A search for thermally emitting isolated neutron stars in the 2XMMp catalogue

Abstract

The relatively large number of nearby radio-quiet and thermally emitting isolated neutron stars (INSs) discovered in the ROSAT All-Sky Survey, dubbed the ``Magnificent Seven'' (M7), suggests that they belong to a formerly neglected major component of the overall INS population. So far, attempts to discover similar INSs beyond the solar vicinity failed to confirm any reliable candidate. The EPIC cameras onboard the XMM-Newton satellite allow to efficiently search for new thermally emitting INSs. We used the 2XMMp catalogue to select sources with no catalogued candidate counterparts and with X-ray spectra similar to those of the M7, but seen at greater distances and thus undergoing higher interstellar absorptions. Identifications in more than 170 astronomical catalogues and visual screening allowed to select fewer than 30 good INS candidates. In order to rule out alternative identifications, we obtained deep ESO-VLT and SOAR optical imaging for the X-ray brightest candidates. We report here on the optical follow-up results of our search and discuss the possible nature of 8 of our candidates. A high X-ray-to-optical flux ratio together with a stable flux and soft X-ray spectrum make the brightest source of our sample, 2XMM J104608.7-594306, a newly discovered thermally emitting INS. The X-ray source 2XMM J010642.3+005032 has no evident optical counterpart and should be further investigated. The remaining X-ray sources are most probably identified with CVs and AGN, as inferred from the colours and flux ratios of their likely optical counterparts. Beyond the finding of new thermally emitting INSs, our study aims at constraining the space density of this Galactic population at great distances and at determining whether their apparently high density is a local anomaly or not.

13 pages, 5 figures, accepted for publication in A&A

References in corpus (16)

• The XMM-Newton Serendipitous Survey. V. The Second XMM-Newton Serendipitous Source Catalogue
• The Magnificent Seven: Magnetic fields and surface temperature distributions
• Isolated neutron stars: Magnetic fields, distances, and spectra
• Population synthesis of radio and gamma-ray millisecond pulsars from the Galactic disk
• High precision X-ray logN-logS distributions: implications for the obscured AGN population
• The XMM-Newton Serendipitous Survey V. Optical identification of the XMM-Newton Medium sensitivity Survey (XMS)
• A Census of the Carina Nebula -- II. Energy Budget and Global Properties of the Nebulosity
• Discovery of Pulsations and a Possible Spectral Feature in the X-ray Emission from Rotating Radio Transient J1819-1458
• The Magnificent Seven in the dusty prairie -- The role of interstellar absorption on the observed neutron star population
• A tale of two populations: Rotating Radio Transients and X-ray Dim Isolated Neutron Stars
• Discovery of an Isolated Compact Object at High Galactic Latitude
• Proper motions of thermally emitting isolated neutron stars measured with Chandra
• The isolated neutron star candidate 2XMM J104608.7-594306
• Proper motions of ROSAT discovered isolated neutron stars measured with Chandra: First X-ray measurement of the large proper motion of RX J1308.6+2127/RBS 1223
• Persistent and Transient Blank Field Sources
• Accretion by Isolated Neutron Stars

Cited by in corpus (13)

• Further Searches for RRATs in the Parkes Multi-Beam Pulsar Survey
• The XMM-Newton SSC survey of the Galactic Plane
• An X-Ray-dim "Isolated'' Neutron Star in a Binary?
• New XMM-Newton observation of the thermally emitting isolated neutron star 2XMM J104608.7-594306
• The peculiar isolated neutron star in the Carina Nebula - Deep XMM-Newton and ESO-VLT observations of 2XMM J104608.7-594306
• Follow-up of isolated neutron star candidates from the eROSITA survey
• Candidate isolated neutron stars in the 4XMM-DR10 catalog of X-ray sources
• Discovery of two promising isolated neutron star candidates in the SRG/eROSITA All-Sky Survey
• No Confirmed New Isolated Neutron Stars In The SDSS Data Release 4
• XMM-Newton and SRG/eROSITA observations of the isolated neutron star candidate 4XMM J022141.5-735632
• Towards an X-ray inventory of nearby neutron stars
• Statistical ages and the cooling rate of X-ray dim isolated neutron stars
• Isolated neutron stars as Science Validation for XMM2ATHENA: Ensuring robust data for future X-ray Astronomy