The NuSTAR view of the non-thermal emission from PSR J0437-4715
Abstract
The millisecond pulsar PSR J0437-4715 is the ideal target to place constraints on the dense matter equation of state. Its proximity allows for modelling of the spin-phase modulated light curve from which measurements of the neutron star radius can be obtained, and therefore, tight constraints on the dense matter equation of state. However, such modelling of the light curve requires a good understanding of the broadband emission and in particular of the surface emission. In particular, the poorly constrained non-thermal emission (above 3 keV) was causing some uncertainties in the spectral modelling of the thermal emission below 3 keV (such as the amount of absorption, and on the number of surface thermal components). A 200 ks observation with NuSTAR provided the sensitivity in the 3-20 keV range necessary to constrain the slope of the non-thermal emission. A simultaneous analysis of NuSTAR and XMM-Newton spectra removed remaining ambiguities in the spectral modelling of the surface emission from PSR J0437-4715. Furthermore, the NuSTAR observation demonstrated that the non-thermal emission was actually pulsed at the pulsar spin period, a crucial information to take into account when modelling the light curve and attempting to measure the neutron star radius. This NuSTAR observation provides further impetus for future observations with the NICER satellite (Neutron Star Interior Composition Explorer) whose sensitivity will provide much stricter constraints on the radius of PSR J0437-4715, and therefore on the equation of state of nuclear matter.
- Publication:
-
41st COSPAR Scientific Assembly
- Pub Date:
- July 2016
- Bibcode:
- 2016cosp...41E.754G