Department of Astronomy

Prof. Lugger uses the Hubble Space Telescope and the Chandra X-ray Observatory to study X-ray emitting binary stars in globular star clusters. Globular clusters occupy a special place in astrophysics as they provide a local laboratory for studying fundamental issues in stellar dynamics and stellar evolution. These studies have included the optical identification of Chandra X-ray sources in the nearby core-collapsed globular clusters NGC 6397 and NGC 6752 and the non-core-collapsed clusters 47 Tuc and M4. The counterparts that have been found include cataclysmic variables, chromospherically active binaries, and millisecond pulsars. Studies of the spatial distribution of these sources are used to study the effects of dynamical interactions on the production and evolution of these sources and to investigate the dynamical state of the clusters.

A Comprehensive Analysis of X-Ray Sources in Terzan 5 Using Chandra Observations, Kumawat, Gourav; Heinke, Craig O.; Zhao, Jiaqi; Bahramian, Arash; Cohn, Haldan N.; Lugger, Phyllis M. 2025, ApJ, 990, 218.

Searching for exotic object companions in the dense core of NGC 362: A multi-wavelength and multi-epoch photometric analysis, Ettorre, Greta; Dalessandro, emanuele; Pallanca, Cristina; Cadelano, Mario; Kumawat, Gourav; Heinke, Craig O.; Kamann, Sebastian; Libralato, Mattia; Lugger, Phyllis M.; Cohn, Haldan N.; Dreizler, Stefan 2025, A&A,697A, 215. 

Simultaneous Chandra and HST observations of the quiescent neutron star low-mass X-ray binaries in 47 Tucanae, van den Berg, M.; Rivera Sandoval, L.E.; Heinke, C.O.; Cohn, H. N.; Lugger, P. M.; Grindlay, J. E.; Edmonds, P. D.; Anderson, J.; Catuneanu, A. 2024, MNRAS, 531, 1653.

Chandra and HST studies of the X-ray sources in the globular cluster NGC 362, Kumawat, Gourav; Heinke, Craig O.; Cohn, Haldan N.; Lugger, Phyllis M. 2024, MNRAS, 530, 82.

Exploration of faint X-ray and radio sources in the massive globular cluster M14: a UV-bright counterpart to Nova Ophiuchus 1938, Zhao, Yue; D'Antona, Francesca; Milone, Antonino P. and 4 more 2024, MNRAS, 527, 11491

Exotica in the globular cluster M4, studied with Chandra, HST and the VLA, Lugger, Phyllis M., Cohn, Haldan N., Heinke, Craig O., Zhao, Jiaqi, Zhao, Yue, Anderson, Jay 2023, MNRAS, 524, 2088. 

A deep search for faint Chandra X-ray sources, radio sources and optical counterparts in NGC 6752, Cohn, Haldan N., Lugger, Phyllis M., Zhao, Yue, and 6 more 2021, MNRAS, 508, 2823.

A deep Chandra survey for faint X-ray sources in the Galactic globular cluster M30, and Searches of optical and radio counterparts, Zhao, Yue, Heinke, Craig O., Cohn, Haldan N., Lugger, Phyllis M., and 10 more 2020, MNRAS, 499, 3338.

The X-ray emissivity of low-density stellar populations, Heinke, C. O., Ivanov, M. G., Koch, E. W., Andrews, R., Chomiuk, L., Cohn, H. N., Crothers, S. de Boer, T., Ivanova, N., Kong, A. K. H., Leigh, N. W. C., Lugger, P. M., and 8 more 2020, MNRAS, 492, 5684.

Identifications of faint Chandra sources in the globular cluster M3, Zhao, Y., Heinke, C. O., Cohn, H. N., Lugger, P. M., Cool, A. M. 2019, MNRAS, 483, 4560.

View the complete list from the Astrophysics Data System

• A100: The Solar System
• A105: Stars and Galaxies