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 Observational limits on the X-ray emission from the bubble nebula surrounding Ho IX X-1

2019 ◽  
Vol 488 (4) ◽  
pp. 4614-4622 ◽  
Author(s):  
Rajath Sathyaprakash ◽  
Timothy P Roberts ◽  
Magdalena M Siwek
Keyword(s):  
Strong Evidence ◽  
Thermal Emission ◽  
High Energy ◽  
Accretion Disc ◽  
Spatial Extent ◽  
X Rays ◽  
Radio Observations ◽  
High Energy Astrophysics ◽  
Photometric Analysis ◽  
X Ray

ABSTRACT Optical and radio observations of shock-ionized bubble nebulae surrounding ultraluminous X-ray sources (ULXs) suggest that they are powered by jets or supercritical outflows presumably launched from the ULX accretion disc. Recent simulations of these systems have shown that the shocked wind can emit thermal X-rays with estimated luminosities ≲1036 erg s−1. In this work, we investigated whether it is possible to detect and spatially resolve the X-ray emission from these systems using archival Chandra observations of the ULX Holmberg IX X-1 (Ho IX X-1). This source is an ideal target to study for two reasons: it is surrounded by an optical bubble nebula with a large spatial extent (∼400 pc) that can easily be resolved with Chandra. Further, it has a hard X-ray continuum that is easily distinguishable from the expected soft thermal emission from the nebula. However, a spectral and photometric analysis on stacked Chandra observations of the source reveals that there is no strong evidence for an X-ray bubble associated with it, to a limiting luminosity of ∼2 × 1036 erg s−1. The detection of such X-ray nebulae may be possible with future X-ray missions such as Advanced Telescope for High ENergy Astrophysics(ATHENA), which would provide useful constraints on the kinematics of the outflow. Finally, our observations also emphasize that the nebular emission does not contribute significantly to the residuals in the X-ray spectrum of the source, which are more likely to be linked to processes localized to the ULX.

scholarly journals Extreme Relic Radio Sources in Four Southern Clusters

2002 ◽  
Vol 199 ◽  
pp. 153-156
Author(s):  
H. Andernach ◽  
O.B. Slee ◽  
A.L. Roy ◽  
M. Ehle
Keyword(s):  
Fine Structure ◽  
Thermal Emission ◽  
Host Galaxy ◽  
Radio Sources ◽  
X Rays ◽  
Radio Observations ◽  
Potential Wells ◽  
X Ray ◽  
Abell Clusters ◽  
Inverse Compton

We describe the highest-resolution radio observations yet made of relic radio sources. These relics have extremely steep (α ≤ −2.5) spectra and are located in four southern Abell clusters (A 13, A 85, A133, A 4038). VLA images at 1.4 GHz and ∼4″ resolution show a remarkable variety of fine structure like arcs, wisps, plumes, and loops. Integrated polarization fractions range from 2.3% to 16.8%. Deep red CCD images do not reveal any optical object with a brightness and/or position typical of a radio host galaxy. The X-ray centroids in ROSAT images tend to be displaced from the cluster potential wells in the direction of the relics in A85, A133 and A4038, suggesting that some of the X-rays may be inverse Compton or excess thermal emission from the relic itself.

scholarly journals Search for non-thermal X-ray emission in the colliding wind binary Cygnus OB2 #8A

2020 ◽  
Vol 636 ◽  
pp. A109 ◽  
Author(s):  
E. Mossoux ◽  
J. M. Pittard ◽  
G. Rauw ◽  
Y. Nazé
Keyword(s):  
Thermal Emission ◽  
Broad Band ◽  
X Rays ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Thermal Radio Emission ◽  
Shock Region ◽  
Inverse Compton ◽  
First Time ◽  
Colliding Winds

Aims. Cyg OB2 #8A is a massive O-type binary displaying strong non-thermal radio emission. Owing to the compactness of this binary, emission of non-thermal X-ray photons via inverse Compton scattering is expected. Methods. We first revised the orbital solution for Cyg OB2 #8A using new optical spectra. We then reduced and analysed X-ray spectra obtained with XMM-Newton, Swift, INTEGRAL, and NuSTAR. Results. The analysis of the XMM-Newton and Swift data allows us to better characterise the X-ray emission from the stellar winds and colliding winds region at energies below 10 keV. We confirm the variation of the broad-band light curve of Cyg OB2 #8A along the orbit with, for the first time, the observation of the maximum emission around phase 0.8. The minimum ratio of the X-ray to bolometric flux of Cyg OB2 #8A remains well above the level expected for single O-type stars, indicating that the colliding wind region is not disrupted during the periastron passage. The analysis of the full set of publicly available INTEGRAL observations allows us to refine the upper limit on the non-thermal X-ray flux of the Cyg OB2 region between 20 and 200 keV. Two NuSTAR observations (phases 0.028 and 0.085) allow us to study the Cyg OB2 #8A spectrum up to 30 keV. These data do not provide evidence of the presence of non-thermal X-rays, but bring more stringent constraints on the flux of a putative non-thermal component. Finally, we computed, thanks to a new dedicated model, the anisotropic inverse Compton emission generated in the wind shock region. The theoretical non-thermal emission appears to be compatible with observational limits and the kinetic luminosity computed from these models is in good agreement with the unabsorbed flux observed below 10 keV.

scholarly journals PSR B0656+14: the unified outlook from the infrared to X-rays

2021 ◽  
Vol 502 (2) ◽  
pp. 2005-2022
Author(s):  
S Zharikov ◽  
D Zyuzin ◽  
Yu Shibanov ◽  
A Kirichenko ◽  
R E Mennickent ◽  
...  
Keyword(s):  
Neutron Star ◽  
Absorption Line ◽  
Optical Spectrum ◽  
Near Infrared ◽  
Thermal Emission ◽  
Model Parameters ◽  
X Rays ◽  
Polar Cap ◽  
X Ray ◽  
Star Surface

ABSTRACT We report detection of PSR B0656+14 with the Gran Telescopio Canarias in narrow optical F657, F754, F802, and F902 and near-infrared JHKs bands. The pulsar detection in the Ks band extends its spectrum to 2.2 $\mu$m and confirms its flux increase towards the infrared. We also present a thorough analysis of the optical spectrum obtained by us with the VLT. For a consistency check, we revised the pulsar near-infrared and narrow-band photometry obtained with the HST. We find no narrow spectral lines in the optical spectrum. We compile available near-infrared-optical-UV and archival 0.3–20 keV X-ray data and perform a self-consistent analysis of the rotation phase-integrated spectrum of the pulsar using unified spectral models. The spectrum is best fitted by the four-component model including two blackbodies, describing the thermal emission from the neutron star surface and its hot polar cap, the broken power law, originating from the pulsar magnetosphere, and an absorption line near ∼0.5 keV detected previously. The fit provides better constraints on the model parameters than using only a single spectral domain. The derived surface temperature is $T_{NS}^{\infty } = 7.9(3)\times 10^5$ K. The intrinsic radius (7.8–9.9 km) of the emitting region is smaller than a typical neutron star radius (13 km) and suggests a non-uniform temperature distribution over the star surface. In contrast, the derived radius of the hot polar cap is about twice as large as the ‘canonical’ one. The spectrum of the non-thermal emission steepens from the optical to X-rays and has a break near 0.1 keV. The X-ray data suggest the presence of another absorption line near 0.3 keV.

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 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 1/4 Ke V Diffuse Background and the Local Interstellar Medium

1989 ◽  
Vol 120 ◽  
pp. 536-536
Author(s):  
S.L. Snowden
Keyword(s):  
Interstellar Medium ◽  
Filling Factor ◽  
Thermal Emission ◽  
Mean Free Path ◽  
Physical Parameters ◽  
X Rays ◽  
Local Interstellar Medium ◽  
X Ray ◽  
Diffuse Background ◽  
X Ray Background

The 1/4 keV diffuse X-ray background (SXRB) is discussed in relation to the local interstellar medium (LISM). The most likely source for these soft X-rays is thermal emission from a hot diffuse plasma. The existence of a non-zero flux from all directions and the short ISM mean free path of these X-rays (1020HI cm-2), coupled with ISM pressure constraints, imply that the plasma has a local component and that it must, at least locally (nearest hundred parsecs), have a large filling factor. Our understanding of the geometry and physical parameters of the LISM is therefore directly tied to our understanding of the SXRB.

scholarly journals Detecting shocked intergalactic gas with X-ray and radio observations

2019 ◽  
Vol 627 ◽  
pp. A5 ◽  
Author(s):  
F. Vazza ◽  
S. Ettori ◽  
M. Roncarelli ◽  
M. Angelinelli ◽  
M. Brüggen ◽  
...  
Keyword(s):  
Large Scale ◽  
Intergalactic Medium ◽  
Thermal Emission ◽  
Intergalactic Gas ◽  
Radio Observations ◽  
X Ray ◽  
Large Scale Structures ◽  
Hot Gas ◽  
Scale Structures ◽  
Radio Band

Detecting the thermal and non-thermal emission from the shocked cosmic gas surrounding large-scale structures represents a challenge for observations, as well as a unique window into the physics of the warm-hot intergalactic medium. In this work, we present synthetic radio and X-ray surveys of large cosmological simulations in order to assess the chances of jointly detecting the cosmic web in both frequency ranges. We then propose best observing strategies tailored for existing (LOFAR, MWA, and XMM) or future instruments (SKA-LOW and SKA-MID, Athena, and eROSITA). We find that the most promising targets are the extreme peripheries of galaxy clusters in an early merging stage, where the merger causes the fast compression of warm-hot gas onto the virial region. By taking advantage of a detection in the radio band, future deep X-ray observations will probe this gas in emission, and help us to study plasma conditions in the dynamic warm-hot intergalactic medium with unprecedented detail.

Effect of Asymmetry on a Trap Model for Solar Hard Xray Bursts

1979 ◽  
Vol 3 (6) ◽  
pp. 369-371 ◽  
Author(s):  
D. B. Melrose ◽  
S. M. White
Keyword(s):  
Magnetic Flux ◽  
Flux Tube ◽  
Magnetic Trap ◽  
Energetic Particles ◽  
Magnetic Flux Tube ◽  
X Rays ◽  
Radio Observations ◽  
X Ray ◽  
Additional Information ◽  
Basic Model

The basic model for the precipitation of trapped energetic particles from a magnetic flux tube is Kennel and Petschek’s (1966) model. Their model is symmetric, implying equal precipitation rates at the two feet of the flux tube. We have developed a model for precipitation in an asymmetric flux tube (Melrose and White 1979). Here we explore some of the consequences for the precipitation model of Melrose and Brown (1976) for solar hard X-ray bursts. In Melrose and Brown’s model roughly half the X-rays arise from precipitating electrons. With present instruments it is not possible to resolve the two feet of the flux tube. However, if the feet can be resolved, either directly by future X-ray telescopes, or indirectly through secondary optical, UV or radio observations, then, as we shall show, the additional information obtained could be used to derive information on processes in the magnetic trap.

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