ABSTRACT
Discussing the particularly long gravitational microlensing event OGLE-2014-BLG-1186 with a time-scale tE ∼ 300 d, we present a methodology for identifying the nature of localised deviations ...from single-lens point-source light curves, which ensures that (1) the claimed signal is substantially above the noise floor, (2) the inferred properties are robustly determined and their estimation is not subject to confusion with systematic noise in the photometry, (3) alternative viable solutions within the model framework are not missed. Annual parallax and binarity could be separated and robustly measured from the wing and the peak data, respectively. We find matching model light curves that involve either a binary lens or a binary source, and discover hitherto unknown model ambiguities. Our binary-lens models indicate a planet of mass M2 = (45 ± 9) M⊕, orbiting a star of mass M1 = (0.35 ± 0.06) M⊙, located at a distance DL = (1.7 ± 0.3) kpc from Earth, whereas our binary-source models suggest a brown-dwarf lens of M = (0.046 ± 0.007) M⊙, located at a distance DL = (5.7 ± 0.9) kpc, with the source potentially being a (partially) eclipsing binary involving stars predicted to be of similar colour given the ratios between the luminosities and radii. Further observations might resolve the ambiguity in the interpretation in favour of either a lens or a source binary. We experienced that close binary source stars pose a challenge for claiming the detection of planets by microlensing in events where the source passes very close to the lens star hosting the planet.
We present high-precision photometry of three transits of the extrasolar planetary system WASP-2, obtained by defocusing the telescopes, and achieving scatters of between 0.42 and 0.73 mmag versus ...the best-fitting model. These data are modelled using the jktebop code, and taking into account the light from the recently discovered faint star close to the system. The physical properties of the WASP-2 system are derived using tabulated predictions from five different sets of stellar evolutionary models, allowing both statistical and systematic error bars to be specified. We find the mass and radius of the planet to be Mb= 0.846 ± 0.055 ± 0.023 MJup and Rb= 1.043 ± 0.029 ± 0.015RJup. It has a low equilibrium temperature of 1281 ± 21 K, in agreement with a recent finding that it does not have an atmospheric temperature inversion. The first of our transit data sets has a scatter of only 0.42 mmag with respect to the best-fitting light-curve model, which to our knowledge is a record for ground-based observations of a transiting extrasolar planetary system.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Terrestrial ecosystems in North America changed substantially during the Neogene. Previous authors have documented changes in plants and mammals but squamates have received comparatively little ...attention. Several Miocene lizard fossils were described previously from the Split Rock Formation (Wyoming), which was deposited just before or during the mid-Miocene Climatic Optimum (c. 18-14 Ma). I re-evaluate the identifications of some of the previously published fossil lizards from the Split Rock Formation and describe several new fossil lizards. I focus on the iguanians and revise the biogeographical and temporal context for the evolution of several clades. I establish a minimum age for crown Phrynosomatidae and describe the oldest known occurrence of Crotaphytidae. The fossils provide evidence of a relatively modern lizard fauna in central North America by ∼17.5 Ma and support a substantial turnover from the Eocene to the middle Miocene. I also describe a new taxon, Caeruleodentatus lovei, with a distinctive dentary morphology. The revised iguanian lizard fauna is more diverse than previously described. I discuss difficulties and considerations with using apomorphies to identify fossils, biogeographical biases that affect fossil identifications, and the previous and future use of fossils from the Split Rock Formation in divergence time analyses. I recommend that comparative samples used for identifying fossils should not be intentionally limited by biogeography or stratigraphy, and underscore the importance of topology selection when constructing an apomorphy-based diagnosis. While apomorphy-based diagnoses may decrease taxonomic resolution of fossil identifications, they do not necessarily decrease our capacity to interpret the phylogenetic, biogeographical or ecological significance of fossils.
http://zoobank.org/urn:lsid:zoobank.org:pub:F15984C6-144C-4110-A317-6714C6EEE295
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BFBNIB, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
ABSTRACT Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by ...exploring different regions of the lens plane and by directly measuring the "microlens parallax." We report the discovery of a 30-65MJ brown dwarf orbiting a K dwarf in the microlensing event OGLE-2015-BLG-1319. The system is located at a distance of ∼5 kpc toward the Galactic Bulge. The event was observed by several ground-based groups as well as by Spitzer and Swift, allowing a measurement of the physical properties. However, the event is still subject to an eight-fold degeneracy, in particular the well-known close-wide degeneracy, and thus the projected separation between the two lens components is either ∼0.25 au or ∼45 au. This is the first microlensing event observed by Swift, with the UVOT camera. We study the region of microlensing parameter space to which Swift is sensitive, finding that though Swift could not measure the microlens parallax with respect to ground-based observations for this event, it can be important for other events. Specifically, it is important for detecting nearby brown dwarfs and free-floating planets in high magnification events.
ABSTRACT
We present photometric observations of four transits in the WASP‐17 planetary system, obtained using telescope defocusing techniques and with scatters reaching 0.5 mmag per point. Our ...revised orbital period is 4.0 ± 0.6 s longer than previous measurements, a difference of 6.6σ, and does not support the published detections of orbital eccentricity in this system. We model the light curves using the jktebop code and calculate the physical properties of the system by recourse to five sets of theoretical stellar model predictions. The resulting planetary radius, Rb = 1.932 ± 0.052 ± 0.010 RJup (statistical and systematic errors, respectively), provides confirmation that WASP‐17 b is the largest planet currently known. All 14 planets with radii measured to be greater than 1.6 RJup are found around comparatively hot (Teff > 5900 K) and massive (MA > 1.15 M⊙) stars. Chromospheric activity indicators are available for eight of these stars, and all imply a low activity level. The planets have small or zero orbital eccentricities, so tidal effects struggle to explain their large radii. The observed dearth of large planets around small stars may be natural but could also be due to observational biases against deep transits, if these are mistakenly labelled as false positives and so not followed up.
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BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
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.
Glyptosaurinae is an extinct group of anguid lizards commonly found in the Cretaceous and Paleogene fossil record of North America and Eurasia. Glyptosaurines are well documented up until the middle ...Oligocene, but the temporal extent of the group was never constrained precisely. Here, I document the youngest known record of glyptosaurine lizards. I describe 10 fossils of the glyptosaurine Peltosaurus granulosus from the Monroe Creek and upper Sharps formations of Sharps Corner, South Dakota. The youngest known occurrence of Peltosaurus and Glyptosaurinae is between 27.4 and 26.4 Ma, based on a correlation of the magnetozone of the Monroe Creek Formation with chron C9n. Those dates are in the age range of a hypothesized middle–late Oligocene warming event. I review relevant morphological characteristics previously described for Peltosaurus and provide images of the holotypes of Peltosaurus abbotti and Peltosaurus granulosus, as well as two relatively complete specimens of Peltosaurus granulosus. I also establish an apomorphy of Peltosaurus on the frontal bone. Additionally, I correct an error in the literature pertaining to the original description of Peltosaurus.
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Accurate measurements of the physical characteristics of a large number of exoplanets are useful to strongly constrain theoretical models of planet formation and evolution, which lead to the large ...variety of exoplanets and planetary-system configurations that have been observed. We present a study of the planetary systems WASP-45 and WASP-46, both composed of a main-sequence star and a close-in hot Jupiter, based on 29 new high-quality light curves of transits events. In particular, one transit of WASP-45 b and four of WASP-46 b were simultaneously observed in four optical filters, while one transit of WASP-46 b was observed with the NTT obtaining a precision of 0.30 mmag with a cadence of roughly 3 min. We also obtained five new spectra of WASP-45 with the FEROS spectrograph. We improved by a factor of 4 the measurement of the radius of the planet WASP-45 b, and found that WASP-46 b is slightly less massive and smaller than previously reported. Both planets now have a more accurate measurement of the density (0.959 ± 0.077 ρJup instead of 0.64 ± 0.30 ρJup for WASP-45 b, and 1.103 ± 0.052 ρJup instead of 0.94 ± 0.11 ρJup for WASP-46 b). We tentatively detected radius variations with wavelength for both planets, in particular in the case of WASP-45 b we found a slightly larger absorption in the redder bands than in the bluer ones. No hints for the presence of an additional planetary companion in the two systems were found either from the photometric or radial velocity measurements.
We present the analysis of stellar binary microlensing event OGLE-2015-BLG-0060 based
on observations obtained from 13 different telescopes. Intensive coverage of the anomalous
parts of the light ...curve was achieved by automated follow-up observations from the robotic
telescopes of the Las Cumbres Observatory. We show that, for the first time, all main features of
an anomalous microlensing event are well covered by follow-up data, allowing us to estimate
the physical parameters of the lens. The strong detection of second-order effects in the event
light curve necessitates the inclusion of longer-baseline survey data in order to constrain
the parallax vector. We find that the event was most likely caused by a stellar binary-lens
with masses M ͙(1) = 0.87 ± 0.12M(☉) and M ͙(2)= 0.77 ± 0.11M(☉). The distance to the lensing
system is 6.41 ± 0.14 kpc and the projected separation between the two components is
13.85 ± 0.16 au. Alternative interpretations are also considered.
We present photometric observations of four transits in the WASP-17 planetary system, obtained using telescope defocusing techniques and with scatters reaching 0.5mmag per point. Our revised orbital ...period is 4.0 ± 0.6s longer than previous measurements, a difference of 6.6σ, and does not support the published detections of orbital eccentricity in this system. We model the light curves using the jktebop code and calculate the physical properties of the system by recourse to five sets of theoretical stellar model predictions. The resulting planetary radius, Rb = 1.932 ± 0.052 ± 0.010RJup (statistical and systematic errors, respectively), provides confirmation that WASP-17b is the largest planet currently known. All 14 planets with radii measured to be greater than 1.6RJup are found around comparatively hot (Teff > 5900K) and massive (MA > 1.15M) stars. Chromospheric activity indicators are available for eight of these stars, and all imply a low activity level. The planets have small or zero orbital eccentricities, so tidal effects struggle to explain their large radii. The observed dearth of large planets around small stars may be natural but could also be due to observational biases against deep transits, if these are mistakenly labelled as false positives and so not followed up. PUBLICATION ABSTRACT
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