933 results on '"Marshall, Jonathan"'
Search Results
2. Epsilon Sagittarii: An Extreme Rapid Rotator with a Decretion Disk
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Bailey, Jeremy, Lewis, Fiona, Howarth, Ian D., Cotton, Daniel V., Marshall, Jonathan P., and Kedziora-Chudczer, Lucyna
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics - Abstract
We report high-precision multi-wavelength linear-polarization observations of the bright B9 (or A0) star $\epsilon$ Sagittarii. The polarization shows the distinctive wavelength dependence expected for a rapidly rotating star. Analysis of the polarization data reveals an angular rotation rate $\omega$ (= $\Omega/\Omega_{crit})$ of 0.995 or greater, the highest yet measured for a star in our galaxy. An additional wavelength-independent polarization component is attributed to electron scattering in a low-density edge-on gas disk that also produces the narrow absorption components seen in the spectrum. Several properties of the star (polarization due to a disk, occasional weak H$\alpha$ emission, and multiple periodicities seen in space photometry) resemble those of Be stars, but the level of activity in all cases is much lower than that of typical Be stars. The stellar properties are inconsistent with single rotating-star evolutionary tracks, indicating that it is most likely a product of binary interaction. The star is an excellent candidate for observation by interferometry, optical spectropolarimetry to detect the \"{O}hman effect, and UV polarimetry; any of which would allow its extreme rotation to be tested and its stellar properties to be refined., Comment: Accepted by Astrophysical Journal, 18 pages, 13 figures
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- 2024
3. AtLAST Science Overview Report
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Booth, Mark, Klaassen, Pamela, Cicone, Claudia, Mroczkowski, Tony, Cordiner, Martin A., Di Mascolo, Luca, Johnstone, Doug, van Kampen, Eelco, Lee, Minju M., Liu, Daizhong, Orlowski-Scherer, John, Saintonge, Amélie, Smith, Matthew W. L., Thelen, Alexander, Wedemeyer, Sven, Akiyama, Kazunori, Andreon, Stefano, Arzoumanian, Doris, Bakx, Tom J. L. C., Bot, Caroline, Bower, Geoffrey, Brajša, Roman, Chen, Chian-Chou, da Cunha, Elisabete, Eden, David, Ettori, Stefano, Gaches, Brandt, Hatziminaoglou, Evanthia, Luppe, Patricia, Magnelli, Benjamin, Marshall, Jonathan P., Montenegro-Montes, Francisco Miguel, Niemack, Michael, Nixon, Conor, de Pater, Imke, Perrott, Yvette, Raimundo, Sandra I., Redaelli, Elena, Richards, Anita, Rybak, Matus, Šarčević, Nikolina, Semenov, Dmitry, Spezzano, Silvia, Srinivasan, Sundar, Stanke, Thomas, Andreani, Paola, Beltrán, Maria T., Butler, Bryan J., Cantalupo, Sebastiano, Dagostino, Miguel Chavez, Duarte-Cabral, Ana, Emonts, Bjorn, Fletcher, Leigh, Gary, Dale E., Gunar, Stanislav, Hacar, Alvaro, Hagedorn, Bendix, Kaminski, Tomek, Kirton, Fiona, de Kleer, Katherine, Kontar, Eduard, Kuan, Yi-Jehng, Lightfoot, John, Lopez-Rodriguez, Enrique, Lundgren, Andreas, Milam, Stefanie N., Mohan, Atul, Moreno, Raphael, Motorina, Galina G., Moullet, Arielle, Pattle, Kate, Pellizzoni, Alberto, Peretto, Nicolas, Ramasawmy, Joanna, Ricci, Claudio, Rigby, Andrew J., Sánchez-Monge, Álvaro, Saberi, Maryam, Shimojo, Masumi, Simionescu, Aurora, Thompson, Mark, Traficante, Alessio, Vignali, Cristian, and White, Stephen M.
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Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Cosmology and Nongalactic Astrophysics ,Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Astrophysics - Solar and Stellar Astrophysics - Abstract
Submillimeter and millimeter wavelengths provide a unique view of the Universe, from the gas and dust that fills and surrounds galaxies to the chromosphere of our own Sun. Current single-dish facilities have presented a tantalising view of the brightest (sub-)mm sources, and interferometers have provided the exquisite resolution necessary to analyse the details in small fields, but there are still many open questions that cannot be answered with current facilities. In this report we summarise the science that is guiding the design of the Atacama Large Aperture Submillimeter Telescope (AtLAST). We demonstrate how tranformational advances in topics including star formation in high redshift galaxies, the diffuse circumgalactic medium, Galactic ecology, cometary compositions and solar flares motivate the need for a 50m, single-dish telescope with a 1-2 degree field of view and a new generation of highly multiplexed continuum and spectral cameras. AtLAST will have the resolution to drastically lower the confusion limit compared to current single-dish facilities, whilst also being able to rapidly map large areas of the sky and detect extended, diffuse structures. Its high sensitivity and large field of view will open up the field of submillimeter transient science by increasing the probability of serendipitous detections. Finally, the science cases listed here motivate the need for a highly flexible operations model capable of short observations of individual targets, large surveys, monitoring programmes, target of opportunity observations and coordinated observations with other observatories. AtLAST aims to be a sustainable, upgradeable, multipurpose facility that will deliver orders of magnitude increases in sensitivity and mapping speeds over current and planned submillimeter observatories., Comment: 47 pages, 12 figures. For further details on AtLAST see https://atlast.uio.no
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- 2024
4. The Dictator and the Mafia: How Rafael Trujillo Partnered with US Criminals to Extend His Power
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Marshall, Jonathan
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- 2018
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5. The Nervous Stage: Nineteenth-Century Neuroscience and the Birth of Modern Theatre by Matthew Wilson Smith (review)
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Marshall, Jonathan W.
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- 2018
6. Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Our Galaxy
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Klaassen, Pamela, Traficante, Alessio, Beltrán, Maria T., Pattle, Kate, Booth, Mark, Lovell, Joshua B., Marshall, Jonathan P., Hacar, Alvaro, Gaches, Brandt A. L., Bot, Caroline, Peretto, Nicolas, Stanke, Thomas, Arzoumanian, Doris, Cabral, Ana Duarte, Duchêne, Gaspard, Eden, David J., Hales, Antonio, Kauffmann, Jens, Luppe, Patricia, Marino, Sebastian, Redaelli, Elena, Rigby, Andrew J., Sánchez-Monge, Álvaro, Schisano, Eugenio, Semenov, Dmitry A., Spezzano, Silvia, Thompson, Mark A., Wyrowski, Friedrich, Cicone, Claudia, Mroczkowski, Tony, Cordiner, Martin A., Di Mascolo, Luca, Johnstone, Doug, van Kampen, Eelco, Lee, Minju M., Liu, Daizhong, Maccarone, Thomas J., Saintonge, Amélie, Smith, Matthew, Thelen, Alexander E., and Wedemeyer, Sven
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Astrophysics - Astrophysics of Galaxies ,Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
As we learn more about the multi-scale interstellar medium (ISM) of our Galaxy, we develop a greater understanding for the complex relationships between the large-scale diffuse gas and dust in Giant Molecular Clouds (GMCs), how it moves, how it is affected by the nearby massive stars, and which portions of those GMCs eventually collapse into star forming regions. The complex interactions of those gas, dust and stellar populations form what has come to be known as the ecology of our Galaxy. Because we are deeply embedded in the plane of our Galaxy, it takes up a significant fraction of the sky, with complex dust lanes scattered throughout the optically recognisable bands of the Milky Way. These bands become bright at (sub-)millimetre wavelengths, where we can study dust thermal emission and the chemical and kinematic signatures of the gas. To properly study such large-scale environments, requires deep, large area surveys that are not possible with current facilities. Moreover, where stars form, so too do planetary systems, growing from the dust and gas in circumstellar discs, to planets and planetesimal belts. Understanding the evolution of these belts requires deep imaging capable of studying belts around young stellar objects to Kuiper belt analogues around the nearest stars. Here we present a plan for observing the Galactic Plane and circumstellar environments to quantify the physical structure, the magnetic fields, the dynamics, chemistry, star formation, and planetary system evolution of the galaxy in which we live with AtLAST; a concept for a new, 50m single-dish sub-mm telescope with a large field of view which is the only type of facility that will allow us to observe our Galaxy deeply and widely enough to make a leap forward in our understanding of our local ecology., Comment: 27 pages, submitted to Open Research Europe as part of the AtLAST collection: https://open-research-europe.ec.europa.eu/collections/atlast/about
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- 2024
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7. Hydrological connectivity and environment characteristics explain spatial variation in fish assemblages in a wet–dry tropical river
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O’Mara, Kaitlyn, Venarsky, Michael, Stewart-Koster, Ben, McGregor, Glenn B., Schulz, Cameron, Marshall, Jonathan, and Bunn, Stuart E.
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- 2024
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8. Lost in the Forest: Encoding categorical variables and the absent levels problem
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Smith, Helen L., Biggs, Patrick J., French, Nigel P., Smith, Adam N. H., and Marshall, Jonathan C.
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- 2024
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9. Sudden extreme obscuration of a Sun-like main-sequence star: evolution of the circumstellar dust around ASASSN-21qj
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Marshall, Jonathan P., Ertel, Steve, Kemper, Francisca, del Burgo, Carlos, Otten, Gilles P. P. L., Scicluna, Peter, Zeegers, Sascha T., Ribas, Álvaro, and Morata, Oscar
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
ASASSN-21qj is a distant Sun-like star that recently began an episode of deep dimming events after no prior recorded variability. Here we examine archival and newly obtained optical and near-infrared data of this star. The deep aperiodic dimming and absence of previous infrared excess are reminiscent of KIC 8462852 (``Boyajian's Star''). The observed occultations are consistent with a circumstellar cloud of sub-micron-sized dust grains composed of amorphous pyroxene, with a minimum mass of $1.50~\pm~0.04\times10^{-9}~M_{\oplus}$ derived from the deepest occultations, and a minimum grain size of $0.29^{+0.01}_{-0.18}~\mu$m assuming a power law size distribution. We further identify the first evidence of near-infrared excess in this system from NEOWISE 3.4 and 4.6~$\mu$m observations. The excess emission implies a total circumstellar dust mass of around $10^{-6} M_{\oplus}$, comparable to the extreme, variable discs associated with terrestrial planet formation around young stars. The quasiperiodic recurrence of deep dips and the inferred dust temperature (ranging from 1800 to 700~K across the span of observations) independently point to an orbital distance of $\simeq$0.2~au for the dust, supporting the occulting material and excess emission being causally linked. The origin of this extended, opaque cloud is surmised to be the breakup of one or more exocometary bodies., Comment: 14 pages, 6 figures, 1 table, published in ApJ
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- 2023
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10. Disputes over coal mining and gas drilling in an Australian country town
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Marshall, Jonathan Paul
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- 2023
11. Diet-habitat ecology of invasive tilapia and native fish in a tropical river catchment following a tilapia invasion
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O’Mara, Kaitlyn, Venarsky, Michael, Marshall, Jonathan, and Stewart-Koster, Ben
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- 2024
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12. Multi-wavelength aperture polarimetry of debris disc host stars
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Marshall, Jonathan P., Cotton, Daniel V., Bott, Kimberly, Bailey, Jeremy, Kedziora-Chudczer, Lucyna, and Brown, Emma L.
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
Debris discs around main sequence stars have been extensively characterised from infrared to millimetre wavelengths through imaging, spectroscopic, and total intensity (scattered light and/or thermal emission) measurements. Polarimetric observations have only been used sparingly to interpret the composition, structure, and size of dust grains in these discs. Here we present new multi-wavelength aperture polarisation observations with parts-per-million sensitivity of a sample of twelve bright debris discs, spanning a broad range of host star spectral types, and disc properties. These measurements were mostly taken with the HIgh Precision Polarimetric Instrument on the Anglo-Australian Telescope. We combine these polarisation observations with the known disc architectures and geometries of the discs to interpret the measurements. We detect significant polarisation attributable to circumstellar dust from HD 377 and HD 39060, and find tentative evidence for HD 188228 and HD 202628., Comment: 25 pages, 8 figures, 9 tables, accepted for publication in MNRAS
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- 2023
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13. Stirred but not shaken: a multi-wavelength view of HD 16743's debris disc
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Marshall, Jonathan P., Milli, Julien, Choquet, Elodie, del Burgo, Carlos, Kennedy, Grant M., Kemper, Francisca, Wyatt, Mark C., Kral, Quentin, and Soummer, Remi
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Astrophysics - Earth and Planetary Astrophysics - Abstract
Planetesimals -- asteroids and comets -- are the building blocks of planets in protoplanetary discs and the source of dust, ice and gas in debris discs. Along with planets they comprise the left-over material after star formation that constitutes a planetary system. Planets influence the dynamics of planetesimals, sculpting the orbits of debris belts to produce asymmetries or gaps. We can constrain the architecture of planetary systems, and infer the presence of unseen planetary companions, by high spatial resolution imaging of debris discs. HD~16743 is a relatively young F-type star that hosts a bright edge-on debris disc. Based on far-infrared \textit{Herschel} observations its disc was thought to be stirred by a planetary companion. Here we present the first spatially resolved observations at near-infrared and millimetre wavelengths with \textit{HST} and ALMA, revealing the disc to be highly inclined at $87\fdg3~^{+1\fdg9}_{-2\fdg5}$ with a radial extent of 157.7$^{+2.6}_{-1.5}$~au and a FWHM of 79.4$^{+8.1}_{-7.8}$~au ($\Delta R/R = 0.5$). The vertical scale height of the disc is $0.13~\pm~0.02$, significantly greater than typically assumed unstirred value of 0.05, and could be indicative of stirring of the dust-producing planetesimals within the disc by bodies at least a few times the mass of Pluto up to 18.3~$M_{\oplus}$ in the single object limit., Comment: 12 pages, 7 figures, 4 tables, accepted for publication in MNRAS
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- 2023
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14. A Mixed Stirring Mechanism for Debris Discs with Giant and Dwarf Planetary Perturbations
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Muñoz-Gutiérrez, Marco A., Marshall, Jonathan P., and Peimbert, Antonio
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Astrophysics - Earth and Planetary Astrophysics - Abstract
Debris discs consist of belts of bodies ranging in size from dust grains to planetesimals; these belts are visible markers of planetary systems around other stars that can reveal the influence of extrasolar planets through their shape and structure. Two key stirring mechanisms -- self-stirring by planetesimals and secular perturbation by an external giant planet -- have been identified to explain the dynamics of planetesimal belts; their relative importance has been studied independently, but are yet to be considered in combination. In this work we perform a suite of 286 N-body simulations exploring the evolution of debris discs over 1~Gyr, combining the gravitational perturbations of both dwarf planets embedded in the discs, and an interior giant planet. Our systems were somewhat modeled after the architecture of the outer Solar system: a Solar mass star, a single massive giant planet at 30~au ($M_{\rm GP} =$ 10 to 316~$\mathrm{M}_{\oplus}$), and a debris disc formed by 100 massive dwarf planets and 1000 massless particles ($M_{\rm DD} =$ 3.16 to 31.6~$\mathrm{M}_{\oplus}$). We present the evolution of both the disc and the giant planet after 1~Gyr. The time evolution of the average eccentricity and inclination of the disc is strongly dependent on the giant planet mass as well as on the remaining disc mass. We also found that efficient stirring is achieved even with small disc masses. In general, we find that a mixed mechanism is more efficient in the stirring of cold debris discs than either mechanism acting in isolation., Comment: Accepted for publication in MNRAS. 11 pages, 6 figures (4 animated). Animated figures can be found at https://figshare.com/projects/Mixed_Stirring_of_Debris_Discs/136118
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- 2023
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15. Evidence for the disruption of a planetary system during the formation of the Helix Nebula
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Marshall, Jonathan P., Ertel, Steve, Birtcil, Eric, Villaver, Eva, Kemper, Francisca, Boffin, Henri, Scicluna, Peter, and Kamath, Devika
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
The persistence of planetary systems after their host stars evolve into their post-main sequence phase is poorly constrained by observations. Many young white dwarf systems exhibit infrared excess emission and/or spectral absorption lines associated with a reservoir of dust (or planetesimals) and its accretion. However, most white dwarfs are too cool to sufficiently heat any circumstellar dust to detectable levels of emission. The Helix Nebula (NGC 7293) is a young, nearby planetary nebula; observations at mid- and far-infrared wavelengths revealed excess emission associated with its central white dwarf (WD 2226-210). The origin of this excess is ambiguous. It could be a remnant planetesimal belt, a cloud of comets, or the remnants of material shed during the post-asymptotic giant branch phase. Here we combine infrared (SOFIA, Spitzer, Herschel ) and millimetre (ALMA) observations of the system to determine the origin of this excess using multi-wavelength imaging and radiative transfer modelling. We find the data are incompatible with a compact remnant planetesimal belt or post-asymptotic giant branch disc, and conclude the dust most likely originates from deposition by a cometary cloud. The measured dust mass, and lifetime of the constituent grains, implies disruption of several thousand Hale-Bopp equivalent comets per year to fuel the observed excess emission around the Helix Nebula's white dwarf., Comment: 15 pages, 3 tables, 4 figures, accepted for publication in AJ
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- 2022
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16. Risk factors for hospitalisation amongst leptospirosis patients in New Zealand
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Sokolova, Maryna, Marshall, Jonathan C, and Benschop, Jackie
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- 2021
17. Staging critical history within the space of the beat or what cultural historians can learn from Public Enemy, NTM, MC Solaar & George Clinton
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Marshall, Jonathan W.
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- 2015
18. Navigating the community renewable energy landscape: An analytics-driven policy formulation
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Taghikhah, Firouzeh Rosa, Taghikhah, Masoud, Marshall, Jonathan Paul, and Voinov, Alexey
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- 2024
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19. Development of a multiplex droplet digital PCR assay for simultaneous detection and quantification of Escherichia coli, E. marmotae, and E. ruysiae in water samples
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Moinet, Marie, Collis, Rose M., Rogers, Lynn, Devane, Megan L., Biggs, Patrick J., Stott, Rebecca, Marshall, Jonathan, Muirhead, Richard, and Cookson, Adrian L.
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- 2024
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20. The unique aquatic ecosystem of Talaroo Hot Springs
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Negus, Peter, Marshall, Jonathan C, Steward, Alisha L, McGregor, Glenn B, and O'Connor, Ruth
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- 2021
21. Modeled small airways lung deposition of two fixed-dose triple therapy combinations assessed with in silico functional respiratory imaging
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Usmani, Omar, Li, Grace, De Backer, Jan, Sadafi, Hosein, Wu, Libo, and Marshall, Jonathan
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- 2023
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22. Accurate, non-destructive, and high-throughput age estimation for Golden perch (Macquaria ambigua spp.) using DNA methylation
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Mayne, Benjamin, Espinoza, Tom, Crook, David A., Anderson, Chloe, Korbie, Darren, Marshall, Jonathan C., Kennard, Mark J., Harding, Doug J., Butler, Gavin L., Roberts, Brien, Whiley, Josh, and Marshall, Sharon
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- 2023
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23. Four new PLanetesimals Around TYpical and Pre-main seqUence Stars (PLATYPUS) Debris Discs at 8.8mm
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Norfolk, Brodie J., Maddison, Sarah T., Marshall, Jonathan P., Kennedy, Grant M., Duchêne, Gaspard, Wilner, David J., Pinte, Christophe, Moór, Attila, Matthews, Brenda, Ábrahám, Péter, Kóspál, Ágnes, and van der Marel, Nienke
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
Millimetre continuum observations of debris discs can provide insights into the physical and dynamical properties of the unseen planetesimals that these discs host. The material properties and collisional models of planetesimals leave their signature on the grain size distribution, which can be traced through the millimetre spectral index. We present 8.8 mm observations of the debris discs HD 48370, CPD 72 2713, HD 131488, and HD 32297 using the Australian Telescope Compact Array (ATCA) as part of the PLanetesimals Around TYpicalPre-main seqUence Stars (PLATYPUS) survey. We detect all four targets with a characteristic beam size of 5 arcseconds and derive a grain size distribution parameter that is consistent with collisional cascade models and theoretical predictions for parent planetesimal bodies where binding is dominated by self-gravity. We combine our sample with 19 other millimetre-wavelength detected debris discs from the literature and calculate a weighted mean grain size power law index which is close to analytical predictions for a classical steady state collisional cascade model. We suggest the possibility of two distributions of q in our debris disc sample; a broad distribution (where q is approximately 3.2 to 3.7) for "typical" debris discs (gas-poor/non-detection), and a narrow distribution (where q is less than 3.2) for bright gas-rich discs. Or alternatively, we suggest that there exists an observational bias between the grain size distribution parameter and absolute flux which may be attributed to the detection rates of faint debris discs at cm wavelengths., Comment: 10 pages, 4 figures, accepted
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- 2021
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24. Letter to the Editor Regarding “Fluticasone Furoate/Umeclidinium/Vilanterol (FF/UMEC/VI) Triple Therapy Compared with Other Therapies for the Treatment of COPD: A Network Meta-Analysis”
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Marshall, Jonathan, Sharma, Akanksha, Darken, Patrick, Ouwens, Mario, Singh, Barinder, and Tansey-Dwyer, Deniz
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- 2023
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25. Polarization of hot Jupiter systems: a likely detection of stellar activity and a possible detection of planetary polarization
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Bailey, Jeremy, Bott, Kimberly, Cotton, Daniel V., Kedziora-Chudczer, Lucyna, Zhao, Jinglin, Evensberget, Dag, Marshall, Jonathan P., Wright, Duncan, and Lucas, P. W.
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
We present high-precision linear polarization observations of four bright hot Jupiter systems ($\tau$ Boo, HD 179949, HD 189733 and 51 Peg) and use the data to search for polarized reflected light from the planets. The data for 51 Peg are consistent with a reflected light polarization signal at about the level expected with 2.8$\sigma$ significance and a false alarm probability of 1.9 per cent. More data will be needed to confirm a detection of reflected light in this system. HD 189733 shows highly variable polarization that appears to be most likely the result of magnetic activity of the host star. This masks any polarization due to reflected light, but a polarization signal at the expected level of $\sim$20 ppm cannot be ruled out. $\tau$ Boo and HD 179949 show no evidence for polarization due to reflected light. The results are consistent with the idea that many hot Jupiters have low geometric albedos. Conclusive detection of polarized reflected light from hot Jupiters is likely to require further improvements in instrument sensitivity., Comment: 16 pages, 8 figures, accepted by MNRAS
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- 2021
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26. Polarimetric and radiative transfer modelling of HD 172555
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Marshall, Jonathan P., Cotton, Daniel V., Scicluna, Peter, Bailey, Jeremy, Kedziora-Chudczer, Lucyna, and Bott, Kimberly
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
The debris disc around HD 172555 was recently imaged in near-infrared polarised scattered light by the Very Large Telescope's Spectro-Polarimetric High-contrast Exoplanet REsearch instrument. Here we present optical aperture polarisation measurements of HD 172555 by the HIgh Precision Polarimetric Instrument (HIPPI), and its successor HIPPI-2 on the Anglo-Australian Telescope. We seek to refine constraints on the disc's constituent dust grains by combining our polarimetric measurements with available infrared and millimetre photometry to model the scattered light and continuum emission from the disc. We model the disc using the 3D radiative transfer code Hyperion, assuming the orientation and extent of the disc as obtained from the SPHERE observation. After correction for the interstellar medium contribution, our multi-wavelength HIPPI/-2 observations (both magnitude and orientation) are consistent with the recent SPHERE polarisation measurement with a fractional polarisation $p = 62.4 \pm 5.2$~ppm at 722.3 nm, and a position angle $\theta = 67 \pm 3^{\circ}$. The multi-wavelength polarisation can be adequately replicated by compact, spherical dust grains (i.e. from Mie theory) that are around 1.2 $\mu$m in size, assuming astronomical silicate composition, or 3.9 $\mu$m assuming a composition derived from radiative transfer modelling of the disc. We were thus able to reproduce both the spatially resolved disc emission and polarisation with a single grain composition model and size distribution., Comment: 17 pages, 7 figures, 12 tables. (incl. appendices); accepted for publication in MNRAS
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- 2020
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27. Dust Populations in the Iconic Vega Planetary System Resolved by ALMA
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Matrà, Luca, Dent, William R. F., Wilner, David J., Marino, Sebastián, Wyatt, Mark C., Marshall, Jonathan P., Su, Kate Y. L., Chavez, Miguel, Hales, Antonio, Hughes, A. Meredith, Greaves, Jane S., and Corder, Stuartt A.
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
The Vega planetary system hosts the archetype of extrasolar Kuiper belts, and is rich in dust from the sub-au region out to 100's of au, suggesting intense dynamical activity. We present ALMA mm observations that detect and resolve the outer dust belt from the star for the first time. The interferometric visibilities show that the belt can be fit by a Gaussian model or by power-law models with a steep inner edge (at 60-80 au). The belt is very broad, extending out to at least 150-200 au. We strongly detect the star and set a stringent upper limit to warm dust emission previously detected in the infrared. We discuss three scenarios that could explain the architecture of Vega's planetary system, including the new {ALMA} constraints: no outer planets, a chain of low-mass planets, and a single giant planet. The planet-less scenario is only feasible if the outer belt was born with the observed sharp inner edge. If instead the inner edge is currently being truncated by a planet, then the planet must be $\gtrsim$6 M$_{\oplus}$ and at $\lesssim71$ au to have cleared its chaotic zone within the system age. In the planet chain scenario, outward planet migration and inward scattering of planetesimals could produce the hot and warm dust observed in the inner regions of the system. In the single giant planet scenario, an asteroid belt could be responsible for the warm dust, and mean motion resonances with the planet could put asteroids on star-grazing orbits, producing the hot dust., Comment: 18 pages, 3 figures, Accepted for publication in ApJ
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- 2020
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28. AU Mic b is the Youngest Planet to have a Spin-Orbit Alignment Measurement
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Addison, Brett C., Horner, Jonathan, Wittenmyer, Robert A., Heitzmann, Alexis, Plavchan, Peter, Wright, Duncan J., Nicholson, Belinda A., Marshall, Jonathan P., Clark, Jake T., Gunther, Maximilian N., Kane, Stephen R., Hirano, Teruyuki, Wang, Songhu, Kielkopf, John, Shporer, Avi, Tinney, C. G., Zhang, Hui, Ballard, Sarah, Bowler, Brendan P., Mengel, Matthew W., Okumura, Jack, Gaidos, Eric, and Wang, Xian-Yu
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Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Solar and Stellar Astrophysics - Abstract
We report measurements of the sky-projected spin-orbit angle for AU\,Mic\,b, a Neptune-size planet orbiting a very young ($\sim20$\,Myr) nearby pre-main sequence M dwarf star which also hosts a bright, edge-on, debris disk. The planet was recently discovered from preliminary analysis of radial velocity observations and confirmed to be transiting its host star from photometric data from the NASA's \textit{TESS} mission. We obtained radial velocity measurements of AU\,Mic over the course of two partially observable transits and one full transit of planet b from high-resolution spectroscopic observations made with the {\textsc{Minerva}}-Australis telescope array. Only a marginal detection of the Rossiter--McLaughlin effect signal was obtained from the radial velocities, in part due to AU Mic being an extremely active star and the lack of full transit coverage plus sufficient out-of-transit baseline. As such, a precise determination of the obliquity for AU\,Mic\,b is not possible in this study and we find a sky-projected spin-orbit angle of $\lambda = 47{^{+26}_{-54}}^{\circ}$. This result is consistent with both the planet's orbit being aligned or highly misaligned with the spin-axis of its host star. Our measurement independently agrees with, but is far less precise than observations carried out on other instruments around the same time that measure a low obliquity orbit for the planet. AU\,Mic is the youngest exoplanetary system for which the projected spin-orbit angle has been measured, making it a key data point in the study of the formation and migration of exoplanets -- particularly given that the system is also host to a bright debris disk., Comment: 15 pages, 6 figures, 3 tables. Published in the Astronomical Journal on 10/09/2021
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- 2020
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29. Polarization measurements of the polluted white dwarf G29-38
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Cotton, Daniel V., Bailey, Jeremy, Pringle, J. E., Sparks, William B., von Hippel, Ted, and Marshall, Jonathan P.
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We have made high precision polarimetric observations of the polluted white dwarf G29-38 with the HIgh Precision Polarimetric Instrument 2. The observations were made at two different observatories -- using the 8.1-m Gemini North Telescope and the 3.9-m Anglo AustralianTelescope -- and are consistent with each other. After allowing for a small amount of interstellar polarization, the intrinsic linear polarization of the system is found to be 275.3 +/- 31.9 parts-per-million at a position angle of 90.8 +/- 3.8 degrees in the SDSS g' band. We compare the observed polarization with the predictions of circumstellar disc models. The measured polarization is small in the context of the models we develop which only allows us to place limits on disc inclination and Bond albedo for optically thin disc geometries. In this case either the inclination is near face-on or the albedo is small -- likely in the range 0.05 to 0.15 -- which is in line with other debris disc measurements. A preliminary search for the effects of G29-38's pulsations in the polarization signal produced inconsistent results. This may be caused by beating effects, indicate a clumpy dust distribution, or be a consequence of measurement systematics., Comment: 15 pages, 6 figures, 4 tables. Accepted to MNRAS
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- 2020
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30. Studies of Evolved Stars in the Next Decade: EAO Submillimetre Futures White Paper Series, 2019
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Scicluna, Peter, Shinnaga, Hiroko, Marshall, Jonathan, Wouterloot, Jan, McDonald, Iain, Goldman, Steven, Wallström, Sofia, van Loon, Jacco Th., Dharmawardena, Thavisha, Fanciullo, Lapo, and Srinivasan, Sundar
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
This white paper discusses recent progress in the field of evolved stars, primarily highlighting the contributions of the James Clerk Maxwell Telescope. It discusses the ongoing project, the \emph{Nearby Evolved Stars Survey} (NESS), and the potential to build upon NESS in the next decade. It then outlines a number of science cases which may become feasible with the proposed 850\,$\mu$m camera which is due to become available at the JCMT in late 2022. These include mapping the extended envelopes of evolved stars, including in polarisation, and time-domain monitoring of their variations. The improved sensitivity of the proposed instrument will facilitate statistical studies that put the morphology, polarisation properties and sub-mm variability in perspective with a relatively modest commitment of time that would be impossible with current instrumentation. We also consider the role that could be played by other continuum wavelengths, heterodyne instruments or other facilities in contributing towards these objectives., Comment: 11 pages, 2 figures; Part of the 2019 EAO Submillimetre Futures Paper Series, https://www.eaobservatory.org//jcmt/wp-content/uploads/sites/2/2019/11/EAOSubmmFuturesWPs.pdf
- Published
- 2020
31. ABOVEGROUND CARBON ACCUMULATION BY SECOND-GROWTH FORESTS AFTER DEFORESTATION IN HAWAII
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Hughes, R. Flint, Grossman, Dennis, Sowards, Travis G., Marshall, Jonathan D., and Mueller-Dombois, Dieter
- Published
- 2022
32. Do Cane Toads (Rhinella marina) Impact Desert Spring Ecosystems?
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Clifford, Sara E, Steward, Alisha L, Negus, Peter M, Blessing, Joanna J, Marshall, Jonathan C, and BHL Australia
- Published
- 2020
33. The Nearby Evolved Stars Survey: I. JCMT/SCUBA-2 Sub-millimetre detection of the detached shell of U Antliae
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Dharmawardena, Thavisha E., Kemper, Francisca, Srinivasan, Sundar, Scicluna, Peter, Marshall, Jonathan P., Wouterloot, Jan G. A., Greaves, Jane, Goldman, Steven R., van Loon, Jacco Th., Matsuura, Mikako, McDonald, Iain, He, Jinhua, Zijlstra, Albert A., Toalá, Jesús A., Wallström, Sofia H. J., Kim, Hyosun, Trejo, Alfonso, Ventura, Paolo, Lagadec, Eric, Boyer, Martha L., Liu, Tie, Rau, Gioia, Izumiura, Hideyuki, Cami, Jan, Holland, Wayne, Jones, Olivia, and Shinnaga, Hiroko
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Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
We present the highest resolution single-dish submillimetre observations of the detached shell source U Antliae to date. The observations were obtained at $450~\micron$ and $850~\micron$ with SCUBA-2 instrument on the James Clerk Maxwell Telescope as part of the Nearby Evolved Stars Survey. The emission at $850~\micron$ peaks at $40\arcsec$ with hints of a second peak seen at $\sim 20\arcsec$. The emission can be traced out to a radius of $56\arcsec$ at a $3\sigma$ level. The outer peak observed at $850~\micron$ aligns well with the peak observed at Herschel/PACS wavelengths. With the help of spectral energy distribution fitting and radiative transfer calculations of multiple-shell models for the circumstellar envelope, we explore the various shell structures and the variation of grain sizes along the in the circumstellar envelope. We determine a total shell dust mass of $(2.0 \pm 0.3) \times 10^{-5}$ M$_{\odot}$ and established that the thermal pulse which gave rise to the detached shell occurred 3500 $\pm$ 500 years ago., Comment: Accepted for publication in MNRAS
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- 2019
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34. The Sub-mm Variability of IRC+10216 and $o$ Ceti
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Dharmawardena, Thavisha E., Kemper, Francisca, Wouterloot, Jan G. A., Scicluna, Peter, Marshall, Jonathan P., and Wallstrom, Sofia H. J.
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Astrophysics - Solar and Stellar Astrophysics - Abstract
We present the sub-mm variability of two of the most well studied AGB stars, IRC+10216 and $o$ Ceti. The data are obtained at $450~\micron$ and $850~\micron$ as part of pointing calibration observations for the James Clerk Maxwell Telescope's SCUBA-2 instrument over a span of 7 years. The periods are derived using non-parametric methods, \texttt{Gatspy Supersmoother} and \texttt{P4J} in order not to assume an underlying shape to the periodicity. These were compared to two Lomb-Scargle parametric methods. We find that for both sources and wavelengths the periods derived from all methods are consistent within $1\sigma$. The $850~\micron$ phase folded light curves of IRC+10216 show a time lag of $\sim 540$ days compared to its optical counterpart. We explore the origins of the sub-mm variability and the phase lag using radiative transfer models. Combining the modelling with findings in the literature, we find that the sub-mm emission and phase lag can be partially attributed to the dust formation/destruction cycle. A second, unknown mechanism must be invoked; we defer an investigation of the origin and nature of this mechanism to a future work., Comment: Accepted for publication in MNRAS
- Published
- 2019
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35. The REASONS Survey: Resolved Millimeter Observations of a Large Debris Disk Around the Nearby F Star HD 170773
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Sepulveda, Aldo G., Matra, Luca, Kennedy, Grant M., del Burgo, Carlos, Oberg, Karin I., Wilner, David J., Marino, Sebastian, Booth, Mark, Carpenter, John M., Davies, Claire L., Dent, William R. F., Ertel, Steve, Lestrade, Jean-Francois, Marshall, Jonathan P., Milli, Julien, Wyatt, Mark C., MacGregor, Meredith A., and Matthews, Brenda C.
- Subjects
Astrophysics - Earth and Planetary Astrophysics - Abstract
Debris disks are extrasolar analogs to our own Kuiper Belt and they are detected around at least 17% of nearby Sun-like stars. The morphology and dynamics of a disk encode information about its history, as well as that of any exoplanets within the system. We used ALMA to obtain 1.3 mm observations of the debris disk around the nearby F5V star HD 170773. We image the face-on ring and determine its fundamental parameters by forward-modeling the interferometric visibilities through a Markov Chain Monte Carlo approach. Using a symmetric Gaussian surface density profile, we find a 71 $\pm$ 4 au wide belt with a radius of 193$^{+2}_{-3}$ au, a relatively large radius compared to most other millimeter-resolved belts around late A / early F type stars. This makes HD 170773 part of a group of four disks around A and F stars with radii larger than expected from the recently reported planetesimal belt radius - stellar luminosity relation. Two of these systems are known to host directly imaged giant planets, which may point to a connection between large belts and the presence of long-period giant planets. We also set upper limits on the presence of CO and CN gas in the system, which imply that the exocomets that constitute this belt have CO and HCN ice mass fractions of <77% and <3%, respectively, consistent with Solar System comets and other exocometary belts., Comment: 14 pages, 6 figures, accepted to ApJ
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- 2019
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36. The HD 181433 Planetary System: Dynamics and a New Orbital Solution
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Horner, Jonathan, Wittenmyer, Robert A, Wright, Duncan J, Hinse, Tobias C, Marshall, Jonathan P, Kane, Stephen R, Clark, Jake T, Mengel, Matthew, Agnew, Matthew T, and Johns, Daniel
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Astrophysics - Earth and Planetary Astrophysics - Abstract
We present a detailed analysis of the orbital stability of the HD 181433 planetary system, finding it to exhibit strong dynamical instability across a wide range of orbital eccentricities, semi-major axes, and mutual inclinations. We also analyse the behaviour of an alternative system architecture, proposed by Campanella (2011), and find that it offers greater stability than the original solution, as a result of the planets being trapped in strong mutual resonance. We take advantage of more recent observations to perform a full refit of the system, producing a new planetary solution. The best-fit orbit for HD 181433 d now places the planet at a semi-major axis of 6.60$\pm$0.22 au, with an eccentricity of 0.469$\pm$0.013. Extensive simulations of this new system architecture reveal it to be dynamically stable across a broad range of potential orbital parameter space, increasing our confidence that the new solution represents the ground truth of the system. Our work highlights the advantage of performing dynamical simulations of candidate planetary systems in concert with the orbital fitting process, as well as supporting the continuing monitoring of radial velocity planet search targets., Comment: 16 pages + 6 page appendix containing RV data; 5 tables, 9 figures. To appear in The Astronomical Journal
- Published
- 2019
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37. The wavelength dependence of interstellar polarization in the Local Hot Bubble
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Cotton, Daniel V., Marshall, Jonathan P., Frisch, Priscilla C., Kedziora-Chudzer, Lucyna, Bailey, Jeremy, Bott, Kimberly, Wright, Duncan J., Wyatt, Mark C., and Kennedy, Grant M.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
The properties of dust in the interstellar medium (ISM) nearest the Sun are poorly understood because the low column densities of dust toward nearby stars induce little photometric reddening, rendering the grains largely undetectable. Stellar polarimetry offers one pathway to deducing the properties of this diffuse material. Here we present multi-wavelength aperture polarimetry measurements of seven bright stars chosen to probe interstellar polarization near the edge of the Local Hot Bubble (LHB) - an amorphous region of relatively low density interstellar gas and dust extending ~70-150 pc from the Sun. The measurements were taken using the HIgh Precision Polarimetric Instrument (HIPPI) on the 3.9-m Anglo-Australian Telescope. HIPPI is an aperture stellar polarimeter with a demonstrated sensitivity of 4.3 parts-per-million (ppm). Of the stars observed two are polarized to a much greater degree than the others; they have a wavelength of maximum polarization ($\lambda_{max}$) of ~550 $\pm$ 20 nm - similar to that of stars beyond the LHB - and we conclude that they are in the wall of the LHB. The remaining five stars have polarizations of ~70 to 160 ppm, of these four have a much bluer $\lambda_{max}$, ~350 $\pm$ 50 nm. Bluer values of $\lambda_{max}$ may indicate grains shocked during the evolution of the Loop I Superbubble. The remaining star, HD 4150 is not well fit by a Serkowski curve, and may be intrinsically polarized., Comment: 12 pages, 2 figures, 6 tables, accepted to MNRAS
- Published
- 2018
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- View/download PDF
38. The polarization of the planet-hosting WASP-18 system
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Bott, Kimberly, Bailey, Jeremy, Cotton, Daniel V., Kedziora-Chudczer, Lucyna, Marshall, Jonathan P., and Meadows, Victoria S.
- Subjects
Astrophysics - Earth and Planetary Astrophysics - Abstract
We report observations of the linear polarization of the WASP-18 system, which harbors a very massive ( approx 10 M_J) planet orbiting very close to its star with an orbital period of 0.94 days. We find the WASP-18 system is polarized at about 200 parts-per-million (ppm), likely from the interstellar medium predominantly, with no strong evidence for phase dependent modulation from reflected light from the planet. We set an upper limit of 40 ppm (99% confidence level) on the amplitude of a reflected polarized light planetary signal. We compare the results with models for a number of processes that may produce polarized light in a planetary system to determine if we can rule out any phenomena with this limit. Models of reflected light from thick clouds can approach or exceed this limit, but such clouds are unlikely at the high temperature of the WASP-18b atmosphere. Additionally, we model the expected polarization resulting from the transit of the planet across the star and find this has an amplitude of about 1.6 ppm, which is well below our detection limits. We also model the polarization due to the tidal distortion of the star by the massive planet and find this is also too small to be measured currently., Comment: 23 pages, 10 Figures, 6 Tables, Accepted to AJ
- Published
- 2018
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39. Extended-spectrum β-lactamase- and AmpC β-lactamase-producing Enterobacterales associated with urinary tract infections in the New Zealand community: a case-control study
- Author
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Toombs-Ruane, Leah J., Marshall, Jonathan C., Benschop, Jackie, Drinković, Dragana, Midwinter, Anne C., Biggs, Patrick J., Grange, Zoë, Baker, Michael G., Douwes, Jeroen, Roberts, Mick G., French, Nigel P., and Burgess, Sara A.
- Published
- 2023
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40. 6. Trolling and the Orders and Disorders of Communication in ‘(Dis)Information Society’
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Marshall, Jonathan Paul, primary
- Published
- 2022
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41. Atacama Large Aperture Submillimeter Telescope (AtLAST) science: Our Galaxy
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Klaassen, Pamela, primary, Traficante, Alessio, additional, Beltrán, Maria, additional, Pattle, Kate, additional, Booth, Mark, additional, Lovell, Joshua, additional, Marshall, Jonathan, additional, Hacar, Alvaro, additional, Gaches, Brandt, additional, Bot, Caroline, additional, Peretto, Nicolas, additional, Stanke, Thomas, additional, Arzoumanian, Doris, additional, Duarte Cabral, Ana, additional, Duchêne, Gaspard, additional, Eden, David, additional, Hales, Antonio, additional, Kauffmann, Jens, additional, Luppe, Patricia, additional, Marino, Sebastian, additional, Redaelli, Elena, additional, Rigby, Andrew, additional, Sánchez-Monge, Álvaro, additional, Schisano, Eugenio, additional, Semenov, Dmitry, additional, Spezzano, Silvia, additional, Thompson, Mark, additional, Wyrowski, Friedrich, additional, Cicone, Claudia, additional, Mroczkowski, Tony, additional, Cordiner, Martin, additional, Di Mascolo, Luca, additional, Johnstone, Doug, additional, van Kampen, Eelco, additional, Lee, Minju, additional, Liu, Daizhong, additional, Maccarone, Thomas, additional, Saintonge, Amélie, additional, Smith, Matthew, additional, Thelen, Alexander, additional, and Wedemeyer, Sven, additional
- Published
- 2024
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42. Introduction
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Marshall, Jonathan P., primary and Cupitt, Rebekah, additional
- Published
- 2024
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43. Spatial risk of disease transmission between wild bovids and livestock in Thailand
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Horpiencharoen, Wantida, primary, Marshall, Jonathan C., additional, Muylaert, Renata L., additional, John, Reju Sam, additional, and Hayman, David T. S., additional
- Published
- 2024
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44. Budesonide/Glycopyrrolate/Formoterol for the Management of COPD in a UK Primary Care Population: Real-World Use and Early Medication Success
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Müllerová, Hana, primary, Chan, Jeffrey Shi Kai, additional, Heatley, Heath, additional, Carter, Victoria, additional, Townend, John, additional, Skinner, Derek, additional, Franzén, Stefan, additional, Marshall, Jonathan, additional, and Price, David, additional
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- 2024
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45. Dairy Cattle Density and Temporal Patterns of Human Campylobacteriosis and Cryptosporidiosis in New Zealand
- Author
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Grout, Leah, Marshall, Jonathan, Hales, Simon, Baker, Michael G., and French, Nigel
- Published
- 2022
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46. Extended Dust Emission from Nearby Evolved Stars
- Author
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Dharmawardena, Thavisha E., Kemper, Francisca, Scicluna, Peter, Wouterloot, Jan G. A., Trejo, Alfonso, Srinivasan, Sundar, Cami, Jan, Zijlstra, Albert, and Marshall, Jonathan P.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
We present JCMT SCUBA-2 $450\mu$m and $850\mu$m observations of 14 Asymptotic Giant Branch (AGB) stars (9 O--rich, 4 C-rich and 1 S--type) and one Red Supergiant (RSG) in the Solar Neighbourhood. We combine these observations with \emph{Herschel}/PACS observations at $70\mu$m and $160\mu$m and obtain azimuthally-averaged surface-brightness profiles and their PSF subtracted residuals. The extent of the SCUBA-2 850 $\mu$m emission ranges from 0.01 to 0.16 pc with an average of $\sim40\%$ of the total flux being emitted from the extended component. By fitting a modified black-body to the four-point SED at each point along the radial profile we derive the temperature ($T$), spectral index of dust emissivity ($\beta$) and dust column density ($\Sigma$) as a function of radius. For all the sources, the density profile deviates significantly from what is expected for a constant mass-loss rate, showing that all the sources have undergone variations in mass-loss during this evolutionary phase. In combination with results from CO line emission, we determined the dust-to-gas mass ratio for all the sources in our sample. We find that, when sources are grouped according to their chemistry, the resulting average dust-to-gas ratios are consistent with the respective canonical values. However we see a range of values with significant scatter which indicate the importance of including spatial information when deriving these numbers., Comment: 18 pages plus 13 pages of supplementary figures. Accepted for publication on MNRAS on 24/05/2018. Updated 05/07/2018: Fixed secondary axes (pc axes) on Radial Profiles in all figures
- Published
- 2018
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- View/download PDF
47. Kuiper Belt Analogues in Nearby M-type Planet-host Systems
- Author
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Kennedy, Grant M., Bryden, Geoffrey, Ardila, David, Eiroa, Carlos, Lestrade, Jean-François, Marshall, Jonathan P., Matthews, Brenda C., Moro-Martin, Amaya, and Wyatt, Mark C.
- Subjects
Astrophysics - Earth and Planetary Astrophysics - Abstract
We present the results of a Herschel survey of 21 late-type stars that host planets discovered by the radial velocity technique. The aims were to discover new disks in these systems and to search for any correlation between planet presence and disk properties. In addition to the known disk around GJ 581, we report the discovery of two new disks, in the GJ 433 and GJ 649 systems. Our sample therefore yields a disk detection rate of 14%, higher than the detection rate of 1.2% among our control sample of DEBRIS M-type stars with 98% confidence. Further analysis however shows that the disk sensitivity in the control sample is about a factor of two lower in fractional luminosity than for our survey, lowering the significance of any correlation between planet presence and disk brightness below 98%. In terms of their specific architectures, the disk around GJ 433 lies at a radius somewhere between 1 and 30au. The disk around GJ 649 lies somewhere between 6 and 30au, but is marginally resolved and appears more consistent with an edge-on inclination. In both cases the disks probably lie well beyond where the known planets reside (0.06-1.1au), but the lack of radial velocity sensitivity at larger separations allows for unseen Saturn-mass planets to orbit out to $\sim$5au, and more massive planets beyond 5au. The layout of these M-type systems appears similar to Sun-like star + disk systems with low-mass planets., Comment: MNRAS, in press
- Published
- 2018
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48. Disinformation society, communication and cosmopolitan democracy
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Marshall, Jonathan Paul
- Published
- 2017
49. Tutorial on kernel estimation of continuous spatial and spatiotemporal relative risk with accompanying instruction in R
- Author
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Davies, Tilman M., Marshall, Jonathan C., and Hazelton, Martin L.
- Subjects
Statistics - Methodology - Abstract
Kernel smoothing is a highly flexible and popular approach for estimation of probability density and intensity functions of continuous spatial data. In this role it also forms an integral part of estimation of functionals such as the density-ratio or "relative risk" surface. Originally developed with the epidemiological motivation of examining fluctuations in disease risk based on samples of cases and controls collected over a given geographical region, such functions have also been successfully employed across a diverse range of disciplines where a relative comparison of spatial density functions has been of interest. This versatility has demanded ongoing developments and improvements to the relevant methodology, including use spatially adaptive smoothers; tests of significantly elevated risk based on asymptotic theory; extension to the spatiotemporal domain; and novel computational methods for their evaluation. In this tutorial paper we review the current methodology, including the most recent developments in estimation, computation and inference. All techniques are implemented in the new software package sparr, publicly available for the R language, and we illustrate its use with a pair of epidemiological examples.
- Published
- 2017
50. SONS: The JCMT legacy survey of debris discs in the submillimetre
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Holland, Wayne S., Matthews, Brenda C., Kennedy, Grant M., Greaves, Jane S., Wyatt, Mark C., Booth, Mark, Bastien, Pierre, Bryden, Geoff, Butner, Harold, Chen, Christine H., Chrysostomou, Antonio, Davies, Claire L., Dent, William R. F., Di Francesco, James, Duchene, Gaspard, Gibb, Andy G., Friberg, Per, Ivison, Rob J., Jenness, Tim, Kavelaars, JJ, Lawler, Samantha, Lestrade, Jean-Francois, Marshall, Jonathan P., Moro-Martin, Amaya, Panic, Olja, Phillips, Neil, Serjeant, Stephen, Schieven, Gerald H., Sibthorpe, Bruce, Vican, Laura, Ward-Thompson, Derek, van der Werf, Paul, White, Glenn J., Wilner, David, and Zuckerman, Ben
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Earth and Planetary Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
Debris discs are evidence of the ongoing destructive collisions between planetesimals, and their presence around stars also suggests that planets exist in these systems. In this paper, we present submillimetre images of the thermal emission from debris discs that formed the SCUBA-2 Observations of Nearby Stars (SONS) survey, one of seven legacy surveys undertaken on the James Clerk Maxwell telescope between 2012 and 2015. The overall results of the survey are presented in the form of 850 microns (and 450 microns, where possible) images and fluxes for the observed fields. Excess thermal emission, over that expected from the stellar photosphere, is detected around 49 stars out of the 100 observed fields. The discs are characterised in terms of their flux density, size (radial distribution of the dust) and derived dust properties from their spectral energy distributions. The results show discs over a range of sizes, typically 1-10 times the diameter of the Edgeworth-Kuiper Belt in our Solar System. The mass of a disc, for particles up to a few millimetres in size, is uniquely obtainable with submillimetre observations and this quantity is presented as a function of the host stars' age, showing a tentative decline in mass with age. Having doubled the number of imaged discs at submillimetre wavelengths from ground-based, single dish telescope observations, one of the key legacy products from the SONS survey is to provide a comprehensive target list to observe at high angular resolution using submillimetre/millimetre interferometers (e.g., ALMA, SMA)., Comment: 61 pages, 51 figures
- Published
- 2017
- Full Text
- View/download PDF
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