112 research outputs found
COVID-19 catalyst: emergent pedagogies and a DIAgram framework
The global COVID-19 pandemic has delivered extraordinary challenges across geographies as well as practices, and clearly academia has not been spared. While the events of 2020 and 2021 have revealed some limits to teaching in the ‘old (pre-pandemic) normal’, technology-supported pedagogies have been emerging for several years. This pandemic has been a potent catalyst, not only for ad-hoc adaptation, but potentially for long-term change and improvement. The ‘old normal’ is now long passed, and approaches to learning and teaching continue to explore new ground. This article draws on the work of Built Environments Learning + Teaching (BEL+T), an academic group within the Faculty of Architecture, Building and Planning at the University of Melbourne. The BEL+T group applies creative problem-solving and design-led approaches, evidence-based research methodologies and project-focused consultancy to improve teaching quality and student engagement in built environment disciplines. The following sections introduce a learning design framework – the Delivery, Interaction, Assessment (DIA) framework – which was developed by BEL+T as a tool to communicate with and support staff throughout 2020 and 2021, and continues to be used to support teaching efforts. The translation of the elements of the DIA framework and its related ‘DIAgram’ to specific learning activities are presented in the following sections ‘on the (virtual) ground’. Some emergent pedagogies for virtual learning environments (VLEs) are outlined, exploring relationships between students, teachers, objects, sites and VLEs for learning, alongside implications for teacher presence and performance online. These key factors have influenced online approaches both before and since the onset of the pandemic. They deliver implications for emergent hybrid approaches such as dual delivery and blended synchronous learning, which are in turn driven by the needs of a still-distributed student cohort and the challenges of ongoing unpredictability
The Transiting System GJ1214: High-Precision Defocused Transit Observations and a Search for Evidence of Transit Timing Variation
Aims: We present 11 high-precision photometric transit observations of the
transiting super-Earth planet GJ1214b. Combining these data with observations
from other authors, we investigate the ephemeris for possible signs of transit
timing variations (TTVs) using a Bayesian approach.
Methods: The observations were obtained using telescope-defocusing
techniques, and achieve a high precision with random errors in the photometry
as low as 1mmag per point. To investigate the possibility of TTVs in the light
curve, we calculate the overall probability of a TTV signal using Bayesian
methods.
Results: The observations are used to determine the photometric parameters
and the physical properties of the GJ1214 system. Our results are in good
agreement with published values. Individual times of mid-transit are measured
with uncertainties as low as 10s, allowing us to reduce the uncertainty in the
orbital period by a factor of two.
Conclusions: A Bayesian analysis reveals that it is highly improbable that
the observed transit times is explained by TTV, when compared with the simpler
alternative of a linear ephemeris.Comment: Submitted to A&
A pair of temperate sub-Neptunes transiting the star EPIC 212737443
We report the validation of a new planetary system around the K3 star EPIC 212737443 using a combination of K2 photometry, follow-up high resolution imaging and spectroscopy. The system consists of two sub-Neptune sized transiting planets with radii of 2.6R⊕, and 2.7R⊕, with orbital periods of 13.6 days and 65.5 days, equilibrium temperatures of 536 K and 316 K respectively. In the context of validated K2 systems, the outer planet has the longest precisely measured orbital period, as well as the lowest equilibrium temperature for a planet orbiting a star of spectral type earlier than M. The two planets in this system have a mutual Hill radius of ΔRH = 36, larger than most other known transiting multi-planet systems, suggesting the existence of another (possibly non-transiting) planet, or that the system is not maximally packed
The GAPS Programme with HARPS-N at TNG VIII: Observations of the Rossiter-McLaughlin effect and characterisation of the transiting planetary systems HAT-P-36 and WASP-11/HAT-P-10
We determine the true and the projected obliquity of HAT-P-36 and
WASP-11/HAT-P-10 systems, respectively, which are both composed of a relatively
cool star and a hot-Jupiter planet. Thanks to the high-resolution spectrograph
HARPS-N, we observed the Rossiter-McLaughlin effect for both the systems by
acquiring precise radial-velocity measurements during planetary transit events.
We also present photometric observations comprising six light curves covering
five transit events, obtained using three medium-class telescopes and the
telescope-defocussing technique. One transit of WASP-11/HAT-P-10 was followed
simultaneously from two observatories. The three transit light curves of
HAT-P-36b show anomalies that are attributable to starspot complexes on the
surface of the parent star, in agreement with the analysis of its spectra that
indicate a moderate activity. By analysing the complete HATNet data set of
HAT-P-36, we estimated the stellar rotation period by detecting a periodic
photometric modulation in the light curve caused by star spots, obtaining
Prot=15.3 days, which implies that the inclination of the stellar rotational
axis with respect to the line of sight is 65 degree. We used the new
spectroscopic and photometric data to revise the main physical parameters and
measure the sky-projected misalignment angle of the two systems. We found
\lambda=-14 degree for HAT-P-36 and \lambda=7 degree for WASP-11/HAT-P-10,
indicating in both cases a good spin-orbit alignment. In the case of HAT-P-36,
we also measured its real obliquity, which turned out to be 25 degrees.Comment: 18 pages, 14 figure
High-precision photometry by telescope defocussing - VI. WASP-24, WASP-25 and WASP-26
The research leading to these results has received funding from the European Community's Seventh Framework Programme (FP7/2007-2013/) under grant agreement nos. 229517 and 268421. This publication was supported by grants NPRP 09-476-1-078 and NPRP X-019-1-006 from Qatar National Research Fund (a member of Qatar Foundation). TCH acknowledges financial support from the Korea Research Council for Fundamental Science and Technology (KRCF) through the Young Research Scientist Fellowship Programme and is supported by the KASI (Korea Astronomy and Space Science Institute) grant 2012-1-410-02/2013-9-400-00. SG, XW and XF acknowledge the support from NSFC under the grant no. 10873031. The research is supported by the ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) funded by the European Research Council (grant agreement no. 267864). DR, YD, AE, FF (ARC), OW (FNRS research fellow) and J Surdej acknowledge support from the Communauté française de Belgique – Actions de recherche concertées – Académie Wallonie-Europe.We present time series photometric observations of 13 transits in the planetary systems WASP-24, WASP-25 and WASP-26. All three systems have orbital obliquity measurements, WASP-24 and WASP-26 have been observed with Spitzer, and WASP-25 was previously comparatively neglected. Our light curves were obtained using the telescope-defocussing method and have scatters of 0.5–1.2 mmag relative to their best-fitting geometric models. We use these data to measure the physical properties and orbital ephemerides of the systems to high precision, finding that our improved measurements are in good agreement with previous studies. High-resolution Lucky Imaging observations of all three targets show no evidence for faint stars close enough to contaminate our photometry. We confirm the eclipsing nature of the star closest to WASP-24 and present the detection of a detached eclipsing binary within 4.25 arcmin of WASP-26.Publisher PDFPeer reviewe
Characterizing Low-Mass Binaries From Observation of Long Time-scale Caustic-crossing Gravitational Microlensing Events
Despite astrophysical importance of binary star systems, detections are
limited to those located in small ranges of separations, distances, and masses
and thus it is necessary to use a variety of observational techniques for a
complete view of stellar multiplicity across a broad range of physical
parameters. In this paper, we report the detections and measurements of 2
binaries discovered from observations of microlensing events MOA-2011-BLG-090
and OGLE-2011-BLG-0417. Determinations of the binary masses are possible by
simultaneously measuring the Einstein radius and the lens parallax. The
measured masses of the binary components are 0.43 and 0.39
for MOA-2011-BLG-090 and 0.57 and 0.17 for
OGLE-2011-BLG-0417 and thus both lens components of MOA-2011-BLG-090 and one
component of OGLE-2011-BLG-0417 are M dwarfs, demonstrating the usefulness of
microlensing in detecting binaries composed of low-mass components. From
modeling of the light curves considering full Keplerian motion of the lens, we
also measure the orbital parameters of the binaries. The blended light of
OGLE-2011-BLG-0417 comes very likely from the lens itself, making it possible
to check the microlensing orbital solution by follow-up radial-velocity
observation. For both events, the caustic-crossing parts of the light curves,
which are critical for determining the physical lens parameters, were resolved
by high-cadence survey observations and thus it is expected that the number of
microlensing binaries with measured physical parameters will increase in the
future.Comment: 8 pages, 5 figures, 4 table
Rotation of planet-harbouring stars
The rotation rate of a star has important implications for the detectability,
characterisation and stability of any planets that may be orbiting it. This
chapter gives a brief overview of stellar rotation before describing the
methods used to measure the rotation periods of planet host stars, the factors
affecting the evolution of a star's rotation rate, stellar age estimates based
on rotation, and an overview of the observed trends in the rotation properties
of stars with planets.Comment: 16 pages, 4 figures: Invited review to appear in 'Handbook of
Exoplanets', Springer Reference Works, edited by Hans J. Deeg and Juan
Antonio Belmont
High-precision photometry by telescope defocusing - V.WASP-15 and WASP-16
We present newphotometric observations ofWASP-15 andWASP-16, two transiting extrasolar planetary systems with measured orbital obliquities but without photometric follow-up since their discovery papers. Our new data for WASP-15 comprise observations of one transit simultaneously in four optical passbands using GROND on the MPG/European Southern Observatory (ESO) 2.2 m telescope, plus coverage of half a transit from DFOSC on the Danish 1.54 m telescope, both at ESO La Silla. ForWASP-16 we present observations of fourcomplete transits, all from the Danish telescope. We use these new data to refine the measured physical properties and orbital ephemerides of the two systems. Whilst our results are close to the originally determined values forWASP-15, we find that the star and planet in theWASP-16 system are both larger and less massive than previously thought. ©2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
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