2024/12/17 by S. K. Jeena, Jeena, S. K., Projjwal Banerjee +1
Physics and Astronomy · #Astronomy and Astrophysical Research #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2412.13078
Among very metal-poor (VMP) stars, α-poor VMP (αPVMP) stars that have sub-solar values of \rm [X/Fe] for Mg and other α elements are rare and are thought to have been formed from gas polluted by Type 1a supernova (SN 1a). However, recent analyses indicate that pure core-collapse supernova (CCSN) ejecta can also be a likely source. We perform a detailed analysis of 17 αPVMP stars by considering six different scenarios relevant to the early Galaxy. We consider a single pair-instability supernova (PISN) and a single CCSN. Additionally, we consider the combination of ejecta from a CCSN with ejecta from another CCSN, a PISN, a near-Chandrasekhar mass (near-\rm MCh) SN 1a, and a sub-Chandrasekhar mass (sub-\rm MCh) SN 1a. A clear signature can only be established for sub-\rm MCh SN 1a with a near-smoking-gun signature in SDSSJ0018-0939 and a reasonably clear signature in ET0381. The majority (82%) of αPVMP stars can be explained by pure CCSN ejecta and do not require any SN 1a contribution. However, the combination of CCSN and sub-\rm MCh SN 1a ejecta can also explain most (76%) of αPVMP stars. In contrast, the combination of ejecta from CCSN with near-\rm MCh SN 1a and PISN can fit 41% and 29% of the stars, respectively. The single PISN scenario is strongly ruled out for all stars. Our results indicate that αPVMP stars are equally compatible with pure CCSN ejecta and a combination of CCSN and SN 1a ejecta, with sub-\rm MCh SN 1a being roughly twice as frequent as near-\rm MCh SN 1a.