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RX J0420.0-5022: An isolated neutron star candidate with evidence for 22.7 s X-ray pulsations

F. Haberl·W. Pietsch·C. Motch
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Abstract

We 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.

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F. Haberl, W. Pietsch, C. Motch. 1999-11-10. RX J0420.0-5022: An isolated neutron star candidate with evidence for 22.7 s X-ray pulsations. https://arxiv.org/abs/astro-ph/9911159

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