scholarly journals A stochastic propagation model to the energy dependent rapid temporal behaviour of Cygnus X-1 as observed by AstroSat in the hard state

2019 ◽  
Vol 486 (2) ◽  
pp. 2964-2975 ◽  
Author(s):  
Bari Maqbool ◽  
Sneha Prakash Mudambi ◽  
R Misra ◽  
J S Yadav ◽  
S B Gudennavar ◽  
...  
Keyword(s):  
Time Lag ◽  
Broad Band ◽  
Propagation Model ◽  
Large Area ◽  
Temporal Behaviour ◽  
X Ray ◽  
Single Temperature ◽  
Hard State ◽  
Band Spectra ◽  
Energy Dependent

Abstract We report the results from analysis of six observations of Cygnus X-1 by Large Area X-ray Proportional Counter (LAXPC) and Soft X-ray Telescope (SXT) onboard AstroSat, when the source was in the hard spectral state as revealed by the broad-band spectra. The spectra obtained from all the observations can be described by a single-temperature Comptonizing region with disc and reflection components. The event mode data from LAXPC provides unprecedented energy dependent fractional root mean square (rms) and time-lag at different frequencies which we fit with empirical functions. We invoke a fluctuation propagation model for a simple geometry of a truncated disc with a hot inner region. Unlike other propagation models, the hard X-ray emission (>4 keV) is assumed to be from the hot inner disc by a single-temperature thermal Comptonization process. The fluctuations first cause a variation in the temperature of the truncated disc and then the temperature of the inner disc after a frequency dependent time delay. We find that the model can explain the energy dependent rms and time-lag at different frequencies.

scholarly journals A broad-band look of the accreting millisecond X-ray pulsar SAX J1748.9−2021 using AstroSat and XMM–Newton

2020 ◽  
Vol 492 (3) ◽  
pp. 4361-4368 ◽  
Author(s):  
Rahul Sharma ◽  
Aru Beri ◽  
Andrea Sanna ◽  
Anjan Dutta
Keyword(s):  
Timing Analysis ◽  
Broad Band ◽  
Energy Bands ◽  
Large Area ◽  
Pulse Profile ◽  
Time Resolved ◽  
X Ray ◽  
Reflection Model ◽  
Single Temperature ◽  
Energy Pulse

ABSTRACT SAX J1748.9−2021 is a transient accretion powered millisecond X-ray pulsar located in the globular cluster NGC 6440. We report on the spectral and timing analysis of SAX J1748.9−2021 performed on AstroSat data taken during its faint and short outburst of 2017. We derived the best-fitting orbital solution for the 2017 outburst and obtained an average local spin frequency of 442.361098(3) Hz. The pulse profile obtained from 3 to 7 and 7 to 20 keV energy bands suggest constant fractional amplitude ∼0.5 per cent for fundamental component, contrary to previously observed energy pulse profile dependence. Our AstroSat observations revealed the source to be in a hard spectral state. The 1–50 keV spectrum from SXT (Soft X-ray Telescope) and LAXPC (Large Area X-ray Proportional Counter) on-board AstroSat can be well described with a single temperature blackbody and thermal Comptonization. Moreover, we found that the combined spectra from XMM–Newton (EPIC-PN) and AstroSat (SXT + LAXPC) indicated the presence of reflection features in the form of iron (Fe Kα) line that we modelled with the reflection model xillvercp. One of the two X-ray burst observed during the AstroSat/LAXPC observation showed hard X-ray emission (>30 keV) due to Compton up-scattering of thermal photons by the hot corona. Time-resolved analysis performed on the bursts revealed complex evolution in emission radius of blackbody for second burst suggestive of mild photospheric radius expansion.

scholarly journals Broad-band spectral study of X-ray transient MAXI J1820+070 using Swift/XRT and NuSTAR

2019 ◽  
Vol 487 (4) ◽  
pp. 5946-5951 ◽  
Author(s):  
Priya Bharali ◽  
Jaiverdhan Chauhan ◽  
Kalyanee Boruah
Keyword(s):  
Thermal Emission ◽  
Broad Band ◽  
Compact Object ◽  
Black Body ◽  
Gravitational Radius ◽  
X Ray ◽  
Stable Circular Orbit ◽  
Hard State ◽  
Best Fitting ◽  
Band Spectra

ABSTRACT We report on a NuSTAR and Swift/XRT observation of the newly discovered X-ray transient MAXI J1820+070. Swift/XRT and NuSTAR have concurrently observed the newly detected source on 2018 March 14. We have simultaneously fitted the broad-band spectra obtained from Swift/XRT and NuSTAR. The observed joint spectra in the energy range 0.6–78.0 keV are well modeled with a weak disc black-body emission, dominant thermal Comptonization, and relativistic reflection fraction. We have detected a fluorescent Iron-Kα line relativistically broadened and a Compton hump at ∼30 keV. We constrain the inner disc radius as well as the disc inclination angle, and their values are found to be 4.1$^{+0.8}_{-0.6}$RISCO (where RISCO ≡ radius of the innermost stable circular orbit) or 5.1$^{+1.0}_{-0.7}$ rg (where rg ≡ gravitational radius) and 29.8$^{+3.0}_{-2.7}$°, respectively. The best-fitting broad-band spectra suggest that the source was in the hard state and evolving. The source emission is best described by weak thermal emission along with strong thermal Comptonization from a relatively cold, optically thick, geometrically thin and ionized accretion disc. X-ray spectral modeling helps us to understand the accretion and ejection properties in the vicinity of the compact object.

scholarly journals Energy and time-lag spectra of galactic black-hole X-ray sources in the low/hard state

2003 ◽  
Vol 403 (1) ◽  
pp. L15-L18 ◽  
Author(s):  
P. Reig ◽  
N. D. Kylafis ◽  
D. Giannios
Keyword(s):  
Black Hole ◽  
Time Lag ◽  
X Ray ◽  
Galactic Black Hole ◽  
Hard State

scholarly journals Broad-band spectral energy distribution of the X-ray transient Swift J1745−26 from outburst to quiescence

2020 ◽  
Vol 637 ◽  
pp. A2
Author(s):  
Sylvain Chaty ◽  
Francis Fortin ◽  
Alicia López-Oramas
Keyword(s):  
Energy Distribution ◽  
Light Curve ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Spectral Energy ◽  
X Ray ◽  
Upper Limit ◽  
Spectral Break ◽  
Hard State ◽  
Low Mass

Aims. We aim to analyse our study of the X-ray transient Swift J1745−26, using observations obtained from its outburst in September 2012, up to its decay towards quiescence in March 2013. Methods. We obtained optical and infrared observations, through override programme at ESO/VLT with FORS2 and ISAAC instruments, and added archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, to build the light curve and the broad-band spectral energy distribution (SED) of Swift J1745−26. Results. We show that, during its outburst and also during its decay towards quiescence, Swift J1745−26 SED can be adjusted, from infrared up to X-rays, by the sum of both a viscous irradiated multi-colour black body emitted by an accretion disc, and a synchrotron power law at high energy. In the radio domain, the SED arises from synchrotron emission from the jet. While our SED fitting confirms that the source remained in the low/hard state during its outburst, we determine an X-ray spectral break at frequency 3.1 ≤ νbreak ≤ 3.4 × 1014 Hz, and a radio spectral break at 1012 Hz ≤ νbreak ≤ 1013 Hz. We also show that the system is compatible with an absorption AV of ∼7.69 mag, lies within a distance interval of D ∼ [2.6 − 4.8] kpc with an upper limit of orbital period Porb = 11.3 h, and that the companion star is a late spectral type in the range K0–M0 V, confirming that the system is a low-mass X-ray binary. We finally plot the position of Swift J1745−26 on an optical-infrared – X-ray luminosity diagram: its localisation on this diagram is consistent with the source staying in the low-hard state during outburst and decay phases. Conclusions. By using new observations obtained at ESO/VLT with FORS2 and ISAAC, and adding archival optical (VLT/VIRCAM), radio and X-ray (Swift) observations, we built the light curve and the broad-band SED of Swift J1745−26, and we plotted its position on an optical-infrared – X-ray luminosity diagram. By fitting the SED, we characterized the emission of the source from infrared, via optical, up to X-ray domain, we determined the position of both the radio and X-ray spectral breaks, we confirmed that it remained in the low-hard state during outburst and decay phases, and we derived its absorption, distance interval, orbital period upper limit, and the late-type nature of companion star, confirming Swift J1745−26 is a low-mass X-ray binary.

scholarly journals An effect of the target position relative to the laser focus on X-ray emission from the laser plasma

1992 ◽  
Vol 10 (4) ◽  
pp. 743-751 ◽  
Author(s):  
M. Chvojka ◽  
B. Králiková ◽  
E. Krouský ◽  
L. Láska ◽  
K. Maŝek ◽  
...  
Keyword(s):  
Laser Plasma ◽  
Laser System ◽  
Broad Band ◽  
Plasma Temperature ◽  
Target Position ◽  
Resonant Line ◽  
X Ray ◽  
Laser Focus ◽  
Foil Target ◽  
Band Spectra

The first harmonics beam generated by an iodine laser system was focused by an f/2 optics on an Al foil target. The X-ray output from the laser plasma both in the line and broad-band spectra was registered over an interval around the “ideal” focus. It was found that the maximum X-ray power is not obtained in the focus itself but for a somewhat larger focal spot outside the focus. To explain this phenomena, temperature and density measurements were in addition made. The plasma temperature evaluated from both the line (He-like Al XII resonant line and j, k, l satellites) and broad-band spectra (two foil method) was also measured and found to be largely constant in the vicinity of the focus. The line and broad-band temperatures differ, the broad-band temperature being about 25% higher. The electron density was equally determined using an intercombination line.

scholarly journals A spectral study of the black hole X-ray binary MAXI J1820+070 with AstroSat and NuSTAR

2020 ◽  
Vol 498 (4) ◽  
pp. 5873-5884
Author(s):  
Sudip Chakraborty ◽  
Nilam Navale ◽  
Ajay Ratheesh ◽  
Sudip Bhattacharyya
Keyword(s):  
Black Hole ◽  
Broad Band ◽  
X Ray ◽  
Reflection Model ◽  
Temporal Features ◽  
Source State ◽  
Hard State ◽  
Independent Observations ◽  
Best Fitting ◽  
Fitting Model

ABSTRACT MAXI J1820+070 is a newly discovered transient black hole X-ray binary, which showed several spectral and temporal features. In this work, we analyse the broad-band X-ray spectra from all three simultaneously observing X-ray instruments onboard AstroSat, as well as contemporaneous X-ray spectra from NuSTAR, observed during the hard state of MAXI J1820+070 in 2018 March. Implementing a combination of multicolour disc model, relativistic blurred reflection model relxilllpcp, and a distant reflection in the form of xillvercp, we achieve reasonable and consistent fits for AstroSat and NuSTAR spectra. The best-fitting model suggests a low temperature disc (kTin ∼ 0.3 keV), iron overabundance (AFe ∼ 4–5 solar), a short lamp-post corona height (h ≲ 8Rg), and a high corona temperature (kTe ∼ 115–150 keV). Addition of a second Comptonization component leads to a significantly better fit, with the kTe of the second Comptonization component being ∼14–18 keV. Our results from independent observations with two different satellites in a similar source state indicate an inhomogeneous corona, with decreasing temperature attributed to increasing height. Besides, utilizing the broader energy coverage of AstroSat, we estimate the black hole mass to be 6.7–13.9 M⊙, consistent with independent measurements reported in the literature.

BeppoSAX observations of the massive X-ray pulsar Cen X-3: Broad-band spectra and iron line diagnostic

2000 ◽  
Vol 25 (3-4) ◽  
pp. 413-416 ◽  
Author(s):  
S. Del Sordo ◽  
D. Dal Fiume ◽  
M. Orlandini ◽  
S. Piraino ◽  
A. Santangelo ◽  
...  
Keyword(s):  
Broad Band ◽  
Iron Line ◽  
X Ray ◽  
Band Spectra

scholarly journals X-ray spectral and timing evolution of MAXI J1727–203 with NICER

2020 ◽  
Vol 497 (3) ◽  
pp. 3896-3910
Author(s):  
K Alabarta ◽  
D Altamirano ◽  
M Méndez ◽  
V A Cúneo ◽  
L Zhang ◽  
...  
Keyword(s):  
Broad Band ◽  
Periodic Oscillations ◽  
X Ray ◽  
Band Noise ◽  
Intermediate States ◽  
Hard State ◽  
The Moment ◽  
Variability Study ◽  
Spectral States ◽  
Rule Out

ABSTRACT We present a detailed X-ray spectral and variability study of the full 2018 outburst of MAXI J1727–203 using NICER observations. The outburst lasted approximately four months. Spectral modelling in the 0.3–10 keV band shows the presence of both a soft thermal and a hard Comptonised component. The analysis of these components shows that MAXI J1727–203 evolved through the soft, intermediate, and hard spectral states during the outburst. We find that the soft (disc) component was detected throughout almost the entire outburst, with temperatures ranging from ∼0.4 keV, at the moment of maximum luminosity, to ∼0.1 keV near the end of the outburst. The power spectrum in the hard and intermediate states shows broad-band noise up to 20 Hz, with no evidence of quasi-periodic oscillations. We also study the rms spectra of the broad-band noise at 0.3−10 keV of this source. We find that the fractional rms increases with energy in most of the outburst except during the hard state, where the fractional rms remains approximately constant with energy. We also find that, below 3 keV, the fractional rms follows the same trend generally observed at energies >3 keV, a behaviour known from previous studies of black holes and neutron stars. The spectral and timing evolution of MAXI J1727–203, as parametrised by the hardness–intensity, hardness–rms, and rms–intensity diagrams, suggest that the system hosts a black hole, although we could not rule out a neutron star.

scholarly journals Broad-band spectral analysis of LMXB XTE J1710−281 with Suzaku

2020 ◽  
Vol 496 (1) ◽  
pp. 197-205
Author(s):  
Prince Sharma ◽  
Rahul Sharma ◽  
Chetana Jain ◽  
Anjan Dutta
Keyword(s):  
Spectral Analysis ◽  
Broad Band ◽  
Emission Spectra ◽  
Band Spectrum ◽  
Surface Boundary ◽  
Hot Electron ◽  
Spectral Parameters ◽  
Surface Boundary Layer ◽  
X Ray ◽  
Single Temperature

ABSTRACT This work presents the broad-band time-averaged spectral analysis of neutron star (NS) low-mass X-ray binary, XTE J1710−281 by using the Suzaku archival data. The source was in a hard or an intermediate spectral state during this observation. This is the first time that a detailed spectral analysis of the persistent emission spectra of XTE J1710−281 has been done up to 30 keV with improved constraints on its spectral parameters. By simultaneously fitting the X-ray Imaging Spectrometer (0.6–9.0 keV) and the HXD-PIN (15.0–30.0 keV) data, we have modelled the persistent spectrum of the source with models comprising a soft component from accretion disc and/or NS surface/boundary layer and a hard Comptonizing component. The 0.6–30 keV continuum with neutral absorber can be described by a multicolour disc blackbody with an inner disc temperature of kTdisc = 0.28 keV, which is significantly Comptonized by the hot electron cloud with electron temperature of kTe ≈ 5 keV and described by photon index Γ = 1.86. A more complex three-component model comprising a multicolour disc blackbody ≈0.30 keV, single-temperature blackbody ≈0.65 keV, and Comptonization from the disc, partially absorbed (about 38 per cent) by an ionized absorber (log(ξ) ≈ 4) describes the broad-band spectrum equally well.

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