Insights on the physics of SNIa obtained from their gamma-ray emission

Type Ia supernovae are thought to be the outcome of the thermonuclear explosion of a carbon/oxygen white dwarf in a close binary system. Their optical light curve is powered by thermalized gamma-rays produced by the radioactive decay of $^{56}$Ni, the most abundant isotope present in the debris. Gamma-rays escaping the ejecta can be used as a diagnostic tool for studying the structure of the exploding star and the characteristics of the explosion. The fluxes of the $^{56}$Ni lines and the continuum obtained by INTEGRAL from SN2014J in M82, the first ever gamma-detected SNIa, around the time of the maximum of the optical light curve strongly suggest the presence of a plume of $^{56}$Ni in the outermost layers moving at high velocities. If this interpretation was correct, it could have important consequences on our current understanding of the physics of the explosion and on the nature of the systems that explode.Comment: Proceedings of the 11th INTEGRAL Conference Gamma-Ray AStrophysics in Multi-Wavelength Perspectiv

The Persistence of Memory, or How the X-Ray Spectrum of SNR 0509-67.5 Reveals the Brightness of its Parent Type Ia Supernova

We examine the dynamics and X-ray spectrum of the young Type Ia supernova remnant 0509-67.5 in the context of the recent results obtained from the optical spectroscopy of its light echo. Our goal is to estimate the kinetic energy of the supernova explosion using Chandra and XMM-Newton observations of the supernova remnant, thus placing the birth event of 0509-67.5 in the sequence of dim to bright Type Ia supernovae. We base our analysis on a standard grid of one-dimensional delayed detonation explosion models, together with hydrodynamic and X-ray spectral calculations of the supernova remnant evolution. From the remnant dynamics and the properties of the O, Si, S, and Fe emission in its X-ray spectrum we conclude that 0509-67.5 was originated ~400 years ago by a bright, highly energetic Type Ia explosion similar to SN 1991T. Our best model has a kinetic energy of 1.4x10E51 erg and synthesizes 0.97 Msun of 56Ni. These results are in excellent agreement with the age estimate and spectroscopy from the light echo. We have thus established the first connection between a Type Ia supernova and its supernova remnant based on a detailed quantitative analysis of both objects.Comment: 10 pages, 9 figures, plus an exclusive astro-ph-only Appendix; ApJ in press, companion paper to Rest et al. 0

Quantum Mechanical Corrections to the Schwarzschild Black Hole Metric

Motivated by quantum mechanical corrections to the Newtonian potential, which can be translated into an $\hbar$-correction to the $g_{00}$ component of the Schwarzschild metric, we construct a quantum mechanically corrected metric assuming $-g_{00}=g^{rr}$. We show how the Bekenstein black hole entropy $S$ receives its logarithmic contribution provided the quantum mechanical corrections to the metric are negative. In this case the standard horizon at the Schwarzschild radius $r_S$ increases by small terms proportional to $\hbar$ and a remnant of the order of Planck mass emerges. We contrast these results with a positive correction to the metric which, apart from a corrected Schwarzschild horizon, leads to a new purely quantum mechanical horizon.Comment: 14 pages Latex, enlarged version as compared to the published on

Can mHealth Improve Risk Assessment in Underserved Populations? Acceptability of a Breast Health Questionnaire App in Ethnically Diverse, Older, Low-Income Women.

Background: Use of mobile health (mHealth) tools has expanded rapidly but little research has been done on its acceptability by low-income, diverse, older patient populations. Objective: To assess the attitudes of a diverse group of underserved women on the acceptability and usability of mHealth tools in a clinical setting using a breast health questionnaire application (app) at a public hospital mammography clinic. Methods: Semi-structured interviews were conducted in a breast-imaging center of an urban safety net institution from July-August 2012. Interviews included pre- and post-questions. Women completed the Athena breast health questionnaire app on an iPad and were asked about their experience and ways to improve the tool. Results: Fifteen women age 45-75 years from diverse ethnic and educational backgrounds were interviewed. The majority of women, 11 of 15, preferred the Athena app over a paper version and all the women thought the app was easy to use. Two Spanish-speaking Latinas preferred paper; and two women, with limited mobile phone use, did not have a preference. Many women indicated that it would be necessary to have staff available for instruction and assistance if the app were to be implemented. Conclusions: mHealth tools are an acceptable, if not preferred, method of collecting health information for diverse, older, low-income women. Further studies are required to evaluate the reliability and accuracy of data collection using mHealth tools in underserved populations. mHealth tools should be explored as a novel way to engage diverse populations to improve clinical care and bridge gaps in health disparities

Explosion of white dwarfs harboring hybrid CONe cores

Recently, it has been found that off-centre carbon burning in a subset of intermediate-mass stars does not propagate all the way to the center, resulting in a class of hybrid CONe cores. Here, we consider the possibility that stars hosting these hybrid CONe cores might belong to a close binary system and, eventually, become white dwarfs accreting from a non-degenerate companion at rates leading to a supernova explosion. We have computed the hydrodynamical phase of the explosion of Chandrasekhar-mass white dwarfs harboring hybrid cores, assuming that the explosion starts at the center, either as a detonation (as may be expected in some degenerate merging scenarios) or as a deflagration (that afterwards transitions into a delayed detonation). We assume these hybrid cores are made of a central CO volume, of mass M(CO), surrounded by an ONe shell. We show that, in case of a pure detonation, a medium-sized CO-rich region, M(CO)<0.4 Msun, results in the ejection of a small fraction of the mantle while leaving a massive bound remnant. Part of this remnant is made of the products of the detonation, Fe-group nuclei, but they are buried in its inner regions, unless convection is activated during the ensuing cooling and shrinking phase of the remnant. In contrast, and somehow paradoxically, delayed detonations do not leave remnants but for the minimum M(CO) we have explored, M(CO)=0.2 Msun, and even in this case the remnant is as small as 0.13 Msun. The ejecta produced by these delayed detonations are characterized by slightly smaller masses of 56Ni and substantially smaller kinetic energies than obtained for a delayed detonation of a 'normal' CO white dwarf. The optical emission expected from these explosions would hardly match the observational properties of typical Type Ia supernovae, although they make interesting candidates for the subluminous class of SN2002cx-like or SNIax.Comment: Accepted for Astronomy and Astrophysics, 11 pages, 4 figure

Exploring the Physics of Type Ia Supernovae Through the X-ray Spectra of their Remnants

We present the results of an ongoing project to use the X-ray observations of Type Ia Supernova Remnants to constrain the physical processes involved in Type Ia Supernova explosions. We use the Tycho Supernova Remnant (SN 1572) as a benchmark case, comparing its observed spectrum with models for the X-ray emission from the shocked ejecta generated from different kinds of Type Ia explosions. Both the integrated spectrum of Tycho and the spatial distribution of the Fe and Si emission in the remnant are well reproduced by delayed detonation models with stratified ejecta. All the other Type Ia explosion models fail, including well-mixed deflagrations calculated in three dimensions.Comment: 5 pages, 3 figures, to appear in the proceedings of the "Stellar end products" workshop, 13-15 April 2005, Granada, Spain, ed. M.A. Perez-Torres, Vol. 77 (Jan 2006) of MmSA

Wavelets: a powerful tool for studying rotation, activity, and pulsation in Kepler and CoRoT stellar light curves

Aims. The wavelet transform has been used as a powerful tool for treating several problems in astrophysics. In this work, we show that the time-frequency analysis of stellar light curves using the wavelet transform is a practical tool for identifying rotation, magnetic activity, and pulsation signatures. We present the wavelet spectral composition and multiscale variations of the time series for four classes of stars: targets dominated by magnetic activity, stars with transiting planets, those with binary transits, and pulsating stars. Methods. We applied the Morlet wavelet (6th order), which offers high time and frequency resolution. By applying the wavelet transform to the signal, we obtain the wavelet local and global power spectra. The first is interpreted as energy distribution of the signal in time-frequency space, and the second is obtained by time integration of the local map. Results. Since the wavelet transform is a useful mathematical tool for nonstationary signals, this technique applied to Kepler and CoRoT light curves allows us to clearly identify particular signatures for different phenomena. In particular, patterns were identified for the temporal evolution of the rotation period and other periodicity due to active regions affecting these light curves. In addition, a beat-pattern signature in the local wavelet map of pulsating stars over the entire time span was also detected.Comment: Accepted for publication on A&

An Empirical Study of Earnings of Immigrants and Native-Born Americans in the U.S. Labor Market Given Different Levels of Educational Attainment

This paper will compare the Lifetime wage earnings of immigrants and native-born citizens in the U.S. for the years 2000-2010 according to educational attainment using cross-sectional data. The data obtained through IPUMS-CPS Integrated Public Use of Microdata Series, University of Minnesota. The findings of investment in Human Capital of Mincer (1958), the Immigrants earnings distribution of Chiswick and Miller (2006), the Pareto’s law of income distribution, and the immigrants investment in human capital model by Duleep and Regets (1999) are the theoretical basis in which this study will be ruled. The empirical evidence suggests that immigrants who invest in education have closer Lifetime income earnings in the higher income distribution levels to the US native-born citizens than those who do not. It also shows that according to age, the average wage earnings will increase rapidly the first working years, settle by the middle, and decrease at the end for all the educational attainment levels

Properties of Deflagration Fronts and Models for Type Ia Supernovae

Detailed models of the explosion of a white dwarf, which include self-consistent calculations of the light curve and spectra, provide a link between observational quantities and the underlying explosion.These calculations assume spherical geometry and are based on parameterized descriptions of the burning front during the deflagration phase. Recently, first multi-dimensional calculations for nuclear burning fronts have been performed. Although a fully consistent treatment of the burning fronts is beyond the current state of the art, these calculations provided a new and better understanding of the physics, and new descriptions for the flame propagation have been proposed. Here, we have studied the influence on the results of previous analyses of Type Ia Supernovae, namely, the nucleosynthesis and structure of the expanding envelope. Our calculations are based on a set of delayed detonation models with parameters that give a good account of the optical and infrared light curves, and of the spectral evolution. In this scenario, the burning front propagates first in a deflagration mode and, subsequently, turns into a detonation. The explosions and light curves are calculated using a one-dimensional Lagrangian radiation-hydro code, including a detailed nuclear network.Comment: 9 pages, 4 figures, macros 'crckapb.sty'. The Astrophysical Journal (accepted