[Show abstract][Hide abstract] ABSTRACT: The tenth recorded outburst of the recurrent eclipsing nova U Sco was observed simultaneously in X-ray, UV, and optical by XMM-Newton on days 22.9 and 34.9 after the outburst. Two full passages of the companion in front of the nova ejecta were observed, as was the reformation of the accretion disk. On day 22.9, we observed smooth eclipses in UV and optical but deep dips in the X-ray light curve that disappeared by day 34.9, yielding clean eclipses in all bands. X-ray dips can be caused by clumpy absorbing material that intersects the line of sight while moving along highly elliptical trajectories. Cold material from the companion could explain the absence of dips in UV and optical light. The disappearance of X-ray dips before day 34.9 implies significant progress in the formation of the disk. The X-ray spectra contain photospheric continuum emission plus strong emission lines, but no clear absorption lines. Both continuum and emission lines in the X-ray spectra indicate a temperature increase from day 22.9 to day 34.9. We find clear evidence in the spectra and light curves for Thompson scattering of the photospheric emission from the white dwarf. Photospheric absorption lines can be smeared out during scattering in a plasma of fast electrons. We also find spectral signatures of resonant line scattering that lead to the observation of the strong emission lines. Their dominance could be a general phenomenon in high-inclination systems such as Cal 87.
The Astrophysical Journal 12/2011; 745(1):43. · 6.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We describe the functionalities and contents of Version 3.0 of the IUE
Newly Extracted Spectra (INES) System, which has been developed jointly
by ESA and LAEFF, and which has been operational at the INES Principal
Centre (LAEFF) since August 2000. At the time of writing, it is being
distributed to the National Hosts.
[Show abstract][Hide abstract] ABSTRACT: The IUE Archive was the first astronomical archive to be made accessible
on-line, back in 1985, when the World Wide Web didn't even exist. The
archive stores more than 110000 spectra which span nearly two decades of
Ultraviolet Astronomy. The IUE Newly Extracted Spectra System (INES), a
complete astronomical archive and its associated data distribution
system, was developed with the goal of delivering IUE data to the
scientific community in a simple and efficient form. Data distribution
is structured into three levels: a Principal Centre at LAEFF (Laboratory
for Space Astronomy and Theoretical Physics, owned by the Spanish
National Institute for Aerospace Technology) and its Mirror at CADC, a
number of National Hosts (currently 22), and an unlimited number of end
users. The INES Principal Centre can be reached at
[Show abstract][Hide abstract] ABSTRACT: In this paper we document the results of the study which led to the ripple correction and absolute calibration algorithms applied to the high resolution spectra processed with the NEWSIPS software for the Final Archive of the IUE Project. In this analysis, based on a very large number of spectra, we find that both K and the alpha parameters (not only the former as previously believed) vary with order number. This fact, together with the finding that the central peaks of the blaze function vary also as a function of the THDA temperature (for the SWP camera) and of the date of observations (for the LWP and LWR cameras), makes the ripple correction algorithm more complex than previously considered but, at the same time, considerably more reliable. As for the high resolution absolute calibration, the method followed is similar to the one implemented in IUESIPS. The internal accuracy of the high resolution calibration is about 4%. We note that the ripple correction and absolute calibration algorithms here described apply also to IUE data processed and distributed with the INES system. Comment: 11 pages, 16 figures, accepted for publication in A&A Supplement Series
Astronomy and Astrophysics Supplement Series 10/1999;
[Show abstract][Hide abstract] ABSTRACT: Ultraviolet (λ: 1150-3300 A) observations of SN 1987A with the
IUE satellite provide a unique data set. Observations started the day
after discovery, 1987 February 24 (day 1.6), and a total of 751 spectra
were obtained through 1992 June 9 (day 1567). The data have been
processed to generate a complete catalog of SN 1987A ultraviolet
spectra. The data reduction procedure includes careful line-by-line
extraction, removing hits and hot pixels, and, most importantly, a
scrupulous subtraction of the contribution from stars near SN 1987A
within the IUE aperture. In addition to processing the data, we have
also extracted light curves, and combined them with the ground-based
optical data and HST observations (day 1278 to 2431) to extend the study
in both wavelength and time. The data-processing procedures of our IUE
study produce results that are consistent with the HST data where they
overlap, but not with the IUE study by Sanz Fernandez de Cordoba (1993)
because of its incorrect background subtraction. The IUE data are
consistent with the ground-based Walraven V BLUW photometry, while we
found that flux scale of the Soviet ASTRON satellite spectroscopic data
is low by ~15%. The UV flux plummeted during the earliest days of
observations because of the drop in the photospheric temperature and the
increase in opacity. However, after reaching a minimum of 0.04% on day
44, the UV flux increased by 175 times in its contribution to 7% of the
total UVOIR bolometric luminosity at day 800. A revised set of
bolometric data has been constructed which includes the contribution of
UV from day 1 to day 1352. Studies of the UV colors show that the
supernova started to get bluer in UV around the time when dust started
to form in the ejecta. Our results are consistent with the possibility
that the dust condensed may be metal-rich.
The Astrophysical Journal Supplement Series 06/1995; 99:223. · 16.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The results of an extensive coordinated UV and optical spectroscopic
study of the Seyfert 1 galaxy NGC 5548 are presented. The very broad
component has a blueshift of 2000 km/s, possibly indicating obscuration
in the innermost parts of an accretion disk. Unlike Ly-alpha, the very
broad C IV 1549 A does not continue to increase with the UV continuum at
large flux levels. For the broad component, the ratio semiforbidden C
III 1909 A/C IV 1549 A is independent of the continuum luminosity,
suggesting a large ionization parameter. The Balmer decrement in the
broad component is smaller when the continuum is brighter. Ly-alpha and
H-gamma increase more than H-alpha and H-beta with increasing UV flux.
The He II lines are very broad and change by a factor of up to four.
They seem to react quickly to UV continuum changes, and there is no need
to invoke accretion events to explain their variability.
The Astrophysical Journal 04/1990; 354:446-467. · 6.73 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The on-line IUE Uniform Low Dispersion Archive (ULDA) and the associated ULDA Support Software Package (USSP) are described. The underlying philosophy, the detailed corrections made to the data and the implementation details are summarized. The low-resolution data are made available for direct access to the astronomical community through the existing computer networks. The USSP includes a selection mechanism and a mechanism to transfer the data selected from the national host to the end user's institute; it supports various data formats and requires only minimum user registration, and collects some usage information.
Astronomy and Astrophysics Supplement Series 01/1989;
[Show abstract][Hide abstract] ABSTRACT: Preliminary results are presented on the UV spectral evolution of SN
1987 A from IUE data obtained from February 25 to March 23, 1987. It is
suggested that line blanketing, mainly from Fe II, Ni II and Ti II,
variable with time, is probably responsible for the observed features.
Black body fitting to the UV-optical-infrared energy distribution on
February 25.2, February 26.3 and February 27.4, provides photospheric
radii which are consistent with the expansion velocity observed in
H-gamma, and with the event having taken place near the neutrino
Astronomy and Astrophysics 04/1987; 177:L29-L32. · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Early phase observations of the SN 1987A in the ultraviolet wavelength
range are presented. Some general considerations on the behaviour of
this supernova are given. Also, a comparison is made with other
supernovae observed in the ultraviolet with the IUE Observatory.
Astronomy and Astrophysics 04/1987; 177:L21-L24. · 5.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The autors use spatial and spectroscopic information from IUE spectra in the range 1,150 - 1,950 Å to demonstrate that Sk -69°202, the star coinciding positionally with the LMC supernova has disappeared from sight. Two weaker sources, named star 2 and star 3 in the astrometric analysis of the image of Sk -69°202 before the supernova outburst, are still present in the ultraviolet spectra. The authors isolate their spectra and give a spectral classification. They conclude that Sk -69°202 is the progenitor of the LMC supernova.
[Show abstract][Hide abstract] ABSTRACT: Difficulties in preparing the IUE low resolution spectra reference atlas
(Volume 2) of stars with anomalous spectra are outlined. It is
impossible to translate all peculiarity groups of the 3600 to 4800 A
region into similarly structured peculiarity groups in the 1200 to 3200
A region. Thus one finds the same phenomenon as with normal stars:
classifications based upon one spectral region have no strict
equivalence in another spectral region. Examples of Hg-Mn versus Ga
stars, Horizontal-Branch versus lambda Boo stars, hydrogen-deficient
versus C II stars, and the case of subdwarfs are shown.
[Show abstract][Hide abstract] ABSTRACT: Variations of the continuum and the strongest emission lines for NGC 5548 are presented. The relations between the lines and continuum show large variations in the Ba decrement - closer to recombination when brighter.