scholarly journals Rapid X-Ray Variability and The FE II Problem in I Zw 1 Objects

1994 ◽  
Vol 161 ◽  
pp. 660-661
Author(s):  
Th. Boller ◽  
J. Trümper ◽  
S. Molendi ◽  
S. Schaeidt ◽  
H. Fink
Keyword(s):  
Spectral Analysis ◽  
Accretion Disk ◽  
Energy Band ◽  
Optical Spectrum ◽  
Seyfert Galaxies ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Compact Region ◽  
First Time

X-ray variability in the 0.1–2.4 keV ROSAT energy band with a doubling timescale of 800 s and a factor of 4 within a few hours has been detected in a 20 ksec pointing on the IRAS AGN 13224-3809. The optical spectrum indicates that IRAS 13224-3809 is a narrow-line Seyfert 1 galaxy with strong permitted Fe II emission, a member of the unusual I Zw 1 class objects. IRAS 13224-3809 appears to be one of the most rapidly variable AGN known so far. This is the first time that variability on a timescale smaller than 1000 s is reported at such high L (0.1–2.4 keV) = 3·1044 erg · s−1 X-ray luminosity in Seyfert galaxies. It is also the first reported X-ray variability in I Zw 1 class objects. The δt = 800 s variation indicates that the X-rays come from a compact region of about 17 light minutes in size. Our results from the X-ray spectral analysis favour a scenario in which a hard X-ray source irradiates the accretion disk which reemits at soft X-ray energies. The absence of broad H I wings can be explained if only a part of the BLR, far from the centre, is observed and the bulk of the region, which emits the wings, is hidden. We want to draw attention to the fact that rapid X-ray variability could also be connected with the absence of broad H I lines in IRAS 13224-3809.

scholarly journals Optical Short-Time Variations in GK Persei during the 1983 Outburst

1987 ◽  
Vol 93 ◽  
pp. 485-485
Author(s):  
H. Steinle ◽  
W. Pietsck
Keyword(s):  
Accretion Disk ◽  
Time Resolution ◽  
X Rays ◽  
X Ray ◽  
Time Variations ◽  
Short Time ◽  
First Time ◽  
Calar Alto

AbstractDuring the August 1983 outburst of the old nova GK Persei observations with EXOSAT showed for the first time a 351 second periodicity in X-rays.Our fast photometry (U(B)V with 25 sec time resolution) was made at the end of the outburst in the nights of September 29 , and October 1–3 , using the 2.2 meter telescope at Calar Alto (Spain).Optical variations up to 10% in U and 4% in V with periodicities in the range 350 to 360 seconds were found, lasting only for few cycles.A comparison with the extrapolated prediction of the X-ray maxima did not show a coincidence, but rather an anticoincidence in several cases. This supports a model of reprocessed X-rays at the inner edge of an accretion disk.

scholarly journals X-rays from the mode-switching PSR B0943+10

2017 ◽  
Vol 13 (S337) ◽  
pp. 62-65 ◽  
Author(s):  
S. Mereghetti ◽  
L. Kuiper ◽  
A. Tiengo ◽  
J. Hessels ◽  
W. Hermsen ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Thermal Emission ◽  
Mode Switching ◽  
X Rays ◽  
Radio Telescopes ◽  
Polar Cap ◽  
Radio Observations ◽  
X Ray ◽  
First Time

AbstractNew simultaneous X-ray and radio observations of the archetypal mode-switching pulsar PSR B0943+10 have been carried out with XMM-Newton and the LOFAR, LWA and Arecibo radio telescopes in November 2014. They allowed us to better constrain the X-ray spectral and variability properties of this pulsar and to detect, for the first time, the X-ray pulsations also during the X-ray-fainter mode. The combined timing and spectral analysis indicates that unpulsed non-thermal emission, likely of magnetospheric origin, and pulsed thermal emission from a small polar cap are present during both radio modes and vary in a correlated way.

scholarly journals Strong Soft X-ray Emission and High Accretion Rates in Seyfert Galaxies

1997 ◽  
Vol 163 ◽  
pp. 812-813 ◽  
Author(s):  
Ewa Szuszkiewicz
Keyword(s):  
Accretion Disk ◽  
Seyfert Galaxies ◽  
Narrow Line ◽  
Natural Explanation ◽  
X Ray ◽  
Accretion Rates

AbstractSlim accretion disk models with high accretion rates provide a natural explanation for the strong soft X-ray emission observed in several narrow–line Seyfert 1 galaxies.

scholarly journals Broadband X-ray observations of four gamma-ray narrow-line Seyfert 1 galaxies

2019 ◽  
Vol 632 ◽  
pp. A120 ◽  
Author(s):  
M. Berton ◽  
V. Braito ◽  
S. Mathur ◽  
L. Foschini ◽  
E. Piconcelli ◽  
...  
Keyword(s):  
Accretion Disk ◽  
Gamma Ray ◽  
High Energy ◽  
Time Variability ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Relativistic Jet ◽  
Line Region ◽  
Spectrum Radio

Narrow-line Seyfert 1 galaxies (NLS1s) is one of the few classes of active galactic nuclei harboring powerful relativistic jets and detected in γ-rays. NLS1s are well-known X-ray sources. While in non-jetted sources the origin of this X-ray emission may be a hot corona surrounding the accretion disk, in jetted objects, especially beamed ones, the contribution of corona and relativistic jet is difficult to disentangle without a proper sampling of the hard X-ray emission. For this reason, we observed with NuSTAR the first four NLS1s detected at high energy γ-rays. These data, along with XMM-Newton and Swift/XRT observations, confirmed that X-rays originate both in the jet and in the accretion disk corona. Time variability in hard X-rays furthermore suggests that, as observed in flat-spectrum radio quasars, the dissipation region during flares could change its position from source to source, and it can be located both inside and outside the broad-line region. We find that jetted NLS1s, and other blazars as well, seem not to follow the classical fundamental plane of black hole (BH) activity, which therefore should be used as a BH mass estimator in blazars with extreme care only. Our results strengthen the idea according to which γ-NLS1s are smaller and younger version of flat-spectrum radio quasars, in which both a Seyfert and a blazar component co-exist.

scholarly journals Observations of X-rays from Laboratory Sparks in Air at Atmospheric Pressure under Negative Switching Impulse Voltages

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 169 ◽  
Author(s):  
Mahbubur Rahman ◽  
Pasan Hettiarachchi ◽  
Vernon Cooray ◽  
Joseph Dwyer ◽  
Vladimir Rakov ◽  
...  
Keyword(s):  
Rise Time ◽  
Atmospheric Pressure ◽  
Opposite Polarity ◽  
X Rays ◽  
X Ray ◽  
Impulse Voltage ◽  
First Time ◽  
Switching Impulses ◽  
Low Rate

We present observations of X-rays from laboratory sparks created in the air at atmospheric pressure by applying an impulse voltage with long (250 µs) rise-time. X-ray production in 35 and 46 cm gaps for three different electrode configurations was studied. The results demonstrate, for the first time, the production of X-rays in gaps subjected to switching impulses. The low rate of rise of the voltage in switching impulses does not significantly reduce the production of X-rays. Additionally, the timing of the X-ray occurrence suggests the possibility that the mechanism of X-ray production by sparks is related to the collision of streamers of opposite polarity.

Mesoscopic structure of SiC fibers by neutron and x-ray scattering

1996 ◽  
Vol 11 (5) ◽  
pp. 1169-1178 ◽  
Author(s):  
Kentaro Suzuya ◽  
Michihiro Furusaka ◽  
Noboru Watanabe ◽  
Makoto Osawa ◽  
Kiyohito Okamura ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Volume Fraction ◽  
X Rays ◽  
X Ray ◽  
Sic Fibers ◽  
X Ray Scattering ◽  
Mesoscopic Structure ◽  
Angle Scattering ◽  
Momentum Transfer Range ◽  
First Time

Mesoscopic structures of SiC fibers produced from polycarbosilane by different methods were studied by diffraction and small-angle scattering of neutrons and x-rays. Microvoids of a size of 4–10 Å in diameter have been observed for the first time by neutron scattering in a medium momentum transfer range (Q = 0.1–1.0 Å−1). The size and the volume fraction of β–SiC particles were determined for fibers prepared at different heat-treatment temperatures. The results show that wide-angle neutron scattering measurements are especially useful for the study of the mesoscopic structure of multicomponent materials.

scholarly journals Limits on mass outflow from optical tidal disruption events

2021 ◽  
Vol 502 (3) ◽  
pp. 3385-3393
Author(s):  
Tatsuya Matsumoto ◽  
Tsvi Piran
Keyword(s):  
Energy Band ◽  
New Method ◽  
Hydrodynamic Modelling ◽  
X Rays ◽  
Will Emit ◽  
Tidal Disruption ◽  
X Ray ◽  
Mass Outflow ◽  
Current Sample ◽  
Stellar Masses

ABSTRACT The discovery of optical/UV (ultraviolet) tidal disruption events (TDEs) was surprising. The expectation was that, upon returning to the pericentre, the stellar-debris stream will form a compact disc that will emit soft X-rays. Indeed, the first TDEs were discovered in this energy band. A common explanation for the optical/UV events is that surrounding optically thick matter reprocesses the disc’s X-ray emission and emits it from a large photosphere. If accretion follows the super-Eddington mass infall rate, it would inevitably result in an energetic outflow, providing naturally the reprocessing matter. We describe here a new method to estimate, using the observed luminosity and temperature, the mass and energy of outflows from optical transients. When applying this method to a sample of supernovae, our estimates are consistent with a more detailed hydrodynamic modelling. For the current sample of a few dozen optical TDEs, the observed luminosity and temperature imply outflows that are significantly more massive than typical stellar masses, posing a problem to this common reprocessing picture.

scholarly journals X-Ray Aspects of the IRAS Galaxies

1998 ◽  
Vol 188 ◽  
pp. 145-148
Author(s):  
E.J.A. Meurs
Keyword(s):  
Stellar Evolution ◽  
Seyfert Galaxies ◽  
Temporal Variations ◽  
Spectral Studies ◽  
X Rays ◽  
X Ray ◽  
Active Core

Several IRAS galaxies have been detected at X-rays, with a variety of satellite observatories. About half of these are classified optically as Seyfert galaxies. Among those not (convincingly) classified as AGN, many have X-ray luminosities for which stellar evolution products offer convenient explanations. Some non-active IRAS galaxies display anomalously high levels of X-ray emission for which several conceivable origins are investigated: optical misclassification, X-ray misidentification, hidden AGN, incidental activity, starburst, environmental sources. X-ray spectral studies and temporal variations constitute important tools for further investigation, for instance to assess the strength of a starburst or to establish signatures of an active core.

scholarly journals Testing the disk-corona interplay in radiatively-efficient broad-line AGN

2019 ◽  
Vol 628 ◽  
pp. A135 ◽  
Author(s):  
R. Arcodia ◽  
A. Merloni ◽  
K. Nandra ◽  
G. Ponti
Keyword(s):  
Accretion Disk ◽  
Reference Sample ◽  
Selection Effect ◽  
Galactic Nuclei ◽  
Theoretical Explanation ◽  
X Rays ◽  
Broad Line ◽  
Coronal Emission ◽  
X Ray ◽  
Intrinsic Scatter

The correlation observed between monochromatic X-ray and UV luminosities in radiatively-efficient active galactic nuclei (AGN) lacks a clear theoretical explanation despite being used for many applications. Such a correlation, with its small intrinsic scatter and its slope that is smaller than unity in log space, represents the compelling evidence that a mechanism regulating the energetic interaction between the accretion disk and the X-ray corona must be in place. This ensures that going from fainter to brighter sources the coronal emission increases less than the disk emission. We discuss here a self-consistently coupled disk-corona model that can identify this regulating mechanism in terms of modified viscosity prescriptions in the accretion disk. The model predicts a lower fraction of accretion power dissipated in the corona for higher accretion states. We then present a quantitative observational test of the model using a reference sample of broad-line AGN and modeling the disk-corona emission for each source in the LX − LUV plane. We used the slope, normalization, and scatter of the observed relation to constrain the parameters of the theoretical model. For non-spinning black holes and static coronae, we find that the accretion prescriptions that match the observed slope of the LX − LUV relation produce X-rays that are too weak with respect to the normalization of the observed relation. Instead, considering moderately-outflowing Comptonizing coronae and/or a more realistic high-spinning black hole population significantly relax the tension between the strength of the observed and modeled X-ray emission, while also predicting very low intrinsic scatter in the LX − LUV relation. In particular, this latter scenario traces a known selection effect of flux-limited samples that preferentially select high-spinning, hence brighter, sources.

scholarly journals A unified accretion-ejection paradigm for black hole X-ray binaries

2019 ◽  
Vol 626 ◽  
pp. A115 ◽  
Author(s):  
G. Marcel ◽  
J. Ferreira ◽  
M. Clavel ◽  
P.-O. Petrucci ◽  
J. Malzac ◽  
...  
Keyword(s):  
Radio Emission ◽  
Accretion Disk ◽  
Ad Hoc ◽  
Emission Model ◽  
X Rays ◽  
Temperature Plasma ◽  
X Ray ◽  
Fitting Procedure ◽  
High Level ◽  
X Ray Binaries

Context. Transient X-ray binaries (XrB) exhibit very different spectral shapes during their evolution. In luminosity-color diagrams, their behavior in X-rays forms q-shaped cycles that remain unexplained. In Paper I, we proposed a framework where the innermost regions of the accretion disk evolve as a response to variations imposed in the outer regions. These variations lead not only to modifications of the inner disk accretion rate ṁin, but also to the evolution of the transition radius rJ between two disk regions. The outermost region is a standard accretion disk (SAD), whereas the innermost region is a jet-emitting disk (JED) where all the disk angular momentum is carried away vertically by two self-confined jets. Aims. In the previous papers of this series, it has been shown that such a JED–SAD disk configuration could reproduce the typical spectral (radio and X-rays) properties of the five canonical XrB states. The aim of this paper is now to replicate all X-ray spectra and radio emission observed during the 2010–2011 outburst of the archetypal object GX 339-4. Methods. We used the two-temperature plasma code presented in two previous papers (Papers II and III) and designed an automatic ad hoc fitting procedure that for any given date calculates the required disk parameters (ṁin,rJ) that fit the observed X-ray spectrum best. We used X-ray data in the 3–40 keV (RXTE/PCA) spread over 438 days of the outburst, together with 35 radio observations at 9 GHz (ATCA) dispersed within the same cycle. Results. We obtain the time distributions of ṁin(t) and rJ(t) that uniquely reproduce the X-ray luminosity and the spectral shape of the whole cycle. In the classical self-absorbed jet synchrotron emission model, the JED–SAD configuration also reproduces the radio properties very satisfactorily, in particular, the switch-off and -on events and the radio-X-ray correlation. Although the model is simplistic and some parts of the evolution still need to be refined, this is to our knowledge the first time that an outburst cycle is reproduced with such a high level of detail. Conclusions. Within the JED–SAD framework, radio and X-rays are so intimately linked that radio emission can be used to constrain the underlying disk configuration, in particular, during faint hard states. If this result is confirmed using other outbursts from GX 339-4 or other X-ray binaries, then radio could be indeed used as another means to indirectly probe disk physics.

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