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Dr David Moriarty, Roy Axelsen and Mark Blackford were authors on this publication in the Journal of the American Association of Variable Star Observers in 2021.
Abstract
We present 246 times of minima of 77 southern hemisphere eclipsing binary stars acquired in 2020. These observations were acquired and analysed by the authors, who are members of the Southern Eclipsing Binary group of Variable Stars South (VSS) (http://www.variablestarssouth.org), using CCD detectors. For four of the systems we have derived updated light elements and present those as well as O–C values for the VSS minima. This paper is the sixth in a series by Richards et al.
Citation
Tom Richards, Roy A. Axelsen, Mark Blackford, Robert Jenkins and David J. W. Moriarty, 2021
Southern Eclipsing Binary Minima and Light Elements in 2020. Journal of the American Association of Variable Star Observers. 49: 251-256.
Web site: https://app.aavso.org/jaavso/article/3764/
Link to Publication
Dr David Moriarty was an author on this publication in the Journal of Astronomy and Astrophysics in 2022
Abstract
This work presents an extensive analysis of the properties of three southern semi-detached eclipsing binaries hosting a pulsating component, namely HM Pup, V632 Sco, and TT Vel. Systematic multi-filtered photometric observations were obtained using telescopes located in Australia and Chile mostly between 2018 and 2021. These observations were combined with data from the Transiting Exoplanet Survey Satellite (TESS) mission for a detailed analysis of pulsations. Spectral types and radial velocities were determined from spectra obtained with the Australian National University’s 2.3 m telescope and Wide Field Spectrograph. The data are modelled and the absolute parameters of all components are derived. The light curve residuals are further analysed using Fourier transformation techniques for the determination of the pulsation frequencies. Using theoretical models, the most probable modes of the principal oscillations are also identified. Eclipse-timing variation analysis is also carried out for all systems and the most likely mechanisms modulating the orbital period are proposed. The physical properties of these systems are compared with other similar cases and the locations of their components are plotted in the Mass-Radius (M−R) and Hertzsprung-Russell diagrams. Finally, the pulsational properties of the oscillating components are compared with currently known systems of this type within the orbital-pulsation period and log g-pulsation period diagrams. These systems are confirmed as oscillating eclipsing Algol-type systems (oEA stars), as the primary components are pulsating stars of δ Scuti type, with evidence of mass flow from the evolved secondary components present in their Na I D spectra.
Orbital model of HM Pup. Models of several of the binary systems have been prepared with Binary Maker; the Sun is shown as an orange circle to the scale of each binary system. View the model animation here:
Citation
Liakos, A., Moriarty, D.J.W., Blackford, M.G. West, P. Evans, C. M. Moriarty, J.F. and Sweet, S. M. Comprehensive analysis of southern eclipsing systems with pulsating components: The cases of HM Pup, V632 Sco, and TT Vel. 2022 Astronomy and Astrophysics. 663, A137.
Web Site: https://doi.org/10.1051/0004-6361/202243313
Link to Publication
https://www.aanda.org/articles/aa/pdf/2022/07/aa43313-22.pdf
Dr David Moriarty was an author on this publication in the Journal of Astrophysics and Space Science in 2019
Abstract
We have combined photometric and spectroscopic observations of two very close eclipsing binary systems, ST Centauri and V775 Centauri, to determine their evolutionary state from calculations of masses and radii and other properties. Spectral types were determined and radial velocities calculated from spectra obtained with the Australian National University’s 2.3 m telescope and Wide Field Spectrograph. The spectral type of the ST Cen primary component is F8 IV and the secondary is F8 – 8.5 IV. The ST Cen mean masses and radii of 1.40 ± 0.05 M☉ and 1.38 ± 0.10 M☉ and 2.2 ± 0.1 R☉ and 2.13 ± 0.08 R☉ for the primary and secondary components respectively, indicate that they are close to terminal age on the Main Sequence. Although the spectra of V775 Cen appeared to be single lined, the broadening function method enabled us to determine the radial velocities of the faint secondary component as well as those of the primary star. The mean masses and radii of the V775 Cen components are 1.66 ± 0.31 M☉ and 0.72 ± 0.29 M☉ and 1.68 ± 0.11 R☉ and 1.24 ± 0.08 R☉ for components 1 and 2 respectively. Our data show that V775 Cen is a close Algol binary system, with a secondary component that has evolved beyond terminal age Main Sequence, has filled its inner critical equipotential surface and is transferring mass to the primary star. The masses and radii of both components of V775 Cen are smaller than those of other Algol binary systems. Although the primary component of V775 Cen is on the Main Sequence, its spectral type is F0/F1 class IV. Both systems displayed episodes of photospheric and chromospheric activity. This was evident in the Hα lines of ST Cen and the Na I D lines of the components in both systems. Narrow Na I D lines between those of the binary components suggest that circumbinary gas is present.
Orbital models. Models of several of the binary systems have been prepared with Binary Maker; the Sun is shown as an orange circle to the scale of each binary system. View the model animations here:
V775 Cen
ST Cen
Citation
Moriarty, D.J.W., Liakos, A., Drinkwater, M.J. Mohit, A., Sweet, S. M. and West, J. F. 2019. Photometric and spectroscopic monitoring, radial velocities and evolutionary status of the chromospherically active, close eclipsing binaries ST Centauri and V0775 Centauri. Astrophysics and Space Science, 365: 1-17.
Web site: https://link.springer.com/article/10.1007/s10509-019-3709-7
Link to Publication
Dr David Moriarty was the author on this publication in the Journal of the American Association of Variable Star Observers in 2016.
Abstract
BC Gruis is a W UMa-type contact binary system of the W-subtype with the primary minimum 0.1 magnitudes fainter than the secondary minimum. The period is currently 0.3073060 ± 0.0000001 days; it was 7 seconds longer between 1986 and 1991. There were small modulations of 0.001 – 0.002 days in the Observed–Calculated diagram due to asymmetry in the light curves, most likely caused by star spots. An astrophysical model of the system was developed with a mass ratio of 1.2 determined from light curve analysis. The best fit to light curves in B, V and I pass bands in 2014 was given by including 2 large cool star spots on the more massive, cooler component and 1 cool spot on the hotter star. In 2015, the asymmetry in the light curves was different and was modelled best with a hot spot on the more massive component at the neck joining the stars and 1 cool spot on the other component.
The model has been updated with radial velocity data. Models of several of the binary systems have been prepared with Binary Maker; the Sun is shown as an orange circle to the scale of each binary system. View the model animation here:
Citation
Moriarty, D.J.W. 2016.
Period Analysis, Photometry and Astrophysical Modelling of the Contact Eclipsing Binary BC Gruis. Journal of the American Association of Variable Star Observers. 44: 10-17.
Web site: https://app.aavso.org/jaavso/article/3169/
Link to Publication
Dr David Moriarty was the author on this publication in the Journal of the American Association of Variable Star Observers in 2015.
Abstract
TW Crucis is a W-type W UMa contact eclipsing binary that has not been studied in detail since discovery in 1926. During 5 seasons from 2011 to 2015, photometric CCD observations were obtained mostly in the V passband, but also some light curves in B and I passbands. The period was found to be 0.3881444 ± 0.0000006 days, which is not substantially different from the original period of 0.3881358 days. There were slight variations in the period from cycle to cycle and year to year, which are most likely due to asymmetry in the light curves caused by star spots. A preliminary model of the light curves indicates the mass ratio may be about 0.67, inclination 70.8° and fillout factor 0.11. As no spectra are available, the range in B-V and V-I colour indices of 0.82 – 0.87 and 0.87 – 0.92 respectively were used to estimate the effective temperatures for the modelling, based on the spectral types of K0 – K2. The spectral type may be earlier, if the colour indices are affected by interstellar reddening. Star spots, which changed over short period cycles and were required to obtain good fits of the models to the light curves, indicate the stars are magnetically active.
The model has been updated with radial velocity data. Models of several of the binary systems have been prepared with Binary Maker; the Sun is shown as an orange circle to the scale of each binary system. View the model animation here:
Citation
Moriarty, D.J.W. 2015.
Period Analysis, Photometry and Astrophysical Models of the Eclipsing Binary TW Crucis. Journal of the American Association of Variable Star Observers. 43: 151-157.
Web site: https://app.aavso.org/jaavso/article/3115/
Link to Publication
https://app.aavso.org/media/jaavso/3115_WKu2UAT.pdf
Dr David Moriarty was an author on this publication in the Journal of the American Association of Variable Star Observers in 2015
Abstract
Since 2011, members of Variable Stars South have undertaken intensive time series observations and analysis of eclipsing binary systems, most of which are south of declination -40°. Many of them have not been observed in detail since their discovery 50 – 80 years ago. New or revised light elements are presented here for 60 systems and revised O-C values for a further 18 systems. A pulsating component has been discovered in four of the binary systems: RZ Mic, V0632 Sco, V0638 Sco and LT Her.
Citation
M. Streamer, J. Byron, D.J.W. Moriarty and 14 other co-authors. 2015.
Revised Light Elements of 78 Southern Eclipsing Binary Systems. Journal of the American Association of Variable Star Observers. 43: 1-7.
Web site: https://app.aavso.org/jaavso/article/3048/
Link to Publication
Dr David Moriarty was an author on this publication in the Journal of the American Association of Variable Star Observers in 2013
Abstract
Eclipsing binary stars with pulsating components are especially valuable for studies of stellar evolution. We have discovered that three eclipsing binary stars in the southern sky have a pulsating component with oscillations similar to those of δ Scuti stars. The systems are: AW Velorum, HM Puppis and TT Horologii. Their spectral types were determined as A7 for AW Vel and HM Pup and F0-F2 for TT Hor. The dominant pulsation frequencies are 15 – 38 cycles per day with amplitudes of 10 – 60 millimagnitudes.
Citation
Moriarty, D.J.W., Bohlsen, T., Heathcote, B., Richards, T. and Streamer, M. (2013).
Discovery of Pulsating Components in the Southern Eclipsing Binary Systems AW Velorum, HM Puppis and TT Horologii. Journal of the American Association of Variable Star Observers. 41: 182-192.
Web site: https://app.aavso.org/media/jaavso/2930.pdf
Link to Publication
Keith Treschman published this article in the Australian Science Teachers Association Teaching Science Journal in 2022
Abstract
The topic of the seasons is covered in both primary and secondary schools in Australia. It may be difficult for some students to comprehend how the Sun alters its position throughout the year. The following shows how to calculate the changing rising and setting positions of the Sun for one’s locality and the extremes of its elevation near noon over a year. A model to show these changes may be constructed.
Citation
Treschman, Keith. (2022). MODEL OF MOTION OF SUN. Teaching Science, v68 n2 p43-45 Jun 2022.
Australian Science Teachers Association. P.O. Box 334, Deakin West, ACT 2600, Australia. Web site: https://www.asta.edu.au/resources/teaching-science-journal/
Link to Publication
https://www.researchgate.net/publication/361916450_MODEL_OF_MOTION_OF_SUN
Keith Treschman, AJAA, 2021. Even though the longest day occurs on the June solstice everywhere in the Northern Hemisphere, this is NOT the day of earliest sunrise and latest sunset.