Circinus X-1
{{Short description|Binary star in the constellation Circinus}}
{{use dmy dates|date=June 2015}}
{{Starbox begin}}
{{Starbox image
|image=250px
|caption=X-ray image of Circinus X-1
|credit=Chandra X-ray Observatory
}}
{{Starbox observe
|epoch=J2000
|constell=Circinus
}}
{{Starbox character
|variable=HMXB{{cite simbad|title=V* BR Cir|accessdate=22 September 2017}}
}}
{{Starbox astrometry
|dist_ly={{val|31000|+2600|-3300}}
}}
{{Starbox orbit
|period_unitless=16.68 ± 0.15 d
|periastron={{nowrap|JD 2453473.8 ± 0.4}}
|eccentricity=0.45 ± 0.07
|periarg=2 ± 12
|k1=25 ± 2
}}
{{Starbox catalog
|names={{odlist|V=BR Cir|name=INTREF 645|2MASS=J15204084-5710001|name2=2U 1516-56}}
}}
{{Starbox reference
|Simbad=V*+BR+Cir
}}
{{Starbox end
}}
Circinus X-1 is an X-ray binary star system that includes a neutron star. Observation of Circinus X-1 in July 2007 revealed the presence of X-ray jets normally found in black hole systems; it is the first of the sort to be discovered that displays this similarity to black holes. Circinus X-1 may be among the youngest X-ray binaries observed.
Location, distance
On June 14, 1969, an Aerobee 150 rocket, launched from Natal, Rio Grande do Norte, Brazil, obtained X-ray data during a scan of the Norma-Lupus-Circinus region that detected a well-isolated source at ℓ = 321.4±0.9° b = -0.5±2° (galactic), RA {{RA|15|14}} Dec {{Dec|-57|49}} within the constellation Circinus and referred to as Circinus XR-1 (Cir XR-1).{{ cite journal |author=Margon B|author2=Lampton M|author3=Bowyer S|author4=Cruddace R |title=A Pulsing X-Ray Source in Circinus |journal=Astrophys. J. |date=Oct 1971 |volume=169 |issue=10 |pages=L23–5 |bibcode=1971ApJ...169L..23M |doi=10.1086/180806 |hdl=2060/19710026671 |hdl-access=free }}
The distance of Circinus X-1 was not well established, with a low estimate of 13,400 light years{{cite journal|display-authors=4|author=R. Iaria|author2=M. Spano|author3=T. DiSalvo|author4=N.R. Robba|author5=L. Burderi|author6=R. Fender|author7=M. Van Der Klis|author8=F. Frontera|title=On The Soft Excess In The X-Ray Spectrum Of Circinus X-1: Revisitation Of The Distance To Circinus X-1|journal=The Astrophysical Journal|date=January 2005|volume=619|issue=1|pages=503–516|doi=10.1086/426422|arxiv = astro-ph/0410259 |bibcode = 2005ApJ...619..503I |s2cid=18973228}} and high estimate of 26,000 light years.{{cite web|title=Circinus X-1: Neutron Stars Join The Black Hole Jet Set|url=http://chandra.harvard.edu/photo/2007/cirx1/|publisher=Harvard-Smithsonian Center for Astrophysics|accessdate=5 December 2013}}
On June 23, 2015, an article published on NASA's Chandra X-Ray Observatory's website, revealed that an international team of astronomers has succeeded in determining its distance from Earth with more precision - via a method of triangulation of X-ray light emitted by the star, echoing through stellar clouds and interstellar dust - as being about 30,700 light-years.{{Cite web|title = NASA's Chandra Captures X-Ray Echoes Pinpointing Distant Neutron Star| date=23 June 2015 |url = http://www.nasa.gov/press-release/nasa-s-chandra-captures-x-ray-echoes-pinpointing-distant-neutron-star|accessdate = 2015-06-24}}
Other spectral regions
The binary nature of Cir X-1 has been established.{{ cite journal |author=Jones C|author2=Tananbaum H|author3=Giacconi R |title=UHURU Observations of the Binary Nature of Circinus X-1 |journal=141st Meeting Amer Astron Soc |volume=5|pages=395|location=Tucson, Arizona |date=1973 |bibcode=1973BAAS....5..395J }} The binary's radio component and a possible visual counterpart were identified by Whelan et al.{{cite journal|display-authors= 4|author= Whelan, J. A. J.|author2= Mayo, S. K.|author3= Wickramasinghe, D. T.|author4= Murdin, P. G.|author5= Peterson, B. A.|author6= Hawarden, T. G.|author7= Longmore, A. J.|author8= Haynes, R. F.|author9= Goss, W. M.|author10= Simons, L. W.|author11= Caswell, J. L.|author12= Little, A. G.|author13= McAdam, W. B.|journal=Monthly Notices of the Royal Astronomical Society|date=1977|volume=181|issue= 2|pages=259–271|bibcode=1977MNRAS.181..259W|title=The optical and radio counterpart of Circinus X-1 /3U 1516-56/ | doi = 10.1093/mnras/181.2.259 |doi-access= free}} Its infrared counterpart was located and found to flare with a 16.6-day period by Glass.{{cite journal|last=Glass|first=I.S.|title=Variations of Circinus X-1 in the infrared|journal=Monthly Notices of the Royal Astronomical Society|date=1978|volume=183|issue=3|pages=335–340|bibcode = 1978MNRAS.183..335G | doi = 10.1093/mnras/183.3.335 |doi-access=free}} A (heavily reddened) precise optical counterpart (now known as BR Cir) was identified by Moneti.{{cite journal|last=Moneti|first=A.|journal=Astronomy and Astrophysics|title=Optical and infrared observations of Circinus X-1|date=1992|volume=260|pages=L7–L10|bibcode = 1992A&A...260L...7M }}
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References
External links
{{commons-inline}}
- {{Cite web |url=http://chandra.harvard.edu/photo/2007/cirx1/ |title=Circinus X-1: Neutron Stars Join the Black Hole Set |accessdate=8 January 2009 |work=Chandra X-Ray Observatory |publisher=Harvard University / National Aeronautics and Space Administration |date=2007}}
{{Stars of Circinus}}
{{DEFAULTSORT:Circinus X-1}}