Central Transit Time Research Articles

Noninvasive Assessment Of Cardiovascular Hemodynamics During Exercise Using Systolic Time Intervals

Noninvasive Assessment Of Cardiovascular Hemodynamics During Exercise Using Systolic Time Intervals

First Observation of a Planetary Transit with the SPARC4 CCD: Improved Parameters for HATS-24b

The photometric monitoring of planetary transits is an important method for the characterization of exoplanets. Transiting exoplanets allow measurements of the planetary radius and mass, providing information on the physical structure of the planet. Therefore, the parameters obtained with the transit method become fundamental for a comparative study of exoplanets in different planetary systems. In this work, we present the results obtained from observations of a transit event of the exoplanet HATS-24b using the new SPARC4 CCD mounted on the 1.6 m telescope of the Pico dos Dias Observatory (OPD). We have used Bayesian statistical inference to determine the physical parameters of this exoplanet, where we obtained a radius of 1.395+-0.057 RJup, mass of 2.26+-0.17 MJup, and density of 1.03+-0.15 g/cm^3. We have combined our measurements of the central time of transit and orbital period with values from the literature to obtain an improved ephemeris for the transits of HATS-24b, Tc=(2457948.709321+-0.000039) + E (1.3484978+-0.0000009). We have applied the differential analysis using a solar spectrum to recalculate the stellar surface parameters of HATS-24, where we obtained Teff=6125+-94 K, log(g)=4.370+-0.045 cm/s^2, and [Fe/H]=-0.229+-0.058 dex. This allowed us to estimate an equilibrium temperature for HATS-24b of Teq=2166+-53 K. The mass and radius of HATS-24b are consistent with the theoretical model of a pure helium-hydrogen planet at 1 Gy.

Relationship of prolonged global and regional central circulatory transit time with hemodynamics

Methods Forty nine subjects undergoing clinically indicated right and left heart cardiac catheterization were prospectively recruited to undergo MRI in a 1.5T scanner. First pass perfusion using steady state free precession saturation recovery sequence was performed with gadolinium infusion at 0.01 mmol/kg. Global TT was defined as the time between the peaks of time intensity curves between the right atrium and the ascending aorta. Segmental TT included TT between right atrium to pulmonary artery (right heart TT), pulmonary artery to left atrium (pulmonary TT), or left atrium to ascending aorta (left heart TT). All TTs were normalized to heart rate. Multivariate regression analysis was performed to delineate the relationship of hemodynamic parameters measured during cardiac catheterization to TT. Receiver operating characteristic (ROC) analyses were performed to assess ability of global and segmental TT to predict elevated LVEDP.

Refined physical properties andg′,r′,i′,z′,J, H, Ktransmission spectrum of WASP-23b from the ground

Multi-band observations of planetary transits using the telescope defocus technique may yield high-quality light curves suitable for refining the physical properties of exoplanets even with small or medium size telescopes. Such observations can be used to construct a broad-band transmission spectrum of transiting planets and search for the presence of strong absorbers. We have thoroughly characterised the orbital ephemeris and physical properties of the transiting planet and host star in the WASP-23b system, constructed a broad-band transmission spectrum of WASP-23b and performed a comparative analysis with theoretical models of hot Jupiters. We observed a complete transit of WASP-23b in seven bands simultaneously, using the GROND instrument on the MPG/ESO 2.2m telescope at La Silla Observatory and telescope defocussing. The optical data were taken in the Sloan g',r',i' and z' bands. The resulting light curves are of high quality, with a root-mean-square scatter of the residual as low as 330ppm in the z'-band, with a cadence of 90s. Near-infrared data were obtained in the JHK bands. We performed MCMC analysis of our photometry plus existing radial velocity data to refine measurements of the ephemeris and physical properties of the WASP-23. We constructed a broad-band transmission spectrum of WASP-23b and compared it with a theoretical transmission spectrum of a Hot Jupiter. We measured the central transit time with a precision about 8s. From this and earlier observations we obtain an orbital period of P=2.9444300+/-0.0000011d. Our analysis also yielded a larger radius and mass for the planet (Rp=1.067+0.045-0.038 RJup and, Mp=0.917+0.040-0.039MJup). The transmission spectrum is marginally flat, given the limited precision of the measurements for the planet radius and poor spectral resolution of the data.

Association of global and regional central circulation transit time with left ventricular end diastolic pressure using dynamic magnetic resonance imaging

Background Prolonged central circulation transit time (TT) has long been associated with heart failure and left ventricular (LV) dysfunction. However, it is not known which portion of the central circulation is associated with this prolongation. Moreover, the relation of global and regional TT to LV end diastolic pressure (LVEDP) is not defined. In this study we assessed the global and regional TT in each portion of the central circulation and investigated their relations to LVEDP in patients undergoing cardiac catheterization. Methods All patients were prospectively recruited and underwent cardiac MRI within 5 hours of cardiac catheterization. Dynamic MR images were acquired during the infusion of gadopentetate dimeglumine (0.01 mmol/kg) at 6 ml/s. Areas of interest were drawn and propagated through phases in the right atrium (RA), right ventricle (RV), main pulmonary artery (PA), left and right lung, left atrium (LA), LV and ascending aorta to construct timeintensity curves. TT was defined as the time between the peaks of time-intensity curves. All TTs were normalized to RR intervals. Central circulation TT was defined as TT from RA to aorta, while regional TT was defined as RA to RV, RV to PA, PA to lungs (averaged value of the left and right lung), lungs to LA, LA to LV, and LV to aorta. LVEDP was assessed during cardiac catheterization. Results Of the 48 subjects studied the mean age was 59 years and 32 (67%) were male. Average LV ejection fraction (LVEF) was 48±15% and the LVEDP 15±8 mmHg. Central TT was significantly prolonged in patients with elevated LVEDP (>12 mmHg) 15.7±5.8 cardiac cycles vs. 10.5±2.2 cardiac cycles (p=0.002) in those with normal LVEDP (≤12 mmHg). Regional analysis demonstrated that TT prolongation was present in PA to lungs, lungs to LA, LA to LV and LV to aorta but not in RA to RV and RV to PA. The multivariate regression model which included all regional TTs as covariables showed that TT from lung to LA had the strongest association with LVEDP (beta coefficients 0,424, p<0.001) followed by TT from LA to LV (0,325, p=0.007) and TT from PA to lungs (0,240, p=0.037). TTs from other regions were not significantly associated with LVEDP. Conclusions Central and regional circulation TT can be assessed by dynamic MR imaging. Central TT was significantly prolonged in patients with elevated LVEDP largely due to regional TT prolongation in lungs to LA, LA to LV and PA to lungs circulation. Funding None.

Ground-based detection of thermal emission from the exoplanet WASP-19b

Abstract We present an occultation of the newly discovered hot Jupiter system WASP-19, observed with the High Acuity Wide-field K-band Imager instrument on the VLT, in order to measure thermal emission from the planet's dayside at ∼2μm. The light curve was analysed using a Markov Chain Monte Carlo method to find the eclipse depth and the central transit time. The transit depth was found to be 0.366 ± 0.072 per cent, corresponding to a brightness temperature of 2540 ± 180 K. This is significantly higher than the calculated (zero-albedo) equilibrium temperature and indicates that the planet shows poor redistribution of heat to the night side, consistent with models of highly irradiated planets. Further observations are needed to confirm the existence of a temperature inversion and possibly molecular emission lines. The central eclipse time was found to be consistent with a circular orbit.

ON THE APPARENT ORBITAL INCLINATION CHANGE OF THE EXTRASOLAR TRANSITING PLANET TrES-2b

On June 15, 2009 UT the transit of TrES-2b was detected using the University of Arizona's 1.55 meter Kuiper Telescope with 2.0-2.5 millimag RMS accuracy in the I-band. We find a central transit time of $T_c = 2454997.76286 \pm0.00035$ HJD, an orbital period of $P = 2.4706127 \pm 0.0000009$ days, and an inclination angle of $i = 83^{\circ}.92 \pm 0.05$, which is consistent with our re-fit of the original I-band light curve of O'Donovan et al. (2006) where we find $i = 83^{\circ}.84 \pm0.05$. We calculate an insignificant inclination change of $\Delta i = -0^{\circ}.08 \pm 0.07$ over the last 3 years, and as such, our observations rule out, at the $\sim 11 \sigma$ level, the apparent change of orbital inclination to $i_{predicted} = 83^{\circ}.35 \pm0.1$ as predicted by Mislis and Schmitt (2009) and Mislis et al. (2010) for our epoch. Moreover, our analysis of a recently published Kepler Space Telescope light curve (Gilliland et al. 2010) for TrES-2b finds an inclination of $i = 83^{\circ}.91 \pm0.03$ for a similar epoch. These Kepler results definitively rule out change in $i$ as a function of time. Indeed, we detect no significant changes in any of the orbital parameters of TrES-2b.

Exoplanet Transit Database. Reduction and processing of the photometric data of exoplanet transits

We demonstrate the newly developed resource for exoplanet researchers – The Exoplanet Transit Database. This database is designed to be a web application and it is open for any exoplanet observer. It came on-line in September 2008. The ETD consists of three individual sections. One serves for predictions of the transits, the second one for processing and uploading new data from the observers. We use a simple analytical model of the transit to calculate the central time of transit, its duration and the depth of the transit. These values are then plotted into the observed–computed diagrams (O–C), that represent the last part of the application.

FOLLOW-UP OBSERVATIONS OF THE NEPTUNE MASS TRANSITING EXTRASOLAR PLANET HAT-P-11b

We have confirmed the existence of the transiting super Neptune extrasolar planet HAT-P-11b. On May 1, 2009 UT the transit of HAT-P-11b was detected at the University of Arizona's 1.55m Kuiper Telescope with 1.7 millimag rms accuracy. We find a central transit time of T_c = 2454952.92534+/-0.00060 BJD; this transit occurred 80+/-73 seconds sooner than previous measurements (71 orbits in the past) would have predicted. Hence, our transit timing rules out the presence of any large (>200 s) deviations from the ephemeris of Bakos et al. (2009). We obtain a slightly more accurate period of P=4.8878045+/-0.0000043 days. We measure a slightly larger planetary radius of R_p=0.452+/-0.020 R_J (5.07+/-0.22 R_earth) compared to Bakos and co-workers' value of 0.422+/-0.014 R_J (4.73+/-0.16 R_earth). Our values confirm that HAT-P-11b is very similar to GJ 436b (the only other known transiting super Neptune) in radius and other bulk properties.

A Hubble Space Telescope transit light curve for GJ 436b

We present time series photometry for six partial transits of GJ 436b obtained with the Fine Guidance Sensor instrument on the Hubble Space Telescope(HST). Our analysis of these data yields independent estimates of the host star’s radius R⋆ = 0.505 +0.029 −0.020 R⊙, and the planet’s orbital period P = 2.643882 +0.000060 −0.000058 d, orbital inclination i = 85.80 ◦ +0.21 ◦ −0.25 ◦ , mean central transit time Tc = 2454455.279241 +0.00026 −0.00025 HJD, and radius Rp = 4.90 +0.45 −0.33 R⊕. The radius we determine for the planet is larger than the previous findings from analyses of an infrared light curve obtained with the Spitzer Space Telescope. Although this discrepancy has a 92% formal significance (1.7σ), it might be indicative of systematic errors that still infl uence the analyses of even the highest-precision transit li ght curves. Comparisons of all the measured radii to theoretical models suggest that GJ 436b has a H/He envelope of∼ 10% by mass. We point out the similarities in structure between this planet and Uranus and Neptune and discuss possible parallels between these planets’ formation environments and dynamical evolution. We also fin d that the transit times for GJ 436b are constant to within 10 s over the 11 planetary orbits that the HST data span. However, the ensemble of published values exhibits a long-term drift and our mean transit time is 128 s later than that expected from the Spitzer ephemeris. The sparseness of the currently available data hinders distinguishing between an error in the orbital period or perturbations aris ing from an additional object in the system as the cause of the apparent trend. Assuming the drift is due to an error in the orbital per iod we obtain an improved estimate for it of P = 2.643904± 0.000005 d. This value and our measured transit times will serve as important benchmarks in future studies of the GJ 436 system.

The analysis of radioisotope cardiac output dilution curves.

An analysis of radioisotope dilution cardiac output curves yielded 19 parameters which were measured from curves obtained before and after therapeutic manoeuvres in patients such as haemodialysis and the administration of hypotensive drugs. The changes observed in the parameters were consistent with the known pharmacological actions of the compounds. By means of a multiple regression analysis, three variables—central mean transit time, right-heart volume index and the ratio of the dilution curve area to its plateau height—were found which can be used to monitor for changes occurring in the shape of the dilution curve which are consistent with a deterioration of the patient's haemodynamic state.

On the theory of the indicator-dilution method for measurement of blood flow and volume.

On the theory of the indicator-dilution method for measurement of blood flow and volume.