Study of extremely reddened AGB stars in the Galactic bulge

Context. Extremely reddened AGB stars lose mass at high rates of >10^-5 Msun/yr. This is the very last stage of AGB evolution, in which stars in the mass range 2.0--4.0 Msun (for solar metallicity) should have been converted to C stars already. The extremely reddened AGB stars in the Galactic bulge are however predominantly O-rich, implying that they might be either low-mass stars or stars at the upper end of the AGB mass range. Aims. To determine the mass range of the most reddened AGB stars in the Galactic bulge. Methods. Using Virtual Observatory tools, we constructed spectral energy distributions of a sample of 37 evolved stars in the Galactic bulge with extremely red IRAS colours. We fitted DUSTY models to the observational data to infer the bolometric fluxes. Applying individual corrections for interstellar extinction and adopting a common distance, we determined luminosities and mass-loss rates, and inferred the progenitor mass range from comparisons with AGB evolutionary models. Results. The observed spectral energy distributions are consistent with a classification as reddened AGB stars, except for two stars, which are proto-planetary nebula candidates. For the AGB stars, we found luminosities in the range 3000--30,000 Lsun and mass-loss rates 10^-5--3x10^-4 Msun/yr. The corresponding mass range is 1.1--6.0 Msun assuming solar metallicity. Conclusions. Contrary to the predictions of the evolutionary models, the luminosity distribution is continuous, with many O-rich AGB stars in the mass range in which they should have been converted into C stars already. We suspect that bulge AGB stars have higher than solar metallicity and therefore may avoid the conversion to C-rich. The presence of low-mass stars in the sample shows that their termination of the AGB evolution also occurs during a final phase of very high mass-loss rate, leading to optically thick circumstellar shells

The onset of solar cycle 24: What global acoustic modes are telling us

We study the response of the low-degree, solar p-mode frequencies to the unusually extended minimum of solar surface activity since 2007. A total of 4768 days of observations collected by the space-based, Sun-as-a-star helioseismic GOLF instrument are analyzed. A multi-step iterative maximum-likelihood fitting method is applied to subseries of 365 days and 91.25 days to extract the p-mode parameters. Temporal variations of the l=0, 1, and 2 p-mode frequencies are then obtained from April 1996 to May 2009. While the p-mode frequency shifts are closely correlated with solar surface activity proxies during the past solar cycles, the frequency shifts of the l=0 and l=2 modes show an increase from the second half of 2007, when no significant surface activity is observable. On the other hand, the l=1 modes follow the general decreasing trend of the solar surface activity. The different behaviours between the l=0 and l=2 modes and the l=1 modes can be interpreted as different geometrical responses to the spatial distribution of the solar magnetic field beneath the surface of the Sun. The analysis of the low-degree, solar p-mode frequency shifts indicates that the solar activity cycle 24 started late 2007, despite the absence of activity on the solar surface.Comment: To be accepted by A&A (with minor revisions), 4 pages, 3 figures, 1 tabl

Radiative decays of dynamically generated charmed baryons

In this work we study the radiative decay of dynamically generated J^P=\oh^- charm baryons into the ground state J^P=\oh^+ baryons. Since different theoretical interpretations of these baryonic resonances, and in particular of the $\Lambda_c(2595)$, give different predictions, a precise experimental measurement of these decays would be an important step for understanding their nature.Comment: 10 pages, 1 figur

Implications for the missing low-mass galaxies (satellites) problem from cosmic shear

The number of observed dwarf galaxies, with dark matter mass ≲1011 M⊙ in the Milky Way or the Andromeda galaxy does not agree with predictions from the successful ΛCDM paradigm. To alleviate this problem, a suppression of dark matter clustering power on very small scales has been conjectured. However, the abundance of dark matter halos outside our immediate neighbourhood (the Local Group) seem to agree with the ΛCDM-expected abundance. Here we connect these problems to observations of weak lensing cosmic shear, pointing out that cosmic shear can make significant statements about the missing satellites problem in a statistical way. As an example and pedagogical application, we use recent constraints on small-scale power suppression from measurements of the CFHTLenS data. We find that, on average, in a region of ∼Gpc3 there is no significant small-scale power suppression. This implies that suppression of small-scale power is not a viable solution to the 'missing satellites problem' or, alternatively, that on average in this volume there is no 'missing satellites problem' for dark matter masses ≳5 × 109 M⊙. Further analysis of current and future weak lensing surveys will probe much smaller scales, k > 10h Mpc−1 corresponding roughly to masses M < 109M⊙

A critical review of transhumanism: right to vulnerability in the Christian hope

El transhumanismo, y su posición más extrema posthumana, se ha convertido en los últimos tiempos en una de las claves para desentrañar el paradigma cultural en el que se juega la vida social, no ya del futuro, sino del presente. A pesar de la complejidad del debate y la variedad y divergencias de posiciones, en el origen del transhumanismo hemos detectado una pretensión que no es meramente científica, sino también religiosa: La pretensión de la salvación del hombre. La crítica que le realizamos se sostiene en el Derecho a la vulnerabilidad, raíz de la civilización que logrado condensar en los Derechos Humanos lo más propio del hombre: su razón y su libertad.Transhumanism, and its most extreme post-human position, has recently become one of the keys to unraveling the cultural paradigm in which social life is played, now and in the future. The complexity of the debate and the variety and divergence of positions, at the origin of transhumanism we have detected a claim that is not merely scientific, but also religious: The pretense of the salvation of man. The criticism we make is based on the Right to Vulnerability, the root of civilization that managed to condense into Human Rights the most characteristic of man: his reason and his freedom

Short-term drought responses by seedlings of three maizes from contrasting environments in Michoacán, Mexico

Alterations in precipitation regimes resulting from climate change threaten countries like Mexico, where rainfed ag- riculture for subsistence is widespread. However, numerous local maizes are cultivated throughout the country’s territory originated from a substantial environmental diversity. To investigate whether an environmental specializa- tion exists, responses to drought by maizes from three sites (elevations of 689, 2379, and 3638 m) in the state of Michoacán, Mexico, were studied in a greenhouse experiment. Plants were watered every other day for 21 days since sowing. Watering was withheld during 26 d and followed by a 10 d recovery period during which watering was resumed. Environmental conditions were contrasting among the sites of origin, e.g., annual precipitation defi- cit (from an ombrotherm diagram) was 33% at the lowest site and 9% and 0.3% for the sites at higher elevations. At the greenhouse, substrate water content for the control was ca. 34% (w/w) over the course of the experiment, it decreased to 1.9% at 26 d of water withholding and recovered after resuming irrigation. Tissue water content was ca. 92% for the control and decreased by 22-33% (depending on its origin) for the droughted individuals at the peak of the drought. Dry mass was lower for droughted individuals than for the control at the end of the experi- ment. Leaf chlorophyll content tended to decrease with plant age, but did not respond to water withholding. In contrast, proline tended to increase for droughted individuals. The the content of polyphenols, free-radical scav- enging compounds, tended to decrease during the recovery period, but not during drought. Neither did the anti- oxidant activity of leaf tissue respond to water withholding. Germplasm that is able cope with novel environmental conditions seems to exist in Mexico. Future studies should survey yield responses to different drought intensities for various maizes from dry environments to help identify traits useful in future breeding programs