17 research outputs found
Developing Basic Space Science World Wide: Progress Report
The UN/ESA Workshops on Basic Space Science is a long-term effort for the
development of astronomy and regional and international co-operation in this
field on a world wide basis, particularly in developing nations. The first four
workshops in this series (India 1991, Costa Rica and Colombia 1992, Nigeria
1993, and Egypt 1994) addressed the status of astronomy in Asia and the
Pacific, Latin America and the Caribbean, Africa, and Western Asia,
respectively. One major recommendation that emanated from the first four
workshops was that small astronomical facilities should be established in
developing nations for research and education programmes at the university
level and that such facilities should be networked. Subsequently, material for
teaching and observing programmes for small optical telescopes were developed
or recommended and astronomical telescope facilities have been inaugurated at
UN/ESA Workshops on Basic Space Science in Sri Lanka (1995), Honduras (1997),
and Jordan (1999). UN/ESA Workshops on Basic Space Science in Germany (1996),
France (2000), Mauritius (2001), Argentina (2002), and P.R. China (2004)
emphasised the particular importance of astrophysical data systems and the
virtual observatory concept for the development of astronomy on a world wide
basis. Since 1996, the workshops are contributing to the development of the
World Space Observatory concept. Achievements of the series of workshops are
briefly summarised in this report.Comment: 3 page
World Space Observatory/Ultraviolet (WSO/UV): Progress Report
The World Space Observatory/Ultraviolet (WSO/UV) represents a new mission
implementation model for large space missions for astrophysics. The process has
been brought up to enable, fully scientific needs driven, a logic to be applied
to the demands for large collection powers required to undertake space missions
which are complementary to the continuously increasing sensitivity of
ground-based telescopes. One of the assumptions associated with the idea of a
WSO is to avoid the excessive complexity required for multipurpose missions.
Although there may exist purely technological or programmatic policy issues,
which would suggest such more complex missions to be more attractive, many
other aspects, which do not need to be explored in this report, may argue
against such a mission model. Following this precept and other reasons, the
first implementation model for a WSO has been done for the ultraviolet domain
WSO/UV. WSO/UV is a follow-up project of the UN/ESA Workshops on Basic Space
Science, organised annually since 1991.Comment: 4 page
The Nature of the Broad--Line--Region in the Radio--Loud AGN 3C390.3
We present an analysis of the ultraviolet and X-Ray variability of the Broad-
Line-Radio Galaxy 3C390.3 over 15 years. The UV continuum showed large
variations with amplitudes of up to a factor of 10. We find: (1) The variations
of CIV and Ly_alpha are highly correlated with the UV continuum, and are
delayed with respect to the continuum variations by 50-110 days with the red
wing of both CIV and Ly_alpha , leading the blue wing; (2) The CIV/Ly_alpha
ratio is positively correlated with both the continuum flux and UV line
strength, a behavior different from other AGNs studied so far; (3) The blue
sides of the Ly_alpha and CIV profiles are similar to the blue side of the
Balmer lines, while the red sides are different, suggesting a different origin
for the red peak in the Balmer lines. Our results suggest: (1) The broad CIV
and Ly_alpha emitting gas is infalling towards the central object; (2) The
overall behaviour of the CIV/Ly_alpha ratio and the absence of a big blue bump,
strongly indicate the coexistence of optically thick as well as optically thin
BLR clouds; (3) Assuming circular symmetry and predominantly circular motion,
the BLR gas is situated at 8325 lightdays from the central source; (4)
Under these assumptions and with the derived circular velocity of 2850 km s, the central mass inside this radius is confined to
; (6) Comparing our results with
those obtained from VLBI and observations of the Fe line, suggests
the association of the BLR with a disk, inclined at 9812 degrees with
respect to the direction of superluminal motion of the radio blobs.Comment: MNRAS in pres
Numerical Simulation of Non-Gaussian Random Fields with Prescribed Marginal Distributions and Cross-Correlation Structure II: Multivariate Random Fields
We provide theoretical procedures and practical recipes to simulate
non-Gaussian correlated, homogeneous random fields with prescribed marginal
distributions and cross-correlation structure, either in a N-dimensional
Cartesian space or on the celestial sphere. We illustrate our methods using
far-infrared maps obtained with the Infrared Space Observatory. However, the
methodology presented here can be used in other astrophysical applications that
require modeling correlated features in sky maps, for example, the simulation
of multifrequency sky maps where backgrounds, sources and noise are correlated
and can be modeled by random fields.Comment: 24 pages, 4 figures. To appear in PAS
Multiwavelength Monitoring of the BL Lacertae Object PKS 2155-304 in May 1994. II. The IUE Campaign
PKS 2155-304, the brightest BL Lac object in the ultraviolet sky, was
monitored with the IUE satellite at ~1 hour time-resolution for ten nearly
uninterrupted days in May 1994. The campaign, which was coordinated with EUVE,
ROSAT, and ASCA monitoring, along with optical and radio observations from the
ground, yielded the largest set of spectra and the richest short time scale
variability information ever gathered for a blazar at UV wavelengths. The
source flared dramatically during the first day, with an increase by a factor
~2.2 in an hour and a half. In subsequent days, the flux maintained a nearly
constant level for ~5 days, then flared with ~35% amplitude for two days. The
same variability was seen in both short- and long-wavelength IUE light curves,
with zero formal lag (~<2 hr), except during the rapid initial flare, when the
variations were not resolved. Spectral index variations were small and not
clearly correlated with flux. The flux variability observed in the present
monitoring is so rapid that for the first time, based on the UV emission alone,
the traditional Delta L/Delta t limit indicating relativistic beaming is
exceeded. The most rapid variations, under the likely assumption of synchrotron
radiation, lead to a lower limit of 1 G on the magnetic field strength in the
UV emitting region. These results are compared with earlier intensive
monitoring of PKS 2155-304 with IUE in November 1991, when the UV flux
variations had completely different characteristics.Comment: 45 pages, Latex, 11 PostScript figures, to appear in The
Astrophysical Journa
The evolution of ultraviolet emission lines from the circumstellar material surrounding SN 1987A
The presence of narrow high-temperature emission lines from nitrogen-rich gas
close to SN 1987A has been the principal observational constraint on the evolu-
tionary status of the supernova's progenitor. A new analysis of the complete
five-year set of low and high resolution IUE ultraviolet spectra of SN 1987A
(1987.2--1992.3) provide fluxes for the N V 1240, N IV] 1486, He II 1640, OIII]
1665, NIII] 1751, and CIII] 1908 lines with significantly reduced random and
systematic errors and reveals significant short-term fluctuations in the light
curves. The N V, N IV] and N III] lines turn on sequentially over 15 to 20 days
and show a progression from high to low ionization potential, implying an ioni-
zation gradient in the emitting region. The line emission turns on suddenly at
83+/-4 days after the explosion, as defined by N IV]. The N III] line reaches
peak luminosity at 399+/-15 days. A ring radius of (6.24+/-0.20)E{17} cm and
inclination of 41.0+/-3.9 is derived from these times, assuming a circular
ring. The probable role of resonant scattering in the N V light curve
introduces systematic errors that leads us to exclude this line from the timing
analysis. A new nebular analysis yields improved CNO abundance ratios
N/C=6.1+/-1.1 and N/O=1.7+/-0.5, confirming the nitrogen enrichment found in
our previous paper. From the late-time behavior of the light curves we find
that the emission origi- nates from progressively lower density gas. We
estimate the emitting mass near maximum (roughly 400 days) to be roughly
4.7E{-2} solar masses, assuming a filling factor of unity and an electron
density of 2.6E4 cm^{-3}. These results are discussed in the context of current
models for the emission and hydrodynamics of the ring.Comment: 38 pages, AASTeX v.4.0, 13 Postscript figures; ApJ, in pres
The World Space Observatory-Ultraviolet
El progreso de la astrofísica moderna requiere tener acceso al espectro electromagnético
en toda su extensión. El rango ultravioleta (UV) del espectro es
de un interés fundamental, puesto que contiene los trazadores espectrales más
sensibles de plasmas atómicos en el rango de temperaturas de los 3.000 a los
300.000K. El UV es también fundamental para el estudio de los plasmas moleculares,
puesto que las transiciones electrónicas de las moléculas más abundantes
del Universo (H2, CO, OH, CS, oor, C2...) se encuentran en este rango espectral.
Además la radiación UV es un agente fotonionizante muy importante (y
también un acelerador de la química en los entornos astronómico s).
El Observatorio Espacial Mundial o World Space Observatory UV (WSOjUV)
es una misión espacial dedicada a la espectroscopia UV y a la obtención de
imágenes astronómicas de alta resolución. La carga útil está constituida por
un telescopio de 170 cm, 4 cámaras UV, 2 cámaras ópticas, un espectrógrafo
de rendija y baja resolución espectral y un espectrógrafo echelle doble de alta
resolución espectral (HIRDES). Está previsto que el WSOjUV sea lanzado al
punto de Lagrange 2 (L2) en el 2012. El proyecto está gestionado por un extenso
consorcio mundialliderado por la Agencia Espacial Rusa (ROSCOSMOS).
Esta trabajo resume las características y el estado de definición del proyecto
WSO jUV en marzo de 2006, en el momento en que se cierra la edición de esta
publicación.Progress of modern astrophysics requires the access to the electromagnetic spectrum
in the broadest energy range. The ultraviolet (UV) is a fundamental energy
domain since it grants high sensitivity access to the study of both atomic
plasmas at temperatures in the 3,000-300,000 K range and molecular plasmas illuminated
by UV radiation since the electronic transitions of the most abundant
molecules in the Universe (H2, eo, OH, CS, co]. C2 ... ) are in this range; the
UV radiation field itself is a powerful astrochemical and photoionizing agent.
The World Space Observatory - UV is a space mission devoted to UV spectroscopy
and imaging. The payload is constituted by a 170cm telescope, 4
cameras working in the UV range, 2 cameras working in the optical range, a
long-slit low resolution spectrograph and a double echelle high resolution spectrograph
(HIRDES). WSO/UV is intended to be launched to the Lagrangian 2
(L2) point in 2010. The project is managed by a large, world-wide, consortium
lead by the Russian Space Agency, ROSCOSMOS.
This contribution summarizes the characteristics and state of definition of the
project WSO /UV in March 2006, at the time of closing the edition of this book.Peer reviewe