scholarly journals The long-term enhanced brightness of the magnetar 1E 1547.0–5408

2020 ◽  
Vol 633 ◽  
pp. A31 ◽  
Author(s):  
Francesco Coti Zelati ◽  
Alice Borghese ◽  
Nanda Rea ◽  
Daniele Viganò ◽  
Teruaki Enoto ◽  
...  
Keyword(s):  
Thermal Emission ◽  
Broad Band ◽  
Spectral Shape ◽  
Band Spectrum ◽  
Pulse Profile ◽  
X Ray ◽  
Time Period ◽  
Order Of Magnitude ◽  
Cooling Trend

We present the evolution of the X-ray emission properties of the magnetar 1E 1547.0–5408 since February 2004 over a time period covering three outbursts. We analyzed new and archival observations taken with the Swift, NuSTAR, Chandra, and XMM–Newton X-ray satellites. The source has been observed at a relatively steady soft X-ray flux of ≈10−11 erg cm−2 s−1 (0.3–10 keV) over the last 9 years, which is about an order of magnitude fainter than the flux at the peak of the last outburst in 2009, but a factor of ∼30 larger than the level in 2006. The broad-band spectrum extracted from two recent NuSTAR observations in April 2016 and February 2019 showed a faint hard X-ray emission up to ∼70 keV. Its spectrum is adequately described by a flat power law component, and its flux is ∼7 × 10−12 erg cm−2 s−1 (10–70 keV), that is a factor of ∼20 smaller than at the peak of the 2009 outburst. The hard X-ray spectral shape has flattened significantly in time, which is at variance with the overall cooling trend of the soft X-ray component. The pulse profile extracted from these NuSTAR pointings displays variability in shape and amplitude with energy (up to ≈25 keV). Our analysis shows that the flux of 1E 1547.0–5408 is not yet decaying to the 2006 level and that the source has been lingering in a stable, high-intensity state for several years. This might suggest that magnetars can hop among distinct persistent states that are probably connected to outburst episodes and that their persistent thermal emission can be almost entirely powered by the dissipation of currents in the corona.

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 Sax Mission For X-Ray Astronomy

1990 ◽  
Vol 123 ◽  
pp. 141-150 ◽  
Author(s):  
R.C. Butler ◽  
L. Scarsi
Keyword(s):  
Energy Band ◽  
Broad Band ◽  
Energy Spectra ◽  
X Ray ◽  
Joint Development ◽  
Space Agency ◽  
Italian Space Agency ◽  
Galactic Sources ◽  
Bright Source

AbstractThe satellite for X-ray astronomy SAX, to be launched at the end of 1993, is devoted to systematic, integrated and comprehensive, studies of galactic and extra-galactic sources in the energy band 0.1–200 keV, and is under joint development by the Italian Space Agency (ASI) and the Netherlands Agency for Aerospace programs (NIVR), with the participation of SRU/SRON and SSD/ESTEC. The basic scientific objectives can be summarized as follows:– Broad band spectroscopy (E/Δ E=12) from 0.1–10 keV with imaging resolution of 1 arcmin.– Continuum and line spectroscopy (E/Δ E=5–20) in the energy range 3–200 keV.– Variability studies of bright source energy spectra on timescales from milliseconds to days and months.– Systematic long term variability studies over the entire sky down to a source intensity of 1 mCrab.

scholarly journals The Hunt for Pulsating Ultraluminous X-ray Sources

2019 ◽  
Author(s):  
X Song ◽  
D J Walton ◽  
G B Lansbury ◽  
P A Evans ◽  
A C Fabian ◽  
...  
Keyword(s):  
Next Generation ◽  
X Ray ◽  
Monitoring Programs ◽  
Final Sample ◽  
Upper Limits ◽  
Flux Variability ◽  
Order Of Magnitude

Abstract Motivated by the recent discoveries that six Ultraluminous X-ray Sources (ULXs) are powered by highly super-Eddington X-ray pulsars, we searched for additional pulsating ULX (PULX) candidates by identifying sources that exhibit long-term flux variability of at least an order of magnitude (a common feature seen in the 6 known PULXs, which may potentially be related to transitions to the propeller regime). Expanding on previous studies, we used the available fluxes from XMM-Newton, Swift and Chandra, along with carefully computed upper limits in cases of a non-detection, to construct long-term lightcurves for a sample of 296 ULXs selected from the XMM-Newton archive. Among these 296, we find 25 sources showing flux variability larger than a factor of 10, of which 17 show some evidence for (or are at least consistent with) exhibiting bi-modal flux distributions, as would be expected for sources undergoing propeller transitions. These sources are excellent candidates for continued monitoring programs to further test for this behaviour. There are 3 sources in our final sample with fluxes similar to NGC 5907 ULX1, currently the faintest known PULX, which would also be good targets for deeper observations with current facilities to search for pulsations. For the rest of the PULX candidates identified here, the next generation of X-ray telescopes (such as Athena) may be required to determine their nature owing to their lower peak fluxes.

scholarly journals NuSTAR view of Be/X-ray binary pulsar 2S 1417−624 during 2018 giant outburst

2019 ◽  
Vol 490 (2) ◽  
pp. 2458-2466 ◽  
Author(s):  
Shivangi Gupta ◽  
Sachindra Naik ◽  
Gaurava K Jaisawal
Keyword(s):  
Broad Band ◽  
Gaussian Function ◽  
Physical Models ◽  
Spectral Studies ◽  
Band Spectrum ◽  
X Ray ◽  
Binary Pulsar ◽  
Double Peak Structure ◽  
Peak Structure ◽  
Cyclotron Line

ABSTRACT We report the results obtained from a detailed timing and spectral studies of Be/X-ray binary pulsar 2S 1417−624 using data from Swift and NuSTAR observatories. The observations were carried out at the peak of a giant outburst of the pulsar in 2018. X-ray pulsations at ∼17.475 s were detected in the source light curves up to 79 keV. The evolution of the pulse profiles with energy was found to be complex. A four-peaked profile at lower energies gradually evolved into a double-peak structure at higher energies. The pulsed fraction of the pulsar, calculated from the NuSTAR observation was found to follow an anticorrelation trend with luminosity as observed during previous giant X-ray outburst studies in 2009. The broad-band spectrum of the pulsar is well described by a composite model consisting of a cut-off power-law model modified with the interstellar absorption, a thermal blackbody component with a temperature of ≈1 keV, and a Gaussian function for the 6.4 keV iron emission line. Though the pulsar was observed at the peak of the giant outburst, there was no signature of presence of any cyclotron line feature in the spectrum. The radius of the blackbody emitting region was estimated to be ≈2 km, suggesting that the most probable site of its origin is the stellar surface of the neutron star. Physical models were also explored to understand the emission geometry of the pulsar and are discussed in the paper.

scholarly journals The December 2015 re-brightening of V404 Cygni

2018 ◽  
Vol 616 ◽  
pp. A129 ◽  
Author(s):  
J. J. E. Kajava ◽  
S. E. Motta ◽  
C. Sánchez-Fernández ◽  
E. Kuulkers
Keyword(s):  
Broad Band ◽  
High Energy ◽  
Accretion Disc ◽  
Band Spectrum ◽  
Hard Photon ◽  
Time Resolved ◽  
X Ray ◽  
Spectral Behaviour ◽  
Black Hole Binary ◽  
Spectral Cut

In December 2015 the black hole binary V404 Cyg underwent a secondary outburst after the main June 2015 event. We monitored this re-brightening with the INTEGRAL and Swift satellites, and in this paper we report the results of the time-resolved spectral analysis of these data. The December outburst shared several characteristics with the June event. The well-sampled INTEGRAL light curve shows up to ten Crab flares, which are separated by relatively weak non-flaring emission phases when compared to the June outburst. The spectra are nicely described by absorbed Comptonization models, with hard photon indices, Γ ≲ 2, and significant detections of a high-energy cut-off only during the bright flares. This is in contrast to the June outburst, where the Comptonization models gave electron temperatures mostly in the 30–50 keV range, while some spectra were soft (Γ ~ 2.5) without signs of any spectral cut-off. Similarly to the June outburst, we see clear signs of a variable local absorber in the soft energy band covered by Swift/XRT and INTEGRAL/JEM-X, which causes rapid spectral variations observed during the flares. During one flare, both Swift and INTEGRAL captured V404 Cyg in a state where the absorber was nearly Compton thick, N H ≈ 1024 cm−2, and the broad-band spectrum was similar to obscured AGN spectra, as seen during the X-ray plateaus in the June outburst. We conclude that the spectral behaviour of V404 Cyg during the December outburst was analogous with the first few days of the June outburst, both having hard X-ray flares that were intermittently influenced by obscuration due to nearly Compton-thick outflows launched from the accretion disc.

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.

scholarly journals New measurements of the cyclotron line energy in Cen X-3

2020 ◽  
Vol 500 (3) ◽  
pp. 3454-3461
Author(s):  
Gunjan Tomar ◽  
Pragati Pradhan ◽  
Biswajit Paul
Keyword(s):  
Broad Band ◽  
Resonant Scattering ◽  
High Energy ◽  
Emission Lines ◽  
Power Law Model ◽  
Pulse Profile ◽  
Line Energy ◽  
X Ray ◽  
Cyclotron Absorption ◽  
Cyclotron Line

ABSTRACT We report results from the analysis of data from two observations of the accreting binary X-ray pulsar Cen X-3 carried out with the broad-band X-ray observatories Suzaku and NuSTAR. The pulse profile is dominated by a broad single peak and show some energy dependence with two additional weak pulse peaks at energies below 15 and 25 keV, respectively. The broad-band X-ray spectrum for 0.8–60.0 keV for Suzaku  and 3.0–60.0 keV for NuSTAR is fitted well with high-energy cut-off power-law model along with soft-excess, multiple iron emission lines and a cyclotron absorption. The cyclotron line energy is found to be $30.29^{+0.68}_{-0.61}$ and $29.22^{+0.28}_{-0.27}$ keV, respectively, in the Suzaku  and NuSTAR  spectra. We make a comparison of these two measurements with four previous measurements of Cyclotron Resonant Scattering Feature (CRSF) in Cen X-3  obtained with Ginga, BeppoSAX,  and RXTE. We find no evidence for a dependence of the CRSF on luminosity. Except for one CRSF measurement with BeppoSAX , the remaining measurements are consistent with a CRSF energy in the range of 29.5–30.0 keV over a luminosity range of 1.1–5.4 × 1037 erg s−1 different from several other sources that show considerable CRSF variation in the same luminosity range.

scholarly journals The first broad-band X-ray view of the narrow-line Seyfert 1 Ton S180

2020 ◽  
Vol 497 (2) ◽  
pp. 2352-2370 ◽  
Author(s):  
G A Matzeu ◽  
E Nardini ◽  
M L Parker ◽  
J N Reeves ◽  
V Braito ◽  
...  
Keyword(s):  
Thermal Emission ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
Outer Part ◽  
Spectral Energy ◽  
X Rays ◽  
Narrow Line ◽  
X Ray ◽  
Extreme Uv ◽  
Reflection Grating

ABSTRACT We present joint XMM–Newton and NuSTAR observations of the ‘bare’ narrow-line Seyfert 1 Ton S180 (z = 0.062), carried out in 2016 and providing the first hard X-ray view of this luminous galaxy. We find that the 0.4–30 keV band cannot be self-consistently reproduced by relativistic reflection models, which fail to account simultaneously for the soft and hard X-ray emission. The smooth soft excess prefers extreme blurring parameters, confirmed by the nearly featureless nature of the Reflection Grating Spectrometer (RGS) spectrum, while the moderately broad Fe K line and the modest hard excess above 10 keV appear to arise in a milder gravity regime. By allowing a different origin of the soft excess, the broad-band X-ray spectrum and overall spectral energy distribution (SED) are well explained by a combination of (a) direct thermal emission from the accretion disc, dominating from the optical to the far/extreme UV; (b) Comptonization of seed disc photons by a warm (kTe ∼ 0.3 keV) and optically thick (τ ∼ 10) corona, mostly contributing to the soft X-rays; (c) Comptonization by a standard hot ($kT_{\rm \mathrm{ e}}\gtrsim 100$ keV) and optically thin (τ < 0.5) corona, responsible for the primary X-ray continuum; and (d) reflection from the mid/outer part of the disc. The two coronae are suggested to be rather compact, with $R_{\rm hot}\lesssim R_{\rm warm}\lesssim 10\, r_{\rm g}$. Our SED analysis implies that Ton S180 accretes at super-Eddington rates. This is a key condition for the launch of a wind, marginal (i.e. 3.1σ significance) evidence of which is indeed found in the RGS spectrum.

scholarly journals Long-term pulse profile study of the Be/X-ray pulsar SAX J2103.5+4545

2007 ◽  
Vol 473 (2) ◽  
pp. 551-559 ◽  
Author(s):  
A. Camero Arranz ◽  
C. A. Wilson ◽  
M. H. Finger ◽  
V. Reglero
Keyword(s):  
Pulse Profile ◽  
X Ray ◽  
Profile Study
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