On the Unique Solution of Planet and Star Parameters from an Extrasolar Planet Transit Light Curve

There is a unique solution of the planet and star parameters from a planet transit light curve with two or more transits if the planet has a circular orbit and the light curve is observed in a band pass where limb darkening is negligible. The existence of this unique solution is very useful for current planet transit surveys for several reasons. First, there is an analytic solution that allows a quick parameter estimate, in particular of Rp. Second, the stellar density can be uniquely derived from the transit light curve alone. The stellar density can be used to immediately rule out a giant star (and hence a much larger than planetary companion) and can also be used to put an upper limit on the stellar and planet radius even considering slightly evolved stars. Third, the presence of an additional fully blended star that contaminates an eclipsing system to mimic a planet transit can be largely ruled out from the transit light curve given a spectral type for the central star. Fourth, the period can be estimated from a single-transit light curve and a measured spectral type. All of these applications can be used to select the best planet transit candidates for mass determination by radial velocity follow-up. To use these applications in practice, the photometric precision and time sampling of the light curve must be high (better than 0.005 mag precision and 5 minute time sampling).Comment: 26 pages incl. 11 figs, submitted to Ap

Voltaje de referencia BandGap y módulo de comunicación serial para SAR ADC 10 bits de baja potencia para aplicaciones biomédicas

The document presents two designs a BandGap Reference Voltage, and a Communication Serial Module for a 10 bits SAR ADC for low-power applications. Designs were implemented using TSMC 0.18 µm CMOS technology with 1.8 V supply voltage. The BandGap Reference Voltage was designed to provide a reference voltage of 900 mV ±500 µV. The bandgap was tested at simulation level under different temperature conditions to ensure constant output in a temperature range from –40 °C to 85 °C. The Communication Serial Module is designed using the hardware description language Verilog. This module receives the 10 bits parallel output of the SAR ADC and retransmits the conversion result into a serial format using the SPI format. The Communication Serial Module was tested under a simulator, where multiple test cases were applied to stimulate in different ways the module. Both circuits were designed to accomplish the SAR ADC requirements in which BandGap supplies the reference voltage to the capacitor array in the SAR ADC and the Serial Module sends the data values after the conversion is finalized.ITESO, A. C

On the Period Distribution of Close-In Extrasolar Giant Planets

Transit (TR) surveys for extrasolar planets have recently uncovered a population of ``very hot Jupiters,'' planets with orbital periods of P< 3 d. At first sight this may seem surprising, given that radial velocity (RV) surveys have found a dearth of such planets, despite the fact that their sensitivity increases with decreasing P. We examine the confrontation between RV and TR survey results, paying particular attention to selection biases that favor short-period planets in transit surveys. We demonstrate that, when such biases and small-number statistics are properly taken into account, the period distribution of planets found by RV and TR surveys are consistent at better than the 1-sigma level. This consistency holds for a large range of reasonable assumptions. In other words, there are not enough planets detected to robustly conclude that the RV and TR short-period planet results are inconsistent. Assuming a logarithmic distribution of periods, we find that the relative frequency of very hot Jupiters (VHJ: P=1-3 d) to hot Jupiters (HJ: P=3-9 d) is 10-20%. Given an absolute frequency of HJ of ~1%, this implies that approximately one star in ~500-1000 has a VHJ. We also note that VHJ and HJ appear to be distinct in terms of their upper mass limit. We discuss the implications of our results for planetary migration theories, as well as present and future TR and RV surveys.Comment: 11 pages, 4 figures, 2 tables. Minor changes. Accepted to ApJ, to appear in the April 20, 2005 issue (v623

Investigation of alpha-nuclear potential families from elastic scattering experiments

In this work we present the continuation of the reported analysis [1] of the experimentally measured angular distributions of the reaction Cd-106(alpha, alpha)Cd-106 at several different energies around the Coulomb barrier. The difficulties that arise in the study of Cd-106-alpha-nuclear potential and the so called Family Problem are addressed

How important is the Family? : Alpha nuclear potentials and p-process nucleosynthesis

Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike LicenceIn this work we present the results from the analysis of the experimentally measured angular distributions of the reaction 106Cd(α , α )106 Cd at several different energies around the Coulomb barrier. The difficulties that arise in the study of 106Cd-α -nuclear potential and the so called Family Problem are addressed in this work

Cross section measurement of the astrophysically important 17O(p,gamma)18F reaction in a wide energy range

The 17O(p,g)18F reaction plays an important role in hydrogen burning processes in different stages of stellar evolution. The rate of this reaction must therefore be known with high accuracy in order to provide the necessary input for astrophysical models. The cross section of 17O(p,g)18F is characterized by a complicated resonance structure at low energies. Experimental data, however, is scarce in a wide energy range which increases the uncertainty of the low energy extrapolations. The purpose of the present work is therefore to provide consistent and precise cross section values in a wide energy range. The cross section is measured using the activation method which provides directly the total cross section. With this technique some typical systematic uncertainties encountered in in-beam gamma-spectroscopy experiments can be avoided. The cross section was measured between 500 keV and 1.8 MeV proton energies with a total uncertainty of typically 10%. The results are compared with earlier measurements and it is found that the gross features of the 17O(p,g)18F excitation function is relatively well reproduced by the present data. Deviation of roughly a factor of 1.5 is found in the case of the total cross section when compared with the only one high energy dataset. At the lowest measured energy our result is in agreement with two recent datasets within one standard deviation and deviates by roughly two standard deviations from a third one. An R-matrix analysis of the present and previous data strengthen the reliability of the extrapolated zero energy astrophysical S-factor. Using an independent experimental technique, the literature cross section data of 17O(p,g)18F is confirmed in the energy region of the resonances while lower direct capture cross section is recommended at higher energies. The present dataset provides a constraint for the theoretical cross sections.Comment: Accepted for publication in Phys. Rev. C. Abstract shortened in order to comply with arxiv rule

Parameter estimation and model selection for stochastic differential equations for biological growth

In this paper, we consider stochastic versions of three classical growth models given by ordinary differential equations (ODEs). Indeed we use stochastic versions of Von Bertalanffy, Gompertz, and Logistic differential equations as models. We assume that each stochastic differential equation (SDE) has some crucial parameters in the drift to be estimated and we use the Maximum Likelihood Estimator (MLE) to estimate them. For estimating the diffusion parameter, we use the MLE for two cases and the quadratic variation of the data for one of the SDEs. We apply the Akaike information criterion (AIC) to choose the best model for the simulated data. We consider that the AIC is a function of the drift parameter. We present a simulation study to validate our selection method. The proposed methodology could be applied to datasets with continuous and discrete observations, but also with highly sparse data. Indeed, we can use this method even in the extreme case where we have observed only one point for each path, under the condition that we observed a sufficient number of trajectories. For the last two cases, the data can be viewed as incomplete observations of a model with a tractable likelihood function; then, we propose a version of the Expectation Maximization (EM) algorithm to estimate these parameters. This type of datasets typically appears in fishery, for instance

The EXPLORE Project I: A Deep Search for Transiting Extrasolar Planets

(Abridged) We discuss the design considerations of the EXPLORE (EXtra-solar PLanet Occultation REsearch) project, a series of transiting planet searches using 4-m-class telescopes to continuously monitor a single field of stars in the Galactic Plane in each ~2 week observing campaign. We discuss the general factors which determine the efficiency and the number of planets found by a transit search, including time sampling strategy and field selection. The primary goal is to select the most promising planet candidates for radial velocity follow-up observations. We show that with very high photometric precision light curves that have frequent time sampling and at least two detected transits, it is possible to uniquely solve for the main parameters of the eclipsing system (including planet radius) based on several important assumptions about the central star. Together with a measured spectral type for the star, this unique solution for orbital parameters provides a powerful method for ruling out most contaminants to transiting planet candidates. For the EXPLORE project, radial velocity follow-up observations for companion mass determination of the best candidates are done on 8-m-class telescopes within two or three months of the photometric campaigns. This same-season follow-up is made possible by the use of efficient pipelines to produce high quality light curves within weeks of the observations. We conclude by presenting early results from our first search, EXPLORE I, in which we reached <1% rms photometric precision (measured over a full night) on ~37,000 stars to I <= 18.2.Comment: accepted by ApJ. Main points unchanged but more thorough discussion of some issues. 36 pages, including 14 figure

Y-chromosomal diversity in the population of Guinea-Bissau: a multiethnic perspective

<p>Abstract</p> <p>Background</p> <p>The geographic and ethnolinguistic differentiation of many African Y-chromosomal lineages provides an opportunity to evaluate human migration episodes and admixture processes, in a pan-continental context. The analysis of the paternal genetic structure of Equatorial West Africans carried out to date leaves their origins and relationships unclear, and raises questions about the existence of major demographic phenomena analogous to the large-scale Bantu expansions. To address this, we have analysed the variation of 31 binary and 11 microsatellite markers on the non-recombining portion of the Y chromosome in Guinea-Bissau samples of diverse ethnic affiliations, some not studied before.</p> <p>Results</p> <p>The Guinea-Bissau Y chromosome pool is characterized by low haplogroup diversity (D = 0.470, sd 0.033), with the predominant haplogroup E3a*-M2 shared among the ethnic clusters and reaching a maximum of 82.2% in the Mandenka people. The Felupe-Djola and Papel groups exhibit the highest diversity of lineages and harbor the deep-rooting haplogroups A-M91, E2-M75 and E3*-PN2, typical of Sahel's more central and eastern areas. Their genetic distinction from other groups is statistically significant (P = 0.01) though not attributable to linguistic, geographic or religious criteria. Non sub-Saharan influences were associated with the presence of haplogroup R1b-P25 and particular lineages of E3b1-M78.</p> <p>Conclusion</p> <p>The predominance and high diversity of haplogroup E3a*-M2 suggests a demographic expansion in the equatorial western fringe, possibly supported by a local agricultural center. The paternal pool of the Mandenka and Balanta displays evidence of a particularly marked population growth among the Guineans, possibly reflecting the demographic effects of the agriculturalist lifestyle and their putative relationship to the people that introduced early cultivation practices into West Africa. The paternal background of the Felupe-Djola and Papel ethnic groups suggests a better conserved ancestral pool deriving from East Africa, from where they have supposedly migrated in recent times. Despite the overall homogeneity in a multiethnic sample, which contrasts with their social structure, minor clusters suggest the imprints of multiple peoples at different timescales: traces of ancestral inhabitants in haplogroups A-M91 and B-M60, today typical of hunter-gatherers; North African influence in E3b1-M78 Y chromosomes, probably due to trans-Saharan contacts; and R1b-P25 lineages reflecting European admixture via the North Atlantic slave trade.</p