773 research outputs found
The blue sky of GJ3470b: the atmosphere of a low-mass planet unveiled by ground-based photometry
GJ3470b is a rare example of a "hot Uranus" transiting exoplanet orbiting a
nearby M1.5 dwarf. It is of crucial interest for atmospheric studies because it
is one of the most inflated low-mass planets known, bridging the boundary
between "super-Earths" and Neptunian planets. We present two new ground-based
light curves of GJ3470b gathered by the LBC camera at the Large Binocular
Telescope. Simultaneous photometry in the ultraviolet (lambda_c = 357.5 nm) and
optical infrared (lambda_c = 963.5 nm) allowed us to detect a significant
change of the effective radius of GJ3470b as a function of wavelength. This can
be interpreted as a signature of scattering processes occurring in the
planetary atmosphere, which should be cloud-free and with a low mean molecular
weight. The unprecedented accuracy of our measurements demonstrates that the
photometric detection of Earth-sized planets around M dwarfs is achievable
using 8-10m size ground-based telescopes. We provide updated planetary
parameters, and a greatly improved orbital ephemeris for any forthcoming study
of this planet.Comment: 8 pages, 6 figures, 1 table; accepted for publication in A&
The M4 Core Project with HST - IV. Internal Kinematics from Accurate Radial Velocities of 2771 Cluster Members
We present a detailed study of the internal kinematics of the Galactic
Globular Cluster M 4 (NGC 6121), by deriving the radial velocities from 7250
spectra for 2771 stars distributed from the upper part of the Red Giant Branch
down to the Main Sequence. We describe new approaches to determine the
wavelength solution from day-time calibrations and to determine the radial
velocity drifts that can occur between calibration and science observations
when observing with the GIRAFFE spectrograph at VLT. Two techniques to
determine the radial velocity are compared, after a qualitative description of
their advantages with respect to other commonly used algorithm, and a new
approach to remove the sky contribution from the spectra obtained with
fibre-fed spectrograph and further improve the radial velocity precision is
presented. The average radial velocity of the cluster is km s with an average dispersion of km
s. Using the same dataset and the same statistical approach of previous
analyses, 20 additional binary candidates are found, for a total of 87
candidates. A new determination of the internal radial velocity dispersion as a
function of cluster distance is presented, resulting in a dispersion of
km s within 2 from the center of cluster and steadily
decreasing outward. We statistically confirm the small amplitude of the cluster
rotation, as suggested in the past by several authors. This new analysis
represents a significant improvement with respect to previous results in
literature and provides a fundamental observational input for the modeling of
the cluster dynamics.Comment: 17 pages, 17 figures. Accepted for publication in MNRAS on September
15, 201
Exploiting the transit timing capabilities of Ariel
The Transit Timing Variation (TTV) technique is a powerful dynamical tool to
measure exoplanetary masses by analysing transit light curves. We assessed the
transit timing performances of the Ariel Fine Guidance Sensors (FGS1/2) based
on the simulated light curve of a bright, 55 Cnc, and faint, K2-24,
planet-hosting star. We estimated through a Markov-Chain Monte-Carlo analysis
the transit time uncertainty at the nominal cadence of 1 second and, as a
comparison, at a 30 and 60-s cadence. We found that at the nominal cadence
Ariel will be able to measure the transit time with a precision of about 12s
and 34s, for a star as bright as 55 Cnc and K2-24, respectively. We then ran
dynamical simulations, also including the Ariel timing errors, and we found an
improvement on the measurement of planetary masses of about in a
K2-24-like planetary system through TTVs. We also simulated the conditions that
allow us to detect the TTV signal induced by an hypothetical external perturber
within the mass range between Earth and Neptune using 10 transit light curves
by Ariel.Comment: 15 pages, 8 figures, accepted for publication in Experimental
Astronomy - Ariel Special Issu
Large Binocular Telescope view of the atmosphere of GJ1214b
The atmospheric composition and vertical structure of the super-Earth GJ1214b
has been a subject of debate since its discovery in 2009. Recent studies have
indicated that high-altitude clouds might mask the lower layers. However, some
data points that were gathered at different times and facilities do not fit
this picture, probably because of a combination of stellar activity and
systematic errors. We observed two transits of GJ1214b with the Large Binocular
Camera, the dual-channel camera at the Large Binocular Telescope. For the first
time, we simultaneously measured the relative planetary radius
at blue and red optical wavelengths (), thus
constraining the Rayleigh scattering on GJ1214b after correcting for stellar
activity effects. To the same purpose, a long-term photometric follow-up of the
host star was carried out with WiFSIP at STELLA, revealing a rotational period
that is significantly longer than previously reported. Our new unbiased
estimates of yield a flat transmission spectrum extending to shorter
wavelengths, thus confirming the cloudy atmosphere scenario for GJ1214b.Comment: 11 pages, 5 figures, 3 tables. Published in A&A. Minor changes to
reflect the published versio
TASTE IV. Refining ephemeris and orbital parameters for HAT-P-20b and WASP-1b
We present four new light curves of transiting exoplanets WASP-1b and
HAT-P-20b, observed within the TASTE (The Asiago Search for Transit timing
variations of Exoplanets) project. We re-analyzed light curves from the
literature in a homogeneous way, calculating a refined ephemeris and
orbital-physical parameters for both objects. WASP-1b does not show any
significant Transit Timing Variation signal at the 120 s-level. As for
HAT-P-20b, we detected a deviation from our re-estimated linear ephemeris that
could be ascribed to the presence of a perturber or, more probably, to a
previously unnoticed high level of stellar activity. The rotational period of
HAT-P-20 A we obtained from archival data (P_rot ~ 14.5 days), combined with
its optical variability and strong emission of CaII H&K lines, is consistent
with a young stellar age (< 1 Gyr) and support the hypothesis that stellar
activity may be responsible of the measured deviations of the transit times.Comment: 7 pages, 4 figures, 3 tables, accepted to Astronomische Nachrichte
Practice parameters for the treatment of colonic diverticular disease: Italian Society of Colon and Rectal Surgery (SICCR) guidelines
The mission of the Italian Society of Colorectal Surgery (SICCR) is to optimize patient care. Providing evidence-based practice guidelines is therefore of key importance. About the present report it concernes the SICCR practice guidelines for the diagnosis and treatment of diverticular disease of the colon. The guidelines are not intended to define the sole standard of care but to provide evidence-based recommendations regarding the available therapeutic options
Ocular Refraction at Birth and Its Development During the First Year of Life in a Large Cohort of Babies in a Single Center in Northern Italy
The purpose of this study was to investigate refraction at birth and during the first year of life in a large cohort of babies born in a single center in Northern Italy. We also aimed to analyze refractive errors in relation to the gestational age at birth. An observational ophthalmological assessment was performed within 24 h of birth on 12,427 newborns. Refraction was examined using streak retinoscopy after the administration of tropicamide (1%). Values in the range of between +0.50 ≤ D ≤ +4.00 were defined as physiological refraction at birth. Newborns with refraction values outside of the physiological range were followed up during the first year of life. Comparative analyses were conducted in a subgroup of babies with known gestational ages. The following distribution of refraction at birth was recorded: 88.03% of the babies had physiological refraction, 5.03% had moderate hyperopia, 2.14% had severe hyperopia, 3.4%, had emmetropia, 0.45%, had myopia, 0.94% had astigmatism, and 0.01% had anisometropia. By the end of the first year of life, we observed reductions in hyperopia and astigmatism, and stabilization of myopia. Preterm babies had a four-fold higher risk of congenital myopia and a three-fold higher risk of congenital emmetropia as compared to term babies. Refraction profiles obtained at birth changed during the first year of life, leading to a normalization of the refraction values. Gestational age at birth affected the incidence of refractive errors and amblyopia
High-precision astrometry with VVV. I. An independent reduction pipeline for VIRCAM@VISTA
We present a new reduction pipeline for the VIRCAM@VISTA detector and
describe the method developed to obtain high-precision astrometry with the
VISTA Variables in the V\'ia L\'actea (VVV) data set. We derive an accurate
geometric-distortion correction using as calibration field the globular cluster
NGC 5139, and showed that we are able to reach a relative astrometric precision
of about 8 mas per coordinate per exposure for well-measured stars over a field
of view of more than 1 square degree. This geometric-distortion correction is
made available to the community. As a test bed, we chose a field centered
around the globular cluster NGC 6656 from the VVV archive and computed proper
motions for the stars within. With 45 epochs spread over four years, we show
that we are able to achieve a precision of 1.4 mas/yr and to isolate each
population observed in the field (cluster, Bulge and Disk) using proper
motions. We used proper-motion-selected field stars to measure the motion
difference between Galactic disk and bulge stars. Our proper-motion
measurements are consistent with UCAC4 and PPMXL, though our errors are much
smaller. Models have still difficulties in reproducing the observations in this
highly-reddened Galactic regions.Comment: 11 pages, 10 figures (some in low res), 1 table. Accepted for
publication in MNRAS on March 25, 2015. The FORTRAN routine will be soon made
available at http://groups.dfa.unipd.it/ESPG/ , and via email request to the
first autho
Openness in Teachers' Digital Competence Frameworks: Looking for the Open Educator
There has been a wide variety of definitions of digital competence, from early narrow and technology-focused explanations to more recent attempts , such as the one by Ferrari (2013), who describes it as a complex concept encompassing a wide set of skills, attitudes and knowledge when performing tasks with Information and Communication Technologies (ICT). Furthermore, there have been various different attempts to describe teachers’ digital competence, as the literature review by McGarr and McDonagh (2019) demonstrates. These authors evidence that models either depict teachers’ digital competence in diverse taxonomies of areas and dimensions, or as a hierarchical and progressive evolution from low to high levels of awareness and ability. They observe that openness does not have a presence in most of the taxonomic models and thus they propose openness as a dimension of their four-part model, under the label of attitudes. In this current work, we analyse international and national teachers’ digital competence frameworks and review whether openness has been included in them, and, if so, how it is described. In the case of frameworks that offer a model of increasing performance, we observe the levels at which open-related concepts appear. An initial review of the frameworks by the European Commission, UNESCO, ISTE (US) and INTEF (Spain) indicates that ‘openness’ typically does not constitute a dimension in itself and tends to appear at intermediate and high levels of teachers’ digital competence, except from the UNESCO framework, where access to OER (Open Educational Resources) is present already at the lowest level. In this paper we reflect on the need for international and national frameworks of teacher professional development to boost openness: in particular, for open educational practices to be included at lower levels of teachers’ pre-service and in-service professional education. We argue that becoming an open educator requires both the development of the dispositions associated with reflective practice and the confidence to challenge neo-liberal educational assumptions in order to embrace participatory, equitable and open educational practices from the early stages of the development of teachers’ digital competence
Broad-band spectrophotometry of the hot Jupiter HAT-P-12b from the near-UV to the near-IR
The detection of trends or gradients in the transmission spectrum of
extrasolar planets is possible with observations at very low spectral
resolution. Transit measurements of sufficient accuracy using selected
broad-band filters allow for an initial characterization of the atmosphere of
the planet. We obtained time series photometry of 20 transit events and
analyzed them homogeneously, along with eight light curves obtained from the
literature. In total, the light curves span a range from 0.35 to 1.25 microns.
During two observing seasons over four months each, we monitored the host star
to constrain the potential influence of starspots on the derived transit
parameters. We rule out the presence of a Rayleigh slope extending over the
entire optical wavelength range, a flat spectrum is favored for HAT-P-12b with
respect to a cloud-free atmosphere model spectrum. A potential cause of such
gray absorption is the presence of a cloud layer at the probed latitudes.
Furthermore, in this work we refine the transit parameters, the ephemeris and
perform a TTV analysis in which we found no indication for an unseen companion.
The host star showed a mild non-periodic variability of up to 1%. However, no
stellar rotation period could be detected to high confidence.Comment: 13 pages, 6 figures, Accepted for publication in A&
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