878 research outputs found
Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. V.: A Massive Jupiter orbiting the very low metallicity giant star BD+03 2562 and a possible planet around HD~103485
We present two evolved stars from the TAPAS (Tracking Advanced PlAnetary
Systems) with HARPS-N project devoted to RV precision measurements of
identified candidates within the PennState - Torun Centre for Astronomy Planet
Search. Evolved stars with planets are crucial to understand the dependency of
the planet formation mechanism on the mass and metallicity of the parent star
and to study star-planet interactions. The paper is based on precise radial
velocity (RV) measurements, for HD 103485 we collected 57 epochs over 3317 days
with the Hobby-Eberly Telescope and its High Resolution Spectrograph and 18
ultra-precise HARPS-N data over 919 days. For BD+03 2562 we collected 46 epochs
of HET data over 3380 days and 19 epochs of HARPS-N data over 919 days. We
present the analysis of the data and the search for correlations between the RV
signal and stellar activity, stellar rotation and photometric variability.
Based on the available data, we interpret the RV variations measured in both
stars as Keplerian motion. Both stars have masses close to Solar (1.11 and
1.14), very low metallicities ([Fe/H]=-0.50 and -0.71), and, both have Jupiter
planetary mass companions (m sin i=7 and 6.4 Mj), in close to terrestrial
orbits (1.4 and 1.3~au), with moderate eccentricities (e=0.34 and 0.2).
However, we cannot totally exclude that the signal in the case of HD~103485 is
due to rotational modulation of active regions. Based on the current data, we
conclude that BD+03 2562 has a bona fide planetary companion while for HD
103485 we cannot totally exclude that the best explanation for the RV signal
modulations is not the existence of a planet but stellar activity. If, the
interpretation remains that both stars have planetary companions they represent
systems orbiting very evolved stars with very low metallicities, a challenge to
the conditions required for the formation of massive giant gas planets.Comment: Acepted A&A 12 pages, 11 figure
Application of random coherence order selection in gradient-enhanced multidimensional NMR
Development of multidimensional NMR is essential to many applications, for example in high resolution structural studies of biomolecules. Multidimensional techniques enable separation of NMR signals over several dimensions, improving signal resolution, whilst also allowing identification of new connectivities. However, these advantages come at a significant cost. The Fourier transform theorem requires acquisition of a grid of regularly spaced points to satisfy the Nyquist criterion, while frequency discrimination and acquisition of a pure phase spectrum require acquisition of both quadrature components for each time point in every indirect (non-acquisition) dimension, adding a factor of 2 to the number of free-induction decays which must be acquired, where is the number of dimensions. Compressed sensing (CS) ℓ-norm minimisation in combination with non-uniform sampling (NUS) has been shown to be extremely successful in overcoming the Nyquist criterion. Previously, maximum entropy reconstruction has also been used to overcome the limitation of frequency discrimination, processing data acquired with only one quadrature component at a given time interval, known as random phase detection (RPD), allowing a factor of two reduction in the number of points for each indirect dimension (Maciejewski et al. 2011 108 16640). However, whilst this approach can be easily applied in situations where the quadrature components are acquired as amplitude modulated data, the same principle is not easily extended to phase modulated (P-/N-type) experiments where data is acquired in the form exp () or exp (−), and which make up many of the multidimensional experiments used in modern NMR. Here we demonstrate a modification of the CS ℓ-norm approach to allow random coherence order selection (RCS) for phase modulated experiments; we generalise the nomenclature for RCS and RPD as random quadrature detection (RQD). With this method, the power of RQD can be extended to the full suite of experiments available to modern NMR spectroscopy, allowing resolution enhancements for all indirect dimensions; alone or in combination with NUS, RQD can be used to improve experimental resolution, or shorten experiment times, of considerable benefit to the challenging applications undertaken by modern NMR.This is the final version of the article. It first appeared from IOP Publishing via http://dx.doi.org/10.1088/1742-6596/699/1/01200
Bilateral coronary artery to pulmonary trunk fistulae detected by coronary angiography and evaluated by ECG-gated SPECT myocardial perfusion imaging: report of two cases
Coronary artery fistulae (CAF) are anomalies related to coronary artery abnormal termination. This is a very rare congenital malformation accounting for about 0.2–0.4% of congenital cardiac anomalies, but in some patients it can be haemodynamically important. Single-photon emission computed tomography or positron emission tomography myocardial perfusion imaging (MPI) using radioactive agents is widely used in clinical practice for cardiac ischaemia detection as a very sensitive and non-invasive tool. We are going to present 2 patients with bilateral CAFs to the pulmonary trunk without signs of the rest or stress ischaemia in MPI.
Large oxygen-isotope effect in Sr_{0.4}K_{0.6}BiO_{3}: Evidence for phonon-mediated superconductivity
Oxygen-isotope effect has been investigated in a recently discovered
superconductor Sr_{0.4}K_{0.6}BiO_{3}. This compound has a distorted perovskite
structure and becomes superconducting at about 12 K. Upon replacing ^{16}O with
^{18}O by 60-80%, the T_c of the sample is shifted down by 0.32-0.50 K,
corresponding to an isotope exponent of alpha_{O} = 0.40(5). This isotope
exponent is very close to that for a similar bismuthate superconductor
Ba_{1-x}K_{x}BiO_{3} with T_c = 30 K. The very distinctive doping and T_c
dependencies of alpha_{O} observed in bismuthates and cuprates suggest that
bismuthates should belong to conventional phonon-mediated superconductors while
cuprates might be unconventional supercondutors.Comment: 9 pages, 5 figure
A Nonparametric Method for the Derivation of α/β Ratios from the Effect of Fractionated Irradiations
Multifractionation isoeffect data are commonly analysed under the assumption that cell survival determines the observed tissue or tumour response, and that it follows a linear-quadratic dose dependence. The analysis is employed to derive the α/β ratios of the linear-quadratic dose dependence, and different methods have been developed for this purpose. A common method uses the so-called Fe plot. A more complex but also more rigorous method has been introduced by Lam et al. (1979). Their method, which is based on numerical optimization procedures, is generalized and somewhat simplified in the present study. Tumour-regrowth data are used to explain the nonparametric procedure which provides α/β ratios without the need to postulate analytical expressions for the relationship between cell survival and regrowth delay
Departure from the constant-period ephemeris for the transiting exoplanet WASP-12 b
Most hot Jupiters are expected to spiral in towards their host stars due to
transfering of the angular momentum of the orbital motion to the stellar spin.
Their orbits can also precess due to planet-star interactions. Calculations
show that both effects could be detected for the very-hot exoplanet WASP-12 b
using the method of precise transit timing over a timespan of the order of 10
yr. We acquired new precise light curves for 29 transits of WASP-12 b,
spannning 4 observing seasons from November 2012 to February 2016. New
mid-transit times, together with literature ones, were used to refine the
transit ephemeris and analyse the timing residuals. We find that the transit
times of WASP-12 b do not follow a linear ephemeris with a 5 sigma confidence
level. They may be approximated with a quadratic ephemeris that gives a rate of
change in the orbital period of -2.56 +/- 0.40 x 10^{-2} s/yr. The tidal
quality parameter of the host star was found to be equal to 2.5 x 10^5 that is
comparable to theoretical predictions for Sun-like stars. We also consider a
model, in which the observed timing residuals are interpreted as a result of
the apsidal precession. We find, however, that this model is statistically less
probable than the orbital decay.Comment: Accepted for publication in A&A Letter
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