1. Unifying afterglow diversity Gabriele Ghisellini INAF-Osservatorio Astronomico di Brera - Italy with the help of G.Ghirlanda and M. Nardini

2. X-ray and optical often behave differently ~same spectrum TATATATA Is this “real” afterglow? i.e. external shock? X-ray What is T A ? optical

3. 2 Component model Component 1: Standard afterglow.Component 1: Standard afterglow. Standard=forward shocks in the ISM (e.g. Panaitescu & Kumar 2000) Component 2:Component 2: Completely phenomenological. Used for the “flat-steep” part of the light curve. Constant SED (minimum # of parameters). Both componentsBoth components emit optical and X-rays

4. X-ray optical

5. X-ray Afterglow Optical Afterglow Standard afterglow theory (Panaitescu & Kumar 2000)

6. Component 2 Component 2: completely phenomenological at this stage

7.  flat  steep

8. Sum Sum

9. X-ray optical

10. Optical Afterglow X-ray Afterglow

11. Component 2

12.  flat  steep

13. Sum Sum

14. Good fits for all 33 GRBs in the sampleGood fits for all 33 GRBs in the sample What is “component 2”?What is “component 2”?

15. ~5/3 Decay index of steep part of comp 2  steep

16. ~70 Swift GRBs with z X-rays

17. t -5/3

18. t -5/4

19. Ghisellini+ 2009 Comp 2

20. Lazzati+ 2008 t -5/3 From averaging the luminosity of flares in different GRBs

21. MacFadyen+ 2001 t -5/3 M from fallback

22. Zhang Woosley Heger 2008 10 6 10 5 10 4 10 3 Time [s] Fallback lasts for quite a long time M from fallback

23. Fallback Prolonged activity of the central engineFallback Prolonged activity of the central engine Can we explain T A ?Can we explain T A ?

24. Early (normal) prompt: Early (normal) prompt:  >>1 /  j Late prompt: Late prompt:  >1 /  j Late prompt: Late prompt:  =1 /  j Late prompt: Late prompt:  <1 /  j ”real” after- glow Ghisellini et al. 2007 Strong, erratic Smooth After the early prompt, the central engine decreases energy and decreases  monotonically R~10 13 cm

25. Early (normal) prompt: Early (normal) prompt:  >>1 /  j Late prompt: Late prompt:  >1 /  j Late prompt: Late prompt:  =1 /  j Late prompt: Late prompt:  <1 /  j ”real” after- glow Ghisellini et al. 2007 R~10 13 cm TATATATA T jet

26. Conclusions 2 components can explain the diversity2 components can explain the diversity Component 2 can be associated with the prolonged activity of the entral engineComponent 2 can be associated with the prolonged activity of the entral engine Fallback is long  late prompt “forever”Fallback is long  late prompt “forever” Flares as accretion of denser chunks of fallback materialFlares as accretion of denser chunks of fallback material T A can be explainedT A can be explained Next…Next…

27. NEXT (Marco Nardini): Can we also explain the presence/absence of jet breaks?Can we also explain the presence/absence of jet breaks?

29.  ~ t -   /2 t-2t-2t-2t-2 t-3t-3t-3t-3 Time Flux M out ~ t -(      ) /2 TATATATA L   M out ~ t -  

30.  ~ t -   /2 t-2t-2t-2t-2 t-3t-3t-3t-3 Time Flux M out ~ t -(      ) /2 Long lasting engine with two-phase accretion? 1: Very dense torus, large B-field, erratic. 2: Less dense material, smaller B-field, smoother accretion – Fallback? TATATATA L   M out ~ t -   L~ M accr ? Very cheap

31. SEDs vs light curvesSEDs vs light curves Tests Log F Log F Log Log optical X-rays

32. SEDs vs light curvesSEDs vs light curves Some GRBs with no plateau: achromatic breaks?Some GRBs with no plateau: achromatic breaks? Tests

33. SEDs vs light curvesSEDs vs light curves Some GRBs with no plateau: achromatic breaks?Some GRBs with no plateau: achromatic breaks? Late ‘jump’ in X-ray light-curves revealing real X-ray afterglowLate ‘jump’ in X-ray light-curves revealing real X-ray afterglow Tests TATATATA Jump=end of late prompt Time X-ray Flux