X-shooter II nd Generation VLT Spectrograph for GRBs Paolo Goldoni, SAp/CEA-APC Conseil Scientifique - APC 21/11/2003

: The Long Wait BATSE 2704 burst Lack of Weak Bursts w.r.t. uniform distribution in Euclidean space Fluence Φ (cm -2 s -1 ) N (> Φ) Duration distribution bimodal 63% of bursts last < 30 s T 90 (s) Nombre de sursauts 63%

Optical Afterglow T B + 6,5 hT B + 12 hT B + 52 h GRB Afterglow : keV power law decline 1997 : BEPPO-SAX, the counterparts Host Galaxies Redshift ~ 35 measured redshift (0.16 ~1) Cosmological sources Most energetic (Γ ~100) Emitted energy γ ~ ergs

Afterglow lightcurves: Breaks, Bumps, Wiggles and the emergency of a SN Wijers et al Harrison et al Berger et al. 2003

GRB : the appearance of SN2003dh Evolution 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). The early spectra consist of a power-law continuum (F ~ ν -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 characteristic of a supernova. From Stanek et al. 2003

GRB030329: Association with SN Ib for long GRBs From Stanek et al. 2003

J. Paul7 “Standard” model 1 1Newly Formed BH surrounded by a torus 4Ext. shock 4 3Int. Shock 3 Lorentz Factor > Rel. Ejection 5 5Reverse shock

Open problems X-ray Flashes= GRB with lower peak energy Less energetic GRBs ? GRB at High Redshift ? Short Bursts ! No afterglow for T < 1 s Are GRBs an effective SFR tracer ? Structure of the jet ? Beaming ? (At least some) GRBs are the farthest stars we can observe State of the art (Zhang & Meszaros astro-ph/ )

1999 : Prompt Optical Emission 123 Discovery of Prompt Optical Emission of GRB Secondes après le déclenchement du sursaut Coups s -1 keV -1 Prompt Emission is not limited to γ-ray domain, GRB emitted in optical an isotropic equivalent energy of ~ ergs (m V ~ 9 in image 2 ) ROTSE-1

2002 : GRB Optical Observations of the error box of GRB detected and localized with HETE-2 Image NEAT 9 min after the burst m R = 15,3 Image DPOSS (20/8/1990)

Name V z 3C 273 ~ PKS ~ PG ~ Brightest Quasars vs. Brightest GRBs Name V z ~ ~ ~ Brightest GRBs can be used as new cosmological probes ! IGM study in several line of sights with unprecedented brightness

GRBs as cosmological probe Pros 1) Very bright 2) Unperturbed Medium, no proximity effect 3) Isotropic Distribution Cons 1) Very Fast Transient 2) Small Number SWIFT launch ~mid-2004 ~150 localized afterglow/year !

“Call for proposals for 2nd Generation VLT Instruments” ( ) 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  m) 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~ 10 4 wide-band visible-NIR high-throughput Spectrometer Goal of the instrument: Single object observations at the sky limit

Consortium NL,D,I,F,ESO Project Constraints and characteristics Very Fast realization ! (SWIFT launch mid-2004). Commisioning in 2006 and operation in 2007 are foreseen More than half budget from member states First second generation instrument to be operative but very tight budget Automatic operations driven by robotic telescopes at Chili: REM (APC) and Tarot-2

X-shooter Science Case: Faint Object Spectroscopy

GRB Afterglow, host galaxy, line-of-sight absorption 1) Type Ia Supernovae 2) X-ray Binaries Main Scientific Topics for APC The brightest cosmic lighthouses visible up to redshift  15 Stars and Structure formation in The early Universe Secondary Scientific Topics

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

X-shooter sensitivity Sensitivity to a 30 kms -1 line (moderately strong IGM absorption line) as a function of 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-α absorption 4 z > 5.8 quasars (Becker et al. 2001). X-shooter wil be able to observe all this band with 1 exposure

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

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

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

Why an IFU To perform (mini) area spectroscopy for higher spectrophotometric Accuracy over a wide spectral range of stellar and slightly extended targets To map the spectral characteristics of extended objects To reduce slit losses when operating with narrow spectrograph slits To reach the limiting spectral resolution of the instrument or with bad/variable seeing To reduce the effect of pointing errors when the targets are invisible in the acquisition system (or prompt response considerations preclude the use of the acquisition CCD) and the coordinates are known to +/-1 arcsec accuracy

IFU advantage: X-shooter FOV & OT positions Bloom et al 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”.

GRB and its host galaxy with HST May Observations, V~22.7, M (Galaxy)~-16.5

X-Shooter Planning Phase APhase BPhase CPhase D Nov 2003Avr 2004Apr 2005Apr 2006 Apr 2004Apr 2005Apr 2006Jul months12 months 16 months

APC Contribution IFU and IFU Data Reduction Software PI F. Hammer, DRS PI: A. Claret Science Team: P. Goldoni, H. Flores, P. Francois, Ph. Filliatre Scientific return: Guaranteed time under discussion ~15 % of total cost

Conclusions X-shooter has been approved by ESO STC, it will be the first IInd generation instrument operative at VLT APC/GEPI participation at ~15% guarantees an interesting return It will be the most sensitive VLT single object spectrograph The main scientific aim will be the GRBs with the possibility of detecting the farthest sources at the reionization epoch or beyond