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A GRB in a slide

A GRB in a slide. Short (< 10 3 sec) intense emission episodes of high energy g -ray photons. 1973-1997. PROMPT. ... accompained by a considerable long lasting emission at lower energies (X-ray, Optical, IR and Radio). > 1997. AFTERGLOW. g -ray. X-ray. Optical. … … ….

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A GRB in a slide

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  1. A GRB in a slide Short (< 10 3 sec) intense emission episodes of high energy g-ray photons... 1973-1997 PROMPT ... accompained by a considerable long lasting emission at lower energies (X-ray, Optical, IR and Radio) > 1997 AFTERGLOW g-ray X-ray Optical … … …

  2. A serendipitous discovery 5 August 1963 US + UK + USSR sign the LTBT=Limited Test Ban Treaty, banning nuclear weapon tests in the atmosphere, in outer space, and under water. Vela Space Program (1963-1965 ... 1968, 1969, 1970 ) Detect nuclear explosion from: • Earth • Dark side of the moon • Space X-ray monitor(2-20keV) g-ray monitor(>150keV)

  3. E > 100 keV Few seconds (probably) The First Gamma Ray Burst Exclude earth and moon

  4. BeppoSax (1996-2002) (Italian-Dutch satellite for X-ray astronomy) Wide Field Camera (WFC) (2-30 keV; 20x20 degree FOV angular resolution 5 arc min) The scintillator (anti-coincidence shields of the Phoswich detector) are able to detect gamma-rays 60-600 keV and get crude angular information

  5. The answer to the “great debate” 28 Feb 1997 E>40 keV SAX The burst is somewhere here… but where ? GRB 970228 is in the FOV of the WFC Afterglowdiscovery: emission from the burst in the X ray • Fading • Well localized Groot, Galama, von Paradijs, et al IAUC 6584, March 12, 1997

  6. The answer to the “great debate” HST GRB Host Galaxy OT=Optical Transient

  7. Since Nov. 2004 UVOT BAT BAT XRT UVOT XRT Spacecraft Spacecraft BAT Error Circle Swift: “everything in space” • T<10 sec • < 4‘ E>15 keV T<100 sec  < 5'' E<10 keV Satellite slews (1 min) and repoints its X ray (XRT) and UV telescopes to observe the error region of the GRB. T<300sec Optical/NIR

  8. Prompt: light curve diversity Prompt

  9. Se fotone ha energia > 2 me di un elettrone si producono coppie ma in gamma burst noi vediamo GeV fotoni Un fattore di Lorentz dell’ordine di 200-300 fa si che nel sistema di riferimento della sorgente non si abbia opacita’ per due motivi: Doppler factor relativistico aumenta la frequenza (energia) osservata di un fattore D La variabilita’ osservata e’ amplificata di un fattore D per cui le dimensioni della regione emittente hanno un volume maggiore di un fattor D^3 da cui la scarsa opacita’

  10. ENERGY VOLUME E(iso) ~ 1052 - 54 erg tvar ~ 10 ms R ~ 107-8 cm ... build up the standard model ... Huge amount of energy in a small volume = FIREBALL

  11. The standard model: Fireball E~1052 erg Shells are optically thick. Internal pressure (due to high energy density) drives the accelerationand internal energy is converted into kinetic energy. Central Engine ?? G r

  12. The standard model: Fireball + Internal shock Shock Shock transfers energy to the particles and magnetic field E~1052 erg Prompt emission is synchrotron Central Engine ?? G Most of the internal energy has been converted into kinetic and the shell coast with constant G r

  13. The standard model: Fireball + Internal +External shock GRB AFTERGLOW E~1052 erg Central Engine ?? Merged shells are decelerated by the ISM G r

  14. The standard modell: Fireball + Internal +External shock GRB AFTERGLOW E~1052 erg Q: What is the “central engine”? Progenitor & Central Engine ?? Merged shells are decelerated by the ISM G r

  15. At these distances gamma-ray bursts would have an energy of 1052 erg to 1054 erg if they emitted isotropically. That is up to the rest mass of the sun turned into gamma-rays in 10 seconds!

  16. The standard model: Fireball + Internal +External shock GRB AFTERGLOW E~1052 erg Central Engine ?? Merged shells are decelerated by the ISM G r

  17. Long GRB are in SF regions where most massive stars occur

  18. SN 1998bw GRB 980425 GRB SN connection – The first Type Ic supernova, d = 36 Mpc Etot ~ 3 x 1052 erg V=3x104 Km/s of a massive CO star (Iwamoto et al 1998; Woosley, Eastman, & Schmidt 1999) GRB E ~ 8 x 1047 erg; T= 23 s

  19. Ia binaria con nana bianca – no H vecchie II stella massiccia  Fe56 – si H giovani Types Ib and Ic supernovae are caused by the core collapse of massive stars. A Wolf-Rayet star, with a core of about 10 solar M These stars have shed (or been stripped of) their outer envelope of hydrogen, and, when compared to the spectrum of Type Ia supernovae, they lack the absorption line of silicon. Compared to Type Ib, Type Ic supernovae are believed to have lost more of their initial envelope, including most of their helium. The two types are usually referred to as stripped core-collapse supernovae

  20. GRB/SN Connection – a few GRB 980425 (40 Mpc) GRB 030329 (z=0.17) GRB 031203 (z=0.1) GRB 060218 (150 Mpc) (Galama et al. 1998, Matheson et al. 2003, Malesani et al. 2004, Pian et al. 2006)

  21. GRB/SN are more luminous SN1998bw SN2003dh SN2003lw SN2006aj

  22. Woosley and Bloom (2006)

  23. The Collapsar model: BH + (fed) disk

  24. Today, there are two principal models being discussed for GRBs of the “long-soft” variety: • The collapsar model • The millisecond magnetar Glatzmaier MacFadyen and Zhang (2005)

  25. qjet= 0.1rad; Ljet = 1050-1051 erg/s Long GRB central engine ms magnetar (NS) Collapsar (BH+disk) Supranova (delayed BH+disk) B~1015 G M>Mcrit Delay ~ year (clean environ) “Cold” fireball “Cold & Hot” fireball Adv: fallback

  26. Progenitors (current paradigm) Still controversial e.g. both early and late type galaxies Short (t< 2 s) • Supported by: • Hosts • Position within hosts • Direct association with SNIbc Long (t> 2 s)

  27. Short Gamma-Ray burst cannot be produced in SN Their location is not only in star formation regions  Figure 7. Snapshots of simulation of two neutron stars merger (each neutron star has 1.4M8 and ≈ 30 km diameter). Initially, they are less than 10 km apart, and moving at around v = 0.2c.

  28. From simulations: Merger time: Inspiral phase: 106 yrs Final 100 km less than 1 second Crash: 15 millisecond spinning black hole magnetic field amplification magnetic tower 11 millisecond: jets

  29. FireballModel • If  notuniform, fastershells collide withslowerones, and internalshocksform • Part of the kineticenergyisconverted in internal promptemission • Formationof a GRB couldbegineitherwith the mergeroftwo compact objects or with the collapseof a massive star • As a result, anenergyas high as E~1054 ergs can be released in a compact volume of space (~106 cm) • Afireballofe+/e- pairs, photons and baryonsisformed and expandsconvertingthermalenergy in bulk kineticenergycarriedby the baryonsoriginallypresent in the explosion site (Mb) • When the thermalmotionbecomessub-relativistic, the bulk Lorentzfactorsaturatesto=E/Mbc2 • The fireballexpands and collects ISM • Itstartstobedecelarated and anexternal shock forms • The initalevolutionisinverted: bulk kineticenergyisconvertedintointernalenergyacross the shock front • The acceleratedelectrons radiate via synchrotronemissionafterglowemission ~1016 cm ~1013 cm

  30. The fireball model E.g. afterglow phase: emission processes, circum-burst medium (density and structure) How to derive clues on the nature of the progenitor? n < 1 cm-3 and uniform medium d I will consider the link with the GW domain n~102-104 cm-3 and evidence for a stellar wind n  r-2 ~1016 cm ~1013 cm

  31. Figure 11. Light from a GRB and its afterglows travels on its way to the Earth through circumburst medium, host galaxy medium and intervening absorbers. All of these may imprint their signature in the spectrum. From left to right: clouds of gas in the early universe collapsed to form the first (Pop III) massive stars, which probably produced the first GRBs. GRBs may have preceded the formation of the first galaxies and active galactic nuclei/quasars, which are powered by supermassive black holes and formed even later. Thus, GRBs may probe the properties and environment of the first stars and galaxies in the Universe, as well as properties of the intervening absorbers

  32. Peakenergy vs. Trueenergy cr2=1.27 Epeak Etrue0.7 Ghirlanda, Ghisellini, Lazzati 2004 Epeak(1+z) Epeak(1+z)

  33. E=1051 erg Luminosity distance Stretch-lum (SNIa) Ep-Eg correlation (GRB) Luminosity distance redshift E=1051 erg Luminosity distance The correlationreduces the scatterofGRBs in the HubbleDiagram GRBs can beusedascosmological RULERS ! redshift JGRG 17 – G.Gh.

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