802 research outputs found
A data base of synthetic photometry in the GALEX ultraviolet bands for the stellar sources observed with the International Ultraviolet Explorer
The Galaxy Evolution Explorer (GALEX) has produced the largest photometric
catalogue of ultraviolet (UV) sources. As such, it has defined the new standard
bands for UV photometry: the near UV band (NUV) and the far UV band (FUV).
However, due to brightness limits, the GALEX mission has avoided the Galactic
plane which is crucial for astrophysical research and future space missions.
The International Ultraviolet Explorer (IUE) satellite obtained 63,755 spectra
in the low dispersion mode during its 18 years lifetime. We have derived the
photometry in the GALEX bands for the stellar sources in the IUE Archive to
extend the GALEX data base with observations including the Galactic plane.Good
quality spectra have been selected for all IUE classes of stellar sources. The
GALEX FUV and NUV magnitudes have been computed using the GALEX transmission
curves, as well as the conversion equations between flux and magnitudes
provided by the mission (galexgi.gsfc.nasa.gov). Consistency between GALEX and
IUE synthetic photometries has been tested using White Dwarfs (WD) contained in
both samples. The non-linear response performance of GALEX inferred from this
data agrees with the results from GALEX calibration. The photometric data base
is made available to the community through the services of the Centre de
Donn\'ees Stellaires at Strasbourg (CDS). The catalogue contains FUV magnitudes
for 1,631 sources, ranging from FUV=1.81 to FUV=18.65 mag. In the NUV band, the
catalogue includes observations for 1,005 stars ranging from NUV = 3.08 to NUV=
17.74 mag . UV photometry for 1,493 not included in the GALEX AIS GR5 catalogue
is provided; most of them are hot (O-A spectral type) stars. The sources in the
catalogue are distributed over the full sky, including the Galactic plane.Comment: Submitted to Astronomy & Astrophysic
Signatures of diffuse interstellar gas in the Galaxy Evolution Explorer all sky survey
The all sky survey run by the Galaxy Evolution Explorer (GALEX AIS) mapped
about 85% of the Galaxy at ultraviolet (UV) wavelengths and detected the
diffuse UV background produced by the scattering of the radiation from OBA
stars by interstellar dust grains. Against this background, diffuse weak
structures are detected as well as the UV counterparts to nebulae and molecular
clouds. To make full profit of the survey, unsupervised and semi-supervised
procedures need to be implemented. The main objective of this work is to
implement and analyze the results of the method developed by us for the blind
detection of ISM features in the GALEX AIS . Most ISM features are detected at
very low signal levels (dark filaments, globules) against the already faint UV
background. We have defined an index, the UV background fluctuations index (or
UBF index), to identify areas of the sky where these fluctuations are detected.
The algorithm is applied to the images obtained in the FUV (1344 -1786
Angstroms) band since this is less polluted by stellar sources, facilitating
the automated detection. The UBF index is shown to be sensitive to the main
star forming regions within the Gould's Belt, as well as to some prominent
loops like Loop I or the Eridanus and Monogem areas. The catalogue with the UBF
index values is made available on-line to the community.Comment: The online catalogue will be made available through the CDS services
and in the jcuva.ucm.es website. Accepted A&
Variation of the ultraviolet extinction law across the Taurus-Auriga star forming complex. A GALEX based study
The Taurus-Auriga molecular complex (TMC) is the main laboratory for the
study of low mass star formation. The density and properties of interstellar
dust are expected to vary across the TMC. These variations trace important
processes such as dust nucleation or the magnetic field coupling with the
cloud. In this article, we show how the combination of near ultraviolet (NUV)
and infrared (IR) photometry can be used to derive the strength of the 2175
\AA\ bump and thus any enhancement in the abundance of small dust grains and
PAHs in the dust grains size distribution. This technique is applied to the
envelope of the TMC, mapped by the GALEX All Sky Survey (AIS). UV and IR
photometric data have been retrieved from the GALEX-AIS and the 2MASS
catalogues. NUV and K-band star counts have been used to identify the areas in
the cloud envelope where the 2175 \AA\ bump is weaker than in the diffuse ISM
namely, the low column density extensions of L1495, L1498 and L1524 in Taurus,
L1545, L1548, L1519, L1513 in Auriga and L1482-83 in the California region.
This finding agrees with previous results on dust evolution derived from
Spitzer data and suggests that dust grains begin to decouple from the
environmental galactic magnetic field already in the envelope.Comment: Accepted in Monthly Notices of the Royal Astronomical Societ
Hubble Space Telescope STIS spectrum of RW Aurigae A: Evidence for an ionized beltlike structure and mass ejection in timescales of a few hours
Profiles of the UV semiforbidden lines of C III](1908) and Si III](1892) of RW Aur have been obtained with the Hubble Space Telescope (HST) STIS. The C III](1908) profile shows two high-velocity components at upsilon = +/-170 km s(-1) and a central one. The Si III](1892) profile is very broad (FWHM = 293 km s(-1)), and the high-velocity components are unresolved. The high-velocity components are most probably produced in a rotating belt similar to that detected in other sources of bipolar outflows. A radius between 2.7 R-* and the corotation radius (6.1 R-*) is derived, and a log T-e(K) similar or equal to 4.7 and log n(e)(cm(-3)) = 11.6 are estimated. The belt is clumpy, and the most likely source of heating is local X-ray radiation, probably associated with the release of magnetic energy. In addition, profiles of the optical lines of He I, Fe II, and Halpha retrieved from the HST archive have been analyzed. The spectra were obtained by shifting the STIS slit between exposures in the transverse direction to the flow. Two features vary from one exposure to another: a blueshifted emission feature (detected in the Fe II and He I lines) and a redshifted absorption feature (detected in Halpha), which are observed at the velocity of the blueshifted and redshifted components of the jet, respectively. There is a clear-cut correlation between the equivalent widths of these two components. These components are not associated with the flaring activity of the source, since they remain stable timescales of similar or equal to40 minutes. They are most likely associated with variations in the stellar/circumstellar environment in timescales of a few (similar or equal to5) hours, consistent with reports by other authors for variations of the veiling and the appearance of shell signatures in the optical spectrum
Una propuesta integradora de Mantenimiento Correctivo aplicada al Diseño Web Adaptativo y Accesibilidad Web
The increase of ICT has promoted free software such as Content Management System (CMS) that facilitate the efficient generation of digital content. CMS should be evaluated before to be to use, in order to generate accessible product. The work presents a corrective maintenance application implemented through Web Accessibility and Adaptive Web Design. The incorporation of this guidelines in software development, guarantee the quality of this products and promotes digital inclusion of individuals regardless of their abilities. El incremento de las TIC ha promovido el desarrollo de herramientas informáticas libres y gratuitas, como los Content Management System o Sistemas de Gestión de Contenidos que facilitan la generación eficaz de contenidos digitales. Éstos deben ser evaluados previos a su utilización, a los efectos de producir un producto accesible por todos los usuarios. Se presenta una experiencia de Mantenimiento Correctivo del software aplicada a la Accesibilidad Web y el Diseño Web Adaptativo. La incorporación de estas pautas en el desarrollo de software, permiten impulsar la generación de productos tecnológicos de calidad y fomentan la inclusión digital de los individuos independientemente de sus capacidade
Una propuesta integradora de Mantenimiento Correctivo aplicada al Diseño Web Adaptativo y Accesibilidad Web
The increase of ICT has promoted free software such as Content Management System (CMS) that facilitate the efficient generation of digital content. CMS should be evaluated before to be to use, in order to generate accessible product. The work presents a corrective maintenance application implemented through Web Accessibility and Adaptive Web Design. The incorporation of this guidelines in software development, guarantee the quality of this products and promotes digital inclusion of individuals regardless of their abilities. El incremento de las TIC ha promovido el desarrollo de herramientas informáticas libres y gratuitas, como los Content Management System o Sistemas de Gestión de Contenidos que facilitan la generación eficaz de contenidos digitales. Éstos deben ser evaluados previos a su utilización, a los efectos de producir un producto accesible por todos los usuarios. Se presenta una experiencia de Mantenimiento Correctivo del software aplicada a la Accesibilidad Web y el Diseño Web Adaptativo. La incorporación de estas pautas en el desarrollo de software, permiten impulsar la generación de productos tecnológicos de calidad y fomentan la inclusión digital de los individuos independientemente de sus capacidade
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