The interface between the stellar wind and interstellar medium around R Cassiopeiae revealed by far-infrared imaging

The circumstellar dust shells of intermediate initial-mass (about 1 to 8 solar masses) evolved stars are generated by copious mass loss during the asymptotic giant branch phase. The density structure of their circumstellar shell is the direct evidence of mass loss processes, from which we can investigate the nature of mass loss. We used the AKARI Infrared Astronomy Satellite and the Spitzer Space Telescope to obtain the surface brightness maps of an evolved star R Cas at far-infrared wavelengths, since the temperature of dust decreases as the distance from the star increases and one needs to probe dust at lower temperatures, i.e., at longer wavelengths. The observed shell structure and the star's known proper motion suggest that the structure represents the interface regions between the dusty wind and the interstellar medium. The deconvolved structures are fitted with the analytic bow shock structure to determine the inclination angle of the bow shock cone. Our data show that (1) the bow shock cone of 1 - 5 x 10^-5 solar masses (dust mass) is inclined at 68 degrees with respect to the plane of the sky, and (2) the dust temperature in the bow shock cone is raised to more than 20 K by collisional shock interaction in addition to the ambient interstellar radiation field. By comparison between the apex vector of the bow shock and space motion vector of the star we infer that there is a flow of interstellar medium local to R Cas whose flow velocity is at least 55.6 km/s, consistent with an environment conducive to dust heating by shock interactions.Comment: 7 pages, 2 figures, accepted for publication in Astronomy and Astrophysic

An AKARI Search for Intracluster Dust of Globular Clusters

We report the observations of 12 globular clusters with the AKARI/FIS. Our goal is to search for emission from the cold dust within clusters. We detect diffuse emissions toward NGC 6402 and 2808, but the IRAS 100-micron maps show the presence of strong background radiation. They are likely emitted from the galactic cirrus, while we cannot rule out the possible association of a bump of emission with the cluster in the case of NGC 6402. We also detect 28 point-like sources mainly in the WIDE-S images (90 micron). At least several of them are not associated with the clusters but background galaxies based on some external catalogs. We present the SEDs by combining the near-and-mid infrared data obtained with the IRC if possible. The SEDs suggest that most of the point sources are background galaxies. We find one candidate of the intracluster dust which has no mid-infrared counterpart unlike the other point-like sources, although some features such as its point-like appearance should be explained before we conclude its intracluster origin. For most of the other clusters, we have confirmed the lack of the intracluster dust. We evaluate upper limits of the intracluster dust mass to be between 1.0E-05 and 1.0E-03 solar mass depending on the dust temperature. The lifetime of the intracluster dust inferred from the upper limits is shorter than 5 Myr (T=70K) or 50 Myr (35K). Such short lifetime indicates some mechanism(s) are at work to remove the intracluster dust. We also discuss its impact on the chemical evolution of globular clusters.Comment: Accepted for publication in PASJ AKARI special issue. 14 pages, 11 figure

AKARI Near- to Mid-Infrared Imaging and Spectroscopic Observations of the Small Magellanic Cloud. I. Bright Point Source List

We carried out a near- to mid-infrared imaging and spectroscopic observations of the patchy areas in the Small Magellanic Cloud using the Infrared Camera on board AKARI. Two 100 arcmin2 areas were imaged in 3.2, 4.1, 7, 11, 15, and 24 um and also spectroscopically observed in the wavelength range continuously from 2.5 to 13.4 um. The spectral resolving power (lambda/Delta lambda) is about 20, 50, and 50 at 3.5, 6.6 and 10.6 um, respectively. Other than the two 100 arcmin2 areas, some patchy areas were imaged and/or spectroscopically observed as well. In this paper, we overview the observations and present a list of near- to mid-infrared photometric results, which lists ~ 12,000 near-infrared and ~ 1,800 mid-infrared bright point sources detected in the observed areas. The 10 sigma limits are 16.50, 16.12, 13.28, 11.26, 9.62, and 8.76 in Vega magnitudes at 3.2, 4.1, 7, 11, 15, and 24 um bands, respectively.Comment: 16 pages, 7 figures, accepted for publication in PASJ. Full resolution version is available at http://www-irc.mtk.nao.ac.jp/%7Eyita/smc20100112.pd

Caracterização sazonal do efeito de atrazina e 2,4-D sobre microrganismos de solos da microbacia do córrego do Espraiado, Ribeirão Preto-SP.

Com o objetivo de estudar o efeito sazonal de atrazina e 2,4-D sobre os microrganismos do solo e se isolar aqueles com potencial para degradar os herbicidas, foram coletadas mensalmente, durante o ano de 1996, amostras de solo de 9 pontos a profundidade de 0-20 cm em area de cana-de-acucar da microbacia do Espraiado, regiao de Ribeirao Preto. Os solos variaram de argiloso a arenoso. Suspensoes de solo, (5 g/50 ml), recem coletadas foram tratadas com atrazina (1 mg/ml) e 2,4-D (0,5 mg/ml) e incubadas a 30oC por 21 dias, juntamente com a testemunha. A populacao microbiana foi monitorada semanalmente por plaqueamento, contagem, fotografia e isolamento de colonias. Os resultados mostraram variacao sazonal significativa no comportamento quali e quantitativo da populacao microbiana. O crescimento dos microrganismos nas amostras de fevereiro a maio foi fortemente inibido por 2,4-D. No mes de junho, a atrazina inibiu o crescimento, ao passo que em agosto, 2,4-D passou a exercer forte efeito estimulante, com populacoes de ate 15 vezes maior que a testemunha. Em outubro, ambos herbicidas estimularam de maneira geral o crescimento. O tipo de solo apresentou pequena influencia. Os tratamentos promoveram crescimento diferenciado de populacoes homogeneas tipicas e caracteristicas para cada um dos herbicidas com a predominancia de bacterias para ambos, apesar de tambem serem detectados fungos e leveduras. Atrazina e 2,4-D na maioria das vezes agiram antagonicamente, sendo o 2,4-D inibidor mais potente sobre a populacao de solos arenosos, quando a inibiu. O tratamento com os herbicidas reduziu o grau de biodiversidade sendo comumente encontrado um unico tipo celular nas placas, distinto para atrazina e 2,4-D

Adsorptividade de solos da microbacia do Córrego do Espraiado, Ribeirão Preto: riboflavina como modelo de adsorção.

Em area onde foram desenvolvidos estudos sobre os efeitos dos herbicidas atrazina e 2,4-D sobre a populacao microbiana dos solos da microbacia do Espraiado, Ribeirao Preto-SP, foi tambem pesquisado o uso de riboflavina, composto organico facilmente detectavel por espectrofotometria a baixas concentracoes, como modelo de estudos de adsorcao de solos. Os solos empregados neste trabalho foram provenientes de 9 pontos selecionados da microbacia para estudos microbiologicos e se agruparam em argilosos e arenosos, com teores de materia organica de 0,15 a 3,50%. Os resultados de adsorcao mostraram que a riboflavina foi adsorvida pelos diferentes solos, em proporcoes variadas dependente do solo. As isotermas de adsorcao revelaram isotermas do tipo L, como as observadas para os herbicidas triazinicos, como a atrazina. Os valores experimentais, para amostras coletadas de 0-20 cm aplicados a equacao de Freundlich, mostraram correlacao variando de 0.93 a 0,99, e valores de K de 0,47 a 63,43 e 1/n de 0,42 a 1,42. Os valores de Kd para riboflavina em diferentes amostras variaram de 0,61 +- 0,26 (amostra de solo arenoso) a 56,1 +- 13,7 (amostra de solo argiloso) enquanto o Koc variou de 230 +- 32 (solo arenoso) a 4671 +- 780 (solo argiloso). Amostras de solos argilosos coletadas a 80-90 cm, com menor teor de materia organica, tiveram valores de Koc maiores, enquanto em solo arenoso foram semelhantes. Valores de Kd, Koc e constantes da equacao e Freundlich encontrados para riboflavina sao comparaveis aqueles de uma gama de herbicidas puplicados na literatura, tornando riboflavina um modelo pratico e conveniente para o estudo de adsorptividade de herbicidas em solos

Three-body Faddeev Calculation for 11Li with Separable Potentials

The halo nucleus $^{11}$Li is treated as a three-body system consisting of an inert core of $^{9}$Li plus two valence neutrons. The Faddeev equations are solved using separable potentials to describe the two-body interactions, corresponding in the n-$^{9}$Li subsystem to a p$_{1/2}$ resonance plus a virtual s-wave state. The experimental $^{11}$Li energy is taken as input and the $^{9}$Li transverse momentum distribution in $^{11}$Li is studied.Comment: 6 pages, RevTeX, 1 figur

Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy

International audienceWe report the design and characterization of a new molecular-beam/surface-science apparatus for quantum state-resolved studies of gas/surface reaction dynamics combining optical state-specific reactant preparation in a molecular beam by rapid adiabatic passage with detection of surface-bound reaction products by reflection absorption infrared spectroscopy (RAIRS). RAIRS is a non-invasive infrared spectroscopic detection technique that enables online monitoring of the buildup of reaction products on the target surface during reactant deposition by a molecular beam. The product uptake rate obtained by calibrated RAIRS detection yields the coverage dependent state-resolved reaction probability S(θ). Furthermore, the infrared absorption spectra of the adsorbed products obtained by the RAIRS technique provide structural information, which help to identify nascent reaction products, investigate reaction pathways, and determine branching ratios for different pathways of a chemisorption reaction. Measurements of the dissociative chemisorption of methane on Pt(111) with this new apparatus are presented to illustrate the utility of RAIRS detection for highly detailed studies of chemical reactions at the gas/surface interface

Herschel Planetary Nebula Survey (HerPlaNS) - First Detection of OH+ in Planetary Nebulae

We report the first detections of OH$^+$ emission in planetary nebulae (PNe). As part of an imaging and spectroscopy survey of 11 PNe in the far-IR using the PACS and SPIRE instruments aboard the Herschel Space Observatory, we performed a line survey in these PNe over the entire spectral range between 51 and 672$\mu$m to look for new detections. OH$^+$ rotational emission lines at 152.99, 290.20, 308.48, and 329.77$\mu$m were detected in the spectra of three planetary nebulae: NGC 6445, NGC 6720, and NGC 6781. Excitation temperatures and column densities derived from these lines are in the range of 27 to 47 K and 2$\times$10$^{10}$ to 4 $\times$10$^{11}$ cm$^{-2}$, respectively. In PNe, the OH+ rotational line emission appears to be produced in the photodissociation region (PDR) in these objects. The emission of OH+ is observed only in PNe with hot central stars (T$_{eff}$ > 100000 K), suggesting that high-energy photons may play a role in the OH+ formation and its line excitation in these objects, as it seems to be the case for ultraluminous galaxies.Comment: 9 pages, 7 figures; accepted for publication in A&

Quasi-degenerate self-trapping in one-dimensional charge transfer exciton

The self-trapping by the nondiagonal particle-phonon interaction between two quasi-degenerate energy levels of excitonic system, is studied. We propose this is realized in charge transfer exciton, where the directions of the polarization give the quasi-degeneracy. It is shown that this mechanism, unlike the conventional diagonal one, allows a coexistence and resonance of the free and self-trapped states even in one-dimensional systems and a quantitative theory for the optical properties (light absorption and time-resolved luminescence) of the resonating states is presented. This theory gives a consistent resolution for the long-standing puzzles in quasi-one-dimensional compound A-PMDA.Comment: accepted to Phys. Rev. Letter