Central engine activity as seen in Naked-Eye Burst prompt emission

1. Central engine activity as seen in Naked-Eye Burst prompt emission G.Beskin, S.Karpov, S.Bondar, A.Guarnieri, C.Bartolini, G.Greco, A.Piccioni

2. Gamma-Ray Bursts:origin • E=1051-1054 erg — comparable to the rest-energy of the Sun • the collimation is necessary — so, let there be jets • Compact objects merging and formation of black hole • NS+NS, NS+BH • Orbital motion -> collimation • Old objects in halos of old galaxies • Massive star collapse towards the black hole • 100-150 Msun stars • Rotation -> collimation of the ejecta • Young objects in star formation regions • Supernova imprints on late stages of the afterglow

3. Gamma-Ray Bursts:fireball model

4. Naked-Eye Burst SAO RAS, 2009 Gamma-Ray Bursts:what can variability tell? • Activity of central engine • Periods • Flares • Dynamics of ejecta • Internal shocks • Instabilities (density fluctuations, magnetic field reconnections…) • Interaction with surrounding medium • Temporal properties of prompt emission • Stochastic components are distorted (instabilities, interactions, ...)‏ • Periodic components (have to, can, could) reflect internal engine behaviour?

5. Gamma-Ray Bursts:temporal properties – key for the central engine nature Bi-modal distribution of durations ~40% are shorter than 2 seconds About 80% of GRBs light curves are structured The gamma variability timescale is down to ~10-4 s (close to the timescale near horizon events) No periodicity! What about optical prompt emission?

6. Naked-Eye Burst SAO RAS, 2009 Gamma-Ray Bursts:open questions about optical emission When does it start and when does it end? Transition from prompt emission to afterglow several hundreds of afterglows, but only about ten prompts Temporal variability gamma is highly variable down to 10-4 s, what about optics? Relation to gamma emission are they correlated? what is the temporal lag between them? who is the first? Prompt emission from the short bursts afterglows are basically the same, what about prompts? All this require the detection of very first moments of the burst and, obviously, high temporal resolution of observations

7. Naked-Eye Burst SAO RAS, 2009 Gamma-Ray Bursts:time is money GRB Coordinates Network coordinates after ~10 seconds For 50% of events optical prompt emission is lost! Up to now found ~350 afterglows and ~ 20 prompts (~40 upper limits from 8 to 23 mag) ratio of papers - 0.2 RESPONSE TIME OF ALERT-BASED SYSTEMS IS TOO LARGE

8. Naked-Eye Burst SAO RAS, 2009 Independent search for optical prompt emission:requirements for a general-purpose system Need wide field of view the shorter the focus the better Need good detection limit the larger the diameter the better Need high temporal resolution short exposures and fast read-out low read-out noise Need real-time processing software real-time detection and classification of transients

9. Naked-Eye Burst SAO RAS, 2009 Independent search for optical prompt emission :crazy ideas of the past Large telescopes with «bad» mirrors Beskin et al (1999)‏ Size: 10-30 m Detectors: 10-1000 PMT (< 1us)‏ FOV: 10-20 square degrees Angular resolution: 5-30 arcmin Limit: up to 18m for 1ms Cerenkov telescopes (MAGIC, H.E.S.S., VERITAS...)‏ Solar concentrators (PETAL, ...)‏

10. Naked-Eye Burst SAO RAS, 2009 Gamma-Ray Bursts:prompt optical emission You need to look at the burst position before it appears! Systematic monitoring of all sky (or its large parts) with high temporal resolution Selection of parameters – contradictory requirements Wide field of view Large objective diameter High time resolution Optimal parameters: DECISION Field of view > 20o x 20o Small telescopes with large D/F Temporal resolution < 0.1 c and fast detectors Limiting magnitude > 10m

11. Wide-Field Monitoring:systems currently in operation Only general-purpose systems are listed. There are also a lot of specialized (like meteor cameras) or narrow-field (like LINEAR) monitoring projects around the world. Naked-Eye Burst SAO RAS, 2009

12. Naked-Eye Burst SAO RAS, 2009 FAVOR & TORTORA systems:overview FAVOR (FAst Variability Optical Registrator) camera — SAO RAS, since 2003 Built in collaboration with IPI and IKI (Moscow), supported by CRDF grant

13. Naked-Eye Burst SAO RAS, 2009 TORTORA system:overview Telescopio Ottimizzato per la Ricerca dei Transienti Ottici Rapidi Two-telescope complex: - independent detection - automatic study TORTORA La-Silla, Chile mounted on REM since 2006 Team: SAO RAS, IPI (Russia), Bologna University, REM (Italy) TORTORA - Telescopio Ottimizzato per la Ricerca dei Transienti Ottici Rapidi Two-telescope complex: - independent detection - automatic study

14. Naked-Eye Burst SAO RAS, 2009 TORTORA system:technical details Objective Diameter: 120 mm Focal length: 150 mm D/F: 1/1.2 Field of view: 32x24o Image Intensifier type: S20 diameter: 90 mm amplification: 120 downscale: 4.5/1 Q.E.: 10% CCD type: SONY 2/3'' IXL285 size: 1388х1036 exposures: 0.128 — 10 sec scale: 80''/pixel limit: ~10.5m for 0.13с Data flow rate — 20 Mb/s, per night— 600 Gb, ~200.000 frames

15. Naked-Eye Burst SAO RAS, 2009 Wide-field monitoring systems:TORTORA

16. Naked-Eye Burst SAO RAS, 2009 TORTORA – real-time analysis • Decision scheme • Analysis of objects on separate frames • Merging them into events • Automatic classification of events • transient • known astrophysical object • satellite • meteor • Conclusion on event nature in 0.4 s Example of fast optical transient duration– 0.4 s magnitude– 4.6m identification– satellite

17. Naked-Eye Burst SAO RAS, 2009 Wide-field monitoring systems:TORTORA • Two-telescope complex — observations in triggered mode • Bursts outside FOV • Fast REM repointing on GCN alerts • Data acquisition and analysis with high time resolution GRB 060719 Pointing after 59 seconds Limit B > 12.4 with 12.8 s effective exposure Limit for sinusoidal variable component B > 16.5 in 0.01 - 3.5 Hz frequency range GRB 061202 Pointing after 92 seconds Limit B > 11.3 with 12.8 s effective exposure Limit for sinusoidal variable componentB > 14.0 in 0.1 - 3.5 Hz frequency range • GRB 061218 • Pointing after 118 seconds • Limit B > 11.3 with 12.8 s effective exposure • Limit for sinusoidal variable component B > 16.4 in 0.01 - 3.5 Hz frequency range

18. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:the stars – they are falling GRB 080319a: T0 = 05:45:41 UT, T90~40 s, R~21m GRB 080319b: T0 = 06:12:49 UT, T90~60 s, V~5.5m GRB 080319c: T0 = 12:25:55 UT, T90~20 s, R~17m GRB 080319d: T0 = 17:05:19 UT, T90~24 s, V~19m GRB 080320: T0 = 04:37:38 UT, T90~25 s, I' ~23m

19. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:burst in real time

20. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:triumph of monitoring systems

21. Naked-Eye Burst SAO RAS, 2009 Naked-Eye Burst:observations, observations...

22. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:general information – spectrum

23. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:general information — light curve GRB 080319b Swift, Konus-Wind, Integral Eiso = 1.321054 erg, Eopt,iso = 61051 erg z=0.937(VLT/UVES, 8.5 min since burst)‏

24. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:what timing may say Optical observations: - detailed rise and fall - variability (peaks) on seconds - optical/gamma correlation - ??? Starting at T ~ 0 s Rise ~ t 3.5 Fall ~ t -5 Variability: - 2 parts (2 x ~20 s) with intensity ratio of 1.6 - 4 peaks (3-7 s)

25. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:periodicity T = 9.40.8 s, SL=10-15

26. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:periodicity Four nearly equidistant peaks T1-2 = 8.7  0.4 s T2-3 = 9.0  0.3 s T3-4 = 8.2  0.5 s Periodic behaviour of central engine? Kocevski et al (2003)

27. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:power spectra

28. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:short time scales Signs of a periodicity at last peak (40-50 s). A~10%, T~1.14 SL= 0.01 T = 1.140.06 s A<15% A<10% Precession of central engine / jet ???

29. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:optical vs gamma Corr=0.82, SL=5*10-7 Optical and gamma plateau are correlated!

30. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:what theorists think about Two-component jet (Racusin et al 2008)‏ Explains optical/x-ray late afterglow Can't say anything about prompt emission and variability Synchrotron-Self Compton model (Kumar & Panaitescu 2008)‏ Explains optical to gamma excess No optical lag, or negative one Overproduces GeV photons Cannonball model (Dado, Dar & De Rujula 2008)‏ The same as SSC model No predicted supernova bump one month since the burst Optical and gamma emissions from internal forward-reverse shocks (Yu, Wang & Dai 2008)‏ Optics and gamma from the same region, simultaneous emission No optical lag

31. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:residual collisions at large radii Optical emission from residual collisions at large radii (Li & Waxman 2008)‏ Optical lag of ~1 s imply residual collisions radius of 1016 cm Optical emission is of the same nature as gamma-ray one Optics and gamma have the same modulation due to internal engine Г +/- dГ Optical emission Gamma emission A f t e r g l o w Internal engine (single activity episode)‏ modulated ejection of shells Initial collisions R ~ 1013 cm Residual collisions R~1016 cm

32. Naked-Eye Burst SAO RAS, 2009 -rays Naked Eye Burst:neutron-rich internal shocks Proton shell Proton shell Proton shell Proton shell Proton shell Proton shell Proton shell Proton shell Secondary internal shocks at ~1016 cm – result of collisions of late proton shells with products of the early neutron beta-deckay: powering UV/optical emission Regular internal shocks at ~1013 cm: powering gamma-ray emission The beta-decay radius : Natural explanation of fluxes ratio (opt-gamma) ~ 1000

33. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:insights from variability Periodic activity of internal engine — accretion instability modulating the outflow? One second period — signature of precession?

34. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:instability + precession Toy model Newly born black hole M ~ 3 Msun Massive accretion disk Mdisk ~ Msun Neutrino-driven viscous instability Rstop ~ 30 Rg Masada et al, 2007 Viscous Instability T ~ 5 sec Gravitomagnetic Prcession T ~ 0.5 sec

35. Naked-Eye Burst SAO RAS, 2009 Naked Eye Burst:Summary First GRB to be seen completely simultaneously in optical/gamma Two scales of optical variability Periodicity of ~10 seconds for overall emission – four peaks One second period on the last peak (40-50 s)‏ Optical/gamma spectral lag of ~2 seconds as evidence of different localizations ( distance ~ 1016 cm ) Rules out inverse compton models of gamma emission Spectral lags and optical/gamma correlation (r~0.82) imply the same origin of emission variability– periodic activity of central engine

36. Naked-Eye Burst See you in nine years! Naked-Eye Burst SAO RAS, 2009