Cygnus survey with the Giant Metrewave Radio Telescope at 325 and 610 MHz: the catalog

Context. Observations at the radio continuum band below the gigahertz band are key when the nature and properties of nonthermal sources are investigated because their radio radiation is strongest at these frequencies. The low radio frequency range is therefore the best to spot possible counterparts to very high-energy (VHE) sources: relativistic particles of the same population are likely to be involved in radio and high-energy radiation processes. Some of these counterparts to VHE sources can be stellar sources. Aims. The Cygnus region in the northern sky is one of the richest in this type of sources that are potential counterparts to VHE sources. We surveyed the central ∼15 sq deg of the Cygnus constellation at the 325 and 610 MHz bands with angular resolutions and sensitivities of 10″ and 6″, and 0.5 and 0.2 mJy beam−1, respectively. Methods. The data were collected during 172 h in 2013–2017, using the Giant Metrewave Radio Telescope with 32 MHz bandwidth, and were calibrated using the SPAM routines. The source extraction was carried out with the PyBDSF tool, followed by verification through visual inspection of every putative catalog candidate source in order to determine its reliability. Results. In this first paper we present the catalog of sources, consisting of 1048 sources at 325 MHz and 2796 sources at 610 MHz. By cross-matching the sources from both frequencies with the objects of the SIMBAD database, we found possible counterparts for 143 of them. Most of the sources from the 325-MHz catalog (993) were detected at the 610 MHz band, and their spectral index α was computed adopting S(ν) ∝ να. The maximum of the spectral index distribution is at α = −1, which is characteristic of nonthermal emitters and might indicate an extragalactic population.

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New composite supernova remnant toward HESS J1844-030?

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834734 ◽

2019 ◽

Vol 626 ◽

pp. A65

Author(s):

A. Petriella

Keyword(s):

Supernova Remnant ◽

High Energy ◽

Radio Continuum ◽

Pressure Balance ◽

High Energy Radiation ◽

X Ray ◽

Galactic Source ◽

Very High Energy ◽

The Magnetic Field ◽

Very High

Aims. HESS J1844-030 is a newly confirmed TeV source in the direction of the X-ray pulsar wind nebula (PWN) candidate G29.4+0.1 and the complex radio source G29.37+0.1, which is likely formed by the superposition of a background radio galaxy and a Galactic supernova remnant (SNR). Many scenarios have been proposed to explain the origin of HESS J1844-030, based on several sources that are capable of producing very high energy radiation. We investigate the possible connection between the SNR, the PWN G29.4+0.1, and HESS J1844-030 to shed light on the astrophysical origin of the TeV emission. Methods. We performed an imaging and spectral study of the X-ray emission from the PWN G29.4+0.1 using archival observations obtained with the Chandra and XMM-Newton telescopes. Public radio continuum and HI data were used to derive distance constraints for the SNR that is linked to G29.37+0.1 and to investigate the interstellar medium where it is expanding. We applied a simple model of the evolution of a PWN inside an SNR to analyze the association between G29.4+0.1 and the radio emission from G29.37+0.1. We compared the spectral properties of the system with the population of TeV PWNe to investigate if HESS J1844-030 is the very high energy counterpart of the X-ray PWN G29.4+0.1. Results. Based on the morphology and spectral behavior in the X-ray band, we conclude that G29.4+0.1 is a PWN and that a point source embedded on it is the powering pulsar. The HI data revealed that the SNR linked to G29.37+0.1 is a Galactic source at 6.5 kpc and expanding in a nonuniform medium. From the analysis of the pulsar motion and the pressure balance at the boundary of X-ray emission, we conclude that G29.4+0.1 could be a PWN that is located inside its host remnant, forming a new composite SNR. Based on the magnetic field of the PWN obtained from the X-ray luminosity, we found that the population of electrons producing synchrotron radiation in the keV band can also produce IC photons in the TeV band. This suggests that HESS J1844-030 could be the very high energy counterpart of G29.4+0.1.

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

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317004689 ◽

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.

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Investigation of the WR 11 field at decimeter wavelengths

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834971 ◽

2019 ◽

Vol 625 ◽

pp. A99 ◽

Cited By ~ 1

Author(s):

P. Benaglia ◽

S. del Palacio ◽

C. H. Ishwara-Chandra ◽

M. De Becker ◽

N. L. Isequilla ◽

...

Keyword(s):

Spectral Index ◽

Thermal Emission ◽

Mass Loss Rate ◽

High Energy ◽

Low Frequencies ◽

Nonthermal Radio ◽

Short Period ◽

Radiation Processes ◽

Period System ◽

The Individual

The massive binary system WR 11 (γ2-Velorum) has recently been proposed as the counterpart of a Fermi source. If this association is correct, this system would be the second colliding wind binary detected in GeV γ-rays. However, the reported flux measurements from 1.4 to 8.64 GHz fail to establish the presence of nonthermal (synchrotron) emission from this source. Moreover, WR 11 is not the only radio source within the Fermi detection box. Other possible counterparts have been identified in archival data, some of which present strong nonthermal radio emission. We conducted arcsec-resolution observations toward WR 11 at very low frequencies (150–1400 MHz) where the nonthermal emission – if existent and not absorbed – is expected to dominate. We present a catalog of more than 400 radio emitters, among which a significant portion are detected at more than one frequency, including limited spectral index information. Twenty-one of these radio emitters are located within the Fermi significant emission. A search for counterparts for this last group pointed at MOST 0808–471; this source is 2′ away from WR 11 and is a promising candidate for high-energy emission, having a resolved structure along 325–1390 MHz. For this source, we reprocessed archive interferometric data up to 22.3 GHz and obtained a nonthermal radio spectral index of − 0.97 ± 0.09. However, multiwavelength observations of this source are required to establish its nature and to assess whether it can produce (part of) the observed γ-rays. WR 11 spectrum follows a spectral index of 0.74 ± 0.03 from 150 to 230 GHz, consistent with thermal emission. We interpret that any putative synchrotron radiation from the colliding-wind region of this relatively short-period system is absorbed in the photospheres of the individual components. Notwithstanding, the new radio data allowed us to derive a mass-loss rate of 2.5 × 10−5 M⊙ yr−1, which, according to the latest models for γ-ray emission in WR 11, would suffice to provide the required kinetic power to feed nonthermal radiation processes.

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Gamma-Ray Pulsar Emission Models

International Astronomical Union Colloquium ◽

10.1017/s0252921100041804 ◽

1996 ◽

Vol 160 ◽

pp. 315-322 ◽

Cited By ~ 1

Author(s):

Alice K. Harding

Keyword(s):

Spectral Index ◽

Gamma Ray ◽

High Energy ◽

Pulsar Emission ◽

High Energy Radiation ◽

X Ray ◽

Gamma Ray Detectors ◽

Emerging Patterns ◽

Increased Sensitivity ◽

Emission Models

AbstractWith the increased sensitivity of gamma-ray detectors on the Compton Gamma-Ray Observatory (CGRO) the number of presently known gamma-ray pulsars has grown. The new detections are beginning to provide clues to the origin of the high-energy radiation in the form of emerging patterns and correlations among observed quantities such as gamma-ray efficiency and spectral index vs. age. But there are still many questions about the location of the emission and its relation to the radio, optical and X-ray pulses. This paper will review models for gamma-ray emission from pulsars and will examine how well the detailed predictions of these models account for the existing observations.

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A new study towards PSR J1826–1334 and PSR J1826–1256 in the region of HESS J1825–137 and HESS J1826–130

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834590 ◽

2019 ◽

Vol 623 ◽

pp. A115 ◽

Cited By ~ 1

Author(s):

L. Duvidovich ◽

E. Giacani ◽

G. Castelletti ◽

A. Petriella ◽

L. Supán

Keyword(s):

High Energy ◽

Radio Continuum ◽

Very Large Array ◽

X Ray ◽

Compact Component ◽

New Radio ◽

Northern Border ◽

Inverse Compton ◽

Photon Index ◽

Very High Energy

Aims. The goal of this paper is to detect synchrotron emission from the relic electrons of the crushed pulsar wind nebula (PWN) HESS J1825−137 and to investigate the origin of the γ-ray emission from HESS J1826−130. Methods. The study of HESS J1825−137 was carried out on the basis of new radio observations centred at the position of PSR J1826−1334 performed with the Karl G. Jansky Very Large Array at 1.4 GHz in configurations B and C. To investigate the nature of HESS J1826−130, we reprocessed unpublished archival data obtained with XMM-Newton. Results. The new radio continuum image towards PSR J1826−1334 reveals a bright radio source, with the pulsar located in its centre, which suggests that this feature could be the radio counterpart of the compact component of the PWN detected at high energy. The new 1.4 GHz radio data do not reveal emission with an extension comparable with that observed in γ-rays for the HESS J1825−137 source. On the other hand, the XMM-Newton study of the region including PSR J1826−1256 reveals an elongated non-thermal X-ray emitting nebula with the pulsar located in the northern border and a tail towards the peak of the very high energy source. The spectrum is characterized by a power law with a photon index going from 1.6 around the pulsar to 2.7 in the borders of the nebula, a behaviour consistent with synchrotron cooling of electrons. From our X-ray analysis we propose that HESS J1826−130 is likely produced by the PWN powered by PSR J1826−1256 via the inverse Compton mechanism.

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The curing of organic coatings by high energy radiation processes

Progress in Organic Coatings ◽

10.1016/0300-9440(76)80008-2 ◽

1976 ◽

Vol 4 (4) ◽

pp. 225-249 ◽

Cited By ~ 14

Author(s):

S.E. Young

Keyword(s):

High Energy ◽

Organic Coatings ◽

High Energy Radiation ◽

Energy Radiation ◽

Radiation Processes

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Gamma-ray Bursts at the Highest Energies

Universe ◽

10.3390/universe7120503 ◽

2021 ◽

Vol 7 (12) ◽

pp. 503

Author(s):

Lara Nava

Keyword(s):

Gamma Ray ◽

Current Knowledge ◽

Spectral Component ◽

High Energy ◽

Gamma Ray Bursts ◽

Special Focus ◽

High Energy Radiation ◽

Energy Radiation ◽

Very High Energy ◽

Very High

Emission from Gamma-ray bursts is thought to be powered mainly by synchrotron radiation from energetic electrons. The same electrons might scatter these synchrotron seed photons to higher (>10 GeV) energies, building a distinct spectral component (synchrotron self-Compton, SSC). This process is expected to take place, but its relevance (e.g., the ratio between the SSC and synchrotron emitted power) is difficult to predict on the basis of current knowledge of physical conditions at GRB emission sites. Very high-energy radiation in GRBs can be produced also by other mechanisms, such as synchrotron itself (if PeV electrons are produced at the source), inverse Compton on external seed photons, and hadronic processes. Recently, after years of efforts, very high-energy radiation has been finally detected from at least four confirmed long GRBs by the Cherenkov telescopes H.E.S.S. and MAGIC. In all four cases, the emission has been recorded during the afterglow phase, well after the end of the prompt emission. In this work, I give an overview, accessible also to non-experts of the field, of the recent detections, theoretical implications, and future challenges, with a special focus on why very high-energy observations are relevant for our understanding of Gamma-ray bursts and which long-standing questions can be finally answered with the help of these observations.

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