AstroSat/UVIT Study of NGC 663: first detection of Be+sdOB

systems in a young star cluster

Be stars are rapidly rotating stars surrounded by a disc; however, the origin of these remains unclear. Mass and angular momentum transfer in close binaries account for the rapid rotation of a major fraction of Be stars, supported by the previous detection of low-mass stripped companions to them. The stripped companions can be helium burning subdwarf OB-type stars (sdOBs), and white dwarfs (WDs). In our search for hot companions in a sample of Be stars in NGC 663, we found that  that 19 out of 23 candiates possess a UV excess, which can be unambiguously attiributed to the presence of hot companions. We report the first detection of high-mass sdOB companions to Be stars, with 69.5% of them found in binaries within a cluster, offering direct evidence of binary interactions and their role in shaping the properties of Be stars.

https://ui.adsabs.harvard.edu/abs/2025arXiv250608126N/abstract

Differential reddening in 48 globular clusters: An end to the quest for the intracluster medium

Building on the Stetson photometry for 48 globular clusters (Stetson et al. 2019), we derived accurate differential reddening maps that can be used to correct any photometric catalog in those areas. We used the maps to estimate the amount of intracluster medium within each cluster and we found it to be in agreement with theoretical expectations. In the past, upper limits derived from non-detections of infrared emission were used to claim that the intracluster medium was orders of magnitude less abundant than expected. Our maps support recent discoveries about the spatial distribution which, together with new data on the dust chemical composition, show of the missing intracluster medium problem was indeed a false problem. 

https://ui.adsabs.harvard.edu/abs/2024A%26A...686A.283P/abstract