scholarly journals Discovery and Timing of Three Millisecond Pulsars in Radio and Gamma-Rays with the Giant Metrewave Radio Telescope and Fermi Large Area Telescope

2021 ◽  
Vol 910 (2) ◽  
pp. 160
Author(s):  
B. Bhattacharyya ◽  
J. Roy ◽  
T. J. Johnson ◽  
P. S. Ray ◽  
P. C. C. Freire ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Gamma Rays ◽  
Large Area ◽  
Millisecond Pulsars

scholarly journals On a Possible Origin of the Gamma-ray Excess around the Galactic Center

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1432
Author(s):  
Dmitry O. Chernyshov ◽  
Andrei E. Egorov ◽  
Vladimir A. Dogiel ◽  
Alexei V. Ivlev
Keyword(s):  
Dark Matter ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Alternative Explanation ◽  
Gamma Ray ◽  
Galactic Center ◽  
The Self ◽  
Large Area ◽  
Mhd Turbulence ◽  
The Standard Model

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

Gamma rays from millisecond pulsars

1991 ◽  
Vol 12 (1) ◽  
pp. 17-25 ◽  
Author(s):  
D. Bhattacharya ◽  
G Srinivasan
Keyword(s):  
Gamma Rays ◽  
Millisecond Pulsars

scholarly journals G279.0+1.1: a new extended source of high-energy gamma-rays

2020 ◽  
Vol 492 (4) ◽  
pp. 5980-5986
Author(s):  
M Araya
Keyword(s):  
Spectral Index ◽  
Gamma Rays ◽  
Gamma Ray ◽  
High Energy ◽  
Particle Spectrum ◽  
Large Area ◽  
Extended Source ◽  
The North ◽  
Energy Gamma ◽  
High Energy Emission

ABSTRACT G279.0+1.1 is a supernova remnant (SNR) with poorly known parameters, first detected as a dim radio source and classified as an evolved system. An analysis of data from the Fermi-Large Area Telescope (LAT) revealing for the first time an extended source of gamma-rays in the region is presented. The diameter of the GeV region found is ${\sim} 2{^{\circ}_{.}}8$, larger than the latest estimate of the SNR size from radio data. The gamma-ray emission covers most of the known shell and extends further to the north and east of the bulk of the radio emission. The photon spectrum in the 0.5–500 GeV range can be described by a simple power law, $\frac{\mathrm{ d}N}{\mathrm{ d}E} \propto E^{-\Gamma }$, with a spectral index of Γ = 1.86 ± 0.03stat ± 0.06sys. In the leptonic scenario, a steep particle spectrum is required and a distance lower than the previously estimated value of 3 kpc is favoured. The possibility that the high-energy emission results from electrons that already escaped the SNR is also investigated. A hadronic scenario for the gamma-rays yields a particle spectral index of ∼2.0 and no significant constraints on the distance. The production of gamma-rays in old SNRs is discussed. More observations of this source are encouraged to probe the true extent of the shell and its age.

scholarly journals Radio counterparts of gamma-ray pulsars

2012 ◽  
Vol 8 (S291) ◽  
pp. 87-92
Author(s):  
L. Guillemot
Keyword(s):  
Gamma Ray ◽  
Population Studies ◽  
Radio Observations ◽  
Large Area ◽  
Millisecond Pulsars ◽  
Follow Up Studies ◽  
First Time

AbstractObservations of pulsars with the Large Area Telescope (LAT) on the Fermi satellite have revolutionized our view of the gamma-ray pulsar population. For the first time, a large number of young gamma-ray pulsars have been discovered in blind searches of the LAT data. More generally, the LAT has discovered many new gamma-ray sources whose properties suggest that they are powered by unknown pulsars. Radio observations of gamma-ray sources have been key to the success of pulsar studies with the LAT. For example, radio observations of LAT-discovered pulsars provide constraints on the relative beaming fractions, which are crucial for pulsar population studies. Also, radio searches of LAT sources with no known counterparts have been very efficient, with the discovery of over forty millisecond pulsars. I review radio follow-up studies of LAT-discovered pulsars and unidentified sources, and discuss some of the implications of the results.

scholarly journals Pulsar Searches at Effelsberg

2004 ◽  
Vol 218 ◽  
pp. 133-134 ◽  
Author(s):  
B. Klein ◽  
M. Kramer ◽  
P. Müller ◽  
R. Wielebinski
Keyword(s):  
Radio Telescope ◽  
Galactic Center ◽  
Millisecond Pulsars ◽  
Highly Dispersed ◽  
L Band ◽  
Under Construction ◽  
5 Ghz ◽  
Key Aspects ◽  
Pulsar Searches

We report on the progress of our search for highly dispersed pulsars near the Galactic Center at 5 GHz using the 100-m radio telescope in Effelsberg. We also present key aspects of our new survey for millisecond pulsars at 21 cm in parts of the northern sky. This survey will greatly benefit from the L-band multibeam receiver and a new FFT-based backend which are currently under construction at the MPIfR.

scholarly journals DISCOVERY OF TWO MILLISECOND PULSARS INFERMISOURCES WITH THE NANÇAY RADIO TELESCOPE

2011 ◽  
Vol 732 (1) ◽  
pp. 47 ◽  
Author(s):  
I. Cognard ◽  
L. Guillemot ◽  
T. J. Johnson ◽  
D. A. Smith ◽  
C. Venter ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Millisecond Pulsars

scholarly journals Rotation Measure variations for millisecond pulsars

2012 ◽  
Vol 8 (S291) ◽  
pp. 568-570
Author(s):  
Wenming Yan ◽  
R. N. Manchester ◽  
Na Wang
Keyword(s):  
Radio Telescope ◽  
Position Angle ◽  
Polarization Mode ◽  
Millisecond Pulsars ◽  
Pulsar Timing ◽  
Rotation Measure ◽  
The Mean ◽  
Pulsar Timing Array

AbstractAs part of the Parkes Pulsar Timing Array (PPTA) project, frequent observations of 20 millisecond pulsars are made using the Parkes 64-m radio telescope. Variations in the mean position angle of the 20 millisecond pulsars can be studied by the PPTA data being recorded in full-polarization mode. We briefly discuss these results.

scholarly journals Tracking dispersion measure variations of timing array pulsars with the GMRT

2012 ◽  
Vol 8 (S291) ◽  
pp. 432-434 ◽  
Author(s):  
Ujjwal Kumar ◽  
Yashwant Gupta ◽  
Willem van Straten ◽  
Stefan Osłowski ◽  
Jayanta Roy ◽  
...  
Keyword(s):  
Solar Wind ◽  
Solar Corona ◽  
Radio Telescope ◽  
Line Of Sight ◽  
Dispersion Measure ◽  
Millisecond Pulsars ◽  
Preliminary Comparison ◽  
Pulsar Timing ◽  
Single Epoch ◽  
Pulsar Timing Array

AbstractWe present the results from nearly three years of monitoring of the variations in dispersion measure (DM) along the line-of-sight to 11 millisecond pulsars using the Giant Metrewave Radio Telescope (GMRT). These results demonstrate accuracies of single epoch DM estimates of the order of 5 × 10−4 cm−3 pc. A preliminary comparison with the Parkes Pulsar Timing Array (PPTA) data shows that the measured DM fluctuations are comparable. We show effects of DM variations due to the solar wind and solar corona and compare with the existing models.

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