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/
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
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
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/
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/
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/
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
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/
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.
One application was received and successful for a 2023 Research Grant. The project is Photometry of variable stars brighter than ~6th magnitude utilising neutral density filters to mitigate scintillation noise caused by short exposure times by Mark Blackford
In 2022 the Astronomical Association of Queensland (AAQ) called for applications for a grant from the Edward Corbould Research Fund (ECRF). The grant was to fund astronomical research by Australian amateur astronomers commencing in 2023.
From October 2022 applications for funding up to the value of $5,000 were invited, to be received by the AAQ General Secretary no later than 28 February 2023. Projects requiring in excess of this amount could be considered under special circumstances.
The ECRF has been established to encourage and assist astronomical research. Projects in any field of astronomy are considered. Projects would normally comprise observational research which has defined objectives and timeline, adds to the body of astronomy or space knowledge, and is appropriate for publication. Funds may be requested to support any aspect of the research including appropriate equipment (excluding office equipment and items which form an inherent part of a larger whole such as a telescope mirror), consumable items or essential travel but excluding personal remuneration. Applications for funding solely for travel to conferences or for planning research will not be considered.
If you have a astronomical research project in mind, we would like to hear from you. Yes, grants for 2023 have closed, but you can prepare for the next time we offer a grant!
If applying for grants or writing proposals would put you off, please approach us anyway. We have experienced amateur researchers who are quite happy to guide you through a proposal, get you started in your research and help you reporting on, or writing up, your project’s outcomes.
The application is in the form of a research proposal and includes the following:
A statement of the aims of the project.
Details of the proposed methodology including analysis of the data to be collected.
A timeline for the project.
An itemised list of proposed expenditure. Where appropriate you would rank items in terms of priority: 1 – those essential for the project; 2 – those considered necessary to maintain a reasonable rate of progress to bring the project to completion; 3 – other items which would be useful in supporting the project.
A short CV of the applicant including relevant astronomical experience.
A letter of support for the project from a scientist/renowned amateur working in the field covered by the proposal.
A review of any relevant scientific literature, supported by a list of references.
Applicants are expected to use the ECRF Application form 2023 for making an ECRF Grant submission. There is a PDF version and a Microsoft Word version.
The signed copy of the application is required to be sent by post or scanned and lodged via email to the General Secretary of the AAQ at the address below.
Sufficient biographical and project information has to be provided to allow the Research Committee to determine if the recipient is capable of achieving the project’s aims and the project is scientifically worthwhile. Applicants requesting more than one item of equipment or consumables should provide a list of priorities showing which items are essential and which could be left to a subsequent year.
Applications are reviewed by the AAQ Research Committee which makes recommendations to the AAQ Council. If, in the Research Committee’s opinion, no worthy project is proposed in any year then no funds will be granted for that year.
Applicants must be Australian citizens. Successful applicants who are not members of the AAQ are required to join the AAQ before funds can be disbursed and must remain members during the period of the grant. The current membership fees are published in our Membership Pack. Successful applicants who are not already AAQ members will be advised in time so that they may make membership applications to be received by the General Secretary prior to 1st June for subsequent election to membership at the June 2023 Council Meeting.
Successful applicants must submit annual project progress reports to the General Secretary to be printed in the AAQ Annual Proceedings over the life of the project up to a maximum of 7 years. They must also provide evidence to the General Secretary of the expenditure of the grant in the form of receipts, photographs etc.
Equipment purchased under the ECRF grant remains the property of the AAQ. If the project is of limited duration the equipment is to be either returned to the AAQ or the applicant may purchase the equipment from the AAQ at its depreciated value. Equipment is depreciated at a rate of 20% per annum after the first twelve months with the equipment written off after a 7 year period. Where the equipment is lost, stolen or damaged during the grant recipient’s custodianship, the recipient must tell the Council as soon as possible. The Council reserves the right to ask the recipient to make a contribution to the repair or replacement of the items.
Contact the General Secretary for further details or enquiries.
Email:
Post:
The General Secretary,
Astronomical Association of Queensland,
PO Box 6101,
St Lucia QLD. 4067.
