Scienza dei GRBs dopo BeppoSAX & Swift Gianpiero Tagliaferri INAF – OABr Maggio, 2014

La scoperta dei Gamma Ray Bursts satelliti Vela 4,5,6: cercano raggi X e gamma per monitorare il rispetto del Geneva Limited Nuclear Test Ban Treaty del 1963 (nessun test nucleare nello spazio) Scoperta di intensi flash di raggi Gamma di origine cosmica: GAMMA RAY BURSTS (GRBs) (Klebesadel et al. 1973; Strong et al. 1974) -Centinaia di GRBs scoperti da vari satelliti daggli anni Nessuna idea sulla distanza delle sorgenti - I primi modelli si basavano su stelle a neutroni

CGRO : due tipi di GRBs La durata dei GRBs ha una distribuzione bimodale (e.g. Briggs et al. 2002) s -> burst brevi s -> burst lunghi I GRBs brevi hanno uno spettro più duro dei GRB lunghi (e.g. Fishman & Meegan, 1995;Tavani 1996)

BeppoSAX e l’era degli afterglow, GRB970228: il primo afterglow ottico ed X Il rapido ripuntamento con i NFIs di BeppoSAX (8hr) ha permesso la scoperta di una sorgente brillante e sconosciuta Un secondo puntamento 3 giorni dopo ha mostrato che la sorgente era più debole (Costa, et al., 1997) L’accuratezza della posizione X (~1 arcmin) ha portato all’identificazione con i telescopi da terra di una sorgente ottica che si indeboliva nel tempo (Van Paradijs, et al., 1997) Metzeger et al., 1997 I GRBs sono a distanze cosmologiche!

Gli spettri e le curve di luce degli afterglows: leggi di potenza  F x (t)  t ,  x ≈1.4  F x ( )    x ≈1.0

BAT XRT Spacecraft UVOT BAT UVOT XRT Spacecraft Strumenti Satellite GRB scoperti a bordo in automatico Ripuntamento automatico in sec Il satellite Swift (USA, I, UK) Burst Alert Telescope (BAT) Nuovi rivelatori CdZnTe Scopre >100 GRBs per anno (dipende dalla logN-logS) Il rivelatore di raggi gamma ad immagine più sensibile mai costruito X-Ray Telescope (XRT) Posizione dei GRB al secondo d’arco Spettroscopia CCD Fotometria nel range erg cm - 2 s -1 (UVOT) UV/Optical Telescope Immagini al sub-arcsec Spettroscopia con grism Sensibilità alla 24 th mag (1000 sec) Finding chart per gli altri osservatori

Short GRB Swift GRB Statistics Fast Rise Exponential Decay >860 GRB 85% (91%) con scoperta di afterglow X ~60% con scoperta di afterglow ottico >270 con redshift (41 prima di Swift) > 70 GRBs brevi localizzati (0 prima di Swift), piu’ di 20 con redshift)

10 years of Swift

 Prompt (<T p )  PL Decay О Flares О Emission “Hump” O ’ Brien et al. 2006, ApJ 647, 1213 Un insieme delle curve di luce X di GRB visti da Swift

GRB050904: un tipico esempio di GRB scoperto da Swift (a z=6.29 !!!)

Salvaterra et al Tanvir et al Cucchiara et al GRBs su 600 a z>5 z = 6.29 GRB z = 9.4 GRB B z = 8.2 GRB Tagliaferri et al. 2005, Kawai et al GRBs ad alto redshift

Universo lontano (quindi giovane) Metallicità Kistler et al Tasso di formazione stellare Thöne et al Savaglio 2006 z GRB Optical Brightness B K = 3 hrs K = 20 min K = 10 min J = 3 hrs I = 2 min K = 23 hrs R = 1.5 hrs GRBs: le sorgenti ad alto-z più brillanti

GRB most important facts GRB are cosmological (therefore large energetics, but how large? Depends on collimation..; history of Star formation; beacon to study the Universe) GRBs have large Γ (From GeV; msec variability; radio scintillation; theory) Long & Short (but there are exceptions + extended emission) SN connection (i.e. progenitors. But there are exceptions. Evidence can be gathered only from nearby, under-luminous GRBs, but see GRB130427A) GW? (we do not have evidences so far, but with the Advanced-LIGO & -VIRGO short burst could be good candidate for the detection of GW)

GRBs a mystery or an opportunity? After more than 40 years we know a lot about GRB, still they are a big puzzle!! What is the prompt? Which is the mechanism? Who is the progenitor? (very massive star? Binary? Fast rotator? Coalescence? …) What is left over? (BH? NS? nothing?) Do we always have a SN associated to a long-GRB? Why sometimes we have a precursor? What is it? GRBs physics

GRBs a mystery or an opportunity? After more than 40 years we know a lot about GRB, still they are a big puzzle!! Are they a good tracer of SFR and star evolution? Are they a good tracer of galaxy evolution and therefore of the history of the Universe? Are they unbiased “illuminators” in & of the Universe? Will they ever be good distance indicators? GW GRBs as indicators UFFO SVOM

GRBs a mystery or an opportunity? After more than 40 years we know a lot about GRB, still they are a big puzzle!! So what do we need ideally, for the prompt? Energy band: ≤1 keV – ≥50 MeV Field of view: 2 steradiant Sensitivity: ~1500 cm 2 up to keV; ~6000 cm 2 up to 1 MeV High time resolution (<1ms) Good energy resolution (few hundreds eV <10 keV, 10-15% above) X-ray polarisation

NIR spectrum for high z GRB 17

18 GRB afterglow at z=7 after 60s X-Rat Telescope on ORIGIN: 1000cm2, 2eV energy resolution High resolution X-ray spectroscopy of high z GRB

GRBs a mystery or an opportunity? After more than 40 years we know a lot about GRB, still they are a big puzzle!! So what do we need ideally, for the afterglow? Fast repointing (<1min) NIR telescope (1-1.5 m), good spectral resolution (R~3000) X-ray imaging (few arcsec) and high energy resolution (few eV)

 Many of these will be concerned with time-domain phenomena (and high-z). “The full realization of time domain studies is one of the most promising discovery areas of the decade.” - US Decadal review Tanvir, Paris presentation L2/L3

ATHENA Swift ALMA AdGW E-ELT CTA LSST JWST SKA Euclid Wide area, high energy is key to tying together many transient phenomena. Fast slewing, narrow field instruments enable detailed characterisation and follow-up. “The single most important message...is that we cannot afford to be without a satellite localizing GRBs in the era of m optical/ IR telescopes” – Richard Ellis, summary of “Feeding the Giants” conference. Tanvir, Paris presentation L2/L3

Even post-JWST there will likely be crucial unsolved questions regarding formation of first stars and galaxies:  An increasing (dominant) proportion of high-z star formation appears to be taking place in intrinsically very faint galaxies, beyond the reach of JWST at z>8 ; the nature of those galaxies will hardly be known, but they will be GRB hosts.  Spectroscopy of even bright z>8 galaxies, with JWST and ELT will provide only limited information on global chemical evolution, which is key to understanding the earliest generations of stars; GRB afterglows will provide bright backlights for spectroscopy, and could give reliable redshifts even at z>13.  There may be no direct detections of population III sources; pop III collapsars predicted to produce GRB-like events.  Experiments such as LOFAR and SKA may tell us when reionization occurred, but not directly how it occurred, which requires identifying the sources responsible and determining the escape fraction of ionizing radiation from them; GRBs allow us to map global star formation and study escape fraction and IGM neutral fraction via spectroscopy. Tanvir, Paris presentation L2/L3

Athena : the first stars and black holes When did the first generation of stars explode to form the first seed black holes and disseminate the first metals in the Universe? How do black holes grow and shape the Universe? Jonker, O'Brien et al., 2013 arXiv Gamma Ray Burst at z=7

CONCLUSIONS The study of GRB provides a lot of opportunity, nevertheless it is very unlikely that we will have a good mission in the next years!! But having a good GRB machine in the future is fundamental also for other research area (e.g. High-z, GW) We have to work together with other communities (GW, transient, SNe, early Universe, SFR, metallicity & galaxy evolution ….) to strengthen our case and succeed in getting a good mission in the timescale

CONCLUSIONS In any case we definitively need a high energy transient discovery mission in the period good enough to work with E-ELT, JSWT, AdWG, SKA, CTA, LSST

10 years of Swift

BACK-UP

GAME: GRB and All Sky Monitor Experiment XRM: X-ray Monitor Si drift detectors (SDD) 1-50 keV 3 sr FCFoV Localisation <1 arcmin Sensitivity: 0.3 crab in 1s; 2 mCrab 50ks HXI: Hard X-ray Imager CZT detectors keV 20 o x20 o FWHM FoV Localisation ~30 arcmin Sensitivity 1 Crab in 1s 10 mCrab 1 day SGS: Soft Γ-Ray Spectrometer Phoswich scintillators keV 2.5 sr FWHM FoV Sensitivity 1 Crab in 1s 10 mCrab 1 day

A-STAR A-STAR accommodated on a rapid-slewing Myriade Evolutions platform for a Vega launch into a 30° low- earth orbit. Prompt alert downlink is via a HETE-like VHF subsystem. All sky survey pointings will be 20 mins each, resulting in 2 observations of every field per day and an exposure of 1 Msec per field per year. FOV 17x52° Energy band keV Positions50% <30” Sensitivity4x erg.cm -2.s in 10 3 s FOV 60x88° Energy band4-150 keV Positions2-10’ Sensitivity2x erg.cm -2.s in 10 3 s Owl (IRAP, Toulouse & CEA, Saclay) Lobster (Leicester + B/I/DK/PL/CH) 1 Swift XRT c/s is detectable in a single Lobster pointing. Julian Osborne (University of Leicester). Explosive Transients. Santorini Sept 2013

GAME: GRB and All Sky Monitor Experiment

Lobster wide-field focussing: Julian Osborne (University of Leicester). Explosive Transients. Santorini Sept 2013

Lobster development based on micro-channel optics in the MIXS instrument on ESA’s BepiColombo mission to Mercury Julian Osborne (University of Leicester). Explosive Transients. Santorini Sept 2013