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Chi Ophiuchi

Chi Ophiuchi

A blue-light light curve for Chi Ophiuchi, adapted from Cuypers et al. (1989)[1]
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Ophiuchus
Right ascension 16h 27m 01.43557s[2]
Declination −18° 27′ 22.4500″[2]
Apparent magnitude (V) 4.22[3] (4.18 to 5.0)[4]
Characteristics
Evolutionary stage main sequence
Spectral type B2Vne[5]
U−B color index −0.75[6]
B−V color index +0.28[6]
R−I color index +0.22[6]
Variable type GCAS[4] + LERI[7]
Astrometry
Radial velocity (Rv)−19.0±2.1[8] km/s
Proper motion (μ) RA: −5.378[2] mas/yr
Dec.: −22.308[2] mas/yr
Parallax (π)6.5402 ± 0.1961 mas[2]
Distance500 ± 10 ly
(153 ± 5 pc)
Absolute magnitude (MV)−2.27[9]
Details
Mass10.1±0.7[10] M☉
Radius4.44±0.09[11] R☉
Luminosity55,847[12] L☉
Surface gravity (log g)3.53±0.04[11] cgs
Temperature30,000±300[11] K
Rotational velocity (v sin i)150±3[11] km/s
Age22.5±2.6[10] Myr
Other designations
χ Oph, 7 Ophiuchi, BD−18°4282, FK5 3298, GC 22117, HD 148184, HIP 80569, HR 6118, SAO 159918, PPM 231703[13]
Database references
SIMBADdata

Chi Ophiuchi, Latinized from χ Ophiuchi, is a variable star in the equatorial constellation of Ophiuchus.[13] It has a blue-white hue and is faintly visible to the naked eye with an apparent visual magnitude that fluctuates around 4.22.[3] The distance to this object, as determined from parallax measurements, is approximately 500 light years,[2] but it is moving closer to the Sun with a radial velocity of −19 km/s.[8] This star is a proper motion member of the Upper Scorpius sub-group in the Scorpius–Centaurus OB association; the nearest such co-moving association of massive stars to the Sun.[14]

This is a massive Be star with a stellar classification of B2Vne,[5] where the 'n' indicates "nebulous" lines due to rapid rotation. It is spinning with a projected rotational velocity of 144 km/s. As the critical velocity for the star is 477 km/s, the inclination angle of its poles must be small; estimated as ~20°.[15] It is a Gamma Cassiopeiae variable with an amplitude of 0.15 magnitude.[16] The brightness has been measured varying from magnitude 4.18 down to 5.0.[4]

Chi Ophiuchi is 22.5 million years old with 10.1 times the mass of the Sun.[10] It has four times the Sun's radius and is radiating 56,000 times the luminosity of the Sun from its photosphere at an effective temperature of about 30,000 K. A weak magnetic field has been detected in the chromosphere of this star.[17] It is being orbited by a symmetrical disk of ejected gas extending out to 0.52 AU (112 R☉),[15] and excess radio and infrared emission has been detected from this structure.[18]

Abt and Levy (1978) cataloged Chi Ophiuchi as a single-lined spectroscopic binary with a period of 138.8 days and an eccentricity of 0.44, although the orbital elements are considered marginal.[19] Eggleton and Tokovinin (2008) list it as a single star.[20]

  1. ^ Cite error: The named reference Cuypers was invoked but never defined (see the help page).
  2. ^ a b c d e f Cite error: The named reference dr3 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference gcvs 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. ^ a b c Cite error: The named reference bsc2 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference vsx was invoked but never defined (see the help page).
  8. ^ a b Cite error: The named reference Gontcharov2006 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference melnik2020 was invoked but never defined (see the help page).
  10. ^ a b c Cite error: The named reference mnras410_1_190 was invoked but never defined (see the help page).
  11. ^ a b c d Cite error: The named reference arcos2018 was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference zorec2016 was invoked but never defined (see the help page).
  13. ^ a b Cite error: The named reference sb0 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference aaa216_1_44 was invoked but never defined (see the help page).
  15. ^ a b Cite error: The named reference Tycner2008 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Adelman2000 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Hubrig2007 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Taylor1987 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Abt1978 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Eggleton2008 was invoked but never defined (see the help page).

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