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Observations of Gamma-Ray Pulsars
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Observations of Gamma-Ray Pulsars

A special issue of Galaxies (ISSN 2075-4434).

Deadline for manuscript submissions: closed (18 February 2022) | Viewed by 12238

Special Issue Editor

Prof. Dr. Roberto Mignani

E-Mail Website
Guest Editor
INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, 20133 Milano, Italy
Interests: multi-wavelength astronomy; pulsars; neutron stars
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The NASA's Fermi Gamma-ray Space Telescope marked a revolution in pulsar gamma-ray astronomy, thanks to the unprecedented performance of its Large Area Telescope (LAT), having detected now more than 200 pulsars in gamma-rays, compared with the seven known before its launch in June 2008. About a quarter of these pulsars have been discovered in gamma-rays and they are still lacking a radio detection. The existence of a significant population of these “radio-quiet” pulsars was expected since the discovery of the prototype of this class, the gamma-ray pulsar Geminga, back in the early 1970s. Quite unexpectedly, about half of the gamma-ray pulsars discovered by Fermi are Gyr-old millisecond pulsars, which are a few orders of magnitude less energetic than the bulk of the young pulsar population. This discovery has triggered, among other things, a profound rethinking of gamma-ray emission models in pulsars. With Fermi extending its mission this reach harvest of gamma-ray pulsars is set to continue, possibly with the detection of those still hiding among the hundreds of unidentified gamma-ray sources.

It is now clear that this provides us with an unprecedentedly large and diverse sample to start characterising the pulsar spectra from the gamma rays to the optical, and understand how the complex radiation processes in pulsar magnetospheres work, which is key to understand the behaviour of relativistic particles and radiation under extreme magnetic fields.

The goals of this Special Issue are to set the state-of-the-art after ten years of pulsar observations by Fermi, present the results of their multi-wavelength follow-ups and how this helped to understand the pulsar emission physics, and outline the research plans for the next few years.

Prof. Dr. Roberto Mignani
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Galaxies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • pulsars
  • gamma-rays
  • multi-wavelength

Published Papers (4 papers)

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Research

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14 pages, 344 KiB  
Article
On the VHE Spectrum and Formation of the Teraelectronvolt Pulsed Emission of the Crab Pulsar
by Nino Chkheidze
Galaxies 2022, 10(2), 59; https://doi.org/10.3390/galaxies10020059 - 12 Apr 2022
Viewed by 1780
Abstract
In the present paper, a model for the pulsed γ-ray emission of the Crab pulsar from 0.01 GeV to 1 TeV in the context of synchrotron emission generated in the vicinity of a light cylinder is developed. The generation of such high [...] Read more.
In the present paper, a model for the pulsed γ-ray emission of the Crab pulsar from 0.01 GeV to 1 TeV in the context of synchrotron emission generated in the vicinity of a light cylinder is developed. The generation of such high energies through the synchrotron process requires the existence of very energetic plasma particles in pulsar magnetospheres. It is assumed that the emitting particles are ultra-relativistic primary beam electrons re-accelerated to very high energies due to the Landau damping process of a special type of parametrically driven Langmuir waves. This type of Langmuir wave carries energy released through the rotational slow-down of a pulsar and is very effective in supplying the resonant particles with energy from a natural reservoir. The model provides simultaneous generation of energetic γ-ray and low-frequency radio (0.1–1 GHz) emission in the same location of the pulsar magnetosphere. These two radiations processes are triggered by a single plasma process, namely excitation of the cyclotron instability. This provides a natural explanation for the observed coincidence of radio and γ-ray signals observed from the Crab pulsar. Full article
(This article belongs to the Special Issue Observations of Gamma-Ray Pulsars)
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9 pages, 536 KiB  
Article
Searching for Gamma-Ray Millisecond Pulsars: Selection of Candidates Revisited
by Xuejie Dai, Zhongxiang Wang and Jithesh Vadakkumthani
Galaxies 2019, 7(1), 31; https://doi.org/10.3390/galaxies7010031 - 07 Feb 2019
Viewed by 2676
Abstract
We are starting a project to find γ -ray millisecond pulsars (MSPs) among the unidentified sources detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope (Fermi), by radio observations. The selection of good candidates from analysis of the LAT [...] Read more.
We are starting a project to find γ -ray millisecond pulsars (MSPs) among the unidentified sources detected by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope (Fermi), by radio observations. The selection of good candidates from analysis of the LAT data is an important part of the project. Given that there is more than 10 years worth of LAT data and the advent of the newly released LAT 8-year point source list (FL8Y), we have conducted a selection analysis, on the basis of our previous analysis, and report the results here. Setting the requirements for the unidentified sources in FL8Y of Galactic latitudes | b | > 5 ∘ and curvature significances >3 σ , there are 202 sources with detection signficances >6 σ . We select 57 relatively bright ones (detection significances >15 σ ) and analyze their 10.2 years of LAT data. Their variability is checked to exclude variable sources (likely blazars), test statistic maps are constructed to avoid contaminated sources, and curvature significances are re-obtained and compared to their γ -ray spectra to exclude non-significant sources. In the end, 48 candidates are found. Based on the available information, mostly from multi-wavelength studies, we discuss the possible nature of several of the candidates. Most of these candidates are currently being observed with the 65-meter Shanghai Tian Ma Radio Telescope. Full article
(This article belongs to the Special Issue Observations of Gamma-Ray Pulsars)
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Review

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17 pages, 721 KiB  
Review
Relativistic Effects of Rotation in γ-ray Pulsars—Invited Review
by Zaza Osmanov
Galaxies 2021, 9(1), 6; https://doi.org/10.3390/galaxies9010006 - 18 Jan 2021
Cited by 4 | Viewed by 2823
Abstract
In this paper, we consider the relativistic effects of rotation in the magnetospheres of γ-ray pulsars. The paper reviews the progress achieved in this field during the last three decades. For this purpose, we examine the direct centrifugal acceleration of particles and [...] Read more.
In this paper, we consider the relativistic effects of rotation in the magnetospheres of γ-ray pulsars. The paper reviews the progress achieved in this field during the last three decades. For this purpose, we examine the direct centrifugal acceleration of particles and the corresponding limiting factors: the constraints due to the curvature radiation and the inverse Compton scattering of electrons against soft photons. Based on the obtained results, the generation of parametrically excited Langmuir waves and the corresponding Landau–Langmuir centrifugal drive are studied. Full article
(This article belongs to the Special Issue Observations of Gamma-Ray Pulsars)
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27 pages, 1600 KiB  
Review
High Energy Radiation from Spider Pulsars
by Chung Yue Hui and Kwan Lok Li
Galaxies 2019, 7(4), 93; https://doi.org/10.3390/galaxies7040093 - 13 Dec 2019
Cited by 21 | Viewed by 3668
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Observations of Gamma-Ray Pulsars)
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