2001/02/14 by Christopher L. Gerardy, C. L. Gerardy, Robert A. Fesen +1 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #astro-ph
paper · pdf · doi:10.1086/320393
17 Pages, 10 Figures to be published in The Astronomical Journal
arxiv created 2001/02/14 · openalex publication_date 2001/05/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
Near-infrared spectra (0.95–2.4 μm) of the Cassiopeia A and Kepler supernova remnants (SNRs) are presented. Low-dispersion ( R ≈ 700) spectra were obtained for five bright fast-moving ejecta knots (FMKs) at two locations on the main shell and for three bright circumstellar knots (quasi-stellar flocculi or QSFs) near the southwest rim of Cas A. The main shell FMKs in Cas A exhibit a sparse near-infrared spectrum dominated by [S II] 1.03 μm emission with a handful of other, fainter emission lines. Among these are two high-ionization silicon lines, [Si VI] 1.96 and [Si X] 1.43 μm, which have been detected in active galactic nuclei and novae but never before in a supernova remnant. The near-infrared spectra of circumstellar QSFs in Cas A show a much richer spectrum, with strong He I 1.083 μm emission and over a dozen bright [Fe II] lines. Observed [Fe II] line ratios indicate electron densities of 5–9 × 10 4 cm -3 in the QSFs. The Cas A QSF data are quite similar to the observed spectrum of a bright circumstellar knot along the northwest rim of the Kepler SNR, which also shows strong He I and [Fe II] emission with a measured electron density of 2.5–3 × 10 4 cm -3 . Finally, we present J - and K -band images of Cas A. The K -band image shows faint diffuse emission that has no optical or midinfrared counterpart but is morphologically similar to radio continuum maps and may be infrared synchrotron radiation.