{'fraction_non_alphanumeric': 0.026573426573426574, 'fraction_numerical': 0.04265734265734266, 'mean_word_length': 4.021052631578947, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
N ov 2 00 2 submitted to AJ Optical Photometry of GRB 021004 : The First Month 1

We present UBVRCIC photometry of the optical afterglow of the gamma-ray burst GRB 021004 taken at the Nordic Optical Telescope between approximately eight hours and 30 days after the burst. This data is combined with an analysis of the Chandra X-ray observations of GRB 021004 taken approximately 33 hours after the burst to investigate the nature of the burst. We find an intrinsic optical spectral slope of βO = 0.39 ± 0.12 and an X-ray slope of βX = 0.93 ± 0.03. There is no evidence for color evolution between 8.5 hours and 5.5 days after the burst. Our data suggest that the extinction within the host along the line of sight to the burst is AV = 0.26 and that the host galaxy has an SMC extinction law. The optical and X-ray data are consistent with a relativistic fireball with the shocked electrons being in the slow cooling regime and an electron index of p = 1.9±0.1. The burst occurred in an ambient medium that is homogeneous on scales larger than ≈ 10 cm with a mean particle density no greater than ≈ 60 cm. Our results support the idea that the brightening seen at ≈ 0.1 days was due to interaction with a clumpy ambient medium within 10–10 cm of the progenitor. There is evidence that a jet break occurred gradually at ≈ 6 days after the burst and that the jet is undergoing sideways expansion. Subject headings: gamma rays: bursts