The Evolution of Late-Time Optical Emission from SN 1986J

• Published in: The Astrophysical journal Vol. 684; no. 2; pp. 1170 - 1173
• Main Authors: Milisavljevic, Dan, Fesen, Robert A, Leibundgut, Bruno, Kirshner, Robert P
• Format: Journal Article
• Language: English
• Published: Chicago, IL IOP Publishing 10.09.2008; University of Chicago Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Circumstellar matter; Supernova remnants; Light emission; supemovae: general
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/590426

We present late-time optical images and spectra of the Type IIn supernova SN 1986J. HST ACS/WFC images obtained in 2003 February show it to be still relatively bright, with m sub(F606W) = 21.4 and m sub(F814W) = 20.0 mag. Compared to 1994 December HST WFPC2 images, SN 1986J shows a decline of only [image]1 mag in brightness over 8 years. Ground-based spectra taken in 1989, 1991, and 2007 show a 50% decline in H alpha emission between 1989 and 1991, and an order of magnitude drop between 1991 and 2007, along with the disappearance of He i line emissions during the period 1991-2007. The object's [O i] [lambda][lambda]6300, 6364, [O ii] [lambda][lambda]7319, 7330 and [O iii] [lambda][lambda]4959, 5007 emission lines show two prominent peaks near -1000 and -3500 km s super(-1), with the more blueshifted component declining significantly in strength between 1991 and 2007. The observed spectral evolution suggests two different origins for SN 1986J's late-time optical emission: dense, shock-heated circumstellar material, which gave rise to the initially bright H alpha , He i, and [N ii] [lambda]5755 lines, and reverse-shock-heated O-rich ejecta on the facing expanding hemisphere, dominated by two large clumps generating two blueshifted emission peaks in the [O i], [O ii], and [O iii] lines.