Cygnus X-3

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Template:Short description

Cygnus X-3
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Cygnus[1]
Right ascension Template:RA[2]
Declination Template:DEC[2]
Characteristics
Spectral type WN 4–6[3]
Astrometry
Radial velocity (Rv)Template:Val[3] km/s
DistanceTemplate:Val[4] pc
Absolute magnitude (MV)Template:Val[3]
Orbit[3]
Period (P)4.8 hours
Semi-amplitude (K1)
(primary)		Template:Val km/s
Details
WR
Mass8–14[3] Template:Solar mass
Radius<2[3] Template:Solar radius
LuminosityTemplate:Val[3] Template:Solar luminosity
Temperaturemore than 80,000[3] K
compact object
MassTemplate:Val[5] Template:Solar mass
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
V1521 Cyg, 18P 57, WR 145a, X Cyg X-3, RX J2032.3+4057, INTEGRAL1 118, 2U 2030+40, 3U 2030+40, 4U 2030+40[6]
Database references
SIMBADdata

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Cygnus X-3 is a high-mass X-ray binary (HMXB), one of the stronger binary X-ray sources in the sky. It is often considered to be a microquasar, and it is believed to be a compact object in a binary system which is pulling in a stream of gas from an ordinary star companion. It is one of only two known HMXBs containing a Wolf–Rayet star. It is invisible visually, but can be observed at radio, infrared, X-ray, and gamma-ray wavelengths.

Observations

File:Cygnus X3.jpg
Cygnus X3 and its X-ray halo

Cygnus X-3 is a prominent X-ray source, with soft and hard X-rays both varying in intensity. Periods where the hard X-rays are at minimum intensity are known as soft states. It is less than half a degree from a gamma-ray pulsar, but is itself a weak gamma-ray source. It also shows periodic gamma-ray flares, apparently all occurring during the soft state.[7][8]

It is undetectable at visual wavelengths due to extreme extinction in the galactic plane. However, there is an infrared point source at its position.[3] Cygnus X-3 is also notable as the only microquasar firmly detected in the high energy gamma rays in the range >100 MeV.[9]

Because of the variations in emission at various wavelengths, Cygnus X-3 has been given the variable star designation V1521 Cygni.[10]

Flares

Cygnus X-3 is notable for its intense X-ray emission, but it is also remarkable for its gamma-ray and radio flares during which it becomes the brightest radio source in the Milky Way.[11] The gamma-ray flares apparently occur in the quiet radio period before a major radio flare.[7][8]

During the giant radio flares, a relativistic jet has been resolved within about Template:Val of being aimed directly towards us.[11]

Binary system

Cygnus X-3 shows consistent variations across all wavelengths with a Template:Val period. The nature of the infrared spectrum and the x-ray emission is interpreted as a binary system containing a Wolf–Rayet (WR) star and a compact object. The Template:Val variations have been interpreted as eclipses,[7] but this is thought to be unlikely because there are not well-defined periodic dips in the brightness.[3]

The orbit of the binary system is not known accurately, other than the period. Therefore, the masses of the components are not known accurately. Orbital analysis suggested that the mass of the compact object is less than Template:Solar mass, probably around Template:Solar mass. It could possibly be a neutron star but is more likely to be a black hole.[3] The combination of a WR star and a black hole would be the only known example.[12]

While the combination of WR star and compact object would be unique, the WR component will itself almost certainly become a black hole very quickly by astronomical timescales. A supernova or possible direct collapse to a black hole is expected within a million years or so. However, modelling of the Cygnus X-3 system suggests it is most likely that the binary will be disrupted by any supernova event.[13]

The cosmic ray events from Cygnus X-3 had previously led to exotic proposals such as a star made of quarks,[14] but are now explained as being produced in the relativistic jet. The explanation for the unusual relationship between the x-rays and the gamma-ray and radio flares is that the compact objects produces jets along its axis of rotation, within the dense wind from the WR star. These jets evacuate a cocoon within the wind when entering the hard state, and are then quenched by the wind when entering the soft state. Flares are produced during the transition to the hard state as the jets are interacting with the dense wind.[11]

Distance

Cygnus X-3 lies in the direction of the Cygnus OB2 association in the Cygnus X complex, although it is much further away.[4] Its distance can be estimated relative to Cygnus OB2 by studying the X-ray halo produced by dust between us and Cygnus X-3. The distance to Cygnus OB2 is not known precisely, but this method gives possible distances to Cygnus X-3 of Template:Val or Template:Val.[15]

There is a small X-ray source Template:Val from Cygnus X-3 that varies with the same period by a phase lag of about Template:Val. This is thought to be a Bok globule at approximately the same distance as Cygnus X-3. Using molecular line emission from this object, two possible distances are found to be Template:Val and Template:Val. A statistical mean is Template:Val.[4]

See also

References

Template:Reflist

External links

Template:Stars of Cygnus Template:Sky Template:Authority control

  1. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named constellation
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  4. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named mccollough
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named zdziarski
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  7. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named becklin
  8. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named tavani
  9. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named zanin
  10. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named gcvs
  11. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named koljonen2018
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named lutovinov
  13. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named belczynski
  14. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named quark
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named ling
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