How a Supernova Shoots Out a Lone Spinning Star ⚡ экспресс
Single Be stars, rapidly rotating and typically linked to binary origins, are difficult to explain within standard models. A new formation channel has been proposed: the Be star is an ejected companion after the thermonuclear explosion of a Type Ia supernova. The mechanism is based on the convective Urca process, which triggers explosive oxygen burning in helium stars with masses near the Chandrasekhar limit. Binary evolution modeling showed that about 0.4% of 'helium star + main-sequence star' systems can end up as a single Be star: accretion of material spins up the companion star, after which the helium star explodes. A parameter range where this scenario plays out has been identified. About 22% of such Be stars have peculiar tangential velocities above 24 km/s, classifying them as runaway stars. Thus, the Type Ia supernova channel makes a significant contribution to the population of single Be stars, especially among runaways.
Be stars are rapidly rotating luminaries with bright gas disks. Usually, a companion star spins them up: mass flowing from the neighbor whirls the star like a bullet in a rifled barrel. But there are also lone Be stars without a partner—their origin long remained a mystery.
New research shows that solitaries can be born from a supernova explosion. In a binary system, a massive helium star "feeds" its neighbor hydrogen fuel, spinning it up. Upon reaching the Chandrasekhar limit (about 1.4 solar masses), the helium star detonates as a type Ia supernova. The blast acts like a gunpowder charge and launches the already-spun-up star into free flight—exactly like a bullet from a barrel.
Such runaway stars carry the "memory" of the explosion: their high speed betrays a turbulent past. Astronomers can track them down by measuring the motion of helium witnesses to bygone cataclysms.
🎯 The 'e' in Be stars stands for 'emission'—radiation. It occurs because rapid rotation tears gas from the star's equator, forming a bright disk.