation. This object is visible to the naked eye as a faint, blue-white hued point of light with a baseline apparent visual magnitude of 4.60.[2] It is located approximately 650 light years away from the Sun based on parallax,[1] but is drifting closer with a radial velocity of −13 km/s.[5] The star has a peculiar velocity of 13.1±3.2 km/s[14] relative to its neighbors.

A visual band light curve for V2048 Ophiuchi, adapted from Floquet et al. (2002)[13]

The primary star, known as 66 Ophiuchi A, is a main sequence Be star with a stellar classification of B2Ve.[3] Be stars are rapidly rotating stars that eject gas from their equators due to their rotation, forming disks that produce emission lines. 66 Ophiuchi A's disk extends out to 115 R☉.[15] Like many other Be stars, it is a γ Cas variable; a shell star with a circumstellar disc of gas and is exhibiting irregular changes in brightness, ranging from 4.85 up to 4.55 magnitude.[4] The star is 14 million years old with 9.6[6] times the Sun's mass and is spinning rapidly with a projected rotational velocity of 250 km/s.[10] It is radiating 1,525[7] times the Sun's luminosity from its photosphere at an effective temperature of 22,000 K.[9] Because of its rotation, it has a polar equatorial radius 4.50 that of the Sun, but an equatorial radius 5.11 that of the Sun.[15]

A magnitude 6.5 visual companion at an angular separation of 0.1″ has been reported, and is known as 66 Ophiuchi B.[16] It is 2.61 magnitudes fainter than the primary. This corresponds to a mass of about 3.8 times that of the Sun, and a spectral class of about B8.[6]

  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 Hoffleit1991 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference gcvs was invoked but never defined (see the help page).
  5. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  6. ^ a b c d e f g Cite error: The named reference Hutter was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference XHIP was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Wu2011 was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference Hohle2010 was invoked but never defined (see the help page).
  10. ^ a b Cite error: The named reference Abt2002 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Tetzlaff2011 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference Floquet2002 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Bobylev2013 was invoked but never defined (see the help page).
  15. ^ a b Cite error: The named reference Marr was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference WDS was invoked but never defined (see the help page).
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