scholarly journals NEAR-INFRARED AND X-RAY QUASI-PERIODIC OSCILLATIONS IN NUMERICAL MODELS OF Sgr A*

2012 ◽  
Vol 746 (1) ◽  
pp. L10 ◽  
Author(s):  
Joshua C. Dolence ◽  
Charles F. Gammie ◽  
Hotaka Shiokawa ◽  
Scott C. Noble
Keyword(s):  
Near Infrared ◽  
Numerical Models ◽  
Periodic Oscillations ◽  
X Ray ◽  
Sgr A

scholarly journals Possible Detection of Quasi-Periodic Oscillations from Sgr A* at 43 GHz

2016 ◽  
Vol 11 (S322) ◽  
pp. 50-51
Author(s):  
Yuhei Iwata ◽  
Tomoharu Oka ◽  
Makoto Miyoshi
Keyword(s):  
Indirect Evidence ◽  
Two Dimensional ◽  
Resonant Oscillation ◽  
Periodic Oscillations ◽  
Gaussian Shape ◽  
X Ray ◽  
Long Baseline ◽  
Spin Parameter ◽  
Sgr A ◽  
Very Long Baseline Array

AbstractQuasi-periodic oscillations (QPOs) are believed to be indirect evidence for black holes. Several authors have reported detections of QPOs from Sgr A*, the nucleus of our Galaxy, in infrared and X-ray wavelength during flare-ups. Miyoshi et al. (2011) reported a tentative detection of QPOs in the 43 GHz light curve of Sgr A* obtained with the Very Long Baseline Array (VLBA). To confirm their detection, we reanalysed their VLBA data very conservatively. The 43 GHz flux was calculated for every 15 seconds by assuming a two-dimensional Gaussian-shape spatial structure. The Lomb-Scargle periodogram of the 43 GHz flux just after a millimeter wave flare of Sgr A*, shows three apparent peaks at 10.2, 14.6 and 32.1 min. Two of them are barely consistent with the previously reported QPOs. Using the resonant oscillation model, we estimated the spin parameter of the Sgr A* black hole to be 0.56 assuming the mass of 4.3 × 106M⊙.

scholarly journals Detection of millihertz quasi-periodic oscillations in the X-Ray binary 1RXS J180408.9−342058

2020 ◽  
Vol 500 (1) ◽  
pp. 34-39
Author(s):  
Kaho Tse ◽  
Duncan K Galloway ◽  
Yi Chou ◽  
Alexander Heger ◽  
Hung-En Hsieh
Keyword(s):  
Neutron Star ◽  
Power Law ◽  
Numerical Models ◽  
Periodic Oscillations ◽  
X Ray ◽  
Thermonuclear Burning ◽  
Low Mass ◽  
Power Law Noise ◽  
Star Surface ◽  
X Ray Binaries

ABSTRACT Millihertz quasi-periodic oscillations (mHz QPOs) observed in neutron-star low-mass X-ray binaries (NS LMXBs) are generally explained as marginally stable thermonuclear burning on the neutron star surface. We report the discovery of mHz QPOs in an XMM–Newton observation of the transient 1RXS J180408.9−342058, during a regular bursting phase of its 2015 outburst. We found significant periodic signals in the March observation, with frequencies in the range 5–8 $\, \mathrm{mHz}$, superimposed on a strong ∼1/f power-law noise continuum. Neither the QPO signals nor the power-law noise were present during the April observation, which exhibited a 2.5 × higher luminosity and had correspondingly more frequent bursts. When present, the QPO signal power decreases during bursts and disappears afterwards, similar to the behaviour in other sources. 1RXS J180408.9−342058 is the eighth source known to date that exhibits such QPOs driven by thermonuclear burning. We examine the range of properties of the QPO signals in different sources. Whereas the observed oscillation profile is similar to that predicted by numerical models, the amplitudes are significantly higher, challenging their explanation as originating from marginally stable burning.

scholarly journals Scale-invariance of black hole accretion: modelling emission from a black hole X-ray binary with relativistic accretion flow simulations

2019 ◽  
Vol 490 (4) ◽  
pp. 5353-5358
Author(s):  
M Mościbrodzka
Keyword(s):  
Black Hole ◽  
Near Infrared ◽  
Thermal Emission ◽  
Broad Band ◽  
Scale Invariant ◽  
X Ray ◽  
Accretion Flow ◽  
Black Hole Accretion ◽  
Sgr A ◽  
Hole Accretion

ABSTRACT We model the non-thermal emission spectrum of the extremely sub-Eddington X-ray binary system A0620-00. It is believed that this non-thermal emission is produced by radiatively inefficient ‘quiescent’ accretion on to a stellar-mass black hole present in the system. We post-process general relativistic magnetohydrodynamics (GRMHD) simulations with multiwavelength, fully polarized, relativistic radiative transfer calculations to predict broad-band spectra and emission polarization levels for a range of electron models and accretion rates. We find that a model with strong coupling of electrons and ions in the accretion disc and accretion rate of only $\dot{M}=3\times 10^{-13} \, \rm [M_\odot \, yr^{-1}]$ is able to recover the observed X-ray spectral slope, as well as the excess of linear polarization detected in the source in the near-infrared (NIR)/optical bands. Our models constrain the spectral properties of a putative relativistic jet produced in this system. In addition, we show that the magnetized winds from our hot accretion flow carry away a small fraction of the orbital angular momentum of the binary, which is unable to explain the observed rapid orbital decay of the system. GRMHD simulations similar to the present ones are often used to explain emission from sub-Eddington supermassive black holes in Sgr A* or M87; the present simulations allow us to test whether some aspects of quiescent black hole accretion are scale-invariant.

scholarly journals General relativistic MHD simulations of non-thermal flaring in Sagittarius A*

2021 ◽  
Author(s):  
K Chatterjee ◽  
S Markoff ◽  
J Neilsen ◽  
Z Younsi ◽  
G Witzel ◽  
...  
Keyword(s):  
Particle Acceleration ◽  
Near Infrared ◽  
Power Spectra ◽  
X Rays ◽  
Thermal Electron ◽  
X Ray ◽  
Particle Distributions ◽  
Accretion Flows ◽  
General Relativistic ◽  
Sgr A

Abstract Sgr A* exhibits regular variability in its multiwavelength emission, including daily X-ray flares and roughly continuous near-infrared (NIR) flickering. The origin of this variability is still ambiguous since both inverse Compton and synchrotron emission are possible radiative mechanisms. The underlying particle distributions are also not well constrained, particularly the non-thermal contribution. In this work, we employ the GPU-accelerated general relativistic magnetohydrodynamics (GRMHD) code H-AMR to perform a study of flare flux distributions, including the effect of particle acceleration for the first time in high-resolution 3D simulations of Sgr A*. For the particle acceleration, we use the general relativistic ray-tracing (GRRT) code BHOSS to perform the radiative transfer, assuming a hybrid thermal+non-thermal electron energy distribution. We extract ∼60 hr lightcurves in the sub-millimetre, NIR and X-ray wavebands, and compare the power spectra and the cumulative flux distributions of the lightcurves to statistical descriptions for Sgr A* flares. Our results indicate that non-thermal populations of electrons arising from turbulence-driven reconnection in weakly magnetised accretion flows lead to moderate NIR and X-ray flares and reasonably describe the X-ray flux distribution while fulfilling multiwavelength flux constraints. These models exhibit high rms per cent amplitudes, $\gtrsim 150{{\ \rm per\ cent}}$ both in the NIR and the X-rays, with changes in the accretion rate driving the 230 GHz flux variability, in agreement with Sgr A* observations.

scholarly journals Continuation of the X-ray monitoring of Sgr A*: the increase in bright flaring rate confirmed

2020 ◽  
Vol 636 ◽  
pp. A25
Author(s):  
E. Mossoux ◽  
B. Finociety ◽  
J.-M. Beckers ◽  
F. H. Vincent
Keyword(s):  
Black Hole ◽  
Near Infrared ◽  
Milky Way ◽  
Detection Efficiency ◽  
Previous Method ◽  
Arrival Times ◽  
X Ray ◽  
Sagittarius A ◽  
Block Algorithm ◽  
Sgr A

Context. The supermassive black hole Sagittarius A* (Sgr A*) is located at the dynamical center of the Milky Way. In a recent study of the X-ray flaring activity from Sgr A* using Chandra, XMM-Newton, and Swift observations from 1999 to 2015, it has been argued that the bright flaring rate has increased from 2014 August 31 while the faint flaring rate decreased from around 2013 August. Aims. We tested the persistence of these changes in the flaring rates with new X-ray observations of Sgr A* performed from 2016 to 2018 (total exposure of 1.4 Ms). Methods. We reprocessed the Chandra, XMM-Newton, and Swift observations from 2016 to 2018. We detected 9 flares in the Chandra data and 5 flares in the Swift data that we added to the set of 107 previously detected flares. We computed the intrinsic distribution of flare fluxes and durations corrected for the sensitivity bias using a new method that allowed us to take the error on the flare fluxes and durations into account. From this intrinsic distribution, we determined the average flare detection efficiency for each Chandra, XMM-Newton, and Swift observation. After correcting each observational exposure for this efficiency, we applied the Bayesian blocks algorithm on the concatenated flare arrival times. As in the above-mentioned study, we also searched for a flux and fluence threshold that might lead to a change in flaring rate. We improved the previous method by computing the average flare detection efficiencies for each flux and fluence range. Results. The Bayesian block algorithm did not detect any significant change in flaring rate of the 121 flares. However, we detected an increase by a factor of about three in the flaring rate of the most luminous and most energetic flares that have occurred since 2014 August 30. Conclusions. The X-ray activity of Sgr A* has increased for more than four years. Additional studies about the overall near-infrared and radio behavior of Sgr A* are required to draw strong results on the multiwavelength activity of the black hole.

Lense‐Thirring Precession and Quasi‐periodic Oscillations in X‐Ray Binaries

1998 ◽  
Vol 507 (1) ◽  
pp. 316-326 ◽  
Author(s):  
Dragoljub Marković ◽  
Frederick K. Lamb
Keyword(s):  
Periodic Oscillations ◽  
X Ray ◽  
X Ray Binaries

scholarly journals Phase lags of quasi-periodic oscillations across source states in the low-mass X-ray binary 4U 1636–53

2016 ◽  
Vol 461 (1) ◽  
pp. 79-92 ◽  
Author(s):  
Marcio G. B. de Avellar ◽  
Mariano Méndez ◽  
Diego Altamirano ◽  
Andrea Sanna ◽  
Guobao Zhang
Keyword(s):  
Periodic Oscillations ◽  
X Ray ◽  
Phase Lags ◽  
Low Mass

scholarly journals Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*

2016 ◽  
Vol 461 (1) ◽  
pp. 552-559 ◽  
Author(s):  
S. Dibi ◽  
S. Markoff ◽  
R. Belmont ◽  
J. Malzac ◽  
J. Neilsen ◽  
...  
Keyword(s):  
Event Horizon ◽  
X Ray ◽  
Sgr A

scholarly journals Characterization and mapping of hematite ore mineral classes using hyperspectral remote sensing technique: a case study from Bailadila iron ore mining region

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Ibrahim Shaik ◽  
S. K. Begum ◽  
P. V. Nagamani ◽  
Narayan Kayet
Keyword(s):  
Infrared Absorption ◽  
Near Infrared ◽  
Spectral Feature ◽  
Absorption Feature ◽  
X Ray ◽  
Remote Sensing Technique ◽  
Ore Minerals ◽  
Feature Fitting ◽  
Hematite Ore

AbstractThe study demonstrates a methodology for mapping various hematite ore classes based on their reflectance and absorption spectra, using Hyperion satellite imagery. Substantial validation is carried out, using the spectral feature fitting technique, with the field spectra measured over the Bailadila hill range in Chhattisgarh State in India. The results of the study showed a good correlation between the concentration of iron oxide with the depth of the near-infrared absorption feature (R2 = 0.843) and the width of the near-infrared absorption feature (R2 = 0.812) through different empirical models, with a root-mean-square error (RMSE) between < 0.317 and < 0.409. The overall accuracy of the study is 88.2% with a Kappa coefficient value of 0.81. Geochemical analysis and X-ray fluorescence (XRF) of field ore samples are performed to ensure different classes of hematite ore minerals. Results showed a high content of Fe > 60 wt% in most of the hematite ore samples, except banded hematite quartzite (BHQ) (< 47 wt%).

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