1,022 research outputs found

    The Asian development bank on the eve of commencing activities

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    The Asian development bank on the eve of commencing activities

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    The HI absorption distance of HESS J1943+213 favours its extragalactic nature

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    The H.E.S.S. collaboration (Abramowski et al. 2011) dicovered a new TeV point-like source HESS J1943+213 in the Galactic plane and suggested three possible low-energy-band counterparts: a Îł\gamma-ray binary, a pulsar wind nebula (PWN), or a BL Lacertae object. We measure the distance to the radio counterpart G57.76-1.29 of HESS J1943+213. We analyze Very Large Array observations to obtain a reliable HI absorption spectrum.The resulting distance limit is ≄\ge 16 kpc. This distance strongly supports that HESS J1943+213 is an extragalactic source, consistent with the preferred counterpart of the HESS collaboration.Comment: 3 figures, 2 pages, A&A accepte

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

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    Very high energy (VHE) gamma-rays have been detected from the direction of the Galactic center. The H.E.S.S. Cherenkov telescopes have located this gamma-ray source with a preliminary position uncertainty of 8.5" per axis (6" statistic + 6" sytematic per axis). Within the uncertainty region several possible counterpart candidates exist: the Super Massive Black Hole Sgr A*, the Pulsar Wind Nebula candidate G359.95-0.04, the Low Mass X-Ray Binary-system J174540.0-290031, the stellar cluster IRS 13, as well as self-annihilating dark matter. It is experimentally very challenging to further improve the positional accuracy in this energy range and therefore, it may not be possible to clearly associate one of the counterpart candidates with the VHE-source. Here, we present a new method to investigate a possible link of the VHE-source with the near environment of Sgr A* (within approximately 1000 Schwarzschild radii). This method uses the time- and energy-dependent effect of absorption of gamma-rays by pair-production (in the following named pair-eclipse) with low-energy photons of stars closely orbiting the SMBH Sgr A*.Comment: 4 pages, 6 figures, Published in Proceedings of the 4th International Meeting on High Energy Gamma-Ray Astronomy (Gamma 08), Heidelber

    Exploring the nature of the unidentified VHE gamma-ray source HESS J1507-622

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    The nature of the first unidentified VHE gamma-ray source with significant angular offset from the Galactic plane of 3.5 degrees, HESS J1507-622, is explored. Fermi-LAT data in the high-energy (HE, 100 MeV < E < 100 GeV) gamma-ray range collected over 34 month are used to describe the spectral energy distribution (SED) of the source. HESS J1507-622 is detected in the Fermi energy range and its spectrum is best described by a power law in energy with Gamma=1.7 +/- 0.1 stat +/- 0.2_sys and integral flux between (0.3-300) GeV of F = (2.0 +/-0.5_stat +/- 1.0_sys) x 10^-9 cm^-2 s^-1. With the available data it is not possible to discriminate between a hadronic and a leptonic scenario for HESS J1507-622. The location and compactness of the source indicate a considerable physical offset from the Galactic plane for this object. In case of a multiple-kpc distance, this challenges a pulsar wind nebula (PWN) origin for HESS J1507-622 since the time of travel for a pulsar born in the Galactic disk to reach such a location would exceed the inverse Compton (IC) cooling time of electrons that are energetic enough to produce VHE gamma-rays. However, an origin of this gamma-ray source connected to a pulsar that was born off the Galactic plane in the explosion of a hypervelocity star cannot be excluded. The nature of HESS J1507-622 is still unknown to date, and a PWN scenario cannot be ruled out in general. On the contrary HESS J1507-622 could be the first discovered representative of a population of spatially extended VHE gamma-ray emitters with HE gamma-ray counterpart that are located at considerable offsets from the Galactic plane. Future surveys in the VHE gamma-ray range are necessary to probe the presence or absence of such a source population.(abridged)Comment: accepted for publication in A&A, 7 pages, 3 figure

    Rezension: Mary Daly: Gender Inequality and Welfare States in Europe

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    Das bisschen Haushalt

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    „Das bisschen Haushalt“: Wer in Paarbeziehungen welche Routine-Hausarbeiten ĂŒbernimmt, ist nach wie vor eine Frage des Geschlechts. Die Studie setzt sich mit innerhĂ€uslichen Arbeitsteilungsarrangements in Paarbeziehungen im Zusammenhang mit dem von Studien der Familiensoziologie mittlerweile vernachlĂ€ssigten Machtaspekt auseinander. Um die KontinuitĂ€t der traditionellen Arbeitsteilung in europĂ€ischen Regionen erklĂ€ren zu können, wird eine theoretische Macht-Typologie entwickelt, die empirisch anhand einer Mehrebenenanalyse ĂŒberprĂŒft wird.; Who does the dishes and cleans the bathroom? In couple relationships it is still a question of gender who does the majority of housework. The study deals with domestic work arrangements in couple relationships in connection with the aspect of power, which has been neglected by studies of family sociology. In order to explain the continuity of the traditional division of labour in European regions, a theoretical typology of power is developed

    GAMMA-RAY OBSERVATIONS OF GAMMA-RAY BINARIES

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