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The signature of a wind reverse shock in GRB’s Afterglows

The signature of a wind reverse shock in GRB’s Afterglows. Asaf Pe’er Ralph A.M.J. Wijers (Amsterdam). ApJ., 543, 1036 astro-ph/0511508. J une 0 6. Outline. Motivation: massive stars as GRB progenitors Complexities of the ambient density profile

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The signature of a wind reverse shock in GRB’s Afterglows

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  1. The signature of a wind reverse shock in GRB’s Afterglows Asaf Pe’er Ralph A.M.J. Wijers (Amsterdam) ApJ., 543, 1036 astro-ph/0511508 June 06

  2. Outline • Motivation: massive stars as GRB progenitors • Complexities of the ambient density profile • Interaction of relativistic blast wave and wind termination shock • Plasma dynamics • Resulting light curves

  3. Motivation: wind from massive star • Massive stars are progenitors of Long GRB’s(GRB-SN Ic connection, GRB’s in star forming regions..) • Massive stars emit supersonic wind: ISM nISM~103 cm-3 Stellar wind Shocked stellar wind Massive star (reverse) shock wave (forward) shock wave Contact discontinuity

  4. Graph #1: Density profile Pb>>Pa rb=4ra(r=R0) Castor et. al., 1975 Weaver et. al., 1977

  5. Density profilenumerical simulation by Chevalier, Li & Fransson (2004)

  6. Blast wave propagation in region a: density profile Dr(ã)ob. ~ r/4G2 Blandford & McKee (1976) : n(r) r-2G(r) r-1/2

  7. GRB blast wave propagation in region a Regionã: (relativistically-) shocked stellar wind (hot: Gmc2 per particle) Region a: Stellar wind (cold) Region b: Shocked stellar wind G(r) Compressed: Dr(ã)ob. ~ r/4G2 Relativistic blast wave Wind reverse shock

  8. G(r) ~ ~ Region b Region c G1G(r=R0) GRS<G1 Interaction of shock waves Regionã Region a Region b Wind reverse shock (downstream) r<R0 G(r) Regionã: Region b (upstream) r>R0 New blast wave reverse shock New blast wave forward shock Contact discontinuity

  9. Region b: Regionã: ~ ~ Region b Region c GRS<G1=? G2=? G1G(r=R0) Calculation of plasma properties during interaction Problem: reverse shock propagates into hot medium not strong ! We know: Boundary conditions: G1, nã, nb We find: Reverse shock jump conditions: - Conservation of particle number flux: [nGb] - Energy flux – [wG2b] - Momentum flux: [wG2b2 + P]

  10. Schematic density profile during the existence of the reverse shock • As long as the reverse shock exists – plasma in region ã is upstream  continues to move at G1 conditions in other regions are time independent !

  11. Graph #2: Evolution of blast wave Lorentz factor G(r) r-1/2 G(r) r-3/2 R1 = 1.06R0 = radius where the reverse shock crossed region ã

  12. Light curves calculations Synchrotron emission spectrum Calculation in 3 different regimes:(a) r < R0 Emission from region ã (b) R0<r<R1 Emission from regions ã , b, c (c) r>R1  Emission from region c ~ ~ (Sari, Piran & Narayan, 1998) ~

  13. Graph #3: Resultinglight curve Model predictions: (1) Jump in the light curve by a factor ~2 after ~day; (2) Change of spectral slopes at late times (3) Late times afterglow looks like explosion into constant density

  14. Comparison with data: GRB030329 R-band afterglow of GRB030329 (corrected for the contribution of SN2003dh) (Taken from Lipkin et.al., 2004)

  15. Summary • Wind of massive star results in complex density structure • GRB blast wave splits at R0, change its r- dependence • Light curve is complex: shows jump by a factor of ~2 after ~ day, and change slope at late times

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