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Spectral features: broken power laws with E p of a few tens to hundreds of keV

Studies of Gamma-Ray Bursts in the Swift Era Dai Zigao Department of Astronomy, Nanjing University 物理年会，北京， 09/16/2006. Gamma-Ray Bursts. Spectral features: broken power laws with E p of a few tens to hundreds of keV. Temporal features: diverse and spiky light curves.

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Spectral features: broken power laws with E p of a few tens to hundreds of keV

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  1. Studies of Gamma-Ray Bursts in the Swift EraDai ZigaoDepartment of Astronomy, Nanjing University物理年会，北京，09/16/2006

  2. Gamma-Ray Bursts Spectral features: broken power laws with Ep of a few tens to hundreds of keV Temporal features: diverse and spiky light curves.

  3. Bimodal distribution in durations short long 2s

  4. Outline • Pre-Swift progress • Recent progress and implications • GRB cosmology

  5. Most important discoveries in the pre-Swift era • 1967: Klebesadel et al.’s discovery • 1992: spatial distribution (BATSE) • 1997: observations on multiwavelength afterglows of GRB970228 and detection of the redshift of GRB970508 (BeppoSAX) • 1998: association of GRB980425 with SN1998bw(BeppoSAX) • 2003: association of GRB030329with SN2003dh(HETE-2)

  6. Some important discoveries in the pre-Swift era • 1993: sub-classes (Kouveliotou et al.) • 1994: MeV-GeV emission from GRB 940217 (Hurley et al.)；200 MeV emission from GRB 941017 (Gonzalez et al. 2003) • 1997: detection of the iron lines in the X-ray afterglow of GRB 970508 (Piro et al.) • 1999: optical flash and broken ligh curve of the R-band afterglow of GRB 990123 (Akerlof et al.; Fruchter et al.; Kulkarni et al.) • 2002: X-ray flashes (Heise et al.; Kippen et al.) • 2005: X-ray flares of GRBs (Piro et al.)

  7. Theoretical progress in the pre-Swift era • 1975: Usov & Chibison proposed GRBs at cosmological distances; Ruderman discussed an optical depth >> 1 problem • 1986: Paczynski & Goodman proposed the fireball model of cosmological GRBs • 1989: Eichleret al. proposed the NS-NS merger model • 1990: Shemi & Piran proposed the relativistic fireball model to solve the optical depth problem • 1992: Rees & Meszaros proposed the external shock model of GRBs; Usovand Duncan & Thompson proposed the magnetar model • 1993: Woosley proposed the collapsar model • 1994: Paczynski & Xu and Rees & Meszaros proposed the internal shock model of GRBs; Katz predicted afterglows from GRBs • 1995: Sari & Piran analyzed the dynamics of forward-reverse shocks； Waxman和Vietri discussed high-E cosmic rays from GRBs • 1997: Waxman & Bahcall discussed high-E neutrinos from GRBs

  8. 1997: Meszaros & Rees predicted light curves of afterglows • 1998: Sari,Piran & Narayanestablished standard afterglow model; Vietri & Stella proposed the supranova model; Paczynskiproposed the hypernova model; Dai & Luand Rees & Meszarosproposed energy injection models; Dai & Lu and Meszaros et al. proposed the wind model; Wei & Lu discussed the IC scattering in afterglows； • 1999: Rhoadsand Sari et al. proposed the jet model; Sari & Piran explained the optical flash from GRB 990123; Dai & Luproposed dense environments —— GMC； Huang et al. established the generic dynamic model; MacFadyen et al. numerically simulated the collapsar model;Derishev et al. proposed the neutron effect in afterglows • 2000: some correlations were found, e.g., Fenimore et al. and Norris et al. ；Kumar & Panaitescuproposed the curvature effect in afterglows

  9. 2001: Frailet al. found a cluster of the jet-collimated energies; Panaitescu & Kumar fitted the afterglow data and obtained the model parameters • 2002: the Amati correlation was found; Zhang & Meszaros analyzed spectral break models of GRBs; Rossi et al. and Zhang & Meszaros discussed the structured jet models; Fanet al. found the magnetized reverse shock in GRB 990123 • 2003: Schaeferdiscussed the cosmological use of GRBs; • 2004: the Ghirlanda correlation was found; Dai et al.used this relation to constrain the cosmological parameters

  10. Central engine models • NS-NS merger model (Paczynski 1986; Eichler et al. 1989) • Collapsar models (Woosley 1993; Paczynski 1998; MacFadyen & Woosley 1999) • Magnetar model (Usov 1992; Duncan & Thompson 1992) • NS-SS phase transition models (Cheng & Dai 1996; Dai & Lu 1998a; Paczynski & Haensel 2005) • Supranovamodels (Vietri & Stella 1998)

  11. NS-NS merger model Collapsar model

  12. Expectationsto Swift Gehrels et al. 2004, ApJ, 611, 1005 • GRB progenitors? • Early afterglows? • Short-GRB afterglows? • Environments? • Classes of GRBs? • (High-z) GRBs as astrophysical tools? Blast wave interaction?

  13. Gehrels et al. 2004; Launch on 20 November 2004

  14. Discoveries in the Swift era • Prompt optical-IR emission and very early optical afterglows • Early steep decay and shallow decay of X-ray afterglows • X-ray flares from long/short bursts • One high-redshift (z=6.295) burst • Afterglows and host galaxies of short bursts • Nearby GRB060218 / SN2006aj; nearby GRB060614 (z=0.125) / no supernova

  15. Prompt optical-IR emission and • very early optical afterglows Vestrand et al. 2005, Nature, 435, 178 Blake et al. 2005, Nature, 435, 181

  16. 2. Early steep decay and shallow decay of X-ray afterglows GRB 050319 t -5.5ν-1.60.22 t -1.14ν-0.800.08 t -0.54ν-0.690.06 Cusumano et al. 2005, astro-ph/0509689

  17. Tagliaferri et al. 2005, Nature, 436, 985 (also see Chincarini et al. 2005) Initial steep decay: tail emission from relativistic shocked ejecta, e.g. curvature effect (Kumar & Panaitescu 2000; Zhang et al. 2006) Flattening: continuous energy injection (Dai & Lu 1998a,b; Dai 2004; Zhang & Meszaros 2001; Zhang et al. 2006; Nousek et al. 2006), implying long-lasting central engine Final steepening: forward shock emission

  18. 3. X-ray flares from long bursts Burrows et al. 2005, Science, 309, 1833 Explanation: late internal shocks (Fan & Wei 2005; Zhang et al. 2006; Wu, Dai et al. 2005), implying long-lasting central engine.

  19. Energy source models of X-ray flares • Fragmentation of a stellar core (King et al. 2005) • Fragmentation of an accretion disk (Perna Armitage & Zhang 2005) • Magnetic-driven barrier in an accretion disk (Proga & Zhang 2006) • Newborn millisecond pulsar (for short GRB) (Dai, Wang, Wu & Zhang 2006)

  20. 4. High-z GRB 050904: z=6.295 Tagliaferri et al. 2005, astro-ph/0509766

  21. Kawai et al. 2006, Nature, 440, 184

  22. X-ray flares of GRB 050904 Watson et al. 2005, Cusumano et al. 2006, Nature, 440, 164

  23. Zou, Dai & Xu 2006, ApJ, in press

  24. 5. Afterglowfrom short GRB050509B X-ray afterglow Gehrels et al. 2005, Nature, 437, 851

  25. Another case －GRB050709 radio B-band t-1.25 t-2.8 X-ray:t-1.3 Fox et al. 2005, Nature, 437, 845

  26. X-ray flare from GRB050709 射电余辉:上限 X-ray flare at t=100 s 光学余辉: t-1.25 t-2.8 Villasenor et al. 2005, Nature, 437, 855

  27. GRB050724: Barthelmy et al. 2005, Nature, 438, 994

  28. Properties of short GRBs Fox, et al. 2005, Nature, 437, 845

  29. Ages of the host galaxies Gorosabel et al. 2005, astro-ph/0510141

  30. Summary:Basic features of short GRBs 1. low-redshifts (e.g., GRB050724, z=0.258; GRB050813, z=0.722) 2. Eiso ~ 1048 – 1050 ergs； 3. The host galaxies are old and short GRBs are usually in their outskirts;  support the NS-NS merger model！ 4. X-ray flares challenge this model!

  31. Rosswog et al., astro-ph/0306418

  32. Ozel 2006, Nature, in press Support stiff equations of state

  33. Morrison et al. 2004, ApJ, 610, 941

  34. Dai et al. 2006, Science, 311, 1127:differentially-rotating millisecond pulsars, similar to the popular solar flare model.

  35. Further evidence: GRB060313 prompt flares + late flattening Roming et al., astro-ph/0605005, Swift BAT (left), KONUS-Wind (right)

  36. Further evidence: GRB060313 prompt flares + late flattening GRB060313: Roming et al., astro-ph/0605005, Yu Yu’s fitting by the pulsar energy injection model: B~1014 Gauss, P0~1 ms

  37. 6. Nearby GRB 060218/SN2006aj(Campana et al. 17/39, 2006, Nature, in press) • Nearby GRB, z=0.0335 • SN 2006aj association • Low luminosity ~1047 ergs/s, low energy ~1049 ergs • Long duration (~900 s in gamma-rays, ~2600 s in X-rays) • A thermal component identified in early X-rays and late UV/optical band

  38. GRB 060218: prompt emission(Dai, Zhang & Liang 2006) • Very faint prompt UVOT emission can not be synchrotron emission. • The thermal X-ray component provides a seed photon source for IC. • Steep decay following both gamma-rays and X-rays implies the curvature effect. • Non-thermal spectrum must be produced above the photosphere.

  39. GRB 060218: prompt emission(Dai, Zhang & Liang 2006)

  40. Outline • Pre-Swift progress • Recent progress and implications • GRB cosmology

  41. Type-Ia Supernovae When the mass of an accreting white dwarf increases to the Chandrasekhar limit, this star explodes as an SN Ia. Hamuy et al. (1993, 1995)

  42. Supernova Cosmology Luminosity distance of a standard candle DL(z) = [Lp/(4F)]1/2 • More standardized candles from low-zSNe Ia: • A tight correlation: Lp ~ Δm15 (Phillips 1993) • Multi-color light curve shape (Riess et al. 1995) • The stretch method (Perlmutter et al. 1999) • The Bayesian adapted template match (BATM) method (Tonry et al. 2003) • A tight correlation: Lp ~ ΔC12 (B-V colors after the B maximum, Wang X.F. et al. 2005) Phillips (1993)

  43. Integral Method for Theoretical DL or Calculate 2 (H0,ΩM,Ω) or 2 (H0,ΩM, w), which is model-dependent, and obtain confidence contours from 1σto 3σ.

  44. Riess et al. (2004, ApJ, 607, 665):16 SNe Ia discovered byHST.

  45. The deceleration factor:q(z) = q0 + z(dq/dz) Transition from deceleration to acceleration:zT = -q0/(dq/dz) = 0.46

  46. Riess et al. (2004):Ω= 0.71, q0 < 0 (3σ), andw = -1.02+0.13-0.19 (1σ), implying that Λis a candidate of dark energy.

  47. y(z)=H0dL/(1+z) Differential Method, which is model-independent Daly et al. 2004, ApJ, 612, 652 Pseudo-SNAP SNIa sample

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