Circinus X-1 is an

X-ray binary X-ray binaries are a class of binary stars that are luminous in X-rays. The X-rays are produced by matter falling from one component, called the ''donor'' (usually a relatively normal star), to the other component, called the ''accretor'', which ...

star system that includes a

neutron star A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. w ...

. Observation of Circinus X-1 in July 2007 revealed the presence of X-ray jets normally found in

black hole A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can defo ...

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 Rio Grande do Norte (, , ) is one of the states of Brazil. It is located in the northeastern region of the country, forming the northeasternmost tip of the South American continent. The name literally translates as "Great Northern River", re ...

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, 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 Dec within the constellation

Circinus Circinus is a small, faint constellation in the southern sky, first defined in 1756 by the French astronomer Nicolas-Louis de Lacaille. Its name is Latin for compass, referring to the drafting tool used for drawing circles (it should not be con ...

and referred to as Circinus XR-1 (Cir XR-1). The distance of Circinus X-1 was not well established, with a low estimate of 13,400 light years and high estimate of 26,000 light years. On June 23, 2015, an article published on NASA's

Chandra X-Ray Observatory The Chandra X-ray Observatory (CXO), previously known as the Advanced X-ray Astrophysics Facility (AXAF), is a Flagship-class space telescope launched aboard the during STS-93 by NASA on July 23, 1999. Chandra is sensitive to X-ray sources ...

'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.

X-ray source and age related to supernova remnant

A 16.6 day X-ray period was found by Kaluzienski et al. The X-ray source is assumed to be a

as part of a

low-mass X-ray binary X-ray binaries are a class of binary stars that are luminous in X-rays. The X-rays are produced by matter falling from one component, called the ''donor'' (usually a relatively normal star), to the other component, called the ''accretor'', which ...

(LMXB), type-I

X-ray burster X-ray bursters are one class of X-ray binary stars exhibiting X-ray bursts, periodic and rapid increases in luminosity (typically a factor of 10 or greater) that peak in the X-ray region of the electromagnetic spectrum. These astrophysical syst ...

. 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. An association of Circinus X-1 with a different nearby supernova remnant, G321.9-0.3, has been ruled out. 15-137-CircinusX1-XRayLightRings-NeutronStar-Chandra-20150624

15-137-CircinusX1-XRayLightRings-NeutronStar-Chandra-20150624

Other spectral regions

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

References

External links

{{DEFAULTSORT:Circinus X-1 X-ray binaries Circinus (constellation) Circini, BR Supergiants Neutron stars