A possible association of the new VHE γ-ray source HESS J1825-137 with the pulsar wind nebula G18.0-0.7
Raux, J.; Ripken, J.; Funk, S.; Lemoine-Goumard, M.; Reimer, A.; Reimer, O.; Venter, C.; Schlickeiser, R.; Giebels, B.; Fontaine, G.; Benbow, W.; Hauser, M.; Boisson, C.; Gillessen, S.; Akhperjanian, A. G.; Bazer-Bachi, A. R.; Beilicke, M.; Berge, D.; Bernlöhr, K.; Bolz, O.; Braun, I.; Breitling, F.; Brown, A. M.; Chadwick, P. M.; Chounet, L. -M.; Cornils, R.; Costamante, L.; Degrange, B.; Djannati-Ataï, A.; O'C. Drury, L.; Dubus, G.; Emmanoulopoulos, D.; Espigat, P.; Feinstein, F.; Fuchs, Y.; Gallant, Y. A.; Glicenstein, J. F.; Goret, P.; Hadjichristidis, C.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hofmann, W.; Holleran, M.; Horns, D.; de Jager, O. C.; Khélifi, B.; Komin, Nu.; Konopelko, A.; Latham, I. J.; Le Gallou, R.; Lemière, A.; Leroy, N.; Martineau-Huynh, O.; Lohse, T.; Marcowith, A.; Masterson, C.; McComb, T. J. L.; de Naurois, M.; Nolan, S. J.; Noutsos, A.; Orford, K. J.; Osborne, J. L.; Ouchrif, M.; Panter, M.; Pelletier, G.; Pita, S.; Pühlhofer, G.; Punch, M.; Raubenheimer, B. C.; Raue, M.; Rayner, S. M.; Rob, L.; Rolland, L.; Rowell, G.; Sahakian, V.; Saugé, L.; Schlenker, S.; Schuster, C.; Schwanke, U.; Siewert, M.; Sol, H.; Steenkamp, R.; Stegmann, C.; Tavernet, J. -P.; Terrier, R.; Théoret, C. G.; Tluczykont, M.; Vasileiadis, G.; Vincent, P.; Völk, H. J.; Wagner, S. J.; Borrel, V.; Dickinson, H. J.; Jacholkowska, A.; Aharonian, F. A.; Martin, J. M.; Spangler, D.
Germany, Armenia, France, United Kingdom, Ireland, South Africa, Czech Republic, Namibia
Abstract
We report on a possible association of the recently discovered very high-energy γ-ray source HESS J1825-137 with the pulsar wind nebula (commonly referred to as G 18.0 0.7) of the 2.1× 104 year old Vela-like pulsar PSR B1823 13. HESS J1825-137 was detected with a significance of 8.1σ in the Galactic Plane survey conducted with the HESS instrument in 2004. The centroid position of HESS J1825-137 is offset by 11´ south of the pulsar position. XMM-Newton observations have revealed X-ray synchrotron emission of an asymmetric pulsar wind nebula extending to the south of the pulsar. We argue that the observed morphology and TeV spectral index suggest that HESS J1825-137 and G18.0-0.7 may be associated: the lifetime of TeV emitting electrons is expected to be longer compared to the XMM-Newton X-ray emitting electrons, resulting in electrons from earlier epochs (when the spin-down power was larger) contributing to the present TeV flux. These electrons are expected to be synchrotron cooled, which explains the observed photon index of ~2.4, and the longer lifetime of TeV emitting electrons naturally explains why the TeV nebula is larger than the X-ray size. Finally, supernova remnant expansion into an inhomogeneous medium is expected to create reverse shocks interacting at different times with the pulsar wind nebula, resulting in the offset X-ray and TeV γ-ray morphology.