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New Horizons for Fundamental Physics with LISA
K. G. Arun, Enis Belgacem, Robert Benkel +138
The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitatio…
Strong field tests of gravity with electromagnetic and gravitational waves
Sourabh Nampalliwar
For nearly a century, Einstein's theory of gravity has been the standard theory for describing gravitational phenomena in our universe. Along with its successes, limitations of the…
Theory-agnostic tests of gravity with black hole shadows
Sourabh Nampalliwar, Saurabh K
Observations of black hole shadows with the Event Horizon Telescope have paved way for a novel approach to testing Einstein's theory of general relativity. Early analyses of the me…
Testing horizon topology with electromagnetic observations
Sourabh Nampalliwar, Arthur G. Suvorov, Kostas D. Kokkotas
In general relativity without a cosmological constant, a classical theorem due to Hawking states that stationary black holes must be topologically spherical. This result is one of…
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…
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…
Prospects for Fundamental Physics with LISA
Enrico Barausse, Emanuele Berti, Thomas Hertog +318
In this paper, which is of programmatic rather than quantitative nature, we aim to further delineate and sharpen the future potential of the LISA mission in the area of fundamental…
Gravitational-wave versus X-ray tests of strong-field gravity
Alejandro Cardenas-Avendano, Sourabh Nampalliwar, Nicolas Yunes
Electromagnetic observations of the radiation emitted by an accretion disk around a black hole, as well as gravitational wave observations of coalescing binaries, can be used to pr…
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…
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…
A study of the strong gravity region of the black hole in GS 1354-645
Yerong Xu, Sourabh Nampalliwar, Askar B. Abdikamalov +5
It is thought that the spacetime metric around astrophysical black holes is well described by the Kerr solution of Einstein's gravity. However, a robust observational evidence of t…
RELXILL_NK: a relativistic reflection model for testing Einstein's gravity
Cosimo Bambi, Askar B. Abdikamalov, Dimitry Ayzenberg +6
Einstein's theory of general relativity was proposed over 100 years ago and has successfully passed a large number of observational tests in the weak field regime. However, the str…