A VLA Study of High-redshift GRBs. I. Multiwavelength Observations and Modeling of GRB 140311A

作者：Laskar Tanmoy; Berger Edo; Chornock Ryan; Margutti Raffaella; Fong Wen fai; Zauderer B Ashley

来源：Astrophysical Journal, 2018, 858(1): 65.

DOI：10.3847/1538-4357/aab8f5

<jats:title>Abstract</jats:title>
<jats:p>We present the first results from a recently concluded study of GRBs at <jats:italic>z</jats:italic> ≳ 5 with the Karl G. Jansky Very Large Array (VLA). Spanning 1 to 85.5 GHz and 7 epochs from 1.5 to 82.3 days, our observations of GRB 140311A are the most detailed joint radio and millimeter observations of a GRB afterglow at <jats:italic>z</jats:italic> ≳ 5 to date. In conjunction with optical/near-IR and X-ray data, the observations can be understood in the framework of radiation from a single blast wave shock with energy <jats:inline-formula>
<jats:tex-math>
<?CDATA ${E}_{{\rm{K}},\mathrm{iso}}\approx 8.5\times {10}^{53}$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaab8f5ieqn1.gif" xlink:type="simple" />
</jats:inline-formula> erg expanding into a constant density environment with density, <jats:inline-formula>
<jats:tex-math>
<?CDATA ${n}_{0}\approx 8$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaab8f5ieqn2.gif" xlink:type="simple" />
</jats:inline-formula>
<jats:inline-formula>
<jats:tex-math>
<?CDATA ${\mathrm{cm}}^{-3}$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaab8f5ieqn3.gif" xlink:type="simple" />
</jats:inline-formula>. The X-ray and radio observations require a jet break at <jats:inline-formula>
<jats:tex-math>
<?CDATA ${t}_{\mathrm{jet}}\approx 0.6$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaab8f5ieqn4.gif" xlink:type="simple" />
</jats:inline-formula> days, yielding an opening angle of <jats:inline-formula>
<jats:tex-math>
<?CDATA ${\theta }_{\mathrm{jet}}\approx 4^\circ $?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaab8f5ieqn5.gif" xlink:type="simple" />
</jats:inline-formula> and a beaming-corrected blast wave kinetic energy of <jats:inline-formula>
<jats:tex-math>
<?CDATA ${E}_{{\rm{K}}}\approx 2.2\times {10}^{50}$?>
</jats:tex-math>
<jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="apjaab8f5ieqn6.gif" xlink:type="simple" />
</jats:inline-formula> erg. The results from our radio follow-up and multiwavelength modeling lend credence to the hypothesis that detected high-redshift GRBs may be more tightly beamed than events at lower redshift. We do not find compelling evidence for reverse shock emission, which may be related to fast cooling driven by the moderately high circumburst density.</jats:p>

• 出版日期2018-5-1
• 单位西北大学