X-shooterIInd Generation VLT Spectrograph for GRBsPaolo Goldoni, SAp/CEA-APCConseil Scientifique - APC 21/11/2003

1967-1997 : The Long Wait

1997 : BEPPO-SAX, the counterpartshttp://www.mpe.mpg.de/~jcg/grbgen.html

Afterglow lightcurves:Breaks, Bumps, Wiggles and the emergency of a SNWijers et al. 1997Harrison et al. 1999Berger et al. 2003

GRB 030329: the appearance of SN2003dhEvolution of the GRB 03029/SN 2003 spectrum,from April 1.13 UT (2.64 days after the burst)to April 8.13 UT (9.64 days after the burst). Theearly spectra consist of a power-law continuum (F ~ -0.9) with narrow emission lines originating from H II regions in the host galaxy at a redshift of z=0.168 taken after April 5 show the development of broad peaks in the spectra characteristicof a supernova. From Stanek et al. 2003

GRB030329: Association with SN Ibfor long GRBsFrom Stanek et al. 2003

Standard model

Open problemsX-ray Flashes= GRB with lower peak energyLess energetic GRBs ? GRB at High Redshift ?Short Bursts ! No afterglow for T < 1 sAre GRBs an effective SFR tracer ?Structure of the jet ? Beaming ?(At least some) GRBs are the farthest stars we can observeState of the art (Zhang & Meszaros astro-ph/0311321)

1999 : Prompt Optical Emission

2002 : GRB021004Optical Observations of the error box of GRB 021004detected and localized with HETE-2

Name V z3C 273 ~12.86 0.158 PKS 2155-304 ~13.09 0.17PG 1634+706 ~14.9 1.33Brightest Quasars vs. Brightest GRBsName V z990123 ~9 1.6 021004 ~15.3 2.3021211 ~18.2 1.01 Brightest GRBs can be used as new cosmological probes !IGM study in several line of sights with unprecedented brightness

GRBs as cosmological probePros1) Very bright2) Unperturbed Medium, no proximity effect3) Isotropic DistributionCons1) Very Fast Transient2) Small NumberSWIFT launch ~mid-2004~150 localized afterglow/year !

Call for proposals for 2nd Generation VLTInstruments (http://www.eso.org/instruments/vlt2ndgenins.html)The main goal is to get maximum detectivity on stellar or small emission-line objects,while covering the largest possible wavelength range (ideally 0.32 to 2.4 mm) in a single observation, presumably leading to a multiple arm ("x-shooter") system. A particularly important requirement is the ability to get spectrographic data on unpredictable/fast varying objects like supernova explosions or gamma ray burst optical counterparts, for the latter if possible in a matter of minutes.

R~ 104 wide-band visible-NIR high-throughput Spectrometer

Goal of the instrument: Single object observations at the sky limit

Consortium NL,D,I,F,ESOProject Constraints and characteristicsVery Fast realization ! (SWIFT launch mid-2004).Commisioning in 2006 and operation in 2007 are foreseenMore than half budget from member statesFirst second generation instrument to be operative but very tight budgetAutomatic operations driven by robotic telescopes atChili: REM (APC) and Tarot-2

X-shooter Science Case: Faint Object Spectroscopy

GRB Afterglow, host galaxy, line-of-sight absorption1) Type Ia Supernovae2) X-ray BinariesMain Scientific Topics for APCThe brightest cosmic lighthouses visible up toredshift 15 Stars and Structure formation inThe early UniverseSecondary Scientific Topics

Lamb & Reichart, 2000X- shooter Spectral range and maximum redshiftWavelength position of absorption lines and Lyman- forest as a function of redshift. To the right X-shooter spectral range with respect to UVES

X-shooter sensitivitySensitivity to a 30 kms-1 line (moderately strong IGM absorption line) as a functionof wavelength: X-shooter, FORS Giraffe and ISAAC

Afterglow lightcurve (R~13.6 after 5 minutes, R~18 after 1 day).Arrows mark the cooling and injection breaks. The vertical line mark the jet break.Afterglow Spectroscopy I : The Time evolution

Afterglow Spectroscopy II : The spectral break Afterglow spectra at 4 different epochs along with X-shooter spectral range

Cosmological Lyman- absorption4 z > 5.8 quasars (Becker et al. 2001). X-shooter wil be able toobserve all this band with 1 exposure

GRB spectra, where are the lines ? GRB021004 (z=2.23) spectrum taken with NOT R~19.0,importance of a WIDE spectral range

X-shooter spectrum of GRB 021004 at z=8.5Texp = 2 hr, reionization at z=7, 7 hours post burst.

APC Contribution: Integral Field Unit Fed. APC: GEPI-Meudon, SAp1 spectrum for every micro lens: PSF sampling and ~ 1 magnitude gain w.r.t. slit spectrographRealised by GEPI-Observatoire de Paris (Girafe):DRS responsibility of SAp

Why an IFUTo perform (mini) area spectroscopy for higher spectrophotometricAccuracy over a wide spectral range of stellar and slightly extendedtargetsTo map the spectral characteristics of extended objectsTo reduce slit losses when operating with narrow spectrograph slitsTo reach the limiting spectral resolution of the instrument or withbad/variable seeingTo reduce the effect of pointing errors when the targets are invisiblein the acquisition system (or prompt response considerations precludethe use of the acquisition CCD) and the coordinates are known to +/-1arcsec accuracy

IFU advantage: X-shooter FOV & OT positionsBloom et al. 2001 X-shooter FOV with IFU (1.6 x 3.2) is superposed to the angular distribution of 20 OTs in their galaxy. 1 pixel is 0.2 x 0.2.

http://www-int.stsci.edu/~fruchter/GRB/030329/GRB 030329 and its host galaxy with HST12-13 May Observations, V~22.7, M (Galaxy)~-16.5

X-Shooter Planning

Phase APhase BPhase CPhase DNov 2003Avr 2004Apr 2005Apr 2006Apr 2004Apr 2005Apr 2006Jul 20076 months12 months12 months16 months

APC ContributionIFU and IFU Data Reduction SoftwarePI F. Hammer, DRS PI: A. ClaretScience Team: P. Goldoni, H. Flores, P. Francois, Ph. FilliatreScientific return: Guaranteed time under discussion~15 % of total cost

ConclusionsX-shooter has been approved by ESO STC, it will be the first IInd generation instrument operative at VLTAPC/GEPI participation at ~15% guaranteesan interesting returnIt will be the most sensitive VLT single object spectrographThe main scientific aim will be the GRBs with the possibilityof detecting the farthest sources at the reionization epoch orbeyond