A. Talavera

European University of Madrid, Madrid, Madrid, Spain

Are you A. Talavera?

Claim your profile

Publications (35)92.58 Total impact

  • Source
    [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. DOI:10.1088/0004-637X/745/1/43 · 6.28 Impact Factor
  • Antonio Talavera, OMCal Team
    [Show abstract] [Hide abstract]
    ABSTRACT: The XMM-Newton X-ray observatory was launched at the end of 1999 and it is still successfully operated. In addition to the X-ray instruments, the payload carries a small telescope, the Optical Monitor, which provides simultaneous imaging and spectroscopic observations in the optical and UV ranges. In this report we review the status of the OM and its main achievements after 10 years of operations. We also introduce the XMM-OM Serendipitous Ultra-violet Source Survey (SUSS) Catalogue. KeywordsInstruments–Ultraviolet–Optical–Photometry–Spectra
    Astrophysics and Space Science 09/2011; 335(1):291-296. DOI:10.1007/s10509-011-0708-8 · 2.40 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The Wolf-Rayet star WR 46 is known to exhibit a very complex variability pattern on relatively short time scales of a few hours. Periodic but intermittent radial velocity shifts of optical lines as well as multiple photometric periods have been found in the past. Non-radial pulsations, rapid rotational modulation or the presence of a putative low-mass companion have been proposed to explain the short-term behaviour. In an effort to unveil its true nature, we observed WR 46 with FUSE (Far Ultraviolet Spectroscopic Explorer) over several short-term variability cycles. We found significant variations on a time scale of ~8 hours in the far-ultraviolet (FUV) continuum, in the blue edge of the absorption trough of the OVI {\lambda}{\lambda}1032, 1038 doublet P Cygni profile and in the SVI {\lambda}{\lambda}933, 944 P Cygni absorption profile. We complemented these observations with X-ray and UV light-curves and an X-ray spectrum from archival XMM-Newton (X-ray Multi-Mirror Mission - Newton Space Telescope) data. The X-ray and UV light-curves show variations on a time scale similar to the variability found in the FUV. We discuss our results in the context of the different scenarios suggested to explain the short-term variability of this object and reiterate that non-radial pulsations is the most likely to occur.
    The Astrophysical Journal 04/2011; 735(1). DOI:10.1088/0004-637X/735/1/13 · 6.28 Impact Factor
  • Antonio Talavera, OMCal Team
    [Show abstract] [Hide abstract]
    ABSTRACT: The Optical and UV Monitor (OM), is a small telescope co-aligned with the main XMM-Newton X-ray telescopes. It can perform imaging with six broad band lenticular filters covering the range 180 nm to 600 nm. In addition, two grisms allow the user to obtain low resolution spectra in the same range. The detector is an intensified CCD. The instrument is fully calibrated in the standard UBV Johnson system and also in absolute flux for both filters and grisms. We describe the instrument and its calibration. We present some results and usage statistics.
    Astrophysics and Space Science 01/2009; 320(1):177-180. DOI:10.1007/s10509-008-9760-4 · 2.40 Impact Factor
  • Source
    [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.
    01/2001; 238:152.
  • Source
    [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 http://ines.vilspa.esa.es.
    01/2001; 238:156.
  • [Show abstract] [Hide abstract]
    ABSTRACT: The REMOT (Remote Experiment Monitoring and conTrol) project was financed by 1996 by the European Community in order to investigate the possibility of generalizing the remote access to scientific instruments. After the feasibility of this idea was demonstrated, the DYNACORE (DYNAmically, COnfigurable Remote Experiment monitoring and control) project was initiated as a REMOT follow-up. Its purpose is to develop software technology to support scientists in two different domains, astronomy and plasma physics. The resulting system allows (1) simultaneous multiple user access to different experimental facilities, (2) dynamic adaptability to different kinds of real instruments, (3) exploitation of the communication infrastructures features, (4) ease of use through intuitive graphical interfaces, and (5) additional inter-user communication using off-the-shelf projects such as video-conference tools, chat programs and shared blackboards.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
  • Source
    [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; DOI:10.1051/aas:2000316 · 1.75 Impact Factor
  • Source
    [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. DOI:10.1086/192185 · 14.14 Impact Factor
  • A. Talavera, J. D. Ponz
  • J. Murray, C. Driessen, A. Talavera
    08/1990;
  • Source
    [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(2):446-467. DOI:10.1086/168707 · 6.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: IAUC 4959 available at Central Bureau for Astronomical Telegrams. IAUC 4959 available at Central Bureau for Astronomical Telegrams.
    02/1990;
  • Source
    [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; · 1.75 Impact Factor
  • Source
  • [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.
    Nature 07/1987; 328(6128). DOI:10.1038/328318a0 · 42.35 Impact Factor
  • Source
    [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. · 4.48 Impact Factor

Publication Stats

230 Citations
92.58 Total Impact Points

Institutions

  • 2009–2011
    • European University of Madrid
      Madrid, Madrid, Spain
  • 1987
    • University of Catania
      Catania, Sicily, Italy
    • Space Telescope Science Institute
      Baltimore, Maryland, United States
  • 1986
    • University of Oxford
      Oxford, England, United Kingdom