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Collaborators

Recent Progress on Gamma-Ray Bursts and GRB Cosmology Zigao Dai Department of Astronomy, Nanjing University Sino-French workshop, Beijing, 08/30/2006. Collaborators. Lu Tan, Huang Yongfeng, Wang Xiangyu, Wei Daming, Cheng Kwongsheng

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Collaborators

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  1. Recent Progress on Gamma-Ray Bursts and GRB CosmologyZigao DaiDepartment of Astronomy, Nanjing UniversitySino-French workshop, Beijing, 08/30/2006

  2. Collaborators • Lu Tan, Huang Yongfeng, Wang Xiangyu, Wei Daming, Cheng Kwongsheng • Li Zhuo, Wu Xuefeng, Fan Yizhong, Zou Yuanchuan, Shao Lang, Xu Dong, Xu Lei, … • Zhang Bing, Liang Enwei, Peter Meszaros

  3. 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.

  4. Bimodal distribution in durations short long 2s

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

  6. 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)

  7. 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.)

  8. 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

  9. 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

  10. 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

  11. 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)

  12. NS-NS merger model Collapsar model

  13. Summary: fireball + shock model

  14. Basic assumptions in the standard afterglow model • A spherical,ultrarelativistic fireball is ejected; • The total energy of the shocks is released impulsively before their formation; • The unshocked medium is homogeneous, and its density is of the order of 1 cm-3; • The electron and magnetic energy-density fractions of the shocked medium and the index p of the electron power-law distribution are constant; • The emission mechanism is synchrotron radiation.

  15. Physical effects in afterglows • Jets(Rhoads 1997, 1999; Sari, Piran & Halpern 1999; Dai & Cheng 2001) • Postburst energy injection(Dai & Lu 1998a, 2000, 2001; Rees & Meszaros 1998; Panaitescu & Meszaros 1998; Kumar & Piran 2000a,b; Zhang & Meszaros 2001a,b; Nakar & Piran 2003; Dai 2004) • Environments including stellar windsand dense media(Dai & Lu 1998b, 1999, 2002; Meszaros, Rees & Wijers 1998; Chevalier & Li 1999, 2000; Dai & Wu 2003; Chevalier et al. 2004) • Model parameters changed(Yost et al. 2003) • Other emission mechanisms including IC scattering(Wei & Lu 1998; Sari & Esin 2001; Panaitescu & Kumar 2001; Zhang & Meszaros 2002)

  16. 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?

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

  18. ν~(5-18)x1014 Hz

  19. 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

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

  21. Further evidence: Vestrand et al. 2006, Nature, in press

  22. 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

  23. 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

  24. 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.

  25. Halpern et al. (2006): optical flares

  26. Energy source models of X-ray/optical 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)

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

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

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

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

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

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

  33. 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

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

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

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

  37. 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!

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

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

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

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

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

  43. 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

  44. 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 see J.S. Deng’s talk

  45. 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.

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

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

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