NICER observation list: Target ID 255201

We propose a NICER observing sequence to determine a timing solution for the isolated neutron star RX J0806.4-4123. The previous XMM-Newton observations yielded a frequency derivative with a large uncertainty that is consistent with spin-up of the neutron star. A better constrained timing solution is needed because recent near-infrared observations discovered an extended source at the position of the neutron star which could indicate a circumpulsar disk. The proposed observations will allow us to test whether RX J0806.4-4123 has timing properties different from those of its siblings, the other six of the so-called Magnificent Seven.