Details

Autor(en) / Beteiligte

• Buckley, D A H
• Bagnulo, S
• Britto, R J
• Mao, J
• Kann, D A
• Cooper, J
• Lipunov, V
• Hewitt, D M
• Razzaque, S
• Kuin, N P M
• Monageng, I M
• Covino, S
• Jakobsson, P
• van der Horst, A J
• Wiersema, K
• Böttcher, M
• Campana, S
• D’Elia, V
• Gorbovskoy, E S
• Gorbunov, I
• Groenewald, D N
• Hartmann, D H
• Kornilov, V G
• Mundell, C G
• Podesta, R
• Thomas, J K
• Tyurina, N
• Vlasenko, D
• van Soelen, B
• Xu, D

Titel

Spectropolarimetry and photometry of the early afterglow of the gamma-ray burst GRB 191221B

Ist Teil von

• Monthly notices of the Royal Astronomical Society, 2021-08, Vol.506 (3), p.4621-4631

Ort / Verlag

Oxford University Press

Erscheinungsjahr

2021

Quelle

Free E-Journal (出版社公開部分のみ）

Beschreibungen/Notizen

• ABSTRACT We report on results of spectropolarimetry of the afterglow of the long gamma-ray burst GRB 191221B, obtained with SALT/RSS and VLT/FORS2, as well as photometry from two telescopes in the MASTER Global Robotic Network, at the MASTER-SAAO (South Africa) and MASTER-OAFA (Argentina) stations. Prompt optical emission was detected by MASTER-SAAO 38 s after the alert, which dimmed from a magnitude (white-light) of ∼10–16.2 mag over a period of ∼10 ks, followed by a plateau phase lasting ∼10 ks and then a decline to ∼18 mag after 80 ks. The light curve shows complex structure, with four or five distinct breaks in the power-law decline rate. SALT/RSS linear spectropolarimetry of the afterglow began ∼2.9 h after the burst, during the early part of the plateau phase of the light curve. Absorption lines seen at ∼6010 and 5490 Å are identified with the Mg ii 2799 Å line from the host galaxy at z = 1.15 and an intervening system located at z = 0.96. The mean linear polarization measured over 3400–8000 Å was ∼1.5 per cent and the mean equatorial position angle (θ) was ∼65°. VLT/FORS2 spectropolarimetry was obtained ∼10 h post-burst, during a period of slow decline (α = −0.44), and the polarization was measured to be p = 1.2 per cent and θ = 60°. Two observations with the MeerKAT radio telescope, taken 30 and 444 d after the GRB trigger, detected radio emission from the host galaxy only. We interpret the light curve and polarization of this long GRB in terms of a slow-cooling forward shock.