The polarized Gamma-Ray Burst GRB 061122

TL;DR

This paper reports on polarization measurements of GRB 061122's prompt emission, constrains the host galaxy's properties, and sets new limits on Lorentz Invariance Violation, advancing understanding of gamma-ray bursts and fundamental physics.

Contribution

It provides the first polarization measurement of GRB 061122 and constrains quantum gravity effects through Lorentz Invariance Violation limits.

Findings

Polarization fraction >60% at 68% c.l. in 250-800 keV range.

Host galaxy redshift constrained to [0.57, 2.10], best estimate z=1.33.

Stringent limit on Lorentz Invariance Violation parameter xi < 3.4x10^-16.

Abstract

We report on the polarization measure, obtained with IBIS on board INTEGRAL, of the prompt emission of GRB 061122. Over an 8 s interval containing the brightest part of the Gamma-Ray Burst we put a lower limit on its polarization fraction of 60% at 68% c.l. and of 33% at 90% c.l. on the 250-800 keV energy range. We performed late time optical and near infra-red imaging observations of the GRB field using the Telescopio Nazionale Galileo (TNG), and the Canada-France-Hawaii Telescope (CFHT). Our multi-band (ugrizYJHK) photometry allowed us to identify the host galaxy of GRB 061122 and to build its SED. Using a photometric redshift code we fitted these data, and derived the basic properties of the galaxy, including its type and redshift, that we could constrain to the interval [0.57, 2.10] at a 90% c.l., with a best fit value of z=1.33. The polarization measurement in different energy bands, together with the distance determination, allowed us to put the most stringent limit (xi < 3.4x10-16) to date to a possible Lorentz Invariance Violation based on the vacuum birefringence effect, predicted by some quantum-gravity theories.