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Abstract: The relatively large number of nearby radio-quiet and thermally emittingisolated neutron stars INSs discovered in the ROSAT All-Sky Survey, dubbedthe ``Magnificent Seven- M7, suggests that they belong to a formerlyneglected major component of the overall INS population. So far, attempts todiscover similar INSs beyond the solar vicinity failed to confirm any reliablecandidate. The EPIC cameras onboard the XMM-Newton satellite allow toefficiently search for new thermally emitting INSs. We used the 2XMMp catalogueto select sources with no catalogued candidate counterparts and with X-rayspectra similar to those of the M7, but seen at greater distances and thusundergoing higher interstellar absorptions. Identifications in more than 170astronomical catalogues and visual screening allowed to select fewer than 30good INS candidates. In order to rule out alternative identifications, weobtained deep ESO-VLT and SOAR optical imaging for the X-ray brightestcandidates. We report here on the optical follow-up results of our search anddiscuss the possible nature of 8 of our candidates. A high X-ray-to-opticalflux ratio together with a stable flux and soft X-ray spectrum make thebrightest source of our sample, 2XMM J104608.7-594306, a newly discoveredthermally emitting INS. The X-ray source 2XMM J010642.3+005032 has no evidentoptical counterpart and should be further investigated. The remaining X-raysources are most probably identified with CVs and AGN, as inferred from thecolours and flux ratios of their likely optical counterparts. Beyond thefinding of new thermally emitting INSs, our study aims at constraining thespace density of this Galactic population at great distances and at determiningwhether their apparently high density is a local anomaly or not.



Author: Adriana M. Pires 1,2, Christian Motch 1, Eduardo Janot-Pacheco 2 1 Observatoire Astronomique, Strasbourg, France, 2 IAG-USP, Braz

Source: https://arxiv.org/







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