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   linkMPE   linkNews   pointer20090428
MPE News April 28, 2009

Gamma-Ray Burst 090423 detected at a record distance

GRB090423
In this composite picture the afterglow of GRB090423 is the red object shining only in some of the used color channels.
(klick on the image for full resolution)

GRB090423
Top: from left to right the seven spectral band images (g'r'i'z'JHK) of the afterglow of GRB 090423 observed with GROND.
Bottom: spectral energy distribution from g' to K and the estimated SED for a z = 8 object.
(klick on the image for full resolution)

Following a Gamma-Ray burst alarm of the NASA Swift Satellite on April 23, several groups world-wide started searching for the afterglow emission. The team led by Nial Tanvir (UK) first announced the discovery of the afterglow, based on measurements in the K band.
The MPE built  linkGROND instrument mounted at the MPI/ESO telesope at La Silla Observatory (Chile) observed this afterglow simultaneously in the spectral bands g'r'i'z'JHK about 15 hours after the burst. The simultaneous measurements in the seven spectral bands enabled scientists at MPE led by Jochen Greiner, to rapidly estimate the redshift of the burst to be around z = 8 which puts it into a new record distance.
The explosion of a star causing the Gamma-Ray burst occured when the universe was only 630 million years old (4.5 percent of the current age of the universe). Subsequent spectroscopic measurements at TNG (Canary Islands) and the VLT (ESO/Chile) confirmed this redshift estimate.
This burst was also detected by the Fermi Gamma-Ray Burst monitor  ( linkGBM), an instrument built in a collaboration between MPE and MSFC. Besides confirming a very low peak energy around 50 keV, the measurements also establish GRB 090423 as a long-duration burst.
Original GROND notification:
    external link GCN Circular 9215

external link NASA press release

external link ESO press release

external link MPG press release - interview with Jochen Greiner (in German language)

link special page on this burst by J. Greiner.


"Since some years, Gamma-ray bursts were believed (at least within the GRB community) to be ideal probes for the early Universe. The discovery of GRB 090423 is a wonderful confirmation of this believe. The quick succession of two record-breaking GRBs (the previous record holder was GRB 080913 at z = 6.7; external linkpaper, external linkNASA press release) implies that present-day routine follow-up strategies are now adequate to not miss high-redshift afterglows, and let us hope that even more distant GRBs will be identified to allow us to study the era of the formation of the first stars." (J. Greiner)

Contact:

J. Greiner linkDr. Jochen Greiner
  High-Energy Group
  Max-Planck-Institut für extraterrestrische Physik
  Germany
  Phone: +49 89 30000-3847
  Email: jcg@mpe.mpg.de

  ToP top of page Last update: 2009-05-01 by linkH. Steinle
Contact person: link Dr. Jochen Greiner
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