STUDYING THE SGR 1806-20/Cl* 1806-20 REGION USING THE FERMI LARGE AREA TELESCOPE

Abstract

The region around SGR 1806-20 and its host stellar cluster Cl * 1806-20 is a potentially important site of particle acceleration. The soft γ-ray repeater and Cl * 1806-20, which also contains several very massive stars including a luminous blue variable hypergiant LBV 1806-20, are capable of depositing a large amount of energy to the surroundings. Using the data taken with the Fermi Large Area Telescope (LAT), we identified an extended LAT source to the southwest of Cl * 1806-20. The centroid of the 1-50 GeV emission is consistent with that of HESS J1808-204 (until now unidentified). The LAT spectrum is best-fit by a broken power law with the break energy =  E 297 15 MeV b . The index above E b is 2.60±0.04 and is consistent with the flux and spectral index above 100 GeV for HESS J1808-204, suggesting an association between the two sources. Meanwhile, the interacting supernova remnant SNR G9.7-0.0 is also a potential contributor to the LAT flux. A tentative flux enhancement at the MeV band during a 45 day interval (2011 January 21-March 7) is also reported. We discuss possible origins of the extended LAT source in the context of both leptonic and hadronic scenarios.

Fermi Large Area Telescope Fourth Source Catalog

“…Four H.E.S.S. sources were found to be extended sources in the Fermi-LAT range as well: HESS J1534−571 (Araya 2017), HESS J1808−204 (Yeung et al 2016), HESS J1809−193, and HESS J1813−178 (Araya 2018b). 4.…”

A search for energy-dependence of the Kes 73/1E 1841-045 morphology in GeV

“…In each band, we performed a likelihood ratio test to quantify the radius and significance of extension, following the scheme adopted by [9] and [5]. We assigned this source a simple power law, and we attempted uniform-disk morphologies of different radii as well as a point-source model on it.…”