GeminiFocus 2013 Year in Review | Page 38

Figure 12. presence of high-velocity 56Ni in the northern region of the supernova. Difference image shows SN1987A light echoes as positive and negative (bright and dark) circular rings. They appear uniformly circular because the echo is reflected off sheet-like dust structures. Black boxes mark the GMOS fields, and red points show the spectral locations. Most theoretical models of supernovae require some asymmetry to explode successfully, and observations such as these obtained with Gemini South of SN1987A can better constrain the simulations. The complete results will be published in The Astrophysical Journal, Volume 767. A link is also now available: http://iopscience.iop.org/0004-637X/767/1/45 tribution but also on the exact region observed. The echo spectra must be compared to an appropriate isotropic source model, which is based on the original SN1987A outburst observations. The well-known source spectrum (SN1987A) is advantageous, then, because it provides an excellent reference for isotropic emission scenarios. The Ha line shows some of the strongest deviations from the isotropic assumption (Figure 13). Two particularly interesting examples come from opposite sides of the e