Lead 5 postgraduate researchers, covering Asia-Pacific, Middle East, and Africa. Projects include using satellite imagery to determine urban/rural, machine learning techniques to better detect new retail outlet behaviour, location services such as geo-fencing and mapping to improve sampling compliance, statistical process control and automation, optimisation techniques to allow continuous sampling, and use of distribution data for sales force effectiveness. A little bit of astronomical work too
We present an updated ephemeris, and physical parameters, for the exoplanet WASP-77 A b. In this ... more We present an updated ephemeris, and physical parameters, for the exoplanet WASP-77 A b. In this effort, we combine 64 ground- and space-based transit observations, 6 space-based eclipse observations, and 32 radial velocity observations to produce this target’s most precise orbital solution to date aid- ing in the planning of James Webb Space Telescope (JWST) and Ariel observations and atmospheric studies. We report a new orbital period of 1.360029395 ± 5.7 × 10−8 days, a new mid-transit time of 2459957.337860 ± 4.3 × 10−5 BJDTDB (Barycentric Julian Date in the Barycentric Dynamical Time scale; Eastman et al. (2010)) and a new mid-eclipse time of 2459956.658192 ± 6.7 × 10−5 BJDTDB. Furthermore, the methods presented in this study reduce the uncertainties in the planet’s mass 1.6654 ±4.5 × 10−3MJup and orbital period 1.360029395 ± 5.7 × 10−8 days by factors of 15.1 and 10.9, re- spectively. Through a joint fit analysis comparison of transit data taken by space-based and citizen science-led initiatives, our study demonstrates the power of including data collected by citizen scientists compared to a fit of the space-based data alone. Additionally, by including a vast array of citizen science data from ExoClock, Exoplanet Transit Database (ETD), and Exoplanet Watch, we can increase our observational baseline and thus acquire better constraints on the forward propagation of our ephemeris than what is achievable with TESS data alone
This study outlines a detailed investigation using CCD UBV and Gaia DR3 data sets of the two open... more This study outlines a detailed investigation using CCD UBV and Gaia DR3 data sets of the two open clusters Ruprecht 1 (Rup-1) and Ruprecht 171 (Rup-171). Funda- mental astrophysical parameters such as color excesses, photometric metallicities, ages, and isochrone distances were based on UBV-data analyses, whereas member- ship probability calculations, structural and astrophysical parameters, as well as the kinematic analyses were based on Gaia DR3-data. We identified 74 and 596 stars as the most probable cluster members with membership probabilities over 50% for Rup-1 and Rup-171, respectively. The color excesses 𝐸(𝐵 − 𝑉 ) were obtained as 0.166 ± 0.022 and 0.301 ± 0.027 mag for Rup-1 and Rup-171, respectively. Photo- metric metallicity analyses were performed by considering F-G type main-sequence member stars and found to be [Fe/H]=−0.09 ± 0.16 and [Fe/H]=−0.20 ± 0.20 dex for Rup-1 and Rup-171, respectively. Ages and distances were based on both UBV and Gaia-data analyses; according to isochrone-fitting these values were estimated to be 𝑡 = 580±60Myr, 𝑑 = 1469±57 pc for Rup-1 and 𝑡 = 2700±200Myr, 𝑑 = 1509 ± 69 pc for Rup-171. The present-day mass function slope of Rup-1 was estimated as 1.26 ± 0.32 and Rup-171 as 1.53 ± 1.49. Galactic orbit integration anal-yses showed that both of the clusters might be formed outside the solar circle.
A detailed analysis of ground-based CCD UBV photometry and space-based Gaia Data Release 3 (DR3) ... more A detailed analysis of ground-based CCD UBV photometry and space-based Gaia Data Release 3 (DR3) data for the open clusters King 6 and NGC 1605 was performed. Using the pyUPMASK algorithm on Gaia astrometric data to estimate cluster membership probabilities, we have identified 112 stars in King 6 and 160 stars in NGC 1605 as the statistically most likely members of each cluster. We calculated reddening and metallicity separately using UBV two-color diagrams to estimate parameter values via independent methods. The color excess E(B − V) and photometric metallicity [Fe/H] for King 6 are 0.515 ± 0.030 mag and 0.02 ± 0.20 dex, respectively. For NGC 1605, they are 0.840 ± 0.054 mag and 0.01 ± 0.20 dex, respectively. With reddening and metallicity kept constant, we have estimated the distances and cluster ages by fitting PARSEC isochrones to color–magnitude diagrams based on the Gaia and UBV data. The photometric distances are 723 ± 34 pc for King 6 and 3054 ± 243 pc for NGC 1605. The clu...
CCD images of transits by the exoplanet XO-1b over the years 2018 to 2021 are analyzed. The data ... more CCD images of transits by the exoplanet XO-1b over the years 2018 to 2021 are analyzed. The data were collected by a MicroObservatory telescope in Arizona. These are supplemented by analysis of TESS space telescope data along with transits observed by amateur astronomers, leading to an investigation of the mid-transit times and the orbital period of the exoplanet. No evidence is found to support transit timing variations, with a period of 3.9415049 ± 0.0000008 days being sufficient to explain mid-transit times over 2006 to 2021. Using TESS data, the orbital radius is estimated to be some 11.10 ± 0.15 times the radius of the host star, and the planetary radius 0.1300 ± 0.0016 times the stellar radius. A simple transit model is combined with Bayesian sampling to provide estimates for the orbital inclination, radii, and limb darkening, however these estimates are not internally consistent. This is likely due to the application of the "small planet approximation," which neglects a radial gradient in the stellar flux obscured by the planet (due to the limb darkening effect), together with the model not accounting for variation in the stellar flux.
Estimates of orbital parameters were made using a Bayesian optimization technique on astrometric ... more Estimates of orbital parameters were made using a Bayesian optimization technique on astrometric data for 25 visual binary systems catalogued a century ago by the ninth Astronomer Royal, Sir Frank Dyson. An advantage of this method is that it provides reliable, unbiased uncertainty estimates for the optimized parameters. Reasonable agreement is found for the short period (< 100 yr) systems between the current study and Dyson, with superior estimation for the longer systems through the inclusion of an additional century of data. Dynamical masses are presented for the systems through the inclusion of parallax measurements.
We demonstrate optimal curve-fitting procedures to the parametrization of a selection of 25 visua... more We demonstrate optimal curve-fitting procedures to the parametrization of a selection of 25 visual-binary-star orbits from F. W. Dyson's 1 catalogue. We compare our findings with other published results, which reveal uncertainties, real and formal, affecting the parameters. The extent of data coverage for any one system can have a substantial impact on the modelled results, with various orbital solutions sometimes possible for a single system.
We present an updated ephemeris, and physical parameters, for the exoplanet WASP-77 A b. In this ... more We present an updated ephemeris, and physical parameters, for the exoplanet WASP-77 A b. In this effort, we combine 64 ground- and space-based transit observations, 6 space-based eclipse observations, and 32 radial velocity observations to produce this target’s most precise orbital solution to date aid- ing in the planning of James Webb Space Telescope (JWST) and Ariel observations and atmospheric studies. We report a new orbital period of 1.360029395 ± 5.7 × 10−8 days, a new mid-transit time of 2459957.337860 ± 4.3 × 10−5 BJDTDB (Barycentric Julian Date in the Barycentric Dynamical Time scale; Eastman et al. (2010)) and a new mid-eclipse time of 2459956.658192 ± 6.7 × 10−5 BJDTDB. Furthermore, the methods presented in this study reduce the uncertainties in the planet’s mass 1.6654 ±4.5 × 10−3MJup and orbital period 1.360029395 ± 5.7 × 10−8 days by factors of 15.1 and 10.9, re- spectively. Through a joint fit analysis comparison of transit data taken by space-based and citizen science-led initiatives, our study demonstrates the power of including data collected by citizen scientists compared to a fit of the space-based data alone. Additionally, by including a vast array of citizen science data from ExoClock, Exoplanet Transit Database (ETD), and Exoplanet Watch, we can increase our observational baseline and thus acquire better constraints on the forward propagation of our ephemeris than what is achievable with TESS data alone
This study outlines a detailed investigation using CCD UBV and Gaia DR3 data sets of the two open... more This study outlines a detailed investigation using CCD UBV and Gaia DR3 data sets of the two open clusters Ruprecht 1 (Rup-1) and Ruprecht 171 (Rup-171). Funda- mental astrophysical parameters such as color excesses, photometric metallicities, ages, and isochrone distances were based on UBV-data analyses, whereas member- ship probability calculations, structural and astrophysical parameters, as well as the kinematic analyses were based on Gaia DR3-data. We identified 74 and 596 stars as the most probable cluster members with membership probabilities over 50% for Rup-1 and Rup-171, respectively. The color excesses 𝐸(𝐵 − 𝑉 ) were obtained as 0.166 ± 0.022 and 0.301 ± 0.027 mag for Rup-1 and Rup-171, respectively. Photo- metric metallicity analyses were performed by considering F-G type main-sequence member stars and found to be [Fe/H]=−0.09 ± 0.16 and [Fe/H]=−0.20 ± 0.20 dex for Rup-1 and Rup-171, respectively. Ages and distances were based on both UBV and Gaia-data analyses; according to isochrone-fitting these values were estimated to be 𝑡 = 580±60Myr, 𝑑 = 1469±57 pc for Rup-1 and 𝑡 = 2700±200Myr, 𝑑 = 1509 ± 69 pc for Rup-171. The present-day mass function slope of Rup-1 was estimated as 1.26 ± 0.32 and Rup-171 as 1.53 ± 1.49. Galactic orbit integration anal-yses showed that both of the clusters might be formed outside the solar circle.
A detailed analysis of ground-based CCD UBV photometry and space-based Gaia Data Release 3 (DR3) ... more A detailed analysis of ground-based CCD UBV photometry and space-based Gaia Data Release 3 (DR3) data for the open clusters King 6 and NGC 1605 was performed. Using the pyUPMASK algorithm on Gaia astrometric data to estimate cluster membership probabilities, we have identified 112 stars in King 6 and 160 stars in NGC 1605 as the statistically most likely members of each cluster. We calculated reddening and metallicity separately using UBV two-color diagrams to estimate parameter values via independent methods. The color excess E(B − V) and photometric metallicity [Fe/H] for King 6 are 0.515 ± 0.030 mag and 0.02 ± 0.20 dex, respectively. For NGC 1605, they are 0.840 ± 0.054 mag and 0.01 ± 0.20 dex, respectively. With reddening and metallicity kept constant, we have estimated the distances and cluster ages by fitting PARSEC isochrones to color–magnitude diagrams based on the Gaia and UBV data. The photometric distances are 723 ± 34 pc for King 6 and 3054 ± 243 pc for NGC 1605. The clu...
CCD images of transits by the exoplanet XO-1b over the years 2018 to 2021 are analyzed. The data ... more CCD images of transits by the exoplanet XO-1b over the years 2018 to 2021 are analyzed. The data were collected by a MicroObservatory telescope in Arizona. These are supplemented by analysis of TESS space telescope data along with transits observed by amateur astronomers, leading to an investigation of the mid-transit times and the orbital period of the exoplanet. No evidence is found to support transit timing variations, with a period of 3.9415049 ± 0.0000008 days being sufficient to explain mid-transit times over 2006 to 2021. Using TESS data, the orbital radius is estimated to be some 11.10 ± 0.15 times the radius of the host star, and the planetary radius 0.1300 ± 0.0016 times the stellar radius. A simple transit model is combined with Bayesian sampling to provide estimates for the orbital inclination, radii, and limb darkening, however these estimates are not internally consistent. This is likely due to the application of the "small planet approximation," which neglects a radial gradient in the stellar flux obscured by the planet (due to the limb darkening effect), together with the model not accounting for variation in the stellar flux.
Estimates of orbital parameters were made using a Bayesian optimization technique on astrometric ... more Estimates of orbital parameters were made using a Bayesian optimization technique on astrometric data for 25 visual binary systems catalogued a century ago by the ninth Astronomer Royal, Sir Frank Dyson. An advantage of this method is that it provides reliable, unbiased uncertainty estimates for the optimized parameters. Reasonable agreement is found for the short period (< 100 yr) systems between the current study and Dyson, with superior estimation for the longer systems through the inclusion of an additional century of data. Dynamical masses are presented for the systems through the inclusion of parallax measurements.
We demonstrate optimal curve-fitting procedures to the parametrization of a selection of 25 visua... more We demonstrate optimal curve-fitting procedures to the parametrization of a selection of 25 visual-binary-star orbits from F. W. Dyson's 1 catalogue. We compare our findings with other published results, which reveal uncertainties, real and formal, affecting the parameters. The extent of data coverage for any one system can have a substantial impact on the modelled results, with various orbital solutions sometimes possible for a single system.
Estimates of orbital parameters were made using a Bayesian optimization technique on astrometric ... more Estimates of orbital parameters were made using a Bayesian optimization technique on astrometric data for 25 visual binary systems catalogued a century ago by the ninth Astronomer Royal, Sir Frank Dyson. An advantage of this method is that it provides reliable, unbiased uncertainty estimates for the optimized parameters. Reasonable agreement is found for the short period (< 100 yr) systems between the current study and Dyson, with superior estimation for the longer systems through the inclusion of an additional century of data. Dynamical masses are presented for the systems through the inclusion of parallax measurements.
The Synthetic Light Curve Packages of Budding, and Wilson & Devinney are used to obtain physical ... more The Synthetic Light Curve Packages of Budding, and Wilson & Devinney are used to obtain physical parameters of eclipsing binaries ,and photospheric disturbances where appropriate. The systems modeled are CG·Cygni, R Arae, XY Ursae Majoris, AE Phoenicis, RT Andromedae, ABDoradus, YY Eridani, and RT Sculptoris. The structure and strategy of Budding's Eclipsing BinaryLight Curve Fitting program is considered in detail. An operating manual is provided for theBudding programs, which are found to deduce parameters in reasonable agreement with Hill'sLight, the Wilson-Devinney programs, and Wood's Wink.
This thesis describes the collection, reduction, and analysis of Charge Coupled Detector (CCD) im... more This thesis describes the collection, reduction, and analysis of Charge Coupled Detector (CCD) images of star clusters. The objects studied are primarily in the Large Magellanic Cloud (LMC), a nearby galaxy. The study of these groupings can provide information such as the initial dynamic state of Globular Clusters, the heavy-element enrichment rate of the LMC, the distribution of masses that stars form with, and the validity of given stellar evolution models.
The majority of the observations were collected at Mount John University Observatory (NZ). Procedures for the collection and transfer of the data are described, along with an overview of the analysis facility and CCDs. Statistical moment-based ellipse fitting was applied to the observations, confirming that trends are evident in the position angles and ellipticities of the clusters, as had been reported in the literature. Artificial images of clusters with known parameters were generated and subjected to the same analysis techniques, revealing apparent trends caused by stochastic processes. Caution should therefore be exercised in the interpretation of observational trends in the structure of young LMC clusters. Isochrones were used to date the 19 clusters. The resulting ages are in good agreement with the literature, as are results from profile modeling. There is no evidence for tidal truncation of the young clusters.
Observations were made of two LMC and two Galactic star clusters in a test of imaging clusters with the Vilnius photometric system and a CCD. The colour-magnitude diagrams, distances and interstellar reddenings of the clusters were derived and found to be in agreement with the literature. This is the first time that the standard Vilnius filter set has been used with a CCD. Use of the system for direct imaging of star clusters appears promising. Johnson BV CCD observations were made of the young LMC cluster NGC 2214 and a nearby field using the Anglo-Australian Telescope. It has been suggested in the literature that this elliptical cluster is actually two clusters in the process of merging. No evidence was found from profile fitting or the colour-magnitude diagrams to support this contention. Completeness factors were estimated for the CCD frames. These values were used in conjunction with luminosity functions to estimate the Initial Mass Function (IMF) for NGC 2214. A power- law M^-(l+c) was assumed for the IMF (where M is stellar mass relative to that of the Sun), with a good fit being found for c = 1.01 + 0.09. There is some indication that the low mass end has a smaller gradient than the high mass end of the derived IMF. The value of e is in reasonable agreement with literature values for other Magellanic IMFs, and not substantially different from the poorly determined Galactic IMFs, suggesting the possibility of a 'universal' IMF over the Magellanic Clouds and our Galaxy.
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The majority of the observations were collected at Mount John University Observatory (NZ). Procedures for the collection and transfer of the data are described, along with an overview of the analysis facility and CCDs. Statistical moment-based ellipse fitting was applied to the observations, confirming that trends are evident in the position angles and ellipticities of the clusters, as had been reported in the literature. Artificial images of clusters with known parameters were generated and subjected to the same analysis techniques, revealing apparent trends caused by stochastic processes. Caution should therefore be exercised in the interpretation of observational trends in the structure of young LMC clusters. Isochrones were used to date the 19 clusters. The resulting ages are in good agreement with the literature, as are results from profile modeling. There is no evidence for tidal truncation of the young clusters.
Observations were made of two LMC and two Galactic star clusters in a test of imaging clusters with the Vilnius photometric system and a CCD. The colour-magnitude diagrams, distances and interstellar reddenings of the clusters were derived and found to be in agreement with the literature. This is the first time that the standard Vilnius filter set has been used with a CCD. Use of the system for direct imaging of star clusters appears promising.
Johnson BV CCD observations were made of the young LMC cluster NGC 2214 and a nearby field using the Anglo-Australian Telescope. It has been suggested in the literature that this elliptical cluster is actually two clusters in the process of merging. No evidence was found from profile fitting or the colour-magnitude diagrams to support this contention. Completeness factors were estimated for the CCD frames. These values were used in conjunction with luminosity functions to estimate the Initial Mass Function (IMF) for NGC 2214. A power- law M^-(l+c) was assumed for the IMF (where M is stellar mass relative to that of the Sun), with a good fit being found for c = 1.01 + 0.09. There is some indication that the low mass end has a smaller gradient than the high mass end of the derived IMF. The value of e is in reasonable agreement with literature values for other Magellanic IMFs, and not substantially different from the poorly determined Galactic IMFs, suggesting the possibility of a 'universal' IMF over the Magellanic Clouds and our Galaxy.