X Ophiuchi
{{short description|Binary star in the constellation Ophiuchus}}
{{Distinguish|Chi Ophiuchi{{!}}χ (Chi) Ophiuchi}}
{{Starbox begin}}
{{Starbox image
| image =
{{Location mark
| image=Ophiuchus IAU.svg
| float=center | width=250 | position=right
| mark=Red circle.svg | mark_width=10 | mark_link=ι Exa
| x%=15.8 | y%=20.4
}}
| caption=Location of X Ophiuchi (circled)
}}
{{Starbox observe
| epoch = J2000.0
| constell = Ophiuchus
| appmag_v = 6.40 ({{Val|5.9|to|9.2}})
}}
{{Starbox character
| type =
| class = {{nowrap|M0-8e + K2:III}}
M5e–M9e
| variable = Mira
}}
{{Starbox astrometry
| prop_mo_ra = 4.481
| prop_mo_dec = 14.781
| parallax = 5.1425
| p_error = 0.3495
| absmag_v =
}}
{{Starbox orbit
| primary =
| name =
| period = 877.14{{±|24.53}}
| axis = 0.822{{±|0.090}}
| eccentricity = 0.446{{±|0.026}}
| inclination = 103.7{{±|1.2}}
| node = 130.1{{±|0.3}}
| periastron = 2,020.98{{±|23.27}}
| periarg = 14.1{{±|2.6}}
| periarg_primary =
| k1 =
| k2 =
}}
{{Starbox detail
| source =
| component1 = Mira variable
| mass = 1.5[https://britastro.org/vss/vsoty2014.pdf Variable Star of the Year 2014 X Ophiuchi]
| gravity =
| metal_fe =
| rotation =
| rotational_velocity =
| age_gyr =
| component2 = K-type giant
| radius2 =
| luminosity2 =
| gravity2 =
| temperature2=
| metal_fe2 =
| rotation2 =
| rotational_velocity2 =
| age_gyr2 =
}}
{{Starbox catalog
| names = {{odlist | V=X Oph | BD=+08°3780 | GC=25485 | HD=172171 | HIP=91389 | HR=7002 | PPM=166252 | SAO=123744 | WDS=J18384+0850AB }}
}}
{{Starbox reference
| Simbad = X+Oph
}}
{{Starbox end}}
X Ophiuchi is a binary star system in the equatorial constellation of Ophiuchus, abbreviated X Oph. It is a Mira variable that ranges in brightness from an apparent visual magnitude of 5.9 down to 9.2 with a period of 328.85 days. The system is located at a distance of approximately 630 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −71 km/s.
This star was found to be variable by T. H. E. C. Espin in 1886. The binary nature of this system was reported by W. J. Hussey in 1900, listing an angular separation of {{val|0.22|u=arcsecond}} along a position angle of 195.2°. L. Campbell used light curves of the star from 1904 to 1921 to find a variability period of 337 days. In 1922, G. Van Biesbroeck showed that only the northward member of the pair is variable. P. W. Merrill in 1923 found a stellar classification of M6e for the variable component at maximum, while the secondary is K0. At minimum, the primary becomes fainter than the secondary in visual wavelengths. This make X Ophiuchi the Mira variable with the lowest maginitude variation known.
File:XOphLightCurve.png light curve for X Ophiuchi, plotted from AAVSO data]]
By 1959, the orbital arc of the pair had spanned an angle of 50°, providing an estimated orbital period of at least 500 years and a separation of {{val|64|ul=AU}}. Preliminary orbital models suggested a mass of {{val|0.8|ul=Solar mass}} for the variable component and {{val|1.2|u=Solar mass}} for the K-type giant. According to a 2014 publication, the total mass of the system is {{solar mass|4.5}}, with 2/3 of this mass (or {{solar mass|3}}) belonging to the K-type giant, and the remaining {{solar mass|1.5}} belonging to the Mira variable. The latter star showed an age of around five billion years. At that mass, the variable component must have undergone significant mass loss in order to have already evolved away from the main sequence. The K-type component may have received up to {{val|0.1|u=Solar mass}} from the donor star.
A 2007 model gives an orbital period of about 877 years with an eccentricity (ovalness) of 0.45. The variable component is an oxygen-rich M-type Mira variable. The duration, amplitude, and shape of the light curve is found to vary slightly from cycle to cycle. Some show a hump during the ascending curve. Its estimated mass loss rate is {{val|2.95|e=−9|ul=Solar mass}}·yr−1. In 1992, a strong radio flare event was observed from this system at a frequency of {{val|1667|ul=MHz|fmt=commas}}. This outburst came from an OH maser in the inner part of a shell surrounding the variable. Water in the shell is being photodissociated to create OH molecules.
References
{{reflist|refs=
| title=X Oph
| access-date=2024-10-05
| postscript=. | mode = cs2 }}
{{Cite Gaia EDR3|4479466244821909376}}
| title=Download Data |url=https://www.aavso.org/data-download | website=aavso.org | publisher=AAVSO
| access-date=5 October 2024}}
| title=Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters
| display-authors=1 | last1=Famaey | first1=B.
| last2=Jorissen | first2=A. | last3=Luri | first3=X.
| last4=Mayor | first4=M. | last5=Udry | first5=S.
| last6=Dejonghe | first6=H. | last7=Turon | first7=C.
| journal=Astronomy and Astrophysics
| volume=430 | pages=165 | date=January 2005
| doi=10.1051/0004-6361:20041272 | doi-access=free
| arxiv=astro-ph/0409579 | s2cid=17804304
| bibcode=2005A&A...430..165F }}
| title=Revised Catalog of Spectra of Mira Variables of Types ME and Se
| journal=The Astrophysical Journal Supplement Series
| display-authors=1 | last1=Keenan | first1=Philip C.
| last2=Garrison | first2=Robert F. | last3=Deutsch | first3=Armin J.
| volume=28 | pages=271 | year=1974
| doi=10.1086/190318|doi-access=free
| bibcode=1974ApJS...28..271K }}
| title=Catalogue of Stellar Photometry in Johnson's 11-color system.
| last=Ducati | first=J. R.
| journal=VizieR Online Data Catalog
| series=CDS/ADC Collection of Electronic Catalogues
| volume=2237 | year=2002
| bibcode=2002yCat.2237....0D }}
| display-authors=1 | last1=Samus | first1=N. N.
| last2=Kazarovets | first2=E. V. | last3=Durlevich | first3=O. V.
| last4=Kireeva | first4=N. N. | last5=Pastukhova | first5=E. N.
| title=General Catalogue of Variable Stars
| version=5.1 | journal=Astronomy Reports
| year=2017 | volume=61 | issue=1 | pages=80–88
| bibcode=2017ARep...61...80S | s2cid=125853869
| doi=10.1134/S1063772917010085 }}
| title=Observations of one hundred new double stars
| last=Hussey | first=William J.
| journal=Astronomical Journal
| volume=21 | issue=485 | pages=35–39 | date=November 1900
| doi=10.1086/103240 | bibcode=1900AJ.....21...35H
}}
Data for: 198. DM. +8°3780.
| title=The variable star X Ophuichi
| last=Gingrich | first=C. H.
| journal=Astrophysical Journal
| volume=56 | pages=132–138 | date=September 1922
| doi=10.1086/142694 | bibcode=1922ApJ....56..132G }}
| title=Spectroscopic observations of both components of the variable double star X Ophiuchi
| last=Merrill | first=P. W.
| journal=Astrophysical Journal
| volume=57 | pages=251–256 | date=May 1923
| doi=10.1086/142753 | bibcode=1923ApJ....57..251M }}
| title=The binary system X Ophiuchi
| last=Fernie | first=J. D.
| journal=Astrophysical Journal
| volume=130 | page=611 | date=September 1959
| doi=10.1086/146750 | bibcode=1959ApJ...130..611F }}
| title=X Ophiuchi
| last1=Le Squeren | first1=A. M. | last2=Etoka | first2=S.
| journal=IAU Circular
| volume=5724 | page=1 | date=March 1993
| editor-last=Marsden | editor-first=B. G.
| bibcode=1993IAUC.5724....1L }}
| title=A Flare in the Mira X Oph
| last1=Etoka | first1=S. | last2=Le Squeren | first2=A. M.
| journal=Astrophysics and Space Science
| volume=224 | issue=1 | pages=455–456 | date=February 1995
| doi=10.1007/BF00667902 | bibcode=1995Ap&SS.224..455E }}
| title=An OH maser flare in the Mira X Ophiuchi
| last1=Etoka | first1=S. | last2=Le Squeren | first2=A. M.
| journal=Astronomy and Astrophysics
| volume=315 | pages=134–140 | date=November 1996
| bibcode=1996A&A...315..134E }}
| title=Orbits of Ten Visual Binary Stars
| last=Novakovic | first=B.
| journal=Chinese Journal of Astronomy and Astrophysics
| volume=7 | issue=3 | pages=415–420 | date=June 2007
| doi=10.1088/1009-9271/7/3/11 | bibcode=2007ChJAA...7..415N }}
| title=Cycle-to-Cycle Changes of Mira-type Variable X Oph
| last1=Marsakova | first1=V. I. | last2=Andronov | first2=I. L.
| work=Proceedings of the 20th Stellar Conference of the Czech and Slovak Astronomical Institutes. 5th - 7th November 1997. Brno, Czech Republic
| editor-first=J. | editor-last=Dusek
| isbn=80-85882-08-6 | location=Brno
| year=1998 | page=130
| bibcode=1998vsr..conf..130M }}
| title=On the silicate crystallinities of oxygen-rich evolved stars and their mass-loss rates
| last1=Liu | first1=Jiaming | last2=Jiang | first2=B. W.
| last3=Li | first3=Aigen | last4=Gao | first4=Jian
| journal=Monthly Notices of the Royal Astronomical Society
| volume=466 | issue=2 | pages=1963–1986 | date=April 2017
| doi=10.1093/mnras/stw3165 | doi-access=free
| arxiv=1612.02115
| bibcode=2017MNRAS.466.1963L }}
}}
{{Ophiuchus}}
{{DEFAULTSORT:X Ophiuchi}}