Science Highlights - An ALMA Detection of the Radioactive Molecule 26AlF in a Stellar Merger Remnant.

Although diffuse Galactic gamma-ray emission from the isotope of aluminum, ²⁶Al, was first detected in the 1980s, the identification of the source of emission has been hard to pinpoint due to the poor spatial resolution of gamma-ray observations. In a recent Nature paper, a team led by Dr. Kaminski has made use of sensitive, high-resolution observations with Band 6 and the newly commissioned Band 5 on ALMA, as well as observations with NOEMA, to detect millimeter-wave emission from an isotopologue of aluminum monofluoride (²⁶AlF) towards the stellar merger remnant CK Vul (aka Nova 1670; see Figure). These observations have provided information about the nature of one of the stars in the merger. I.e., in the case of CK Vul, the ²⁶Al is likely produced within a star with an initial stellar mass in the range of 0.8-2.5 M_sun that has already formed a condensed degenerate core. During the merger, the ²⁶Al from the outer layers of the helium core are ejected. The authors propose that, unless there is significant amounts of ²⁶Al in atomic phase, in molecules other than ²⁶AlF, and in solids, there is unlikely to be a sufficient number of CK Vul-like merger events to account for the amount of Galactic gamma ray emission from ²⁶Al.