The X-ray spectrum of the supernova remnant 1E 0102.2-7219

¹ Columbia Astrophysics Laboratory, 550 West 120th Street, New York, NY 10027, USA
² University of Utrecht & Space Research Organization of The Netherlands, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

Corresponding author: A. P. Rasmussen, arasmus@astro.columbia.edu

Received: 4 October 2000
Accepted: 10 November 2000

Abstract

In this letter we present the soft X-ray (5-35 Å) spectrum of the supernova remnant (SNR) 1E 0102.2-7219 in the Small Magellanic Cloud, acquired by the reflection grating spectrometers (RGS) aboard ESA's XMM-Newton Observatory. Because the RGS features a large dispersion angle, spatial-spectral confusion is suppressed even for moderately extended () sources. Consequently, these data, along with the spectrum of N132d (Behar et al. [CITE]), provide what are probably the most detailed soft X-ray spectrum of entire SNRs. The diagnostic power of performing spectroscopy using groups of emission lines from single ions is demonstrated. In particular, the bright Lyman and helium series lines for light elements (Cvi, Ovii, Oviii, Neix & Nex) show peculiar ratios, where the values are systematically weaker than expected for electron impact excitation close to ionization equilibrium, indicating nonequilibrium ionizing (NEI) conditions in the source. The well known temperature diagnostics of helium-like triplets (Ovii & Neix) confirm this suggestion, with values that are inconsistent with ionization equilibrium. The temperatures implied are well above the maximum emission temperature for each ion, and consistent with a purely ionizing plasma. The density diagnostics meanwhile, are consistent with the low density limit, as expected.