tokens: multiwavelength emission region. In fact, the X-ray and radio observations have also revealed that the morphology of the central PWN is shaped by reverse shock interactions inside the SNR (Temim et al. 2009 , 2015 ; Ma et al. 2016 ), as reverse shocks inside SNRs can accelerate electrons to high enough energies to produce gamma-ray emission. However, the pulsed emission of the central putative pulsar has not been detected from the radio to high-energy γ -ray bands so far. Compared with other composite SNRs, COMP G327.1-1.1 is an excellent source to explore the interaction between its host and inside PWN in combination with the multiwavelength observations from radio to γ -ray (Acero et al. 2013 ). In previous works (Acero et al. 2013 , 2016 ), the GeV γ -ray emission from the source had not been detected by the Fermi-LAT. In this paper, we search for the potential GeV emission from COMP G327.1-1.1 with Fermi-LAT to better understand its nature of emission in the high-energy band. The paper is organized as follows. The routines of data analysis are given in Section 2 , and the related results are presented in Section 3 . The likely origin of the GeV radiation is discussed in Section 4 , and we conclude in Section 5 . 2. Data Reduction The analysis was performed using the Fermi Science Tools version v11r5p3 . 3 3 http://fermi.gsfc.nasa.gov/ssc/data/analysis/software/ We follow the data analysis method as documented in Fermi Science Support Center. 4 4 http://fermi.gsfc.nasa.gov/ssc/data/analysis/scitools/ The Pass 8 data with “Source” event class (evtype = 3 and evclass = 128) and the instrumental response function “P8R3_SOURCE_V2” were adopted. To minimize the contamination from the Earth limb, we excluded events with the zenith angle > 90°. The time range of the photon events is from 2008 August 4 to 2020 October 24, and the energy range is from 800 MeV to 500 GeV considering a larger point-spread function (PSF) in the lower-energy band. The center of the region of interest (ROI) of 20° × 20° square is at (R.A. = 23863, decl. = −5506). 5 5 http://simbad.u-strasbg.fr/simbad/ We used the Fermi Large Telescope Fourth Source Catalog (4FGL; Abdollahi et al. 2020 ) and the script make4FGLxml.py 6 6 https://fermi.gsfc.nasa.gov/ssc/data/analysis/user/ to generate the source model file, which in total included 737 objects within 30° centered at the center of ROI, and then we added a point source with a power-law spectral model in the position of COMP G327.1+1.1. The fit was performed by using the tool gtlike in the Fermi Science Tools package. 7 7 https://fermi.gsfc.nasa.gov/ssc/data/analysis/scitools/references.html Here, we select to free the normalizations and spectral parameters from all sources within 5°, and the normalizations of the two diffuse backgrounds including iso _ P8R3 _ SOURCE _ V2 _ v1.txt and gll _ iem _ v07.fits . 8 8 http://fermi.gsfc.nasa.gov/ssc/data/access/lat/BackgroundModels.html 3. Results The command gttsmap is used to
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