Further constraints on the optical transmission spectrum of HAT-P-1b

We report on novel observations of HAT-P-1 aimed at constraining the optical transmission spectrum of the atmosphere of its transiting Hot-Jupiter exoplanet. Ground-based differential spectrophotometry was performed over two transit windows using the DOLORES spectrograph at the Telescopio Nazionale Galileo (TNG). Our measurements imply an average planet to star radius ratio equal to $\rm R_p/R_{\star}$=(0.1159$\pm$0.0005). This result is consistent with the value obtained from recent near infrared measurements of this object but differs from previously reported optical measurements being lower by around 4.4 exoplanet scale heights. Analyzing the data over 5 different spectral bins 600\AA$\,$ wide we observed a single peaked spectrum (3.7 $\rm\sigma$ level) with a blue cut-off corresponding to the blue edge of the broad absorption wing of sodium and an increased absorption in the region in between 6180-7400\AA. We also infer that the width of the broad absorption wings due to alkali metals is likely narrower than the one implied by solar abundance clear atmospheric models. We interpret the result as evidence that HAT-P-1b has a partially clear atmosphere at optical wavelengths with a more modest contribution from an optical absorber than previously reported.Comment: Accepted by Ap

Segmentazione delle serie temporali nell’analisi dei dati: un esempio di applicazione a dati sismo-vulcanici.

Il presente report descrive quanto sviluppato dagli autori per l’analisi delle serie temporali utilizzate per il monitoraggio sismo-vulcanico del vulcano Etna. La necessità di ottenere una rappresentazione ridotta delle serie temporali ha portato alla ricerca ed alla implementazione degli algoritmi di segmentazione oggetto del presente lavoro. Le metodologie introdotte nel paragrafo 2, largamente applicate nella disciplina del data mining su serie temporali, costituiscono ad oggi lo stato dell’arte per quanto riguarda le tecniche di approssimazione di serie temporali. In particolare, l’applicazione dell’algoritmo bottom-up ha permesso una compressione elevata dei dati, consentendo quindi una rappresentazione con un numero di punti inferiore rispetto a quello delle serie temporali di partenza. In questo contesto la scelta delle soglie errore, legata indirettamente al numero di segmenti con cui si approssima la serie temporale, è stata scelta in modo empirico. Questa scelta è stata vincolata alla dimensione dei buffer di dati da impiegare per scopi di visualizzazione ed elaborazione. Future implementazioni riguarderanno l’ottimizzazione in linea degli algoritmi Sliding Window in modo da operare in real-time sugli streaming di dati ed ottimizzarne l’archiviazione e la visualizzazione

Current status of laboratory and imaging diagnosis of neonatal necrotizing enterocolitis

Necrotizing enterocolitis continues to be a devastating disease process for very low birth weight infants in Neonatal Intensive Care Units. The aetiology and pathogenesis of necrotizing enterocolitis are not definitively understood. It is known that necrotizing enterocolitis is secondary to a complex interaction of multiple factors that results in mucosal damage, which leads to intestinal ischemia and necrosis. Advances in neonatal care, including resuscitation and ventilation support technology, have seen increased survival rates among premature neonates and a concomitant detection in the incidence of this intestinal disease.Diagnosis can be difficult, and identifying infants at the onset of disease remains a challenge. Early diagnosis, which relies on imaging findings, and initiation of prompt therapy are essential to limit morbidity and mortality. Moreover, early management is critical and life-saving.This review summarizes what is known on the laboratory and instrumental diagnostic strategies needed to improve neonatal outcomes and, possibily, to prevent the onset of an overt necrotizing enterocolitis

Evidence for a spectroscopic direct detection of reflected light from 51 Peg b

The detection of reflected light from an exoplanet is a difficult technical challenge at optical wavelengths. Even though this signal is expected to replicate the stellar signal, not only is it several orders of magnitude fainter, but it is also hidden among the stellar noise. We apply a variant of the cross-correlation technique to HARPS observations of 51 Peg to detect the reflected signal from planet 51 Peg b. Our method makes use of the cross-correlation function of a binary mask with high-resolution spectra to amplify the minute planetary signal that is present in the spectra by a factor proportional to the number of spectral lines when performing the cross correlation. The resulting cross-correlation functions are then normalized by a stellar template to remove the stellar signal. Carefully selected sections of the resulting normalized CCFs are stacked to increase the planetary signal further. The recovered signal allows probing several of the planetary properties, including its real mass and albedo. We detect evidence for the reflected signal from planet 51 Peg b at a significance of 3\sigma_noise. The detection of the signal permits us to infer a real mass of 0.46^+0.06_-0.01 M_Jup (assuming a stellar mass of 1.04\;M_Sun) for the planet and an orbital inclination of 80^+10_-19 degrees. The analysis of the data also allows us to infer a tentative value for the (radius-dependent) geometric albedo of the planet. The results suggest that 51Peg b may be an inflated hot Jupiter with a high albedo (e.g., an albedo of 0.5 yields a radius of 1.9 \pm 0.3 R_Jup for a signal amplitude of 6.0\pm0.4 x 10^-5). We confirm that the method we perfected can be used to retrieve an exoplanet's reflected signal, even with current observing facilities. The advent of next generation of observing facilities will yield new opportunities for this type of technique to probe deeper into exoplanets.Comment: 9 pages, 6 figure

Towards an automatic monitoring system of infrasonic events at Mt. Etna: strategies for source location and modelling

Active volcanoes characterized by open conduit conditions generate sonic and infrasonic signals, whose investigation provides useful information for both monitoring purposes and studying the dynamics of explosive processes. In this work, we discuss the automatic procedures implemented for a real-time application to the data acquired by a permanent network of five infrasound stations running at Mt. Etna volcano. The infrasound signals at Mt. Etna consist in amplitude transients, called infrasound events. The adopted procedure uses a multi-algorithm approach for event detection, counting, characterization and location. It is designed for an efficient and accurate processing of infrasound records provided by single-site and array stations. Moreover, the source mechanism of these events can be investigated off-line or in near real-time by using three different models: i) Strombolian bubble; ii) resonating conduit and iii) Helmholtz resonator. The infrasound waveforms allow us to choose the most suitable model, to get quantitative information about the source and to follow the time evolution of the source parameters

College Student Debt and Anticipated Repayment Difficulty

This study analyzes factors associated with anticipated difficulty with repayment of debt accumulated during college using a basic model of credit risk that includes socialization processes influencing college student financial decisions. The empirical analysis uses data from the 2010 Ohio Student Financial Wellness Study. Results provide evidence of male overconfidence in financial decision making, as males are less likely than females to predict repayment difficulties. Socialization process variables, including financial management practices, financial parenting communication, and expected economic returns from education, are strongly associated with anticipated debt repayment difficulty. Inclusion of these process variables in the model results in loss of explanatory power of many of the traditional individual success variables, such as grade point average, and graduation plans

A new analysis of the WASP-3 system: no evidence for an additional companion

In this work we investigate the problem concerning the presence of additional bodies gravitationally bounded with the WASP-3 system. We present eight new transits of this planet and analyse all the photometric and radial velocity data published so far. We did not observe significant periodicities in the Fourier spectrum of the observed minus calculated (O-C) transit timing and radial velocity diagrams (the highest peak having false-alarm probabilities of 56 per cent and 31 per cent, respectively) or long-term trends. Combining all the available information, we conclude that the radial velocity and transit timing techniques exclude, at 99 per cent confidence limit, any perturber more massive than M \gtrsim 100 M_Earth with periods up to 10 times the period of the inner planet. We also investigate the possible presence of an exomoon on this system and determined that considering the scatter of the O-C transit timing residuals a coplanar exomoon would likely produce detectable transits. This hypothesis is however apparently ruled out by observations conducted by other researchers. In case the orbit of the moon is not coplanar the accuracy of our transit timing and transit duration measurements prevents any significant statement. Interestingly, on the basis of our reanalysis of SOPHIE data we noted that WASP-3 passed from a less active (log R'_hk=-4.95) to a more active (log R'_hk=-4.8) state during the 3 yr monitoring period spanned by the observations. Despite no clear spot crossing has been reported for this system, this analysis claims for a more intensive monitoring of the activity level of this star in order to understand its impact on photometric and radial velocity measurements.Comment: MNRAS accepted (14/08/2012

The old and heavy bulge of M31 I. Kinematics and stellar populations

We present new optical long-slit data along 6 position angles of the bulge region of M31. We derive accurate stellar and gas kinematics reaching 5 arcmin from the center, where the disk light contribution is always less than 30%, and out to 8 arcmin along the major axis, where the disk makes 55% of the total light. We show that the velocity dispersions of McElroy (1983) are severely underestimated (by up to 50 km/s) and previous dynamical models have underestimated the stellar mass of M31's bulge by a factor 2. Moreover, the light-weighted velocity dispersion of the galaxy grows to 166 km/s, thus reducing the discrepancy between the predicted and measured mass of the black hole at the center of M31. The kinematic position angle varies with distance, pointing to triaxiality. We detect gas counterrotation near the bulge minor axis. We measure eight emission-corrected Lick indices. They are approximately constant on circles. We derive the age, metallicity and alpha-element overabundance profiles. Except for the region in the inner arcsecs of the galaxy, the bulge of M31 is uniformly old (>12 Gyr, with many best-fit ages at the model grid limit of 15 Gyr), slightly alpha-elements overabundant ([alpha/Fe]~0.2) and at solar metallicity, in agreement with studies of the resolved stellar components. The predicted u-g, g-r and r-i Sloan color profiles match reasonably well the dust-corrected observations. The stellar populations have approximately radially constant mass-to-light ratios (M/L_R ~ 4-4.5 for a Kroupa IMF), in agreement with stellar dynamical estimates based on our new velocity dispersions. In the inner arcsecs the luminosity-weighted age drops to 4-8 Gyr, while the metallicity increases to above 3 times the solar value.Comment: Accepted for publication in A&

PYDBSCAN UN SOFTWARE PER IL CLUSTERING DI DATI

Con il termine clustering si indica il processo mediante il quale è possibile raggruppare oggetti in base a caratteristiche comuni (features). Questo approccio, alla base dei processi di estrazione di conoscenza da insiemi di dati (data mining), riveste notevole importanza nelle tecniche di analisi. Come verrà mostrato in questo lavoro, l’applicazione delle tecniche di clustering consente di analizzare dataset, con l’obiettivo di ricercare strutture che possano fornire informazioni utili circa i dati oggetto dello studio. Gli ambiti in cui tali algoritmi sono impiegati risultano essere eterogenei, a partire dalle analisi di dati biomedici, astrofisici, biologici, fino ad arrivare a quelli geofisici. La letteratura è ricca di vari casi di studio, dai quali il ricercatore può trarre spunto e adattare i differenti approcci alle proprie esigenze. Il software PyDBSCAN, oggetto del presente lavoro, permette di applicare tecniche di clustering basate sul concetto di densità, applicate ad oggetti (o punti) appartenenti ad insiemi definiti in uno spazio metrico. L’algoritmo di base è il DBSCAN (Density Based Spatial Clustering on Application with Noise) [Ester et al., 1996], di cui viene riportata una implementazione ottimizzata al fine di migliorare la qualità del processamento dei dati. Schematicamente, il sistema proposto può essere rappresentato come in Fig. 1. Il software, sviluppato in Python 2.6 [Python ref.], utilizza le librerie scientifiche Numpy [Numpy ref.], Matplotlib [matplotlib ref.] e la libreria grafica PyQt [PyQt ref.] impiegata nella realizzazione dell’interfaccia utente. Python è un linguaggio di programmazione che permette la realizzazione di applicazioni crossplatform in grado di funzionare su diversi sistemi operativi quali Windows, Unix, Linux e Mac OS. Nella prima parte del lavoro verranno brevemente descritte le tecniche oggetto del software presentato, mentre nella seconda parte verrà descritto un esempio di applicazione su dati reali