Cygnus X-3

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Cygnus X-3
Observation data
Epoch J2000.0        Equinox J2000.0 (ICRS)
Constellation Cygnus
Right ascension 20h 32m 25.78s [1]
Declination +40° 57 27.9 [1]
Characteristics
Spectral type WN 4–6 [2]
Apparent magnitude  (H)13.192 [3]
Apparent magnitude  (J)15.309 [3]
Apparent magnitude  (K)11.921 [3]
Astrometry
Radial velocity (Rv)208+113
−127
[2]  km/s
Distance 7,400±1,100 [4]   pc
Absolute magnitude  (MV)−4.5 [2]
Orbit [2]
Period (P)4.8 hours
Semi-amplitude (K1)
(primary)
379+124
−149
km/s
Details
WR
Mass 8–14 [2]   M
Radius <2 [2]   R
Luminosity 209,000+93,000
−64,000
[2]   L
Temperature more than 80,000 [2]   K
compact object
Mass 2.4+2.1
−1.1
[5]   M
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. [3]
Database references
SIMBAD data

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.

Contents

Observations

Cygnus X3 and its X-ray halo 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. [6] [7]

It is undetectable at visual wavelengths due to extreme extinction in the galactic plane. However, there is an infrared point source at its position. [2] Cygnus X-3 is also notable as the only microquasar firmly detected in the high energy gamma rays in the range >100 MeV. [8]

Because of the variations in emission at various wavelengths, Cygnus X-3 has been given the variable star designation V1521 Cygni. [9]

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. [10] The gamma-ray flares apparently occur in the quiet radio period before a major radio flare. [6] [7]

During the giant radio flares, a relativistic jet has been resolved within about 14° of being aimed directly towards us. [10]

Binary system

Cygnus X-3 shows consistent variations across all wavelengths with a 4.8  h 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 4.8 h variations have been interpreted as eclipses, [6] but this is thought to be unlikely because there are not well-defined periodic dips in the brightness. [2]

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 5  M, probably around 2 M. It could possibly be a neutron star but is more likely to be a black hole. [2] The combination of a WR star and a black hole would be the only known example. [11]

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. [12]

The cosmic ray events from Cygnus X-3 had previously led to exotic proposals such as a star made of quarks, [13] 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. [10]

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 3.4 kpc or 9.3 kpc. [14]

There is a small X-ray source 16 from Cygnus X-3 that varies with the same period by a phase lag of about 2.7 h. 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 6.1±0.6 kpc and 7.8±0.6 kpc. A statistical mean is 7.4±1.1 kpc. [4]

See also

Related Research Articles

<span class="mw-page-title-main">Cygnus (constellation)</span> Constellation in the northern celestial hemisphere

Cygnus is a northern constellation on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. Cygnus is one of the most recognizable constellations of the northern summer and autumn, and it features a prominent asterism known as the Northern Cross. Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, and it remains one of the 88 modern constellations.

<span class="mw-page-title-main">Cygnus X-1</span> Galactic X-ray source in the constellation Cygnus that is very likely a black hole

Cygnus X-1 (abbreviated Cyg X-1) is a galactic X-ray source in the constellation Cygnus and was the first such source widely accepted to be a black hole. It was discovered in 1971 during a rocket flight and is one of the strongest X-ray sources detectable from Earth, producing a peak X-ray flux density of 2.3×10−23 W/(m2⋅Hz) (2.3×103 jansky). It remains among the most studied astronomical objects in its class. The compact object is now estimated to have a mass about 21.2 times the mass of the Sun and has been shown to be too small to be any known kind of normal star or other likely object besides a black hole. If so, the radius of its event horizon has 300 km "as upper bound to the linear dimension of the source region" of occasional X-ray bursts lasting only for about 1 ms.

<span class="mw-page-title-main">X-ray binary</span> Class of binary stars

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, to the other component, called the accretor, which is either a neutron star or black hole. The infalling matter releases gravitational potential energy, up to 30 percent of its rest mass, as X-rays. The lifetime and the mass-transfer rate in an X-ray binary depends on the evolutionary status of the donor star, the mass ratio between the stellar components, and their orbital separation.

<span class="mw-page-title-main">Galactic Center</span> Rotational center of the Milky Way galaxy

The Galactic Center is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact radio source which is almost exactly at the galactic rotational center. The Galactic Center is approximately 8 kiloparsecs (26,000 ly) away from Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius, where the Milky Way appears brightest, visually close to the Butterfly Cluster (M6) or the star Shaula, south to the Pipe Nebula.

<span class="mw-page-title-main">SS 433</span> Binary star system in the constellation Aquila

SS 433 is a microquasar or eclipsing X-ray binary system, consisting of a stellar-mass black hole accreting matter from an A-type companion star. SS 433 is the first discovered microquasar. It is at the centre of the supernova remnant W50.

<span class="mw-page-title-main">Gamma Velorum</span> Star system in the constellation Vela

Gamma Velorum is a quadruple star system in the constellation Vela. This name is the Bayer designation for the star, which is Latinised from γ Velorum and abbreviated γ Vel. At a combined magnitude of +1.7, it is one of the brightest stars in the night sky, and contains by far the closest and brightest Wolf–Rayet star. It has the traditional name Suhail al Muhlif and the modern name Regor, but neither is approved by the International Astronomical Union.

The Tolman–Oppenheimer–Volkoff limit is an upper bound to the mass of cold, non-rotating neutron stars, analogous to the Chandrasekhar limit for white dwarf stars. If the mass of a neutron star reaches the limit it will collapse to a denser form, most likely a black hole.

LS I +61 303 is a microquasar, a binary system containing a massive star and a compact object. The compact object is a pulsar and the system is around 7,000 light-years away.

<span class="mw-page-title-main">Westerlund 1</span> Super star cluster in the Milky Way Galaxy

Westerlund 1 is a compact young super star cluster about 3.8 kpc away from Earth. It is thought to be the most massive young star cluster in the Milky Way, and was discovered by Bengt Westerlund in 1961 but remained largely unstudied for many years due to high interstellar absorption in its direction. In the future, it will probably evolve into a globular cluster.

<span class="mw-page-title-main">GRS 1915+105</span> Binary system in the constellation Aquila

GRS 1915+105 or V1487 Aquilae is an X-ray binary star system which features a regular star and a black hole. It was discovered on August 15, 1992 by the WATCH all-sky monitor aboard Granat. "GRS" stands for "GRANAT source", "1915" is the right ascension and "105" reflects the approximate declination. The near-infrared counterpart was confirmed by spectroscopic observations. The binary system lies 11,000 parsecs away in Aquila. GRS 1915+105 is the heaviest of the stellar black holes so far known in the Milky Way Galaxy, with 10 to 18 times the mass of the Sun. It is also a microquasar, and it appears that the black hole rotates at least 950 times per second, close to the maximum of 1,150 times per second, with a spin parameter value between 0.82 and 1.00.

<span class="mw-page-title-main">WR 104</span> Triple star system

WR 104 is a triple star system located about 2,580 parsecs (8,400 ly) from Earth. The primary star is a Wolf–Rayet star, which has a B0.5 main sequence star in close orbit and another more distant fainter companion.

<span class="mw-page-title-main">Cygnus OB2-12</span> Blue hypergiant star

Cygnus OB2 #12 is an extremely luminous blue hypergiant with an absolute bolometric magnitude of −10.9, among the most luminous stars known in the galaxy. This makes the star nearly two million times more luminous than the Sun, although estimates were even higher when the star was first discovered. It is now known to be a binary, with the companion approximately a tenth as bright. A very approximate initial estimate of the orbit gives the total system mass as 120 M and the period as 30 years.

<span class="mw-page-title-main">Cygnus OB2-8A</span> Spectroscopic binary star near the center of Cygnus OB2

Cygnus OB2 #8A is a double-lined spectroscopic binary located near the centre of the Cygnus OB2 association located 5,500 light years away.

<span class="mw-page-title-main">Cygnus OB2</span> Cluster of massive and luminous stars

Cygnus OB2 is an OB association that is home to some of the most massive and most luminous stars known, including suspected Luminous blue variable Cyg OB2 #12. It also includes one of the largest known stars, NML Cygni. The region is embedded within a wider one of star formation known as Cygnus X, which is one of the most luminous objects in the sky at radio wavelengths. The region is approximately 1,570 parsecs from Earth in the constellation of Cygnus.

<span class="mw-page-title-main">V404 Cygni</span> Star and black hole binary star system in the constellation Cygnus

V404 Cygni is a microquasar and a binary system in the constellation of Cygnus. It contains a black hole with a mass of about 9 M and an early K giant star companion with a mass slightly smaller than the Sun. The star and the black hole orbit each other every 6.47129 days at fairly close range. Due to their proximity and the intense gravity of the black hole, the companion star loses mass to an accretion disk around the black hole and ultimately to the black hole itself.

<span class="mw-page-title-main">Colliding-wind binary</span> Binary star system in which two massive stars emit powerful stellar winds

A colliding-wind binary is a binary star system in which the two members are massive stars that emit powerful, radiatively-driven stellar winds. The location where these two winds collide produces a strong shock front that can cause radio, X-ray and possibly synchrotron radiation emission. Wind compression in the bow shock region between the two stellar winds allows dust formation. When this dust streams away from the orbiting pair, it can form a pinwheel nebula of spiraling dust. Such pinwheels have been observed in the Quintuplet Cluster

WR 147 is a multiple star system in the constellation of Cygnus. The system is extremely reddened by interstellar extinction – that is, dust in front of the star scatters much of the blue light coming from WR 147, leaving the star appearing reddish.

<span class="mw-page-title-main">WR 140</span> Star in the constellation of Cygnus

WR 140 is a visually moderately bright Wolf–Rayet star placed within the spectroscopic binary star, SBC9 1232, whose primary star is an evolved spectral class O4–5 star. It is located in the constellation of Cygnus, lying in the sky at the centre of the triangle formed by Deneb, γ Cygni and δ Cygni.

<span class="mw-page-title-main">HM 1</span> Open cluster in the constellation Scorpius

HM 1, also known as Havlen-Moffat 1, is an open cluster located in the constellation of Scorpius, close to the galactic plane. It was first observed by R. J. Havlen and A. F. J. Moffat in 1976. HM 1 is thought to be 9,500 to 12,700 light-years away from the Earth, beyond the Carina–Sagittarius Arm. It is heavily reddened by interstellar extinction, so although it comprises mostly blue-colored stars, it appears brighter for longer-wavelength passbands. It is projected against the H II region known as RCW 121, and appears to be the source of ionization for the nearby regions RCW 122 and RCW 123.

<span class="mw-page-title-main">CV Serpentis</span>

CV Serpentis is a binary star system in the equatorial constellation of Serpens. It is a detached eclipsing binary with an orbital period of 29.7 days. The system includes a Wolf–Rayet (WR) star with the identifier WR 113. The system is located at a distance of approximately 6,700 light years from the Sun based on parallax measurements. It is a member of the Serpens OB2 association of co-moving stars.

References

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