NON-THERMAL X-RAYS AND INTERSTELLAR GAS TOWARD THE γ-RAY SUPERNOVA REMNANT RX J1713.7–3946: EVIDENCE FOR X-RAY ENHANCEMENT AROUND CO AND H I CLUMPS

AbstractThe supernova remnant (SNR) Puppis A (aka G260.4-3.4) is a middle-aged supernova remnant, which displays increasing X-ray surface brightness from West to East corresponding to an increasing density of the ambient interstellar medium at the Eastern and Northern shell. The dense IR photon field and the high ambient density around the remnant make it an ideal case to study in γ-rays. Gamma-ray studies based on three years of observations with the Large Area Telescope (LAT) aboard Fermi have revealed the high energy gamma-ray emission from SNR Puppis A. The γ-ray emission from the remnant is spatially extended, and nicely matches the radio and X-ray morphologies. Its γ-ray spectrum is well described by a simple power law with an index of ~2.1, and it is among the faintest supernova remnants yet detected at GeV energies. To constrain the relativistic electron population, seven years of Wilkinson Microwave Anisotropy Probe (WMAP) data were also analyzed, and enabled to extend the radio spectrum up to 93 GHz. The results obtained in the radio and γ-ray domains are described in detail, as well as the possible origins of the high energy γ-ray emission (Bremsstrahlung, Inverse Compton scattering by electrons or decay of neutral pions produced by proton interactions).

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Gamma-ray-emitting narrow-line Seyfert 1 galaxies: the Swift view

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1580 ◽

2020 ◽

Vol 496 (2) ◽

pp. 2213-2229 ◽

Cited By ~ 1

Author(s):

F D’Ammando

Keyword(s):

Gamma Ray ◽

Thermal Emission ◽

Optical Emission ◽

X Rays ◽

Narrow Line ◽

X Ray ◽

Relativistic Jet ◽

Photon Index ◽

Γ Ray ◽

Lower Variability

ABSTRACT We report the analysis of all Swift observations available up to 2019 April of γ-ray-emitting narrow-line Seyfert 1 galaxies (NLSy1). The distribution of X-ray luminosities (and fluxes) indicates that the jet radiation significantly contributes to their X-ray emission, with Doppler boosting making values higher than other radio-loud NLSy1. The 0.3–10 keV photon indices are on average harder with respect to radio-quiet and radio-loud NLSy1, confirming a dominant jet contribution in X-rays. However, the lower variability amplitude with respect to blazars and the softening of the spectrum in some periods suggests that also the corona radiation contributes to the X-ray emission. In optical and ultraviolet (UV) significant flux changes have been observed on daily, weekly, and monthly time-scale, providing a clear indication of the significant contribution of the jet radiation in this part of spectrum. A strong correlation between X-ray, UV, and optical emission and simultaneous flux variations have been observed in 1H 0323+342, SBS 0846+513, PMN J0948+0022 as expected in case the jet radiation is the dominant mechanism. Correlated multiband variability favours the jet-dominated scenario also in FBQS J1644+2619 and PKS 2004−447. The summed X-ray Telescope spectra of 1H 0323+342, SBS 0846+513, PMN J0948+0022, and FBQS J1644+2619 are well fitted by a broken power law with a break around 2 keV. The spectrum above 2 keV is dominated by the non-thermal emission from a beamed relativistic jet, as suggested by the hard photon index. A Seyfert-like feature like the soft X-ray excess has been observed below 2 keV, making these γ-ray-emitting NLSy1 different from typical blazars.

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A New Chapter in Hard X-rays of the M87 AGN

Proceedings ◽

10.3390/proceedings2019017009 ◽

2019 ◽

Vol 17 (1) ◽

pp. 9

Author(s):

Ka-Wah Wong ◽

Rodrigo S. Nemmen ◽

Jimmy A. Irwin ◽

Dacheng Lin

Keyword(s):

High Energy ◽

X Rays ◽

X Ray ◽

Accretion Flow ◽

Relativistic Jet ◽

Very High Energy ◽

Γ Ray ◽

High Energy Emission ◽

First Time ◽

Very High

The nearby M87 hosts an exceptional relativistic jet. It has been regularly monitored in radio to TeV bands, but little has been done in hard X-rays ≳10 keV. For the first time, we have successfully detected hard X-rays up to 40 keV from its X-ray core with joint Chandra and NuSTAR observations, providing important insights to the X-ray origins: from the unresolved jet or the accretion flow. We found that the hard X-ray emission is significantly lower than that predicted by synchrotron self-Compton models introduced to explain very-high-energy γ -ray emission above a GeV. We discuss recent models to understand these high energy emission processes.

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Numerically investigating the morphology of the supernova remnant SN 1006 in the ambient medium with a density discontinuity

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3214 ◽

2019 ◽

Vol 491 (2) ◽

pp. 2460-2464 ◽

Cited By ~ 2

Author(s):

Jun Fang ◽

Jingwen Yan ◽

Lu Wen ◽

Chunyan Lu ◽

Huan Yu

Keyword(s):

Supernova Remnant ◽

Ambient Medium ◽

X Rays ◽

X Ray ◽

North West ◽

Density Discontinuity ◽

North East ◽

The North ◽

South West ◽

Type Ia

ABSTRACT Multiband observations on the Type Ia supernova remnant SN 1006 indicate peculiar properties in its morphologies of emission in the radio, optical, and X-ray bands. In the hard X-rays, the remnant is bilateral with two opposite bright limbs with prominent protrusions. Moreover, a filament has been detected at the radio, optical, and soft X-ray wavelengths. The reason for these peculiar features in the morphologies of the remnant is investigated using 3D HD simulations. With the assumption that the supernova ejecta are evolved in the ambient medium with a density discontinuity, the radius of the remnant’s boundary is smaller in the tenuous medium, and the shell consists of two hemispheres with different radii. Along particular line of sights, protrusions appear on the periphery of the remnants since the emission from the edge of the hemisphere with a larger radius is located outside that from the shell of the small hemisphere. Furthermore, the north-west filament of SN 1006 arises as a result of the intersection of the line of sight and the shocked material near the edges of the two hemispheres. It can be concluded that the protrusions on the north-east and south-west limbs and the north-west filament in the morphologies of SN 1006 can be reproduced as the remnants interacting with the medium with a density discontinuity.

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A NuSTAR view of powerful γ-ray loud blazars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935750 ◽

2019 ◽

Vol 627 ◽

pp. A72 ◽

Cited By ~ 2

Author(s):

G. Ghisellini ◽

M. Perri ◽

L. Costamante ◽

G. Tagliaferri ◽

T. Sbarrato ◽

...

Keyword(s):

Energy Distribution ◽

Spectral Energy Distribution ◽

Peak Frequency ◽

High Energy ◽

Spectral Energy ◽

X Rays ◽

X Ray ◽

Γ Ray ◽

The Universe ◽

Jet Power

We observed three blazars at z > 2 with the NuSTAR satellite. These were detected in the γ-rays by Fermi/LAT and in the soft X-rays, but have not yet been observed above 10 keV. The flux and slope of their X-ray continuum, together with Fermi/LAT data allows us to estimate their total electromagnetic output and peak frequency. For some of them we were able to study the source in different states, and investigate the main cause of the different observed spectral energy distribution. We then collected all blazars at redshifts greater than 2 observed by NuSTAR, and confirm that these hard and luminous X-ray blazars are among the most powerful persistent sources in the Universe. We confirm the relation between the jet power and the disk luminosity, extending it at the high-energy end.

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XMM-Newton and Fermi/LAT view on the supernova remnant 3C434.1

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935487 ◽

2019 ◽

Vol 631 ◽

pp. A179

Author(s):

V. Doroshenko ◽

D. Malyshev ◽

G. Pühlhofer ◽

B. Dincel ◽

M. Sasaki ◽

...

Keyword(s):

Power Law ◽

Supernova Remnant ◽

X Rays ◽

Significant Excess ◽

X Ray ◽

Thermal Origin

We report on XMM-Newton observations of the supernova remnant (SNR) 3C434.1 (G94.0+1.0), the first in X-rays since the ROSAT era. Our analysis confirms the thermal origin of the observed extended X-ray emission, whose morphology appears more complex than previously reported. In particular, part of the shell shows a significantly harder spectrum which is consistent with a power law, and it is, therefore, likely of non-thermal origin. Motivated by these finding, we revisited the GeV observations of the field taken with the Fermi observatory. A significant excess associated with the remnant was detected, which is likely associated with non-thermal X-ray emission from part of the shell. The analysis of the Fermi data resulted in the serendipity discovery of GeV emission from the nearby SNR G093.7-00.2. Finally, we searched for a possible compact remnants within the shell, however, no obvious candidates could be identified due to the fairly large positional uncertainties.

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Middle aged γ-ray pulsar J1957+5033 in X-rays: pulsations, thermal emission and nebula

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3991 ◽

2020 ◽

Author(s):

D A Zyuzin ◽

A V Karpova ◽

Y A Shibanov ◽

A Y Potekhin ◽

V F Suleimanov

Keyword(s):

Neutron Star ◽

Neutron Stars ◽

Power Law ◽

Thermal Emission ◽

Single Pulse ◽

X Rays ◽

Middle Aged ◽

X Ray ◽

Photon Index ◽

Γ Ray

Abstract We analyze new XMM-Newton and archival Chandra observations of the middle-aged γ-ray radio-quiet pulsar J1957+5033. We detect, for the first time, X-ray pulsations with the pulsar spin period of the point-like source coinciding by position with the pulsar. This confirms the pulsar nature of the source. In the 0.15–0.5 keV band, there is a single pulse per period and the pulsed fraction is ≈18 ± 6 per cent. In this band, the pulsar spectrum is dominated by a thermal emission component that likely comes from the entire surface of the neutron star, while at higher energies (≳ 0.7 keV) it is described by a power law with the photon index Γ ≈ 1.6. We construct new hydrogen atmosphere models for neutron stars with dipole magnetic fields and non-uniform surface temperature distributions with relatively low effective temperatures. We use them in the spectral analysis and derive the pulsar average effective temperature of ≈(2 − 3) × 105 K. This makes J1957+5033 the coldest among all known thermally emitting neutron stars with ages below 1 Myr. Using the interstellar extinction–distance relation, we constrain the distance to the pulsar in the range of 0.1–1 kpc. We compare the obtained X-ray thermal luminosity with those for other neutron stars and various neutron star cooling models and set some constraints on latter. We observe a faint trail-like feature, elongated ∼8 arcmin from J1957+5033. Its spectrum can be described by a power law with a photon index Γ = 1.9 ± 0.5 suggesting that it is likely a pulsar wind nebula powered by J1957+5033.

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Theories of discrete X-ray and γ-ray sources: (Invited discourse)

Symposium - International Astronomical Union ◽

10.1017/s0074180900004332 ◽

1970 ◽

Vol 37 ◽

pp. 216-237

Author(s):

James E. Felten

Keyword(s):

Synchrotron Radiation ◽

Supernova Remnants ◽

Galactic Plane ◽

Theoretical Work ◽

X Rays ◽

X Ray ◽

Γ Ray ◽

Low Efficiency ◽

Optical Flux ◽

Galactic Sources

This is a critical review of theories of known discrete X-ray sources. The Crab is omitted, having been dealt with in Woltjer's review. Two of the identified sources, Sco X-1 and Cyg X-2, seem to be of the same sort. A binary or gas-stream model like that of Prendergast and Burbidge, with dimension R ∼ 109 cm and density n ∼ 1016 cm−3, appears reconcilable with the observed features of these sources, though much detailed work remains to be done. Neither object is yet known to be binary. Theoretical work becomes more difficult if, as appears to be the case at least for Sco X-1, the objects are optically thick due to electron scattering; this may affect the optical and X-ray spectra.The recent searches for iron lines in the X-ray spectrum of Sco X-1 are reviewed briefly. The calculations and the energy resolution are not yet good enough to make this a dependable test of models.Several possibilities are offered for explaining the excess radio flux from Sco X-1.Other theories of Sco X-1-type sources are discussed briefly. The theory of Manley and Olbert seems a little superfluous when the gas-stream theory is still in a strong position.There are serious discrepancies between X-ray and optical estimates of the distance to Sco X-1. 21-cm measurements must also be considered. The situation is reviewed, and ways out of the difficulty are discussed.Cen X-2 seems to be like Sco X-1, but several other unidentified sources have hard spectra like the Crab. It is tempting to speculate that most of the galactic sources are supernova remnants.The extended γ-ray source in the galactic plane may be the extrapolated unresolved sum of galactic X-ray sources, as suggested by Ogelman. There are several other possibilities.M87 is the only established extragalactic source. Radio, optical and X-ray observations are summarized and graphed. A power-law extrapolation to the X-ray band is far from mandatory; nevertheless the optical flux from the jet is known to be synchrotron radiation. The time-scale difficulties in the jet are described, and several theories of the survival of the optical electrons are reviewed.Processes for producing X-rays other than thermal bremsstrahlung and synchrotron radiation are listed. These other processes are characterized by low efficiency, and are likely to be unimportant in discrete sources, though several have attracted attention with reference to the diffuse background.

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