tokens: equally. The fitting method is the same as the SED analysis. The results are shown in Figure 4 . The arrows indicate the 95% upper limits of those time bins, whose TS values are smaller than 5. No obvious long term variation is found, which is consistent with the emission expected from an SNR. Figure 4. Light curve of source X. The horizontal solid and dashed lines are the average flux and its 1 σ range from the whole data set. 3. DISCUSSION The spatial and spectral association between source X and the HESS observation of SNR CTB 37B suggests that source X is the GeV counterpart of this SNR. The γ -ray emission can be either from the ICS of high energy electrons or the π 0 decay due to the inelastic pp collisions. Due to the lack of non-thermal X-ray emission in the same region of the TeV γ -ray emission, Aharonian et al. ( 2008 ) argued that the TeV γ -rays may have a hadronic origin. The Suzaku observations reveal, however, both thermal and non-thermal diffuse X-ray emissions from the western part of the radio shell, which suggests alternatively a multi-zone leptonic scenario for the γ -ray emission (Nakamura et al. 2009 ). We discuss both the leptonic and hadronic models in light of the multi-wavelength data, including the Fermi -LAT ones. In the modeling, both the spectra of electrons and protons are assumed to be power laws with exponential cutoffs, , where i = e or p , and α i and are the spectral index and the cutoff energy, respectively. The distance of CTB 37B is adopted to be 13.2 kpc (Tian Leahy 2012 ), and the radius is taken to be r ≈ 20 pc which corresponds to an angular size of 51 at such a distance. The radiation field includes the cosmic microwave background (CMB), an infrared field with T = 30 K and energy density u = 1 eV cm −3 , and an optical field with T = 6000 K and u = 1 eV cm −3 (Porter et al. 2006 ). The gas density is adopted to be 0.5 hydrogen cm −3 , as inferred from the X-ray observations (Aharonian et al. 2008 ; Nakamura et al. 2009 ). For the region which is coincident with the SNR shell (region 1), no non-thermal emission has been detected (Aharonian et al. 2008 ; Nakamura et al. 2009 ). The 1–5 keV flux of the thermal emission is ∼3 × 10 −13 erg cm −2 s −1 (Aharonian et al. 2008 ). The 2–10 keV unabsorbed flux of the thermal X-ray emission from region 1 is estimated to be ∼6 × 10 −13 erg cm −2 s −1 , based on the non-equilibrium ionization model employed in Aharonian et al. ( 2008 ). This thermal flux is adopted as an upper limit of the non-thermal emission from the SNR. 3.1. Leptonic Model In the leptonic model, the radio to X-ray emission is due to synchrotron radiation of relativistic electrons in the magnetic field, and the γ -ray emission is produced through ICS in the background radiation field and bremsstrahlung in the interstellar medium. To fit the radio to TeV γ -ray data, we find α e ≈ 1.65, , a magnetic field B ≈ 100 μ G, and a total electron energy above 1 GeV W e ≈ 9.0 × 10 48 erg. The fitting
ner_tags: O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Telescope O O B-CelestialObject I-CelestialObject I-CelestialObject O O O O O O B-Wavelength O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength O O O O O O O B-Wavelength I-Wavelength I-Wavelength O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O B-Wavelength I-Wavelength I-Wavelength O O O O O O B-Telescope O O O O O O O O B-Wavelength O O O O O O O B-Wavelength O O O O O O O O O O B-Wavelength I-Wavelength O B-Citation I-Citation I-Citation I-Citation O O O O O B-Model O B-Model I-Model O O O O O O O O B-Observatory B-Telescope O O O O O O O O O O O O O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O B-Citation I-Citation I-Citation O O O O O O O O B-Formula I-Formula I-Formula I-Formula O O O O O O O O O O O O O O O O O O B-Wavelength O B-Wavelength O O O O B-Formula I-Formula I-Formula I-Formula O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O O O O O B-Formula I-Formula I-Formula I-Formula O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O B-Wavelength O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O B-Citation I-Citation I-Citation I-Citation O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation O O B-Wavelength I-Wavelength O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O B-Citation I-Citation I-Citation I-Citation I-Citation I-Citation O O O O O O O O O O O O O O O O O B-Model I-Model O O B-Model I-Model O B-Wavelength O B-Wavelength O O O O O O O O O O O O O O O B-Wavelength I-Wavelength O O O O O O O O O O O O O O O O O O O B-Wavelength O B-Wavelength I-Wavelength I-Wavelength O O O B-Formula I-Formula I-Formula I-Formula B-TextGarbage O O O B-Formula I-Formula I-Formula I-Formula I-Formula O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O