Stellar Death as a Window to Peep into Beyond the Standard Model Physics

Stellar deaths — from the collapse of the first stars to 
core-collapse supernovae — serve as powerful cosmic laboratories to 
probe physics beyond the Standard Model (BSM). We present two 
complementary studies exploiting this connection. First, we propose a 
mechanism in which non-annihilating dark matter (DM) with spin-dependent 
interactions accumulates inside Population III stars, driving their 
premature collapse into black hole seeds. These early seeds accrete over 
longer periods and naturally explain the supermassive black holes 
observed at high redshifts (z > 5) by JWST, reproducing their mass 
function and SMBH–stellar mass relation. Portions of the viable 
parameter space are testable by forthcoming direct detection 
experiments, and the scenario predicts distinctive gravitational wave 
signatures accessible to LISA and pulsar timing arrays. Second, we 
develop a comprehensive framework to compute the diffuse gamma-ray flux 
from axions produced in core-collapse supernovae and converting into 
photons across all relevant magnetic field environments — progenitor, 
host galaxy, intergalactic medium, and the Milky Way — for the first 
time treated consistently together with an updated cosmic star formation 
rate. Using COMPTEL, EGRET, and Fermi-LAT data, we derive competitive 
constraints on the axion-photon coupling over a wide range of axion 
masses, and forecast sensitivity of upcoming MeV gamma-ray telescopes 
via Fisher analysis. This talk is based on our recent works - 
arXiv:2512.23789, arXiv:2604.01277.