A diffuse X-ray source, AX J1843.8-0352: Association with the radio complex G28.6-0.1 and identification of a new supernova remnant

Abstract

ASCA discovered an extended source in the constellation Scutum. The X-ray morphology is an elliptical shape elongated from north to south with a mean diameter of about 10′. The image center is located at RA2000 = 18h43m53s, DEC2000 = -03°52′55″ (hereafter, AX J1843.8-0352). The north and south rims of AX J1843.8-0352 are associated with non-thermal radio sources C and F of the G28.6-0.1 complex (Helfand et al. 1989, AAA 49.125.029). The X-ray spectrum was fitted with a model of either a thin thermal plasma in non-equilibrium ionization of a temperature 5.4 keV or a power-law of photon index 2.1. The absorption column is (2.4-4.0) × 1022cm-2, which probably places this source in the Scutum arm. With a reasonable distance assumption of about 7 kpc, we estimate the mean diameter and X-ray luminosity to be ∼ 20 pc and ∼ 3 × 1034 erg s-1, respectively. Although a Sedov solution for a thin thermal plasma model gives parameters of a young shell-like SNR, no strong emission lines are found with the metal abundances being ∼ solar. Thus, a more likely scenario for both the radio and X-ray spectra and the morphologies is that AX J1843.8-0352 is a shell-like SNR which predominantly emits synchrotron X-rays.