Fermi-LAT constraints on the Pulsar Wind Nebula nature of HESS J1857+026

Abstract : Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857+026 is a spatially extended gamma-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856+0245. We search for gamma-ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase-fold 36 months of gamma-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete gamma-ray spectral and morphological analysis. No gamma-ray pulsations were detected from PSR J1856+0245. However, significant emission is detected at a position coincident with the TeV source HESS J1857+026. The gamma-ray spectrum is well described by a simple power-law with a spectral index of 1.53 \pm 0.11_{\rm stat} \pm 0.55_{\rm syst}$ and an energy flux of $G(0.1$--100 GeV$)=(2.71 \pm 0.52_{\rm stat} \pm 1.51_{\rm syst}) \times 10^{-11}$ ergs cm$^{-2}$ s$^{-1}$. The $\gamma$-ray luminosity is $L_{PWN}^{\gamma} (0.1$--100 GeV$)=(2.5 \pm 0.5_{stat} \pm 1.5_{syst}) \times 10^{35} (\frac{d}{9 kpc})^2$ ergs s$^{-1}$, assuming a distance of 9 kpc. This implies a $\gamma-$ray efficiency of $\sim$ 5% for $\dot{E}=4.6 \times 10^{36}$ erg $s^{-1}$, in the range expected for pulsar wind nebulae. Detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.
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Contributeur : Nathalie Martin <>
Soumis le : vendredi 5 octobre 2012 - 11:30:10
Dernière modification le : jeudi 1 février 2018 - 01:41:10

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R. Rousseau, M.-H. Grondin, A. Van Etten, M. Lemoine-Goumard, S. Bogdanov, et al.. Fermi-LAT constraints on the Pulsar Wind Nebula nature of HESS J1857+026. Astronomy and Astrophysics - A&A, EDP Sciences, 2012, 544, pp.A3. 〈10.1051/0004-6361/201118685〉. 〈in2p3-00738825〉



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