Procesamiento de imágenes quasi-interactivo en el observatorio de La Plata

Se han iniciado las tareas conducentes a dotar al OALP de un sistema de procesamiento de imágenes interactivo dentro de las posibilidades actuales. Utilizando el equipo HP 1000 con 454 Kb de memoria en línea y 20 Mb en disco rígido más una impresora, con capacidad de graficación por matriz de puntos, se ha diseñado y codificado algunas rutinas elementales. Actualmente se pueden visualizar con la ayuda del mencionado printer, imágenes de hasta 256x256 píxels mapeando, mediante una sencilla "look-up-table", los 15 bits de la imagen en la memoria en 9 niveles de grises controlados en forma quasi interactiva. Además se dispone de una rutina de fotometría para imágenes estelares con centrado automático y corrección por el fondo del cielo.Asociación Argentina de Astronomí

Sistema de adquisición de datos del polarímetro

El sistema consiste en una interfase, diseñada a base de CMOS, capaz de comunicarse con cualquier computadora, a la cual se pueda entrar y salir con datos por sistema de entrada-salida o por interfases adicionales. Nuestro sistema emplea una microcomputadora CBM 2001. El software consiste en una rutina de BASIC y una subrutina en absoluto. La capacidad del sistema de adquisición de datos, expandible, es actualmente de 96 dígitos decimales.Asociación Argentina de Astronomí

El sistema detector multicanal del OALP

Se describen algunos resultados de la observación directa y otros correspondientes a la espectro-fotometría hecha en conjunción con el espectrógrafo Ridell-Spotz. Se comparan estos resultados con los obtenidos por sistemas similares en otros observatorios.Asociación Argentina de Astronomí

Large T Antigen-Specific Cytotoxic T Cells Protect Against Dendritic Cell Tumors through Perforin-Mediated Mechanisms Independent of CD4 T Cell Help.

Our newly generated murine tumor dendritic cell (MuTuDC) lines, generated from tumors developing in transgenic mice expressing the simian virus 40 large T antigen (SV40LgT) and GFP under the DC specific promoter CD11c, reproduce the phenotypic and functional properties of splenic wild type CD8α(+) conventional DCs. They have an immature phenotype with low co-stimulation molecule expression (CD40, CD70, CD80, and CD86) that is upregulated after activation with toll-like receptor ligands. We observed that after transfer into syngeneic C57BL/6 mice, MuTuDC lines were quickly rejected. Tumors grew efficiently in large T transgene-tolerant mice. To investigate the immune response toward the large T antigen that leads to rejection of the MuTuDC lines, they were genetically engineered by lentiviral transduction to express luciferase and tested for the induction of DC tumors after adoptive transfer in various gene deficient recipient mice. Here, we document that the MuTuDC line was rejected in C57BL/6 mice by a CD4 T cell help-independent, perforin-mediated CD8 T cell response to the SV40LgT without pre-activation or co-injection of adjuvants. Using depleting anti-CD8β antibodies, we were able to induce efficient tumor growth in C57BL/6 mice. These results are important for researchers who want to use the MuTuDC lines for in vivo studies

Observaciones de Au Mic durante la campaña internacional del IUE

Durante la campaña internacional del satélite IUE que se realizó en la primer semana de agosto de 1980, hemos observado la estrella variable de tipo flare AU Mic. Se han encontrado cuatro flares en siete horas de observaciones fotométricas y polarimétricas, que aún están en su etapa de reducción. Todas las observaciones fueron realizadas con el fotómetro fotoeléctrico y polarímetro digital rotatorio del Observatorio de La Plaata, adherido al telescopio reflector Perrin de 76 cm, de la Estación El Leóncito en la Pcia. de San Juan.Asociación Argentina de Astronomí

El sistema de digitalización de placas de La Plata

Se presenta un informe sobre el estado actual de los trabajos para digitalizar la medidora Grant y su conexión con la computadora HP 1000. Se muestran registros espectrofométricos que representan los primeros resultados obtenidos con el equipo. El trabajo de "hardware" y "software" puede considerarse completo en un 50 %.Asociación Argentina de Astronomí

The first orbital solution for the massive colliding-wind binary HD93162 (=WR25)

Since the discovery, with the EINSTEIN satellite, of strong X-ray emission associated with HD93162 (=WR25), this object has been predicted to be a colliding-wind binary system. However, radial-velocity variations that would prove the suspected binary nature have yet to be found. We spectroscopically monitored this object to investigate its possible variability to address this discordance. We compiled the largest available radial-velocity data set for this star to look for variations that might be due to binary motion. We derived radial velocities from spectroscopic data acquired mainly between 1994 and 2006, and searched these radial velocities for periodicities using different numerical methods. For the first time, periodic radial-velocity variations are detected. Our analysis definitively shows that the Wolf-Rayet star WR25 is an eccentric binary system with a probable period of about 208 days.Comment: 7 pages, 4 figures, accepted by A+

A young binary Brown Dwarf in the R-CrA star formation region

We present imaging and spectroscopic observations with HST (WFPC2, ACS/HRC and STIS), VLT (FORS2) and Keck (HIRES) of the dM8 ultra-cool dwarf DENIS-P J185950.9-370632, located in the R-CrA region. The presence of lithium absorption at 670.8 nm and the strong Halpha emission indicate a young age and a sub-stellar mass. Our diffraction-limited images resolve a companion at the separation limit of HST/ACS (~0.06"). The 2.1 mJy flux in the LW2 filter (5.0-8.5 microns) of the Infrared Space Observatory (see 1999A&A...350..883) likely corresponds to an infrared excess, suggesting the presence of circumstellar material. Proper motion and photometric measurements, as well as the Halpha activity, confirm membership in the R-CrA star forming region. If confirmed by further observations, DENIS-P J185950.9-370632 would be the first accreting sub-stellar multiple system observed to date.Comment: 18 pages, 11 figures, 3 tables Version with full resolution figures available on: ftp://ftp.mpe.mpg.de/people/hbouy/publications/DENIS1859.ps.g

A near-infrared survey of the entire R Corona Australis cloud

To understand low- to intermediate-mass star-formation in the nearby R CrA molecular cloud, we try to identify the stellar content that is accessible with near-infrared observations. We obtained a JHK band mosaic of 10 x 60 arcmin square covering the entire RCrA molecular cloud with unprecedented sensitivity. We present a catalogue of about 3500 near-infrared sources fainter than the saturation limit K = 10 mag, reaching K = 18mag. We analysed the extended sources by inspecting their morphology and point sources by means of colour-colour and colour-magnitude diagrams. Additionally, we compared the extinction inferred from the NIR data with the line-of-sight dust emission at 1.2 mm. Sources towards high dust emission but relatively low H-K show a projected mm-exces; these sources are either immediately surrounded by cold circumstellar material or, if too red to be a true foreground object, they are embedded in the front layer of the 1.2 mm emitting dust cloud. In both cases they are most likely associated with the cloud.Comment: 11 pages, 12 Figures, accepted by Astronomy and Astrophysic

Interstellar polarization and grain alignment: the role of iron and silicon

We compiled the polarimetric data for a sample of lines of sight with known abundances of Mg, Si, and Fe. We correlated the degree of interstellar polarization $P$ and polarization efficiency (the ratio of $P$ to the colour excess $E(B-V)$ or extinction $A_V$) with dust phase abundances. We detect an anticorrelation between $P$ and the dust phase abundance of iron in non silicate - containing grains ]_\rm d, a correlation between $P$ and the abundance of Si, and no correlation between $P/E(B-V)$ or $P/A_V$ and dust phase abundances. These findings can be explained if mainly the silicate grains aligned by the radiative mechanism are responsible for the observed interstellar linear polarization.Comment: Accepted for publication in Astronomy and Astrophysic