The difference in hydrogen abundance between two classes of type I X-ray bursts

The hypothesis that the bright type I X-ray bursts differ from faint bursts in that a hydrogen-rich envelope is ejected in the former type and not in the latter is theoretically discussed and experimentally investigated. Color-temperature versus luminosity diagrams of X-ray bursts from MXB 1636-536 and MXB 1608-522 are constructed based on observations from the Tenma satellite and are used to study the hydrogen richness of the surface of the neutron stars resulting from the outbursts. Systematic differences between the bright and faint class diagrams are found which confirm the hypothesis.