TY - JOUR
T1 - Polarimetry and Photometry of Gamma-Ray Bursts with RINGO2
AU - Steele, I. A.
AU - Kopac, D.
AU - Arnold, D. M.
AU - Smith, R. J.
AU - Kobayashi, S.
AU - Jermak, H. E.
AU - Mundell, C. G.
AU - Gomboc, A.
AU - Guidorzi, C.
AU - Melandri, A.
AU - Japelj, J.
PY - 2017/7/14
Y1 - 2017/7/14
N2 - We present a catalog of early-time (~10^2-10^4s) photometry and polarimetry of all Gamma-Ray Burst (GRB) optical afterglows observed with RINGO2 imaging polarimeter on the Liverpool Telescope. For the 19 optical afterglows observed, the following 9 were bright enough to perform photometry and attempt polarimetry: GRB 100805A, GRB 101112A, GRB 110205A, GRB 110726A, GRB 120119A, GRB 120308A, GRB 120311A, GRB 120326A and GRB 120327A. We present multi-wavelength light curves for these 9 GRBs, together with estimates of their optical polarization degrees and/or limits. We carry out a thorough investigation of detection probabilities, instrumental properties and systematics. Using two independent methods, we confirm previous reports of significant polarization in GRB 110205A and 120308A, and report new detection of $P=6^{+3}_{-2}\%$ in GRB101112A. We discuss the results for the sample in the context of the reverse and forward shock afterglow scenario, and show that GRBs with detectable optical polarization at early time have clearly identifiable signatures of reverse-shock emission in their optical light curves. This supports the idea that GRB ejecta contain large-scale magnetic fields and highlights the importance of rapid-response polarimetry.
AB - We present a catalog of early-time (~10^2-10^4s) photometry and polarimetry of all Gamma-Ray Burst (GRB) optical afterglows observed with RINGO2 imaging polarimeter on the Liverpool Telescope. For the 19 optical afterglows observed, the following 9 were bright enough to perform photometry and attempt polarimetry: GRB 100805A, GRB 101112A, GRB 110205A, GRB 110726A, GRB 120119A, GRB 120308A, GRB 120311A, GRB 120326A and GRB 120327A. We present multi-wavelength light curves for these 9 GRBs, together with estimates of their optical polarization degrees and/or limits. We carry out a thorough investigation of detection probabilities, instrumental properties and systematics. Using two independent methods, we confirm previous reports of significant polarization in GRB 110205A and 120308A, and report new detection of $P=6^{+3}_{-2}\%$ in GRB101112A. We discuss the results for the sample in the context of the reverse and forward shock afterglow scenario, and show that GRBs with detectable optical polarization at early time have clearly identifiable signatures of reverse-shock emission in their optical light curves. This supports the idea that GRB ejecta contain large-scale magnetic fields and highlights the importance of rapid-response polarimetry.
KW - astro-ph.HE
UR - https://doi.org/10.3847/1538-4357/aa79a2
U2 - 10.3847/1538-4357/aa79a2
DO - 10.3847/1538-4357/aa79a2
M3 - Article
SN - 0004-637X
VL - 843
SP - 143
EP - 158
JO - Astrophysical Journal
JF - Astrophysical Journal
ER -