Detailed multiwavelength modelling of the dark GRB 140713A and its host galaxy

Abstract

We investigate the afterglow of GRB 140713A, a gamma-ray burst (GRB) that was detected and relatively well-sampled at X-ray and radio wavelengths, but was not present at optical and near-infrared wavelengths, despite searches to deep limits. We present the emission spectrum of the likely host galaxy at z = 0.935 ruling out a highredshift explanation for the absence of the optical flux detection. Modelling the GRB multi-wavelength afterglow using the radiative transfer hydrodynamics code boxfit provides constraints on physical parameters of the GRB jet and its environment, for instance a relatively wide jet opening angle and an electron energy distribution slope p below 2. Most importantly, the model predicts an optical flux about two orders of magnitude above the observed limits. We calculated that the required host extinction to explain the observed limits in the r, i and z bands was A host V > 3.2 mag, equivalent to E(B − V) host > 1.0 mag. From the X-ray absorption we derive that the GRB host extinction is A host V = 11.6 +7.5 −5.3 mag, equivalent to E(B − V) host = 3.7 +2.4 −1.7 mag, which is consistent with the extinction required from our boxfit derived fluxes. We conclude that the origin of the optical darkness is a high level of extinction in the line of sight to the GRB, most likely within the GRB host galaxy.

A Radio-selected Population of Dark, Long Gamma-Ray Bursts: Comparison to the Long Gamma-Ray Burst Population and Implications for Host Dust Distributions

“…Therefore, IC effects cannot account for the excess X-ray flux, although we note that such excess emission has been seen in other events (Fong et al 2014;Margutti et al 2015;Laskar et al 2018aLaskar et al , 2019. Higgins et al (2019) previously modeled the afterglow of GRB 140713A. Their model allowed for p < 2, and they found a value of p ≈ 1.85, smaller, but not far off from our value of p ≈ 2.17.…”

“…The afterglow of GRB 140713A has been previously modeled by Higgins et al (2019), though they did not include IC effects. We choose to model GRB 140713A in our modeling framework both for consistency across the bursts in our sample, and because we are introducing new VLA and 3 mm afterglow observations that have not previously been modeled.…”

“…Left: X-ray, optical, millimeter, and radio afterglow light curves of GRB 140713A, together with the best-fit forward shock model in a wind environment (lines). Squares represent data newly reported here, circles represent literature data (Higgins et al 2019), and triangles represent 3σ upper limits. Open symbols indicate data that are not included in the fit, and shaded regions represent variability due to scintillation.…”

“…The upgrade to the Karl G. Jansky Very Large Array (VLA), which concluded in 2012, increased the sensitivity of the radio array by a factor of ∼10 (Perley et al 2011), and has allowed for well-sampled, multiband, follow-up of long GRB radio afterglows (including, but not limited to the following studies: Chandra & Frail 2012;Laskar et al 2013c;Zauderer et al 2013c;Laskar et al 2014Laskar et al , 2015Laskar et al , 2016Alexander et al 2017;Laskar et al 2018aLaskar et al , 2018bLaskar et al , 2018c. Radio observations of dust-obscured dark GRBs are critical for properly modeling the afterglow of these bursts, especially when the optical afterglow is not detected (e.g., Jakobsson et al 2005;Castro-Tirado et al 2007;Rol et al 2007;Zauderer et al 2013c;van der Horst et al 2015;Higgins et al 2019;Kangas & Fruchter 2021), as the low-frequency afterglow can constrain burst energetics and environment density through determination of the synchrotron break frequencies (e.g., Sari et al 1998;Granot & Sari 2002).…”

The case for a high-redshift origin of GRB 100205A

“…Contours representing the 67, 95 and 99.5 per cent frequentist probability intervals are overlaid in black. tion (see for examplePerley et al 2009;Greiner et al 2011;Svensson et al 2012;Perley et al 2013;Zauderer et al 2013;Jeong et al 2014a;van der Horst et al 2015;Higgins et al 2019;Chrimes et al 2019…”