scholarly journals Morphology of Gamma-Ray Halos around Middle-aged Pulsars: Influence of the Pulsar Proper Motion

2021 ◽  
Vol 922 (2) ◽  
pp. 130
Author(s):  
Yi Zhang (张艺) ◽  
Ruo-Yu Liu ◽  
S. Z. Chen ◽  
Xiang-Yu Wang
Keyword(s):  
High Altitude ◽  
Proper Motion ◽  
Gamma Ray ◽  
Galactic Disk ◽  
Transverse Velocity ◽  
Surrounding Medium ◽  
Relativistic Electrons ◽  
Middle Aged ◽  
Average Value ◽  
Extended Sources

Abstract Recently, gamma-ray halos of a few degree extension have been detected around two middle-aged pulsars, namely, Geminga and PSR B0656+14, by the High Altitude Water Cherenkov observatory (HAWC). The gamma-ray radiation arises from relativistic electrons that escape the pulsar wind nebula and diffuse in the surrounding medium. The diffusion coefficient is found to be significantly lower than the average value in the Galactic disk. If so, given a typical transverse velocity of 300–500 km s−1 for a pulsar, its displacement could be important in shaping the morphology of its gamma-ray halos. Motivated by this, we study the morphology of pulsar halos considering the proper motion of pulsar. We define three evolutionary phases of the pulsar halo to categorize its morphological features. The morphology of pulsar halos below 10 TeV is double peaked or single peaked with an extended tail, which depends on the electron injection history. Above 10 TeV, the morphology of pulsar halos is nearly spherical, due to the short cooling timescale (<50 kyr) for tens of teraelectronvolt electrons. We also quantitatively evaluate the separation between the pulsar and the center of the gamma-ray halo, as well as the influence of different assumptions on the pulsar characteristics and the injected electrons. Our results suggest that the separation between the center of the gamma-ray halo above 10 TeV and the associated pulsar is usually too small to be observable by HAWC or the Large High Altitude Air Shower Observatory. Hence, our results provide a useful approach to constrain the origin of extended sources at very high energies.

scholarly journals Morphology of Gamma-ray Halos around Middle-aged Pulsars: Influence of the Pulsar Proper Motion

2021 ◽  
Author(s):  
Yi Zhang ◽  
S.Z. Chen ◽  
Xiang-Yu Wang ◽  
Ruo-Yu Liu
Keyword(s):  
Proper Motion ◽  
Gamma Ray ◽  
Middle Aged

scholarly journals Lack of effects of moderate-high altitude upon lung function in healthy middle-aged volunteers

1999 ◽  
Vol 93 (10) ◽  
pp. 739-743 ◽  
Author(s):  
P. Casan ◽  
B. Togores ◽  
J. Giner ◽  
I. Nerin ◽  
F. Drobnic ◽  
...  
Keyword(s):  
Lung Function ◽  
High Altitude ◽  
Middle Aged

scholarly journals Gamma-rays from Solar Flares

2000 ◽  
Vol 195 ◽  
pp. 123-132 ◽  
Author(s):  
R. Ramaty ◽  
N. Mandzhavidze
Keyword(s):  
Energy Release ◽  
Gamma Rays ◽  
Solar Flares ◽  
Gamma Ray ◽  
Particle Interaction ◽  
Mass Motion ◽  
Relativistic Electrons ◽  
Total Energy Release ◽  
Flare Energy ◽  
Accelerated Particles

Gamma-ray emission is the most direct diagnostic of energetic ions and relativistic electrons in solar flares. Analysis of solar flare gamma-ray data has shown: (i) ion acceleration is a major consequence of flare energy release, as the total flare energy in accelerated particles appears to be equipartitioned between ≳ 1 MeV/nucleon ions and ≳ 20 keV electrons, and amounts to an important fraction of the total energy release; (ii) there are flares for which over 50% of the energy is in a particles and heavier ions; (iii) in both impulsive and gradual flares, the particles that interact at the Sun and produce gamma rays are essentially always accelerated by the same mechanism that operates in impulsive flares, probably stochastic acceleration through gyroresonant wave particle interaction; and (iv) gamma-ray spectroscopy can provide new information on solar abundances, for example the site of the FIP-bias onset and the photospheric 3He abundance. We propose a new technique for the investigation of mass motion and mixing in the solar atmosphere: the observations of gamma-ray lines from long-term radioactivity produced by flare accelerated particles.

scholarly journals Chemical Properties of the Local Galactic Disk and Halo. I. Fundamental Properties of 1544 Nearby, High Proper-motion M Dwarfs and Subdwarfs

2020 ◽  
Vol 159 (1) ◽  
pp. 30
Author(s):  
Neda Hejazi ◽  
Sébastien Lépine ◽  
Derek Homeier ◽  
R. Michael Rich ◽  
Michael M. Shara
Keyword(s):  
Proper Motion ◽  
Galactic Disk ◽  
Chemical Properties ◽  
M Dwarfs ◽  
Fundamental Properties

First results of LHAASO

2021 ◽  
Author(s):  
Ruo-Yu Liu
Keyword(s):  
High Altitude ◽  
Detailed Analysis ◽  
Confidence Level ◽  
Gamma Ray ◽  
Crab Nebula ◽  
Ultrahigh Energy ◽  
Air Shower ◽  
First Results ◽  
Energy Gamma

The Large High Altitude Air Shower Observatory (LHAASO) has recently published the first results, including the discovery of 12 ultrahigh-energy gamma-ray sources (with emission above 100[Formula: see text]TeV) above [Formula: see text] confidence level and a detailed analysis of Crab Nebula. This contribution gives a brief introduction to the LHAASO experiment and its recent discoveries.

Methanol Masers in the Andromeda Galaxy

2017 ◽  
Vol 13 (S336) ◽  
pp. 113-116
Author(s):  
Ylva M. Pihlström ◽  
Loránt O. Sjouwerman
Keyword(s):  
Proper Motion ◽  
Milky Way ◽  
Local Group ◽  
Angular Resolution ◽  
Transverse Velocity ◽  
High Angular Resolution ◽  
Dynamic Force ◽  
Group Members ◽  
Methanol Masers ◽  
Motion Studies

AbstractIs M31 going to collide with the Milky Way, or spiral around it? Determining the gravitational potential in the Local Group has been a challenge since it requires 3D space velocities and orbits of the members, and most objects have only had line-of-sight velocities measured. Compared to the less massive group members, the transverse velocity of M31 is of great interest, as after the Milky Way, M31 is the most dominant constituent and dynamic force in the Local Group. Proper motion studies of M31 are preferentially done using masers, as continuum sources are much weaker, and are enabled through the high angular resolution provided by VLBI in the radio regime. The challenges of achieving high astrometric accuracy at high VLBI frequencies (> 20 GHz) makes observations at lower frequencies attractive, as long as sufficient angular resolution is obtained. In particular, we have discovered 6.7 GHz methanol masers in M31 using the VLA, and here we will address their feasibility as VLBI proper motion targets using a set of global VLBI observations.

scholarly journals A Possible Discovery of a Flaring 1012 eV Gamma-Ray Source near the Red Dwarf EV Lac

1995 ◽  
Vol 151 ◽  
pp. 78-79
Author(s):  
I.Yu. Alekseev ◽  
N.N. Chalenko ◽  
V.P. Fomin ◽  
R.E. Gershberg ◽  
O.R. Kalekin ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Electronic Device ◽  
Angular Size ◽  
High Energy ◽  
Optical Systems ◽  
Relativistic Electrons ◽  
Large Area ◽  
Γ Rays ◽  
Γ Ray ◽  
Ev Lac

During the 1994 coordinated observations of the red dwarf flare star EV Lac, the star was monitored in the very high energy (VHE) γ-ray range around 1012 eV with the Crimean ground-based γ-ray telescope GT-48. This telescope consists of two identical optical systems (Vladimirsky et al. 1994) which were directed in parallel on EV Lac.The detection principle of the VHE γ-rays is based on the Čerenkov radiation emitted by relativistic electrons and positrons. The latter are generated in the interaction of the γ-rays with nuclei in the Earth’s atmosphere that leads to an appearance of a shower of charged particles and γ-quanta. The duration of the Cherenkov radiation flash is very short, just about a few nanoseconds. The angular size of the shower is ∼ 1°. To detect such flashes we use an optical system with large area mirrors and a set of 37 photomultipliers (PMs) in the focal plane. Using the information from these PMs which are spaced hexagonally and correspond to a field of view of 2°.6 on the sky, we can obtain the image of an optical flash. The electronic device permits us to detect nanosecond flashes (40 ns exposure time and 12 μs readout dead-time).

scholarly journals OPTICAL-ULTRAVIOLET SPECTRUM AND PROPER MOTION OF THE MIDDLE-AGED PULSAR B1055–52

2010 ◽  
Vol 720 (2) ◽  
pp. 1635-1643 ◽  
Author(s):  
R. P. Mignani ◽  
G. G. Pavlov ◽  
O. Kargaltsev
Keyword(s):  
Proper Motion ◽  
Ultraviolet Spectrum ◽  
Middle Aged

scholarly journals EMERGENCE OF A FILAMENTARY STRUCTURE IN THE FIREBALL FROM GRB SPECTRA

2005 ◽  
Vol 14 (01) ◽  
pp. 97-105 ◽  
Author(s):  
REMO RUFFINI ◽  
CARLO LUCIANO BIANCO ◽  
SHE-SHENG XUE ◽  
PASCAL CHARDONNET ◽  
FEDERICO FRASCHETTI ◽  
...  
Keyword(s):  
Radio Emission ◽  
Gamma Ray ◽  
Surrounding Medium ◽  
Effective Area ◽  
Gamma Ray Bursts ◽  
Moving Frame ◽  
Filamentary Structure ◽  
X Ray ◽  
Spectral Changes ◽  
Analytic Expressions

It is shown that the concept of a fireball with a definite filamentary structure naturally emerges from the analysis of the spectra of Gamma-Ray Bursts (GRBs). These results, made possible by the recently obtained analytic expressions of the equitemporal surfaces in the GRB afterglow, depend crucially on the single parameter ℛ describing the effective area of the fireball emitting the X-ray and gamma-ray radiation. The X-ray and gamma-ray components of the afterglow radiation are shown to have a thermal spectrum in the co-moving frame of the fireball and originate from a stable shock front described self-consistently by the Rankine–Hugoniot equations. Precise predictions are presented on a correlation between spectral changes and intensity variations in the prompt radiation verifiable, e.g., by the Swift and future missions. The highly variable optical and radio emission depends instead on the parameters of the surrounding medium. The GRB 991216 is used as a prototype for this model.

scholarly journals GAMMA-RAY EMISSION FROM MASSIVE STAR FORMING REGIONS

2008 ◽  
Vol 17 (10) ◽  
pp. 1889-1894 ◽  
Author(s):  
A. T. ARAUDO ◽  
G. E. ROMERO ◽  
V. BOSCH-RAMON ◽  
J. M. PAREDES
Keyword(s):  
Gamma Ray ◽  
Surrounding Medium ◽  
Strong Shock ◽  
High Energy ◽  
Young Stellar Objects ◽  
Present Contribution ◽  
Stellar Objects ◽  
Star Forming ◽  
Star Forming Regions ◽  
The Impact

Recent radio observations support a picture for star formation where there is accretion of matter onto a central protostar with the ejection of molecular outflows that can affect the surrounding medium. The impact of a supersonic outflow on the ambient gas can produce a strong shock that could accelerate particles up to relativistic energies. Strong evidence for this has been the detection of nonthermal radio emission coming from the jet termination region of some young massive stars. In the present contribution, we study the possible high-energy emission due to the interaction of relativistic particles, electrons and protons, with the magnetic, photon and matter fields inside a giant molecular cloud. Electrons lose energy via relativistic Bremsstrahlung, synchrotron radiation and inverse Compton interactions, and protons cool mainly through inelastic collisions with atoms in the cloud. We conclude that some massive young stellar objects (YSOs) might be detectable at gamma-rays by next generation instruments, both satellite-borne and ground based.

Sign in / Sign up

Export Citation Format

Share Document