Search Publications
Testing the Kerr Black Hole Hypothesis Using X-Ray Reflection Spectroscopy and a Thin Disk Model with Finite Thickness
Tripathi, Ashutosh; Abdikamalov, Askar B.; Ayzenberg, Dimitry +5 more
X-ray reflection spectroscopy is a powerful tool for probing the strong gravity region of black holes and can be used for testing general relativity in the strong field regime. Simplifications of the available relativistic reflection models limit the capability of performing accurate measurements of the properties of black holes. In this paper, we…
The Variable and Non-variable X-Ray Absorbers in Compton-thin Type II Active Galactic Nuclei
Nikutta, Robert; Laha, Sibasish; Markowitz, Alex G. +3 more
We have conducted an extensive X-ray spectral variability study of a sample of 20 Compton-thin type II galaxies using broadband spectra from XMM-Newton, Chandra, and Suzaku. The aim is to study the variability of the neutral intrinsic X-ray obscuration along the line of sight and investigate the properties and location of the dominant component of…
Sign of Hard-X-Ray Pulsation from the γ -Ray Binary System LS 5039
Takahashi, T.; Enoto, T.; Makishima, K. +3 more
To understand the nature of the brightest γ -ray binary system LS 5039, hard x-ray data of the object, taken with the Suzaku and NuSTAR observatories in 2007 and 2016, respectively, were analyzed. The two data sets jointly gave tentative evidence for a hard x-ray periodicity, with a period of ∼9 s and a period increase rate by ∼3 ×10-10…
Testing general relativity with x-ray reflection spectroscopy: The Konoplya-Rezzolla-Zhidenko parametrization
Tripathi, Ashutosh; Abdikamalov, Askar B.; Ayzenberg, Dimitry +6 more
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 context, the parametrically deformed black hole metrics proposed by Konoplya, Rezzolla, and Zhidenko [Phys. Rev. D 93, 064015 (2016), 10.1103/PhysRevD.93.064015] form an …
A Suzaku sample of unabsorbed narrow-line and broad-line Seyfert 1 galaxies - I. X-ray spectral properties
Gallo, L. C.; Waddell, S. G. H.
A sample of narrow-line Seyfert 1 (NLS1) and broad-line Seyfert 1 (BLS1) galaxies observed with Suzaku is presented. The final sample consists of 22 NLS1s and 47 BLS1s, for a total of 69 active galactic nuclei (AGNs) that are all at low redshift (z < 0.5) and exhibit low host-galaxy column densities (<1022 ${\rm cm}^{-2}\,$ ). The…
Application of an X-Ray Clumpy Torus Model (XCLUMPY) to 10 Obscured Active Galactic Nuclei Observed with Suzaku and NuSTAR
Tanimoto, Atsushi; Ueda, Yoshihiro; Odaka, Hirokazu +4 more
We apply XCLUMPY, an X-ray spectral model from a clumpy torus in an active galactic nucleus (AGN), to the broadband X-ray spectra of 10 obscured AGNs observed with both Suzaku and NuSTAR. The infrared spectra of these AGNs were analyzed by Ichikawa et al. with the CLUMPY code. Because XCLUMPY adopts the same clump distribution as that in the CLUMP…
A Hard Look at Local, Optically Selected, Obscured Seyfert Galaxies
Kaastra, J. S.; Stern, D.; Brandt, W. N. +11 more
We study the X-ray spectra of a sample of 19 obscured, optically selected Seyfert galaxies (Sy 1.8, 1.9, and 2) in the local universe (d ≤ 175 Mpc), drawn from the CfA Seyfert sample. Our analysis is driven by the high sensitivity of NuSTAR in the hard X-rays, coupled with soft X-ray spectra using XMM-Newton, Chandra, Suzaku, and Swift/XRT. We als…
Inverse First Ionization Potential Effects in Giant Solar Flares Found from Earth X-Ray Albedo with Suzaku/XIS
Maeda, Yoshitomo; Katsuda, Satoru; Sato, Kosuke +21 more
We report X-ray spectroscopic results for four giant solar flares that occurred on 2005 September 7 (X17.0), 2005 September 8 (X5.4), 2005 September 9 (X6.2), and 2006 December 5 (X9.0), obtained from Earth albedo data with the X-ray Imaging Spectrometer (XIS) on board Suzaku. The good energy resolution of the XIS (FWHM ∼ 100 eV) enables us to sep…
Nature of Compton-thick Active Galactic Nuclei in "Nonmerging" Luminous Infrared Galaxies UGC 2608 and NGC 5135 Revealed with Broadband X-Ray Spectroscopy
Imanishi, Masatoshi; Tanimoto, Atsushi; Ueda, Yoshihiro +4 more
We have analyzed the broadband X-ray spectra of active galactic nuclei (AGNs) in two "nonmerging" luminous infrared galaxies (LIRGs), UGC 2608 and NGC 5135, utilizing the data of Nuclear Spectroscopic Telescope Array, Suzaku, XMM-Newton, and Chandra. Applying the X-ray clumpy-torus model (XCLUMPY), we find that both sources have similar spectra ch…
Is Superorbital Modulation in SMC X-1 Caused by Absorption in a Warped Precessing Accretion Disk?
Maitra, Chandreyee; Paul, Biswajit; Pradhan, Pragati
We present a broadband spectral-timing analysis of SMC X-1 at different intensity states of its superorbital variation using 10 Suzaku and 6 Nuclear Spectroscopic Telescope Array (NuSTAR) observations. The spectrum in all the states can be described by an absorbed power law with a high-energy cutoff and a blackbody component along with an iron emi…