GRO J1655−40 is a

binary star A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved as separate stars us ...

consisting of an evolved F-type primary star and a massive, unseen companion, which orbit each other once every 2.6 days in the constellation of

Scorpius Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation whose recognition pred ...

. Gas from the surface of the visible star is accreted onto the dark companion, which appears to be a

stellar black hole A stellar black hole (or stellar-mass black hole) is a black hole formed by the gravitational collapse of a star. They have masses ranging from about 5 to several tens of solar masses. They are the remnants of supernova explosions, which may be ...

with several times the mass of the

Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

. The optical companion of this

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 common main sequence star), to the other component, called the ''acc ...

is a

subgiant A subgiant is a star that is brighter than a normal main-sequence star of the same spectral class, but not as bright as giant stars. The term subgiant is applied both to a particular spectral luminosity class and to a stage in the evolution ...

F star. Along with

GRS 1915+105 GRS 1915+105 or V1487 Aquilae is an X-ray binary star system containing a main sequence star and a black hole. Transfer of material from the star to the black hole generates a relativistic jet, making this a microquasar system. The jet ex ...

, GRO J1655−40 is one of at least two galactic "

microquasar A microquasar, a smaller version of a quasar, is a compact region surrounding a stellar black hole with a mass several times that of its companion star, observable in sufficient details, in our own or nearby galaxy. The matter being pulled from ...

s" that may provide a link between the

supermassive black hole A supermassive black hole (SMBH or sometimes SBH) is the largest type of black hole, with its mass being on the order of hundreds of thousands, or millions to billions, of times the mass of the Sun (). Black holes are a class of astronomical ...

s generally believed to power extragalactic

quasar A quasar ( ) is an extremely Luminosity, luminous active galactic nucleus (AGN). It is sometimes known as a quasi-stellar object, abbreviated QSO. The emission from an AGN is powered by accretion onto a supermassive black hole with a mass rangi ...

s and more local accreting black hole systems. In particular, both display the radio jets characteristic of many

active galactic nuclei An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such e ...

The distance from the Solar System is probably about 11,000 light years, or approximately half-way from the Sun to the

Galactic Center The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a ...

, but a closer distance of ~2800 ly is not ruled out. GRO J1655−40 and its companion are moving through the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

at around 112 km/s (250,000 miles per hour), in a galactic orbit that depends on its exact distance, but is mostly interior to the "Solar circle", ''d''~8,500 pc, and within 150 pc (~500 ly) of the galactic plane. For comparison, the Sun and other nearby stars have typical speeds on the order of 20 km/s relative to the average velocity of stars moving with the galactic disk's rotation in the solar neighborhood, which supports the idea that the black hole formed from the collapse of the core of a massive star. As the core collapsed, its outer layers exploded as a

supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

. Such explosions often seem to leave the remnant system moving through the galaxy with unusually high speed. The outburst source was found to exhibit quasi-periodic oscillations (QPOs) whose frequency increases monotonically during the rising phase of the outburst and with monotonically decreasing frequency in the declining phase of the outburst. This can be easily modeled assuming propagation of an oscillating shock wave: steadily going closer to the black hole due to rise in the Keplerian component rate in the rising phase and going away from the black hole as viscosity is withdrawn in the declining phase. The shock appears to be propagating at a speed of a few meters per second.

References

External links

* *SIMBAD
V* V1033 Sco -- High Mass X-ray Binary
"GRO J1665-40" * {{Stars of Scorpius X-ray binaries Stellar black holes Scorpius Microquasars Scorpii, V1033 F-type subgiants

See also

References

External links