Letter to the Editor

Polarization evolution of the GRB 020405 afterglow^*

¹ INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate (LC), Italy
² Institute of Astronomy, University of Cambridge, Madingley Road, CB3 0HA Cambridge, UK
³ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
⁴ INAF – Osservatorio Astronomico di Roma, via Frascati 33, Monteporzio Catone (Roma), Italy
⁵ Service d'Astrophysique, CE Saclay, 91191 Gif-sur-Yvette Cedex, France
⁶ Instituto de Astronomía y Física del Espacio/CONICET, CC 67, Suc. 28, Buenos Aires, Argentina
⁷ Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguroku, Tokyo 152-8551, Japan
⁸ Center for Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139–4307, USA

Corresponding author: S. Covino, covino@merate.mi.astro.it

Received: 4 November 2002
Accepted: 28 January 2003

Abstract

Polarization measurements for the optical counterpart to GRB 020405 are presented and discussed. Our observations were performed with the VLT–UT3 (Melipal) during the second and third night after the gamma–ray burst discovery. The polarization degree (and the position angle) appears to be constant between our two observations at a level around . The polarization can be intrinsic but it is not possible to unambiguously exclude that a substantial fraction of it is induced by dust in the host galaxy.