Identification of the gamma-ray counterpart of the transitional pulsar candidate J1109

Transitional millisecond pulsars (tMSPs) represent a crucial link between binary pulsars in their rotation-powered and accretion-powered states. During their active X-ray state, the tMSPs are the only low-mass X-ray binary systems that are detected up to GeV energies using the Fermi Large Area Telescope (LAT). CXOU J110926.4-650224 is a newly discovered tMSP candidate in an active X-ray state located close to a faint gamma-ray source, listed in the latest release of the Fermi/LAT point-source catalogue as 4FGL J1110.3-6501. Confirming the association between CXOU J110926.4-650224 and the Fermi source is a key step towards validating its classification as a tMSP. In this study, we present an analysis of Fermi/LAT data collected from August 2008 to June 2023, for a total of about 15 years, aiming to achieve a more accurate localisation of the gamma-ray source and characterise its spectral properties. By thoroughly reconstructing the gamma-ray background around the source, we obtain a new localisation that matches the position of the X-ray source at the 95% confidence level. This establishes a possible spatial association between the gamma-ray source and CXOU J110926.4-650224.

Arianna Manca – Università degli Studi di Cagliari

Arianna Manca earned her PhD in Physics at the University of Cagliari in 2024, where she worked mostly on the spectral analysis of Low-Mass X-ray Binary systems, hosting neutron stars or black holes. As member of the HERMES collaboration, she worked on the localisation of Gamma-Ray Bursts through triangulation techniques. During her stay at the Institute of Space Sciences of Barcelona, she worked on the analysis of gamma-ray data of a candidate transitional pulsar.