A. Abramowski

Locating the very high energy source in the Galactic Centre with milliarcsecond accuracy

Very high-energyγ-rays (VHE; E>100 GeV) have been detected from the direction of the Galactic Centre up to energies E >10 TeV. Up to now, the origin of this emission is unknown due to the limited positional accuracy of the observing inst ruments. One of the counterpart candidates is the super-massive black hole (SMBH) Sgr A . If the VHE emission is produced within ≈ 10 cm ≈ 1000 rG (rG = GM/c is the Schwarzschild radius) of the SMBH, a decrease of the VHE photon flux in the energy range 100–300 Ge V is xpected whenever an early type or giant star approaches the line of sight withi n ≈ milli-arcseconds (mas). The dimming of the flux is due to absorption by pair-production of the VHE photons in the soft photon field of the star, an effect we refer to as pair-product ion eclipse (PPE). Based upon the currently known orbits of stars in the inner arcsecond of the Galaxy we find that PPEs lead to a systematic dimming in the 100–300 GeV band at the level of a few per cent and lasts for several weeks. Since the PPE affects only a narrow energy ban d and is well correlated with the passage of the star, it can be clearly discriminated agai nst other systematic or even sourceintrinsic effects. While the effect is too small to be observ able with the current generation of VHE detectors, upcoming high count-rate experiments lik e the Cherenkov telescope array (CTA) will be sufficiently sensitive. Measuring the tempora l signature of the PPE bears the potential to locate the position and size of the VHE emitting re ion within the inner 1000rG or in the case of a non-detection exclude the immediate envir o ment of the SMBH as the site of γ-ray production altogether.

Discovery of variable VHE γ-ray emission from the binary system 1FGL J1018.6–5856

Re-observations with the H.E.S.S. telescope array of the very-high-energy (VHE) source HESS J1018-589 A coincident with the Fermi-LAT

Discovery of gamma-ray emission from the extragalactic pulsar wind nebula N157B with the High Energy Stereoscopic System

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Time‐dependent absorption of very high‐energy gamma‐rays from the Galactic center by pair‐production

-ray binary 1FGL J1018.6-5856 have resulted in a source detection significance of more than 9

Contributions of the High Energy Stereoscopic System (H.E.S.S.) to the 35th International Cosmic Ray Conference (ICRC), Busan, Korea

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The high-energy γ-ray emission of AP Librae (Research Note)

, and the detection of variability (

HESS J1640-465 - an exceptionally luminous TeV gamma-ray SNR

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Discovery of hard-spectrum γ-ray emission from the BL Lacertae object 1 ES 0414+009

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