Carbon fusion is important to understand the late stages in the evolution of a massive star. Astronomically interesting energy ranges for the 12C+12C reactions have been, however, poorly constrained by experiments. Theoretical studies on stellar evolution have relied on reaction rates that are extrapolated from those measured in higher energies. In this work, we update the carbon fusion reaction rates by fitting the astrophysical S-factor data obtained from direct measurements based on the Fowler, Caughlan, & Zimmerman (1975) formula. We examine the evolution of a 20M⊙ star with the updated 12C+12C reaction rates performing simulations with the MESA (Modules for Experiments for Stellar Astrophysics) code. Between 0.5 and 1 GK, the updated reaction rates are 0.35 to 0.5 times less than the rates suggested by Caughlan & Fowler (1988). The updated rates result in the increase of core temperature by about 7% and of the neutrino cooling by about a factor of three. Moreover, the carbon-burning lifetime is reduced by a factor of 2.7. The updated carbon fusion reaction rates lead to some changes in the details of the stellar evolution model, their impact seems relatively minor compared to other uncertain physical factors like convection, overshooting, rotation, and mass-loss history. The astrophysical S-factor measurements in lower energies have large errors below the Coulomb barrier. More precise measurements in lower energies for the carbon burning would be useful to improve our study and to understand the evolution of a massive star.

Introduction
Estimation of New Reaction Rates
    Extrapolation of S-Factor
Stellar Evolution
Summary and Discussion
Acknowledgments
References
12C+12C Reaction Rates Table

• Gwangeon Seong(Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea)
• Yubin Kim(Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea)
• Kyujin Kwak(Department of Physics, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea)
• Sunghoon Ahn(Center for Exotic Nuclear Studies, Institute for Basic Science, Daejeon 34126, Republic of Korea)
• Chaeyeon Park(Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea, Center for Exotic Nuclear Studies, Institute for Basic Science, Daejeon 34126, Republic of Korea)
• Kevin Insik Hahn(Center for Exotic Nuclear Studies, Institute for Basic Science, Daejeon 34126, Republic of Korea)
• Chunglee Kim(Department of Physics, Ewha Womans University, Seoul 03760, Republic of Korea) Corresponding author