6533b829fe1ef96bd128a406
RESEARCH PRODUCT
Neutron Star Radius-to-mass Ratio from Partial Accretion Disk Occultation as Measured through Fe Kα Line Profiles
Vittorio De FalcoRiccardo La PlacaRiccardo La PlacaRiccardo La PlacaMaurizio FalangaTiziana Di SalvoLuigi StellaAlessandra De RosaA. PapittoPavel Bakalasubject
PhysicsAstrophysics::High Energy Astrophysical PhenomenaNeutron starAstronomy and AstrophysicsRadiusAstrophysicsMass ratioX-ray sourcesOccultationNeutron starLow-mass x-ray binary starSettore FIS/05 - Astronomia E AstrofisicaAccretion discGeneral relativitySpace and Planetary ScienceAstrophysics::Earth and Planetary AstrophysicsAstrophysics - High Energy Astrophysical PhenomenaStellar accretion diskLine (formation)description
We present a new method to measure the radius-to-mass ratio (R/M) of weakly magnetic, disc-accreting neutron stars by exploiting the occultation of parts of the inner disc by the star itself. This occultation imprints characteristic features on the X-ray line profile that are unique and are expected to be present in low mass X-ray binary systems seen under inclinations higher than ~65 degrees. We analyse a NuSTAR observation of a good candidate system, 4U 1636-53, and find that X-ray spectra from current instrumentation are unlikely to single out the occultation features owing to insufficient signal-to-noise. Based on an extensive set of simulations we show that large-area X-ray detectors of the future generation could measure R/M to ~2{\div}3% precision over a range of inclinations. Such is the precision in radius determination required to derive tight constraints on the equation of state of ultradense matter and it represents the goal that other methods too aim to achieve in the future.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2020-04-23 |