1. Swift Observations of GRBs David Burrows The Pennsylvania State University

2. 2008 Nanjing GRB Conference GRBs and Swift 20 November 2004

3. 2008 Nanjing GRB Conference Burst Alert Telescope (BAT) Burst Alert Telescope (BAT) –15-150 keV –2 sr field of view –CdZnTe detectors –Most sensitive gamma-ray imager ever –Detect ~100 GRBs per year X-Ray Telescope (XRT) X-Ray Telescope (XRT) –0.2-10 keV –Few arcsecond positions –CCD spectroscopy UV/Optical Telescope (UVOT) UV/Optical Telescope (UVOT) –170 – 650 nm –Sub-arcsec positions –Grism spectroscopy –6 UV/optical broad-band filters –22 nd mag sensitivity (filtered) Spacecraft Spacecraft –Autonomous re-pointing, 20 - 75 sec –Onboard and ground triggers BAT XRT Spacecraft UVOT BAT UVOT XRT Swift Instruments

4. 2008 Nanjing GRB Conference Swift GRBs (> 330 so far) Short GRB FRED Fast Rise Exponential Decay 88% followed up with XRT/UVOT observations

5. 2008 Nanjing GRB Conference Beppo-SAX afterglows: de Pasquale et al. 2006, AA, 455, 813 GRB 000529 GRB 000615 GRB 000926GRB 001109 GRB 010214GRB 010222 GRB 990806 GRB 991106 GRB 000214 2e41e6

6. 2008 Nanjing GRB Conference Swift X-ray Afterglows ~ 225 Prompt X-ray LCs GRB 060204BGRB 060211AGRB 060306 GRB 060413GRB 060428AGRB 060502A GRB 060510A GRB 060510BGRB 060729 1e21e6

7. 2008 Nanjing GRB Conference Afterglow Statistics LGRBs: Detected 253/262 = 97% with XRT (observed @ T < 200 ks) Compare with 55 LGRB afterglows before Swift launch Handful of long GRBs not detected by XRT SGRBs: Detected ~23/31 = 74% with XRT (observed @ T < 200 ks) Compare with 0 SGRB afterglows before Swift launch XRT: All Swift GRBs: Detected 276/293 = 94% with XRT (observed @ T < 200 ks) > 80% of the X-ray afterglows ever detected! ~90% have prompt slews (< 300 s, excluding Aug-Oct 2007) Optical: UVOT: ~ 40% detection rate Total optical: ~ 60% detection rate, ~ 33% with redshifts

8. 2008 Nanjing GRB Conference Key Swift Discoveries GRBs GRBs –> 240 GRBs with arcsec positions –~ 100 GRBs with redshifts (>70% of world total) –80% of world X-ray afterglows Complex X-ray lightcurves and flares – see O’Brien and Chincarini talks this PM Complex X-ray lightcurves and flares – see O’Brien and Chincarini talks this PM

9. 2008 Nanjing GRB Conference 1 year! t j ~ 400 d θ j ~ 67° !! E γ ~ 3 x 10 51 erg GRB 060729 at z=0.54 (Grupe et al. 2008) Key Swift Discoveries GRBs GRBs –> 240 GRBs with arcsec positions –~ 100 GRBs with redshifts –80% of world X-ray afterglows Complex X-ray lightcurves and flares Complex X-ray lightcurves and flares Jet breaks (or not…) Jet breaks (or not…)

10. 2008 Nanjing GRB Conference Key Swift Discoveries GRBs GRBs –> 240 GRBs with arcsec positions –~ 100 GRBs with redshifts –80% of world X-ray afterglows Complex X-ray lightcurves and flares Complex X-ray lightcurves and flares Jet breaks (or not…) Jet breaks (or not…) –“Naked-eye GRB”: GRB 080319B (see session on Tuesday PM) GRB 080319B (Racusin et al. 2008)

11. 2008 Nanjing GRB Conference GRB 060218 (Campana et al. 2006) Key Swift Discoveries GRBs GRBs –> 240 GRBs with arcsec positions –~ 100 GRBs with redshifts –80% of world X-ray afterglows Complex X-ray lightcurves and flares Complex X-ray lightcurves and flares Jet breaks (or not…) Jet breaks (or not…) –“Naked-eye GRB”: GRB 080319B –First shock breakout from stellar surface: GRB 060218 / SN2006aj

12. 2008 Nanjing GRB Conference GRB 071227 (D’Avanzo et al. 2007) VLT Key Swift Discoveries GRBs GRBs –> 240 GRBs with arcsec positions –~ 100 GRBs with redshifts –80% of world X-ray afterglows Complex X-ray lightcurves and flares Complex X-ray lightcurves and flares Jet breaks (or not…) Jet breaks (or not…) –“Naked-eye GRB”: GRB 080319B –First shock breakout from stellar surface: GRB 060218 / SN2006aj –Short GRBs with large and small redshifts Arcsecond localizations => evidence for compact mergers Arcsecond localizations => evidence for compact mergers New data hints at subclasses in redshift, offset, and progenitors New data hints at subclasses in redshift, offset, and progenitors

13. 2008 Nanjing GRB Conference GRB 060614 at z=0.125 (Gal-Yam et al. 2006) Key Swift Discoveries GRBs GRBs –> 240 GRBs with arcsec positions –~ 100 GRBs with redshifts –80% of world X-ray afterglows Complex X-ray lightcurves and flares Complex X-ray lightcurves and flares Jet breaks (or not…) Jet breaks (or not…) –“Naked-eye GRB”: GRB 080319B –First shock breakout from stellar surface: GRB 060218 / SN2006aj –Short GRBs with large and small redshifts Arcsecond localizations => evidence for compact mergers Arcsecond localizations => evidence for compact mergers New data hints at subclasses in redshift, offset, and progenitors New data hints at subclasses in redshift, offset, and progenitors –Nearby long GRBs with and without SNe Possible new classes of GRBs Possible new classes of GRBs

14. 2008 Nanjing GRB Conference Key Swift Discoveries GRBs GRBs –> 240 GRBs with arcsec positions –~ 100 GRBs with redshifts –80% of world X-ray afterglows Complex X-ray lightcurves and flares Complex X-ray lightcurves and flares Jet breaks (or not…) Jet breaks (or not…) –“Naked-eye GRB”: GRB 080319B –First shock breakout from stellar surface: GRB 060218 / SN2006aj –Short GRBs with large and small redshifts Arcsecond localizations => evidence for compact mergers Arcsecond localizations => evidence for compact mergers New data hints at subclasses in redshift, offset, and progenitors New data hints at subclasses in redshift, offset, and progenitors –Nearby long GRBs with and without SNe Possible new classes of GRBs Possible new classes of GRBs –Metallicities of star forming regions in galaxies to record high redshift (z=6.3) using GRBs Includes transitions never before seen Includes transitions never before seen GRB 050730 at z=3.97 (Chen et al. 2005)

15. 2008 Nanjing GRB Conference Short GRBs Major discovery of Swift is the first localizations of short GRBs, and the discovery that they occur in different environments than long GRBs Major discovery of Swift is the first localizations of short GRBs, and the discovery that they occur in different environments than long GRBs Consistent with origin from different progenitors (merging compact objects rather than collapsar) Consistent with origin from different progenitors (merging compact objects rather than collapsar)

16. 2008 Nanjing GRB Conference GRB Classification Bimodal distribution of durations - Short, hard GRBs: mergers - Long, soft GRBs: collapsars Short Bursts: mergers Old (few billion yrs) Outside galaxies Long Bursts: collapsars Young (few million yrs) Star-forming regions

17. 2008 Nanjing GRB Conference GRB Classification Horvath et al. 2002, AA, 392, 791 Short/hard Long/soft Donaghy et al. 2006, astro-ph/0605570 E. Nakar, 2006

18. 2008 Nanjing GRB Conference ~35 Short GRBs (33 from Swift BAT)

19. 2008 Nanjing GRB Conference GRB 050509B t 90 = 0.04 s, Fluence = 2E-8 ergs/cm 2 XRT counterpart in first 400 s, fades rapidly. 11 photons total. Location in cluster at z=0.226, near early- type galaxy. Possible NS-NS merger? BAT: t -1.3 XRT: t -1.1 XRT error circle on VLT image. XRT position is 9.8” from a bright elliptical galaxy at z=0.226 Chandra 100x-1000x fainter than typical AG Gehrels et al. 2005, Nature

20. 2008 Nanjing GRB Conference GRB050709: Second Short GRB Afterglow Discovered by the HETE-II satellite X-ray counterpart found by Chandra X-ray Observatory Optical counterpart found by ground-based telescopes Located at edge of star-forming galaxy at z=0.16 Danish 1.54m La Silla telescope (Jensen et al. 2005, GCN 3589; Price et al. 2005, GCN 3612) Fox et al. 2005

21. 2008 Nanjing GRB Conference GRB 050724 WHT Wiersema et al. 2005, GCN 3699 Optical transient located on edge of an early-type galaxy at z=0.257, L=1.7L*, SFR < 0.02 M o /yr. Another old, nearby elliptical galaxy associated with a short GRB!! t 90 = 1 s by BATSE definition. (But long soft tail.) 30x brighter than GRB 050509B.

22. 2008 Nanjing GRB Conference GRB 050724 No evidence of jet break, θ j > 0.5 rad for reasonable jet parameters t -0.8 Late-time bump (~1/2 day) Grupe et al. 2006

23. 2008 Nanjing GRB Conference ~30 photons t -2.05 GRB 050813

24. 2008 Nanjing GRB Conference Possible association with elliptical galaxies in cluster at z~ 0.722 (or 1.8 – Berger) GRB 050813

25. 2008 Nanjing GRB Conference Swift Short GRBs without afterglows GRB 050906: t 90 = 0.13 s XRT observations began at T+79 s No X-ray counterpart – very unusual GRB 050925 (short, soft) t 90 = 0.07 s XRT observations began at T+92 s No X-ray counterpart – very unusual GRB 051105A t 90 = 0.03 s XRT observations began at T+68 s No X-ray counterpart – very unusual GRB 051114 t 90 = 2.2 s XRT observations began at T+126 ks No X-ray counterpart

26. 2008 Nanjing GRB Conference GRB 051210 t -2.57 flare No clear optical counterpart or redshift, but near z=0.114 cluster Mangano et al. 2006 Naked GRB

27. 2008 Nanjing GRB Conference Soderberg et al. 2006GRB051221A

28. 2008 Nanjing GRB Conference z=0.5459 E p = 402 keV E iso = 2.4E51 Clear jet break implies θ j ~ 4-8˚ Similar to long bursts GRB 051221A t -1.20 Burrows et al. 2006 t -1.93 t -1.20 GRB051221A

29. 2008 Nanjing GRB ConferenceGRB051227 z=0.714 ?? E p = 100 keV t -1.13

30. 2008 Nanjing GRB Conference Many small flares Energy injection t -1.49 GRB 060313

31. 2008 Nanjing GRB Conference Many small flares in early X-ray light curve. Interpret as variable circum-burst medium, with cooling frequency dropping through X-ray band during orbital gap. Small flares in later optical light curve. Roming et al., ApJ, 651, 985 GRB 060313

32. 2008 Nanjing GRB Conference Short GRBs (through 2006) GRBTail? t 90 (s) t followup Afterglow Redshift - 1 GRB 050509B 0.04 53 s X0.225 Possible host galaxy / cluster 2 GRB 050709 Y0.22 139 ks X, O 0.161 Optical afterglow 3 GRB 050724 Y3.0 74 s X, O, R 0.258 Optical afterglow 4 GRB 050813 0.6 73 s X 0.7? / 1.8? Possible host galaxies 5 GRB 050906 0.13 79 s Marginal X ? 6 GRB 050925 0.07 92 s None? 7 GRB 051105A 0.03 68 s None? 8 GRB 051114 2.2 126 ks None? 9 GRB 051210 1.4 79 s X0.114? Possible host galaxy 10 GRB 051211A 4.8 > 11.2 ks None? 11 GRB 051221A 1.4 88 s X, O, R 0.5459 Optical afterglow 12 GRB 051227 Y8 93 s X, O 0.714 Optical afterglow 13 GRB 060121 Y2.4 10.6 ks X, O 4.6?? Possible host galaxy 14 GRB 060313 0.7 94 s X, O ? 15 GRB 060502B 0.09 70 s X? 16? GRB 060505 4 52 ks X, O 0.089? Possible host, SF region? 17? GRB 060614 Y102 91 s X, O 0.125 Optical afterglow, no SN 18 GRB 060801 0.5 63 s X1.131?? Possible host galaxy 19 GRB 061006 Y130 143 s X, O ? 20 GRB 061201 0.8 81 s X, O 0.111 / 0.0865 Possible host galaxy/cluster 21 GRB 061210 Y85 209 ks X0.41? Possible host galaxy 22 GRB 061217 0.3 64 s X0.827? Possible host galaxy

33. 2008 Nanjing GRB Conference Gorosabel et al. 2006, AA, astro-ph/0510141 Short GRB hosts

34. 2008 Nanjing GRB Conference Long vs short GRB energetics 060614 Long GRBs, from Panaitescu 2005) short GRBs long GRBs 10 55 10 54 10 48 10 53 10 52 10 49 10 50 10 51 10 47 10 -2 10 -1 10 0 10 1 10 2 10 3 T 90 / (1+z) (s) E iso (erg) Swift GRBs

35. 2008 Nanjing GRB Conference Fundamental questions on short GRBs What can we hope to learn about short GRBs from X-ray afterglows? What are the progenitors of short GRBs? Are there subclasses of short GRBs? How do short GRB afterglows differ from long GRB afterglows? What can we learn about short GRB environments? What can we learn about the central engines of short GRBs?

36. 2008 Nanjing GRB Conference Short GRB Environments: “normal” decays t -1.15 t -1.22 t -1.13 050509B t -1.07 051227 060121 (HETE-2) 060502B t -1.2 060505 ~ 25% of sample No evidence for decay of prompt emission => consistent with short duration of bursts -exception: 051227, which had a soft tail to the prompt emission Simple afterglows without energy injection phase Afterglows commence by beginning of XRT observations (~ 100 s after burst) BAT XRT

37. 2008 Nanjing GRB Conference Short GRB Environments: “canonical afterglows” t -2.3 t -1..9 060614 061006 061201 t -1.5 t -0.5 t -2.2 t -0.1 t -0.7 t -1.8 t -1.49 060313 t -1.49 050724 t -0.8 t -1.20 t -1.93 051221A t -1.20 ~ 25% of sample Evidence for decay of prompt emission in 3 bursts: 050724, 060614, 061006. - All three of these have soft tails in the BAT data All have evidence for energy injection phases Afterglows commence by beginning of XRT observations (~ 100 s after burst)

38. 2008 Nanjing GRB Conference Short GRB Environments: “Naked” GRBs t -2.05 t -2.57 050813 051210 t -5.8 060801 t -1.2 061210 t -2.3 Combining with the 9 non-detections of short GRBs with prompt slews, we have >13/33 possible “naked” short GRBs, vs 5/210 possible “naked” long GRBs. => Consistent with lower density environments for short GRBs. Short GRBs without X-ray afterglows: 050906, 050925, 051105A, 051114, 070209, 070810B, 070923, 071112B, 080121

39. 2008 Nanjing GRB Conference Short GRB Central Engines: Flares 050724 t -0.8 t -1.13 051227 t -1.49 060313 t -1.49 t -5.8 060801 t -1.2 X-ray flares seen in ~50% of long GRBs Evidence for flaring in ~20% of short GRBs => short GRBs need to keep central engine running for hundreds of seconds

40. 2008 Nanjing GRB Conference Short GRB Central Engines: Energy Injection 050724 t -0.8 t -1.49 060313 t -1.49 t -1.20 t -1.93 051221A t -1.20 060614 t -1.5 t -2.2 t -0.1 t -2.3 061006 t -0.7 t -1.8 t -1..9 061201 t -0.5 t -0.6 061217 Two flavors: Continuous energy injection: shallow decays Episodic energy injection: injection period followed by return to original decay slope

41. 2008 Nanjing GRB Conference Short GRB Summary X-ray afterglows similar to long GRBs, but fainter and less complex X-ray afterglows similar to long GRBs, but fainter and less complex Late central engine activity implied by flares and energy injection in X-ray afterglows Late central engine activity implied by flares and energy injection in X-ray afterglows High incidence of naked GRBs => low density environments High incidence of naked GRBs => low density environments “Missing” hosts “Missing” hosts –Ejections from hosts? –High redshift? Possible subclasses: Possible subclasses: –Extended soft tails –Late central engine activity

42. 2008 Nanjing GRB Conference GRB Classification Horvath et al. 2002, AA, 392, 791 Donaghy et al. 2006 Short/hard Long/soft E. Nakar, 2006 Gehrels et al. 2006 The problem with GRBs is that we have no clear-cut emperical classification scheme: –Considerable overlap in durations and spectral properties between the “long” and “short” populations –Increasing sample of “short/hard” GRBs with long soft tails (~ 33%) 050709, 050724, 051227, 060121, 061006, 061210, 070714B, 080123, 080503 050709, 050724, 051227, 060121, 061006, 061210, 070714B, 080123, 080503 These often have t90 >> 5s as measured by Swift/BAT These often have t90 >> 5s as measured by Swift/BAT

43. 2008 Nanjing GRB Conference Long Soft Tails of Short GRBs Norris & Bonnell 2006, ApJ, 643, 266 Villasenor et al. 2005, Nature, 437, 855 GRB 050709

44. 2008 Nanjing GRB Conference Long Soft Tails of Short GRBs Barthelmy et al. 2005, Nature, 438, 994 GRB 050724 GRB 051227

45. 2008 Nanjing GRB ConferenceGRB060505 Weak burst that did not trigger BAT Ground processing revealed weak source Late notification and slew t 90 = 4 s Optical transient in SF region of spiral galaxy (Sc-type) No associated SN to very low limits Either short GRB (Ofek et al.) or long GRB (Fynbo et al.) Ofek et al.

46. 2008 Nanjing GRB Conference GRB060614 Duration: t 90 = 102s => “long”/Type II Duration: t 90 = 102s => “long”/Type II Initial hard pulse with longer soft tail: similar to several “short”/Type I GRBs (though tail is brighter, harder, and more variable in this case) Initial hard pulse with longer soft tail: similar to several “short”/Type I GRBs (though tail is brighter, harder, and more variable in this case)

47. 2008 Nanjing GRB Conference Mangano et al., A&A, 470, 105 GRB060614

48. 2008 Nanjing GRB Conference Optical: Break at 30 ks slope of 1.1 Second break at 104 ks slope of 2.4 Break at 100 ks seen in both X-ray and optical => achromatic break to slope of about 2.4  Jet break.  θ j = 10.5° (n/3) 1/8 (η/0.2) 1/8  E γ = 4 x 10 49 ergs Mangano et al., A&A, 470, 105 GRB060614

49. 2008 Nanjing GRB Conference BAT+XRT Spectral Fit Fit to Band model gives E p = 8 keV in this time interval. E p ~ 10 keV early, then drops through the X-ray band. Mangano et al., A&A, 470, 105 GRB060614

50. 2008 Nanjing GRB Conference Mangano et al., A&A, 470, 105 UVOT+XRT SED Early: UVOT and XRT inconsistent  Different spectral segments  Cooling frequency must fall near the UV After 30 ks, XRT and UVOT consistent with a single synchrotron spectrum. GRB060614

51. 2008 Nanjing GRB ConferenceGRB060614 Gal-Yam et al., Nature

52. 2008 Nanjing GRB Conference Gehrels et al. 2006, Nature GRB060614

53. 2008 Nanjing GRB Conference Zhang et al. 2007, ApJ, submitted GRB060614

54. 2008 Nanjing GRB Conference The enigmatic case of GRB 060614 The problem with GRBs is that we have no clear-cut emperical classification scheme: –Considerable overlap in durations and spectral properties between the “long” and “short” populations –Increasing sample of “short/hard” GRBs with long soft tails 050709, 050724, 051227, 060121, 061006, 061210 050709, 050724, 051227, 060121, 061006, 061210 These often have t 90 >> 5s as measured by Swift/BAT These often have t 90 >> 5s as measured by Swift/BAT –Case of GRB 060121 (Donaghy et al.) => argument for multidimensional classification, new terminology (“short/long population GRBs”) –Case of GRB 060614 => suggestion for Type I/Type II classification (Zhang et al 2007, ApJ; Zhang 2006, Nature) Duration: t 90 = 102s => “long”/Type II Duration: t 90 = 102s => “long”/Type II Initial hard pulse with longer soft tail: similar to several “short”/Type I GRBs (though tail is brighter and more variable in this case) Initial hard pulse with longer soft tail: similar to several “short”/Type I GRBs (though tail is brighter and more variable in this case) Location: outskirts of host galaxy => “short”/Type I Location: outskirts of host galaxy => “short”/Type I Lack of SN => short/Type I or unusual “long”/Type II Lack of SN => short/Type I or unusual “long”/Type II Lag-luminosity relation: small lag => “short”/Type I Lag-luminosity relation: small lag => “short”/Type I E iso ~ 10 51 ergs, E γ ~ 4 x 10 49 ergs E iso ~ 10 51 ergs, E γ ~ 4 x 10 49 ergs => intermediate between Type I and Type II

55. 2008 Nanjing GRB Conference XRT Afterglow Statistics Mean redshift for long GRBs is ~2.4 Mean redshift for short GRBs is ~0.5 8 GRBs with z > 4.0 (none since 060927)

56. 2008 Nanjing GRB Conference Keck Spectroscopy of GRB 050505 Berger et al. 2005 Metallicity vs Redshift z = 4.275 Damped Ly  - N(HI)=10 22 cm -2 - n ~ 10 2 cm -3 - Z = 0.06 Z O - M progenitor < 25 M O..

57. 2008 Nanjing GRB Conference Subaru spectrum of GRB 050904: z = 6.295 ± 0.002 Kawai et al. 2006 N H =4E21

58. 2008 Nanjing GRB Conference Summary The XRT is performing well. Current efforts are focussing on analysis of database of > 200 afterglows. XRT is increasingly being used for ToOs and other non-GRB science programs.

59. 2008 Nanjing GRB Conference The Future of Swift Selected as #1 mission in the 2008 NASA Senior Review: Selected as #1 mission in the 2008 NASA Senior Review: –In the next 3-4 years we will obtain –more high redshift GRBs –more GRBs with good optical observations, –more short GRBs, and –more unusual cases (like 061007, 060614, 070110, …) Starting subthreshold trigger experiment to search for weak bursts in the noise Starting subthreshold trigger experiment to search for weak bursts in the noise GLAST / Swift synergy GLAST / Swift synergy –GBM: will provide MeV-range spectral data for many Swift GRBs –LAT: will discover very high energy (GeV) GRBs that can be localized by Swift (~ 1 / month) Investigating possibility of rapid Swift responses to LAT GRBs Investigating possibility of rapid Swift responses to LAT GRBs Enhanced LIGO (2009) Enhanced LIGO (2009) –Will double detection range, may permit detection of inspiral sirens Long-term: Advanced LIGO (c. 2013) Long-term: Advanced LIGO (c. 2013) –Simultaneous detection of short GRB by Swift and LIGO would provide “smoking gun” for merger picture –NS-NS inspiral out to 300 Mpc – up to 3/d –NS-BH inspiral to 650 Mpc

60. 2008 Nanjing GRB Conference Long-Term Future Beyond Swift: the high z universe Beyond Swift: the high z universe –Swift may be detecting high z bursts, but ground-based observations are required to identify them –SVOM –JANUS: identify high z GRBs and QSOs Reionization Reionization Star formation at high z Star formation at high z –Xenia: High resolution spectroscopy of GRBs Reionization Reionization First stars First stars Cosmic Structure Cosmic Structure WHIM WHIM

61. 2008 Nanjing GRB Conference JANUS SMEX mission selected for Phase A studies (launch in mid-2012) SMEX mission selected for Phase A studies (launch in mid-2012) X-ray Flash Monitor (0.5-20 keV) + NIR Telescope (0.7-1.7 μ m, R=14) X-ray Flash Monitor (0.5-20 keV) + NIR Telescope (0.7-1.7 μ m, R=14) –Optimized for detection and identification of high-z GRBs –> 50 GRBs with 5 50 GRBs with 5 < z < 12 Star formation rate, finder for ground-based followup Star formation rate, finder for ground-based followup –20,000 sq degree spectroscopic sky survey to discover > 400 QSOs @ 6 400 QSOs @ 6 < z < 10

62. 2008 Nanjing GRB Conference Xenia Instrumentation Instrumentation –Wide Field Monitor (similar to Swift BAT) –Wide Field Imager (similar to Swift XRT, but > 1° x 1°) –Wide Field Spectrometer (microcalorimeter, 0.7° x 0.7°) –GRB Monitor (MeV range)

63. 2008 Nanjing GRB Conference Xenia Xenia

64. 2008 Nanjing GRB Conference Summary Swift has compiled a large database of bursts and their X-ray and optical afterglows, discovering Swift has compiled a large database of bursts and their X-ray and optical afterglows, discovering –Complex X-ray afterglows –X-ray flares, implying long-lived central engine activity –Prompt, accurate localization of short GRBs -> mergers –Bright, high-z bursts Swift has increasingly become the satellite of choice for multiwavelength, rapid-response Targets of Opportunity Swift has increasingly become the satellite of choice for multiwavelength, rapid-response Targets of Opportunity –CVs and novae –SNe –Galactic transients –AGN and blazars Future prospects: Future prospects: –Swift/GLAST synergy –Swift/LIGO synergy -> compact mergers –JANUS, SVOM, and other proposed missions will focus on high-z