Speaker
Description
Transitional millisecond pulsars (tMSPs) bridge the gap between accreting neutron stars in low-mass X-ray binaries and rotation-powered millisecond radio pulsars, offering a unique laboratory to study the interplay between accretion and pulsar activity. These systems display a subluminous X-ray state characterized by rapid transitions between high, low, and flaring emission modes.
Multi-wavelength campaigns on the prototype tMSP PSR J1023+0038 have established a complex scenario in which a compact jet, discrete ejecta, inflowing matter, and the pulsar wind interact to regulate the source phenomenology. Recently, we carried out the first multi-wavelength polarimetric study of PSR J1023+0038 using data from IXPE, the VLT, and the VLA. We detect a linear polarization degree of (12±3)% in the 2–6 keV band during the high mode. The polarization angle is aligned with that measured in the optical band, strongly suggesting a common physical origin. In the low mode, the polarization is not significantly detected, yielding a 90% confidence upper limit of 26%.
These results indicate that both optical and X-ray polarization likely arise from synchrotron emission produced at the shock interface between the pulsar wind and the inner accretion flow. In addition, simultaneous radio, optical, and X-ray observations obtained during this campaign provide the first coordinated view of the flaring mode, highlighting the crucial role of outflows in shaping the system behaviour.
The capabilities of NewAthena will enable unprecedented studies of rapid mode switching and faint polarization-linked spectral components in tMSPs. Combined with coordinated optical and radio facilities, NewAthena will be key to disentangling the accretion–ejection physics of these systems, fully exploiting the multi-band synergies that define the next decade of high-energy astrophysics.
