Disc accreting neutron stars come in two distinct varieties, atolls and Z sources, named after their differently shaped tracks on a colour-colour diagram as the source luminosity changes. Here we present analysis of three transient atoll sources showing that there is an additional branch in the colour-colour diagram of atoll sources which appears at very… (More)
Figure 3. Bolometric luminosity (absorption corrected) as a function of S, i.e. distance along the Z track. The luminosities are linearly scaled so that they match at the S = 1 point. The evolution of luminosity as a function of S is remarkably similar for all 3 sources.