New chandra and RXTE results on the X-ray/gamma-ray millisecond pulsar PSR J0128+4232

Millisecond pulsar PSR J0218+4232 shows remarkable high-energy properties: Very hard pulsed X-ray emission up to 10 keV was reported and, more remarkably, a likely detection of high-energy gamma-rays (> 100 MeV) with a soft spectrum. The relative phasing of the X-ray and gamma -ray profiles, however, was unknown. We report here results from a Chandra (0.08-10 keV) observation of PSR J0218+4232 which shows that the X-ray pulses are aligned with the gamma -ray pulses providing supporting evidence for the first detection of high-energy gamma-rays from this source (statistical significance of 4.9 sigma of finding the two gamma -ray pulses aligned with the X-ray pulses). The Chandra observations also show that the X-ray DC component of PSR J0218+4232 is compact and can be explained as being due to emission from a bombarded polar cap. More recently, also an RXTE (2-60 keV) observation was performed, showing significant pulsed emission up to 20-30 keV. The new results from Chandra and RXTE will be presented and discussed.