Merged Red-Giant Stars

红巨星是最大、最亮的恒星，产生许多常见的化学元素，如碳和氮。由于它们的体积很大，而且大多数恒星都是在双星系统中，所以很可能会与伴星相互作用。这一过程经过了共同包络演化，形成了奇异的双星现象，如热核新星、超新星、中子星和黑洞双星，它们合并在一起，产生了最近探测到的引力波。不幸的是，在所有恒星演化阶段中，共包层演化是最不确定的。对幸存恒星的速率和特性的定量预测是出了名的不可靠。这个项目将扭转这个问题。许多双星系统无法在共同包络演化中幸存下来：相反，它们合并成单个的、奇特的巨星，即“红离散星”。这些巨行星的详细模型将被建立起来，以预测恒星的结构、旋转和化学性质，然后与最新的观测结果进行比较，以了解神秘但非常重要的共同包络物。

Red giants are the biggest and brightest stars, and make many common chemical elements, like carbon and nitrogen.Because of their great size, and because most stars are in binary systems, interaction with a companion star is very likely.This proceeds through common-envelope evolution and forms exotic binary phenomena like thermonuclear novae, type-Iasupernovae and neutron-star and black-hole binaries which merge to make the recently-detected gravitational waves.Unfortunately, common-envelope evolution is the most uncertain of all stellar-evolution phases. Quantitative predictions ofrates and properties of stars that survive it are notoriously unreliable. This project will reverse the problem. Many binarysystems do not survive common-envelope evolution: instead they merge to form single, peculiar giants, the ?redstragglers?. Detailed models of these giants will be constructed to predict stellar-structure, rotation and chemistry, andthen be compared to the latest observations to understand the mysterious, but hugely important, common-envelopemergers.