THE CONNECTION OF CARBON BURNING INSIDE WHITE DWARF ACCRETING HELIUM AND ACCRETION-INDUCED COLLAPSE SCENARIO

• Main Author: Galih Prawiradilaga, Muhammad
• Format: Theses
• Language: Indonesia
• Subjects: Astronomi
• Online Access: https://digilib.itb.ac.id/gdl/view/79926
• Institution: Institut Teknologi Bandung

Carbon-oxygen white dwarf (CO WD) and helium star can become one of the combinations that can lead to accretion-induced collapse (AIC). During the evolution, if the rate of accretion exceeds the critical value (2.5 × 10?6 M?/year), carbon burning off-center (CBC) will occur and creates a flame that propagates to the center of the CO WD. This flame alter the CO WD into ONe (oxygen-neon) or OSi (oxygen-silicon) WD. However, the propagation might be disturbed if convective boundary mixing (CBM) is activated during the calculation. This research uses MESA to analyze the long-term evolution of CO WD accreting helium with initial mass of 0.7, 0.8, and 0.9 M?. The accretion rate is set to be constant value at 4 × 10?6 M?/year. The results show that the luminosity of three models are tended to be constant from the beginning until the end of CBC. The CBC began beneath the surface of the WD and stopped at the coordinate mass of around 1.1 M? for three models. The flame is quenched because the activation of overshoot that can interfere the propagation of flame. Nuclear reaction from CBC increases the number of elements 20Ne, 24Mg, and 28Si along the path of the flame. The final result is CO WD covered by ONe. If accretion continues, it is predicted that the CO WD will undergo Type Ia Supernova (SN Ia) when its mass is getting closer to Chandrasekhar Mass (MCh). Nevertheless, WD model without overshoot shows that the flame will propagate to center even though the computation is not fully followed. The CO elements will transform into ONe and lead to the AIC if accretion is still going.