We present an analysis of data from both the Röntgen Satellite (ROSAT) and the Advanced Satellite for Cosmology and Astrophysics (ASCA) of the supernova remnant G18.95À1.1. We find that the X-ray emission from G18.95À1.1 is predominantly thermal, heavily absorbed with a column density around 10 22 atoms cm À2 , and can be best described by an nonequilibrium ionization (NEI) model with a temperature around 0.9 keV and an ionization timescale of 1:1 Â 10 10 cm À3 s À1. We find only marginal evidence for nonsolar abundances. Comparisons between 21 cm H i absorption data and derived parameters from our spectral analysis strongly suggest a relatively nearby remnant (a distance of about 2 kpc). Above 4 keV, we identify a small region of emission located at the tip of the central, flat-spectrum barlike feature in the radio image. We examine two possibilities for this emission region: a temperature variation within the remnant or a pulsar wind nebula (PWN). The current data do not allow us to distinguish between these possible explanations. In the scenario where this high-energy emission region corresponds to a PWN, our analysis suggests a rotational loss rate for the unseen pulsar of about 7 Â 10 35 ergs s À1 and a ratio L r /L X of about 3.6 for the entire PWN, slightly above the maximum ratio (3.4 for Vela) measured in known PWNe. Subject headings: ISM: abundances-ISM: individual (G18.95À1.1)-supernova remnants-X-rays: ISM
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