scholarly journals Cooling of accretion disc coronae by Type I X-ray bursts

2020 ◽  
Vol 499 (3) ◽  
pp. 4479-4489
Author(s):  
J Speicher ◽  
D R Ballantyne ◽  
J Malzac
Keyword(s):  
Accretion Rate ◽  
Temperature Drop ◽  
Accretion Disc ◽  
Type I ◽  
X Ray ◽  
Geometrical Properties ◽  
Fundamental Properties ◽  
Cooling Effects ◽  
The Impact ◽  
Burst Emission

ABSTRACT Although accretion disc coronae appear to be common in many accreting systems, their fundamental properties remain insufficiently understood. Recent work suggests that Type I X-ray bursts from accreting neutron stars provide an opportunity to probe the characteristics of coronae. Several studies have observed hard X-ray shortages from the accretion disc during an X-ray burst implying strong coronal cooling by burst photons. Here, we use the plasma emission code eqpair to study the impact of X-ray bursts on coronae, and how the coronal and burst properties affect the coronal electron temperatures and emitted spectra. Assuming a constant accretion rate during the burst, our simulations show that soft photons can cool coronal electrons by a factor of ≳ 10 and cause a reduction of emission in the 30–50 keV band to $\lesssim 1{{\ \rm per\ cent}}$ of the pre-burst emission. This hard X-ray drop is intensified when the coronal optical depth and aspect ratio is increased. In contrast, depending on the properties of the burst and corona, the emission in the 8–24 keV band can either increase, by a factor of ≳ 20, or decrease, down to $\lesssim 1{{\ \rm per\ cent}}$ of the pre-burst emission. An increasing accretion rate during the X-ray burst reduces the coronal cooling effects and the electron temperature drop can be mitigated by $\gtrsim 60{{\ \rm per\ cent}}$. These results indicate that changes of the hard X-ray flux during an X-ray burst probe the geometrical properties of the corona.

scholarly journals X-ray properties of reverberation-mapped AGNs with super-Eddington accreting massive black holes

2019 ◽  
Vol 15 (S356) ◽  
pp. 143-143
Author(s):  
Jaya Maithil ◽  
Michael S. Brotherton ◽  
Bin Luo ◽  
Ohad Shemmer ◽  
Sarah C. Gallagher ◽  
...  
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Accretion Rate ◽  
Time Lags ◽  
Black Hole Mass ◽  
Host Galaxies ◽  
Massive Black Holes ◽  
X Ray ◽  
Photon Index ◽  
The Impact

AbstractActive Galactic Nuclei (AGN) exhibit multi-wavelength properties that are representative of the underlying physical processes taking place in the vicinity of the accreting supermassive black hole. The black hole mass and the accretion rate are fundamental for understanding the growth of black holes, their evolution, and the impact on the host galaxies. Recent results on reverberation-mapped AGNs show that the highest accretion rate objects have systematic shorter time-lags. These super-Eddington accreting massive black holes (SEAMBHs) show BLR size 3-8 times smaller than predicted by the Radius-Luminosity (R-L) relationship. Hence, the single-epoch virial black hole mass estimates of highly accreting AGNs have an overestimation of a factor of 3-8 times. SEAMBHs likely have a slim accretion disk rather than a thin disk that is diagnostic in X-ray. I will present the extreme X-ray properties of a sample of dozen of SEAMBHs. They indeed have a steep hard X-ray photon index, Γ, and demonstrate a steeper power-law slope, ασx.

scholarly journals New Reaction Rates Of 64Ge(p,γ)65As(p,γ)66Se And The Impact On Type I X-ray Bursts

2017 ◽  
Author(s):  
Yi Hua Lam ◽  
Jianjun He ◽  
Hendrik Schatz ◽  
B. Alex Brown ◽  
Anuj Parikh
Keyword(s):  
Reaction Rates ◽  
Type I ◽  
X Ray ◽  
The Impact

scholarly journals New ASCA Observations of two Anomalous X-ray Pulsars

2000 ◽  
Vol 177 ◽  
pp. 695-698 ◽  
Author(s):  
B. Paul ◽  
M. Kawasaki ◽  
T. Dotani ◽  
F. Nagase
Keyword(s):  
Accretion Rate ◽  
Accretion Disc ◽  
Spectral Shape ◽  
Energy Spectra ◽  
Pulse Profile ◽  
X Ray ◽  
Low Mass ◽  
Low X ◽  
Star Surface ◽  
Made In

AbstractNewASCAobservations of two anomalous X-ray pulsars (AXP) 4U 0142+61 and 1E 1048.1-5937, made in 1998, when compared to earlier observations in 1994 show remarkable stability in the intensity, spectral shape and pulse profile. The energy spectra consist of two components, a power-law and a blackbody emission from the neutron star surface. In IE 1048.1-5937, we have identified three epochs with different spin-down rates and discuss its implications for the magnetar hypothesis of the AXPs. We also note that the spin-down rate and its variations in IE 1048.1-5937 are much larger than what normally can be produced by an accretion disc with very low mass accretion rate corresponding to its low X-ray luminosity.

scholarly journals The impact of crystal size and temperature on the adsorption-induced flexibility of the Zr-based metal–organic framework DUT-98

2019 ◽  
Vol 10 ◽  
pp. 1737-1744 ◽  
Author(s):  
Simon Krause ◽  
Volodymyr Bon ◽  
Hongchu Du ◽  
Rafal E Dunin-Borkowski ◽  
Ulrich Stoeck ◽  
...  
Keyword(s):  
Crystal Size ◽  
Metal Organic Framework ◽  
Adsorption Behavior ◽  
Switching Behavior ◽  
Type I ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metal Organic ◽  
The Impact ◽  
Organic Framework

In this contribution we analyze the influence of adsorption cycling, crystal size, and temperature on the switching behavior of the flexible Zr-based metal–organic framework DUT-98. We observe a shift in the gate-opening pressure upon cycling of adsorption experiments for micrometer-sized crystals and assign this to a fragmentation of the crystals. In a series of samples, the average crystal size of DUT-98 crystals was varied from 120 µm to 50 nm and the obtained solids were characterized by X-ray diffraction, infrared spectroscopy, as well as scanning and transmission electron microscopy. We analyzed the adsorption behavior by nitrogen and water adsorption at 77 K and 298 K, respectively, and show that adsorption-induced flexibility is only observed for micrometer-sized crystals. Nanometer-sized crystals were found to exhibit reversible type I adsorption behavior upon adsorption of nitrogen and exhibit a crystal-size-dependent steep water uptake of up to 20 mmol g−1 at 0.5 p/p 0 with potential for water harvesting and heat pump applications. We furthermore investigate the temperature-induced structural transition by in situ powder X-ray diffraction. At temperatures beyond 110 °C, the open-pore state of the nanometer-sized DUT-98 crystals is found to irreversibly transform to a closed-pore state. The connection of crystal fragmentation upon adsorption cycling and the crystal size dependence of the adsorption-induced flexibility is an important finding for evaluation of these materials in future adsorption-based applications. This work thus extends the limited amount of studies on crystal size effects in flexible MOFs and hopefully motivates further investigations in this field.

scholarly journals A catalogue of intermediate-duration Type I X-ray bursts observed with the INTEGRAL satellite

2020 ◽  
Vol 494 (2) ◽  
pp. 2509-2522 ◽  
Author(s):  
K Alizai ◽  
J Chenevez ◽  
S Brandt ◽  
N Lund
Keyword(s):  
Accretion Rate ◽  
Type I ◽  
Emission Method ◽  
X Ray ◽  
Long Duration ◽  
Photospheric Radius

ABSTRACT We present a catalogue of long-duration bursts observed with the Joint European X-ray Monitor and IBIS/ISGRI instruments onboard the INTEGRAL satellite. The 14 bursts have e-folding times ranging from 55 s to ≈17 min, and are therefore classified as intermediate-duration bursts, caused by the ignition of an unusually thick helium layer. Though seven events have already been reported in literature, we have systematically reanalysed the whole sample. We find three new photospheric radius expansion bursts, which are not reported in the literature, allowing us to provide a new estimate of the distances to these sources. We apply the enhanced persistent emission method (also known as the fa method) on sources with detectable persistent emission prior to a burst, in order to follow the evolution of the accretion rate during the burst. Although we do not get significantly better fits, the evolution of the fa factor shows an indicative behaviour, which we discuss.

scholarly journals Burst-induced coronal cooling in GS 1826–24

2020 ◽  
Vol 634 ◽  
pp. A58 ◽  
Author(s):  
C. Sánchez-Fernández ◽  
J. J. E. Kajava ◽  
J. Poutanen ◽  
E. Kuulkers ◽  
V. F. Suleimanov
Keyword(s):  
Neutron Star ◽  
Emission Spectra ◽  
Spectral Shape ◽  
Type I ◽  
Simultaneous Observation ◽  
X Ray ◽  
Neutron Star Mass ◽  
Hard State ◽  
First Time ◽  
Burst Emission

Type I X-ray bursts in GS 1826–24, and in several other systems, may induce cooling of the hot inner accretion flow that surrounds the bursting neutron star. Given that GS 1826–24 remained persistently in the hard state over the period 2003–2008 and presented regular bursting properties, we stacked the spectra of the X-ray bursts detected by INTEGRAL (JEM-X and ISGRI) and XMM-Newton (RGS) during that period to study the effect of the burst photons on the properties of the Comptonizing medium. The extended energy range provided by these instruments allows the simultaneous observation of the burst and persistent emission spectra. We detect an overall change in the shape of the persistent emission spectrum in response to the burst photon shower. For the first time, we observe simultaneously a drop in the hard X-ray emission, together with a soft X-ray excess with respect to the burst blackbody emission. The hard X-ray drop can be explained by burst-induced coronal cooling, while the bulk of the soft X-ray excess can be described by fitting the burst emission with an atmosphere model, instead of a simple blackbody model. Traditionally, the persistent emission was assumed to be invariant during X-ray bursts, and more recently to change only in normalization but not in spectral shape; the observed change in the persistent emission level during X-ray bursts may thus trigger the revision of existing neutron star mass-radius constraints, as the derived values rely on the assumption that the persistent emission does not change during X-ray bursts. The traditional burst fitting technique leads to up to a 10% overestimation of the bolometric burst flux in GS 1826–24, which significantly hampers the comparisons of the KEPLER and MESA model against this “textbook burster”.

scholarly journals Accretion Disc Thermal Reverberation in the Lamp Post Geometry

Proceedings ◽  
2019 ◽  
Vol 17 (1) ◽  
pp. 12 ◽  
Author(s):  
Iossif E. Papadakis ◽  
Elias S. Kammoun ◽  
Michal Dovčiak
Keyword(s):  
Light Propagation ◽  
Accretion Rate ◽  
Relativistic Effects ◽  
Accretion Disc ◽  
Time Lags ◽  
Response Functions ◽  
X Ray ◽  
Model Predictions ◽  
Ngc 5548

We present results regarding the disc response functions and the corresponding time lags assuming a standard Novikov–Thorne accretion disc illuminated by a point-like X-ray source. We took into account all relativistic effects in the light propagation from the X-ray source to the disc and then to the observer, and we computed the disc reflection, accounting for its radial ionization profile. Our results suggest that the thermal reverberation effects should be stronger in sources with large X-ray source height and low accretion rate. We found that time lags increase with height and accretion rate. The amplitude of the observed time lags as a function of wavelength (in NGC 5548) is consistent with the model predictions. It is not necessary for the disc to be too hot, it may be that the X-ray source is located further from the disc.

scholarly journals Multiepoch, multiwavelength study of accretion onto T Tauri

2018 ◽  
Vol 618 ◽  
pp. A55 ◽  
Author(s):  
P. C. Schneider ◽  
H. M. Günther ◽  
J. Robrade ◽  
J. H. M. M. Schmitt ◽  
M. Güdel
Keyword(s):  
Near Infrared ◽  
Accretion Rate ◽  
Strong Shock ◽  
Field Configuration ◽  
Optical Data ◽  
X Rays ◽  
Coronal Emission ◽  
X Ray ◽  
T Tauri ◽  
The Impact

Classical T Tauri stars (CTTSs) accrete matter from the inner edge of their surrounding circumstellar disks. The impact of the accretion material on the stellar atmosphere results in a strong shock, which causes emission from the X-ray to the near-infrared (NIR) domain. Shock velocities of several 100 km s−1 imply that the immediate post shock plasma emits mainly in X-rays. Indeed, two X-ray diagnostics, the so-called soft excess and the high densities observed in He-like triplets, differentiate CTTSs from their non-accreting siblings. However, accretion shock properties derived from X-ray diagnostics often contradict established ultraviolet (UV)–NIR accretion tracers and a physical model simultaneously explaining both, X-ray and UV–NIR accretion tracers, is not yet available. We present new XMM-Newton and Chandra grating observations of the CTTS T Tauri combined with UV and optical data. During all epochs, the soft excess is large and the densities derived from the O VII and Ne IX He-like triplets are compatible with coronal densities. This confirms that the soft X-ray emission cannot originate in accretion funnels that carry the bulk of the accretion rate despite T Tauri’s large soft excess. Instead, we propose a model of radially density stratified accretion columns to explain the density diagnostics and the soft excess. In addition, accretion rate and X-ray luminosity are inversely correlated in T Tauri over several epochs. Such an anti-correlation has been observed in samples of stars. Hence the process causing it must be intrinsic to the accretion process, and we speculate that the stellar magnetic field configuration on the visible hemisphere affects both the accretion rate and the coronal emission, eventually causing the observed anti-correlation.

scholarly journals Black hole mass accretion rates and efficiency factors for over 750 AGN and multiple GBH

2020 ◽  
Vol 500 (1) ◽  
pp. 215-231
Author(s):  
Ruth A Daly
Keyword(s):  
Black Hole ◽  
Radio Emission ◽  
Binary Systems ◽  
Accretion Rate ◽  
Beam Power ◽  
Black Hole Mass ◽  
X Ray ◽  
Accretion Rates ◽  
Efficiency Factors ◽  
The Impact

ABSTRACT Mass accretion rates in dimensionless and physical units, and efficiency factors describing the total radiant luminosity of the disc and the beam power of the outflow are obtained and studied here for samples of black hole systems with outflows. Four samples of sources including 576 LINERs, 100 classical double (FRII) radio sources, 80 relatively local AGN, and 103 measurements of four stellar mass X-ray binary systems, referred to as Galactic Black Holes (GBHs), are included in the study. All of the sources have highly collimated outflows leading to compact radio emission or powerful extended (FRII) radio emission. The properties of each of the full samples are explored, as are those of the four individual GBH, and sub-types of the FRII and local AGN samples. Source types and sub-types that have high, medium, and low values of accretion rates and efficiency factors are identified and studied. A new efficiency factor that describes the relative impact of black hole spin and mass accretion rate on the beam power is defined and studied, and is found to provide a new and interesting diagnostic. Mass accretion rates for 13 sources and efficiency factors for 6 sources are compared with values obtained independently, and indicate that similar values are obtained with independent methods. The mass accretion rates and efficiency factors obtained here substantially increase the number of values available, and improve our understanding of their relationship to source types. The redshift dependence of quantities is presented and the impact on the results is discussed.

scholarly journals A persistent ultraviolet outflow from the accretion disc in a transient neutron star binary

2021 ◽  
Author(s):  
Noel Castro Segura ◽  
Christian Knigge ◽  
Knox Long ◽  
Diego Altamirano ◽  
Montserrat Armas Padilla ◽  
...  
Keyword(s):  
Neutron Star ◽  
Hubble Space Telescope ◽  
Uv Spectroscopy ◽  
Accretion Disc ◽  
Absorption Lines ◽  
Time Resolved ◽  
X Ray ◽  
Astrophysical Objects ◽  
Hard State ◽  
The Impact

Abstract All disc-accreting astrophysical objects also produce powerful disc winds and/or jets. In compact binaries containing neutron stars or black holes, accretion often takes place during violent outbursts. The main disc wind signatures seen during these eruptions are blue-shifted X-ray absorption lines. However, these signatures are only observed during "soft states", when the accretion disc generates most of the luminosity. By contrast, optical wind-formed absorption lines have recently been detected in "hard states", when the luminosity is dominated by a hot corona. The relationship between these disc wind signatures is unknown, and no erupting compact binary has so far been observed to display wind-formed lines between the X-ray and optical bands, despite the many strong resonance transitions in this ultraviolet (UV) region of the spectrum. In turn, the impact of disc winds on the overall mass and energy budget of these systems remains a key open question. Here, we show that the transient neutron star X-ray binary Swift J1858.6-0814 exhibits wind-formed, blue-shifted absorption features associated with C IV, N V and He II in time-resolved, UV spectroscopy obtained with the Cosmic Origins Spectrograph on board the Hubble Space Telescope during a luminous hard state. In simultaneous ground-based observations, the optical H and He I lines also display transient blue-shifted absorption troughs. By decomposing our UV data into constant and flaring components, we demonstrate that the blue-shifted absorption is associated with the former, which implies that the outflow is always present. The joint presence of UV and optical wind features in the hard state reveals a multi-phase and/or spatially stratified evaporative outflow from the outer disc. This type of persistent mass loss across all accretion states has been predicted by radiation-hydrodynamic simulations and is required to account for the shorter-than-expected outburst durations.

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