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Early detection of the Optical Transient following the Gamma-Ray Burst GRB 970228

A. Guarnieri·C. Bartolini·N. Masetti·A. Piccioni·E. Costa·M. Feroci·F. Frontera·D. Dal Fiume·L. Nicastro·E. Palazzi·A. J. Castro-Tirado·J. Gorosabel
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Abstract

The optical counterpart of the Gamma-Ray Burst GRB 970228, discovered by Groot et al. (IAU Circ. 6584), is also detected in the B and R frames obtained about 4 hours earlier at the Bologna Observatory. Our observations indicate a very likely rise of the optical emission within these 4 hours. The R luminosity of the transient at maximum was about 15 times that of an underlying extended object. Follow-up data show that the maximum optical emission was delayed of not less than 0.7 days with respect to the gamma-ray peak and that no new big flares were seen after the main one. The optical transient became significantly redder once it has reverted to quiescence.

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A. Guarnieri, C. Bartolini, N. Masetti, A. Piccioni, E. Costa, M. Feroci, F. Frontera, D. Dal Fiume, L. Nicastro, E. Palazzi, A. J. Castro-Tirado, J. Gorosabel. 1997-07-15. Early detection of the Optical Transient following the Gamma-Ray Burst GRB 970228. https://arxiv.org/abs/astro-ph/9707164

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