The GROND GRB sample: II. Fireball parameters for four GRB afterglows

Hendrik van Eerten; Jochen Greiner; Karla Varela; Patricia Schady

REVIEW 4 major objections 5 minor 16 references

The GROND GRB sample: II. Fireball parameters for four GRB afterglows

T0 review · 4 major / 5 minor · reviewed 2026-08-06 · deepseek-v4-flash

Challenge this review Re-run · record.json Download PDF Read on arXiv ↗

Pith's one-line read Dense radio-to-X-ray monitoring of four gamma-ray burst afterglows lets the authors derive all fireball parameters without prior assumptions: every burst exploded into a stellar-wind medium, and the shock-region magnetic field decays as…

desk verdict Useful data and careful fits, but the B(t) claim is mostly model-built and the SSC handling is unconvincing. read the letter →

arxiv 2507.09002 v1 pith:QNOLFVTY submitted 2025-07-11 astro-ph.HE

Karla Varela , Jochen Greiner , Patricia Schady , Hendrik van Eerten This is my paper · ORCID

classification astro-ph.HE

keywords gamma-rayburstsafterglowsfireballmodelsynchrotronemissionstellarwindenvironmentmagneticfieldevolutionshockcompressionmulti-wavelengthphotometry

verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

This paper tries to establish that complete fireball afterglow parameters can be derived for gamma-ray bursts when observations cover radio through X-rays, and that doing so for four well-sampled bursts reveals they all exploded into stellar-wind-like media and a magnetic field in the shocked region that decays as $B(t) \propto t^{-3/4}$. The temporal slope matches the prediction for a field produced by shock compression of the circumburst medium's magnetic field, rather than a field generated fresh at the shock. If correct, the result strengthens the massive-star (collapsar) progenitor scenario for long GRBs and provides a way to measure the seed magnetic field of the burst environment, inferred here to be of order milligauss. It also suggests that earlier preferences for constant-density environments in GRB afterglow samples may have been influenced by missing radio data or by assuming parameters rather than measuring them.

What carries the argument

The analysis rests on the standard synchrotron fireball model of Granot & Sari (2002), with the broadband spectrum described by three break frequencies, $\nu_{\rm sa}$, $\nu_{\rm m}$, $\nu_{\rm c}$, plus a peak flux. GROND 7-band optical/NIR photometry, Swift/XRT X-ray data, and radio/sub-mm light curves at several frequencies and epochs are fit simultaneously, using closure relations to identify the spectral regime and the external density profile. The physical parameters are then extracted per epoch from the measured break frequencies with the formulas of Granot et al. (2005), and their temporal evolution—especially the magnetic field $B(t)$—is compared with theoretical scaling predictions.

What would settle it

Recompute the parameters for GRB 110715A and 130418A including SSC cooling in the epochs used here; if the derived magnetic field no longer follows $t^{-3/4}$ or the required seed field changes by orders of magnitude, the central claim fails.

Watch

Extended reading notes

Core claim

The authors show that for GRBs 100418A, 110715A, 121024A and 130418A, multi-epoch SED fits with three synchrotron break frequencies ($\nu_{\rm sa}$, $\nu_{\rm m}$, $\nu_{\rm c}$) yield per-epoch values of the electron energy fraction $\epsilon_e$, magnetic energy fraction $\epsilon_B$, wind density normalization $A_*$, and isotropic kinetic energy $E_{\rm K,iso}$, without assuming any of them. All four bursts require a wind-like external density profile ($k = 2$), and the derived magnetic field in the shocked region evolves as $t^{-3/4}$, consistent with shock amplification of the ambient magnetic field; the required seed field in the circumburst medium is about 10 mG. The break frequencies themselves evolve in time as predicted by the standard model, and $\epsilon_e$ is constant over the observed epochs.

Load-bearing premise

The derivation treats the electrons as cooling only through synchrotron emission during the epochs used to measure the magnetic field, even though for at least one burst the derived parameters imply inverse-Compton (SSC) cooling should be significant; if SSC matters, the inferred magnetic field and its time evolution would be biased.

Editorial extensions

If this is right

The wind-like density profiles found for all four afterglows support the collapsar scenario for long GRBs and suggest that earlier ISM identifications often relied on assumptions or data that could not distinguish the profiles.
The measured $B(t) \propto t^{-3/4}$ means the magnetic field in the shocked region is consistent with being amplified by shock compression of a pre-existing circumburst field, with a seed field of order a few mG.
The radio and sub-mm data were decisive: without them the break frequencies $\nu_{\rm sa}$ and $\nu_{\rm m}$ could not be tracked, and the external density profile would remain ambiguous.
The constancy of $\epsilon_e$ and the measured evolution of the break frequencies provide independent tests of the standard afterglow model across epochs.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

If the $B(t) \propto t^{-3/4}$ scaling holds for more afterglows, the common practice of treating $\epsilon_B$ as constant throughout a burst should be replaced by an evolving $\epsilon_B$, which changes energy estimates derived from afterglow modelling.
The mG seed field, if it is a general property of GRB environments, would mean the medium around the progenitor is far more magnetized than the typical Galactic interstellar field, possibly reflecting the stellar wind or the star-forming region.
A direct test would be to apply the same epoch-by-epoch, SSC-checked method to other GRBs with full radio-to-X-ray coverage, to see whether the wind preference and the $t^{-3/4}$ slope reproduce or whether they are peculiar to this sample.

Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Desk Editor's Note

read the letter

What is new here: three genuinely new multi-wavelength analyses (100418A, 110715A, 130418A) plus a re-analysis (121024A), added to the short list of afterglows where all fireball parameters are measured without prior assumptions. The GROND photometry, SED fitting, and closure-relation work are done carefully, with attention to host extinction, X-ray absorption, and scintillation. The Appendix C compilation, with candid comments on which literature results actually measure all parameters, is useful. The soft spot is the central B(t) claim. The paper frames the t^-3/4 slope as a new measurement supporting shock compression. But if epsilon_B is constant and you assume a wind profile with adiabatic blast-wave dynamics, B(t) automatically scales as t^-3/4; it is a consequence of the very model used to derive the parameters, not an independent test. Since the fitted epsilon_B is consistent with being constant, the measurement is essentially a restatement of the assumed dynamics. The agreement with -3/4 carries little evidential weight. The SSC issue is more serious. For 110715A, the derived epsilon_e/epsilon_B > 590 implies a Compton parameter well above unity, so SSC should dominate cooling. The authors discard the SSC-included fit because it gives epsilon_B ~ 10, but that is not a valid reason to ignore a cooling process the physics requires. For 130418A, the paper explicitly states that SSC dominated early and that A*~45 satisfies the IC-dominance criterion, yet fits the later epochs with pure synchrotron equations. If SSC is important in those epochs, the derived epsilon_B, A*, and B are biased, and the B(t) slope may be an artifact of an incomplete cooling model. There is also the sample selection caveat: these four bursts were chosen for radio detections and clean SEDs, so the wind-environment conclusion for the population should be stated more cautiously. The wind interpretation for these particular bursts is plausible, and the break-frequency evolutions generally match the wind predictions. The data are solid and the reporting is honest about inconsistencies. Recommendation: I would send this to peer review. The data and fits are valuable, and the claims can be fixed with a more honest discussion of model dependence and a direct confrontation of the SSC diagnostics. A referee should request that, but the paper deserves referee time.

Referee Report

4 major / 5 minor

Summary. The paper presents a detailed multi-wavelength (radio to X-ray) analysis of four GRB afterglows observed with GROND, Swift/XRT, and radio/sub-mm facilities. The authors derive the three synchrotron break frequencies epoch by epoch, obtain physical parameters (E_K, ε_e, ε_B, A*, and jet angles) from the Granot & Sari (2002) formalism, and report two main conclusions: (1) all four bursts expanded into a stellar-wind-like circumburst medium, and (2) the magnetic field in the shocked region evolves as B(t) ∝ t^{-3/4}, which they interpret as evidence for shock compression of a seed CBM field. The paper also compiles a critical list of GRBs with (claimed) complete fireball parameter measurements and compares their results with the literature.

Significance. If the conclusions are robust, the paper provides a rare dataset with break frequencies measured at multiple epochs and a direct look at the temporal evolution of the fireball parameters. The wind-environment result for all four bursts, if free of selection bias, would be an interesting contribution to the debate on GRB progenitor environments. The B(t) ∝ t^{-3/4} claim, however, is the most novel but also the most fragile: the slope is largely an internal consistency check of the adopted synchrotron model, and it rests on epoch-by-epoch ε_B values that may be biased by neglected SSC cooling. The manuscript's strengths are the high-quality, well-calibrated GROND photometry, the explicit handling of host extinction and absorption, the exhaustive compilation in Appendix C, and the clear presentation of the closure-relation logic. These strengths are diminished by the unresolved SSC issue and by the sample-selection bias inherited from the radio-detection requirement.

major comments (4)

[Sec. 3.3.2 and Sec. 3.3.4] The exclusion of SSC-included solutions is not justified by the presented evidence. For GRB 110715A the text states that ε_e/ε_B > 590 (which implies a Compton parameter Y ≫ 1), yet the parameters listed in Tables 6–7 are obtained from synchrotron-only fits, with the rationale that the SSC fit returns an 'unphysical' ε_B ≈ 10. For GRB 130418A the authors note A* ≈ 45 satisfies the A* > 10 criterion for IC dominance and that SSC dominated the early afterglow, but they again adopt the no-SSC fit because the SSC-included solution gives ε_B ~ 10^3. Discarding a cooling process because the model that includes it gives an uncomfortable parameter is circular: the no-SSC model itself indicates that the process should be important. The derived ε_B, A*, and hence B in Tables 8, 9, and 13 are therefore potentially strongly biased. Since the central B(t) ∝ t^{-3/4} claim (Sec. 4.2.3, Fig. 23) is built on these values, the authors must either self-consistently include SSC cooling in the parameter derivation (e.g., via a Compton parameter Y coupled to ε_e/ε_B) or demonstrate quantitatively that the synchrotron-only results are unaffected when SSC is properly included.
[Sec. 4.2.3] The 'prediction' B(t) ∝ t^{-3/4} is not independent of the model used to derive B. The paper uses B = (32π m_p c^2 n)^{1/2} γ ε_B^{1/2} with a wind density n ∝ t^{-1} and decelerating dynamics γ ∝ t^{-1/2}. With ε_B assumed constant, this formula automatically gives B ∝ t^{-3/4}. Therefore the measured slopes in Table 13 (0.81 ± 0.05, 0.78 ± 0.04, 0.67 ± 0.04) are a check of internal consistency of the adopted standard model, not evidence for shock compression of a seed field. The text should state this explicitly and, if the claim is to be made, compare against a genuinely alternative model (e.g., a decaying micro-turbulence prescription with a different predicted B(t) scaling) using the same data. As written, the claim in Sec. 5 that the evolution 'is found to be in agreement with the prediction' of shock amplification overstates what the analysis can establish.
[Sec. 2 and Sec. 5] The sample selection introduces a strong bias that is not adequately discussed. The paper states that of 54 GROND GRBs only 8 have radio detections, and that the four analysed bursts are those with ≥2 radio frequencies over ≥2 epochs and a clean single-synchrotron SED description. This selection likely favors afterglows with bright, well-behaved radio emission, which are more likely to be wind-like or to have favorable geometry. The conclusion that 'all four GRBs exploded into a wind environment' (Sec. 5) and the extrapolation to a 'larger percentage of GRBs associated with a wind profile' (Sec. 4.2.2) therefore conflate a property of the selected sample with a statement about the GRB population. The authors should add an explicit caveat that the wind fraction is measured in a radio-selected sub-sample, and ideally quantify the selection function from the parent GROND sample.
[Table 13] The reported B(t) slope for GRB 130418A is not well constrained. Table 13 lists α(B) = 0.67 ± 0.04, but this is derived from only two epochs with measurements (Table 9, SED I and II), while SED III provides only limits. A linear fit to two points has no internal scatter, so the quoted uncertainty reflects only the propagated parameter errors and not the true systematics. This row should be reported as a two-point constraint with an appropriate caveat, and the combined evidence in Fig. 23 should clearly distinguish the 2-point result from the 5- and 6-point results for GRBs 100418A and 110715A.

minor comments (5)

[Throughout] The text uses 'CMB' and 'CBM' interchangeably (e.g., 'circumburst medium (CBM)' in Sec. 3.3.1 and 'CMB profile' in the overall picture of Sec. 3.3.2). Please use CBM consistently to avoid confusion with the cosmic microwave background.
[Eq. (1)] The third case in Eq. (1) for the double broken power-law appears to have a misprint: the argument of the outer parentheses is not well defined as written. Please verify the formula.
[Sec. 3.2.2] In the discussion of the GRB 110715A SEDs, the text first reports a pure optical/NIR slope of β = 0.35 ± 0.12 and then a combined optical/XRT slope of β = 1.05 ± 0.01. The reason for this large difference and the final adopted value should be stated more clearly.
[Sec. 3.3.2] The statement 'ϵ_e/ϵ_B > 590' is given without a formal uncertainty; since the ratio is derived from two parameters with errors, please provide a propagated uncertainty or a range.
[Appendix C] The compilation in Appendix C is valuable but necessarily subjective; the text acknowledges this, but the sentence in Sec. 4.2.1 that the new GRBs 'tip the balance towards the wind environment' would benefit from an explicit dependence on the inclusion/exclusion criteria used.

Circularity Check

1 steps flagged · score 6.0 of 10

The B(t) ∝ t^{-3/4} agreement is a built-in consequence of the standard model used to derive B, not an independent test of shock compression; the remaining parameter derivation is largely self-contained.

fitted input called prediction [Sec. 3.3.2 (B formula), Sec. 4.2.3, Fig. 23 and Table 13 (B-slope test)]
"B = (32πmpc2n)1/2γ ϵB1/2; Sari et al. 1996 ... The evolution that we find follows the predictions for a magnetic field, which originates due to shock compression, t−3/(2(4−k)) (= t−3/4 for our case of k = 2; Blandford & McKee 1976; Rybicki & Lightman 1979; Inoue et al. 2011). It has no additional assumptions or linked parameters among the analysed epochs of each afterglow. This implies that the observed evolution relies completely on the derived parameters for each SED and actually tests the evolution of the magnetic field in the shocked region independently."

The plotted B values are not directly observed; they are computed with the same Granot-Sari standard-model formula used to fit ε_B, with n and γ taken from the assumed wind deceleration dynamics. For constant ε_B that formula gives B ∝ t^{-3/4} identically, because the model has n ∝ r^{-2} and γ ∝ t^{-1/4}. The fitted ε_B slopes (0.20±0.11, 0.04±0.06, -0.29±0.03) are consistent with constant, so the derived B slope is forced near -3/4 by the assumed dynamics. The agreement is therefore a consistency check of the input model, not an independent measurement of B(t) and not an independent test of the shock-compression origin; the claim that the evolution is tested independently is not supported by the construction.

full rationale

The multi-epoch SED analysis is mostly self-contained: break frequencies are measured from broadband radio-to-X-ray data, closure relations select the wind profile, and microphysical parameters are solved epoch by epoch from published synchrotron relations. The wind-environment conclusion, the constancy of ε_e, and the break-frequency evolution tests are genuine data-driven results. The circularity is confined to the headline magnetic-field claim: B(t) is computed from the same Granot-Sari model whose dynamics already imply B ∝ t^{-3/4} for a wind and constant ε_B, so the agreement in Table 13 and Fig. 23 is partly built in. A further correctness risk, not itself a circular step, is that for GRB 110715A the paper finds ε_e/ε_B > 590 and for GRB 130418A A* ≈ 45 with early SSC dominance, yet discards the SSC-included fits because they give ε_B ≈ 10; the no-SSC ε_B values feeding the B(t) test are therefore conditional on an assumption weakened by the authors' own diagnostics. No load-bearing self-citation was found: the use of Varela et al. (2016) for GRB 121024A is a normal reference to a published analysis. Overall, the central B(t) slope claim partially reduces to the model used to derive it, so the score is 6.

Assumptions & free parameters 5 free parameters · 8 assumptions · 0 invented entities

No new physical entities are introduced. The 'seed magnetic field of order mG' is an inferred physical quantity from the fitted epsilon_B and A*, not a new postulated entity.

free parameters (5)

Break frequencies nu_c, nu_m, nu_sa per epoch = Tables 1-3
Fitted to the broadband SEDs at each epoch; these are the primary observables from which physical parameters are derived.
Energy injection parameter q = q = 0.23, -0.36, 0.52, 0.14 for the four GRBs (Table 14)
Fitted from the plateau light curve shapes; used to model the energy injection phase.
Host extinction A_v^host = 0.01-0.18 mag (Table 11)
Fitted in the SED analysis; affects optical/NIR fluxes and thus derived parameters.
Host column density N_H^host = 0.08-0.57 x 10^22 cm^-2
Fitted to X-ray SEDs.
Light curve smoothness parameters sm = e.g., sm=15 +/- 11, 6.9 +/- 1.3
Ad hoc smoothing parameters in the broken power-law fits.

assumptions (8)

domain assumption The standard GRB afterglow model as in Granot & Sari (2002): emission is synchrotron radiation from a decelerating relativistic blast wave.
Section 1 and 3.1.2; this is the framework for interpreting all data.
domain assumption Electron energy distribution is a power law with index p, with p > 2 assumed.
Section 1; this keeps the electron energy finite and is used in the closure relations.
domain assumption External density profile is either ISM (k=0) or wind (k=2), with no intermediate values.
Section 3.3; only these two profiles are considered in the closure relations and parameter derivation.
domain assumption Energy injection model for plateau phases: L(t) = L0 t^{-q}.
Section 3.1.2; plateaus are interpreted as prolonged energy injection rather than other proposed mechanisms.
domain assumption Closure relations are valid and uniquely identify the spectral regime and density profile.
Section 3.1.2; used to select among scenarios for each burst.
domain assumption Jet break follows the uniform non-spreading jet model.
Section 3.3, using Granot et al. (2005) Eq. 4 for the half-opening angle.
domain assumption Extinction laws (MW, SMC, LMC) from Pei (1992) and Galactic extinction values from Schlafly & Finkbeiner (2011).
Section 3.1.1 and Appendix B; these are used to correct the SEDs before fitting.
domain assumption Interstellar scintillation can be treated as an added systematic error on radio fluxes.
Appendix B, Table B.5 note; this affects the radio light curve fits and break frequency measurements.

how reviews work

0 comments

Cite this review

Pith. "Pith review of The GROND GRB sample: II. Fireball parameters for four GRB afterglows." pith.science (2026). https://pith.science/paper/QNOLFVTY

@misc{pith2026250709002,
  author       = {Pith},
  title        = {Pith review of: The GROND GRB sample: II. Fireball parameters for four GRB afterglows},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/QNOLFVTY}},
  note         = {Machine review of arXiv:2507.09002}
}

read the original abstract

Afterglows of GRBs are, in general, well described by the fireball model. Yet, deducing the full set of model parameters from observations without prior assumptions has been possible for only a handful of GRBs. With GROND, a 7-channel simultaneous optical and near-infrared imager at the 2.2m telescope of the Max-Planck Society at ESO/La Silla, a dedicated gamma-ray burst (GRB) afterglow observing program was performed between 2007 and 2016. Here, we combine GROND observations of four particularly well-sampled GRBs with public Swift/XRT data and partly own sub-mm and radio data to determine the basic fireball afterglow parameters. We find that all four bursts exploded into a wind environment. We are able to infer the evolution of the magnetic field strength from our data, and find evidence for its origin through shock amplification of the magnetic field of the circumburst medium.

Figures

Figures reproduced from arXiv: 2507.09002 by the authors.

**Figure 1.** X-ray light curve of GRB 100418A from the XRT repository. The best fit is a smoothly double broken power-law shown in dashed lines. The epochs used are marked by vertical shaded regions: the steep decay phase (white), the plateau phase (blue), and the post-energy injection phase after a jet break (light green) [PITH_FULL_IMAGE:figures/full_fig_p004_1.png] view at source ↗

**Figure 2.** GROND light curve g ′ r ′ i ′ z ′ JHKs of the afterglow of GRB 100418A. The best fit of the combined optical/NIR and X-ray data is a smooth broken power-law with host contribution shown in dash lines. The epochs used for the spectral analysis are highlighted with the vertical bars. The first two epochs highlighted in light red correspond to the energy injection phase. The last five epochs in orange correspond to th… view at source ↗

**Figure 3.** Sub-mm and radio light curves of the GRB 100418A afterglow at different frequencies, with dashed lines showing the best fit. The eight highlighted vertical regions correspond to the epochs used in the SED analysis. The orange (blue) regions correspond to the fast (slow) cooling regime. The light curves are scaled by an arbitrary factor for clarity. Article number, page 4 of 27 [PITH_FULL_IMAGE:figures/full_fig_p004… view at source ↗

Figures from the paper (16 more)

**Figure 4.** Figure 4: SEDs of the afterglow of GRB 100418A using GROND and XRT data at five epochs: SED1 (t=130.9 ks), SED2 (t=202.1 ks), SED3 (t=217.8 ks), SED4 (t=296.8 ks), SED5 (t=476.4 ks). For clarity, the SEDs are scaled arbitrarily (GROND magnitudes are given in Table B.1). The best…

**Figure 6.** Figure 6: Evolution of the measured break frequencies for the eight optical to radio SEDs for the GRB 100418A afterglow. The solid lines represent the expected theoretical evolution for a wind environment during fast (<600 ks) and slow (>600 ks) cooling. The coloured dashed lin…

**Figure 5.** Figure 5: Broadband SED analysis for GRB 100418A, using eight epochs analysed using multi-epoch broad-band observations. The first three epochs correspond to the fast cooling regime (SED1r - SED3r); the last five epochs (SED4r - SED8r) correspond to the slow cooling regime. The …

**Figure 8.** Figure 8: GROND g ′ r ′ i ′ z ′ JHKs light curve of the GRB 110715A afterglow. The best fit is a single power-law with α= 1.51±0.03 as shown with the dashed lines. The epochs used for the spectral analysis are highlighted with the vertical bars. All four epochs are after the pl…

**Figure 7.** Figure 7: X-ray light curve of the GRB 110715A afterglow, described by a smooth double broken power-law shown in dashed lines. The 3 regions used in the SED analysis are shown as shaded areas, corresponding to the GRB tail, the plateau and the final decay phase, respectively. We…

**Figure 10.** Figure 10: Broad-band analysis of the GRB 110715A afterglow. Six epochs are presented with all the breaks measured [PITH_FULL_IMAGE:figures/full_fig_p007_10.png]

**Figure 11.** Figure 11: Evolution of the break frequencies of the afterglow of GRB 110715A. The last SED is not included in the fit because the values for the optical/NIR bands were extrapolated. Lines are as in [PITH_FULL_IMAGE:figures/full_fig_p007_11.png]

**Figure 14.** Figure 14: Broad-band SEDs of the GRB 130418A afterglow at the three epochs of [PITH_FULL_IMAGE:figures/full_fig_p008_14.png]

**Figure 15.** Figure 15: Evolution of the break frequencies of the GRB 130418A afterglow. Lines are as in [PITH_FULL_IMAGE:figures/full_fig_p008_15.png]

**Figure 16.** Figure 16: Slow cooling: Evolution of the derived dynamical (top) and microphysical (bottom) parameters of the afterglow of GRB 100418A without SSC emission. The blue dashed lines and shaded regions represent the results from the fit of the observed temporal evolution. The hori…

**Figure 17.** Figure 17: Evolution of the derived microphysical and dynamical parameters of the afterglow of GRB 110715A, for the case without IC emission. The dashed-lines in cyan and shaded regions represent results from the fit of the observed temporal evolution (open data points were lef…

**Figure 18.** Figure 18: Evolution of the derived microphysical and dynamical parameters of the afterglow of GRB 130418A. without IC. The dashed lines in cyan represent the results from the fit of the observed temporal evolution, although this is only the connection of two points, since the…

**Figure 19.** Figure 19: Evolution of the energy efficiency η, magnetic field B, mass loss rate M˙ , opening angle θ0 derived from the measured microphysical and dynamical parameters of the afterglow of GRB 130418A with (top) and without (bottom) IC included. The dashed lines represent the re…

**Figure 20.** Figure 20: Evolution of the break frequencies νc (top), νm (middle) and νsa (bottom) for the afterglows of our four GRBs. The solid lines corresponds to the expected evolution of each frequency from the standard afterglow theory. The shaded regions are the fits for each break …

**Figure 22.** Figure 22: Collection of ϵe and ϵB parameters as deduced from multiwavelength modelling of afterglows (see Tab. C.1), with literature values for wind (blue) and ISM (orange) profile, and our four GRB afterglows in red (all wind). The shaded region is the narrow ϵe distributio…

**Figure 23.** Figure 23: Evolution of the secondary quantities according to the GRB afterglow standard model. The dashed-lines show the average value of each parameter. The dotted lines represent the power-law fit to the data. B has a slope −3/4 as expected from a magnetic field amplified by …

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

16 extracted references · 15 canonical work pages

[1]

D., Wijers, R

Aksulu, M. D., Wijers, R. A. M. J., van Eerten, H. J., & van der Horst, A. J. 2020, MNRAS, 497, 4672 Alexander, K. D., Laskar, T., Berger, E., et al. 2017, ApJ, 848, 69 Antonelli, L. A., Maund, J. R., Palazzi, E., et al. 2010, GRB Coordinates Net- work, 10620 Arnaud, K. A. 1996, in Astron. Soc. Pacific Conf. Ser., V ol. 101, Astronomical Data Analysis Sof...

arXiv 2020
[2]

Two epochs during the energy injection phase and five epochs after the break in the light curve

SED mid-time [ks] g′(mAB) r′(mAB) i′(mAB) z′(mAB) J(mVega) H(mVega) Ks(mVega) I* 27.7 18.99 ±0.05 18.64 ±0.05 18.33 ±0.07 18.08 ±0.07 17.63 ±0.07 17.26 ±0.08 17.18 ±0.14 II* 40.2 19.11 ±0.05 18.48 ±0.07 18.77 ±0.06 18.24 ±0.07 17.81 ±0.09 17.49 ±0.10 17.15 ±0.12 I 130.9 20.20 ±0.06 19.87 ±0.06 19.56 ±0.07 19.36 ±0.07 18.93 ±0.09 18.66 ±0.12 18.34 ±0.11 II...

work page 2010
[3]

2012; Moin et al

Radio We also use published data from the Very Large Array (VLA), the Australian Telescope Compact Array (ATCA) and the Westerbork Synthesis Radio Telescope (WSRT) (Chandra & Frail 2012; de Ugarte Postigo et al. 2012; Moin et al. 2013). A TCA follow-up observation began on April 20th. The afterglow was followed for three epochs on the 2nd, 38th and 67th d...

work page 2012
[8]

(J2000) = 15:50:44.10, -46:14:06.2 with an uncertainty of 0.′′4 in each coordinate (Fig

at position RA, Decl. (J2000) = 15:50:44.10, -46:14:06.2 with an uncertainty of 0.′′4 in each coordinate (Fig. A.1). VLT/X-shooter spectroscopy identified the redshift as z= 0.82 (Piranomonte et al. 2011). Observations continued on the 2nd, 4th, 6th and 8th night after the burst. The data were corrected for the Galactic foreground reddening of E(B− V)=0.5...

work page 2011
[9]

LABOCA started observations on July 16 at 23:21 UT, observed for about 1.47 hours, and detected the source with a flux of 11.0±2.3 mJy (de Ugarte Postigo et al. 2011). ALMA observed the source 2.5 days after the detection by Swift. The source was detected with a flux of 4.9±0.60 mJy (de Ugarte Postigo et al. 2012). Radio: ATCA Radio observations were perf...

work page 2011
[10]

The observations at 9.0 GHz resulted in four detections and one upper limit

and continued for more than 2.5 months at four different frequencies (5.5, 9.0, 18.0, and 44.0 GHz). The observations at 9.0 GHz resulted in four detections and one upper limit. Details on the fluxes are given in Table B.5 and Fig. 9 (Chandra & Frail 2012). Table B.4. Observed GROND magnitudes of the GRB 110715A afterglow for the epochs used in the SED an...

work page 2012
[11]

Radio observations include an additional systematic uncertainty of 30% to take into account the effects of interstellar scintillation. B.3. GRB 130418A Swift On April 18th 2013 the Swift Burst Alert Telescope detected GRB 130418A (de Pasquale et al

work page 2013
[12]

Swift slewed to the position of the GRB and started observations 129.7 seconds after the trigger

at 19:00:53 UT. Swift slewed to the position of the GRB and started observations 129.7 seconds after the trigger. The X-ray afterglow was detected by Swift/XRT at a position RA, Decl.(J2000)= 09:56:9.05, 13:39:55.4 with an uncertainty of 5.′′3. The observations were performed in Windowed Timing (WT) mode within the time interval from T0 + 136 s to T0 + 35...

work page 2007

Show all 16 references

[13]

The observations were performed simultaneous in 7 bands in a wavelength range from 400-2400 nm ( g′r′i′z′JHK s)

and continued for the next three hours. The observations were performed simultaneous in 7 bands in a wavelength range from 400-2400 nm ( g′r′i′z′JHK s). The optical counterpart was detected in all 7 bands at a position RA, Decl.(J2000) = 09:56:8.85, 13:40:02.0 with an uncertai...

2014
[15]

(2007) assumeϵe,ϵB<1/3 – 050820A: Cenko et al

– 050416A: Withνa unconstrained, Soderberg et al. (2007) assumeϵe,ϵB<1/3 – 050820A: Cenko et al. (2010) find two alternative solutions with different p. – 051022: Without optical detection, no distinction between ISM and wind environment is possible, and ϵe and ϵB are not well...

2007
[16]

standard

– 090510: Beniamini et al. (2015) assumeϵe= 0.1 – 090902B: Cenko et al. (2011) find a better fit for an ISM density profile, but fix either ϵB (according to their Tab.10) or ϵe (according to their text) at the equipartition value. Beniamini et al. (2015) assume ϵe= 0.1. Lemoin...

2015
[2003]

– 021004: Björnsson et al

– 020813: Panaitescu (2005) find no unique solution, with fireball parameters varying drastically depending on the model. – 021004: Björnsson et al. (2004) set p=2.2, and the jet break time is set from the polarisation variation, though it is not seen in the optical light curv...

2005
[2005]

The analysis of the white filter data of the first 150 seconds located the source at RA, Decl

observed the afterglow during the same time interval as Swift/XRT. The analysis of the white filter data of the first 150 seconds located the source at RA, Decl. (J2000.0)=17:05:26.96, 11:27:41.9 with an uncertainty of 1.′′0 (Marshall et al. 2010). The observations show an ini...

2010
[2010]

The afterglow was detected in all 7 bands at the position RA, Decl

and continued for 6 hours during the first night. The afterglow was detected in all 7 bands at the position RA, Decl. (J2000) = 17:05:27.09, 11:27:42.3 with an uncertainty of 0.′′4 in each coordinate (Fig. A.1). VLT/X-shooter spectroscopy of this optical afterglow revealed a r...

2010
[2011]

Swiftslewed immediately to the position of the burst, and the observations started 90 s after the trigger

the SwiftBurst Alert Telescope triggered on and located GRB 110715A. Swiftslewed immediately to the position of the burst, and the observations started 90 s after the trigger. The afterglow was located at RA, Decl. (J2000) = 15:50:44.07, -46:14:09.0 with an uncertainty of 2.′′...

2011
[2013]

It was also observed at frequencies of 4.95 GHz, 4.9 GHz and 7.9 GHz (see Table B.3)

between 2 and 157 days after the trigger. It was also observed at frequencies of 4.95 GHz, 4.9 GHz and 7.9 GHz (see Table B.3). B.2. GRB 110715A Swift On 2011 July 15 at T0 = 13:13:50 UT (Sonbas et al

2011

Pith tools

Reviewed August 6, 2026 · model on record in the stance chip above.

[1] [1]

D., Wijers, R

Aksulu, M. D., Wijers, R. A. M. J., van Eerten, H. J., & van der Horst, A. J. 2020, MNRAS, 497, 4672 Alexander, K. D., Laskar, T., Berger, E., et al. 2017, ApJ, 848, 69 Antonelli, L. A., Maund, J. R., Palazzi, E., et al. 2010, GRB Coordinates Net- work, 10620 Arnaud, K. A. 1996, in Astron. Soc. Pacific Conf. Ser., V ol. 101, Astronomical Data Analysis Sof...

arXiv 2020

[2] [2]

Two epochs during the energy injection phase and five epochs after the break in the light curve

SED mid-time [ks] g′(mAB) r′(mAB) i′(mAB) z′(mAB) J(mVega) H(mVega) Ks(mVega) I* 27.7 18.99 ±0.05 18.64 ±0.05 18.33 ±0.07 18.08 ±0.07 17.63 ±0.07 17.26 ±0.08 17.18 ±0.14 II* 40.2 19.11 ±0.05 18.48 ±0.07 18.77 ±0.06 18.24 ±0.07 17.81 ±0.09 17.49 ±0.10 17.15 ±0.12 I 130.9 20.20 ±0.06 19.87 ±0.06 19.56 ±0.07 19.36 ±0.07 18.93 ±0.09 18.66 ±0.12 18.34 ±0.11 II...

work page 2010

[3] [3]

2012; Moin et al

Radio We also use published data from the Very Large Array (VLA), the Australian Telescope Compact Array (ATCA) and the Westerbork Synthesis Radio Telescope (WSRT) (Chandra & Frail 2012; de Ugarte Postigo et al. 2012; Moin et al. 2013). A TCA follow-up observation began on April 20th. The afterglow was followed for three epochs on the 2nd, 38th and 67th d...

work page 2012

[4] [8]

(J2000) = 15:50:44.10, -46:14:06.2 with an uncertainty of 0.′′4 in each coordinate (Fig

at position RA, Decl. (J2000) = 15:50:44.10, -46:14:06.2 with an uncertainty of 0.′′4 in each coordinate (Fig. A.1). VLT/X-shooter spectroscopy identified the redshift as z= 0.82 (Piranomonte et al. 2011). Observations continued on the 2nd, 4th, 6th and 8th night after the burst. The data were corrected for the Galactic foreground reddening of E(B− V)=0.5...

work page 2011

[5] [9]

LABOCA started observations on July 16 at 23:21 UT, observed for about 1.47 hours, and detected the source with a flux of 11.0±2.3 mJy (de Ugarte Postigo et al. 2011). ALMA observed the source 2.5 days after the detection by Swift. The source was detected with a flux of 4.9±0.60 mJy (de Ugarte Postigo et al. 2012). Radio: ATCA Radio observations were perf...

work page 2011

[6] [10]

The observations at 9.0 GHz resulted in four detections and one upper limit

and continued for more than 2.5 months at four different frequencies (5.5, 9.0, 18.0, and 44.0 GHz). The observations at 9.0 GHz resulted in four detections and one upper limit. Details on the fluxes are given in Table B.5 and Fig. 9 (Chandra & Frail 2012). Table B.4. Observed GROND magnitudes of the GRB 110715A afterglow for the epochs used in the SED an...

work page 2012

[7] [11]

Radio observations include an additional systematic uncertainty of 30% to take into account the effects of interstellar scintillation. B.3. GRB 130418A Swift On April 18th 2013 the Swift Burst Alert Telescope detected GRB 130418A (de Pasquale et al

work page 2013

[8] [12]

Swift slewed to the position of the GRB and started observations 129.7 seconds after the trigger

at 19:00:53 UT. Swift slewed to the position of the GRB and started observations 129.7 seconds after the trigger. The X-ray afterglow was detected by Swift/XRT at a position RA, Decl.(J2000)= 09:56:9.05, 13:39:55.4 with an uncertainty of 5.′′3. The observations were performed in Windowed Timing (WT) mode within the time interval from T0 + 136 s to T0 + 35...

work page 2007