238 research outputs found
Na I and H absorption features in the atmosphere of MASCARA-2b/KELT-20b
We have used the HARPS-North high resolution spectrograph (=115
000) at TNG to observe one transit of the highly irradiated planet
MASCARA-2b/KELT-20b. Using only one transit observation, we are able to clearly
resolve the spectral features of the atomic sodium (Na I) doublet and the
H line in its atmosphere, measuring absorption depths of
0.170.03 and 0.590.08 for a 0.75 passband,
respectively. These absorptions are corroborated with the transmission measured
from their respective transmission light curves, which show a large
Rossiter-McLaughlin effect. In case of H, this absorption corresponds
to an effective radius of =1.200.04. While the S/N of the
final transmission spectrum is not sufficient to adjust different temperature
profiles to the lines, we find that higher temperatures than the equilibrium
are needed to explain the lines contrast. Particularly, we find that the Na I
lines core require a temperature of T=4210180K and that H requires
T=4330520K. MASCARA-2b, like other planets orbiting A-type stars, receives
a large amount of UV energy from its host star. This energy excites the atomic
hydrogen and produces H absorption, leading to the expansion and
abrasion of the atmosphere. The study of other Balmer lines in the transmission
spectrum would allow the determination of the atmospheric temperature profile
and the calculation of the lifetime of the atmosphere. In the case of
MASCARA-2b, residual features are observed in the H and H lines,
but they are not statistically significant. More transit observations are
needed to confirm our findings in Na I and H, and to build up enough
S/N to explore the presence of H and H planetary absorptions.Comment: 14 pages, 12 figure
Data calibration for the MASCARA and bRing instruments
Aims: MASCARA and bRing are photometric surveys designed to detect
variability caused by exoplanets in stars with . Such variability
signals are typically small and require an accurate calibration algorithm,
tailored to the survey, in order to be detected. This paper presents the
methods developed to calibrate the raw photometry of the MASCARA and bRing
stations and characterizes the performance of the methods and instruments.
Methods: For the primary calibration a modified version of the coarse
decorrelation algorithm is used, which corrects for the extinction due to the
earth's atmosphere, the camera transmission, and intrapixel variations.
Residual trends are removed from the light curves of individual stars using
empirical secondary calibration methods. In order to optimize these methods, as
well as characterize the performance of the instruments, transit signals were
injected in the data. Results: After optimal calibration an RMS scatter of 10
mmag at is achieved in the light curves. By injecting transit
signals with periods between one and five days in the MASCARA data obtained by
the La Palma station over the course of one year, we demonstrate that MASCARA
La Palma is able to recover 84.0, 60.5 and 20.7% of signals with depths of 2, 1
and 0.5% respectively, with a strong dependency on the observed declination,
recovering 65.4% of all transit signals at versus 35.8% at
. Using the full three years of data obtained by MASCARA La
Palma to date, similar recovery rates are extended to periods up to ten days.
We derive a preliminary occurrence rate for hot Jupiters around A-stars of , knowing that many hot Jupiters are still overlooked. In the era of
TESS, MASCARA and bRing will provide an interesting synergy for finding
long-period ( days) transiting gas-giant planets around the brightest
stars.Comment: 18 pages, 17 figures, accepted for publication in A&
bRing: An observatory dedicated to monitoring the Pictoris b Hill sphere transit
Aims. We describe the design and first light observations from the
Pictoris b Ring ("bRing") project. The primary goal is to detect photometric
variability from the young star Pictoris due to circumplanetary
material surrounding the directly imaged young extrasolar gas giant planet
\bpb. Methods. Over a nine month period centred on September 2017, the Hill
sphere of the planet will cross in front of the star, providing a unique
opportunity to directly probe the circumplanetary environment of a directly
imaged planet through photometric and spectroscopic variations. We have built
and installed the first of two bRing monitoring stations (one in South Africa
and the other in Australia) that will measure the flux of Pictoris,
with a photometric precision of over 5 minutes. Each station uses two
wide field cameras to cover the declination of the star at all elevations.
Detection of photometric fluctuations will trigger spectroscopic observations
with large aperture telescopes in order to determine the gas and dust
composition in a system at the end of the planet-forming era. Results. The
first three months of operation demonstrate that bRing can obtain better than
0.5\% photometry on Pictoris in five minutes and is sensitive to
nightly trends enabling the detection of any transiting material within the
Hill sphere of the exoplanet
MASCARA-2 b: A hot Jupiter transiting the A-star HD185603
In this paper we present MASCARA-2 b, a hot Jupiter transiting the
A2 star HD 185603. Since early 2015, MASCARA has taken more than 1.6 million
flux measurements of the star, corresponding to a total of almost 3000 hours of
observations, revealing a periodic dimming in the flux with a depth of .
Photometric follow-up observations were performed with the NITES and IAC80
telescopes and spectroscopic measurements were obtained with the Hertzsprung
SONG telescope. We find MASCARA-2 b orbits HD 185603 with a period of
at a distance of , has a radius of and place a
upper limit on the mass of . HD 185603 is a
rapidly rotating early-type star with an effective temperature of
and a mass and radius of
, , respectively. Contrary
to most other hot Jupiters transiting early-type stars, the projected planet
orbital axis and stellar spin axis are found to be aligned with . The brightness of the host star and the high equilibrium
temperature, , of MASCARA-2 b make it a suitable target for
atmospheric studies from the ground and space. Of particular interest is the
detection of TiO, which has recently been detected in the similarly hot planets
WASP-33 b and WASP-19 b.Comment: 8 pages, 4 figures, Accepted for publication in A&
Furrow and Ridge Soil Nitrogen Mineralization in a Surface Irrigated Artichoke Field
[EN] Quantitative knowledge of soil organic nitrogen net mineralization (NNM)
in field conditions is crucial to optimize N fertilization of crops. In a field
fertilization trial of artichokes 48 PE tubes were inserted to 20 cm depth in the soil
in plant row and irrigation furrows and soil samples were periodically taken
during two and a half months to determine NNM. A parallel essay with disturbed
samples from the same procedence was carried out in the laboratory at 25ºC and
10 kPa soil water tension. Soil sample position (ridge and furrow) did not
significantly determined NNM in the laboratory essay. Although NNM (obtained
from laboratory incubation and corrected to field soil temperature and moisture
monitored during the experimental period) overpredicted measured field NNM,
matching of both was better than those reported in other studies. NNM rate for the
76 days period of incubation predicted from lab data was 22.9 kg N/ ha x 0.1 m
while corresponding field values corrected by Br- or Cl- mass balance were 10%
and 20% lower respectively in ridge position and under 40% lower by either
method in furrow position.The research reported in this paper was supported by a fund from CICYT-INIA
(project RTA01-117-C2-2)Lidón, A.; Bautista, I.; De La Iglesia, F.; Oliver Talens, J.; Llorca, R.; Cruz-Romero, G. (2006). Furrow and Ridge Soil Nitrogen Mineralization in a Surface Irrigated Artichoke Field. Acta Horticulturae. (700):71-74. https://doi.org/10.17660/ActaHortic.2006.700.7S717470
The capacity building of the Peoples Institution to close the sustainability gap in the child survival project in Bangladesh
Structural basis for distinctive recognition of fibrinogen γC peptide by the platelet integrin αIIbβ3
Hemostasis and thrombosis (blood clotting) involve fibrinogen binding to integrin αIIbβ3 on platelets, resulting in platelet aggregation. αvβ3 binds fibrinogen via an Arg-Asp-Gly (RGD) motif in fibrinogen's α subunit. αIIbβ3 also binds to fibrinogen; however, it does so via an unstructured RGD-lacking C-terminal region of the γ subunit (γC peptide). These distinct modes of fibrinogen binding enable αIIbβ3 and αvβ3 to function cooperatively in hemostasis. In this study, crystal structures reveal the integrin αIIbβ3–γC peptide interface, and, for comparison, integrin αIIbβ3 bound to a lamprey γC primordial RGD motif. Compared with RGD, the GAKQAGDV motif in γC adopts a different backbone configuration and binds over a more extended region. The integrin metal ion–dependent adhesion site (MIDAS) Mg2+ ion binds the γC Asp side chain. The adjacent to MIDAS (ADMIDAS) Ca2+ ion binds the γC C terminus, revealing a contribution for ADMIDAS in ligand binding. Structural data from this natively disordered γC peptide enhances our understanding of the involvement of γC peptide and integrin αIIbβ3 in hemostasis and thrombosis
Epigenetic variation during the adult lifespan: cross-sectional and longitudinal data on monozygotic twin pairs
The accumulation of epigenetic changes was proposed to contribute to the age-related increase in the risk of most common diseases. In this study on 230 monozygotic twin pairs (MZ pairs), aged 18-89years, we investigated the occurrence of epigenetic changes over the adult lifespan. Using mass spectrometry, we investigated variation in global (LINE1) DNA methylation and in DNA methylation at INS, KCNQ1OT1, IGF2, GNASAS, ABCA1, LEP, and CRH, candidate loci for common diseases. Except for KCNQ1OT1, interindividual variation in locus-specific DNA methylation was larger in old individuals than in young individuals, ranging from 1.2-fold larger at ABCA1 (P=0.010) to 1.6-fold larger at INS (P=3.7×1
Bemestingsadvies
Deze uitgave geeft de meest actuele versie van de officiële bemestingsadviezen. De "Adviesbasis voor de bemesting van grasland en voedergewassen" is bedoeld voor laboratoria voor grondonderzoek ten behoeve van hun bemestingsadvisering, voorlichtingsdiensten, handel, industrie, onderwijs en onderzoek. Daarnaast is hij ook bedoeld voor de praktische boer die behoefte heeft aan meer achtergrondinformatie omtrent bemesting. De opgenomen bemestingsadviezen zijn vastgesteld door de Commissie Bemesting Grasland en Voedergewassen. Deze commissie is ingesteld door LTO-Nederland en bestaat uit vertegenwoordigers van onderzoek, voorlichting en bedrijfsleven
Discovery of δ Scuti Pulsations in the Young Hybrid Debris Disk Star HD 156623
The bRing robotic observatory network was built to search for circumplanetary material within the transiting Hill
sphere of the exoplanet β Pic b across its bright host star β Pic. During the bRing survey of β Pic, it simultaneously
monitored the brightnesses of thousands of bright stars in the southern sky (V ; 4–8, δ −30°). In this work, we
announce the discovery of δ Scuti pulsations in the A-type star HD 156623 using bRing data. HD 156623 is
notable as it is a well-studied young star with a dusty and gas-rich debris disk, previously detected using ALMA.
We present the observational results on the pulsation periods and amplitudes for HD 156623, discuss its
evolutionary status, and provide further constraints on its nature and age. We find strong evidence of frequency
regularity and grouping. We do not find evidence of frequency, amplitude, or phase modulation for any of the
frequencies over the course of the observations. We show that HD 156623 is consistent with other hot and highfrequency pre-main sequence and early zero-age main sequence (ZAMS) δ Scutis as predicted by theoretical
models and corresponding evolutionary tracks, although we observe that HD 156623 lies hotter than the theoretical
blue edge of the classical instability strip. This, coupled with our characterization and Sco–Cen membership
analyses, suggests that the star is most likely an outlying ZAMS member of the ∼16 Myr Upper Centaurus-Lupus
subgroup of the Sco–Cen associatio
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