15 papers
Testing Black Holes with Interstellar Missions: II. Flyby Probes
Yi Fan, Cosimo Bambi, Leda Gao +2
Recently, we demonstrated that while an interstellar mission to the nearest black hole remains highly speculative and extraordinarily challenging, it is not entirely implausible wi…
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…
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…
First detection of X-ray polarization from the long-period X-ray pulsar 4U 1954+319
Alexander Salganik, Lingda Kong, Sofia V. Forsblom +6
We report the first detection of X-ray polarization with the Imaging X-ray Polarimetry Explorer from the X-ray pulsar (XRP) 4U 1954319. The source belongs to an extremely rare c…
Testing Black Holes with Interstellar Missions: I. Orbiting Probes
Leda Gao, Cosimo Bambi, Yi Fan +3
Recently, we showed that the possibility of an interstellar mission to the closest black hole, while highly speculative and extremely challenging, is not completely unrealistic wit…