The Astrophysical Journal
Department of Physics and Astronomy
We present results from observations of supernova (SN) 1979C with the Newton X-Ray Multi-Mirror (XMM-Newton) mission in X-rays and in UV, archival X-ray, and Hubble Space Telescope (HST) data, and follow-up ground-based optical imaging. The XMM-Newton MOS spectrum shows the best-fit two-temperature thermal plasma emission characteristics of both the forward (kThigh = 4.1 keV) and reverse shock (kTlow = 0.79 keV) with no intrinsic absorption. The long-term X-ray light curve, constructed from all X-ray data available, reveals that SN 1979C is still radiating at a flux level similar to that detected by ROSAT in 1995, showing no sign of a decline over the last 6 years, some 16-23 yr after its outburst. The high inferred X-ray luminosity (L0.3-2 = 8 × 1038 ergs s-1) is caused by the interaction of the SN shock with dense circumstellar matter, likely deposited by a strong stellar wind from the progenitor with a high mass-loss rate of ≈ 1.5 × 10-4 M☉ yr-1 (vw/10 km s-1). The X-ray data support a strongly decelerated shock and show a mass-loss rate history that is consistent with a constant progenitor mass-loss rate and wind velocity over the past 16,000 yr in the stellar evolution of the progenitor. We find a best-fit circumstellar medium (CSM) density profile of ρCSM ∝ r-s with index s 1.7 and high CSM densities (104 cm-3) out to large radii from the site of the explosion (r 4 × 1017 cm). Using XMM-Newton Optical Monitor data, we further detect a pointlike optical/UV source consistent with the position of SN 1979C, with B-, U-, and UVW1-band luminosities of 5, 7, and 9 × 1036 ergs s-1, respectively. The young stellar cluster in the vicinity of the SN, as imaged by the HST and follow-up ground-based optical imaging, can only provide a fraction of the total observed flux, so that a significant contribution to the output likely arises from the strong interaction of SN 1979C with dense CSM.
Stefan Immler et al 2005 ApJ 632 283
Dartmouth Digital Commons Citation
Immler, Stefan; Fesen, Robert A.; Van Dyk, Schuyler D.; Weiler, Kurt W.; Petre, Robert; Lewin, Walter H.G; Pooley, David; Pietsch, Wolfgang; Aschenbach, Bernd; Hammell, Molly C.; and Rudie, Gwen C., "Late‐Time X‐Ray, UV, and Optical Monitoring of Supernova 1979C" (2005). Dartmouth Scholarship. 2887.