A mass of less than 15 solar masses for the black hole in an ultraluminous X-ray source

Most ultraluminous X-ray sources have a typical set of properties not seen in Galactic stellar-mass black holes. They have luminosities of more than 3 × 10 39 ergs per second, unusually soft X-ray components (with a typical temperature of less than about 0.3 kiloelectronvolts) and a characteristic downturn in their spectra above about 5 kiloelectronvolts. Such puzzling properties have been interpreted either as evidence of intermediate-mass black holes or as emission from stellar-mass black holes accreting above their Eddington limit, analogous to some Galactic black holes at peak luminosity. Recently, a very soft X-ray spectrum was observed in a rare and transient stellar-mass black hole. Here we report that the X-ray source P13 in the galaxy NGC 7793 is in a binary system with a period of about 64 days and exhibits all three canonical properties of ultraluminous sources. By modelling the strong optical and ultraviolet modulations arising from X-ray heating of the B9Ia donor star, we constrain the black hole mass to be less than 15 solar masses. Our results demonstrate that in P13, soft thermal emission and spectral curvature are indeed signatures of supercritical accretion. By analogy, ultraluminous X-ray sources with similar X-ray spectra and luminosities of up to a few times 10 40 ergs per second can be explained by supercritical accretion onto massive stellar-mass black holes

Cancer related fatigue: implementing guidelines for optimal management

BACKGROUND: Cancer-related fatigue (CRF) is a key concern for people living with cancer and can impair physical functioning and activities of daily living. Evidence-based guidelines for CRF are available, yet inconsistently implemented globally. This study aimed to identify barriers and enablers to applying a cancer fatigue guideline and to derive implementation strategies. METHODS: A mixed-method study explored the feasibility of implementing the CRF guideline developed by the Canadian Association for Psychosocial Oncology (CAPO). Health professionals, managers and consumers from different practice settings participated in a modified Delphi study with two survey rounds. A reference group informed the design of the study including the surveys. The first round focused on guideline characteristics, compatibility with current practice and experience, and behaviour change. The second survey built upon and triangulated the first round. RESULTS: Forty-five health practitioners and managers, and 68 cancer survivors completed the surveys. More than 75% of participants endorsed the CAPO cancer related fatigue guidelines. Some respondents perceived a lack of resources for accessible and expert fatigue management services. Further barriers to guideline implementation included complexity, limited practical details for some elements, and lack of clinical tools such as assessment tools or patient education materials. Recommendations to enhance guideline applicability centred around four main themes: (1) balancing the level of detail in the CAPO guideline with ease of use, (2) defining roles of different professional disciplines in CRF management, (3) how best to integrate CRF management into policy and practice, (4) how best to ensure a consumer-focused approach to CRF management. CONCLUSIONS: Translating current knowledge on optimal management of CRF into clinical practice can be enhanced by the adoption of valid guidelines. This study indicates that it is feasible to adopt the CAPO guidelines. Clinical application may be further enhanced with guideline adaptation, professional education and integration with existing practices