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

Schulz, A.; Ackermann, M.; Buehler, R.; Mayer, M.; Klepser, S.

doi:10.1051/0004-6361/201630151

Cited by 14 publications

(1 citation statement)

References 31 publications

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“…The publication including final quantitative statements is forthcoming H.E.S.S. Collaboration et al [17]. The future Cherenkov Telescope Array (CTA, Hinton et al [18]), with its improved sensitivity and resolution, will give more insights in the nature of bow shocks of runaway stars.…”

Section: Resultsmentioning

confidence: 99%

Observations of bow shocks of runaway stars with H.E.S.S.

Schulz¹,

Haupt²,

Klepser³

et al. 2017

AIP Conference Proceedings

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Abstract. Runaway stars form bow shocks by sweeping up interstellar matter in their direction of motion. Theoretical models predict a spectrally wide non-thermal component reaching up to gamma-ray energies at a flux level detectable with current instruments. They were motivated by a detection of non-thermal radio emission from the bow shock of BD+43• 3654 and a possible detection of non-thermal X-rays from AE Aurigae. A search in the high-energy regime using data from Fermi-LAT resulted in flux upper limits for 27 candidates listed in the first E-BOSS catalogue. We perform the first systematic search for TeV emission from bow shocks of runaway stars. Using all available archival H.E.S.S. I data we search for very-high-energy gamma-ray emission at the positions of bow shock candidates listed in the second E-BOSS catalogue. This catalogue comprises 73 bow shock candidates, 32 of which have been observed with the H.E.S.S. telescopes. None of the observed bow shock candidates shows significant emission in the H.E.S.S. energy range. The resulting upper limits are used to constrain current models for non-thermal emission from these objects.

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Section: Resultsmentioning

confidence: 99%

Observations of bow shocks of runaway stars with H.E.S.S.

Schulz¹,

Haupt²,

Klepser³

et al. 2017

AIP Conference Proceedings

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

Abdalla¹,

Abramowski²,

Aharonian³

et al. 2018

A&A

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155

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We present the results of the most comprehensive survey of the Galactic plane in very high-energy (VHE) γ-rays, including a public release of Galactic sky maps, a catalog of VHE sources, and the discovery of 16 new sources of VHE γ-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 quality-selected data, covering the Galactic plane at longitudes from ℓ = 250° to 65° and latitudes |b|≤ 3°. In addition to the unprecedented spatial coverage, the HGPS also features a relatively high angular resolution (0.08° ≈ 5 arcmin mean point spread function 68% containment radius), sensitivity (≲1.5% Crab flux for point-like sources), and energy range (0.2–100 TeV). We constructed a catalog of VHE γ-ray sources from the HGPS data set with a systematic procedure for both source detection and characterization of morphology and spectrum. We present this likelihood-based method in detail, 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, for example, due to their complex morphology, namely shell-like sources and the Galactic center region. 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.

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Multi-zone non-thermal radiative model for stellar bowshocks

Palacio

Bosch‐Ramon

Müller

et al. 2018

A&A

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Context. Runaway stars produce bowshocks that are usually observed at infrared (IR) wavelengths. Non-thermal radio emission has been detected so far only from the bowshock of BD+43 • 3654, whereas the detection of non-thermal radiation from these bowshocks at high energies remains elusive. Aims. We aim at characterising in detail the radio, X-ray, and γ-ray emission from stellar bowshocks accounting for the structure of the region of interaction between the stellar wind and its environment. Methods. We develop a broadband-radiative, multi-zone model for stellar bowshocks that takes into account the spatial structure of the emitting region and the observational constraints. The model predicts the evolution and the emission of the relativistic particles accelerated and streaming together with the shocked flow. Results. We present broadband non-thermal spectral energy distributions for different scenarios, synthetic radio-cm synchrotron maps that reproduce the morphology of BD+43 • 3654, and updated predictions in X-ray and γ-ray energy ranges. We also compare the results of the multi-zone model applied in this work with those of a refined one-zone model. Conclusions.A multi-zone model provides better constraints than a one-zone model on the relevant parameters, namely the magnetic field intensity and the amount of energy deposited in non-thermal particles. However, one-zone models can be improved by carefully characterising the intensity of the IR dust photon field and the escape rate of the plasma from the shocked region. Finally, comparing observed radio maps with those obtained from a multi-zone model enables constraints to be obtained on the direction of stellar motion with respect to the observer.

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

Cited by 14 publications

References 31 publications

Observations of bow shocks of runaway stars with H.E.S.S.

Observations of bow shocks of runaway stars with H.E.S.S.

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

Multi-zone non-thermal radiative model for stellar bowshocks

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