Physics & Astronomy Faculty Publications
Document Type
Article
Publication Date
4-1-2026
Abstract
Using Hubble Space Telescope (HST) imaging, we searched for candidate magnetically active binary (AB) counterparts to low-luminosity Chandra X-ray sources in the globular cluster 47 Tucanae (NGC 104). We consider the catalog of 300 Chandra sources within the half-light radius of 47 Tuc compiled by C. O. Heinke et al. (2005). The 10-band HST imaging used to identify these sources spans the range from 275–658 nm. We generated a cross-matched catalog of objects detected by photometric reductions. We used this catalog to search for counterparts within Chandra source error circles using color–magnitude diagrams and a color–color plot. We found 88 likely ABs that lie primarily in the binary sequence region above the main sequence, 10 possible ABs within this region, 12 sub-subgiants, three subgiants, six blue stragglers, and two yellow stragglers. Of these 121 proposed counterparts, 67 are newly identified. One of the ABs appears to be a pre-cataclysmic variable. Our analysis of the spatial distribution of these proposed counterparts indicates that they are significantly more centrally concentrated than the main-sequence turnoff stars. The inferred characteristic mass for these objects is 1.3 ± 0.1 M⊙. A comparison of the numbers of X-ray detected ABs above LX = 1030 erg s−1 in four globular clusters indicates that their relative numbers can be approximately predicted by the mass and binary fractions of each cluster, suggesting that ABs are a primordial population.
Recommended Citation
Cohn, Haldan N., Phyllis M. Lugger, Craig O. Heinke, Maureen Van Den Berg, Liliana Rivera Sandoval, and Jay Anderson. "A Search for Magnetically Active Binary Counterparts to Chandra X-Ray Sources in 47 Tucanae with HST Imaging." The Astrophysical Journal 1000, no. 2 (2026): 214. https://doi.org/10.3847/1538-4357/ae4506
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Publication Title
The Astrophysical Journal
DOI
10.3847/1538-4357/ae4506
Comments
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