6 papers
Stable X-ray reverberation lags in the black hole X-ray binary Swift J1727.8-1613
Wei Yu, Sinan Allak, Zi-Xu Yang +3
Aims. We investigate the evolution of X-ray reverberation lags in the black hole X-ray binary Swift J1727.8-1613 during its 2023 outburst, with the aim of probing the inner accreti…
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…
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…
Discovery of a 9.67-s pulsar in an ultraluminous X-ray source in NGC 4631 with XMM-Newton
L. Ducci, S. Mereghetti, F. Pintore +4
Thanks to a recent observation with XMM-Newton, we discovered periodic pulsations at P= 9.6652 +/- 0.0002 s in a new ultraluminous X-ray source (ULX) in the galaxy NGC 4631. This s…
Unveiling the nature of donor stars of ULXs in NGC 1559
S. Allak, A. Akyuz
X-ray data provide insights into accretion processes and the compact objects of ultraluminous X-ray sources (ULXs), while optical and infrared (IR) observations help identify the d…