Coronal emission from the shocked circumstellar ring of SN 1987A

¹ Department of Astronomy, Stockholm University, AlbaNova University Center, 106 91 Stockholm, Sweden
² Department of Astronomy, University of Virginia, PO Box 3818, Charlottesville, VA 22903, USA
³ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching, Germany e-mail: per@astro.su.se

Received: 30 March 2006
Accepted: 9 June 2006

Abstract

High resolution spectra with UVES/VLT of SN 1987A from December 2000 until November 2005 show a number of high ionization lines from gas with velocities of ~ , emerging from the shocked gas formed by the ejecta–ring collision. These include coronal lines from [Fe X], [Fe XI] and [Fe XIV] which have increased by a factor of ~ 20 during the observed period. The evolution of the lines is similar to that of the soft X-rays, indicating that they arise in the same component. The line ratios are consistent with those expected from radiative shocks with velocity , corresponding to a shock temperature of  K. A fraction of the coronal emission may, however, originate in higher velocity adiabatic shocks.