13 papers
HALO II: Constraining Hubble constant through continuum delay fitting of Fairall 9
Amit Kumar Mandal, Francisco Pozo Nuñez, Vikram Kumar Jaiswal +28
The Hubble tension remains one of the most significant unresolved problems in modern cosmology. A key question is whether it may arise from underestimated systematic uncertainties…
Consistency between X-ray and UV-Optical reverberation measurements in NGC 5548
Amit Kumar Mandal, Bożena Czerny, Michal DovÄiak +2
The hard X-rayemitting hot corona is a key component of active galaxies. Constraints on the hot corona height can be derived from reverberation studies in both the X-ray and opt…
Disk reflection as the origin of the X-ray polarization of NGC 4151 with IXPE
E. Kammoun, M. DovÄiak, J. Podgorný +6
We present an X-ray spectro-polarimetric study of the nearby type-1 active galactic nucleus NGC 4151 using two long IXPE observations obtained in 2022 and 2024, supported by simult…
Polarization properties of thermal accretion disk emission. I. Direct radiation
L. Marra, J. Podgorný, R. Taverna +4
The X-ray polarimetric observing window re-opening is shedding new light on our current understanding of compact accreting sources. This is true, in particular, for stellar-mass bl…
HALO I: Photometric continuum reverberation mapping of Fairall 9
Amit Kumar Mandal, Francisco Pozo Nuñez, Vikram Kumar Jaiswal +23
We investigate the origin of inter-band continuum time delays in active galactic nuclei (AGNs) to study the structure and properties of their accretion disks. We aim to measure the…
Super-Eddington Accretion Geometry: a Remarkable Stability of the Hidden Ultraluminous X-Ray Source Cygnus X-3
Romana Mikušincová, Alexandra Veledina, Fabio Muleri +112
We report on the average and orbital phase-resolved polarization of Cyg X-3 in the hard state during the 2023 Imaging X-ray Polarimetry Explorer (IXPE) observational campaign. We f…