1 / 12

Origin of the X-Ray Flashes

Origin of the X-Ray Flashes. 京大天体核　 D3 山崎 了. 共同研究者 : 井岡 邦仁 ( 阪大 ) 、中村 卓史 ( 京大 ). Ref. Yamazaki et al., astro-ph/0401044. X-ray band. γ - ray band. Light Curves of XRFs & GRBs. X-ray flash (XRF). γ-ray burst (GRB). GRB. XRF. Ep=19 keV. Ep=126 keV.

vilina
Download Presentation

Origin of the X-Ray Flashes

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. Origin of the X-Ray Flashes 京大天体核　D3 山崎 了 共同研究者 : 井岡 邦仁(阪大)、中村 卓史(京大) Ref. Yamazaki et al., astro-ph/0401044

  2. X-ray band γ- ray band Light Curves of XRFs & GRBs X-ray flash (XRF) γ-ray burst (GRB)

  3. GRB XRF Ep=19 keV Ep=126 keV Spectral properties of XRFs and GRBs Double power-low form fits spectra of XRFs and GRBs. Photon indices α, β (スペクトルの傾き) は GRB と XRF で同じ。 XRF の Ep (peak energy) は GRB のものよりも小さい。

  4. XRF(X-ray rich GRB) と GRB の 　･ スペクトル以外の性質(duration, event rate 等) 　 は同じ。 　･ 観測量の分布は連続的。　 ⇒ 両者の起源は同一であると考えられている。 GRB X-ray rich GRB XRF (1+z) Ep ∝ Eiso1/2 (for GRBs and XRFs with known redshifts) Rest frame Ep - Eiso relation

  5. Theoretical Models of the X-ray flash • High redshift GRBs (Heise et al. 2001) • External shocks with small Lorentz factors (Dermer et al. 1999; Rossi et al. 2001) • Internal shocks with high Lorentz factors (Mochkovitch et al. 2003) • Photosphere-dominated fireball (Meszaros et al. 2002; Drenkahn 2002) • Jets with wide opening angles (Lamb et al. 2003) • Off-Axis GRBs (Yamazaki et al. 2002, 2003) ’ ’

  6. νFν X-ray band γ-ray band XRFs GRB relativistic beaming effect GRBs XRF jet (γ～100) ν relativistic Doppler effect Ｏff-Axis Jet Model of XRFs The X-ray flashes (and the soft GRBs) are the typical GRBs observed from off-axis viewing angle.

  7. LOS Ep - Eiso relation in off-axis jet model Ep～ ν0δ ν0 : frequencyin the jet-comoving frame δ-1 = γ(1-βcosθ)～[1+ (γθ)2]/(2γ) γ= 100 : Lorentz factor of the jet θ=θｖ- Δθ (<< 1 ) Eiso ∝δ1-α α= -1～-2 : photon index ⇒ Ep ∝ Eiso1/(1-α) 　　　 ～ Eiso1/3～1/2

  8. Line of sight Jet Emission Model (Yamazaki et al. 2003) ・Spontaneous emission from instantaneously thin shell. ・Normalization of emissivity; isotropic γ-ray energy from the source with z = 1 and θｖ= 0 satisfies Eγ= Eiso (Δθ)2 /2= 1×1051 ergs (Bloom et al. 2003) where Eiso = 4πdL2 (1+z)-1 Sγ ( Sγ; obs. fluence ) ・Emission spectrum in the comoving frame

  9. Δθ/γ-1 =10 Δθ/γ-1 = 5 Maximum redshift to be detected by HETE γ = 100 α = -1 β = -2.5 γν’０= 500 keV zmax : maximum redshift Slim(2-400 keV) = 5×10-8 erg/cm2 Viewing angle θV / γ-1

  10. for z=0, θV=0 Input parameters(10,000 events) α β z Δθ

  11. Soft events (<100 keV) are off-axis emissions! 209 on-axis events 79 off-axis events obs. best fit 62 GRBs 192 XRR-GRBs 34 XRFs ＋: detected by HETE (on-axis) × : detected by HETE (off-axis) ･ : not detected by HETE Result of Simulation : Ep – Eiso relation HETE detects 288 events among 10000 simulated bursts.

  12. The Ep-Eiso relation, the Ep-distribution, the hardness distribution etc. depend on the unknown functional form of the opening angle distribution. ⇒ Ep-Eiso relation constrains the jet opening angle distribution, and therefore the ratio of GRBs to core-collapse SNe !!! Summary Off-axis emission from z～1 can be observable. The Ep-Eiso relation may be reproduced by the off-axis jet model : off-axis emission represents large portion of the X-ray flash.

More Related