18 papers
EXPO: a quantum leap in fast, wide-band X-ray polarimetry for astrophysics
Paolo Soffitta, Sebastien Guillot, Ian Hutchinson +137
The Enhanced X-ray Polarimetry Observatory (EXPO) is a mission concept proposed to ESA as an M8 candidate, with a prospective launch in 2041. Building on the scientific success of…
Spectral and timing variability of the transient ultraluminous X-ray source NGC 4631 X-4
Sinan Allak, Wei Yu, Lorenzo Ducci +4
Ultraluminous X-ray sources (ULXs) are among the best laboratories for studying super-Eddington accretion onto compact objects. We present a detailed spectral and timing analysis o…
A candidate cyclotron line at 1.89 keV in the ultraluminous X-ray source NGC 4861 X-2
Sinan Allak, Lorenzo Ducci, Valery F. Suleimanov +6
In this Letter, we report the detection of an absorption-like feature at ~1.89 keV in Chandra/ACIS spectra of the ultraluminous X-ray source NGC 4861 X-2, based on the deepest obse…
NICER detection of a new candidate cyclotron line in the bursting X-ray pulsar GRO J1744-28
Qi Liu, Lingda Kong, Long Ji +15
We report the detection of cyclotron resonant scattering features (CRSFs) in the spectrum of the unique bursting pulsar GRO J1744-28, observed during its recent outburst in 2021 wi…
Rapid quasi-periodic reconfiguration of the accretion column in pulsar 1A 0535+262
Lingda Kong, Xiaohang Dai, Andrea Santangelo +12
Accretion onto strongly magnetized neutron stars is commonly interpreted using quasi-steady models, in which the accretion-column structure adjusts smoothly to the mass inflow rate…
Identification of three new ultraluminous X-ray sources in NGC 4631 and NGC 1097: Evidence for stellar-mass black holes
Sinan Allak, Aysun Akyuz, Yasemin Aladag +2
Recent observations of galaxies continue to reveal new ultraluminous X-ray sources (ULXs), increasing their known population and improving the statistics needed to understand their…