261 research outputs found
CoBiToM Project -- II: Evolution of contact binary systems close to the orbital period cut-off
Ultra-short orbital period contact binaries (Porb < 0.26 d) host some of the
smallest and least massive stars. These systems are faint and rare, and it is
believed that they have reached a contact configuration after several Gyrs of
evolution via angular momentum loss, mass transfer and mass loss through
stellar wind processes. This study is conducted in the frame of Contact
Binaries Towards Merging (CoBiToM) Project and presents the results from light
curve and orbital analysis of 30 ultra-short orbital period contact binaries,
with the aim to investigate the possibility of them being red nova progenitors,
eventually producing merger events. Approximately half of the systems exhibit
orbital period modulations, as a result of mass transfer or mass loss
processes. Although they are in contact, their fill-out factor is low (less
than 30 per cent), while their mass ratio is larger than the one in longer
period contact binaries. The present study investigates the orbital stability
of these systems and examines their physical and orbital parameters in
comparison to those of the entire sample of known and well-studied contact
binaries, based on combined spectroscopic and photometric analysis. It is found
that ultra-short orbital period contact binaries have very stable orbits, while
very often additional components are gravitationally bound in wide orbits
around the central binary system. We confirmed that the evolution of such
systems is very slow, which explains why the components of ultra-short orbital
period systems are still Main Sequence stars after several Gyrs of evolution
NELIOTA: The wide-field, high-cadence lunar monitoring system at the prime focus of the Kryoneri telescope
We present the technical specifications and first results of the ESA-funded,
lunar monitoring project "NELIOTA" (NEO Lunar Impacts and Optical TrAnsients)
at the National Observatory of Athens, which aims to determine the
size-frequency distribution of small Near-Earth Objects (NEOs) via detection of
impact flashes on the surface of the Moon. For the purposes of this project a
twin camera instrument was specially designed and installed at the 1.2 m
Kryoneri telescope utilizing the fast-frame capabilities of scientific
Complementary Metal-Oxide Semiconductor detectors (sCMOS). The system provides
a wide field-of-view (17.0' 14.4') and simultaneous observations in
two photometric bands (R and I), reaching limiting magnitudes of 18.7 mag in 10
sec in both bands at a 2.5 signal-to-noise level. This makes it a unique
instrument that can be used for the detection of NEO impacts on the Moon, as
well as for any astronomy projects that demand high-cadence multicolor
observations. The wide field-of-view ensures that a large portion of the Moon
is observed, while the simultaneous, high-cadence, monitoring in two
photometric bands makes possible, for the first time, the determination of the
temperatures of the impacts on the Moon's surface and the validation of the
impact flashes from a single site. Considering the varying background level on
the Moon's surface we demonstrate that the NELIOTA system can detect NEO impact
flashes at a 2.5 signal-to-noise level of ~12.4 mag in the I-band and R-band
for observations made at low lunar phases ~0.1. We report 31 NEO impact flashes
detected during the first year of the NELIOTA campaign. The faintest flash was
at 11.24 mag in the R-band (about two magnitudes fainter than ever observed
before) at lunar phase 0.32. Our observations suggest a detection rate of events .Comment: Accepted for publication in A&
CoBiToM Project - II: Evolution of contact binary systems close to the orbital period cut-off
Ultra-short orbital period contact binaries (Porb </p
Towards ensemble asteroseismology of the young open clusters Chi Persei and NGC 6910
As a result of the variability survey in Chi Persei and NGC6910, the number
of Beta Cep stars that are members of these two open clusters is increased to
twenty stars, nine in NGC6910 and eleven in Chi Persei. We compare pulsational
properties, in particular the frequency spectra, of Beta Cep stars in both
clusters and explain the differences in terms of the global parameters of the
clusters. We also indicate that the more complicated pattern of the variability
among B type stars in Chi Persei is very likely caused by higher rotational
velocities of stars in this cluster. We conclude that the sample of pulsating
stars in the two open clusters constitutes a very good starting point for the
ensemble asteroseismology of Beta Cep-type stars and maybe also for other
B-type pulsators.Comment: 4 pages, Astronomische Nachrichten, HELAS IV Conference, Arecife,
Lanzarote, Feb 2010, submitte
Observational detection of eight mutual eclipses and occultations between the satellites of Uranus
We carried out observations, with five different instruments ranging in
aperture from 0.4m to 10m, of the satellites of Uranus during that planet's
2007 Equinox. Our observations covered specific intervals of time when mutual
eclipses and occultations were predicted.
The observations were carried out in the near-infrared part of the spectrum
to mitigate the glare from the planet. Frames were acquired at rates > 1/min.
Following modelling and subtraction of the planetary source from these frames,
differential aperture photometry was carried out on the satellite pairs
involved in the predicted events. In all cases but one, nearby bright
satellites were used as reference sources.
We have obtained fifteen individual lightcurves, eight of which show a clear
drop in the flux from the satellite pair, indicating that a mutual event took
place. Three of these involve the faint satellite Miranda. All eight
lightcurves were model-fitted to yield best estimates of the time of maximum
flux drop and the impact parameter. In three cases best-fit albedo ratios were
also derived. We used these estimates to generate intersatellite astrometric
positions with typical formal uncertainties of <0.01 arcsec, several times
better than conventional astrometry of these satellites. The statistics of our
estimated event midtimes show a systematic lag, with the observations later
than predictions. In addition, lightcurves of two partial eclipses of Miranda
show no statistically significant evidence of a light drop, at variance with
the predictions. These indicate that new information about the Uranian
satellite system is contained in observations of mutual events acquired here
and by other groups.Comment: 8 pages, 3 figures, accepted for publication in Astronomy and
Astrophysics Uses aa style packag
Constipation-Predominant Irritable Bowel Syndrome Associated to Hyperprolactinemia
Irritable bowel syndrome (IBS) is considered to be a physical disorder that mainly affects the bowel and is clinically characterized by lower abdominal pain or discomfort, diarrhea, constipation (or alternating diarrhea/constipation), gas, bloating, and nausea. According to recent studies, it appears that there is an association with increased prolactin levels in patients suffering from IBS. We report a rare case of regression of IBS symptoms (constipation type) in a 16-year-old female adolescent after receiving cabergoline for treating hyperprolactinemia due to pituitary macroadenoma. Our hypothesis is that increased prolactin levels, for instance due to a pituitary adenoma, may suppress prolactin-releasing peptide release and lead to a reverse feedback interaction, consequently resulting in oversecretion of cholecystokinin, inducing the development of IBS
Accurate Treatment of Large Supramolecular Complexes by Double-Hybrid Density Functionals Coupled with Nonlocal van der Waals Corrections
In this work, we present a thorough assessment of the performance of some representative double-hybrid density functionals (revPBE0-DH-NL and B2PLYP-NL) as well as their parent hybrid and GGA counterparts, in combination with the most modern version of the nonlocal (NL) van der Waals correction to describe very large weakly interacting molecular systems dominated by noncovalent interactions. Prior to the assessment, an accurate and homogeneous set of reference interaction energies was computed for the supramolecular complexes constituting the L7 and S12L data sets by using the novel, precise, and efficient DLPNO-CCSD(T) method at the complete basis set limit (CBS). The correction of the basis set superposition error and the inclusion of the deformation energies (for the S12L set) have been crucial for obtaining precise DLPNO-CCSD(T)/CBS interaction energies. Among the density functionals evaluated, the double-hybrid revPBE0-DH-NL and B2PLYP-NL with the three-body dispersion correction provide remarkably accurate association energies very close to the chemical accuracy. Overall, the NL van der Waals approach combined with proper density functionals can be seen as an accurate and affordable computational tool for the modeling of large weakly bonded supramolecular systems.Financial support by the “Ministerio de Economía y Competitividad” (MINECO) of Spain and European FEDER funds through projects CTQ2011-27253 and CTQ2012-31914 is acknowledged. The support of the Generalitat Valenciana (Prometeo/2012/053) is also acknowledged. J.A. thanks the EU for the FP7-PEOPLE-2012-IEF-329513 grant. J.C. acknowledges the “Ministerio de Educación, Cultura y Deporte” (MECD) of Spain for a predoctoral FPU grant
WASP-113b and WASP-114b, two inflated hot Jupiters with contrasting densities
Aims. We present the discovery and characterisation of the exoplanets WASP-113b and WASP-114b by the WASP surveys, SOPHIE and CORALIE. Methods. The planetary nature of the systems was established by performing follow-up photometric and spectroscopic observations. The follow-up data were combined with the WASP-photometry and analysed with an MCMC code to obtain system parameters. Results. The host stars WASP-113 and WASP-114 are very similar. They are both early G-type stars with an effective temperature of ~5900 K, [Fe/H] ~ 0.12, and log g~ 4.1 dex. However, WASP-113 is older than WASP-114. Although the planetary companions have similar radii, WASP-114b is almost four times heavier than WASP-113b. WASP-113b has a mass of 0.48 MJup and an orbital period of ~4.5 days; WASP-114b has a mass of 1.77 MJup and an orbital period of ~1.5 days. Both planets have inflated radii, in particular WASP-113 with a radius anomaly of ℜ = 0.35. The high scale height of WASP-113b (~950 km) makes it a good target for follow-up atmospheric observations.Publisher PDFPeer reviewe
"Inter-Longitude Astronomy" (ILA) project : current highlights and perspectives : I. Magnetic vs. non-magneticinteracting binary stars
We present a review of highlights of our photometric and photo-polarimetric monitoring and mathematical modeling of interacting binary stars of different types classical, asynchronous, intermedi ate polars with 25 timescales corresponding to differ ent physical mechanisms and their combinations (part "Polar"); negative and positive superhumpers in nova-like and dwarf novae stars ("Superhumper"); symbiotic ("Symbiosis"); eclipsing variables with and without ev idence for a current mass transfer ("Eclipser") with a special emphasis on systems with a direct impact of the stream into the gainor star's atmosphere, which we propose to call "Impactors", or V361 Lyr-type stars. Other parts of the ILA project are "Stellar Bell" (pul sating variables of different types and periods - M, SR, RV Tau, RR Lyr, Delta Sct) and "New Variable".
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Glycan biomarkers of autoimmunity and bile acid-associated alterations of the human glycome: primary biliary cirrhosis and primary sclerosing cholangitis-specific glycans
We have recently introduced multiple reaction monitoring (MRM) mass spectrometry as a novel tool for glycan biomarker research and discovery. Herein, we employ this technique to characterize the site-specific glycan alterations associated with primary biliary cirrhosis (PBC) and primary sclerosing cholangitis (PSC). Glycopeptides associated with disease severity were also identified. Multinomial regression modelling was employed to construct and validate multi-analyte diagnostic models capable of accurately distinguishing PBC, PSC, and healthy controls from one another (AUC = 0.93 +/- 0.03). Finally, to investigate how disease-relevant environmental factors can influence glycosylation, we characterized the ability of bile acids known to be differentially expressed in PBC to alter glycosylation. We hypothesize that this could be a mechanism by which altered selfantigens are generated and become targets for immune attack. This work demonstrates the utility of the MRM method to identify diagnostic site-specific glycan classifiers capable of distinguishing even related autoimmune diseases from one another.Afdeling Klinische Chemie en Laboratoriumgeneeskunde (AKCL
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