Magnetic Fields of Accreting X-Ray Pulsars with the Rossi X-Ray Timing Explorer

By W. Coburn. 2001

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Using a consistent set of models, we parameterized the X-ray spectra of all accreting pulsars in the Rossi X-Ray Timing Explorer (RXTE) database that exhibit cyclotron resonance scattering features (CRSFs, or cyclotron lines). These sources in our sample are Her X-1, 4U 0115+63, Cen X-3, 4U 1626-67, XTE J1946-274, Vela X-1, 4U 1907+09, 4U 1538-52, GX 301-2, and 4U 0352+309 (X Per). We searched for correlations among the spectral parameters, concentrating on how the cyclotron line energy relates to the continuum and therefore how the neutron star B-field influences the X-ray emission. As expected, we found a correlation between the CRSF energy and the spectral cutoff energy. However, with our consistent set of fits we found that the relationship is more complex than what has been reported previously. Also, we found not only that the width of the cyclotron line correlates with the energy (as suggested by theory), but also that the width scaled by the energy correlates with the depth of the feature. We discuss the implications of these results, including the possibility that accretion directly affects the relative alignment of the neutron star spin and dipole axes. Finally, we comment on the current state of fitting phenomenological models to spectra in the RXTE/BeppoSAX era and the need for better theoretical models of the X-ray continua of accreting pulsars.

Subfields: Astronomy and Astrophysics, Atmospheric Science, Instrumentation

View Paper: https://www.semanticscholar.org/paper/df30ad1059ba651d609598a30c058e7d34482878

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Citations in the corpus

Thermal and Bulk Comptonization in Accretion-powered X-Ray Pulsars (2006, methodology): “…sources are often well fitted using a combination of a power-law spectrum in the 5− 20 keV energy range plus a blackbody component with a temperature in the range T ∼ 106−7K (e.g., Coburn et al. 2002; di Salvo et al. 1998; White et al. 1983) and a quasi-exponential cutoff at energy E ∼ 20 − 30 keV.”
THE NUCLEAR SPECTROSCOPIC TELESCOPE ARRAY (NuSTAR) HIGH-ENERGY X-RAY MISSION (2013, background): “Neutron stars are exotic objects where densities, magnetic fields, and gravitational fields are all extreme (Lattimer & Prakash 2004; Lattimer & Prakash 2007; Truemper et al. 1978; Coburn et al. 2002).”
Cyclotron lines in highly magnetized neutron stars (2018, methodology): “For previous reviews about cyclotron line sources, see for example, Coburn et al. (2002), Staubert (2003), Heindl et al. (2004), Terada et al. (2007), Wilms (2012), Caballero & Wilms (2012), Revnivtsev & Mereghetti (2016), Maitra (2017).”
High-mass X-ray binaries in the Milky Way (2013, background): “, 2005), sometimes modified by absorption and emission lines in the soft X-rays and by Cyclotron Resonance Scattering Features (CRSF) at higher energies (Coburn et al., 2002; Filippova et al., 2005; Caballero and Wilms, 2012).”