Chandra and RXTE studies of the X-ray/gamma-ray millisecond pulsar PSR J0218+4232
Abstract
We report on high-resolution spatial and timing observations of the millisecond pulsar PSR J0218+4232 performed with the Chandra X-ray Observatory (CXO) and the Rossi X-ray Timing Explorer (RXTE). With these observations we were able to study: a) the possible spatial extent at X-ray energies of the DC source coincident with PSR J0218+4232 in detail (CXO), b) the relative phasing between the X-ray, radio and gamma-ray profiles (CXO and RXTE) and c) the spectral properties at energies beyond 10 keV (RXTE). We found no indications for extended emission at X-ray energies down to about 1" scales and confirmed the presence of a point-like DC-component. The two non-thermal pulses in the X-ray profile are found to be aligned with two of the three pulses visible at radio-frequencies, and more importantly, with the two gamma-ray pulses seen in the EGRET 100-1000 MeV pulse profile. The latter yields now a random occurrence probability for the detection of the gamma-ray signal of about 10-6, which corresponds to a 4.9 sigma detection significance. This strenghtens the credibility of our earlier claimed detection of pulsed high-energy gamma-ray emission from this millisecond pulsar. The pulsed spectrum extends to about 20 keV and can be described by a power-law with photon index of 1.14, slightly softer than measured by the BeppoSAX and XMM for energies below 10 keV. The hard spectrum at X-ray energies and the soft spectrum at high gamma-ray energies is similar to that of Unidentified Gamma-Ray Sources (UGS). Therefore, fast millisecond pulsars with hard X-ray spectra seem to be promising candidates for an UGS association.
- Publication:
-
Pulsars, AXPs and SGRs Observed with BeppoSAX and Other Observatories
- Pub Date:
- July 2003
- Bibcode:
- 2003pasb.conf...31K