Circinus X-1

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.

Circinus X-1

X-ray image of Circinus X-1
Credit: Chandra X-ray Observatory
Observation data
Epoch J2000      Equinox J2000
Constellation Circinus
Right ascension 15h 20m 40.85s[1]
Declination −57° 10′ 00.1″[1]
Apparent magnitude (V) 21.40[2]
Characteristics
Spectral type B5–A0 I[3]
Variable type HMXB[4]
Astrometry
Distance31000+2600
−3300 ly
(9400+800
−1000[5] pc)
Orbit[3]
Period (P)16.68 ± 0.15 d
Eccentricity (e)0.45 ± 0.07
Periastron epoch (T)JD 2453473.8 ± 0.4
Argument of periastron (ω)
(secondary)		2 ± 12°
Semi-amplitude (K1)
(primary)		25 ± 2 km/s
Other designations
INTREF 645, 2U 1516-56, BR Cir, 2MASS J15204084-5710001[4]
Database references
SIMBADdata

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 15h 14m Dec −57° 49′ within the constellation Circinus and referred to as Circinus XR-1 (Cir XR-1).[6] The distance of Circinus X-1 was not well established, with a low estimate of 13,400 light years[7] and high estimate of 26,000 light years.[8]

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.[9]

A 16.6 day X-ray period was found by Kaluzienski et al.[10] The X-ray source is assumed to be a neutron star as part of a low-mass X-ray binary (LMXB), type-I X-ray burster.[11] The X-ray and radio nebulae surrounding Circinus X-1 have properties consistent with a young supernova remnant. This rare case of an X-ray binary apparently associated with a supernova remnant suggests the binary is very young on cosmic time scales, possibly less than 4600 years old.[12] An association of Circinus X-1 with a different nearby supernova remnant, G321.9-0.3, has been ruled out.[11]

X-ray light rings from a neutron star in Circinus X-1 (24 June 2015; Chandra X-ray Observatory).

Other spectral regions

The binary nature of Cir X-1 has been established.[13] The binary's radio component and a possible visual counterpart were identified by Whelan et al.[14] Its infrared counterpart was located and found to flare with a 16.6-day period by Glass.[15] A (heavily reddened) precise optical counterpart (now known as BR Cir) was identified by Moneti.[16]

References
  1. Cutri, R. M.; et al. (2003). "2MASS All-Sky Catalog of Point Sources". VizieR On-line Data Catalog. 2246. Bibcode:2003yCat.2246....0C.
  2. Liu, Q. Z; Van Paradijs, J; Van Den Heuvel, E. P. J (2007). "A catalogue of low-mass X-ray binaries in the Galaxy, LMC, and SMC (Fourth edition)". Astronomy & Astrophysics. 469 (2): 807. arXiv:0707.0544. Bibcode:2007A&A...469..807L. doi:10.1051/0004-6361:20077303. S2CID 14673570.
  3. Jonker, P. G; Nelemans, G; Bassa, C. G (2007). "Detection of the radial velocity curve of the B5-A0 supergiant companion star of Cir X-1?". Monthly Notices of the Royal Astronomical Society. 374 (3): 999–1005. arXiv:astro-ph/0605497. Bibcode:2007MNRAS.374..999J. doi:10.1111/j.1365-2966.2006.11210.x. S2CID 7474465.
  4. "V* BR Cir". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 22 September 2017.
  5. Heinz, S; Burton, M; Braiding, C; Brandt, W. N; Jonker, P. G; Sell, P; Fender, R. P; Nowak, M. A; Schulz, N. S (2015). "Lord of the Rings: A Kinematic Distance to Circinus X-1 from a Giant X-Ray Light Echo Lord of the Rings: A Kinematic Distance to Circinus X-1 from a Giant X-Ray Light Echo". The Astrophysical Journal. 806 (2): 265. arXiv:1506.06142. Bibcode:2015ApJ...806..265H. doi:10.1088/0004-637X/806/2/265. S2CID 17657655.
  6. Margon B; Lampton M; Bowyer S; Cruddace R (October 1971). "A Pulsing X-Ray Source in Circinus". Astrophys. J. 169 (10): L23–5. Bibcode:1971ApJ...169L..23M. doi:10.1086/180806. hdl:2060/19710026671.
  7. R. Iaria; M. Spano; T. DiSalvo; N.R. Robba; et al. (January 2005). "On The Soft Excess In The X-Ray Spectrum Of Circinus X-1: Revisitation Of The Distance To Circinus X-1". The Astrophysical Journal. 619 (1): 503–516. arXiv:astro-ph/0410259. Bibcode:2005ApJ...619..503I. doi:10.1086/426422. S2CID 18973228.
  8. "Circinus X-1: Neutron Stars Join The Black Hole Jet Set". Harvard-Smithsonian Center for Astrophysics. Retrieved 5 December 2013.
  9. "NASA's Chandra Captures X-Ray Echoes Pinpointing Distant Neutron Star". Retrieved 24 June 2015.
  10. Kaluzienski, L. J.; Holt, S. S.; Boldt, E. A.; Serlemitsos, P. J. (1976). "Evidence for a 16.6 day period from Circinus X-1". Astrophysical Journal. 208: L71–L75. Bibcode:1976ApJ...208L..71K. doi:10.1086/182235.
  11. Mignani RP; De Luca A; Caraveo PA; Mirabel IF (2002). "HST observations rule out the association between Cir X-1 and SNR G321.9-0.3". Astron. Astrophys. 386 (2): 487–91. arXiv:astro-ph/0202268. Bibcode:2002A&A...386..487M. doi:10.1051/0004-6361:20020224. S2CID 18606269.
  12. S. Heinz; P. Sell; R.P. Fender; P.G. Jonker; et al. (December 2013). "The Youngest Known X-ray Binary: Circinus X-1 and its Natal Supernova Remnant". The Astrophysical Journal. 779 (2): 171. arXiv:1312.0632. Bibcode:2013ApJ...779..171H. doi:10.1088/0004-637X/779/2/171. S2CID 6064052.
  13. Jones C; Tananbaum H; Giacconi R (1973). "UHURU Observations of the Binary Nature of Circinus X-1". 141st Meeting Amer Astron Soc. Tucson, Arizona. 5: 395. Bibcode:1973BAAS....5..395J.
  14. Whelan, J. A. J.; Mayo, S. K.; Wickramasinghe, D. T.; Murdin, P. G.; et al. (1977). "The optical and radio counterpart of Circinus X-1 /3U 1516-56/". Monthly Notices of the Royal Astronomical Society. 181 (2): 259–271. Bibcode:1977MNRAS.181..259W. doi:10.1093/mnras/181.2.259.
  15. Glass, I.S. (1978). "Variations of Circinus X-1 in the infrared". Monthly Notices of the Royal Astronomical Society. 183 (3): 335–340. Bibcode:1978MNRAS.183..335G. doi:10.1093/mnras/183.3.335.
  16. Moneti, A. (1992). "Optical and infrared observations of Circinus X-1". Astronomy and Astrophysics. 260: L7–L10. Bibcode:1992A&A...260L...7M.


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