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 An artist's impression of GRO J1655−40 | |
| Observation data EpochJ2000.0 EquinoxJ2000.0 (ICRS) | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 54m 00.14s[1] |
| Declination | −39° 50′ 44.9″[1] |
| Apparent magnitude (V) | 17.0[citation needed] |
| Characteristics | |
| Spectral type | F5IV[1] |
| Astrometry | |
| Distance | 5,500–11,000[citation needed] ly |
| Details | |
| Temperature | 6000–8000 (primary)[2][failed verification] K |
| Other designations | |
| V1033 Sco, GRO J1655−40 | |
| Database references | |
| SIMBAD | data |
GRO J1655−40 is abinary star consisting of an evolvedF-type primary star and a massive, unseen companion, which orbit each other once every 2.6 days in the constellation ofScorpius. Gas from the surface of the visible star isaccreted onto the dark companion, which appears to be astellar black hole with several times the mass of theSun. The optical companion of thislow-mass X-ray binary is asubgiant F star.
Along withGRS 1915+105, GRO J1655−40 is one of at least two galactic "microquasars" that may provide a link between thesupermassive black holes generally believed to power extragalacticquasars and more local accreting black hole systems. In particular, both display the radiojets characteristic of manyactive galactic nuclei.
The distance from the Solar System is probably about 11,000 light years, or approximately half-way from the Sun to theGalactic Center, but a closer distance of ~2800 ly is not ruled out. GRO J1655−40 and its companion are moving through theMilky Way 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 thesolar 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 asupernova. Such explosions often seem to leave the remnant system moving through the galaxy with unusually high speed.
The outburst source was found to exhibitquasi-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.[4]
