Browsing Research publications by Author "Roberts, T. P."

Now showing items 1-5 of 5

    • Examining the nature of the ultraluminous X-ray source Holmberg II X-1 

      Barra, F.; Pinto, C.; Middleton, M.; Di Salvo, T.; Walton, D. J.; Gúrpide, A.; Roberts, T. P. (2024-02-06)
      We present a comprehensive spectral analysis of the ultraluminous X-ray source Holmberg II X-1 using broadband and high-resolution X-ray spectra taken with the XMM-Newton satellite over a period of 19 yr, taking advantage ...

    • The hyperluminous X‐ray source population 

      MacKenzie, A. D. A.; Roberts, T. P.; Walton, D. J. (2023-05-16)
      We have recently published a catalog of 1843 candidate ultraluminous X‐ray sources (ULXs). This is the largest catalog of ULXs to date and was built by cross‐correlating recent serendipitous source catalogs from the ...

    • A Multi-Mission Catalogue of Ultraluminous X-ray Source Candidates 

      Walton, D. J.; Mackenzie, A. D. A.; Gully, H.; Patel, N. R.; Roberts, T. P.; Earnshaw, H. P.; Mateos, S. (2022-01-01)
      We present a new, multi-mission catalogue of ultraluminous X-ray source (ULX) candidates, based on recent data releases from each of the XMM-Newton, Swift and Chandra observatories (the 4XMM-DR10, 2SXPS and CSC2 catalogues, ...

    • Probing the nature of the low state in the extreme ultraluminous X-ray pulsar NGC 5907 ULX1 

      Fuerst, F.; Walton, D. J.; Israel, Gian Luca; Bachetti, M.; Barret, D.; Brightman, Murray; Earnshaw, H. P.; Fabian, A.; Heida, M.; Imbrogno, M.; Middleton, M. J.; Pinto, C.; Salvaterra, R.; Roberts, T. P.; Castillo, G. A. Rodríguez; Webb, N. (2023-04-12)
      NGC 5907 ULX1 is the most luminous ultra-luminous X-ray pulsar (ULXP) known to date, reaching luminosities in excess of 1041 erg s-1. The pulsar is known for its fast spin-up during the on-state. Here, we present a long-term ...

    • Unveiling the disc structure in ultraluminous X-ray source NGC 55 ULX-1 

      Barra, F.; Pinto, C.; Walton, D. J.; Kosec, P.; D'Aì, A.; Salvo, T. Di; Santo, M. Del; Earnshaw, H.; Fabian, A. C.; Fuerst, F.; Marino, A.; Pintore, F.; Robba, A.; Roberts, T. P. (2022-11-01)
      Despite two decades of studies, it is still not clear whether ULX spectral transitions are due to stochastic variability in the wind or variations in the accretion rate or in the source geometry. The compact object is also ...