I was trying to find the meaning of passive gamma-ray emission through the internet. I haven't found any helpful article except some research paper just denoting the word passive ray emission. They also didn't define the meaning. When I searched for the picture it showed a graph with the number of counts vs energy that didn't dictate any information why it was passive. And what were the criteria for being an active gamma-ray emission? so it would be helpful if someone can explain it. Thank you!!!
