Detection of Reflection Features in the Neutron Star Low-Mass X-ray Binary Serpens X-1 with NICER

Understand

We present Neutron Star Interior Composition Explorer (NICER) observations of the neutron star low-mass X-ray binary Serpens X-1 during the early mission phase in 2017.

• With the high spectral sensitivity and low-energy X-ray passband of NICER, we are able to detect the Fe L line complex in addition to the signature broad, asymmetric Fe K line.
• We confirm the presence of these lines by comparing the NICER data to archival observations with XMM-Newton/RGS and NuSTAR.
• Both features originate close to the innermost stable circular orbit (ISCO).