scholarly journals Massive Stars and Giant HII Regions: The High-Energy Picture

1991 ◽  
Vol 143 ◽  
pp. 397-408
Author(s):  
Thierry Montmerle
Keyword(s):  
Supernova Remnants ◽  
Massive Stars ◽  
Hii Regions ◽  
High Energy ◽  
X Rays ◽  
High Energy Radiation ◽  
Low Mass ◽  
Γ Rays ◽  
Pms Stars

Giant HII regions contain highly energetic objects: luminous, massive stars (including Wolf-Rayet stars) generating powerful winds, as well as, often, supernova remnants. These objects interact with the surrounding gas by creating shock waves. Part of the energy input is radiated away in the form of X-rays; also, protons and electrons may be accelerated in situ and generate γ-rays by collisions with the ionized gas. In addition, the stars themselves (including the accompanying low-mass PMS stars) are sources of X-rays, and W-R stars may emit continuum y-rays and are associated with nuclear γ-ray lines seen in the interstellar medium. Therefore, both through the stars they contain and through interactions within the gas, giant HII regions are, in addition to their more traditional properties and over nearly 7 decades in energy, important sources of high-energy radiation.

scholarly journals High Energy Radiation from Spider Pulsars

Galaxies ◽  
2019 ◽  
Vol 7 (4) ◽  
pp. 93 ◽  
Author(s):  
Chung Yue Hui ◽  
Kwan Lok Li
Keyword(s):  
High Energy ◽  
X Rays ◽  
The Novel ◽  
Large Area ◽  
High Energy Radiation ◽  
X Ray ◽  
Compact Binaries ◽  
Low Mass ◽  
Γ Rays ◽  
Γ Ray

The population of millisecond pulsars (MSPs) has been expanded considerably in the last decade. Not only is their number increasing, but also various classes of them have been revealed. Among different classes of MSPs, the behaviours of black widows and redbacks are particularly interesting. These systems consist of an MSP and a low-mass companion star in compact binaries with an orbital period of less than a day. In this article, we give an overview of the high energy nature of these two classes of MSPs. Updated catalogues of black widows and redbacks are presented and their X-ray/ γ -ray properties are reviewed. Besides the overview, using the most updated eight-year Fermi Large Area Telescope point source catalog, we have compared the γ -ray properties of these two MSP classes. The results suggest that the X-rays and γ -rays observed from these MSPs originate from different mechanisms. Lastly, we will also mention the future prospects of studying these spider pulsars with the novel methodologies as well as upcoming observing facilities.

scholarly journals The interstellar medium in young supernova remnants: key to the production of cosmic X-rays and $\gamma $-rays

2021 ◽  
Vol 366 (6) ◽  
Author(s):  
Hidetoshi Sano ◽  
Yasuo Fukui
Keyword(s):  
Interstellar Medium ◽  
Supernova Remnants ◽  
Cosmic Ray ◽  
High Energy ◽  
X Rays ◽  
Interstellar Gas ◽  
High Energy Radiation ◽  
Dense Cores ◽  
The Relationship ◽  
Turbulent Velocity Field

AbstractWe review recent progress in elucidating the relationship between high-energy radiation and the interstellar medium (ISM) in young supernova remnants (SNRs) with ages of ∼2000 yr, focusing in particular on RX J1713.7−3946 and RCW 86. Both SNRs emit strong nonthermal X-rays and TeV $\gamma $ γ -rays, and they contain clumpy distributions of interstellar gas that includes both atomic and molecular hydrogen. We find that shock–cloud interactions provide a viable explanation for the spatial correlation between the X-rays and ISM. In these interactions, the supernova shocks hit the typically pc-scale dense cores, generating a highly turbulent velocity field that amplifies the magnetic field up to 0.1–1 mG. This amplification leads to enhanced nonthermal synchrotron emission around the clumps, whereas the cosmic-ray electrons do not penetrate the clumps. Accordingly, the nonthermal X-rays exhibit a spatial distribution similar to that of the ISM on the pc scale, while they are anticorrelated at sub-pc scales. These results predict that hadronic $\gamma $ γ -rays can be emitted from the dense cores, resulting in a spatial correspondence between the $\gamma $ γ -rays and the ISM. The current pc-scale resolution of $\gamma $ γ -ray observations is too low to resolve this correspondence. Future $\gamma $ γ -ray observations with the Cherenkov Telescope Array will be able to resolve the sub-pc-scale $\gamma $ γ -ray distribution and provide clues to the origin of these cosmic $\gamma $ γ -rays.

scholarly journals X-rays from Radio Pulsars: The Portable Supernova Remnants

1983 ◽  
Vol 101 ◽  
pp. 471-484 ◽  
Author(s):  
David J. Helfand
Keyword(s):  
Neutron Stars ◽  
Supernova Remnants ◽  
High Energy ◽  
Particle Accelerator ◽  
High Energy Particle ◽  
X Rays ◽  
Radio Pulsars ◽  
High Energy Radiation ◽  
Origin And Evolution ◽  
Supernova Explosions

Neutron stars are the longest-lived remnants of supernova explosions. As a reservoir of thermal energy remaining from the explosion and generated by frictional coupling between core and crust, as a storehouse of magnetic and rotational kinetic energy which allows the star to act as a high energy particle accelerator, and as the source of a deep gravitational potential which can generate heat from infalling matter, neutron stars remain capable of producing high energy radiation for a Hubble time. We review here the results of an extensive survey of supernova remnants and radio pulsars with the imaging instruments on board the Einstein Observatory and discuss the implications of these results for pulsar physics and for the origin and evolution of galactic neutron stars.

scholarly journals Low frequency radio counterparts of HESS J1731−347 a.k.a SNR G353.6−0.7

2017 ◽  
Vol 12 (S331) ◽  
pp. 201-205
Author(s):  
A. J. Nayana ◽  
Poonam Chandra
Keyword(s):  
Radio Emission ◽  
Radio Telescope ◽  
Supernova Remnants ◽  
Low Frequency ◽  
High Energy ◽  
Spectral Indices ◽  
Thermal Radio Emission ◽  
Very High Energy ◽  
Γ Rays ◽  
Very High

AbstractHESS J1731−347 a.k.a. SNR G353.6−0.7 is one of the five known very high energy (VHE, Energy > 0.1 TeV) shell-type supernova remnants. We carried out Giant Metrewave Radio Telescope (GMRT) observations of this TeV SNR in 1390, 610 and 325 MHz bands. We detected the 325 and 610 MHz radio counterparts of the SNR G353.6−0.7 (Nayana et al. 2017). We also determined the spectral indices of individual filaments and our values are consistent with the non-thermal radio emission. We compared the radio morphology with that of VHE emission. The peak in radio emission corresponds to the faintest feature in the VHE emission. We explain this anti-correlated emission in a possible leptonic origin of the VHE γ-rays.

scholarly journals Photo-evaporation of close-in gas giants orbiting around G and M stars

2019 ◽  
Vol 624 ◽  
pp. A101 ◽  
Author(s):  
Daniele Locci ◽  
Cesare Cecchi-Pestellini ◽  
Giuseppina Micela
Keyword(s):  
Extreme Ultraviolet ◽  
Dynamical Evolution ◽  
High Energy ◽  
Electron Content ◽  
Mass Star ◽  
X Rays ◽  
Atmospheric Escape ◽  
Low Mass ◽  
M Stars ◽  
The Stability

Context. X-rays and extreme ultraviolet radiation impacting a gas produce a variety of effects that, depending on the electron content, may provide significant heating of the illuminated region. In a planetary atmosphere of solar composition, stellar high energy radiation can heat the gas to very high temperatures and this could affect the stability of planetary atmospheres, in particular for close-in planets. Aims. We investigate the variations with stellar age in the occurring frequency of gas giant planets orbiting G and M stars, taking into account that the high energy luminosity of a low mass star evolves in time, both in intensity and hardness. Methods. Using the energy-limited escape approach we investigated the effects induced by the atmospheric mass loss on giant exoplanet distribution that is initially flat, at several distances from the parent star. We followed the dynamical evolution of the planet atmosphere, tracking the departures from the initial profile due to the atmospheric escape, until it reaches the final mass-radius configuration. Results. We find that a significant fraction of low mass Jupiter-like planets orbiting with periods lower than ~3.5 days either vaporize during the first billion years or lose a relevant part of their atmospheres. The planetary initial mass profile is significantly distorted; in particular, the frequency of occurrence of gas giants, less massive than 2 MJ, around young stars can be considerably greater than their occurrence around older stellar counterparts.

scholarly journals The X-ray stellar population of the LMC

2008 ◽  
Vol 4 (S256) ◽  
pp. 20-29 ◽  
Author(s):  
Yaël Nazé
Keyword(s):  
Stellar Population ◽  
Main Sequence ◽  
Massive Stars ◽  
High Energy ◽  
Magellanic Clouds ◽  
X Rays ◽  
X Ray ◽  
Energy Domain ◽  
X Ray Binaries

AbstractIn the study of stars, the high energy domain occupies a place of choice, since it is the only one able to directly probe the most violent phenomena: indeed, young pre-main sequence objects, hot massive stars, or X-ray binaries are best revealed in X-rays. However, previously available X-ray observatories often provided only crude information on individual objects in the Magellanic Clouds. The advent of the highly efficient X-ray facilities XMM-Newton and Chandra has now dramatically increased the sensitivity and the spatial resolution available to X-ray astronomers, thus enabling a fairly easy determination of the properties of individual sources in the LMC.

In situ time-resolved X-ray diffraction of tobermorite formation process under hydrothermal condition: Influence of reactive al compound

2011 ◽  
Vol 26 (2) ◽  
pp. 134-137 ◽  
Author(s):  
K. Matsui ◽  
A. Ogawa ◽  
J. Kikuma ◽  
M. Tsunashima ◽  
T. Ishikawa ◽  
...  
Keyword(s):  
Hydrothermal Reaction ◽  
High Energy ◽  
Saturated Steam ◽  
Array Detector ◽  
Time Interval ◽  
X Rays ◽  
X Ray Diffraction ◽  
Formation Reaction ◽  
X Ray

Hydrothermal formation reaction of tobermorite in the autoclaved aerated concrete (AAC) process has been investigated by in situ X-ray diffraction. High-energy X-rays from a synchrotron radiation source in combination with a newly developed autoclave cell and a photon-counting pixel array detector were used. XRD measurements were conducted in a temperature range 100–190°C throughout 12 h of reaction time with a time interval of 4.25 min under a saturated steam pressure. To clarify the tobermorite formation mechanism in the AAC process, the effect of Al addition on the tobermorite formation reaction was studied. As intermediate phases, non-crystalline calcium silicate hydrate (C-S-H), hydroxylellestadite (HE), and katoite (KA) were clearly observed. Consequently, it was confirmed that there were two reaction pathways via C-S-H and KA in the tobermorite formation reaction of Al containing system. In addition, detailed information on the structural changes during the hydrothermal reaction was obtained.

scholarly journals A zone melting device for the in situ observation of directional solidification using high-energy synchrotron x rays

2020 ◽  
Vol 91 (9) ◽  
pp. 093901
Author(s):  
C. Gombola ◽  
G. Hasemann ◽  
A. Kauffmann ◽  
I. Sprenger ◽  
S. Laube ◽  
...  
Keyword(s):  
Directional Solidification ◽  
High Energy ◽  
Zone Melting ◽  
In Situ Observation ◽  
X Rays

scholarly journals Likely detection of pulsed high-energy γ-rays from millisecond pulsar PSR J0218+4232

2000 ◽  
Vol 177 ◽  
pp. 355-358
Author(s):  
L. Kuiper ◽  
W. Hermsen ◽  
F. Verbunt ◽  
A. Lyne ◽  
I. Stairs ◽  
...  
Keyword(s):  
Timing Analysis ◽  
High Energy ◽  
X Rays ◽  
Millisecond Pulsar ◽  
Imaging Analysis ◽  
Pulse Profile ◽  
Significance Level ◽  
Absolute Phase ◽  
Bl Lac ◽  
Γ Rays

AbstractWe report on the likely detection of pulsed high-energyγ-rays from the binary millisecond pulsar PSR J0218+4232 in 100–1000 MeV data from CGRO EGRET. Imaging analysis demonstrates that the highly significantγ-ray source 2EG J0220+4228 (∼ 10σ) is for energies > 100 MeV positionally consistent with both PSR J0218+4232 and the BL Lac 3C66A. However, above 1 GeV 3C66A is the evident counterpart, whereas between 100 and 300 MeV PSR J0218+4232 is the most likely one. Timing analysis using one ephemeris valid for all EGRET observations yields in the 100-1000 MeV range a double-pulse profile at a ∼ 3.5σsignificance level. The phase separation is similar to the component separation of ∼ 0.47 observed at X-rays. A comparison of theγ-ray profile with the 610 MHz radio profile in absolute phase shows that the twoγ- ray pulses coincide with two of the three emission features in the complex radio profile.

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