In 2018, Professor David Moriarty was awarded the Berenice and Arthur Page Medal for work on eclipsing binary stars and its application to models of stellar evolution.
David’s work is aimed at obtaining data that can be used to test models of stellar evolution. The evolution of close binaries – generally those with periods less than a few days – is complex. There are differing theoretical models that require a range of binary systems with different ages, spectral types, masses and separation of the components, and for which there are accurate values for masses and other fundamental properties. However, current theory is limited by the lack of close binary observations with properties determined from both spectroscopic and photometric data. David is obtaining photometric data in B, V and I bands for a range of contact, semi-detached and detached eclipsing binaries ranging in period from 0.26 to 5 days and V band magnitude from 9 to 13.
However, high resolution spectra with a large telescope are required to determine radial velocities for stars in that magnitude range. After delivering a seminar to the UQ astrophysics group in 2015, David suggested that analysis of high resolution spectra of eclipsing binaries to derive spectral type and radial velocities to complement his photometric studies would make good student projects. Michael Drinkwater agreed and suggested requesting time on the ANU 2.3m telescope with the Wide Field Spectrograph. David wrote a proposal, with the assistance of Michael Drinkwater and Sarah Sweet, and was awarded observing time in April 2016. Troy Cobb was taken on as an Honours student to work on the project. Since then, David has been granted time on the ANU 2.3m telescope for sessions in February, April, May, June and July 2017. Five undergraduate students have benefited from their involvement in the observations and analysis of the spectral and photometric data.
David’s photometric work also has applications in areas of astronomy other than the study of close eclipsing binary systems. He has been asked by Dr P. Maxted at the University of Keele, Staffordshire, United Kingdom, to contribute photometric observations of EPIC 205148699, a low-mass M star transiting a sun-like star, as part of the Kepler2 mission. Observations have been requested in the I band during eclipses.
David has published 4 papers thus far on his work and are cited below.
He has also written a draft of a paper on ST Centauri, with absolute parameters determined from the combination of photometric and spectral data. The abstract is below.
Photometry, spectroscopy and radial velocities of the chromospherically active, close eclipsing binary ST Centauri.
- J. W. Moriarty, M. J. Drinkwater, A. Mohit, S. M. Sweet, Y. Rist
ST Centauri is a close eclipsing binary pair of F9 stars with some characteristics of RS CVn systems. Photometric observations and analysis between 2013 and 2017, combined with those of earlier studies, show that there has been no change in its period for the past 40 years. Both components are chromospherically active, with episodes of emission in Ca II H and K and H Balmer lines that varied over time scales of minutes on some occasions. The radial velocities, determined with the broadening function, were 133 ± 7, 140 ± 11 and -4 km s-1 for each component and system. The mean masses and radii of 0.36 and 1.29 M⊙ and 2.16 and 2.17 R⊙ for components 1 and 2 respectively, indicate that they have evolved past terminal age on the main sequence. The spectra together with the strength of the Sr I 4077 line relative to Fe I 4046 indicate their spectral type is F9 IV.
Publications associated with this award
- Moriarty, D.J.W. 2013, Discovery of Pulsating Components in the Southern Eclipsing Binary Systems AW Velorum, HM Puppis, and TT Horologii. JAAVSO 41, 182.
- Streamer, M., Byron, J., Moriarty, D.J.W. (and 14 other co-authors) 2015, Revised Light Elements of 78 Southern Eclipsing Binary Systems. JAAVSO 43, 67.
- Moriarty, D.J.W. 2015, Period Analysis, Photometry, and Astrophysical Models of the Eclipsing Binary TW Crucis. JAAVSO 43, 151.
- Moriarty, D.J.W. 2016, Period Analysis, Photometry, and Astrophysical Modelling of the Contact Eclipsing Binary BC Gruis. JAAVSO 44, 10.