66 Ophiuchi

66 Ophiuchi
	Location of 66 Ophiuchi (circled)
Observation data; Epoch J2000 Equinox J2000
Constellation	Ophiuchus
Right ascension	18h 00m 15.79825s
Declination	04° 22′ 07.0163″
Apparent magnitude (V)	4.60
Characteristics
Evolutionary stage	main sequence
Spectral type	B2Ve
U−B color index	−0.81
B−V color index	−0.02
Variable type	γ Cas
Astrometry
Radial velocity (Rv)	−12.80 km/s
Proper motion (μ)	RA: +1.23 mas/yr ; Dec.: −12.73 mas/yr
Parallax (π)	5.01 ± 0.26 mas
Distance	650 ± 30 ly ; (200 ± 10 pc)
Absolute magnitude (MV)	−2.8 + −0.2
Orbit
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
Mass	9.6 M☉
Luminosity	1524.63 L☉
Surface gravity (log g)	3.69 cgs
Temperature	22,000 K
Metallicity [Fe/H]	0.00 dex
Rotational velocity (v sin i)	250 km/s
Age	14.0±3.2 Myr
66 Oph B
Mass	3.8 M☉
Other designations
	66 Oph, V2048 Oph, BD+04°3570, GC 24500, HD 164284, HIP 88149, HR 6712, SAO 123005, WDS J18003+0422AB
Database references
SIMBAD	data

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]

References

^ ^a ^b ^c ^d ^e ^f Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600. Vizier catalog entry
^ ^a ^b ^c ^d Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
^ ^a ^b Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H.
^ ^a ^b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
^ ^a ^b Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
^ ^a ^b ^c ^d ^e ^f ^g Hutter, D. J.; Tycner, C.; Zavala, R. T.; Benson, J. A.; Hummel, C. A.; Zirm, H. (2021). "Surveying the Bright Stars by Optical Interferometry. III. A Magnitude-limited Multiplicity Survey of Classical Be Stars". The Astrophysical Journal Supplement Series. 257 (2): 69. arXiv:2109.06839. Bibcode:2021ApJS..257...69H. doi:10.3847/1538-4365/ac23cb. S2CID 237503492.
^ ^a ^b Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644. Vizier catalog entry
^ ^a ^b Wu, Yue; Singh, H. P.; Prugniel, P.; Gupta, R.; Koleva, M. (2010). "Coudé-feed stellar spectral library – atmospheric parameters". Astronomy & Astrophysics. 525: A71. arXiv:1009.1491. Bibcode:2011A&A...525A..71W. doi:10.1051/0004-6361/201015014. S2CID 53480665.
^ ^a ^b Hohle, M.M.; Neuhäuser, R.; Schutz, B.F. (2010). "Masses and luminosities of O- and B-type stars and red supergiants". Astronomische Nachrichten. 331 (4): 349. arXiv:1003.2335. Bibcode:2010AN....331..349H. doi:10.1002/asna.200911355. S2CID 111387483. Vizier catalog entry
^ ^a ^b Abt, Helmut A.; Levato, Hugo; Grosso, Monica (2002). "Rotational Velocities of B Stars". The Astrophysical Journal. 573 (1): 359–365. Bibcode:2002ApJ...573..359A. doi:10.1086/340590.
^ Tetzlaff, N.; Neuhäuser, R.; Hohle, M. M. (2011). "A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun". Monthly Notices of the Royal Astronomical Society. 410 (1): 190–200. arXiv:1007.4883. Bibcode:2011MNRAS.410..190T. doi:10.1111/j.1365-2966.2010.17434.x. S2CID 118629873. Vizier catalog entry
^ "66 Oph". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-06-21.
^ ^a ^b Floquet, M.; et al. (October 2002). "Variability and pulsations in the Be star 66 Ophiuchi" (PDF). Astronomy and Astrophysics. 394: 137–149. Bibcode:2002A&A...394..137F. doi:10.1051/0004-6361:20021105.
^ Bobylev, V. V.; Bajkova, A. T. (August 2013). "Galactic kinematics from a sample of young massive stars". Astronomy Letters. 39 (8): 532–549. arXiv:1307.1677. Bibcode:2013AstL...39..532B. doi:10.1134/S106377371308001X. S2CID 118568203.
^ ^a ^b Marr, K. C.; Jones, C. E.; Carciofi, A. C.; Rubio, A. C.; Mota, B. C.; Ghoreyshi, M. R.; Hatfield, D. W.; Rímulo, L. R. (2021). "The be Star 66 Ophiuchi: 60 Years of Disk Evolution". The Astrophysical Journal. 912 (1): 76. arXiv:2103.06948. Bibcode:2021ApJ...912...76M. doi:10.3847/1538-4357/abed4c. ISSN 0004-637X. S2CID 232223272.
^ Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. Vizier catalog entry