H. Abdalla

North-West University

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A. Wierzcholska

Institute of Nuclear Physics, Polish Academy of Sciences

Nu. Komin

University of the Witwatersrand

L. Mohrmann

Max Planck Institute for Nuclear Physics

J. A. Hinton

Max Planck Institute for Nuclear Physics

R. López-Coto

Instituto de Astrofísica de Andalucía

B. Khélifi

Université Paris Cité

P. T. O’Brien

University of Leicester

D. A. Sánchez

Centre National de la Recherche Scientifique

R. Terrier

Laboratoire AstroParticule et Cosmologie

J. Veh

Friedrich-Alexander-Universität Erlangen-Nürnberg

Cooperative Institutions

Centre National de la Recherche Scientifique

708

California Institute of Technology

339

Consejo Nacional de Investigaciones Científicas y Técnicas

293

Université Paris Cité

288

Institut National de Physique Nucléaire et de Physique des Particules

239

Goddard Space Flight Center

225

Campbell Collaboration

221

Commissariat à l'Énergie Atomique et aux Énergies Alternatives

219

National Institute for Astrophysics

216

University of Alaska Anchorage

194

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

Astronomy and Astrophysics (2019)

H. Abdalla F. Aharonian F. Ait Benkhali E. O. Angüner Masanori Arakawa

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 hours to 53 hours. In addition we observed SN 2016adj as a target of opportunity in February 2016 for 13 hours. 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 $\sim$10$^{-13}$ cm$^{-2}$s$^{-1}$ are established, corresponding to upper limits on the luminosities in the range $\sim$2 $\times$ 10$^{39}$ erg s$^{-1}$ to $\sim$1 $\times$ 10$^{42}$ 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 $\sim$2 $\times 10^{-5}$ and $\sim$2 $\times 10^{-3}$M$_{\odot}$yr$^{-1}$ under reasonable assumptions on the particle acceleration parameters.

10.1051/0004-6361/201935242

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Citations (14)

VizieR Online Data Catalog: H.E.S.S. Galactic Plane Survey (HESS+, 2018)

VizieR Online Data Catalog (2018)

H. Abdalla A. Abramowski F. Aharonian F. Ait Benkhali E. O. Anguener

Galactic plane

Source

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The H.E.S.S. Galactic plane survey

Astronomy and Astrophysics (2018)

H. Abdalla A. Abramowski F. Aharonian F. Ait Benkhali E. O. Angüner

We present the results of the most comprehensive survey of the Galactic plane in very high-energy (VHE) gamma-rays, including a public release of Galactic sky maps, a catalog of VHE sources, and the discovery of 16 new sources of VHE gamma-rays. The High Energy Spectroscopic System (H.E.S.S.) Galactic plane survey (HGPS) was a decade-long observation program carried out by the H.E.S.S. I array of Cherenkov telescopes in Namibia from 2004 to 2013. The observations amount to nearly 2700 h of data, covering the Galactic plane at longitudes from l = 250 deg to 65 deg and latitudes |b| < 3 deg. In addition to the unprecedented spatial coverage, the HGPS also features a relatively high angular resolution (0.08 deg), sensitivity (1.5% Crab flux for point-like sources), and energy range (0.2-100 TeV). We constructed a source catalog with a systematic procedure for both source detection and characterization of morphology and spectrum. We present this method, including the introduction of a model component to account for unresolved, large-scale emission along the Galactic plane. In total, the resulting HGPS catalog contains 78 VHE sources, of which 14 are not reanalyzed here. Where possible, we provide a firm identification of the VHE source or plausible associations with sources in other astronomical catalogs. We also studied the characteristics of the VHE sources with source parameter distributions. 16 new sources were previously unknown or unpublished, and we individually discuss their identifications or possible associations. We firmly identified 31 sources as pulsar wind nebulae (PWNe), supernova remnants (SNRs), composite SNRs, or gamma-ray binaries. Among the 47 sources not yet identified, most of them (36) have possible associations with cataloged objects, notably PWNe and energetic pulsars that could power VHE PWNe.

Galactic plane

Point source

10.1051/0004-6361/201732098

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Citations (350)

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

Astronomy and Astrophysics (2017)

H. Abdalla A. Abramowski F. Aharonian F. Ait Benkhali A. G. Akhperjanian

The nine-year H.E.S.S. Galactic Plane Survey (HGPS) 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 $\dot{E}$. This seems to be caused both by an increase of extension with decreasing $\dot{E}$, and hence with time, compatible with a power law $R_\mathrm{PWN}(\dot{E}) \sim \dot{E}^{-0.65 \pm 0.20}$, and by a mild decrease of TeV gamma-ray luminosity with decreasing $\dot{E}$, compatible with $L_{1-10\,\mathrm{TeV}} \sim \dot{E}^{0.59 \pm 0.21}$. We also find that the offsets of pulsars with respect to the wind nebula centres 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 $L_{1-10\,\mathrm{TeV}}/\dot{E}$. In addition to 14 HGPS sources considered as firmly identified pulsar wind nebulae and 5 additional pulsar wind nebulae taken from literature, we find 10 HGPS sources that form 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.

Galactic plane

Pulsar wind nebula

10.1051/0004-6361/201629377

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Citations (162)

Multi-messenger Observations of a Binary Neutron Star Merger

B. P. Abbott R. Abbott T. D. Abbott F. Acernese K. Ackley

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of $\sim$1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg$^2$ at a luminosity distance of $40^{+8}_{-8}$ Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Msun. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at $\sim$40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over $\sim$10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position $\sim$9 and $\sim$16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. (Abridged)

Kilonova

10.22323/1.362.0019

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Citations (1,712)

Sensitivity of the Cherenkov Telescope Array for probing cosmology and fundamental physics with gamma-ray propagation

Journal of Cosmology and Astroparticle Physics (2021)

H. Abdalla H. Abe F. Acero A. Acharyya R. Adam

The Cherenkov Telescope Array (CTA), the new-generation ground-based observatory for γ astronomy, provides unique capabilities to address significant open questions in astrophysics, cosmology, and fundamental physics. We study some of the salient areas of γ cosmology that can be explored as part of the Key Science Projects of CTA, through simulated observations of active galactic nuclei (AGN) and of their relativistic jets. Observations of AGN with CTA will enable a measurement of γ absorption on the extragalactic background light with a statistical uncertainty below 15% up to a redshift z=2 and to constrain or detect γ halos up to intergalactic-magnetic-field strengths of at least 0.3 pG . Extragalactic observations with CTA also show promising potential to probe physics beyond the Standard Model. The best limits on Lorentz invariance violation from γ astronomy will be improved by a factor of at least two to three. CTA will also probe the parameter space in which axion-like particles could constitute a significant fraction, if not all, of dark matter. We conclude on the synergies between CTA and other upcoming facilities that will foster the growth of γ cosmology.

Cherenkov Telescope Array

Extragalactic background light

Observational cosmology

Astroparticle physics

10.1088/1475-7516/2021/02/048

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Citations (20)

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

Astronomy and Astrophysics (2017)

H. Abdalla A. Abramowski F. Aharonian F. Ait Benkhali A. G. Akhperjanian

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 $\geq 0.1$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 \textit{Fermi}-LAT energy regime resulted in flux upper limits for 27 candidates listed in the E-BOSS catalogue. Here we perform the first systematic search for VHE gamma-ray emission from bow shocks of runaway stars. 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. 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. 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.

Rotational energy

10.1051/0004-6361/201630151

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Citations (17)