2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/15191We report the discovery of a new isolated neutron star candidate, RX J0420.0-5022, showing evidence (4 sigma) for 22.7 s X-ray pulsations in ROSAT data. NTT observations of the field around the soft X-ray source do not reveal any likely optical counterpart brighter than B = 25.25 implying an X-ray to optical flux ratio of >10^3.3 and ruling out other possible kinds of X-ray emitters. The X-ray spectrum of RX J0420.0-5022 can be described with blackbody emission with temperature kT of about 57 eV and four ROSAT detections are consistent with no flux variations on time scales of years. The X-ray pulsations, if confirmed, make RX J0420.0-5022 the second long-period isolated neutron star candidate after RX J0720.4-3125. As for this latter source similar conclusions about the magnetic field strength of the neutron star can be drawn depending on evolutionary scenarios.5 pages, LaTex, 5 figures, Accepted for publication in A&A LettersAstrophysicstext