Ambient Interaction Models for γ-Ray Burst Afterglows

Li, Zhi-Yun; Chevalier, Roger A.

doi:10.1007/3-540-45863-8_20

Cited by 4 publications

(2 citation statements)

References 109 publications

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“…The term À 0 is the initial Lorentz factor of the fireball. Similarly, the size of the spherical fireball can be expressed in the ISM and wind media as (Sari et al 1998;Li & Chevalier 2003) R(ISM ) ¼ 1:3 ; 10 17 E 52 n Using the emission radius derived from scintillation studies (R 2:4 ; 10 17 cm), we find an opening angle of 0:25 rad (14 ) for the ISM model and 0:23 rad (13 ) for the wind model. The Lorentz factor of the shocked ejecta at the time of the jet break is (t jet ) ffi 1/ ¼ 4 in the ISM model and 5 in the wind model.…”

Section: Energeticsmentioning

confidence: 91%

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A Comprehensive Study of GRB 070125, A Most Energetic Gamma‐Ray Burst

Chandra

Cenko

Frail

et al. 2008

Astrophysical Journal

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We present a comprehensive multiwavelength analysis of the bright, long-duration gamma-ray burst GRB 070125, comprised of observations in gamma-ray, X-ray, optical, millimeter, and centimeter wave bands. Simultaneous fits to the optical and X-ray light curves favor a break on day 3.78, which we interpret as the jet break from a collimated outflow. Independent fits to optical and X-ray bands give similar results in the optical bands but shift the jet break to around day 10 in the X-ray light curve. We show that for the physical parameters derived for GRB 070125, inverse Compton scattering effects are important throughout the afterglow evolution. While inverse Compton scattering does not affect radio and optical bands, it may be a promising candidate to delay the jet break in the X-ray band. Radio light curves show rapid flux variations, which are interpreted as due to interstellar scintillation and used to derive an upper limit of 2:4 ; 10 17 cm on the radius of the fireball in the lateral expansion phase of the jet. Radio light curves and spectra suggest a high synchrotron self-absorption frequency indicative of the afterglow shock wave moving in a dense medium. Our broadband modeling favors a constant density profile for the circumburst medium over a windlike profile (R À2). However, keeping in mind the uncertainty of the parameters, it is difficult to unambiguously distinguish between the two density profiles. Our broadband fits suggest that GRB 070125 is a burst with high radiative efficiency (>60%).

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Section: Energeticsmentioning

confidence: 91%

“…cm À1 ) medium ( Wu et al 2005 and references therein). The collimation angle for a radiative afterglow can be written as (Sari et al 1998;Frail et al 2001;Li & Chevalier 2003)…”

Section: Energeticsmentioning

confidence: 99%

A Comprehensive Study of GRB 070125, A Most Energetic Gamma‐Ray Burst

Chandra

Cenko

Frail

et al. 2008

Astrophysical Journal

Self Cite

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The X‐Ray and Radio Emission from SN 2002ap: The Importance of Compton Scattering

Björnsson

Fransson

2004

ApJ

113

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The radio and X-ray observations of the Type Ic supernova SN 2002ap are modeled. We find that inverse Compton cooling by photospheric photons explains the observed steep radio spectrum, and also the X-ray flux observed by XMM. Thermal emission from the shock is insufficient to explain the X-ray flux. The radio emitting region expands with a velocity of ∼ 70, 000 km s −1 . From the ratio of X-ray to radio emission we find that the energy densities of magnetic fields and relativistic electrons are close to equipartion. The mass loss rate of the progenitor star depends on the absolute value of ǫ B , and is given byṀ ≈ 1 × 10 −8 (v w /1000 km s −1 )ǫ −1 B M ⊙ yr −1 .

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GRB 071003: Broadband Follow‐up Observations of a Very Bright Gamma‐Ray Burst in a Galactic Halo

Perley

Chornock

et al. 2008

Astrophysical Journal

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The optical afterglow of long-duration GRB 071003 is among the brightest yet to be detected from any GRB, with R ≈ 12 mag in KAIT observations starting 42 s after the GRB trigger, including filtered detections during prompt emission. However, our high S/N ratio afterglow spectrum displays only extremely weak absorption lines at what we argue is the host redshift of z = 1.60435 -in contrast to the three other, much stronger Mg II absorption systems observed at lower redshifts. Together with Keck adaptive optics observations which fail to reveal a host galaxy coincident with the burst position, our observations suggest a halo progenitor and offer a cautionary tale about the use of Mg II for GRB redshift determination. We present early through late-time observations spanning the electromagnetic spectrum, constrain the connection between the prompt emission and early variations in the light curve (we observe no correlation), and discuss possible origins for an unusual, marked rebrightening that occurs a few hours after the burst: likely either a late-time refreshed shock or a wide-angle secondary jet. Analysis of the late-time afterglow is most consistent with a wind environment, suggesting a massive star progenitor. Together with GRB 070125, this may indicate that a small but significant portion of star formation in the early universe occurred far outside what we consider a normal galactic disk.

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Ambient Interaction Models for γ-Ray Burst Afterglows

Cited by 4 publications

References 109 publications

A Comprehensive Study of GRB 070125, A Most Energetic Gamma‐Ray Burst

A Comprehensive Study of GRB 070125, A Most Energetic Gamma‐Ray Burst

The X‐Ray and Radio Emission from SN 2002ap: The Importance of Compton Scattering

GRB 071003: Broadband Follow‐up Observations of a Very Bright Gamma‐Ray Burst in a Galactic Halo

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