PULSE PROFILES FROM SPINNING NEUTRON STARS IN THE HARTLE–THORNE APPROXIMATION

We present a new numerical algorithm for the calculation of pulse profiles from spinning neutron stars in the Hartle–Thorne approximation. Our approach allows us to formally take into account the effects of Doppler shifts and aberration, of frame dragging, as well as of the oblateness of the stellar surface and of its quadrupole moment. We confirm an earlier result that neglecting the oblateness of the neutron-star surface leads to ≃ 5%–30% errors in the calculated profiles and further show that neglecting the quadrupole moment of its spacetime leads to ≃ 1%–5% errors at a spin frequency of ≃ 600 Hz. We discuss the implications of our results for the measurements of neutron-star masses and radii with upcoming X-ray missions, such as NASA's NICER and ESA's LOFT.

[1]  Dimitrios Psaltis,et al.  NARROW ATOMIC FEATURES FROM RAPIDLY SPINNING NEUTRON STARS , 2012, 1209.0768.

[2]  F. Özel.  Surface emission from neutron stars and implications for the physics of their interiors , 2012 .

[3]  Takashi Okajima,et al.  The Neutron star Interior Composition ExploreR (NICER): an Explorer mission of opportunity for soft x-ray timing spectroscopy , 2012, Other Conferences.

[4]  G. Pappas,et al.  Revising the multipole moments of numerical spacetimes and its consequences. , 2012, Physical review letters.

[5]  T. Johannsen,et al.  A RAY-TRACING ALGORITHM FOR SPINNING COMPACT OBJECT SPACETIMES WITH ARBITRARY QUADRUPOLE MOMENTS. II. NEUTRON STARS , 2011, 1110.4389.

[6]  T. Johannsen,et al.  A RAY-TRACING ALGORITHM FOR SPINNING COMPACT OBJECT SPACETIMES WITH ARBITRARY QUADRUPOLE MOMENTS. I. QUASI-KERR BLACK HOLES , 2010, 1011.4078.

[7]  D. Leahy,et al.  CONSTRAINTS ON THE MASS AND RADIUS OF THE NEUTRON STAR XTE J1807-294 , 2011, 1106.3131.

[8]  D. Leahy,et al.  MULTI-EPOCH ANALYSIS OF PULSE SHAPES FROM THE NEUTRON STAR SAX J1808.4−3658 , 2009, 0911.0887.

[9]  M. Miller,et al.  A MODEL FOR THE WAVEFORM BEHAVIOR OF ACCRETING MILLISECOND X-RAY PULSARS: NEARLY ALIGNED MAGNETIC FIELDS AND MOVING EMISSION REGIONS , 2008, 0808.4159.

[10]  D. Leahy,et al.  CONSTRAINTS ON THE PROPERTIES OF THE NEUTRON STAR XTE J1814−338 FROM PULSE-SHAPE MODELS , 2008, 0806.0824.

[11]  D. Leahy,et al.  Limits on Mass and Radius for the Millisecond-Period X-Ray Pulsar SAX J1808.4?3658 , 2007, astro-ph/0703287.

[12]  D. Leahy,et al.  The Oblate Schwarzschild Approximation for Light Curves of Rapidly Rotating Neutron Stars , 2007, astro-ph/0703123.

[13]  Jonathan E. Grindlay,et al.  Constraints on Neutron Star Properties from X-Ray Observations of Millisecond Pulsars , 2006, astro-ph/0612791.

[14]  D. Leahy,et al.  Light Curves for Rapidly Rotating Neutron Stars , 2006, astro-ph/0609325.

[15]  J. Poutanen,et al.  Pulse profiles of millisecond pulsars and their Fourier amplitudes , 2006, astro-ph/0608663.

[16]  S. Babak,et al.  Mapping spacetimes with LISA: inspiral of a test body in a ‘quasi-Kerr’ field , 2005, gr-qc/0510057.

[17]  P. C. Agrawal.  A broad spectral band Indian Astronomy satellite ‘Astrosat’ , 2006 .

[18]  Tod E. Strohmayer,et al.  Constraints on Neutron Star Parameters from Burst Oscillation Light Curves of the Accreting Millisecond Pulsar XTE J1814-338 , 2005 .

[19]  Deepto Chakrabarty,et al.  THE ENERGY DEPENDENCE OF MILLISECOND OSCILLATIONS IN THERMONUCLEAR X-RAY BURSTS , 2003 .

[20]  N. Stergioulas.  Rotating Stars in Relativity , 1998, Living reviews in relativity.

[21]  F. Ozel,et al.  The Amplitude Evolution and Harmonic Content of Millisecond Oscillations in Thermonuclear X-Ray Bursts , 2002, astro-ph/0204501.

[22]  Juri Poutanen,et al.  On the Nature of the X-ray Emission of Accreting Millisecond Pulsar SAX J1808.4-3658 , 2002, astro-ph/0303084.

[23]  Tod E. Strohmayer,et al.  Bounds on Compactness for Low-Mass X-Ray Binary Neutron Stars from X-Ray Burst Oscillations , 2001, astro-ph/0102421.

[24]  V. Kaspi,et al.  Constraints on Thermal Emission Models of Anomalous X-Ray Pulsars , 2001, astro-ph/0105372.

[25]  R. Narayan,et al.  General Relativistic Constraints on Emission Models of Anomalous X-Ray Pulsars , 2000, astro-ph/0004266.

[26]  D. Lamb,et al.  Oscillation Waveforms and Amplitudes from Hot Spots on Neutron Stars , 2000, astro-ph/0001544.

[27]  R. Romani,et al.  Light Curves of Rapidly Rotating Neutron Stars , 2000, astro-ph/0004411.

[28]  E. Poisson,et al.  Quadrupole Moments of Rotating Neutron Stars , 1997, gr-qc/9709033.

[29]  M. Miller,et al.  Bounds on the Compactness of Neutron Stars from Brightness Oscillations during X-Ray Bursts , 1997, astro-ph/9711325.

[30]  G. Pavlov,et al.  Mass-to-Radius Ratio for the Millisecond Pulsar J0437–4715 , 1997, astro-ph/9709255.

[31]  Bernard F. Schutz,et al.  Living Reviews in Relativity: Making an Electronic Journal Live , 1997 .

[32]  N. Stergioulas,et al.  Comparing models of rapidly rotating relativistic stars constructed by two numerical methods , 1994, astro-ph/9411032.

[33]  Dany Page.  Surface temperature of a magnetized neutron star and interpretation of the ROSAT data. 1: Dipole fields , 1994 .

[34]  Stuart L. Shapiro,et al.  Rapidly Rotating Neutron Stars in General Relativity: Realistic Equations of State , 1993 .

[35]  C. Ftaclas,et al.  Hot spots on neutron stars - The near-field gravitational lens , 1982 .

[36]  J. Hartle,et al.  Slowly Rotating Relativistic Stars. II. Models for Neutron Stars and Supermassive Stars , 1968 .