Identification and characterisation of the gamma-ray counterpart of the transitional pulsar candidate CXOU J110926.4–650224
Transitional millisecond pulsars (tMSPs) represent a crucial link between the rotation-powered and accretion-powered states of binary pulsars. During their active X-ray state, tMSPs are the only low-mass X-ray binary systems detected up to GeV energies by the Fermi Large Area Telescope (LAT). CXOU J110926.4–650224 is a newly discovered tMSP candidate in an active X-ray state and is potentially spatially compatible with a faint gamma-ray source listed in the latest 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. We analysed Fermi -LAT data collected from August 2008 to June 2023 to determine a more accurate localisation of the gamma-ray source, characterise its spectral properties, and investigate potential time variability. By thoroughly reconstructing the gamma-ray background around the source using a weighted likelihood model, we obtain a new localisation that aligns with the position of the X-ray source at the 95% confidence level, with a test statistic value of ∼42. This establishes a spatial association between the gamma-ray source and CXOU J110926.4–650224. The gamma-ray emission is adequately described by a power-law model with a photon index of Γ = 2.5 ± 0.1 and a corresponding flux of (3.7 ± 0.9)×10 −12 erg cm −2 s −1 in the 0.1–300 GeV range.
Authors
- A. Riggio (ORCID: https://orcid.org/0000-0002-6145-9224)
- F. Coti Zelati (ORCID: https://orcid.org/0000-0001-7611-1581)
- A. Marino (ORCID: https://orcid.org/0000-0001-5674-4664)
- Antonella Manca (ORCID: https://orcid.org/0000-0003-2497-1541)
- A. Sanna (ORCID: https://orcid.org/0000-0002-0118-2649)
- T. Di Salvo (ORCID: https://orcid.org/0000-0002-3220-6375)
- N. Rea
- J. Ballet
- Diego F. Torres (ORCID: https://orcid.org/0000-0002-1522-9065)
- L. Burderi (ORCID: https://orcid.org/0000-0001-5458-891X)
- R. Iaria (ORCID: https://orcid.org/0000-0003-2882-0927)
- Junru Li (ORCID: https://orcid.org/0009-0001-5100-0006)
Institutions
- Institució Catalana de Recerca i Estudis Avançats (ES)
- University of Science and Technology of China (CN)
- Centre National de la Recherche Scientifique (FR)
- Institute of Space Sciences (ES)
- Université Paris Cité (FR)
- Commissariat à l'Énergie Atomique et aux Énergies Alternatives (FR)
- Université Paris-Saclay (FR)
- Astrophysique, Instrumentation et Modélisation (FR)
- Institut d'Estudis Espacials de Catalunya (ES)
- CEA Paris-Saclay (FR)
- Istituto Nazionale di Fisica Nucleare, Sezione di Cagliari (IT)
- Istituto di Astrofisica Spaziale e Fisica cosmica di Palermo (IT)
- Osservatorio Astronomico di Cagliari (IT)
- University of Palermo (IT)
Publication Details
- Journal
- Astronomy and Astrophysics
- Published
- 2025-02-28
- DOI
- https://doi.org/10.1051/0004-6361/202453010
- Citations
- 1
- Primary Topic
- Pulsars and Gravitational Waves Research
- Type
- article
- Field-Weighted Citation Impact
- 1.15
Funders
- U.S. Department of Energy
- National Aeronautics and Space Administration
- European Commission
- Ministry of Education, Culture, Sports, Science and Technology
- Centre National d’Etudes Spatiales
- Vetenskapsrådet
- Centre National de la Recherche Scientifique
- Horizon 2020 Framework Programme
- Japan Aerospace Exploration Agency
- Agencia Estatal de Investigación
- Institut National de Physique Nucléaire et de Physique des Particules