Search for gamma-ray emission from the nova-like variable AE Aquarii using the Fermi-LAT Pass 8 data Archive
S.T. Madzime,* P. Meintjes, K.K. Singh, H. van Heerden
*corresponding author
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Pre-published on: December 15, 2020
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Abstract
We present the preliminary results of the search for gamma$-$ray emission from the novalike variable AE Aquarii using the upgraded Fermi$-$LAT Pass 8 data set. A previous study using the Fermi$-$LAT Pass 7 data pipeline showed indications of a low$-$level, but consistent, pulsed emission at a period of 16.54 s, which is the first harmonic of the 33.08 s spin period of the white dwarf. Here we report our findings of a follow$-$up study utilizing the Pass 8 data, which uses an improved galactic diffuse gamma$-$ray emission model as well as more inclusive selection criteria. Thus far no clear detection of any significant gamma$-$ray excess from AE Aqr in the Fermi$-$LAT energy range has been made. However, there are some energy bins with significance just above 2$\sigma$. This significance value is below the Fermi$-$LAT detection limit that signifies a clear 4$-$5 $\sigma$ detection and can only be considered as a 2 $\sigma$ upper$-$limit. The corresponding upper limit of the integrated energy flux above 100 MeV is $F_{\gamma} \sim 4 \times$10$^{-13} \mbox{erg} \, \mbox{cm}^{-2} \, \mbox{s}^{-1}$ which is determined at the 99.995 $\%$ confidence level. However, indications of low$-$level pulsed modulation is found at, or close to, the 33.08 s spin period of the white dwarf in a few two$-$week data sections with higher than average TS values, which is promising for possible future follow$-$up studies with the Cherenkov Telescope Array.
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