Astronomy:GRS 1915+105

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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.[1] "GRS" stands for "GRANAT source", "1915" is the right ascension (19 hours and 15 minutes) and "105" reflects the approximate declination (10 degrees and 56 arcminutes). The near-infrared counterpart was confirmed by spectroscopic observations.[2] The binary system lies 11,000 parsecs away[3] in Aquila. GRS 1915+105 is the heaviest of the stellar black holes so far known in the Milky Way Galaxy,[4] with 10 to 18 times the mass of the Sun.[5] It is also a microquasar, and it appears that the black hole rotates at close to 1,150 times per second, with a spin parameter value between 0.82 and 1.00 (maximum possible value).[6]

Galactic superluminal source

A sequence of MERLIN observation of the X-ray binary GRS 1915+105 taken over a few days.

In 1994, GRS 1915+105 became the first known galactic source that ejects material with apparent faster-than-light or superluminal velocities.[7]

Observations with high resolution radio telescopes such as VLA, MERLIN, and VLBI show a bi-polar outflow of charged particles, which emit synchrotron radiation at radio frequencies. These studies have shown that the apparent superluminal motion is due to a relativistic effect known as relativistic aberration, where the intrinsic velocity of ejecta is actually about 90% the speed of light.[3]

Growth regulation

Repeat observations by the Chandra X-Ray Observatory over the period of a decade have revealed what may be a mechanism for self-regulation of the rate of growth of GRS 1915+105. The jet of materials being ejected is occasionally choked off by a hot wind blowing off the accretion disk. The wind deprives the jet of materials needed to sustain it. When the wind dies down, the jet returns.[8]


  1. Castro-Tirado, A. J; Brandt, S; Lund, N (1992). "Grs 1915+105". IAU Circ 5590: 2. Bibcode1992IAUC.5590....2C. 
  2. Castro-Tirado, A. J; Geballe, T. R; Lund, N (1996). "Infrared Spectroscopy of the Superluminal Galactic Source GRS 1915+105 During the September 1994 Outburst". Astrophysical Journal Letters 461 (2): L99. doi:10.1086/310009. Bibcode1996ApJ...461L..99C. 
  3. 3.0 3.1 Fender, R. P; Garrington, S. T; McKay, D. J; Muxlow, T. W. B; Pooley, G. G; Spencer, R. E; Stirling, A. M; Waltman, E. B (1999). "MERLIN observations of relativistic ejections from GRS 1915+105". Monthly Notices of the Royal Astronomical Society 304 (4): 865. doi:10.1046/j.1365-8711.1999.02364.x. Bibcode1999MNRAS.304..865F. 
  4. "A Very Massive Stellar Black Hole in the Milky Way Galaxy". Retrieved 2017-11-25. 
  5. Greiner, J (2001). Grs 1915+105. pp. arXiv:astro–ph/0111540. 
  6. Jeanna Bryne. "Pushing the Limit: Black Hole Spins at Phenomenal Rate". Retrieved 2017-11-25. 
  7. Mirabel, I. F; Rodríguez, L. F (1994). "A superluminal source in the Galaxy". Nature 371 (6492): 46. doi:10.1038/371046a0. Bibcode1994Natur.371...46M. 
  8. "An Erratic Black Hole Regulates Itself" (Press release). NASA. 2009-03-25. Retrieved 2009-04-16.

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External links

Coordinates: Sky map 19h 15m 11.6s, +10° 56′ 44″ 1915+105 was the original source. Read more.