Letter to the Editor

GRB 030227: The first multiwavelength afterglow of an INTEGRAL GRB ^*

¹ Instituto de Astrofísica de Andalucía (IAA-CSIC), Apartado de Correos, 3004, 18080 Granada, Spain
² Space Telescope Science Institute, 3700 San Martín Drive, Baltimore MD 21218, USA
³ Department of Physical Sciences, University of Hertfordshire, College Lane, Hatfield, Herts AL10 9AB, UK
⁴ Istituto di Astrofisica Spaziale e Fisica Cosmica, Sez. di Milano “G. Occhialini” – CNR v. Bassini 15, 20133 Milano, Italy
⁵ Joint Astronomy Centre, 660 N, A' ohoku Place, Hilo, HI 96720, USA
⁶ State Observatory, Manora Peak, Naini Tal 263129, Uttaranchal, India
⁷ Istituto di Astrofisica Spaziale e Fisica Cosmica – Sezione di Bologna, via Gobetti 101, 40129 Bologna, Italy
⁸ Istituto di Radioastronomia, sezione di Firenze, CNR, Largo E. Fermi 5, 50125, Firenze, Italy
⁹ Lund Observatory, Sölvegatan 27, PO Box 43, 221 00 Lund, Sweden
¹⁰ Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø , Denmark
¹¹ University Observatory Munich, Scheinerstr. 1, 81679 Munich, Germany
¹² Special Astrophysical Observatory of RAS, Karachai-Cherkessia, 369167, Nizhnij Arkhyz, Russia
¹³ Danish Space Research Institute, Juliane Maries Vej 30, 2100 Copenhagen Ø , Denmark.
¹⁴ Grupo de Astrofísica y Ciencias del Espacio, Universidad de Valencia, Apdo. 2085, 46071 Burjassot (Valencia), Spain
¹⁵ European Space Agency, Research Science Division, Noorwijk, The Netherlands
¹⁶ Thüringer Landessternwarte Tautenburg, 07778 Tautenburg, Germany
¹⁷ Max Planck Institut für extraterrestrische Physik, Giessenbachstr., PF 1312, 85741 Garching, Germany
¹⁸ University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
¹⁹ Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy
²⁰ Astrophysikalisches Institut, An der Sternwarte 16, 14482 Potsdam, Germany
²¹ Department of Physics and Astronomy, Aarhus University, Ny Munkegade, 8000 Aarhus C, Denmark
²² NASA/MSFC, NSSTC, SD-50, 320 Sparkman Drive, Huntsville, AL 35805, USA
²³ European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Santiago 19, Chile

Corresponding author: A. J. Castro-Tirado, ajct@iaa.es

Received: 14 July 2003
Accepted: 10 September 2003

Abstract

We present multiwavelength observations of a gamma-ray burst detected by INTEGRAL (GRB 030227) between 5.3 hours and ~1.7 days after the event. Here we report the discovery of a dim optical afterglow (OA) that would not have been detected by many previous searches due to its faintess (). This OA was seen to decline following a power law decay with index . The spectral index yielded . These values may be explained by a relativistic expansion of a fireball (with p = 2.0) in the cooling regime. We also find evidence for inverse Compton scattering in X-rays.