486 research outputs found
Acceleration with Self-Injection for an All-Optical Radiation Source at LNF
We discuss a new compact gamma-ray source aiming at high spectral density, up
to two orders of magnitude higher than currently available bremsstrahlung
sources, and conceptually similar to Compton Sources based on conventional
linear accelerators. This new source exploits electron bunches from
laser-driven electron acceleration in the so-called self-injection scheme and
uses a counter-propagating laser pulse to obtain X and gamma-ray emission via
Thomson/Compton scattering. The proposed experimental configuration inherently
provides a unique test-bed for studies of fundamental open issues of
electrodynamics. In view of this, a preliminary discussion of recent results on
self-injection with the FLAME laser is also given.Comment: 8 pages, 10 figures, 44 references - Channeling 2012 conferenc
Fast Mid-IR Flashes Detected During Small Solar X-Ray Bursts
Solar observations in the mid-infrared 8-14 \mu\m band continuum were carried
out with cadence of 5 frames per second, in December 2007. Rapid small heated
sources, with typical duration of the order of seconds, were found on the
bright plage-like areas around sunspots, in association with relatively weak
GOES soft X-ray bursts. This work presents the analysis of fast mid-infrared
flashes detected during a GOES B2.0-class event on 10 December 2007, beginning
at about 10:40 UT. Rapid brightness temperature enhancements of 0.5 to 2.0 K
were detected at the Earth by a microbolometer array, using a telescope with
10.5 cm diameter aperture producing a diffraction limited field-of-view of 25
arcsec. Minimum detectable temperature change was of 0.1 K. The corresponding
fluxes are 30-130 solar flux units. At the solar surface the estimated rapid
brightenings were of 50-150 KComment: 12 pages including 6 figures. Accepted by Solar Physics, April 201
Spectroscopic Binaries in Southern Open Clusters
Aportamos un informe del trabajo sobre binarias que venimos desarrollando en cúmulos del hemisferio sur. Elpropósito es contribuir a comprender la formación y evolución de binarias espectroscópicas, proporcionandocondiciones de contorno que permitan verificar algunas de las teorías actuales sobre la formación de binariasen cúmulos abiertos.This is a report on an ongoing program about binaries in southern open clusters. The long-term purpose ofthis project is to contribute to understanding the formation and evolution of spectroscopic binaries, providingobservational constraints that will permit tests of some of the current theories on binary formation in openclusters
Spectroscopic Binaries in Southern Open Clusters
Aportamos un informe del trabajo sobre binarias que venimos desarrollando en cúmulos del hemisferio sur. El propósito es contribuir a comprender la formación y evolución de binarias espectroscópicas, proporcionando condiciones de contorno que permitan verificar algunas de las teorías actuales sobre la formación de binarias en cúmulos abiertos.This is a report on an ongoing program about binaries in southern open clusters. The long-term purpose of this project is to contribute to understanding the formation and evolution of spectroscopic binaries, providing observational constraints that will permit tests of some of the current theories on binary formation in open clusters.Facultad de Ciencias Astronómicas y Geofísica
Elemental abundance study of the CP star HD 206653
An analysis of the abundances of the Silicon star HD 206653 is presented using an ATLAS9 model atmosphere and observational material taken with a REOSC echelle spectrograph attached to the Jorge Sahade 2.15 m telescope at CASLEO. The light elements are solar or deficient except silicon which is overabundant by a factor of 5. The iron peak elements are all overabundant by factors between 10 and 50. Sr and Y are around 1000 times the solar values. Among the Rare Earths only Ce and Eu are identified; both are overabundant by large factors.Facultad de Ciencias Astronómicas y Geofísica
Elemental abundance study of the CP star HD 206653
An analysis of the abundances of the Silicon star HD 206653 is presented using an ATLAS9 model atmosphere and observational material taken with a REOSC echelle spectrograph attached to the Jorge Sahade 2.15 m telescope at CASLEO. The light elements are solar or deficient except silicon which is overabundant by a factor of 5. The iron peak elements are all overabundant by factors between 10 and 50. Sr and Y are around 1000 times the solar values. Among the Rare Earths only Ce and Eu are identified; both are overabundant by large factors.Facultad de Ciencias Astronómicas y Geofísica
Bibliographic catalogue of stellar radial velocities: (1991-1994)
We present a bibliographic catalogue of stellar radial velocities with 13359 entries for stars in the galaxy and the Magellanic Clouds, obtained from the issues of several journals published in the period 1991-1994. We have tried to follow the structure of previous compilations although we have relied on data retrived from the SIMBAD database.Facultad de Ciencias Astronómicas y Geofísica
X-rays and Protostars in the Trifid Nebula
The Trifid Nebula is a young HII region recently rediscovered as a
"pre-Orion" star forming region, containing protostars undergoing violent mass
ejections visible in optical jets as seen in images from the Infrared Space
Observatory and the Hubble Space Telescope. We report the first X-ray
observations of the Trifid nebula using ROSAT and ASCA. The ROSAT image shows a
dozen X-ray sources, with the brightest X-ray source being the O7 star, HD
164492, which provides most of the ionization in the nebula. We also identify
85 T Tauri star and young, massive star candidates from near-infrared colors
using the JHKs color-color diagram from the Two Micron All Sky Survey (2MASS).
Ten X-ray sources have counterpart near-infrared sources. The 2MASS stars and
X-ray sources suggest there are potentially numerous protostars in the young
HII region of the Trifid. ASCA moderate resolution spectroscopy of the
brightest source shows hard emission up to 10 keV with a clearly detected Fe K
line. The best model fit is a two-temperature (T = 1.2x10^6 K and 39x10^6 K)
thermal model with additional warm absorbing media. The hotter component has an
unusually high temperature for either an O star or an HII region; a typical
Galactic HII region could not be the primary source for such hot temperature
plasma and the Fe XXV line emission. We suggest that the hotter component
originates in either the interaction of the wind with another object (a
companion star or a dense region of the nebula) or from flares from deeply
embedded young stars.Comment: Accepted in ApJ (Oct, 20 issue, 2001
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