1. GRB prompt optical/UV emission and dust sublimation
崔晓红
国家天文台 SVOM组 厦门

2. Outline Observation & motivation Dust sublimation
Model application: GRB B
Other bursts & prediction

3. Observation z=0.937 γ- ray: t0 -4 s--t0+57 s
optical: t0 +10 s- t t0 +45
Lp,1~5×1049 erg/s
GRB B, Racusin et al. 2008

4. Dust sublimation τ: effective optical depth
Rcl
Waxman & Draine 2000
τ: effective optical depth
ρ: density of grain material
m: mean atomic mass
B: chemical binding energy per atom
Sublimation rate:
GRB
<Q>T: Plank-averaged absorption efficiency
QUV: absorption efficiency over 1-7.5eV

5. Energy Absorption The grain survival time:
The fraction of the flash energy absorbed by dust
nd: dust number density, determined by a standard dust-to-gas ratio
R c l

6. Parameters from the model
L, tdur, trise, nH
f-r
Rcl (molecular cloud): f_obs=trise/tdur
Rd (Dust destruction radius Rd)

7. GRB B
Increasing nH, Rd and Rcl decrease, but Rcl decrease more rapidly than Rd

8. GRB B
A rectangular pulse is assumed to be the eV emission from the GRB
Lobs~L1-7.5 e-τ
Dust optical depth:
τ= QUVndπa2(Rcl-r)

9. Other bursts & prediction

10. Dark rate nH, tdur, trisefobs (Rcl)
The transition point (Rt,Lt) from observed to dark
Rcl-L
Rd-L
Rcl=Rd
Gauss distribution of L with Lmean and σ