A. Talavera

European University of Madrid, Madrid, Madrid, Spain

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Publications (39)96.91 Total impact

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    ABSTRACT: The XMM-Newton X-ray observatory has performed repeated observations of the CDFS in 33 epochs (2001-2010) through the XMM-CDFS Deep Survey. During the X-ray observations, XMM-OM targeted the central 17x17 arcmin2 region of the X-ray field of view, providing simultaneous optical/UV coverage of the CDFS. The resulting set of data can be taken into account to build an XMM-OM catalogue of the CDFS, filling the UV spectral coverage between the optical surveys and GALEX observations. We present the UV catalogue of the XMM-CDFS Deep Survey. Its main purpose is to provide complementary UV average photometric measurements of known optical/UV sources in the CDFS, taking advantage of the unique characteristics of the survey. The data reduction is intended also to improve the standard source detection on individual observations, by cataloguing faint sources through the stacking of their exposure images. We reprocessed the XMM-OM data of the survey and we stacked the exposures from consecutive observations using the standard SAS tools to process the data obtained during single observations. Average measurements of detections with SAS good quality flags from individual observations and from stacked images have been joined to compile the catalogue. Sources have been validated through the cross-identification within the EIS and COMBO-17 surveys. Photometric data of 1129 CDFS sources are provided into the catalogue, and optical/UV/X-ray photometric and spectroscopic information from other surveys are also included. The stacking extends the detection limits by ~1 mag in the three UV bands, contributing 30% of the catalogued UV sources. The comparison with the available measurements in similar spectral bands confirms the validity of the XMM-OM calibration. The combined COMBO-17/X-ray classification of the "intermediate" sources (e.g. optically diluted and/or X-ray absorbed AGN) is also discussed.
    Full-text · Article · Nov 2014 · Astronomy and Astrophysics
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    ABSTRACT: The XMM-Newton Serendipitous Ultraviolet Source Survey (XMM-SUSS) is a catalogue of ultraviolet (UV) sources detected serendipitously by the Optical Monitor (XMM-OM) on-board the XMM-Newton observatory. The catalogue contains ultraviolet-detected sources collected from 2,417 XMM-OM observations in 1-6 broad band UV and optical filters, made between 24 February 2000 and 29 March 2007. The primary contents of the catalogue are source positions, magnitudes and fluxes in 1 to 6 passbands, and these are accompanied by profile diagnostics and variability statistics. The XMM-SUSS is populated by 753,578 UV source detections above a 3 sigma signal-to-noise threshold limit which relate to 624,049 unique objects. Taking account of substantial overlaps between observations, the net sky area covered is 29-54 square degrees, depending on UV filter. The magnitude distributions peak at 20.2, 20.9 and 21.2 in UVW2, UVM2 and UVW1 respectively. More than 10 per cent of sources have been visited more than once using the same filter during XMM-Newton operation, and > 20 per cent of sources are observed more than once per filter during an individual visit. Consequently, the scope for science based on temporal source variability on timescales of hours to years is broad. By comparison with other astrophysical catalogues we test the accuracy of the source measurements and define the nature of the serendipitous UV XMM-OM source sample. The distributions of source colours in the UV and optical filters are shown together with the expected loci of stars and galaxies, and indicate that sources which are detected in multiple UV bands are predominantly star-forming galaxies and stars of type G or earlier.
    Full-text · Article · Jul 2012 · Monthly Notices of the Royal Astronomical Society
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    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.
    Full-text · Article · Dec 2011 · The Astrophysical Journal
  • Antonio Talavera · OMCal Team
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    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
    No preview · Article · Sep 2011 · Astrophysics and Space Science
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    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.
    Full-text · Article · Apr 2011 · The Astrophysical Journal
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    ABSTRACT: Virtual Observatory functionality has been used extensively to determine the properties and test the accuracy of the XMM-Newton serendipitous ultraviolet source sample against objects within the Sloan optical and GALEX UV data archives. We report on the successes and perceived limitations of this process.
    No preview · Article · Jul 2009
  • Antonio Talavera · OMCal Team
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    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.
    No preview · Article · Jan 2009 · Astrophysics and Space Science

  • No preview · Article · Jul 2008
  • A. Talavera · R. González-Riestra · E. Solano

    No preview · Article · Jan 2001
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    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.
    Full-text · Article · Jan 2001
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    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.
    Full-text · Article · Jan 2001
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    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.
    No preview · Article · Jun 2000
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    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
    Full-text · Article · Oct 1999 · Astronomy and Astrophysics Supplement Series
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    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.
    Full-text · Article · Jun 1995 · The Astrophysical Journal Supplement Series

  • No preview · Article · Jan 1994

  • No preview · Article · Sep 1992
  • A. Talavera · J. D. Ponz

    No preview · Article · Aug 1991
  • J. Murray · C. Driessen · A. Talavera

    No preview · Article · Aug 1990
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    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.
    Full-text · Article · Apr 1990 · The Astrophysical Journal
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    ABSTRACT: IAUC 4959 available at Central Bureau for Astronomical Telegrams. IAUC 4959 available at Central Bureau for Astronomical Telegrams.
    No preview · Article · Feb 1990

Publication Stats

280 Citations
96.91 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