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NGC 4993

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NGC 4993
Typical elliptical galaxy
Observation data
ConstellationHydra
Right ascension13h 09m 47.2s
Declination−23° 23′ 4″
Characteristics
Typegalaxy, E/S0

NGC 4993 (also catalogued as NGC 4994) is an elliptical galaxy in the constellation Hydra, discovered in 1789 by Wilhelm Herschel.[1] In August 2017, astronomers reported[2] that a short gamma-ray burst, of the sort conjectured to be emitted in the collision of two neutron stars,[3] was detected in this galaxy. A gravitational wave event had been rumored to have been detected in association with this burst. If verified, its waveform could have provided direct confirmation that binary neutron star collisions could produce short gamma-ray bursts.[4][5]. However, on 12 September 2017, LIGO and Virgo collaboration negated any such finding of a gravitational wave event.

Observations

GRB 170817A is a gamma-ray burst (GRB) detected by NASA's Fermi Gamma-ray Space Telescope and INTEGRAL/SPI-ACS on 17 August 2017.[2][5][6][7] A gravitational wave signal, with an optical counterpart, was rumored to have been observed by the LIGO/Virgo collaboration at the same time. The rumor first went public on 18 August 2017, tweeted by astronomer J. Craig Wheeler of the University of Texas at Austin. He later deleted the tweet and apologized. Others have followed up, and reported that the public logs of several major telescopes (HST, Chandra, ALMA, VLT) list priority interrupts in order to observe NGC 4993, with one record naming a gravitational wave followup as the reason.[5] The collaboration has declined to comment on the rumors, updating a previous announcement that there were seven triggers under analysis (as of 7 July 2017) to an unspecific "several" (as of 25 August 2017).[2][4][5][7][8] LIGO tweeted on 12 September 2017 that they published in Physical Review D (a synopsis by Katherine Wright of Physics.aps.org written on the same day) that the first run spanning 25 days (1 September to 25 September 2017) of LIGO and Virgo’s gravitational-wave search shows no evidence of spinning asymmetric neutron stars. LIGO added that further upgrades could make such detection possible in future.

See also

References

  1. ^ "NGC 4993". Deep Sky Observer's Companion. Retrieved 28 August 2017.
  2. ^ a b c Drake, Nadia (25 August 2017). "Strange Stars Caught Wrinkling Spacetime? Get the Facts". National Geographic. Retrieved 27 August 2017.
  3. ^ Nakar, E. (2007). "Short-hard gamma-ray bursts". Physics Reports. 442: 166–236. arXiv:astro-ph/0701748. Bibcode:2007PhR...442..166N. doi:10.1016/j.physrep.2007.02.005.
  4. ^ a b McKinnon, Mika (23 August 2017). "Exclusive: We may have detected a new kind of gravitational wave". New Scientist. Retrieved 28 August 2017.
  5. ^ a b c d Casttelvecchi, Davide (25 August 2017). "Rumours swell over new kind of gravitational-wave sighting". Nature News. doi:10.1038/nature.2017.22482. Retrieved 27 August 2017.
  6. ^ Kienlin, Andreas von (17 August 2017). "GCN Circular; Number: 21520; GRB 170817A: Fermi GBM detection; 2017/08/17 20:00:07 GMT". Max Planck Institute for Extraterrestrial Physics. Retrieved 28 August 2017.
  7. ^ a b Sokol, Joshua (25 August 2017). "What Happens When Two Neutron Stars Collide?". Wired. Retrieved 28 August 2017.
  8. ^ Staff (25 August 2017). "A very exciting LIGO-Virgo Observing run is drawing to a close August 25 [2017]". LIGO. Retrieved 29 August 2017.
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