153 citations · 339 across the 23 of their papers we have counts for
23 papers
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…
Standardizing reverberation-mapped H active galactic nuclei using time-averaged radiusluminosity relations with 5100\,Å\,, broad H, and narrow \OIII\ luminosities
Shulei Cao, Amit Kumar Mandal, Michal Zajaček +1
Active galactic nuclei (AGN) have been studied as alternate probes in cosmology due to their large and stable luminosities and broad redshift range. Previously it was shown that hi…
Standardizing a larger, higher-quality, homogeneous sample of reverberation-mapped H active galactic nuclei using the broad-line region radius-luminosity relation
Shulei Cao, Amit Kumar Mandal, Michal Zajaček +1
We present a high-quality, homogeneous sample of 157 H reverberation-mapped active galactic nuclei (RM AGNs) spanning redshifts , which is approximat…
Standardizing reverberation-mapped H and H active galactic nuclei using radius--luminosity relations involving monochromatic and broad H luminosities
Shulei Cao, Amit Kumar Mandal, Michal Zajaček +2
We test the standardizability of a homogeneous sample of 41 lower-redshift () active galactic nuclei (AGNs) reverberation-mapped (RM) using the broad H…
Revealing EMRI/IMRI candidates with quasiperiodic ultrafast outflows
Michal Zajaček, Petra Suková, Vladimír Karas +7
The first detection of the quasiperiodic ultrafast outflow in the ASASSN-20qc system was reported by Pasham et al. (2024). The outflow is revealed in the soft X-ray spectra as an a…
UV Fe II emission model of HE 0413-4031 and its relation to broad-line time delays
Michal Zajaček, Swayamtrupta Panda, Ashwani Pandey +11
Fe II emission is a well-known contributor to the UV spectra of active galactic nuclei and the modeling of this part may affect the results obtained for the MgII emiss…
Effects of heterogeneous data sets and time-lag measurement techniques on cosmological parameter constraints from MgII and CIV reverberation-mapped quasar data
Shulei Cao, Michal Zajaček, Bożena Czerny +2
Previously, we demonstrated that MgII and CIV reverberation-mapped quasars (RM QSOs) are standardizable and that the cosmological parameters inferred using the broad-line region ra…
Effect of extinction on quasar luminosity distances determined from UV and X-ray flux measurements
Michal Zajaček, Bożena Czerny, Narayan Khadka +4
In Khadka et al. (2023), a sample of X-ray-detected reverberation-mapped quasars was presented and applied for the comparison of cosmological constraints inferred using two well-es…
Wavelength-resolved reverberation mapping of intermediate redshift quasars HE 0413-4031 and HE 0435-4312: Dissecting Mg II, optical Fe II, and UV Fe II emission regions
Raj Prince, Michal Zajaček, S. Panda +24
We present the wavelength-resolved reverberation mapping (RM) of combined MgII and UV FeII broad-line emissions for two intermediate redshifts (z1), luminous quasars - HE 041…
Ram-pressure stripped radio tail and two ULXs in the spiral galaxy HCG 97b
Dan Hu, Michal Zajaček, Norbert Werner +11
We report LOFAR and VLA detections of extended radio emission in the spiral galaxy HCG 97b, hosted by an X-ray bright galaxy group. The extended radio emission detected at 144 MHz,…
Wavelength-resolved Reverberation Mapping of quasar CTSC30.10: Dissecting MgII and FeII emission regions
Raj Prince, Michal Zajaček, Bożena Czerny +20
We present the results of the reverberation monitoring aimed at MgII broad line and FeII pseudocontinuum for the luminous quasar CTS C30.10 (z = 0.90052) with the Southern African…
Do reverberation-measured H quasars provide a useful test of cosmology?
Narayan Khadka, Mary Loli Martínez-Aldama, Michal Zajaček +2
We use 118 H quasar (QSO) observations in the redshift range to simultaneously constrain cosmological model parameters and QSO 2-parameter radius-lumin…
Standardizing reverberation-measured Mg II time-lag quasars, by using the radius-luminosity relation, and constraining cosmological model parameters
Narayan Khadka, Zhefu Yu, Michal Zajaček +3
We use 78 reverberation-measured Mg II time-lag quasars (QSOs) in the redshift range to constrain cosmological parameters in six different cosmological mo…
Enhanced Doppler Beaming for Dust-Enshrouded Objects and Pulsars in the Galactic Center
Michal Zajaček
Stars within the innermost part of the Nuclear Star Cluster can reach orbital velocities up to a few percent of the light speed. As analyzed by Rafikov (2020), Doppler boosting of…
Perturbing the accretion flow onto a supermassive black hole by a passing star
Petra Suková, Michal Zajaček, Vojtěch Witzany +1
The close neighbourhood of a supermassive black hole contains not only accreting gas and dust, but also stellar-sized objects like stars, stellar-mass black holes, neutron stars, a…
Missing bright red giants in the Galactic center: A fingerprint of its once active state?
Michal Zajaček, Anabella Araudo, Vladimír Karas +5
In the Galactic center nuclear star cluster, bright late-type stars exhibit a flat or even a decreasing surface-density profile, while fainter late-type stars maintain a cusp-like…
Dark energy constraints from quasar observations
B. Czerny, M. L. Martínez-Aldama, G. Wojtkowska +9
Recent measurements of the parameters of the Concordance Cosmology Model (CDM) done in the low-redshift Universe with Supernovae Ia/Cepheids, and in the distant Universe done wi…
Distribution of Radio Spectral Slopes of Galaxies in Optical Diagnostic Diagrams
Michal Zajaček, Andreas Eckart, Silke Britzen +1
For about 500 intermediate-redshift sources (), whose radio flux densities at are larger than 10 mJy, we performed additional observations at 4.85 GHz…
Quasars from LSST as dark energy tracers: first steps
Mary Loli Martínez-Aldama, Swayamtrupta Panda, Bożena Czerny +1
In the near future, new surveys promise a significant increase in the number of quasars (QSO) at large redshifts. This will help to constrain the dark energy models using quasars.…
Reverberation-mapping of distant quasars: time-lag determination using different methods
Michal Zajaček, Bożena Czerny, Mary-Loli Martinez Aldama +1
By applying different statistically robust methods, we analyze the time-lag between the continuum and ionized line-emission (Mg II line) light curves for the distant bright quasar…
Electric charge of black holes: Is it really always negligible?
Michal Zajaček, Arman Tursunov
We discuss the problem of the third black hole parameter, an electric charge. While the mass and the spin of black holes are frequently considered in the majority of publications,…
On the charge of the Galactic centre black hole
Michal Zajaček, Arman Tursunov, Andreas Eckart +1
The Galactic centre supermassive black hole (SMBH), in sharp contrast with its complex environment, is characterized by only three classical parameters -- mass, spin, and electric…
A stellar fly-by close to the Galactic centre: Can we detect stars on highly-relativistic orbits?
Michal Zajaček, Arman Tursunov
The Galactic centre Nuclear Star Cluster is one of the densest stellar clusters in the Galaxy. The stars in its inner portions orbit the supermassive black hole associated with com…