Fermi Gamma-ray Space Telescope

On the origin of the gamma-ray emission toward SNR CTB 37A with Fermi-LAT

Soheila Abdollahi
(Jean Ballet, Tsunefumi Mizuno, Yasushi Fukazawa, Hideaki Katagiri on behalf of the Fermi-LAT collaboration)


Supernova remnants (SNRs) are believed to be one of the major sources of Galactic cosmic rays (CRs) up to ∼10^15 eV. Middle-aged SNR CTB 37A, located in a very complex region, is known to interact with several adjacent dense molecular clouds through detection of shocked H2 and OH 1720 MHz maser emission. An excellent correspondence between radio and infrared emission reveals that CTB 37A is in the radiative stage of evolution at least in the northern and eastern rims of the remnant. The TeV γ-ray source HESS J1714−385 and the X-ray source CXOU J171419.8−383023 are both offset to the west from the geometric center of the remnant and are embedded within the extended radio shell, though it is still not clear whether the TeV γ-ray emission originates in the SNR or in a plausible pulsar wind nebula (PWN). In the present work, we use eight years of Fermi-LAT Pass 8 data to perform detailed morphological and spectral studies of the γ-ray emission. Based on the spatial and spectral characteristics of the SNR, we discuss the possibility of a composite nature for CTB 37A to explain the broadband spectrum and to constrain the physical parameters of the SNR, which helps us to elucidate the nature of the γ-ray emission toward the CTB 37A system.