What is GRB 970228?
{{Infobox astronomical event | ra = {{RA|05|01|46.7}} | dec = {{DEC|+11|46|53.0}} | epoch = J2000 | energy = {{val|5.2|e=44|ul=J}} }} '''GRB 970228''' was a [[gamma-ray burst]] (GRB). It was the first GRB which had an [[Afterglow (gamma-ray burst)|afterglow]]. It was seen on 28 February 1997. Since 1993, scientists had predicted GRBs to be followed by afterglows. But, until this event, GRBs had only been seen in very [[luminosity|bright]] bursts of high-energy [[gamma ray]]s. The burst had several peaks in its [[light curve]]. It lasted around 80 seconds. The light curve was not normal. This suggested that a [[supernova]] may have happened as well. GRB 970228 happened in the same place as a galaxy about 8.1 billion [[light-year]]s away. This means that GRBs happen outside the [[Milky Way]]. == Cause == Reichart showed that the light curve of GRB 970228 could only have been caused by a supernova.<ref>Reichart, Daniel E. 2001. Light curves and spectra of dust echoes from gamma-ray bursts and their afterglows: continued evidence that GRB 970228 is associated with a supernova. ''Astrophysical Journal'' '''554''' (2): 649–659. [http://iopscience.iop.org/0004-637X/554/2/643/]</ref> Definitive evidence linking gamma-ray bursts and supernovae was eventually found in the spectrum of [[GRB 020813]],<ref>Butler, Nathaniel R. ''et al'' 2003. The X-ray afterglows of GRB 020813 and GRB 021004 with Chandra HETGS: possible evidence for a supernova prior to GRB 020813. ''Astrophysical Journal'' '''597''' (2): 1010–1016. [http://iopscience.iop.org/0004-637X/597/2/1010/]</ref> and the afterglow of [[GRB 030329]].<ref>Stanek, Krzysztof Z. ''et al'' 2003. Spectroscopic discovery of the supernova 2003dh associated with GRB0303291. ''Astrophysical Journal'' '''591''' (1): L17–L20. [https://arxiv.org/abs/astro-ph/0304173]</ref> However, supernova-like features only become apparent in the weeks following a burst, leaving the possibility that very early luminosity variations could be explained by dust echoes.<ref> Moran, Jane A. and Rei