1 / 36

伽玛暴的能源、成分和偏振 戴子高 南京大学天文与空间科学学院 POLAR 启动会 , 2014 年 3 月 22 日

伽玛暴的能源、成分和偏振 戴子高 南京大学天文与空间科学学院 POLAR 启动会 , 2014 年 3 月 22 日. v ≥ 0.9999c. Open questions. Central engines of long/short GRBs: BHs, NSs, QSs? Composition of jets: baryons, leptons, magnetic fields?

lydie
Download Presentation

伽玛暴的能源、成分和偏振 戴子高 南京大学天文与空间科学学院 POLAR 启动会 , 2014 年 3 月 22 日

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 伽玛暴的能源、成分和偏振戴子高南京大学天文与空间科学学院POLAR启动会, 2014年3月22日

  2. v ≥ 0.9999c

  3. Open questions • Central engines of long/short GRBs: BHs, NSs, QSs? • Composition of jets: baryons, leptons, magnetic fields? • Physics (e.g. energy dissipation mechanisms, radiation regions & mechanisms) of prompt emission? • Physics of early afterglows (plateaus & X-ray flares)? • Short GRBs/GWs/other signals? GRB130603B/kilonova • High-energy gamma-rays, CRs & neutrinos? • Higher-redshift bursts/Pop III stars? • GRB cosmology (e.g. cosmological models, star formation rates, cosmic reionization)? • GRBs and other frontier physics? • Iron lines?

  4. Open questions • Central engines of long/short GRBs: BHs, NSs, QSs? • Composition of jets: baryons, leptons, magnetic fields? • Physics (e.g. energy dissipation mechanisms, radiation regions & mechanisms) of prompt emission? • Physics of early afterglows (plateaus & X-ray flares)? • Short GRBs/GWs/other signals? GRB130603B/kilonova • High-energy gamma-rays, CRs & neutrinos? • Higher-redshift bursts/Pop III stars? • GRB cosmology (e.g. cosmological models, star formation rates, cosmic reionization)? • GRBs and other frontier physics? • Iron lines 第1、2、3、4个问题与偏振有关！

  5. 已有的光学偏振观测 Liverpool Telescope GRB120308A Mundell et al. (2013, Nature, 504, 119) 意义：喷流包含重子和大尺度磁场

  6. 光学偏振在Nature/Science上已经发表4篇论文！

  7. Π=80±20%?

  8. Requirements to central enginesalso see Dai & Lu (1998, PRL, 81, 4301) • Observed fluence and redshift →extremely high luminosity and energy: Liso~1047-1054 erg s-1 and Eiso~1049-1055 ergs. • Variable light curves in general Δtvar~0.01 s (Δtmin~0.1 ms) →multi-explosions at typical Tdur~ tens of seconds. • Observed power-law spectrum and GeV photons → Lorentz factor ≥100→ very low baryon contamination. • Observed jet break and extremely high Eiso→jet. • Detection rate → burst rate ~10-5-10-6/galaxy/year. • X-ray flares and shallow decay of afterglows in ~ one half of Swift-detected GRBs→long-lasting activity.

  9. Three types of central engines 1) Black hole + accretion disk systems (collapsars or mergers, Eichler et al. 1989; Woosley 1993; Narayan et al. 2001; MacFadyen et al. 2001): Gravitational energy of the disk → thermal energy → neutrino-cooling-dominated disk, Lwind due to neutrino annihilation is too low? Spin energy of the BH → Blandford-Znajek mechanism: LBZ~3*1050B152(MBH/3Msun)2a2f(a) erg s-1 for a~1, MBH~ 3Msun and B~1015 Gauss.

  10. 2)Millisecond magnetars (collapsars or mergers) Gravitational energy of an accretion disk → thermal energy → neutrino-cooling-dominated disk: much higher Lwind (Zhang & Dai 2008, 2009, 2010, ApJ) Rotational energy (Usov 1992; Duncan & Thompson 1992; Metzger et al. 2011) Differentially-rotational energy (Kluzniak & Ruderman 1998; Dai & Lu 1998; Dai et al. 2006)

  11. 3) Strange quark stars (collapsars or mergers or X-ray binaries): Mcrust≤10-5Msun → very low baryon contamination Phase-transition energy ~3*1052 erg (Cheng & Dai 1996) Rotational energy and differentially-rotational energy ~3*1052 erg (Dai & Lu 1998) Gravitational energy of an accretion disk: feed-back effect (Hao & Dai 2013) *Millisecond magnetars → shallow decay of early afterglows (Dai & Lu 1998; Zhang & Meszaros 2001; Dai 2004)

  12. I. Plateaus in early X-ray afterglows GRB050319 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)

  13. See Liang et al. (2007) for a detailed analysis of Swift GRBs: ~ one half of the detected GRB afterglows.

  14. Following the Poynting-flux energy-injection model of a pulsar (Dai & Lu 1998), numerical simulations by some groups (e.g., Fan & Xu 2006; Dall’Osso et al. 2011) provided fits to shallow decay of some GRB afterglows with different slopes.

  15. Relativistic wind bubble (RWB) Ambient gas (zone 1) Shocked ambient gas (zone 2) Shocked wind (zone 3) A relativistic e-e+ wind (zone 4) External shock (ES) Black hole Termination shock (TS) Contact discontinuity Dai (2004, ApJ)

  16. Dai (2004) Yu & Dai (2007)

  17. as discussed in Dai (2004). Future possible detections by POLAR

  18. “Spin evolution of millisecond magnetars with hyperaccreting fallback disks: implications for early afterglows” (Dai & Liu 2012, ApJ, 759, 58) RL R0≈Rm magnetospheric radius Rc: corotation radius RL: light cylinder

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

  20. Chincarini et al. (2007, ApJ, 671, 1903): ~ one half of the detected GRB afterglows.

  21. Short GRB050724: Barthelmy et al. 2005, Nature, 438, 994

  22. tacc ~ 0.5 s Rosswog et al. (2003)

  23. Obs. I. Demorest et al. (2010, Nature, 467, 1081): using Shapiro delay B1957+20 Van Kerkwijk et al. (2010): PSR B1957+20, MPSR = 2.40±0.12M⊙ Obs. II. Support stiff nuclear equations of state

  24. Kluzniak & Ruderman (1998) Lazzati (2007) Dai, Wang, Wu & Zhang (2006, Science, 311, 1127)

  25. Statistics of X-ray flares • Motivation: solar flares are triggered by a magnetic reconnection process, while X-ray flares may also be driven by a similar process (e.g. Dai et al. 2006). Question: do they have statistical similarities? • Wang Fayin & Dai (2013, Nature Physics, 9, 465) find statistical similarities between X-ray flares and solar flares: power-law frequency distributions for energies, durations, and waiting times. • These similarities suggest that X-ray flares may also be triggered by a magnetic reconnection process.

  26. Left: differential energy distribution of solar flares Right: cumulative energy distribution of X-ray flares The slopes: (-1.65±0.02, -1.06±0.15)

  27. Differential duration time distributions of solar flares and X-ray flares. The slopes: (-2.00±0.05, -1.10±0.15).

  28. Differential waiting time distributions of solar flares and X-ray flares. The slopes: (-2.04±0.03, -1.80±0.20).

  29. 耀发能量、持续时间和等待时间的相似分布揭示相同的磁重联机制（Wang, Dai & Yi 2014, submitted to ApJS）。

  30. Explanation • Self-organized criticality (SOC): subsystems will self-organize to a critical state at which a small perturbation can trigger an avalanche of any size within the system (Bak et al. 1997). • The slopes of frequency distributions for energies and durations depends on the Euclidean dimensions S (Aschwanden 2012): • S ≈ 1 for X-ray flares, and S ≈ 3 for solar flares.

  31. III. NS-NS mergers, GWs, and EM signals Macronova Dai et al. 2006; Gao & Fan 2006; Fan & Xu 2006; Zhang 2013; Gao, Ding, Wu, Zhang & Dai 2013; Fan et al. 2013; Yu et al. 2013; Wang & Dai 2013; Wu et al. 2014

  32. Rowlinson et al. (2013): SGRB magnetar sample assuming ηx=1

  33. Reverse shock emission from a postmerger ms magnetar: fitting Palomar Transient Factory PTF11agg (Wang LJ & Dai 2013; Wu et al. 2014)

  34. Models on polarization Nonthermal emission: - synchrotron - (inverse-) Compton large-scale B and syn: Π=(p+1)/(p+7/3)~70% Shock accelerated electrons (p=2) Waxman, 2003, Nature, 423, 388

  35. Summary and Implications • GRBs with plateaus and flares in early X-ray afterglows originate from millisecond magnetars, whose jets are magnetic-or-leptonic-dominated. • These GRBs and possible others have high polarization. • Detections of polarization by POLAR would reveal the central engine, composition, and structure of a GRB jet. • We will carry out numerical simulations on polarization in different models of central engines, prompt emission, and early afterglows.

More Related