NICER observation list: Target ID 561701

Among thermally emitting isolated neutron stars, RBS 1774 appears particularly hot in X-rays and strongly magnetised. Recent XMM-Newton and eROSITA observations reveal unexpected variations in its timing behaviour (a decrease in pulsed fraction and higher spin down), as well as evidence of multiple absorption lines and a cooler thermal component. We propose coordinated NICER observations to derive a precise timing solution and perform phase-resolved spectroscopy. These will allow us to determine the high value of spin down hinted by analysis of existing data, which places the source closer to a magnetar than any other M7 INS. The NICER campaign will likewise provide invaluable information on the geometry and orientation of the emitting region and spin-dependence of the spectral features.