Burst Neutrinos from Nitrogen Flash

Neutrinos give a novel probe to explore deep interior of astrophysical objects, which otherwise is not accessible with optical observations; among notable examples are solar and supernova neutrinos. We show that there is a new class of strong neutrino emission from helium burning, N + alpha --> 18F gamma followed by beta decay 18F --> 18O + e+ + nu_e, that gives a maximum neutrino luminosity of 10^8 times the solar bolometric luminosity at the helium-core flash of a 1 M_sun star, whereas the flash is not observable by optical means. This means that the neutrino flux, of average energy of 0.382 MeV, will be 10% the solar CNO neutrino flux on Earth if the star is located at 10pc.Comment: Accepted to ApJ Letters. Replaced version with extended discussion. Some additional references adde

Solar Neutrinos

The study of solar neutrinos has given since ever a fundamental contribution both to astroparticle and to elementary particle physics, offering an ideal test of solar models and offering at the same time relevant indications on the fundamental interactions among particles. After reviewing the striking results of the last two decades, which were determinant to solve the long standing solar neutrino puzzle and refine the Standard Solar Model, we focus our attention on the more recent results in this field and on the experiments presently running or planned for the near future. The main focus at the moment is to improve the knowledge of the mass and mixing pattern and especially to study in detail the lowest energy part of the spectrum, which represents most of solar neutrino spectrum but is still a partially unexplored realm. We discuss this research project and the way in which present and future experiments could contribute to make the theoretical framemork more complete and stable, understanding the origin of some "anomalies" that seem to emerge from the data and contributing to answer some present questions, like the exact mechanism of the vacuum to matter transition and the solution of the so called solar metallicity problem.Comment: 51 pages, to be published in Special Issue on Neutrino Physics, Advances in High Energy Physics Hindawi Publishing Corporation 201

Bayesian mass and age estimates for transiting exoplanet host stars

The mean density of a star transited by a planet, brown dwarf or low mass star can be accurately measured from its light curve. This measurement can be combined with other observations to estimate its mass and age by comparison with stellar models. Our aim is to calculate the posterior probability distributions for the mass and age of a star given its density, effective temperature, metallicity and luminosity. We computed a large grid of stellar models that densely sample the appropriate mass and metallicity range. The posterior probability distributions are calculated using a Markov-chain Monte-Carlo method. The method has been validated by comparison to the results of other stellar models and by applying the method to stars in eclipsing binary systems with accurately measured masses and radii. We have explored the sensitivity of our results to the assumed values of the mixing-length parameter, $\alpha_{\rm MLT}$, and initial helium mass fraction, Y. For a star with a mass of 0.9 solar masses and an age of 4 Gyr our method recovers the mass of the star with a precision of 2% and the age to within 25% based on the density, effective temperature and metallicity predicted by a range of different stellar models. The masses of stars in eclipsing binaries are recovered to within the calculated uncertainties (typically 5%) in about 90% of cases. There is a tendency for the masses to be underestimated by about 0.1 solar masses for some stars with rotation periods P$_{\rm rot}< 7$d. Our method makes it straightforward to determine accurately the joint posterior probability distribution for the mass and age of a star eclipsed by a planet or other dark body based on its observed properties and a state-of-the art set of stellar models.Comment: Accepted for publication in A&A. 9 pages, 4 figures. Source code for the software described is available from http://sourceforge.net/projects/bagemas

On constructing horizontal branch models

We investigate different methods used to construct (zero-age) horizontal branch models and compare the resulting horizontal branch evolution with that of models resulting from the calculation of the complete stellar evolution from the main sequence and through the core helium flash. We show that the approximate methods may lead to small, but discernible effects, but that some methods, which are as simple, reproduce the complete evolution very well.Comment: accepted for publication in Astronomy & Astrophysic

New DA white dwarf evolutionary models and their pulsational properties

In this letter we investigate the pulsational properties of ZZ Ceti stars on the basis of new white dwarf evolutionary models calculated in a self-consistent way with the predictions of time dependent element diffusion and nuclear burning. In addition, full account is taken of the evolutionary stages prior to the white dwarf formation. Emphasis is placed on the trapping properties of such models. By means of adiabatic, non-radial pulsation calculations, we find, as a result of time dependent diffusion, a much weaker mode trapping effect, particularly for the high-period regime of the pulsation g-spectrum. This result is valid at least for models with massive hydrogen-rich envelopes. Thus, mode trapping would not be an effective mechanism to explain the fact that all the high periods expected from standard models of stratified white dwarfs are not observed in the ZZ Ceti stars.Comment: 3 pages, 5 figures, accepted for publication in Astronomy & Astrophysics Letter

PENGARUH ATRIBUT PRODUK TERHADAP SIKAP KONSUMEN INEZ KOSMETIK (Studi Kasus di Pusaka Indah Swalayan Kebumen Tahun 2013)

Penelitian ini bertujuan untuk mengetahui (1) Ada tidaknya pengaruh atribut produk secara simultan terhadap sikap konsumen Inez kosmetik di Pusaka Indah Swalayan, (2) Ada tidaknya pengaruh atribut produk terhadap sikap konsumen Inez kosmetik di Pusaka Indah Swalayan. Jenis penelitian yang digunakan oleh penulis untuk memenuhi tujuan tersebut adalah menggunakan metode deskriptif kuantitatif dengan teknik pengumpulan data berupa kuesioner. Populasi penelitian ini adalah orang yang membeli dan menggunakan Inez Kosmetik atau konsumen yang memiliki minat terhadap Inez Kosmetik di Pusaka Indah Swalayan. Jumlah sampel yang digunakan dalam penelitian ini sebanyak 100 responden. Teknis analisis data yang digunakan adalah teknik analisis regresi linier berganda. Berdasarkan hasil penelitian tersebut dapat disimpulkan bahwa (1) terdapat pengaruh atribut produk terhadap sikap konsumen Inez kosmetik di Pusaka Indah Swalayan. Hal tersebut tercermin dari hasil uji F diperoleh nilai probabilitas sebesar 0,000. Sehubungan dengan nilai probabilitas 0,000 lebih kecil dari 0,05, maka Ho ditolak dan Ha diterima, sehingga dapat disimpulkan bahwa variabel atirbut produk yang terdiri dari yang terdiri dari : kualitas, merek, kemasan, label dan harga berpengaruh secara simultan terhadap sikap konsumen. (2) hasil perhitungan data untuk variabel kualitas memiliki tingkat signifikansi sebesar 0,035, variabel merek memiliki tingkat signifikansi sebesar 0,027, variabel kemasan memiliki tingkat signifikansi sebesar 0,039, variabel label memiliki tingkat signifikansi sebesar 0,038, variabel harga memiliki tingkat signifikansi sebesar 0,023 . Oleh karena probabilitas variabel kualitas, merek, kemasan, label, dan harga lebih kecil dari 0,05 maka dapat dikemukakan bahwa variabel variabel kualitas, merek, kemasan, label, dan harga berpengaruh secara parsial terhadap keputusan pembelian konsumen. Kata kunci: Atribut produk, sikap konsumen, kosmeti

The ages and colours of cool helium-core white dwarf stars

The purpose of this work is to explore the evolution of helium-core white dwarf stars in a self-consistent way with the predictions of detailed non-gray model atmospheres and element diffusion. To this end, we consider helium-core white dwarf models with stellar masses of 0.406, 0.360, 0.327, 0.292, 0.242, 0.196 and 0.169 solar masses and follow their evolution from the end of mass loss episodes during their pre-white dwarf evolution down to very low surface luminosities. We find that when the effective temperature decreases below 4000K, the emergent spectrum of these stars becomes bluer within time-scales of astrophysical interest. In particular, we analyse the evolution of our models in the colour-colour and colour-magnitude diagrams and we find that helium-core white dwarfs with masses ranging from approx. 0.18 to 0.3 solar masses can reach the turn-off in their colours and become blue again within cooling times much less than 15 Gyr and then remain brighter than M_V approx. 16.5. In view of these results, many low-mass helium white dwarfs could have had time enough to evolve to the domain of collision-induced absorption from molecular hydrogen, showing blue colours.Comment: 11 pages, 9 figures. Accepted for publication in MNRA