204 citations · 1.8k across the 55 of their papers we have counts for
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Probing bumblebee gravity with black hole X-ray data
Jiale Gu, Shafqat Riaz, Askar B. Abdikamalov +2
Bumblebee gravity is one of the simplest gravity theories with spontaneous Lorentz symmetry breaking. Since we know a rotating black hole solution in bumblebee gravity, we can pote…
Testing regular black holes with X-ray and GW data
Shafqat Riaz, Swarnim Shashank, Rittick Roy +5
The presence of spacetime singularities in physically relevant solutions of the Einstein Equations is normally interpreted as a symptom of the breakdown of classical general relati…
Testing Gravity with Black Hole Shadow Subrings
Dimitry Ayzenberg
The black hole shadow, first observed by the Event Horizon Telescope in 2017, is the newest method for studying black holes and understanding gravity. Much work has gone into under…
Observational appearance of Kaluza-Klein black holes
Temurbek Mirzaev, Askar B. Abdikamalov, Ahmadjon A. Abdujabbarov +3
The optical properties of rotating black holes in Kaluza-Klein theory described by the total mass, spin, and electric and magnetic charges are investigated in detail. Using a devel…
X-ray reflection spectroscopy with Kaluza-Klein black holes
Jiachen Zhu, Askar B. Abdikamalov, Dimitry Ayzenberg +6
Kaluza-Klein theory is a popular alternative theory of gravity, with both non-rotating and rotating black hole solutions known. This allows for the possibility that the theory coul…
Reflection features in the X-ray spectrum of Fairall 9 and implications for tests of general relativity
Honghui Liu, Haiyang Wang, Askar B. Abdikamalov +2
X-ray reflection spectroscopy is potentially a powerful tool to probe the spacetime geometry around astrophysical black holes and test general relativity in the strong field regime…
Singularity-free black holes in conformal gravity: new observational constraints
Menglei Zhou, Askar B. Abdikamalov, Dimitry Ayzenberg +4
We consider the family of singularity-free rotating black hole solutions in Einstein's conformal gravity found in Bambi, Modesto & Rachwal (2017) and we constrain the value of the…
Testing general relativity with the stellar-mass black hole in LMC X-1 using the continuum-fitting method
Ashutosh Tripathi, Menglei Zhou, Askar B. Abdikamalov +6
The iron line and the continuum-fitting methods are currently the two leading techniques for measuring black hole spins with electromagnetic radiation. They can be naturally extend…
Search for traversable wormholes in active galactic nuclei using X-ray data
Ashutosh Tripathi, Biao Zhou, Askar B. Abdikamalov +2
In a previous paper, one of us calculated iron K line profiles emitted from possible accretion disks around traversable wormholes as a first step to use X-ray reflection spectro…
Modeling uncertainties in X-ray reflection spectroscopy measurements I: Impact of higher order disk images
Menglei Zhou, Dimitry Ayzenberg, Cosimo Bambi +1
There are many simplifications in current relativistic reflection models and this introduces systematic uncertainties in the measurement of the properties of the source. In this pa…
RELXILL_NK: A Black Hole Relativistic Reflection Model for Testing General Relativity
Askar B. Abdikamalov, Dimitry Ayzenberg, Cosimo Bambi +1
In this paper, we briefly present RELXILL_NK, the first and currently only readily available model of the relativistic reflection spectrum of black hole accretion disks that includ…
Relativistic reflection spectra of super-spinning black holes
Biao Zhou, Ashutosh Tripathi, Askar B. Abdikamalov +4
We construct a relativistic reflection model in a non-Kerr spacetime in which, depending on the value of the deformation parameter of the metric, there are black hole solutions wit…
Tests of the Kerr hypothesis with GRS 1915+105 using different RELXILL flavors
Yuexin Zhang, Askar B. Abdikamalov, Dimitry Ayzenberg +2
In a previous paper, we tried to test the Kerr nature of the stellar-mass black hole in GRS 1915+105 by analyzing NuSTAR data of 2012 with our reflection model RELXILL_NK. We found…
Testing general relativity with supermassive black holes using X-ray reflection spectroscopy
Askar B. Abdikamalov, Dimitry Ayzenberg, Cosimo Bambi +7
In this paper, we review our current efforts to test General Relativity in the strong field regime by studying the reflection spectrum of supermassive black holes. So far we have a…
Constraining the Johannsen deformation parameter with black hole X-ray data
Ashutosh Tripathi, Askar B. Abdikamalov, Dimitry Ayzenberg +2
We extend our previous work on tests of the Kerr black hole hypothesis using X-ray reflection spectroscopy and we infer observational constraints on the Johannsen deformation param…
Testing the Kerr hypothesis using X-ray reflection spectroscopy with NuSTAR data of Cygnus X-1 in the soft state
Honghui Liu, Askar B. Abdikamalov, Dimitry Ayzenberg +4
We continue exploring the constraining capabilities of X-ray reflection spectroscopy to test the Kerr-nature of astrophysical black holes and we present the results of our analysis…
Black hole mimicker hiding in the shadow: Optical properties of the -metric
Askar B. Abdikamalov, Ahmadjon A. Abdujabbarov, Dimitry Ayzenberg +3
Can the observation of the "shadow" allow us to distinguish a black hole from a more exotic compact object? We study the motion of photons in a class of vacuum static axially-symme…
Testing General Relativity with X-ray reflection spectroscopy: The Konoplya-Rezzolla-Zhidenko parametrization
Sourabh Nampalliwar, Shuo Xin, Shubham Srivastava +6
X-ray reflection spectroscopy is a promising technique for testing general relativity in the strong field regime, as it can be used to test the Kerr black hole hypothesis. In this…
XSPEC model for testing the Kerr black hole hypothesis using the continuum-fitting method
Menglei Zhou, Askar B. Abdikamalov, Dimitry Ayzenberg +3
We present NKBB, an XSPEC model for the thermal spectrum of thin accretion disks in parametric black hole spacetimes. We employ the Novikov-Thorne model for the description of the…
Public Release of RELXILL_NK: A Relativistic Reflection Model for Testing Einstein's Gravity
Askar B. Abdikamalov, Dimitry Ayzenberg, Cosimo Bambi +3
We present the public release version of relxill_nk, an X-ray reflection model for testing the Kerr hypothesis and general relativity. This model extends the relxill model that ass…
About the Kerr nature of the stellar-mass black hole in GRS 1915+105
Yuexin Zhang, Askar B. Abdikamalov, Dimitry Ayzenberg +4
We employ the accretion disk reflection model RELXILL_NK to test the spacetime geometry around the stellar-mass black hole in GRS 1915+105. We adopt the Johannsen metric with the d…
Constraints on the spacetime metric around seven "bare" AGNs using X-ray reflection spectroscopy
Ashutosh Tripathi, Jinli Yan, Yuchan Yang +12
We present the study of a sample of seven "bare" active galactic nuclei (AGN) observed with Suzaku. We interpret the spectrum of these sources with a relativistic reflection compon…
Towards precision tests of general relativity with black hole X-ray reflection spectroscopy
Ashutosh Tripathi, Sourabh Nampalliwar, Askar B. Abdikamalov +5
Astrophysical black hole systems are the ideal laboratories for testing Einstein's theory of gravity in the strong field regime. We have recently developed a framework which uses t…
Testing the Kerr metric with X-ray Reflection Spectroscopy of Mrk 335 Suzaku data
Kishalay Choudhury, Sourabh Nampalliwar, Askar B. Abdikamalov +4
Einstein's gravity has undergone extensive tests in the weak field gravitational limit, with results in agreement with theoretical predictions. There exist theories beyond general…