The Effects of Rotation, Metallicity, and Magnetic Field on the Islands of Failed Supernovae

Abstract

Failed supernovae (FSN) are a possible channel for the formation of heavy stellar-mass black holes ( M _BH > ∼30 M _⊙ ). However, the effects of metallicity, rotation, and magnetic field on the islands of explodabilty of massive stars are not clear. Here, we simulate the stellar structure and evolution in the mass range between 6 and 55 M _⊙ with different initial rotational velocities, metallicities, and magnetic fields from zero-age main sequence (ZAMS) to pre-collapse. We find that the rapid rotating stars can remain lower ^12 C mass fraction at the time of C ignition, which allows the transition, from convective carbon burning to radiative burning, to occur at lower M _ZAMS than those from stars without rotation. However, the rapid rotation is unfavorable for FSN occurring but is conducive to long gamma-ray bursts (lGRBs) because it results in the specific angular momentum in the CO core being greater than the last stable orbit at core collapse. The increasing metallicity does not affect FSN islands, but high metallicity inhibits rotational mixing and is unfavorable for producing lGRBs. A magnetic field can constrain the mass-loss rate even for rapid rotating stars, resulting in higher mass at pre-collapse. The magnetic braking triggered by the magnetic field can reduce the rotation velocity for high-metallicity models, which decreases the specific angular momentum in the CO core and is favorable for FSN occurring. We suggest that the heavy-mass black holes detected by LIGO may originate from rapidly rotating massive stars with strong magnetic fields, rather than those with very low metallicity.

Keywords

• Stellar evolution
• Stellar rotation
• Massive stars
• Magnetic fields