scholarly journals Characterizing continuum variability in the radio-loud narrow-line Seyfert 1 galaxy IRAS 17020+4544

2020 ◽  
Vol 496 (3) ◽  
pp. 3708-3724 ◽  
Author(s):  
A G Gonzalez ◽  
L C Gallo ◽  
P Kosec ◽  
A C Fabian ◽  
W N Alston ◽  
...  
Keyword(s):  
Recent Observation ◽  
Temporal Analysis ◽  
Narrow Line ◽  
Soft State ◽  
Spectral Components ◽  
Low Energies ◽  
Show Evidence ◽  
Variable Power ◽  
Reflection Component ◽  
Spectral State

ABSTRACT We present results of temporal and spectral analyses on four XMM–Newton EPIC pn observations of IRAS 17020+4544, a narrow-line Seyfert 1 galaxy with evidence of a radio jet. Analysis of the light curves reveals that this radio-loud source does not behave like the bulk population of its radio-quiet counterparts. A trend of spectral hardening with increased flux is found. Variability is found to increase with energy, though it decreases as the spectrum hardens. The first 40 ks of the most recent observation behave uniquely among the epochs, exhibiting a softer spectral state than at any other time. Possible non-stationarity at low energies is found, with no such effect present at higher energies, suggesting at least two distinct spectral components. A reverberation signature is confirmed, with the lag-frequency, lag-energy, and covariance spectra changing significantly during the soft-state epoch. The temporal analysis suggests a variable power law in the presence of a reflection component, thus motivating such a fit for the 0.3−10 keV EPIC pn spectra from all epochs. We find an acceptable spectral fit using the timing-motivated parameters and report the detection of a broad Fe K emission line, requiring an additional model component beyond the reflection spectrum. We discuss links between this source and other narrow-line Seyfert 1 sources that show evidence of jet activity, finding similarities among this currently very limited sample of interesting objects.

scholarly journals Broadband spectral analysis of MXB 1659−298 in its soft and hard state

2019 ◽  
Vol 630 ◽  
pp. A138
Author(s):  
R. Iaria ◽  
S. M. Mazzola ◽  
T. Bassi ◽  
A. F. Gambino ◽  
A. Marino ◽  
...  
Keyword(s):  
Absorption Lines ◽  
X Ray ◽  
Direct Emission ◽  
Broadband Spectrum ◽  
Hydrogen Column Density ◽  
Soft State ◽  
Transient Sources ◽  
Hard State ◽  
Reflection Component ◽  
Spectral State

Context. The X-ray transient eclipsing source MXB 1659−298 went into outburst in 1999 and 2015. During these two outbursts the source was observed by XMM-Newton, NuSTAR, and Swift/XRT. Aims. Using these observations, we studied the broadband spectrum of the source to constrain the continuum components and to verify whether it had a reflection component, as is observed in other X-ray eclipsing transient sources. Methods. We combined the available spectra to study the soft and hard state of the source in the 0.45–55 keV energy range. Results. We report a reflection component in the soft and hard state. The direct emission in the soft state can be modeled with a thermal component originating from the inner accretion disk plus a Comptonized component associated with an optically thick corona surrounding the neutron star. On the other hand, the direct emission in the hard state is described only by a Comptonized component with a temperature higher than 130 keV; this component is associated with an optically thin corona. We observed narrow absorption lines from highly ionized ions of oxygen, neon, and iron in the soft spectral state. We investigated where the narrow absorption lines form in the ionized absorber. The equivalent hydrogen column density associated with the absorber is close to 6 × 1023 cm−2 and 1.3 × 1023 cm−2 in the soft and hard state, respectively.

scholarly journals Properties of Faint X-ray Activity of XTE J1908+094 in 2019

Galaxies ◽  
2021 ◽  
Vol 9 (2) ◽  
pp. 25
Author(s):  
Debjit Chatterjee ◽  
Arghajit Jana ◽  
Kaushik Chatterjee ◽  
Riya Bhowmick ◽  
Sujoy Kumar Nath ◽  
...  
Keyword(s):  
Black Hole ◽  
Temporal Analysis ◽  
Power Density Spectrum ◽  
Periodic Oscillations ◽  
Telescope Array ◽  
Density Spectrum ◽  
X Ray ◽  
Black Hole Candidate ◽  
Short Period ◽  
Spectral State

We study the properties of the faint X-ray activity of Galactic transient black hole candidate XTE J1908+094 during its 2019 outburst. Here, we report the results of detailed spectral and temporal analysis during this outburst using observations from Nuclear Spectroscopic Telescope Array (NuSTAR). We have not observed any quasi-periodic-oscillations (QPOs) in the power density spectrum (PDS). The spectral study suggests that the source remained in the softer (more precisely, in the soft–intermediate) spectral state during this short period of X-ray activity. We notice a faint but broad Fe Kα emission line at around 6.5 keV. We also estimate the probable mass of the black hole to be 6.5−0.7+0.5M⊙, with 90% confidence.

scholarly journals Fusion hindrance in light and heavy systems

2019 ◽  
Vol 223 ◽  
pp. 01041
Author(s):  
Giovanna Montagnoli
Keyword(s):  
Theoretical Work ◽  
Heavy Ion ◽  
General Phenomenon ◽  
Quantitative Evidence ◽  
Coupled Channels ◽  
S Factor ◽  
Low Energies ◽  
Show Evidence ◽  
Heavy Ion Fusion ◽  
Transfer Channels

The phenomenon of hindrance in sub-barrier heavy-ion fusion has been confirmed by several experimentalevidences and it is now recognised as a general phenomenon of heavy-ion fusion process. In many cases the signature of fusion hindrance lies in the trend of the logarithmic slope of the excitation function and of the S factor at low energies. The comparison with stadard Coupled-Channels calculations is a more quantitative evidence for its existence. In many medium-heavy systems the hindrance effect has been recognised with different features depending on the various couplings to the inelastic and transfer channels. Different theoretical appro ches have been proposed to explain the hindrance but the underlying physics is still a matter of debate. Hindrance is observed in light systems, independent of the sign of the fusion Q-value, with different features. In the case of the 12C + 30Si system the effect is smallbut it is clearly observed. Near-by cases show evidence for systematic behaviours. A very recent experiment has concerned the lighter case 12C + 24Mg where hindrance shows up clearly, because a maximum of the S factor appears already at a relatively high cross section σ=1.6mb. The consequences for the dynamics of stellar evolution have to be clarified by further experimental and theoretical work.

Multiwavelength Monitoring of the Narrow‐Line Seyfert 1 Galaxy Arakelian 564. I.ASCAObservations and the Variability of the X‐Ray Spectral Components

2001 ◽  
Vol 561 (1) ◽  
pp. 131-145 ◽  
Author(s):  
T. J. Turner ◽  
P. Romano ◽  
I. M. George ◽  
R. Edelson ◽  
S. J. Collier ◽  
...  
Keyword(s):  
Narrow Line ◽  
X Ray ◽  
Spectral Components

scholarly journals Reflection component in the Bright Atoll Source GX 9+9

2020 ◽  
Vol 635 ◽  
pp. A209
Author(s):  
R. Iaria ◽  
S. M. Mazzola ◽  
T. Di Salvo ◽  
A. Marino ◽  
A. F. Gambino ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Optical Depth ◽  
Color Temperature ◽  
Equivalent Model ◽  
Western Model ◽  
Broadband Spectrum ◽  
Soft State ◽  
Low Mass ◽  
Reflection Component ◽  
Innermost Region

Context. GX 9+9 (4U 1728−16) is a low mass X-ray binary source harboring a neutron star. Although it belongs to the subclass of the bright Atoll sources together with GX 9+1, GX 3+1, and GX 13+1, its broadband spectrum is poorly studied and apparently does not show reflection features in the spectrum. Aims. To constrain the continuum well and verify whether a relativistic smeared reflection component is present, we analyze the broadband spectrum of GX 9+9 using BeppoSAX and XMM-Newton spectra covering the 0.3−40 keV energy band. Methods. We fit the spectrum adopting a model composed of a disk-blackbody plus a Comptonized component whose seed photons have a blackbody spectrum (Eastern Model). A statistically equivalent model is composed of a Comptonized component whose seed photons have a disk-blackbody distribution plus a blackbody that mimics a saturated Comptonization likely associated with a boundary layer (Western model). Other trials did not return a good fit. Results. The spectrum of GX 9+9 was observed in a soft state and its luminosity is 2.3 × 1037 erg s−1 assuming a distance to the source of 5 kpc. In the Eastern Model scenario, we find the seed-photon temperature and electron temperature of the Comptonized component to be 1.14−0.07+0.10 keV and 2.80−0.04+0.09 keV, respectively, while the optical depth of the Comptonizing corona is 8.9 ± 0.4. The color temperature of the inner accretion disk is 0.86−0.02+0.08 keV and 0.82 ± 0.02 keV for the BeppoSAX and XMM-Newton spectrum, respectively. In the Western Model scenario, instead, we find that the seed-photon temperature is 0.87 ± 0.07 keV and 1.01 ± 0.08 keV for the BeppoSAX and XMM-Newton spectrum, respectively. The electron temperature of the Comptonized component is 2.9 ± 0.2 keV, while the optical depth is 9.4−1.1+1.5. The blackbody temperature is 1.79−0.18+0.09 keV and 1.85−0.15+0.07 keV for the BeppoSAX and XMM-Newton spectrum, respectively. The addition of a relativistic smeared reflection component improved the fit in both the scenarios, giving compatible values of the parameters, even though a significant broad emission line in the Fe-K region is not observed. Conclusions. From the reflection component we estimated an inclination angle of about 43−4+6 deg and 51−2+9 deg for the Eastern and Western Model, respectively. The value of the reflection fraction Ω/2π is 0.18 ± 0.04 and 0.21 ± 0.03 for the Eastern and Western Model, respectively, suggesting that the Comptonized corona should be compact and close to the innermost region of the system.

Neurophysiologic Basis for Cochlear and Auditory Brainstem Implants

2001 ◽  
Vol 10 (2) ◽  
pp. 68-77 ◽  
Author(s):  
Aage R. Møller
Keyword(s):  
Cochlear Implants ◽  
Auditory System ◽  
Temporal Structure ◽  
Temporal Analysis ◽  
Auditory Brainstem ◽  
Speech Discrimination ◽  
Complex Sounds ◽  
Frequency Bands ◽  
Spectral Components ◽  
Auditory Brainstem Implants

The physiologic basis for cochlear and brainstem implants is discussed. It is concluded that the success of cochlear implants may be explained by assuming that the auditory system can adequately discriminate complex sounds, such as speech sounds, on the basis of their temporal structure when that is encoded in a few separate frequency bands to offer moderate separation of spectral components. The most important roles of the cochlea seems to be to prepare complex sounds for temporal analysis and to create separate channels through which information in different frequency bands is transmitted separately to higher nervous centers for decoding of temporal information. It is then pertinent to ask how many channels are needed. Because speech discrimination is very important, it is probably sufficient to use enough channels to separate formants from each other.

scholarly journals ANALYSES OF MULTI-YEAR SYNTHETIC APERTURE RADAR IMAGERY OF DRY-FALLEN INTERTIDAL FLATS

2015 ◽  
Vol XL-7/W3 ◽  
pp. 941-947 ◽  
Author(s):  
M. Gade ◽  
S. Melchionna ◽  
L. Kemme
Keyword(s):  
Synthetic Aperture Radar ◽  
Morphological Changes ◽  
Temporal Analysis ◽  
Synthetic Aperture ◽  
Mussel Beds ◽  
Intertidal Flats ◽  
Show Evidence ◽  
Radar Imagery ◽  
Sar Imagery ◽  
Aperture Radar

We analyzed a great deal of high-resolution Synthetic Aperture Radar (SAR) data of dry-fallen intertidal flats in the German Wadden Sea with respect to the imaging of sediments, macrophytes, and mussels. TerraSAR-X and Radarsat-2 images of five test areas along the German North Sea coast acquired between 2008 and 2013 form the basis for the present investigation and are used to demonstrate that pairs of SAR images, if combined through basic algebraic operations, can already provide useful indicators for morphological changes and for bivalve (oyster and mussel) beds. Depending on the type of sediment, but also on the water level and on environmental conditions (wind speed) exposed sediments may show up on SAR imagery as areas of enhanced, or reduced, radar backscattering. The (multi-temporal) analysis of series of such images allows for the detection of mussel beds, and our results show evidence that also single-acquisition, multi-polarization SAR imagery can be used for that purpose.

scholarly journals The origin of X-ray emission in the gamma-ray emitting narrow-line Seyfert 1 1H 0323+342

2020 ◽  
Vol 496 (3) ◽  
pp. 2922-2931 ◽  
Author(s):  
Sergio A Mundo ◽  
Erin Kara ◽  
Edward M Cackett ◽  
A C Fabian ◽  
J Jiang ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Broad Band ◽  
Band Spectrum ◽  
Narrow Line ◽  
Model Assumption ◽  
X Ray ◽  
Disc Model ◽  
Reflection Model ◽  
Superluminal Motion ◽  
Low Energies

ABSTRACT We present the results of X-ray spectral and timing analyses of the closest gamma-ray emitting narrow-line Seyfert 1 (γ-NLS1) galaxy, 1H 0323+342. We use observations from a recent, simultaneous XMM–Newton/NuSTAR campaign. As in radio-quiet NLS1s, the spectrum reveals a soft excess at low energies (≲2 keV) and reflection features such as a broad iron K emission line. We also find evidence of a hard excess at energies above ∼35 keV that is likely a consequence of jet emission. Our analysis shows that relativistic reflection is statistically required, and using a combination of models that includes the reflection model relxill for the broad-band spectrum, we find an inclination of $i=63^{+7}_{-5}$ degrees, which is in tension with much lower values inferred by superluminal motion in radio observations. We also find a flat (q = 2.2 ± 0.3) emissivity profile, implying that there is more reflected flux than usual being emitted from the outer regions of the disc, which in turn suggests a deviation from the thin disc model assumption. We discuss possible reasons for this, such as reflection off of a thick accretion disc geometry.

scholarly journals A broadband spectral analysis of 4U 1702-429 using XMM-Newton and BeppoSAX data

2019 ◽  
Vol 621 ◽  
pp. A89 ◽  
Author(s):  
S. M. Mazzola ◽  
R. Iaria ◽  
T. Di Salvo ◽  
M. Del Santo ◽  
A. Sanna ◽  
...  
Keyword(s):  
Binary Systems ◽  
Integral Spectrum ◽  
X Ray ◽  
Broadband Spectrum ◽  
Soft State ◽  
Hard State ◽  
Low Mass ◽  
Reflection Component ◽  
Innermost Region ◽  
Integral Observation

Context. Most of the X-ray binary systems containing neutron stars classified as Atoll sources show two different spectral states, referred to as soft and hard. Moreover, a large number of these systems show a reflection component relativistically smeared in their spectra, which provides information on the innermost region of the system. Aims. Our aim is to investigate the poorly studied broadband spectrum of the low-mass X-ray binary system 4U 1702-429, which was recently analysed combining XMM-Newton and INTEGRAL data. The peculiar value of the reflection fraction brought us to analyse further broadband spectra of 4U 1702-429. Methods. We re-analysed the spectrum of the XMM-Newton/INTEGRAL observation of 4U 1702-429 in the 0.3–60 keV energy range and we extracted three 0.1–100 keV spectra of the source analysing three observations collected with the BeppoSAX satellite. Results. We find that the XMM-Newton/INTEGRAL spectrum is well fitted using a model composed of a disc blackbody plus a Comptonised component and a smeared reflection component. We used the same spectral model for the BeppoSAX spectra, finding that the addition of a smeared reflection component is statistically significant. The best-fit values of the parameters are compatible to each other for the BeppoSAX spectra. We find that the reflection fraction is 0.05−0.01+0.3 for the XMM-Newton/INTEGRAL spectrum and between 0.15 and 0.4 for the BeppoSAX ones. Conclusions. The relative reflection fraction and the ionisation parameter are incompatible between the XMM-Newton/INTEGRAL and the BeppoSAX observations and the characteristics of the Comptonising corona suggest that the source was in a soft state in the former observation and in a hard state in the latter.

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