Preliminary Abundance Analysis of Galactic Bulge Main Sequence, Subgiant, and Giant Branch Stars Observed During Microlensing with Keck/HIRES

We present an abundance analysis of six main sequence turnoff, subgiant, and giant branch stars toward the Galactic bulge that were observed with Keck/HIRES during microlensing events. This is an early look at the first detailed chemical analysis of main sequence stars in the Galactic bulge. Lensing events allow the effective aperture of Keck to be increased beyond its current dimensions; although, some events still stretched its spectroscopic capabilities. Future large telescopes with high resolution and high throughput spectrometers will allow the study of abundances in distant stellar populations and in less evolved stars with greater ease.Comment: 8 pages including 2 figures. To appear in SPIE proceedings on Astronomical Telescopes and Instrumentation. Uses spie.cl

The Theory Behind TheoryMine

Abstract. We describe the technology behind the TheoryMine novelty gift company, which sells the rights to name novel mathematical theorems. A tower of four computer systems is used to generate recursive theories, then to speculate conjectures in those theories and then to prove these conjectures. All stages of the process are entirely automatic. The process guarantees large numbers of sound, novel theorems of some intrinsic merit.

The Expected Duration of Gamma-Ray Bursts in the Impulsive Hydrodynamic Models

Depending upon the various models and assumptions, the existing literature on Gamma Ray Bursts (GRBs) mentions that the gross theoretical value of the duration of the burst in the hydrodynamical models is tau~r^2/(eta^2 c), where r is the radius at which the blastwave associated with the fireball (FB) becomes radiative and sufficiently strong. Here eta = E/Mc^2, c is the speed of light, E is initial lab frame energy of the FB, and M is the baryonic mass of the same (Rees and Meszaros 1992). However, within the same basic framework, some authors (like Katz and Piran) have given tau ~ r^2 /(eta c). We intend to remove this confusion by considering this problem at a level deeper than what has been considered so far. Our analysis shows that none of the previously quoted expressions are exactly correct and in case the FB is produced impulsively and the radiative processes responsible for the generation of the GRB are sufficiently fast, its expected duration would be tau ~ar^2/(eta^2 c), where a~O(10^1). We further discuss the probable change, if any, of this expression, in case the FB propagates in an anisotropic fashion. We also discuss some associated points in the context of the Meszaros and Rees scenario.Comment: 21 pages, LATEX (AAMS4.STY -enclosed), 1 ps. Fig. Accepted in Astrophysical Journa

Radiation from collision-dominated relativistic pair fireballs

It is generally accepted that gamma-ray bursts (GRBs) are initiated by a relativistic pair fireball, converting its internal energy into kinetic energy of a relativistically moving plasmoid and subsequently into radiation. Here, we investigate the early stages of this evolution, after the pair fireball has become optically thin to gamma-gamma pair production. We show that for a short period of time, ~ 0.1 - a few seconds after the initial explosion, the pair plasmoid evolution might be dominated by collisional processes prior to the formation of a collisionless shock. We simulate these processes during the early pair plasmoid evolution and calculate the expected radiative signatures. We show that the radiation from the collision-dominated pair plasmoid phase results in a short (~ a few ms) flash of thermal soft X-ray emission, followed by a transition phase of < 1 s during which the fireball turns Thomson thin, but its radiation remains dominated by thermal Comptonization, peaking at around E_pk ~ 100 MeV - a few GeV. While the very early thermal emission could be associated with the quasi-thermal radiation signatures found in the very early phases of several bright BATSE GRBs, the predicted subsequent flash of high-energy emission should be easily detectable with the GLAST satellite.Comment: AASTeX, 25 pages, including 7 figures. Accepted for publication in Ap

Quasi-thermal Comptonization and gamma-ray bursts

Quasi-thermal Comptonization in internal shocks formed between relativistic shells can account for the high energy emission of gamma-ray bursts. This is in fact the dominant cooling mechanism if the typical energy of the emitting particles is achieved either through the balance between heating and cooling or as a result of electron-positron pair production. Both processes yield sub or mildly relativistic energies. In this case the synchrotron spectrum is self-absorbed, providing the seed soft photons for the Comptonization process, whose spectrum is flat [F(v) ~ const], ending either in an exponential cutoff or a Wien peak, depending on the scattering optical depth of the emitting particles. Self-consistent particle energy and optical depth are estimated and found in agreement with the observed spectra.Comment: 10 pages, ApJ Letters, accepted for publicatio

Fireballs Loading and the Blast Wave Model of Gamma Ray Bursts

A simple function for the spectral power $P(\epsilon,t) \equiv \nu L(\nu)$ is proposed to model, with 9 parameters, the spectral and temporal evolution of the observed nonthermal synchrotron power flux from GRBs in the blast wave model. Here $\epsilon = h\nu/$m$_e$c$^2$ is the observed dimensionless photon energy and $t$ is the observing time. Assumptions and an issue of lack of self-consistency are spelled out. The spectra are found to be most sensitive to the baryon loading, expressed in terms of the initial bulk Lorentz factor $\Gamma_0$, and an equipartition term $q$ which is assumed to be constant in time and independent of $\Gamma_0$. Expressions are given for the peak spectral power $P_p(t) = P(\epsilon_p,t)$ at the photon energy $\epsilon = \epsilon_p(t)$ of the spectral power peak. A general rule is that the total fireball particle kinetic energy $E_0 \sim \Pi_0 t_d$, where $t_d \propto \Gamma_0^{-8/3}$ is the deceleration time scale and $\Pi_0 \equiv P(\epsilon_p,t_d) \propto \Gamma_0^{8/3}$ is the maximum measured bolometric power output in radiation, during which it is carried primarily by photons with energy ${\cal E}_0 = \epsilon_p(t_d) \propto q\Gamma_0^4$.Comment: 26 pages, including 4 figures, uses epsf.sty, rotate.sty; submitted to ApJ; revised version with extended introduction, redrawn figures, and correction

Spatial and temporal variation of the different developmental stages of the sweet potato whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) in soybean

La soja es actualmente el cultivo más importante en la Argentina; a sus plagas tradicionales se ha sumado la mosca blanca, Bernisia tabaci. Los objetivos de este trabajo fueron establecer la distribución espacial de los diferentes estados de desarrollo (huevos, ninfas, pupas y adultos) de B. tabaci en lotes de soja del área central de la provincia de Córdoba (Argentina) y determinar la variación temporal de la abundancia de esos estados en dicha área. Se trabajó con muestras de lotes de dos localidades, Colonia Tirolesa y Colonia Caroya (Dpto. Colón). La comparación de abundancia entre localidades mostró variaciones entre ellas pero sólo se detectaron diferencias significativas entre adultos. Al comparar la variación de las abundancias entre fechas, sólo fue significativamente superior el aumento de ninfas y pupas durante la segunda fecha; en cuanto a los adultos se obtuvo mayor número durante la segunda fecha en Colonia Tirolesa. Cuando se analizó la variación de la abundancia tanto de inmaduros como de adultos se observaron diferencias significativas entre lotes para ambas localidades y para ambas fechas. Los resultados aquí presentados resultan de interés para ser utilizados en la toma de decisiones para el manejo de esta plaga.Soybean is now-a-days the most important crop in Argentina. Among all insect pests affecting this crop the sweetpotato whitefly, Bemisia tabaci, is becoming a new and increasingly important pest. In this paper we propose as objectives: a) to establish the spatial distribution of the different stages of B. tabaci in soybean plots in the central area of Cordoba province (Argentina) and b) to determine the spatio-temporal variation of the abundance of these stages in the same places. We worked with samples collected in to localities of Colon Department; Colonia Tirolesa and Colonia Caroya. The comparisons between localities showed a high variability between them but only the differences between adults were statistically significative. When we compared the variation of the abundance between sampling dates only the increase of nymphs and pupae were significative during the second sampling date in Colonia Tirolesa. When comparing the differences between soybean plots differences between plots in both localities and in all B. tabaci stages were observed. These results are an important input to be use in decision making for the management of this pest in the area.Fil: Cavallo, M. J.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinar de Biología Vegetal (p). Grupo Vinculado Centro de Relevamiento y Evaluacion de Recursos Agricolas y Naturales; ArgentinaFil: Bruno, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinar de Biología Vegetal (p). Grupo Vinculado Centro de Relevamiento y Evaluacion de Recursos Agricolas y Naturales; ArgentinaFil: Irastorza, R.. Universidad Nacional de Córdoba. Facultad de Ciencias Agropecuarias; ArgentinaFil: Grilli, Mariano Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinar de Biología Vegetal (p). Grupo Vinculado Centro de Relevamiento y Evaluacion de Recursos Agricolas y Naturales; Argentin