scholarly journals Statistics of VHE γ-rays in temporal association with radio giant pulses from the Crab pulsar

2020 ◽  
Vol 634 ◽  
pp. A25 ◽  
Author(s):  
◽  
M. L. Ahnen ◽  
S. Ansoldi ◽  
L. A. Antonelli ◽  
C. Arcaro ◽  
...  
Keyword(s):  
Radio Telescope ◽  
Gamma Ray ◽  
High Energy ◽  
Statistical Correlation ◽  
Temporal Association ◽  
Time Lags ◽  
Crab Pulsar ◽  
Giant Pulses ◽  
Upper Limits ◽  
Very High Energy

Aims. The aim of this study is to search for evidence of a common emission engine between radio giant pulses (GPs) and very-high-energy (VHE, E >  100 GeV) γ-rays from the Crab pulsar. Methods. We performed 16 h of simultaneous observations of the Crab pulsar at 1.4 GHz with the Effelsberg radio telescope and the Westerbork Synthesis Radio Telescope (WSRT), and at energies above 60 GeV we used the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) telescopes. We searched for a statistical correlation between the radio and VHE γ-ray emission with search windows of different lengths and different time lags to the arrival times of a radio GP. A dedicated search for an enhancement in the number of VHE γ-rays correlated with the occurrence of radio GPs was carried out separately for the P1 and P2 phase ranges, respectively. Results. In the radio data sample, 99444 radio GPs were detected. We find no significant correlation between the GPs and VHE photons in any of the search windows. Depending on phase cuts and the chosen search windows, we find upper limits at a 95% confidence level on an increase in VHE γ-ray events correlated with radio GPs between 7% and 61% of the average Crab pulsar VHE flux for the P1 and P2 phase ranges, respectively. This puts upper limits on the flux increase during a radio GP between 12% and 2900% of the pulsed VHE flux, depending on the search window duration and phase cuts. This is the most stringent upper limit on a correlation between γ-ray emission and radio GPs reported so far.

scholarly journals Systematic search for very-high-energy gamma-ray emission from bow shocks of runaway stars

2018 ◽  
Vol 612 ◽  
pp. A12 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Bow Shock ◽  
Systematic Search ◽  
Upper Limits ◽  
Very High Energy ◽  
Bow Shocks ◽  
Gamma Ray Emission ◽  
Runaway Stars ◽  
Very High

Context. Runaway stars form bow shocks by ploughing through the interstellar medium at supersonic speeds and are promising sources of non-thermal emission of photons. One of these objects has been found to emit non-thermal radiation in the radio band. This triggered the development of theoretical models predicting non-thermal photons from radio up to very-high-energy (VHE, E ≥ 0.1 TeV) gamma rays. Subsequently, one bow shock was also detected in X-ray observations. However, the data did not allow discrimination between a hot thermal and a non-thermal origin. Further observations of different candidates at X-ray energies showed no evidence for emission at the position of the bow shocks either. A systematic search in the Fermi-LAT energy regime resulted in flux upper limits for 27 candidates listed in the E-BOSS catalogue.Aim. Here we perform the first systematic search for VHE gamma-ray emission from bow shocks of runaway stars.Methods. Using all available archival H.E.S.S. data we search for very-high-energy gamma-ray emission at the positions of bow shock candidates listed in the second E-BOSS catalogue release. Out of the 73 bow shock candidates in this catalogue, 32 have been observed with H.E.S.S.Results. None of the observed 32 bow shock candidates in this population study show significant emission in the H.E.S.S. energy range. Therefore, flux upper limits are calculated in five energy bins and the fraction of the kinetic wind power that is converted into VHE gamma rays is constrained.Conclusions. Emission from stellar bow shocks is not detected in the energy range between 0.14 and 18 TeV.The resulting upper limits constrain the level of VHE gamma-ray emission from these objects down to 0.1–1% of the kinetic wind energy.

scholarly journals HESS upper limits on very high energy gamma-ray emission from the microquasar GRS 1915+105

2009 ◽  
Vol 508 (3) ◽  
pp. 1135-1140 ◽  
Author(s):  
◽  
F. Acero ◽  
F. Aharonian ◽  
A. G. Akhperjanian ◽  
G. Anton ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
High Energy Gamma ◽  
Upper Limits ◽  
Very High Energy ◽  
Energy Gamma ◽  
Gamma Ray Emission ◽  
Very High

scholarly journals The population of TeV pulsar wind nebulae in the H.E.S.S. Galactic Plane Survey

2018 ◽  
Vol 612 ◽  
pp. A2 ◽  
Author(s):  
◽  
H. Abdalla ◽  
A. Abramowski ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Galactic Plane ◽  
High Energy ◽  
Pulsar Wind Nebulae ◽  
Upper Limits ◽  
Very High Energy ◽  
Consistent Picture ◽  
Pulsar Wind ◽  
Asymmetric Environment ◽  
First Time

The nine-year H.E.S.S. Galactic Plane Survey (HGPS) has yielded the most uniform observation scan of the inner Milky Way in the TeV gamma-ray band to date. The sky maps and source catalogue of the HGPS allow for a systematic study of the population of TeV pulsar wind nebulae found throughout the last decade. To investigate the nature and evolution of pulsar wind nebulae, for the first time we also present several upper limits for regions around pulsars without a detected TeV wind nebula. Our data exhibit a correlation of TeV surface brightness with pulsar spin-down power Ė. This seems to be caused both by an increase of extension with decreasing Ė, and hence with time, compatible with a power law RPWN(Ė) ~Ė−0.65±0.20, and by a mild decrease of TeV gamma-ray luminosity with decreasing Ė, compatible with L1−10 TeV ~Ė0.59±0.21. We also find that the offsets of pulsars with respect to the wind nebula centre with ages around 10  kyr are frequently larger than can be plausibly explained by pulsar proper motion and could be due to an asymmetric environment. In the present data, it seems that a large pulsar offset is correlated with a high apparent TeV efficiency L1−10 TeV∕Ė. In addition to 14 HGPS sources considered firmly identified pulsar wind nebulae and 5 additional pulsar wind nebulae taken from literature, we find 10 HGPS sources that are likely TeV pulsar wind nebula candidates. Using a model that subsumes the present common understanding of the very high-energy radiative evolution of pulsar wind nebulae, we find that the trends and variations of the TeV observables and limits can be reproduced to a good level, drawing a consistent picture of present-day TeV data and theory.

scholarly journals The Crab Pulsar and Nebula as Seen in Gamma-Rays

Universe ◽  
2021 ◽  
Vol 7 (11) ◽  
pp. 448
Author(s):  
Elena Amato ◽  
Barbara Olmi
Keyword(s):  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Crab Pulsar ◽  
Gamma Ray Astronomy ◽  
Very High Energy ◽  
Energy Gamma ◽  
The Crab Nebula ◽  
The Impact ◽  
Very High

Slightly more than 30 years ago, Whipple detection of the Crab Nebula was the start of Very High Energy gamma-ray astronomy. Since then, gamma-ray observations of this source have continued to provide new surprises and challenges to theories, with the detection of fast variability, pulsed emission up to unexpectedly high energy, and the very recent detection of photons with energy exceeding 1 PeV. In this article, we review the impact of gamma-ray observations on our understanding of this extraordinary accelerator.

scholarly journals Very High Energy Gamma-ray Observations of AGN with CANGAROO

2002 ◽  
Vol 19 (1) ◽  
pp. 26-28 ◽  
Author(s):  
Kyoshi Nishijima
Keyword(s):  
Energy Range ◽  
Energy Region ◽  
Gamma Ray ◽  
High Energy ◽  
Large Zenith Angle ◽  
Upper Limits ◽  
Very High Energy ◽  
Energy Gamma ◽  
Bl Lacs ◽  
Very High

AbstractWe have observed eight AGN since 1993 in the energy region above several hundred GeV using the CANGAROO telescopes. We observed Mrk 421 for ten nights with the CANGAROO-II 10 m telescope during its active state in early 2001 using the very large zenith angle technique. Our preliminary result implies the detection of gamma-ray emission from Mrk 421 in the energy range above 9.3 TeV. The high energy peaked BL Lacs (HBLs) PKS 2005–489 and PKS 2155–304 have been also observed. No statistically significant signals are found for both HBLs and flux upper limits are obtained. A summary of results of observations of AGN is presented in this paper.

scholarly journals MAGIC Upper Limits on the Very High Energy Emission from Gamma‐Ray Bursts

2007 ◽  
Vol 667 (1) ◽  
pp. 358-366 ◽  
Author(s):  
J. Albert ◽  
E. Aliu ◽  
H. Anderhub ◽  
P. Antoranz ◽  
A. Armada ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Energy Emission ◽  
Upper Limits ◽  
Very High Energy ◽  
High Energy Emission ◽  
Very High

scholarly journals Upper Limits on Gamma-ray Emission from Supernovae Serendipitously Observed with H.E.S.S.

2017 ◽  
Vol 12 (S331) ◽  
pp. 325-328 ◽  
Author(s):  
Rachel Simoni ◽  
Nigel Maxted ◽  
Mathieu Renaud ◽  
Jacco Vink
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Air Shower ◽  
Upper Limits ◽  
Very High Energy ◽  
Nearby Galaxies ◽  
Gamma Ray Emission ◽  
High Energy Emission ◽  
By Products ◽  
Very High

AbstractIt is hypothesized that some young supernovae might have the correct properties to accelerate cosmic rays, which in turn might generate gamma-ray emission by-products. We search for gamma-ray excesses towards supernovae in nearby galaxies which were serendipitously within the field of view of the HESS telescopes within a year of the supernova event. HESS cherenkov air-shower data collected between December 2003 and March 2015 were considered and compared to recent catalogs. Nine candidate supernovae were identified and analysed. No significant emission from these supernovae has been found, and upper limits for their very high energy emission are reported.

scholarly journals Upper limits on very-high-energy gamma-ray emission from core-collapse supernovae observed with H.E.S.S.

2019 ◽  
Vol 626 ◽  
pp. A57 ◽  
Author(s):  
◽  
H. Abdalla ◽  
F. Aharonian ◽  
F. Ait Benkhali ◽  
E. O. Angüner ◽  
...  
Keyword(s):  
Gamma Ray ◽  
Cosmic Ray ◽  
High Energy ◽  
Core Collapse ◽  
Upper Limits ◽  
Very High Energy ◽  
Energy Gamma ◽  
Stereoscopic System ◽  
Gamma Ray Emission ◽  
Progenitor Stars

Young core-collapse supernovae with dense-wind progenitors may be able to accelerate cosmic-ray hadrons beyond the knee of the cosmic-ray spectrum, and this may result in measurable gamma-ray emission. We searched for gamma-ray emission from ten supernovae observed with the High Energy Stereoscopic System (H.E.S.S.) within a year of the supernova event. Nine supernovae were observed serendipitously in the H.E.S.S. data collected between December 2003 and December 2014, with exposure times ranging from 1.4 to 53 h. In addition we observed SN 2016adj as a target of opportunity in February 2016 for 13 h. No significant gamma-ray emission has been detected for any of the objects, and upper limits on the >1 TeV gamma-ray flux of the order of ~10−13 cm−2s−1 are established, corresponding to upper limits on the luminosities in the range ~2 × 1039 to ~1 × 1042 erg s−1. These values are used to place model-dependent constraints on the mass-loss rates of the progenitor stars, implying upper limits between ~2 × 10−5 and ~2 × 10−3 M⊙ yr−1 under reasonable assumptions on the particle acceleration parameters.

MAGIC RESULTS ON BINARY SYSTEMS

2012 ◽  
Vol 08 ◽  
pp. 67-72
Author(s):  
◽  
ROBERTA ZANIN ◽  
OSCAR BLANCH ◽  
JUAN CORTINA ◽  
TOBIAS JOGLER ◽  
...  
Keyword(s):  
Binary Systems ◽  
Gamma Ray ◽  
High Energy ◽  
Significant Activity ◽  
X Ray ◽  
Upper Limits ◽  
Very High Energy ◽  
X Ray Binaries ◽  
Spectral States ◽  
Significant Effort

Three X-ray binary systems have been unambiguously detected at TeV energies: LS 5039, LS I +61° +303, PSR B1259-63. Additionally, the TeV source HESS J0632+057 has been found to be a new binary system. The recent detection of the microquasar Cygnus X-3, between 100 MeV and few GeV, confirms that also this sub-class of accreting binaries displaying radio relativistic jets provides interesting candidates for very-high-energy (VHE) gamma-ray observations. The MAGIC telescopes made a significant effort to search for signals from X-ray binaries. This article will present the new results on LS I 61° +303, which show a reduction in the VHE γ-ray flux in the periodic outburst phase with respect to previous campaigns. MAGIC observed also HESS J0632 +057 in 2010 and 2011, covering an X-ray outburst reported by Swift in February 2011. These observations show significant activity in VHE gamma-rays temporally coincident with the X-ray outburst. In addition, this article will review MAGIC results on the microquasars Cygnus X-3, Cygnus X-1, and Scorpius X-1 which report constraining flux upper limits in different X-ray spectral states and as well as during flux enhancements at high energies.

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