Physical Parameters of GRB 970508 and GRB 971214 from Their Afterglow Synchrotron Emission

Wijers, R. A. M. J.; Galama, T. J.

doi:10.1086/307705

Cited by 450 publications

(588 citation statements)

References 35 publications

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“…Such a break would require a concave upward inÑection at longer wavelengths, which is not accommodated by any afterglow model. A similar peak was seen in the IR photometry of GRB 971214 (Ramaprakash et al 1998), but it too could not be satisfactorily explained (Wijers & Galama 1999) in a manner consistent with all of the other data on that burst. In the case of GRB 991216 additional IR data that do not show such a peak have been reported by Garnavich et al (2000).…”

Section: Broadband Continuum Shape and Reddeningmentioning

confidence: 63%

GRB 991216 Joins the Jet Set: Discovery and Monitoring of Its Optical Afterglow

Halpern

Uglesich

Mirabal

et al. 2000

ApJ

112

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The optical light curve of the energetic c-ray burst GRB 991216 is consistent with jetlike behavior in which a power-law decay steepens from t~1.22B0.04 at early times to t~1.53B0.05 in a gradual transition at around 2 days. The derivation of the late-time decay slope takes into account the constant contribution of a host or intervening galaxy, which was measured 110 days after the event at R \ 24.56^0.14, although the light curve deviates from a single power law whether or not a constant term is included. The early-time spectral energy distribution of the afterglow can be described as or F l P l~0.74B0.05 Ñatter between optical and X-ray, which, together with the slow initial decay, is characteristic of standard adiabatic evolution in a uniformly dense medium. Assuming that a reported absorption-line redshift of 1.02 is correct, the apparent isotropic energy of 6.7 ] 1053 ergs is reduced by a factor of B200 in the jet model, and the initial half-opening angle is B6¡. GRB 991216 is the third good example of a jetlike afterglow (following GRB 990123 and GRB 990510), supporting a trend in which the apparently most energetic c-ray events have the narrowest collimation and a uniform interstellar medium environment. This, plus the absence of evidence for supernovae associated with jetlike afterglows, suggests that these events may originate from a progenitor in which angular momentum plays an important role but a massive stellar envelope or wind does not, e.g., in the coalescence of a compact binary.

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Section: Broadband Continuum Shape and Reddeningmentioning

confidence: 63%

GRB 991216 Joins the Jet Set: Discovery and Monitoring of Its Optical Afterglow

Halpern

Uglesich

Mirabal

et al. 2000

ApJ

112

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“…Here we present the time-resolved spectroscopy. Our polarimetric observations resulted in the Ðrst polarization detection of a GRB afterglow (Wijers et al 1999 ; see also Covino et al 1999), while our photometric observations show an achromatic break in the BV RIJHK light curves, which is most likely due to the burst emission being collimated (E. Rol et al 2000, in preparation ; see also Stanek et al 1999 ;Harrison et al 1999). Fruchter et al (1999) 1.2.…”

Section: Introductionmentioning

confidence: 61%

VLT Spectroscopy of GRB 990510 and GRB 990712: Probing the Faint and Bright Ends of the Gamma‐Ray Burst Host Galaxy Population

Vreeswijk

Fruchter

Kaper

et al. 2001

ApJ

Self Cite

108

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We present time-resolved optical spectroscopy of the afterglows of the gamma-ray bursts GRB 990510 and GRB 990712. Through the identiÐcation of several absorption lines in the Ðrst-epoch GRB 990510 spectrum, we determine the redshift for this burst at z º 1.619. No clear emission lines are detected. The strength of the Mg I feature is indicative of a dense environment, most likely the host galaxy of GRB 990510. Although the host is extremely faint the GRB afterglow allows us to probe its inter-(V Z 28), stellar medium andÈin principleÈto measure its metallicity. The optical spectrum of GRB 990712 (whose host galaxy is the brightest of the known GRB hosts at cosmological redshifts) shows clear features both in emission and absorption, at a redshift of z \ 0.4331^0.0004. On the basis of several line emission diagnostic diagrams, we conclude that the host galaxy of GRB 990712 is most likely an H II galaxy. We derive an unreddened [O II] star formation rate of 2.7^0.8 yr~1. Correcting for the M _ measured extinction intrinsic to the host galaxy this value increases to yr~1.width, compared to that of Ðeld galaxies at z ¹ 1, also suggests that the host of GRB 990712 is vigorously forming stars. We employ the oxygen and Hb emission-line intensities to estimate the global oxygen abundance for the host of GRB 990712 : log (O/H) \ [3.7^0.4, which is slightly below the lowest metallicity one Ðnds in nearby spiral galaxies. For both GRBs we study the time evolution of the absorption lines, whose equivalent width might be expected to change with time if the burst resides in a dense compact medium. We Ðnd no evidence for a signiÐcant change in the Mg II width.

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“…Wijers & Galama (1999) have used the multiwavelength observations of the afterglow emission of GRB 970508 to estimate the physical parameters of the burst and its surrounding interstellar medium, assuming that the afterglow is dominated by synchrotron emission. They Ðnd a total burst energy of D4 ] 1052 ergs and n D 0.04 cm~3.…”

Section: Discussionmentioning

confidence: 99%

Hubble Space TelescopeObservations of the Host Galaxy of GRB 970508

Fruchter

Pian²,

Gibbons

et al. 2000

ApJ

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We report on observations of the Ðeld of GRB 970508 made in 1998 early August, 454 days after outburst, with the STIS CCD camera on board the Hubble Space T elescope (HST ). The images, taken in open Ðlter (50CCD) mode, clearly reveal the presence of a galaxy that was overwhelmed in earlier (1997 June) HST images by emission from the optical transient (OT). The galaxy is regular in shape : after correcting for the HST /STIS PSF, it is well Ðtted by an exponential disk with a scale length of 0A .046and an ellipticity of 0.70^0.07. All observations are marginally consistent with a continuouŝ 0A .006 decline in OT emission as t~1.3 beginning 2 days after outburst ; however, we Ðnd no direct evidence in the late-time HST image for emission from the OT, and the surface brightness proÐle of the galaxy is most regular if we assume that the OT emission is negligible, suggesting that the OT may have faded more rapidly at late times than is predicted by the power-law decay. Due to the wide bandwidth of the STIS clear mode, the estimated magnitude of the galaxy is dependent on the galaxy spectrum that is assumed. Using colors obtained from late-time ground-based observations to constrain the spectrum, we Ðnd V \ 25.4^0.15, a few tenths of a magnitude brighter than earlier ground-based estimates that were obtained by observing the total light of the galaxy and the OT and then subtracting the estimated OT brightness, assuming that it fades as a single power law. This again suggests that the OT may have faded faster at late time than the power law predicts. The position of the OT agrees with that of the isophotal center of the galaxy to which, at the galaxy redshift z \ 0.83, corresponds to an o †set from the 0A .01, center of the host of pc. This remarkable agreement raises the possibility that the gamma-ray burst [70 may have been associated with either an active galactic nucleus or a nuclear starburst.

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Physical Parameters of GRB 970508 and GRB 971214 from Their Afterglow Synchrotron Emission

Cited by 450 publications

References 35 publications

GRB 991216 Joins the Jet Set: Discovery and Monitoring of Its Optical Afterglow

GRB 991216 Joins the Jet Set: Discovery and Monitoring of Its Optical Afterglow

VLT Spectroscopy of GRB 990510 and GRB 990712: Probing the Faint and Bright Ends of the Gamma‐Ray Burst Host Galaxy Population

Hubble Space TelescopeObservations of the Host Galaxy of GRB 970508

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