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

ASCA discovered an extended source in the constellation Scutum. The X-ray m orphology is an elliptical shape elongated from north to south with a mean diameter of about 10 '. The image center is located at RA(2000) = 18(h)43(m )53(s), DEC2000 = -03 degrees 52 ' 55 " (hereafter, AX J1843.8- 0352). The north and south rims of AX J1843.8-0352 are associated with non-thermal rad io sources C and F of the G28.6-0.1 complex (Helfand et al. 1989. AAA 49.12 5.029). 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-l aw of photon index 2.1. The absorption column is (2.4-4.0) x 10(22)cm(-2), which probably places this source in the Scutum arm. With a reasonable dist ance assumption of about 7 kpc. we estimate the mean diameter and X-ray lum inosity to be similar to 20 pc and similar to 3 x 10(34) erg s(-1), respect ively. Although a Sedov solution for a thin thermal plasma model gives para meters of a young shell-like SNR, no strong emission lines are found with t he metal abundances being similar to solar. Thus, a more likely scenario fo r 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.