Soft X-ray observing the cosmic sources by the ESA–CAS satellite SMILE

This paper describes the scientific potential of a Soft X-ray Imager (SXI) onboard the ESA–CAS satellite SMILE for investigating cosmic X-ray sources of various types. We show that this instrument, albeit designed for X-ray imaging of solar wind Charge eXchange of the magnetosheath and the cusps, is also essential for astrophysics because it is able to provide wide-field imaging of the sky in the soft X-ray region. Regarding sufficiently luminous X-ray sources with continuous spectra to be observable by the X-ray monitor MAXI/ISS to assess the object types and their light curves that are expected to be detected by SXI/SMILE, the compact sources accreting matter are promising targets for evaluating the possibilities of SXI. We assumed only the cosmic objects located in the planned fields to be observed by SXI. We used the 2–3 keV band flux of MAXI/ISS covering at least part of the expected band of the SXI/SMILE telescope. We used the data obtained by MAXI/ISS to assess the object types and their light curves expected to be detected by SXI/SMILE. We show the long-term activity of the examples of X-ray binary types located in this region. We present the typical features of such objects' activity on long timescales (e.g., outbursts and state transitions) and include physical interpretations of these phenomena. Furthermore, we discuss how SXI can contribute to this branch.