Stochastic Electron Acceleration During the Near‐Infrared and X‐Ray Flares in Sagittarius 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.

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Variable and polarized emission from SgrA*

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307004930 ◽

2006 ◽

Vol 2 (S238) ◽

pp. 181-185

Author(s):

A. Eckart ◽

R. Schödel ◽

L. Meyer ◽

C. Straubmeier ◽

M. Dovčiak ◽

...

Keyword(s):

Black Hole ◽

Near Infrared ◽

Galactic Center ◽

Hot Spot ◽

Massive Black Hole ◽

X Ray ◽

Sagittarius A ◽

Polarized Emission

AbstractThe super-massive black hole in the Galactic Center (Sagittarius A*) is one of the most exciting targets in the sky. At a distance of ∼ 8 kpc it is about one hundred times closer than the second nearest nucleus of a similar galaxy, M31, and therefore the closest galactic nucleus that we can study. Here we report on the modeling of polarized near-infrared flare emission from SgrA* using a model in which a hot spot is moving on a relativistic orbit around the massive black hole. We also summarize the results from simultaneous radio/near-infrared/X-ray measurements of flare emission.

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Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sagittarius A*

Astronomy and Astrophysics ◽

10.1051/0004-6361/201015157 ◽

2011 ◽

Vol 528 ◽

pp. A140 ◽

Cited By ~ 45

Author(s):

G. Trap ◽

A. Goldwurm ◽

K. Dodds-Eden ◽

A. Weiss ◽

R. Terrier ◽

...

Keyword(s):

Near Infrared ◽

Gamma Ray ◽

X Ray ◽

Sagittarius A

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

The Astrophysical Journal ◽

10.1088/2041-8205/746/1/l10 ◽

2012 ◽

Vol 746 (1) ◽

pp. L10 ◽

Cited By ~ 44

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

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

SN Applied Sciences ◽

10.1007/s42452-021-04213-3 ◽

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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Coherence tomography with broad bandwidth extreme ultraviolet and soft X-ray radiation

Applied Physics B ◽

10.1007/s00340-021-07586-w ◽

2021 ◽

Vol 127 (4) ◽

Author(s):

S. Skruszewicz ◽

S. Fuchs ◽

J. J. Abel ◽

J. Nathanael ◽

J. Reinhard ◽

...

Keyword(s):

Optical Coherence Tomography ◽

Near Infrared ◽

Extreme Ultraviolet ◽

Infrared Light ◽

Imaging Method ◽

Optical Coherence ◽

Axial Resolution ◽

Cross Sectional ◽

X Ray ◽

Broad Bandwidth

AbstractWe present an overview of recent results on optical coherence tomography with the use of extreme ultraviolet and soft X-ray radiation (XCT). XCT is a cross-sectional imaging method that has emerged as a derivative of optical coherence tomography (OCT). In contrast to OCT, which typically uses near-infrared light, XCT utilizes broad bandwidth extreme ultraviolet (XUV) and soft X-ray (SXR) radiation (Fuchs et al in Sci Rep 6:20658, 2016). As in OCT, XCT’s axial resolution only scales with the coherence length of the light source. Thus, an axial resolution down to the nanometer range can be achieved. This is an improvement of up to three orders of magnitude in comparison to OCT. XCT measures the reflected spectrum in a common-path interferometric setup to retrieve the axial structure of nanometer-sized samples. The technique has been demonstrated with broad bandwidth XUV/SXR radiation from synchrotron facilities and recently with compact laboratory-based laser-driven sources. Axial resolutions down to 2.2 nm have been achieved experimentally. XCT has potential applications in three-dimensional imaging of silicon-based semiconductors, lithography masks, and layered structures like XUV mirrors and solar cells.

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Evaluation of swelling properties and drug release from mechanochemical pre-gelatinized glutinous rice starch matrix tablets by near infrared spectroscopy

Journal of Near Infrared Spectroscopy ◽

10.1177/0967033520982351 ◽

2021 ◽

pp. 096703352098235

Author(s):

Tomomi Takaku ◽

Yusuke Hattori ◽

Tetsuo Sasaki ◽

Tomoaki Sakamoto ◽

Makoto Otsuka

Keyword(s):

Drug Release ◽

Near Infrared ◽

Nir Spectroscopy ◽

Matrix Tablets ◽

Rice Starch ◽

Release Time ◽

Swelling Properties ◽

X Ray ◽

Glutinous Rice ◽

Pharmaceutical Properties

The effect of grinding on the pharmaceutical properties of matrix tablets consisting of ground glutinous rice starch (GRS) and theophylline (TH) was predicted by near infrared (NIR) spectroscopy. Ground GRS samples were prepared by grinding GRS in a planetary ball mill for 0-120 min, measured by X-ray diffractometry (XRD) and NIR, and then evaluated for crystallinity (%XRD) based on XRD profiles. Tablets containing TH (5 w/w%), ground GRS (94 w/w%), and magnesium stearate (1 w/w%) were formed by compression. Gel-forming and drug-release processes of the tablets were measured using a dissolution instrument with X-ray computed tomography (XCT). Swelling ratio (SWE) and mean drug-release time (MDT) were evaluated based on XCT and drug-release profiles, respectively. Calibration models for predicting percent %XRD, MDT, and SWE were constructed based on the NIR of ground GRS using partial least-squares. The results indicated the possibility of controlling the pharmaceutical properties of matrix tablets by altering the pre-gelatinization of GRS based on changes in their NIR spectra during the milling process.

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