BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:GRB 090423 at z=8.23 - probing the extremely distant universe with
  GRBs - Klaas Wiersema\, University of Leicester
DTSTART:20090916T150000Z
DTEND:20090916T151500Z
UID:TALK19877@talks.cam.ac.uk
CONTACT:Alexander Blustin
DESCRIPTION:On the 23d of April 2009 a gamma-ray burst was detected by Swi
 ft\, with unremarkable gamma-ray and X-ray properties. Our UKIRT rapid res
 ponse programme for GRB follow-up was triggered by an automatic (eStar) sy
 stem\, which revealed a relatively bright source in J\, H and K bands. Obs
 ervations with Gemini-North were obtained soon after\, revealing no source
  to very deep limits at wavelengths lower than ~1 micron\, indicating a ph
 otometric redshift well above 7. We activated our VLT spectroscopy program
  for high redshift bursts\, and acquired spectroscopy with ISAAC and SINFO
 NI. The spectra give a spectroscopic redshift of 8.23\, making GRB 090423 
 by some distance the most distant object known to date. I will show how th
 e gamma-ray and X-ray optical properties gave little indication of such an
  extreme redshift\, which highlights the need to follow-up every burst wit
 h Swift and groundbased facilities. I will discuss how we may be able to u
 se the current and future X-ray\, optical and radio facilities to use extr
 emely high redshift GRBs to probe the reionisation and chemical enrichment
  history of the Universe. 
LOCATION:Sackler Lecture Theatre\, IoA
END:VEVENT
END:VCALENDAR