1. 1 John Nousek (Penn State University) ly Searching the Sky: The First Three Years of the Swift Gamma-Ray Burst Explorer III Cosmic Ray & Astrophysics School - Arequipa, Peru – 1 Sep 2008

2. 2  GRBs – Pre-Swift  GRB Phenomenon  Pre-Swift GRB Paradigm  Swift Era  Swift satellite  Swift discoveries  Challenges to the GRB Paradigm  Short GRBs  ‘Canonical’ X-ray light curves  Lack of jet breaks/chromatic jet breaks  X-ray ‘flares’  Swift & GRB science in the future  What to do with Swift for the next four years? Talk Outline

3. 3 GRBs – Pre-Swift What did we know about GRBs before Swift?

4. 4 GRBs discovered in 1969 by Ray Klebesadel of LANL –Vela satellites: monitored Nuclear Test Ban treaty –Data published in 1973 History of GRBs – BATSE: 2609 bursts in 8.5 years Compton Gamma-Ray Observatory launched on 5 April 1991

5. Compton Observatory Era Soft Hard Hardness Ratio Duration (s) short long

6. GRB 971214 - Keck GRB 970228 - BeppoSAX Beppo-SAX & HETE-2 Era Fireball Model (Meszaros & Rees 1997)  -rays afterglow

7. 7 The Time Gap Swift Beppo SAX data

8. GRB Progenitors Hypernova Merging Neutron Stars

9. 9 The Swift Era What have we learned so far from Swift?

10. 10 Swift launch: 20 Nov 2004 !!

11. 11 MOC Facility Has continuously operated Swift successfully from L+80 minutes to now! Located in State College, PA ~ 4 km. from Penn State campus Flight Operations Team (FOT) – responsible for observatory Health & Safety Science Operations Team (SOT) - responsible for scientific operation of Swift

12. 12 Observing Scenario 2. Spacecraft autonomously slews to GRB position in 20-70 s 3. X-Ray Telescope determines position to ~2-3 arcseconds 4. UV/Optical Telescope images field, transmits finding chart to ground BAT Burst Image T<20 sec 1. Burst Alert Telescope triggers on GRB, calculates position on sky to ~ 1 arcmin BAT Error Circle XRT Image T<90 secT<300 sec UVOT Image

13. 13 BAT GRB Position Accuracy GRB 050215b GRB 050315 GRB 050319 GRB 050406 GRB 050416aGRB 050509a BAT FSW (3’ radius) XRT Mean BAT position error: 52 arcseconds T. Sakamoto

14. 14 FRED Fast Rise Exponential Decay Short GRB Swift Statistics: ~300 GRB discovered 85% with X-ray detections 95% with XRT @ T<200 ks ~60% with optical detection (UVOT + ground) ~9% short GRBs >400 non-GRB TOOs >100,000 slews

15. 15 Average Redshift - Pre-Swift: z = 1.2 - Swift: z = 2.3 Redshift and Time Distributions Redshift (z) Number of GRBs 5 10 Pre-Swift 0.11.0 10.0 0 Swift Long GRBs Lookback Time (G yr) 1.010.0 Era of GRBs 0 5 10 15 20 Analysis by Neil Gehrels

16. 16 72 Swift Long GRB Redshifts 6.29 050904 5.47060927 5.3050814 5.11060522 4.9060510B 4.41060223A 4.27050505 4.05060206 3.97050730 3.91060210 3.71060605 3.69060906 3.63070721B 3.53060115 3.44061110B 3.43060707 3.36061222B 3.34050908 3.24050319 3.22060526 3.20060926 3.08060607A 2.95070411 2.90050401 2.82050603 2.71060714 2.69071031 2.68060604 2.61050820A 2.50070529 2.45070802 2.43060908 2.35051109A 2.35070110 2.31070506 2.30060124 2.20050922C 2.17070810 2.15071020 2.04070611 1.95050315 1.56050801 1.55051111 1.55070125 1.51060502A 1.50070306 1.49060418 1.44050318 1.31061121 1.29050126 1.26061007 1.17070208 1.16061126 0.98071010 0.97070419A 0.95071010B 0.94051016B 0.84060814 0.84070318 0.83050824 0.78060202 0.76061110A 0.70060904B 0.65050416A 0.61050525A 0.59050223 0.54060729 0.44060512 0.30050826 0.125060614 0.089060505 0.033060218 = 2.3 0.001 0.01 0.1110 Redshift Swift Redshift Distribution Number Gehrels et al. 2007

17. 17 GRBs – now in the Swift era How has the paradigm changed with the Swift discoveries?

18. 18 Short vs Long GRBs Short Long GRB 990123 - BeppoSAX HST Image BAT XRT GRB 050509B - Swift VLT Image Cnts/s Short GRBLong GRB Cnts/s Short GRBs in non-SF galaxies/regions Long GRBs in SF galaxies GRB Swift first to discover counterpart to short GRB!

19. 19 III Cosmic Ray & Astrophysics School – Arequipa, Peru – 1 Sep 2008 Comparing Short and Long GRBs & GRB 061210 GRB 061121 = brightest long GRB GRB 061210 = brightest short GRB Norris et al. 2006

20. 20 III Cosmic Ray & Astrophysics School – Arequipa, Peru – 1 Sep 2008 Comparing Short and Long GRBs & GRB 061210 GRB 061121 = brightest long GRB GRB 061210 = brightest short GRB Short GRB 051221A Kouveliotou et al. 1993

21. 21 Long GRBs Short GRBs Gehrels et al. 2007 Prompt vs Afterglow Correlation Analysis

22. 22 Short GRBs - Opportunity Progress on short GRBs - a tough nut to crack! Swift statistics: 24 total short GRB (+ 3 questionable) * ~4 firm redshifts * 8 OTs * ~4 host galaxy IDs Short bursts versus Long bursts - Different physics - Different environments - Different population of stars - Different ages & distances New tool for studying stellar evolution & binary formation Direct tie-in to emerging GW field CHALLENGE: Short GRBs are weak in , X, opt Current knowledge from few events GRBs with afterglow - special subclass? Which are short, which are long? Needed: more short GRBs rapid, sensitive follow-up high resolution optical imaging

23. 23 Pre-Swift X-ray light curve Swift Beppo SAX data

24. Canonical Swift XRT Light Curve (steep – due to light delay effects from end of prompt emission) (plateau – due to energy injection into external shock) (normal – external shock) Flare Jet Break GRB060428A – Courtesy of D. Burrows

25. 25 Jet Break Torus Jet Relativistic beaming: θ ~ Γ -1 Frail et al. 2001, ApJ, 562, L55

26. 26 Jet Break Frail et al. 2001, ApJ, 562, L55 Jet break knowledge is critical for GRB energetics: E γ = E iso (1-cos θ j )

27. GRB050416A > 58 Days α = 0.81 GRB060729 is also still going with no jet break after 2 months!

28. 28 Jet Break Torus Jet Relativistic beaming: θ ~ Γ -1 Frail et al. 2001, ApJ, 562, L55 For some Swift bursts there is either no jet break, or there is a chromatic break → Either jet angle is very wide or Density is very low or Basic model is wrong

29. 29 Giant X-ray Flare: GRB 060526 > 100x increase! Peak ~ 220 s

30. 30 Giant X-ray Flare: GRB 050502B 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 Peak ~ 700 s Note establishment of AG before flare begins.

31. 31 Swift XRT X-ray Flares GRB 050406 GRB 050421 GRB 050502B GRB 050712 GRB 050607GRB 050713A GRB 050714B GRB 050716 GRB 050726 GRB 050730 116 prompt afterglow detections ~ 50% have X-ray flares Typically in first 20 min. Dynamic range: 1.3x – 500x Flare analysis courtesy of Dave Burrows

32. 32 Flares in Short GRBs ? Mechanism for flares must also operate in the context of short GRBs.

33. 33 The Future What to do with Swift for the next four years?

34. 34 High-z GRB - Opportunity Prediction: - 7% - 10% of Swift GRBs at z>5 (Bromm & Loeb, Jakobbson et al., Lamb & Reichart) - ~0.5% at z>10 Swift measurements: - 4 out of 72 = 6% Bromm & Loeb (2006) Swift GRB Rate z GRB Optical Brightness 6.29 050904 J = 18 @ 3 hrs 5.6060927 I = 16 @ 2 min 5.3050814 K = 18 @ 23 hrs 5.11060522 R = 21 @ 1.5 hrs

35. 35 High-z GRB - Opportunity GRBs are briefly the most luminous sources in the universe.... across the E-M spectrum! High-z GRBs offer unique tool for studying: - Reionization era - Abundance history of universe - First stars & first light - Star formation rate history - Gas and dust content of early galaxies CHALLENGE: Difficult to determine redshift for high-z bursts Bursts not detected in optical can be common dark GRBs or rare high-z events. Needed: rapid response, large telescope, IR spectrograph Needed: redshift indicators, good position on sky for follow-up Fraction with OT Fraction with z 239 Swift GRBs with XRT 20052006 2007

36. GRB 060218: GRB + Supernova Super-long GRB - ~35 minutes BAT, XRT, UVOT during GRB z = 0.033 d = 145 Mpc SN 2006aj SN Ib/c E iso = few x 10 49 erg - underluminous E peak = 4.9 keV - XRF BAT 3 GRB SNe SN 2006aj SNe Ic Campana et al., Mazzali et al., Pian et al., Soderberg et al. Pian et al. 2006

37. 37 Underluminous GRBs - Opportunity Observations of nearby GRBs leading to breakthroughs in understanding of: - GRB central engine - Jet outflows - CC supernovae CHALLENGE: Data are scarce and puzzling: 6 events, all different - 980425 underluminous - 031203 underluminous - 030329 normal GRB - 060219 XRF underluminous - 060505 no SN - 060614 no SN Needed: better detection of faint GRBs

38. 38 The Year of High-z Bursts Alerts from Swift data - BAT T90, variability, spectrum (Ukwatta & Sakamoto 2007) - X-ray light curve flaring (Morris et al. 2007) - X-ray N H correlations (Grupe et al. 2007) - UVOT photometric data (Vanden Berk 2007) Sun Angle - 50% of time with Swift pointing >9hr from sun Follow-up Community - Small & medium telescopes to identify candidates - Large telescope for spectra of likely candidates

39. Sakamoto 2007 Pointing angle relative to Sun Advantage of high sun angle 2006 April 2007 Nov. 2007 9 hr 3 hr Sun Angle 1.0 Number of GRBs Fraction of GRBs with z All GRBs Sun angle [deg]

40. 40 BAT Low Threshold Experiment Lower BAT thresholds: ~2 triggers & slews per day Observe with NFIs for 2 ks Trigger is deemed a GRB if afterglow is detected No Notices or Circulars for triggers without afterglow Observers can sign up to receive all triggers, with suitable warnings Experiment to last 1 month Barthelmy, Palmer, Fenimore

41. 41 Opportunities for Joint Observations JWST (2013) IR ICECUBE (2009 -2011) neutrinos LIGO (2014 - ALIGO) gravitational wave ~30 NS-NS mergers per year ALMA (2012) radio mm/submm IR Afterglow JWST sensitivity Bromm & Loeb (2007) z=15 z=5 AGILE & GLAST H.E.  -rays Dermer, Chiang & Mitman (2000) H.E.  -Ray

42. 42 GSFC Swift Institutions Executive Committee G. Chincarini - Brera Obs. N. Gehrels - GSFC P. Giommi - ASI K. Mason - MSSL J. Nousek - PSU J. Osborne - U. Leicester A. Wells - U. Leicester N. White - GSFC