The curved X-ray spectrum of PSR B1509-58 observed with BeppoSAX

¹ Istituto di Fisica Cosmica ed Applicazioni all'Informatica CNR, Via U. La Malfa 153, 90146 Palermo, Italy
² Istituto di Astrofisica Spaziale CNR, via Fosso del Cavaliere, 00113 Roma, Italy
³ Osservatorio Astronomico di Torino, Strada Osservatorio 20, 10025 Pino Torinese, Italy
⁴ Dipartimento di Fisica Generale dell'Università, Via Pietro Giuria 1, 10125 Torino, Italy
⁵ SRON-Utrecht, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

Corresponding author: G. Cusumano, cusumano@ifcai.pa.cnr.it on leave from Università La Sapienza, Roma, Italy.

Received: 22 October 2000
Accepted: 5 June 2001

Abstract

We report timing and spectral results for PSR B1509-58 observed by BeppoSAX in February 1998. We obtained pulse profiles with high statistical significance from 0.1 to 300 keV that exhibit the well-known broad asymmetric single pulse. The shape of this pulse does not change across this energy window and can be described as the sum of a narrow and a broader Gaussian component separated in phase. The spectral distribution can be accurately represented, over the entire BeppoSAX energy range, by a curved function rather than a simple power-law shape. The extrapolation of this model to higher energies is also consistent with the COMPTEL fluxes in the 0.75-30 MeV range, with the maximum luminosity for the broad pulse of PSR B1509-58 reached at MeV. The comparison with the Crab pulsar spectrum suggests a possible origin of the X-ray emission in terms of synchrotron radiation from secondary pair particles near the neutron star.