ASCA discovered an extended source in the Scutum constellation .
The X-ray morphology is an elliptical shape elongated from north to south with a mean diameter of about 10 ^ { \prime } .
The image center is located at RA _ { 2000 } = \timeform 18h43m53s , DEC _ { 2000 } = - \timeform { 03 D 52 ^ { \prime } 55 ^ { \prime \prime } } ( 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 ) .
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 ) \times~ { } 10 ^ { 22 } cm ^ { -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 \sim 20 pc and \sim~ { } 3 ~ { } \times~ { } 10 ^ { 34 } 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 \sim 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 .