Gamma Ray Burst Boot Camp

1. Gamma Ray BurstBoot Camp Robert Nemiroff Michigan Tech

2. GRB Boot Camp: Abstract Gamma Ray Bursts (GRBs) are the furthest explosions known. As such they are valuable probes of energetic explosions and fluctuating beacons seen through nearly the entire intervening universe. Although almost every physical mechanism behind GRBs is debated, leading theories will be reviewed including expansion physics and candidate progenitor objects. The phenomenology of GRBs will be reviewed including prompt emission, afterglows, common light curve features, and candidate standard candles. Searches for GRB coincidences with detectors sensitive to neutrinos, gravitational radiation, cosmic rays, and extremely high energy photons will be reviewed. Searches for gravitational lensing by intervening dark matter and Lorentz invariance violations by intervening quantum foam will be reviewed. Relevant parts of the lecturer's own research will also be briefly mentioned.

3. Know Your Lecturer (Highlights) The consistency of cosmology and BATSE number versus brightness relation • Wickramasinghe, Nemiroff, et al. 1993, Astrophys. J. 411, L55 Gross spectral differences between bright and dim GRBs • Nemiroff, Norris, et al. 1994, Astrophys. J. 435, L133 Detection of signature consistent with cosmological time dilation in GRBs • Norris, Nemiroff et al. 1994, Astrophys. J. 424, 540 The 75th Anniversary Astronomical Debate on the Distance Scale to GRBs • Nemiroff 1995, Pub. Astron. Soc. Pacific 107, 1131 The Pulse Scale Conjecture and the Case of BATSE Trigger 2193 • Nemiroff 2000, Astrophys. J. 544, 805 Limits on cosmological supermassive objects from millilensingsearch in GRBs • Nemiroff, Marani et al. 2001, Phys. Rev. Lett 86, 580 Possible impact of GRB detector thresholds on cosmological standard candles • Shahmoradi, Nemiroff, 2011, Mon. Not. Roy. Astron. Soc. 411, 1843 Bounds on Spectral Dispersion from Fermi-Detected GRBs • Nemiroff, Connolly et al., 2012, Phys. Rev. Lett 108, 1103

4. GRBs: Suggested readings • Wikipedia: http://en.wikipedia.org/wiki/Gamma_ray_bursts • Short: Astronomy Outline • http://astronomyonline.org/cosmology/grbs.asp • Medium: Unveiling the Secrets of GRBs, Gomboc, A 2012 • http://arxiv.org/abs/1206.3127 • Long: The Physics of Gamma-Ray Bursts, Piran, T. 2004, • http://arxiv.org/abs/astro-ph/0405503

5. GRBs: Why Study GRBs? To better understand … • Star and galaxy evolution in universe • Nature of the intervening universe • Physics of the expanding fireballs • Physics of the prompt explosion

6. GRBs: Outline • Phenomenology • Prompt emission • Afterglows • Coincident emission searches • Physical Mechanisms • Candidate progenitor objects • Physics of expansion • Probes of the Universe • Star formation history • Cosmological expansion history • Dark matter & quantum foam

7. GRBs: Outline • Phenomenology • Prompt emission • Afterglows • Coincident emission searches • Physical Mechanisms • Candidate progenitor objects • Physics of expansion • Probes of the Universe • Star formation history • Cosmological expansion history • Dark matter & quantum foam

8. GRBs: Prompt emission • GRBs are triggered in the hard X-ray and soft γ-ray • Triggering emission episode called “prompt emission” • ~5% of GRBs have a “precursor” up to tens of seconds earlier • Why are GRBs not triggered in optical light? • Background is too high • Occasional “orphan afterglow” • Why are GRBs not triggered in hard γ-rays? • Signal is too low • Prompt optical and soft X-ray sometimes also detected

9. GRBs: Present Missions • Swift, Fermi, AGILE, INTEGRAL • Tens of ground-based counterpart chasers • Find and track optical, IR, radio counterpart • Find redshift • InterPlanetary Network (IPN) • Solar system scattered satellites with small detectors • Time delays yield high precision locations • Current IPN members: • Earth (Many: e.g. Fermi, Swift) • Mercury (MESSENGER) • Mars (Odyssey) • L1 (Konus-WIND)

10. GRBs: Unpredictable Flashes • What is seen: • Variability: • Isotropy: science.hq.nasa.gov

11. GRBs: The Long and the Short • Plot of time separation: Bimodal Norris, J. P., Stanford talk

12. GRBs: Visible in other ways? • Neutrinos • Ice Cube, etc. • Gravitational radiation • LIGO, etc. • Very High Energy Gamma Rays • Milagro, HAWC, etc. • Visible light • “orphan afterglows”, LSST, etc.

13. GRBs: History • USA looking to verify nuclear test ban (in space) • 1960s • Ian Strong: “If it scintillates, fly it!” • First model: Stirling Colgate (predates first GRB detection) • First astronomer consulted: Vera Rubin • Cosmology vs. Galactic debate • Paczynski vs. Lamb 1995 • 75th anniversary of the Shapley – Curtis debate • Same location!

14. GRBs: Outline • Phenomenology • Prompt emission • Afterglows • Coincident emission searches • Physical Mechanisms • Candidate progenitor objects • Physics of expansion • Probes of the Universe • Star formation history • Cosmological expansion history • Dark matter & quantum foam

15. GRBs: Outline • Phenomenology • Prompt emission • Afterglows • Coincident emission searches • Physical Mechanisms • Candidate progenitor objects • Physics of expansion • Probes of the Universe • Star formation history • Cosmological expansion history • Dark matter & quantum foam

16. GRBs: Progenitor Models • Create your own GRB model • Show off your physics prowess! • Be cited by your friends! • But how? • Take your current field of research • Find a scenario that can generate great bursts of energy • Find a way for it to create gamma rays • Or not! • Kludge with unknown progenitor rates • Publish! • Hundreds of GRBs models have been published

17. GRB: Progenitor Models Nemiroff, R. J. 1994, Comments Astrophys.

18. Leading Long GRBProgenitor Model Core collapse supernova • Wolf-Rayetstar (M > 50ish Msun) • Iron core • Seen as Type Ic • Furthest redshift ~9 • Leaves a black hole (unconfirmed) Host Galaxies • Blue, high star formation • Low metalicity Image: Y. Grosdidier (U. Montreal) et al., WFPC2, HST, NASA

19. GRBs: Connection to Supernovae • Long GRBs • GRB 980425 = SN 1998bw • GRB 030329 = SN 2003dh • Many others suspected Image: S. Holland, J. Hjorth, J. Fynbo (Survey of Host Galaxies of GRBs Team), ESA, NASA

20. Leading Short GRB Progenitor Model Colliding neutron stars • Less numerous than LGRBs • Not seen coincident with supernova (as yet) • Furthest redshift ~ 1 Host Galaxies • High diversity of types Illustration: Dana Berry, NASA

21. GRBs: Physics of Expansion • Many mechanisms hotly debated • Key problems • How to liberate so much energy • How to efficiently convert kinetic energy to photons • Expansion speeds must be relativistic • Or optically thick gamma-rays create primarily e-e+ pairs • Synchrotron radiation • Charged particles deflected by B fields emitting photons • Inverse Compton scattering • Charged particles up-scattering photons

22. GRBs: After the central engine • Beamed shocks: Internal: prompt; External: afterglow Image: Piran, T., Nature 422, 268-269 (20 March 2003)

23. GRBs: Expanding Shocks • Fireball Expansion phases & the “jet break” Image: Nakar & Piran, New Astronomy, 8, 2, 2003, Pages 141–153

24. GRBs: Outline • Phenomenology • Prompt emission • Afterglows • Coincident emission searches • Physical Mechanisms • Candidate progenitor objects • Physics of expansion • Probes of the Universe • Star formation history • Cosmological expansion history • Dark matter & quantum foam

25. GRBs: Outline • Phenomenology • Prompt emission • Afterglows • Coincident emission searches • Physical Mechanisms • Candidate progenitor objects • Physics of expansion • Probes of the Universe • Star formation history • Cosmological expansion history • Dark matter & quantum foam

26. GRBs: Probe of Star Formation History • Direct information on stars in early universe • Unique! • Must originate from SOME type of star • How early did massive stars form? (back to z=9 at least) • Properties of host galaxies – where do GRB stars reside?

27. GRBs: Star formation probe Jimenez, R. & Piran, T. 2013, arXiv:1303.4809

28. GRBs: Cosmological Expansion History Candidate Standard Clocks • Duration (e.g.: T90) • Minimum fluctuation time Candidate Standard Candles • Peak flux, Fluence • Lag (between energies) • Variability • Epeak: ”Amati Relation” • Constraints = weak • GRB sample, detection threshold effects, need more nearby GRBs • (e.g.: Mörtsell & Sollerman1005, JCAP)

29. GRBs: Cosmological Expansion History Schaefer, B. 2007, Astrophys. J.

30. GRBs: Probe of Massive Dark Matter Nemiroff et al. 2001, Phys. Rev. Lett

31. GRBs: Probe of Quantum Foam (Possibly significant signal well below lPlanck) Nemiroff et al., 2014, research in progress

32. Very Preliminary: Might interest Sabine (Signal below lPlanck unlikely) Nemiroff et al., 2014, research in progress

33. GRBs: Destroyers of Life • Instant media attention! • Should Earthlings fear future bright GRBs? • Needs to be within ~3000 light years for affect • Observed brightness distribution extrapolated to extremely bright • Nearby GRB affects Earth every 5M years? 100M? • Long GRBs too metal poor to occur in our Milky Way galaxy? • Ordovician–Silurian extinction event 450M years ago (?) • What would happen? • Depends on distance to explosion • Secondary radiation • Ozone depletion • Smog winter

34. GRBs: Missions • Past: Vela(s), CGRO (BATSE), BeppoSAX • Current: Swift, Fermi, AGILE, INTEGRAL • Future: Space-based Variable Object Monitor (SVOM) • France & China, Launch in 2015 (?) • See: http://arxiv.org/abs/1005.5008 • Possible Future: • Lobster, Pharos, Edge, LOFT, UFFO Pathfinder

35. Gehrels, N. et al., Lobster presentation, GSFC, 2012

36. GRBs: Breaking News Sources • AAS email list-server • GCN Circulars • Best for latest news • Web page and email list-server • http://gcn.gsfc.nasa.gov/gcn3_archive.html • arXiv.org • astro-ph.HE

37. GRBs: My Research • GRBs consistent with cosmology • Time dilation • Spectral offsets • Lensing searches with GRBs • Limiting cosmological dark matter • Modeling pulses of GRBs • Searching for cosmological dispersion in GRBs • Sometimes called “Lorentz Invariance violations” • Sometimes called “Spacetime foam effects”

38. Surprise: Philosophy Slide! Why study astronomy? • Defense: better bombs, lasers, detectors • Engineering: more underlying physics: better mousetraps • Entertainment: philosophical why, where, and how • Of Life & the Universe