906 research outputs found
Eclipsing binaries and fast rotators in the Kepler sample. Characterization via radial velocity analysis from Calar Alto
The Kepler mission has provided high-accurate photometric data in a long time
span for more than two hundred thousands stars, looking for planetary transits.
Among the detected candidates, the planetary nature of around 15% has been
established or validated by different techniques. But additional data is needed
to characterize the rest of the candidates and reject other possible
configurations. We started a follow-up program to validate, confirm, and
characterize some of the planet candidates. In this paper we present the radial
velocity analysis (RV) of those presenting large variations, compatible with
being eclipsing binaries. We also study those showing large rotational
velocities, which prevents us from obtaining the necessary precision to detect
planetary-like objects. We present new RV results for 13 Kepler objects of
interest (KOIs) obtained with the CAFE spectrograph at the Calar Alto
Observatory, and analyze their high-spatial resolution images and the Kepler
light curves of some interesting cases. We have found five spectroscopic and
eclipsing binaries. Among them, the case of KOI-3853 is of particular interest.
This system is a new example of the so-called heartbeat stars, showing dynamic
tidal distortions in the Kepler light curve. We have also detected duration and
depth variations of the eclipse. We suggest possible scenarios to explain such
effect, including the presence of a third substellar body possibly detected in
our RV analysis. We also provide upper mass limits to the transiting companions
of other six KOIs with large rotational velocities. This property prevents the
RV method to obtain the necessary precision to detect planetary-like masses.
Finally, we analyze the large RV variations of other two KOIs, incompatible
with the presence of planetary-mass objects. These objects are likely to be
stellar binaries but a longer timespan is still needed.Comment: Accepted for publication in A&A. 18 pages, 9 figures, 17 tables. This
version fixes an error affecting the values of tables A.1-A.13. The text
remains unaltere
Kepler-539: a young extrasolar system with two giant planets on wide orbits and in gravitational interaction
We confirm the planetary nature of Kepler-539b (aka Kepler object of interest
K00372.01), a giant transiting exoplanet orbiting a solar-analogue G2 V star.
The mass of Kepler-539b was accurately derived thanks to a series of precise
radial velocity measurements obtained with the CAFE spectrograph mounted on the
CAHA 2.2m telescope. A simultaneous fit of the radial-velocity data and Kepler
photometry revealed that Kepler-539b is a dense Jupiter-like planet with a mass
of Mp = 0.97 Mjup and a radius of Rp = 0.747 Rjup, making a complete circular
revolution around its parent star in 125.6 days. The semi-major axis of the
orbit is roughly 0.5 au, implying that the planet is at roughly 0.45 au from
the habitable zone. By analysing the mid-transit times of the 12 transit events
of Kepler-539b recorded by the Kepler spacecraft, we found a clear modulated
transit time variation (TTV), which is attributable to the presence of a planet
c in a wider orbit. The few timings available do not allow us to precisely
estimate the properties of Kepler-539c and our analysis suggests that it has a
mass between 1.2 and 3.6 Mjup, revolving on a very eccentric orbit (0.4<e<0.6)
with a period larger than 1000 days. The high eccentricity of planet c is the
probable cause of the TTV modulation of planet b. The analysis of the CAFE
spectra revealed a relatively high photospheric lithium content, A(Li)=2.48
dex, which, together with both a gyrochronological and isochronal analysis,
suggests that the parent star is relatively young.Comment: 11 pages, 14 figures, accepted for publication in Astronomy &
Astrophysic
Kepler-447b: a hot-Jupiter with an extremely grazing transit
We present the radial velocity confirmation of the extrasolar planet
Kepler-447b, initially detected as a candidate by the Kepler mission. In this
work, we analyze its transit signal and the radial velocity data obtained with
the Calar Alto Fiber-fed Echelle spectrograph (CAFE). By simultaneously
modeling both datasets, we obtain the orbital and physical properties of the
system. According to our results, Kepler-447b is a Jupiter-mass planet
(), with an estimated radius of
(uncertainties provided in this work are
unless specified). This translates into a sub-Jupiter density. The
planet revolves every days in a slightly eccentric orbit
() around a G8V star with detected activity in the
Kepler light curve. Kepler-447b transits its host with a large impact parameter
(), being one of the few planetary grazing transits
confirmed so far and the first in the Kepler large crop of exoplanets. We
estimate that only around 20% of the projected planet disk occults the stellar
disk. The relatively large uncertainties in the planet radius are due to the
large impact parameter and short duration of the transit. Planets with such an
extremely large impact parameter can be used to detect and analyze interesting
configurations such as additional perturbing bodies, stellar pulsations,
rotation of a non-spherical planet, or polar spot-crossing events. All these
scenarios would periodically modify the transit properties (depth, duration,
and time of mid-transit), what could be detectable with sufficient accurate
photometry. Short-cadence photometric data (at the 1 minute level) would help
in the search for these exotic configurations in grazing planetary transits
like that of Kepler-447b.Comment: Accepted for publication in A&A. 13 pages, 8 figures, 4 tables. This
version replaces an earlier version of the pape
Physical properties, starspot activity, orbital obliquity, and transmission spectrum of the Qatar-2 planetary system from multi-colour photometry
We present seventeen high-precision light curves of five transits of the
planet Qatar-2b, obtained from four defocussed 2m-class telescopes. Three of
the transits were observed simultaneously in the SDSS griz passbands using the
seven-beam GROND imager on the MPG/ESO 2.2-m telescope. A fourth was observed
simultaneously in Gunn grz using the CAHA 2.2-m telescope with BUSCA, and in r
using the Cassini 1.52-m telescope. Every light curve shows small anomalies due
to the passage of the planetary shadow over a cool spot on the surface of the
host star. We fit the light curves with the prism+gemc model to obtain the
photometric parameters of the system and the position, size and contrast of
each spot. We use these photometric parameters and published spectroscopic
measurements to obtain the physical properties of the system to high precision,
finding a larger radius and lower density for both star and planet than
previously thought. By tracking the change in position of one starspot between
two transit observations we measure the orbital obliquity of Qatar-2 b to be
4.3 \pm 4.5 degree, strongly indicating an alignment of the stellar spin with
the orbit of the planet. We calculate the rotation period and velocity of the
cool host star to be 11.4 \pm 0.5 d and 3.28 \pm 0.13 km/s at a colatitude of
74 degree. We assemble the planet's transmission spectrum over the 386-976 nm
wavelength range and search for variations of the measured radius of Qatar-2 b
as a function of wavelength. Our analysis highlights a possible H2/He Rayleigh
scattering in the blue.Comment: 20 pages, 14 figures, to appear in Monthly Notices of the Royal
Astronomical Societ
Simultaneous follow-up of planetary transits: revised physical properties for the planetary systems HAT-P-16 and WASP-21
Context. By now more than 300 planets transiting their host star have been
found, and much effort is being put into measuring the properties of each
system. Light curves of planetary transits often contain deviations from a
simple transit shape, and it is generally difficult to differentiate between
anomalies of astrophysical nature (e.g. starspots) and correlated noise due to
instrumental or atmospheric effects. Our solution is to observe transit events
simultaneously with two telescopes located at different observatories. Aims.
Using this observational strategy, we look for anomalies in the light curves of
two transiting planetary systems and accurately estimate their physical
parameters. Methods. We present the first photometric follow-up of the
transiting planet HAT-P-16 b, and new photometric observations of WASP-21 b,
obtained simultaneously with two medium-class telescopes located in different
countries, using the telescope defocussing technique. We modeled these and
other published data in order to estimate the physical parameters of the two
planetary systems. Results. The simultaneous observations did not highlight
particular features in the light curves, which is consistent with the low
activity levels of the two stars. For HAT-P-16, we calculated a new ephemeris
and found that the planet is 1.3 \sigma colder and smaller (Rb = 1.190 \pm
0.037 RJup) than the initial estimates, suggesting the presence of a massive
core. Our physical parameters for this system point towards a younger age than
previously thought. The results obtained for WASP-21 reveal lower values for
the mass and the density of the planet (by 1.0 \sigma and 1.4 \sigma
respectively) with respect to those found in the discovery paper, in agreement
with a subsequent study. We found no evidence of any transit timing variations
in either system.Comment: 8 pages, 6 figures, accepted for publication in A&
Physical properties of the WASP-44 planetary system from simultaneous multi-colour photometry
We present ground-based broad-band photometry of two transits in the WASP-44
planetary system obtained simultaneously through four optical (Sloan g', r',
i', z') and three near-infrared (NIR; J, H, K) filters. We achieved low
scatters of 1-2 mmag per observation in the optical bands with a cadence of 48
s, but the NIR-band light curves present much greater scatter. We also observed
another transit of WASP-44 b by using a Gunn-r filter and telescope
defocussing, with a scatter of 0.37 mmag per point and an observing cadence
around 135 s. We used these data to improve measurements of the time of
mid-transit and the physical properties of the system. In particular, we
improved the radius measurements of the star and planet by factors of 3 and 4,
respectively. We find that the radius of WASP-44 b is 1.002 R_Jup, which is
slightly smaller than previously thought and differs from that expected for a
core-free planet. In addition, with the help of a synthetic spectrum, we
investigated the theoretically-predicted variation of the planetary radius as a
function of wavelength, covering the range 370-2440 nm. We can rule out extreme
variations at optical wavelengths, but unfortunately our data are not precise
enough (especially in the NIR bands) to differentiate between the theoretical
spectrum and a radius which does not change with wavelength.Comment: 13 pages, 6 figures, to appear in Monthly Notices of the Royal
Astronomical Societ
Effects of a medium cut-off (Theranova®) dialyser on haemodialysis patients: a prospective, cross-over study
Background. Despite significant advances in haemodialysis (HD) in recent decades, current dialysis techniques are limited by
inadequate removal of uraemic solutes such as middle molecules and protein-bound uraemic toxins. Novel medium cut-off
(MCO) membrane or \u2018expanded haemodialysis\u2019 (HDx) provides diffusive removal of conventional and large middle
molecular weight uraemic toxins, with marginal albumin leak.
Methods. This prospective, open-label, controlled, cross-over pilot study compared HDx (novel MCO membrane TheranovaVR
400) and conventional HD in 20 prevalent HD patients. Biochemical, dialysis adequacy and safety measures (adverse events,
infections and hospitalization frequency) were recorded. Ten patients underwent conventional HD high-flux dialyser and
10 patients underwent HDx for 3 months, and the patients then switched and received the other treatment for a further
3 months.
Results. Treatment with HDx was associated with a significant reduction in serum albumin concentration [median
(interquartile range) reduction 0.45 g/dL (0.575 to 0.05); P \ubc 0.025]. However, median albumin levels were 3.5 g/dL and
no patients had clinical symptoms of hypoalbuminaemia or needed intravenous albumin administration. The number of
infections was lower in patients treated with HDx (n \ubc 7/19) compared with patients treated with HD (n \ubc 14/20; P \ubc 0.03).
Patients treated with HDx had reduced levels of interleukin (IL)-1b (from 0.06 6 0.02 pg/mL versus 0.28 6 0.18 pg/mL with HD)
and IL-6 (6.45 6 1.57 pg/mL versus 9.48 6 2.15 pg/mL), while tumour necrosis factor-a levels remain unchanged.
Conclusions. This study demonstrates that the chronic use of the novel MCO dialyser TheranovaVR
appears to be safe and
well-tolerated, without serious side effects or hypoalbuminaemia, as well as fewer infections. These results need to be
confirmed in larger randomized clinical trials
Current Therapy in CKD Patients Can Affect Vitamin K Status
Chronic kidney disease (CKD) patients have a higher risk of cardiovascular (CVD) morbidity and mortality compared to the general population. The links between CKD and CVD are not fully elucidated but encompass both traditional and uremic-related risk factors. The term CKD-mineral and bone disorder (CKD-MBD) indicates a systemic disorder characterized by abnormal levels of calcium, phosphate, PTH and FGF-23, along with vitamin D deficiency, decreased bone mineral density or altered bone turnover and vascular calcification. A growing body of evidence shows that CKD patients can be affected by subclinical vitamin K deficiency; this has led to identifying such a condition as a potential therapeutic target given the specific role of Vitamin K in metabolism of several proteins involved in bone and vascular health. In other words, we can hypothesize that vitamin K deficiency is the common pathogenetic link between impaired bone mineralization and vascular calcification. However, some of the most common approaches to CKD, such as (1) low vitamin K intake due to nutritional restrictions, (2) warfarin treatment, (3) VDRA and calcimimetics, and (4) phosphate binders, may instead have the opposite effects on vitamin K metabolism and storage in CKD patients
New transit observations for HAT-P-30 b, HAT-P-37 b, TrES-5 b, WASP-28 b, WASP-36 b, and WASP-39 b
We present new transit light curves for planets in six extrasolar planetary
systems. They were acquired with 0.4-2.2 m telescopes located in west Asia,
Europe, and South America. When combined with literature data, they allowed us
to redetermine system parameters in a homogeneous way. Our results for
individual systems are in agreement with values reported in previous studies.
We refined transit ephemerides and reduced uncertainties of orbital periods by
a factor between 2 and 7. No sign of any variations in transit times was
detected for the planets studied.Comment: Submitted to Acta Astronomic
Multiparametric Whole Blood Dissection: A one-shot comprehensive picture of the human hematopoietic system
Human hematopoiesis is a complex and dynamic system where morphologically and functionally diverse mature cell types are generated and maintained throughout life by bone marrow (BM) Hematopoietic Stem/Progenitor Cells (HSPC). Congenital and acquired hematopoietic disorders are often diagnosed through the detection of aberrant frequency or composition of hematopoietic cell populations. We here describe a novel protocol, called âWhole Blood Dissectionâ (WBD), capable of analyzing in a single testâtube, hematopoietic progenitors and all major mature cell lineages composing either BM or peripheral blood (PB) through a multiparametric flowâcytometry analysis. WBD allows unambiguously identifying in the same tube up to 23 different blood cell types including HSPC subtypes and all the major myeloid and lymphoid lineage compartments at different stages of maturation, through a combination of 17 surface and 1 viability cell markers. We assessed the efficacy of WBD by analyzing BM and PB samples from adult (nâ=â8) and pediatric (nâ=â9) healthy donors highlighting ageârelated shift in cell composition. We also tested the capability of WBD on detecting aberrant hematopoietic cell composition in clinical samples of patients with primary immunodeficiency or leukemia unveiling expected and novel hematopoietic unbalances. Overall, WBD allows unambiguously identifying >99% of the cell subpopulations composing a blood sample in a reproducible, standardized, costâ, and timeâefficient manner. This tool has a wide range of potential preâclinical and clinical applications going from the characterization of hematopoietic disorders to the monitoring of hematopoietic reconstitution in patients after transplant or gene therapy
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