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How Well Can We Measure Neutron Star Radii?

How Well Can We Measure Neutron Star Radii?. Cole Miller University of Maryland. Collaborators: Romain Artigue , Didier Barret , Sudip Bhattacharyya, Stratos Boutloukos , Novarah Kazmi , Fred Lamb, Ka Ho Lo. Measuring stellar radii. Ordinary star, like the Sun

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How Well Can We Measure Neutron Star Radii?

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  1. How Well Can We Measure Neutron Star Radii? Cole Miller University of Maryland Collaborators: RomainArtigue, Didier Barret, Sudip Bhattacharyya, StratosBoutloukos, Novarah Kazmi, Fred Lamb, Ka Ho Lo

  2. Measuring stellar radii • Ordinary star, like the Sun • Too far for angular resolution • But can get luminosity L • If we assume blackbody, R2=L/(4psT4) • But for NS, usually gives ~5 km! • Why? Spectral shape is ~Planck, but inefficient emission • Need good spectral models • But data usually insufficient to test

  3. Ray Tracing and Light Curves • Rapidly rotating star 300-600 Hz vsurf~0.1-0.2c SR+GR effects • Light curve informative about M, R Miller & Lamb 1998 Bogdanov+ 07, 08, 12 Many others... • Must deal carefully with degeneracies • Will now focus on our results from Lo et al., arXiv:1304.2330 Weinberg, Miller, and Lamb 2001 (synthetic data only!)

  4. High inclinations allow tight constraints on M and R Spot and observer inclinations = 90°, high background

  5. Low inclinations produce looser constraints Amplitude similar to the previous slide, but low spot and observer inclinations, low background

  6. Independent knowledge of the observer’s inclination can increase the precision spot and observer inclinations = 90°, high background Observer inclination unknown

  7. Independent knowledge of the observer’s inclination can increase the precision spot and observer inclinations = 90°, high background Observer inclination known to be 90°

  8. Incorrect modeling of the spot shapeincreases the uncertainties spot and observer inclinations = 90°, medium background Actual spot elongated E-W by 45°

  9. Phase Accumulation from GWs • aLIGO/Virgo: >=2015 • Deviation from point mass in NS-NS inspiral: accumulated tidal effects • For aLIGO, can measure tidal param(Del Pozzo+ 2013: distinguish R~11, 13 km with 15 events?) • Recent analytics confirmed by numerical relativity (Bernuzzi et al. 2012) • High-freq sensitivity key Damour et al., arXiv:1203.4352 High-freq modeling, too

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