GRB in the Swift Era and beyond

Transcription

1 GRB in the Swift Era and beyond Peter Mészáros Pennsylvania State University 1

2 GRB: basic numbers Rate: ~ 1/day inside a Hubble radius Distance: 0.1 z 6.3! D ~ cm Fluence: ~ erg/cm 2 ~ 1 ph/cm 2 (g-rays!) Energy output: (Ω/4π) D F -5 erg but, jet: (Ω j /4π) ~ 10-2 E γ,tot ~ 1051 erg E γ,tot ~ L Θ x 1010 year ~ L gal x 1 year Rate[GRB (γ-obs)] ~10-6 (2π/ Ω) /yr/gal 1/day (z 3) but Rate [GRB (uncollimated)] ~ 10-4 /yr/gal, while Rate [SN (core collapse] ~ 1O -2 /yr/gal, or 10 7 /yr ~ 1/s (z <3) Mészáros Tok06

3 3

4 GRB: standard paradigm Bimodal distribution of t γ duration Short (t g < 2 s) 3d group? Long (t g >2 s)

5 BH + accr. Torus Jet Both collapsar or merger BH+accr.torus fireball Massive rot. *: sideways pressure confines/channel outflow fireball Jet Nuclear density hot torus can have nn e ± jet Hot infall convective dynamo B~10 15 G, twisted (thread BH?) Alfvénic or e ± pγ jet (Note: magnetar might do similar) Mészáros, L Aqu05

6 Explosion FIREBALL E γ ~ Ω -2 D F -5 erg R 0 ~ c t 0 ~ 10 7 t -3 cm Huge energy in very small volume τ γγ ~ (E γ /R 3 0 m e c2 )σ T R 0 >> 1 Fireball: e ±,γ,p relativistic gas L γ ~E γ /t 0 >> L Edd expanding (v~c) fireball (Cavallo & Rees, 1978 MN 183:359) Observe E γ > 10 GeV but γγ e ±, degrade 10 GeV 0.5 MeV? Eγ Et >2(m e c 2 ) 2 /(1-cosΘ)~4(m e c 2 ) 2 /Θ 2 Ultrarelativistic flow Γ Θ -1 ~ 10 2 (Fenimore etal 93; Baring & Harding 94) Mészáros, L Aqu05

7 Relativistic Outflows Energy-impulse tensor : T ik = w u i u k + p g ik, u i : 4-velocity, g ik = metric, g 11 =g 22 =g 33 =-g 00 =1, others 0; ultra-rel. enthalpy: w = 4p n 4/3 ; w, p, n : in comoving-frame 1-D motion : u i =(γ,u,0,0), where u = Γ (v/c), v = 3-velocity, A= outflow channel cross section : Impulse flux Q=(w u 2 +p) A energy flux L= wu Γ c A particle number flux J= n u A Isentropic flow : L, J constant w Γ /n = constant (relativistic Bernoulli equation); for ultra-rel. equ. of state p w n 4/3, and cross section A r 2 n 1 / r 2 Γ comoving density drops Γ r bulk Lorentz factor initially grows with r. But, eventually saturates, Γ E j /M j c 2 ~ constant Γ r

8 Shock formation Collisionless shocks (rarefied gas) Internal shock waves: where? If two gas shells ejected with Δ Γ = Γ 1 -Γ 2 ~ Γ, starting at time intervals Δt ~t v,, they collide at r is, r is ~ 2 c Δt Γ 2 ~ 2 c t v Γ 2 ~ 1O 12 t -3 Γ 2 2 cm (internal shock) [Alternative picture: magnetic dissipation, reconnection] External shock : merged ejected shells coast out to r es, where they have swept up enough enough external matter to slow down, E=(4p/3)r es 3 n ext m p c 2 Γ 2, r es ~ (3E/4pn ext m p c 2 ) 1/3 Γ -2/3 ~ 3.1O 16 (E 51 /n O ) 1/3 Γ 2-2/3 cm (external shock)

9 Fireball Model: long GRBs E.g., recent review on GRB-Swift results & implications: Mészáros, 2006, Rev.Prog.Phys 69:2259 (astro-ph/ ) External Shock Internal Shock Collisions betw. diff. parts of the flow The Flow decelerating into the surrounding medium GRB Afterglow X O R Mészáros grb-glast06

10 Internal & External Shocks in optically thin medium : LONG-TERM BEHAVIOR Γ r c r i r e R ø r Internal shocks (or other, e.g. magnetic dissipation) at radius r i ~10 12 cm γ-rays (burst, t γ ~sec) External shocks at r e ~10 16 cm; progressively decelerate, get weaker and redder in time (Rees & Meszaros 92) Decreasing Doppler boost: roughly, expect ~1 week, ~1 day (Paczynski, & Rhoads 93, Katz 94) PREDICTION : Full quantitative theory of: External forward shock spectrum softens in time: X-ray, optical, radio long fading afterglow (t ~ min, hr, day, month) External reverse shock (less relativistic, cooler, denser): Prompt Optical quick fading ( t ~ mins) (Meszaros & Rees 1997 ApJ 476,232)

11 Standard External Forw. & Rev. Shock Synchroton & IC spectrum Lower energy: Synchrotron (reverse: ev, forward: MeV) F:sy F:IC Higher energy: Inv. Compton (forward: GeV) R:sy

12 Shock Photon Spectrum E 2 N E F E Sy t t IC E Non-thermal power law spectrum, both in int. and ext. shocks, due to Synchrotron, peak at ~200 kev (or ~ ev?) Inv. Compton, peak ~ GeV (or ~200 kev? Sy peak location, ratio Sy/IC dep. on B sh, γ e, Γ E Peak softens with time Ratio Sy/IC decr w. time

13 GRB : BeppoSAX Discovery of an afterglow Feb 28 March 3 F_x ~3E-12 erg.cm2/kev/s, decr. By 1/20 (Costa et al 1997, Nature 387:783) X-ray location:2-3 arcmin raster optical (arcsec) & radio location Can identify host galaxy, redshift located at cosmological dist. NEW ERA! Mészáros, L Aqu05

14 GRB afterglow blast wave model GRB as blast wave: Wijers, Rees & Mészárosl 97 MNRAS 288:L51 fit to Simplest case: adiabatic forward shock synchrotron rad n from shockaccel. non-thermal e - F(ν,t) ν -β t -α α = (3/2) β Parameters E 0, ε e, ε B, (β=(p-1)/2) Mészáros, Rees 97 ApJ 476:232 model Mészáros, L Aqu05

15 Snapshot Afterglow Fits Simplest case: t cool (γ m ) >t exp, where N(γ) γ -p for γ>γ m (i.e. γ c(ool) >γ m ) 3 breaks: ν a(bs), ν m, ν c F ν ν 2 (ν 5/2 ) ; ν<ν a ; ν 1/3 ; ν a <ν<ν m ; ν- (p-1)/2 ; ν m <ν<ν c ν -p/2 ; ν>ν c (Mészáros, Rees & Wijers 98 ApJ 499:301) Mészáros, L Aqu05

16 Collapsar & SN : a direct link - but always? Core collapse of star w. Mt~30 M sun BH + disk (if fast rot.core) jet (MHD? baryonic? high Γ, + SNR envelope eject (?) 3D hydro simulations (Newtonian SR) show that baryonic jet w. high G can be formed/escape SNR: not seen numerically yet (but: several suggestive observations, e.g. late l.c. hump + reddening; and.. Direct observational (spectroscopic) detections of GRB/ccSN Collapsar & SN ANIMATION Credit: Derek Fox & NASA Mészáros, L Aqu05

17 Collapsar & ccsn : GRB SN 2003dh & others 2 nd Nearest unequivocal cosmological GRB: z=0.17 GRB-SN association: strong Fluence:10-4 erg cm -2, among highest in BATSE, but t γ ~30s, nearby; E g,iso ~ erg: ~typical, E SN2003dh,iso ~ erg ~ E SN1998bw,iso («grb980425) v sn,ej ~0.1c ( hypernova ) GRB-SN simultaneous? at most: < 2 days off-set (from opt. lightcurve) ( i.e. not a supra-nova ) But: might be 2-stage (<2 day delay) *- NS-BH collapse? ν predictions may test this! Some others: GRB /SN2003lw; - GRB /SN2006aj;... Mészáros, L Aqu05

18 Light curve break: Jet Edge Effects Monochromatic break in light curve time power law behavior expect Γ t -3/8, as long as ϑ light cone ~Γ -1 < ϑ jet, (spherical approx is valid) see jet edge at Γ ~ ϑ jet -1 Before edge, F ν (r/γ)2.i ν After edge, F ν (r ϑ jet ) 2.I ν, F ν steeper by Γ 2 t -3/4 After edge, also side exp. further steepen F ν t -p Mészáros, L Aqu05

19 GRB : evidence for SN evidence for refreshed shock and evidence for 2-comp. jet: ϑ γ ~5 o < ϑ radio ~17 o Berger etal 03, Nature 426, 154 More recently (Swift): several XR light-curve breaks, but: conflicting evidence for (a?)chromatic breaks Mészáros, L Aqu05

20 Jet Collimation & Energetics Frail et al 01 Jet opening angle inv. corr. w. L γ (iso) L γ(corr) ~ const. Mean collim. correction <(4π/2ΔΩ j )> ~ 10-2 GRB030329: 2-comp. jet? Berger etal 03 ϑ g ~5 o < ϑ radio ~17 o E total = E γ +E kin ~ const. ( quasi-standard candle ) Mészáros, L Aqu05

21 E pk vs E γtot Better correl. than E pk vs E γiso (?) Ghirlanda, Ghisellini, Lazatti, aph/ (see also Friedman & Bloom, aph/ ) E pk Eγ 0.7 Mészáros, L Aqu05

22 z-measures? Variability V vs. E γ, iso (Fenimore, Ramirez-Ruiz, Reichart..) Lag vs. E γiso (Norris, Bonnell,..) Hardness (Epk) vs. E γ,iso (Amati etal, Bagoly etal, Schmidt..) E pk vs. E γ,jet (Ghirlanda et al 04) Epk vs. Eiso vs. tbreak (Liang & Zhang 05) Epk vs Eiso vs. t0.45 (Firmani et al, 06; where t0.45 ~ V) Mészáros, L Aqu05

23 Reasons for Amati - Ghirlanda? E.g, internal shocks, E p ~ E sy ~ ΓB'γ e 2 ~ΓB' ~ B ~ U 1/2 ~ (L/r 2 ) 1/2 ~ L 1/2 t v -1 Γ -2 (Zhang, Mészáros 02 ApJ 581, 1236) ( since r~ ct v Γ 2 - but, is t v, Γ ~ const. for diff. L? ) E.g photospheric characteristic temperature, E p ~ Γ T ~ Γ (L/Γ 2 r ph2 ) 1/4 ~ Γ 2 L -1/4 (since r ph ~ L/Γ 3 ) ; if use Frail : L ~ θ -2, and causality : Γ~ θ -1 E p ~ L 3/4 (Rees, Mészáros 05 ApJ 628, 847) If photosphere is at known radius of WR *, E p ~ Γ T ~ Γ (L/Γ 2 R *2 ) 1/4 ~ Γ 1/2 L 1/4 ; bulk of fluid moves at Γ~3-1/2 θ -1 since outside that KH mix E p ~ L 1/2 (Thompson astroph/ ; Thompson, Meszaros & Rees, aph/ ) Mészáros, L Aqu05

24 Optical Flash : GRB ROTSE GRB 9mag! (z=1.6) (Akerlof et al. 1999; Meszaros & Rees 1997; Sari & Piran 1999; Kobayashi 2000) Mészáros, L Aqu05

25 Prompt Optical Flashes nf n Sy (forw) Sy (rev) 0 X,g n GRB bright (9 th mag) prompt opt. transient (Akerlof etal 99) 1st 10 min: decay steeper than forw. shock Interpreted as reverse external shock (pred : Mészáros&Rees 97) 99-02: Great Desert: Lack of flashes, upper limits m v ~12-15 but: New generation robotic tels: ROTSE III, Super-LOTIS, RAPTOR, KAIT, TAROT, NEAT, Faulkes, REM; etc more prompt optical flashes, e.g. : GRB , ; and new semi- prompt flashes : GRB , : GRB ! t >211, 50 s resp, see forw. shock only? and now... Swift era: GRB A (Raptor; Vestrand 05); GRB (Raptor; Wozniak et al 05) GRB (Rotse III, Quimby et al, 05) GRB (Rotse III, Rykoff et al 05) GRB (TAROT, Gendre et al, 06) GRB (Raptor, Wozniak et al, 06) Mészáros, L Aqu05

26 Cosmology with GRBs? High-z GRB distance measures Positive K-correction: flux ~ constant at z 3 Optical/UV: Ly α cutoff redshift out to z<5 for Swift Forward shock exp. fluxes O/IR Lamb, Reichart 00 Ciardi & Loeb 00 Mészáros, L Aqu05

27 IR & XR hi-z detectability XR detectability O/IR zx detectability ROTSE V-band Chandra K-band Swift JWST Gou et al, 03, ApJ 604:508 Mészáros, L Aqu05

28 BAT: Energy Range: kev FoV: 2.0 sr Burst Detection Rate: 100 bursts/yr SWIFT Three instruments Gamma-ray, X-ray and optical/uv Slew time: s! >95% of triggers yield XRT det >50% triggers yield UVOT det. UVOT: Wavelength Range: nm XRT: Energy Range: kev Launched Nov 04 Mészáros, L Aqu05

29 SWIFT: New Results > 140 new afterglows localized since launch Redshifts for >40 long GRB and 4 short GRB <z long > ~ , which is 2x Beppo-Sax distance (i.e. significantly fainter & redder, than Beppo-Sax afterglows!) <z short > ~ ; L short ~ 10-2 L long ; compact merger XR light curves (10 2 s-10 4 s): new features (both long and short) - steep + shallow decay, flares evidence for continued activity? In the period 1 min < t < hrs, new features show up, which may be natural extensions of the standard burst & AG model (or..?)

30 SWIFT: New Results, cont. Short bursts localized, hosts identified, redshifts measured VHZ (very high redshift) bursts: several >5, one 6.29 Prompt optical/ir flashes (one very bright) GRB/SN, at least two spectroscopic, more...

31 New features seen by Swift : A Generic X-ray Lightcurve ~ -3 new old ( 1 min t hours ) ~ -0.5 ~ s s s ~ -2 BUT: not all features in all bursts

32 Afterglow: when does it start? standard interpretation: AG starts at t dec ~ (3/4) (r dec /2 c Γ 2 ) (1+z) ~ (3/8 c Γ 2 )(3E/4π n m p c 2 Γ 2 ) 1/3 (1+z) ~ 10 2 (E 52 /n 0 ) 1/3 Γ 2-8/3 (1+z) s But, for prompt duration T=T γ =T outflow ~ T90 - Thin shell : T < t dec AG start at t dec above - Thick shell : T > t dec AG start at T~T γ ~T90

33 Example : GRB Vaughn et al t -5.2 ν -1.9 ± t -0.4 t -0.7 ν ±0.11

34 Initial steep drop: F x (t-t 0 ) - α Current bet: tail end of GRB (high latitude emission) : radiation from outside main beam, θ>γ -1 - arrives at t ~ Rθ 2 /2c later than from θ~0, - is softer by D~t -1 (Nousek et al 05, Zhang et al 05, Panaitescu et al 05)) expect α=2+β, where F~ t α ν β (Kumar, Panaitescu 00) ~ OK, generally; departures may be understood Possible alternatives: - Cocoon radiation escape (Pe er, et al, ApJ 06 in press, aph/...) - Photopion rapid cooling --> drop (Dermer, 06, aph/...)

35 Radiation Components: Initial rapid decay: High latitude emission : Prompt γ-rays (GRB) from l.o.s. angles θ < Γ -1 2 : tail-end of GRB, from high latitude emission : γ-rays emited promptly, but from angles θ >Γ -1 ; arrive at time t ~ Rθ 2 /2c later than from θ~0, and is softer by D~t -1 ; expect α=2+β, ~ OK 3 : afterglow, from forward shock at l.o.s.angles θ < Γ -1 ; later than (or partially overlap with) high latitude comp. (2)

36 High latitude issues Time slope α depends on choice of t 0 can fit t 0 such that slope is satisfied i.e., determine t dec? (Liang et al astroph/ ) When T > t dec (and also when T< t dec ) can have an admixture of (a) afterglow (l.o.s) θ<γ -1, and (b) high latitude θ>γ -1 components. Generally β prompt <β steep, so can accommodate steeper decays than 2+ β prompt (O Brien et al, 05) Flares: t 0 fit can give pulse ejection time by engine (Liang et al 06) Structured jet: for on-beam viewing jet shape has little effect, but off-beam can get shallower slope (Dyks et al aph/ ) From initial steep decay slope, t 0 constraints suggest t 0 ~ t trigger, may infer prompt emission radius R γ (Lazzati, Begelman aph/ )

37 Retrofit: The t0 which fits the steep decay slope generally agrees with the onset of the rising segment of the last peak before the decay 37 Liang, et al aph/

38 Shallow decay Slope 0.3 α 1 : likely due to refreshed shock I.e. the forward afterglow shock receives continued reinforcement from late-arriving ejecta NOTE: late arriving, but not necessarily late ejected! (Rees-Meszaros 98, Panaitescu, PM, MJR 98, Kumar-Piran 00, Sari-Meszaros 00, Nousek et al 05, Zhang et al 05, Granot-Kumar 05)

39 Shallow decay (0.2 α 1) Slow Γ,refreshed Probably due to refreshed shocks, due either to: Long duration ejection (t ~ t flat ) ; or Short duration ejection (t ~ t γ ), but with range of Γ, e.g. M(Γ)~ Γ -s, E(Γ) ~ Γ -s+1, for ρ~r -g ext. medium : e.g. FS: α=[-4-4s+g+sg+β(24-7g+sg)]/[2(7+s-2g)] Rees+PM, 98 ApJ 496, L1 ; Sari +PM, 00, ApJ 535, L33 ; Zhang +PM 01, ApJ 552, L35 Note : Fit to Swift data Γ distrib. may be a broken power law (Granot, Kumar astro-ph/ )

40 Refreshed (shallow decay) Note : E Xshallow E γprompt [O Brien, et al, 06]. But in order for refreshed shock to dominate the afterglow, energy input in refreshed component needs exceed that in prompt either - rad n. effic. ε γ > ε x (eg prompt is Poynting dominated?..) or or - fraction of refreshed shock energy undetected (IR? GeV? ) - preactivity evacuates cavity, or fraction of energy into electrons t 1/2 (Ioka et al, astro-ph/ Alternative : shallow decay due to emission from anisotropic jet lines of sight just outside sharp edge of main bright jet (Eichler-Granot astroph/ ) Other possibilities: - Ekin underestimated (also in BATSE), so ε γ is reasonable relative to ε x - Two-component jet (narrow-fast/broad-slow) (Granot, et al, astroph/ )

41 Giant X-ray Flare: GRB050502b 500x increase! GRB Fluence: 8E-7 ergs/cm 2 Flare Fluence: 9E-7 ergs/cm 2 Burrows et al. 2005, Science; Falcone et al. 2005, ApJ

42 XR Flares Main puzzles: - large energy E xfl E γprompt - steep rise/decay F (t-t 0 ) α, α~±3-6 Possible causes: - refreshed (forward) shocks (rise & decay too shallow) - reverse IC component (one shot affair- where is forward?) - interaction with external matter ( rise/decay slope?) - continued central engine activity, e.g. internal shocks, dissipation (difficult for central engine, but address temp. slope, total energy - less problematic than others?)

43 XR Flare triggers? Gravitational instability disk fragmentation lumpy accretion (Perna, Armitage, B.Zhang) MHD accretion- magnetic tension ( springy ) lumpy accretion (Proga & Begelman, Fan, Proga &B.Zhang) Short bursts: BH-NS disr (SPH GR numerical) prompt accretion + extended tail delayed lumpy accretion (Davies, et al 05; Lee et al 00, Rosswog et al 04; Laguna, Rasio 05)

44 MHD accretion? (Proga & Begelman 03) Accretion rate time

45 Main Possible Explanations of long GRB afterglow new features Initial drop: likely due to tail end of GRB (high latitude emission) : rad n from θ>γ -1 arrives at t ~ Rθ 2 /2c later than from θ~0, is softer by D~t -1 ; expect α=2+β, ~ OK Shallow decay: probably refreshed shocks, either from Longer ejection (t ~ t flat ) ; or Short ejection (t ~ t γ ), but with range of Γ, e.g. M(Γ)~ Γ -s, E(Γ) ~ Γ -s+1 Flares: likely due to continued central engine activity : main constraints: very sharp rise and decline (t ± 3 t ± 6 ) But: remains work in progress- depending also on new observations

46 Short & Long Afterglows Big question: are they the same? 0th order answer: looks like yes - initial steep decay - XR flares - normal forward shock decay - jet break But: 1st order differences are interesting - Avg. kin. energy/solid angle x100 smaller - Avg. jet angle x2 larger than in long bursts (Fox et al 05, Panaitescu 05)

47 Short Bursts b - Hosts: E, Irr, SFR (compat. W. NS merg, but: some SGR, other?) - Redshift : < 0.1 to ~ XR, OT, RT: yes (mostly) - XR l.c.: similar to long bursts? (XR bumps too- late engine?) b

48 SHB afterglow fits So far, > 11 shb afterglows, 5-6 hosts ( D. Fox talk, Nature 05) AG fits for (Irr), (E) (Panaitescu, aph/ ) Using fluxes and break times, standard ag model: Γ = 6.5 (E 50 /n 0 ) 1/8 t d -3/8, θ j =Γ(t b ) -1 θ j = 9 o (n 0 /E 50 ) 1/8 t bd 3/8, E j = πθ j2 E ~ n 0 1/4 (E 50 t bd ) 3/4 erg High /low dens. soln s: : θ j >6 o, 10-4 < n < 10-1 cm -3, E~3-300 x erg/s θ j >2 o, n < 10-5 cm -3, E~2-10 x erg/sr : θ j >8 o, 10-1 < n < 10 3 cm -3, E~1-50 x erg/sr but: GRB (Grupe et al, 06, in prep.) Chandra late obs.: no break seen. while: GRB A : Swift + 2 Chandra obs. : well defined jet break 4 days θj ~ 7 o, Ej ~ erg

49 Short burst paradigm: NS-NS or NS-BH merger BH + accretion Paradigm seems compatible with hosts, and (for Kerr BH-NS) some simulations suggest extended activity & flares simulation Laguna, Rasio 06; ( Preliminary )

50 BH-NS merger? (Laguna & Rasio 06) Schwarz.BH-NS Kerr-proBH-NS 50

51 Prompt optical afterglows R γ Gou et al 04 O F O expected behavior: reverse shock causes prompt (10 s of sec) bright (m V 9) optical flash, decaying much faster than longlasting forward shock optical afterglow (Mészáros-Rees 97) First seen in GRB Rotse (Akerlof et al 99), and few other bursts, but rare : why? Could be that - rev.shock hi-mag suppress? - pair formation spec. to IR? - rev. shock rel. spec. to UV? Latest : GRB (z=6.29) shows prompt bright opt flash!

52 (time-dilated hi-z grb) ( usual low z grb) Most distant long burst from Swift ( z=6.29 ): GRB Discovered/localized by Swift BAT, XRT, UVOT Prompt ground I,R band TAROT, P60 upper limits, Detection J=17 mag FUN/SOAR, VLT photometric z >6 Spectroscopy Subaru 8.5 t=3.5 day : z = 6.29!

53 GRB as an XR beacon At a redshift z=6.29 (~reionization; most distant known known QSR: z~ 6.4) GRB X-ray flux exceeded that of the brightest known X-ray QSO SDSS J , by up to x10 5, for days SDSS J0130 (multiplied by 100) [ Watson et al 06 ApJ 637:L69 ]

54 Swift XRT TAROT (O/UV) Prompt O/UV flash as bright as (~ 9th mag!) at same z (rev. shock..) E iso ~ erg, similarly very high ;decay similarly steep (~ t -3 ) Observed at nm by TAROT (25 cm tel.!) [Boer et al, astro-ph/ ]

55 Why and ? Need high E iso ~ erg? (or small beam?) If reverse shock rest frame spectrum in UV (relativistic reverse shock?) ground O/IR: need high z (or else need enough rest-frame spectrum extending redwards of Lyα, so not absorbed) Need burst with strong flares (weak smooth afterglow component)? Other non-obs. or weak flash: pair formation, or weak field in ejecta rest-frame spectrum shifted to IR?

56 Origin of prompt Opt-flash 4 prompt optical flashes have been measured while the gamma-rays were still in progress in some (GRB , Boer et al, astro-ph/ ; also GRB a, Vestrand et al, astroph/ ) - prompt optical l.c. correlates with gamma-rays emission from the same region? (e.g. internal shock? ) in others (GRB , Rykoff et al astroph/ , GRB , Akerloff et al 00) - prompt optical l.c. does NOT correlate with gamma-rays emission from different region? (e.g. reverse shock?) 56

57 Different prompt gamma/opt correlations? Vestrand et al, 06, aph/

58 GRB / SN 2006aj Campana et al, Nature in press, astro-ph/ Long(est) BAT T90 = 2100 s duration XRT after 100 s, rising to max at ~1000s, followed by steep decay, then PL decay UVOT brightening to UV 30ks and later O 40ks, decay to XR non-thermal plus increasing BB component which dominates before the steep (ktbb ~ 0.17 kev) 58

59 GRB / SN 2006aj UVOT Interpreted as shock break-out of an anisotropic, semi-relativistic component from an optically thick progenitor stellar wind (Campana et al 06; Note: Fan-Piran alternate model: their objections apply to spherical single component, whereas here assumed 2+ components, anisotropic semirelativistic + spher. envelope) BB comp. temp. & radius

60 Conclusions Swift is significantly expanding our view & understanding of afterglows New early XR, O features appear to be understandable within context of standard afterglow model, with (not quite mastered) extensions Understanding of new XR smooth features is reasonable, but fluid dynamics remains controversial - and MHD may play a large role. XR flares are significant challenge, also for progenitor, central engine Relation of early XRT, UVOT to BAT flux levels pose challenges to prompt GRB gamma-ray mechanisms (efficiencies, etc..) Commonality & differences between short and long GRB afterglow features will yield important clues, need much further work (diff. due to lower E iso, broader θ jet, E vs. Irr, Sp hosts?) Information on long and short GRB jet breaks (collimation) not very extensive yet, possibly due to higher avg. z and lower fluxes? O/UV late afterglows largely support forward shock AG interpretation Prompt O/IR flash detection may hold vital clues (rareness? reverse shock interpretation? other..?) Potential for high-z IGM probing, SFR mapping appears poised for transition from wish to actual data to be modeled cosmology.