No confirmed new isolated neutron stars in the SDSS data release 4

Marcel A. Agüeros, Bettina Posselt, Scott F. Anderson, Philip Rosenfield, Frank Haberl, Lee Homer, Bruce Margon, Emily R. Newsom, Wolfgang Voges

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7 Scopus citations


We report on follow-up observations of candidate X-ray-bright, radio-quiet isolated neutron stars (INSs) identified from correlations of the ROSAT All-Sky Survey (RASS) and the Sloan Digital Sky Survey (SDSS) Data Release 4 in Agüeros etal. We obtained Chandra X-ray Observatory exposures for 13 candidates in order to pinpoint the source of X-ray emission in optically blank RASS error circles. These observations eliminated 12 targets as good INS candidates. We discuss subsequent observations of the remaining candidate with XMM-Newton, the Gemini North Observatory, and the Apache Point Observatory. We identify this object as a likely extragalactic source with an unusually high log (f X/f opt) ∼ 2.4. We also use an updated version of the population synthesis models of Popov etal. to estimate the number of RASS-detected INSs in the SDSS Data Release 7 footprint. We find that these models predict ∼ 3-4 INSs in the 11,000deg2 imaged by SDSS, which is consistent with the number of known INSs that fall within the survey footprint. In addition, our analysis of the four new INS candidates identified in the SDSS footprint implies that they are unlikely to be confirmed as INSs; together, these results suggest that new INSs are not likely to be found from further correlations of the RASS and SDSS.

Original languageEnglish (US)
Article number176
JournalAstronomical Journal
Issue number6
StatePublished - Jun 2011

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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