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 ~ 1 arcsec scales and confirmed the presence of a point-like DC-component. The 2 non-thermal pulses in the X-ray profile are found to be aligned with 2 of the 3 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 reduces now the random occurrence probability for the detected gamma-ray signal to ~ 1.E-6, which corresponds to a 4.9 sigma detection significance.