scholarly journals AstroSat soft X-ray observations of the symbiotic recurrent nova V3890 Sgr during its 2019 outburst

2020 ◽  
Vol 501 (1) ◽  
pp. 36-49
Author(s):  
K P Singh ◽  
V Girish ◽  
M Pavana ◽  
Jan-Uwe Ness ◽  
G C Anupama ◽  
...  
Keyword(s):  
Model Atmosphere ◽  
Local Thermal Equilibrium ◽  
Atomic Data ◽  
Intensity Level ◽  
Spectral Parameters ◽  
X Ray ◽  
Systematic Uncertainties ◽  
Spectral Models ◽  
Non Local ◽  
Recurrent Nova

ABSTRACT Two long AstroSat Soft X-ray Telescope observations were taken of the third recorded outburst of the symbiotic recurrent nova V3890 Sgr. The first observing run, 8.1–9.9 d after the outburst, initially showed a stable intensity level with a hard X-ray spectrum that we attribute to shocks between the nova ejecta and the pre-existing stellar companion. On day 8.57, the first, weak, signs appeared of supersoft source (SSS) emission powered by residual burning on the surface of the white dwarf. The SSS emission was observed to be highly variable on time-scales of hours. After day 8.9, the SSS component was more stable and brighter. In the second observing run, on days 15.9–19.6 after the outburst, the SSS component was even brighter but still highly variable. The SSS emission was observed to fade significantly during days 16.8–17.8 followed by re-brightening. Meanwhile, the shock component was stable, leading to increase in hardness ratio during the period of fading. AstroSat and XMM–Newton observations have been used to study the spectral properties of V3890 Sgr to draw quantitative conclusions even if their drawback is model dependent. We used the xspec to fit spectral models of plasma emission, and the best fits are consistent with the elemental abundances being lower during the second observing run compared to the first for spectra ≥1 keV. The SSS emission is well fitted by non-local thermal equilibrium model atmosphere used for white dwarfs. The resulting spectral parameters, however, are subject to systematic uncertainties such as completeness of atomic data.

scholarly journals The X-ray Spectra of High Redshift Quasars

1989 ◽  
Vol 134 ◽  
pp. 161-166
Author(s):  
Claude R. Canizares ◽  
Julia L. White
Keyword(s):  
High Redshift ◽  
Radio Spectrum ◽  
Clear Correlation ◽  
X Rays ◽  
Spectral Parameters ◽  
X Ray ◽  
Systematic Uncertainties ◽  
Two Component ◽  
X Ray Background ◽  
Single Power

We present mean spectral parameters for various ensembles of quasars observed with the Einstein Observatory Imaging Proportional Counter (IPC). Our sample contains 71 optically or radio selected quasars with 0.1 < z < 3.5, Galactic NH < 1021 cm−2, total counts of 30 −500, and IPC gain < 19. Quasars are grouped into ensembles according to radio properties (Flat Radio Spectrum [FRS], Steep Radio Spectrum [SRS] or Radio Quiet [RQ]), and either redshift or X-ray luminosity, lx. We find a clear correlation between radio properties and α. FRS quasars have α∼0.4, SRS quasars have α∼0.7 and RQ quasars have α ∼1–1.4. There is no evidence for a dependence of α on z nor, for the FRS and SRS ensembles, on lx over nearly three decades. FRS quasars with 2.0 < z < 3.5 have just as flat mean spectra as those with low z, implying that a single power law, which is flatter than the canonical one with α ∼ 0.65, continues into the 1–10 keV band (in which the observed softer X-rays were emitted). Unfortunately, the results for high redshift and high lx RQ quasars are ambiguous because of systematic uncertainties in the ensemble means. Thus we cannot test the two-component spectral hypothesis of Wilkes and Elvis for these objects. SRS X-ray spectra could be steeper than FRS spectra because of the mixing of two components, although a single intrinsically steeper spectrum is easier to reconcile with the absence of z dependence. The uncertainty in a for RQ quasars with high z leaves open the important question of their contribution to the cosmic X-ray background.

X-RAY SPECTRAL ANALYSIS OF SU UMa TYPE DWARF NOVAE OBSERVED WITH ROSAT

2003 ◽  
Vol 12 (04) ◽  
pp. 739-755 ◽  
Author(s):  
GÜLNUR ÝKİS GÜN ◽  
E. NİHAL ERCAN
Keyword(s):  
Spectral Analysis ◽  
Quiescent State ◽  
X Rays ◽  
Dwarf Novae ◽  
Spectral Parameters ◽  
X Ray ◽  
Spectral Models ◽  
Accretion Rates ◽  
Mass Evaporation ◽  
Best Fit

X-ray spectral parameters were determined for eight SU UMa type Dwarf Novae observed with the ROSAT PSPC. The raw data were fitted with various spectral models and the best fit spectral models are found to be that of Raymond–Smith and Thermal Bremsstrahlung. The best fit temperatures were estimated to be between kT ~ 1.1-1.8 keV while the Column Densities were found to be between NH ~ 2.4×1020-4.1×1020 cm -2. The estimated 0.1-2.4 keV fluxes were in the range of log FX=-13 to -11 ergs cm-2 s-1. FX/F UV and FX/F opt rates were calculated to be between ~0.09 and ~0.37. This shows that most of the energy is radiated in the Optical and Ultraviolet band from the accretion disk in the quiescent state. Many of the SU UMa type Dwarf Novae show an Ultraviolet lag in their outburst spectrum, the Coronal Siphon Flow Model of Meyer and Meyer-Hofmeister may explain this phenomenon. This model proposes a corona at the boundary layer of a system when it is a quiescent state and suggests that some parts of the X-rays come from the corona. For these reasons, the equations of this model were applied to the results of the spectral analysis. Using this model, the mass accretion rates, the mass evaporation rates, and the radii of the coronas were calculated to be ~10-12.3-10-11.3 M⊙ yr -1, ~10-6.5-10-5.5 g cm -2 s -1 and ~109.1-109.9 cm , respectively. The pressures in the coronas were less than ~1200 g cm -2 s -1 for (z) up to ~10×109 cm . The obtained values suggest that the Corona model can indeed operate in SU UMa type Dwarf Novae.

THE X-RAY SPECTRAL ANALYSIS OF DWARF NOVA WZ Sge OBSERVED WITH ROSAT IN QUIESCENCE

2005 ◽  
Vol 14 (07) ◽  
pp. 1185-1193 ◽  
Author(s):  
GÜLNUR İKİS GÜN
Keyword(s):  
Spectral Analysis ◽  
Column Density ◽  
Evaporation Rate ◽  
Accretion Rate ◽  
Spectral Parameters ◽  
X Ray ◽  
Viscosity Parameter ◽  
Spectral Models ◽  
Mass Evaporation ◽  
Best Fit

X-ray spectral parameters were determined for WZ Sge observed with the ROSAT PSPC. The raw data were fitted with various spectral models and the best fit spectral models are found to be that of Raymond–Smith and Thermal Bremsstrahlung. The best fit temperature was estimated to be kT ~ 2.17 keV while the column density was found to be NH ~ 2.8 × 1020 cm -2. The estimated 0.1–2.4 keV flux was in the range of log F = -12 ergs cm -2 s -1. WZ Sge stars show long outburst recurrence times and weak X-ray emissions during the quiescence states. It is possible to lengthen repetition cycles by decreasing the viscosity parameter (α); however there still remains the question why α is so small, specifically for these objects. The Coronal Siphon Model of Meyer and Meyer–Hofmeister1 can explain these phenomenons successfully. For this reason, the equations of this model were applied to the results of spectral analysis. Using this model, the mass accretion rate, mass evaporation rate in corona and the radius of the corona were calculated to be 1014.48 gr yr-1, 10-5.4 gr cm-2 s-1 and 109.7 cm, respectively. The obtained values suggest that the corona model can indeed operate in WZ Sge system.

scholarly journals Stellar laboratories

2020 ◽  
Vol 637 ◽  
pp. A4
Author(s):  
T. Rauch ◽  
S. Gamrath ◽  
P. Quinet ◽  
M. Demleitner ◽  
M. Knörzer ◽  
...  
Keyword(s):  
Mass Fraction ◽  
Local Thermodynamic Equilibrium ◽  
Model Atmosphere ◽  
Spectral Lines ◽  
Oscillator Strengths ◽  
Atomic Data ◽  
Uv Spectrum ◽  
Hot Stars ◽  
Non Local ◽  
First Time

Context. Accurate atomic data is an essential ingredient for the calculation of reliable non-local thermodynamic equilibrium (NLTE) model atmospheres that are mandatory for the spectral analysis of hot stars. Aims. We aim to search for and identify for the first time spectral lines of copper (atomic number Z = 29) and indium (Z = 49) in hot white dwarf (WD) stars and to subsequently determine their photospheric abundances. Methods. Oscillator strengths of Cu IV–VII were calculated to include radiative and collisional bound-bound transitions of Cu in our NLTE model-atmosphere calculations. Oscillator strengths of In IV - VI were compiled from the literature. Results. We newly identified 1 Cu IV, 51 Cu V, 2 Cu VI, and 5 In V lines in the ultraviolet (UV) spectrum of DO-type WD RE 0503−289. We determined the photospheric abundances of 9.3 × 10−5 (mass fraction, 132 times solar) and 3.0 × 10−5 (56 600 times solar), respectively; we also found Cu overabundances in the DA-type WD G191−B2B (6.3 × 10−6, 9 times solar). Conclusions. All identified Cu IV-VI lines in the UV spectrum of RE 0503−289 were simultaneously well reproduced with our newly calculated oscillator strengths. With the detection of Cu and In in RE 0503−289, the total number of trans-iron elements (Z > 28) in this extraordinary WD reaches an unprecedented number of 18.

scholarly journals The Fe XXII I(11.92 Å)/I(11.77 Å) Density Diagnostic

2004 ◽  
Vol 190 ◽  
pp. 124-127
Author(s):  
Christopher W. Mauche ◽  
Duane A. Liedahl ◽  
Kevin B. Fournier
Keyword(s):  
Electron Density ◽  
Highly Charged Ions ◽  
Line Ratio ◽  
Atomic Data ◽  
The Sun ◽  
Late Type ◽  
X Ray ◽  
Spectral Models ◽  
Charged Ions

AbstractUsing the Livermore X-ray Spectral Synthesizer, which calculates spectral models of highly charged ions based on HULLAC atomic data, we investigate the temperature, density, and photoexcitation dependence of the I(11.92 Å)/I(11.77 Å) line ratio of Fe XXII. Applied to the Chandra HETG spectrum of the intermediate polar EX Hya, we find that the electron density of its Te ≈ 12 MK plasma is orders of magnitude greater than that observed in the Sun or other late-type stars.

scholarly journals New Results on X-ray Models and Atomic Data

2005 ◽  
Vol 13 ◽  
pp. 648-650 ◽  
Author(s):  
Jelle S. Kaastra ◽  
Rolf Mewe ◽  
Ton Raassen
Keyword(s):  
Spectral Analysis ◽  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Atomic Data ◽  
X Ray ◽  
Spectral Models ◽  
Recent Developments ◽  
Analysis Package ◽  
Diagnostic Power ◽  
Made In

AbstractWe discuss the most recent developments of the spectral analysis package SPEX. We report on the progress made in updating the atomic data that are used in the spectroscopic code. We also present a set of spectral models that are used for the analysis of high-resolution X-ray spectra of photo-ionized plasmas such as occur in active galactic nuclei. These models include absorption line spectroscopy of photoionized layers. The importance and diagnostic power of inner-shell transitions is shown. We illustrate our results with several examples of observed spectra obtained with the XMM-Newton and Chandra grating spectrometers.

scholarly journals The dependence of spectral parameters in the cross-sectional equation of coherent and incoherent radiation on energy using a mathematical method

2021 ◽  
pp. 1537-1549
Author(s):  
Raed Sabeeh Karyakos ◽  
Ilham M. Yacoob ◽  
Muna Y. Slewa ◽  
Amal M. Banoosh
Keyword(s):  
Atomic Number ◽  
Published Data ◽  
Spectral Parameters ◽  
Cross Sectional ◽  
X Ray ◽  
Incoherent Radiation ◽  
Absorption Experiment ◽  
Cross Sectional Dependence ◽  
The Cross ◽  
X Ray Absorption

The dependence of the cross-section of the coherent and incoherent radiation peaks in the X-ray absorption experiment of different energies (20-800 Kev) was investigated. Cross-sectional dependence on the atomic number Z was included from the published data for (8) elements, ranging from carbon to silver (C-Ag). The proportional constant K was obtained between (σc/σi), with the atomic number Z from (6-47). The results show that the value of K exponentially changes with energy.

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