We report an X-ray study of the evolved Galactic supernova remnant ( SNR ) G156.2+5.7 based on six pointing observations with Suzaku .
The remnant ’ s large extent ( 100 \arcmin in diameter ) allows us to investigate its radial structure in the northwestern and eastern directions from the apparent center .
The X-ray spectra were well fit with a two-component non-equilibrium ionization model representing the swept-up interstellar medium ( ISM ) and the metal-rich ejecta .
We found prominent central concentrations of Si , S and Fe from the ejecta component ; the lighter elements of O , Ne and Mg were distributed more uniformly .
The temperature of the ISM component suggests a slow shock ( 610-960 km s ^ { -1 } ) , hence the remnant ’ s age is estimated to be 7,000-15,000 yr , assuming its distance to be \sim 1.1 kpc .
G156.2+5.7 has also been thought to emit hard , non-thermal X-rays , despite being considerably older than any other such remnant .
In response to a recent discovery of a background cluster of galaxies ( 2XMM J045637.2+522411 ) , we carefully excluded its contribution , and reexamined the origin of the hard X-ray emission .
We found that the residual hard X-ray emission is consistent with the expected level of the cosmic X-ray background .
Thus , no robust evidence for the non-thermal emission was obtained from G156.2+5.7 .
These results are consistent with the picture of an evolved SNR .