NICER observation list: Target ID 564103

eROSITA is performing multiple all-sky X-ray surveys and monitoring almost half a million AGN every six months. It has the capability to identify exceptional AGN with periodic X-ray flux signals. These objects are potential supermassive black hole binaries (SMBHB). We request ToO monitoring campaigns for up to three eROSITA-selected candidate periodic AGN. Each ToO consists of six individual pointings, 10 ks each, spaced roughly four weeks apart. The campaigns are needed to track the flux modulation waveform on a monthly time-scale, accurately determine the period, and to determine the details of follow-up observations to confirm the binary nature. The most convincing case will be the target of a pre-approved 100 ks XMM-Newton observation.