G. Szokoly

Max Planck Institute for Extraterrestrial Physics, Arching, Bavaria, Germany

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Publications (194)526.85 Total impact

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    ABSTRACT: This paper reports on an all-sky search for periodic gravitational waves from sources such as deformed isolated rapidly spinning neutron stars. The analysis uses 840 hours of data from 66 days of the fifth LIGO science run (S5). The data were searched for quasimonochromatic waves with frequencies f in the range from 50 to 1500 Hz, with a linear frequency drift f˙ (measured at the solar system barycenter) in the range -f/τ<f˙<0.1f/τ, for a minimum spin-down age τ of 1000 years for signals below 400 Hz and 8000 years above 400 Hz. The main computational work of the search was distributed over approximately 100 000 computers volunteered by the general public. This large computing power allowed the use of a relatively long coherent integration time of 30 hours while searching a large parameter space. This search extends Einstein@Home’s previous search in LIGO S4 data to about 3 times better sensitivity. No statistically significant signals were found. In the 125-225 Hz band, more than 90% of sources with dimensionless gravitational-wave strain tensor amplitude greater than 3×10^-24 would have been detected.
    Physical Review D 01/2013; 80(4):042003. DOI:10.1103/PhysRevD.80.042003 · 4.86 Impact Factor
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    ABSTRACT: Abadie, J. Abbott, B. P. Abbott, R. Abernathy, M. Accadia, T. Acernese, F. Adams, C. Adhikari, R. Ajith, P. Allen, B. Allen, G. S. Ceron, E. Amador Amin, R. S. Anderson, S. B. Anderson, W. G. Antonucci, F. Arain, M. A. Araya, M. C. Aronsson, M. Aso, Y. Aston, S. M. Astone, P. Atkinson, D. Aufmuth, P. Aulbert, C. Babak, S. Baker, P. Ballardin, G. Ballinger, T. Ballmer, S. Barker, D. Barnum, S. Barone, F. Barr, B. Barriga, P. Barsotti, L. Barsuglia, M. Barton, M. A. Bartos, I. Bassiri, R. Bastarrika, M. Bauchrowitz, J. Bauer, Th. S. Behnke, B. Beker, M. G. Belletoile, A. Benacquista, M. Bertolini, A. Betzwieser, J. Beveridge, N. Beyersdorf, P. T. Bilenko, I. A. Billingsley, G. Birch, J. Birindelli, S. Biswas, R. Bitossi, M. Bizouard, M. A. Black, E. Blackburn, J. K. Blackburn, L. Blair, D. Bland, B. Blom, M. Boccara, C. Bock, O. Bodiya, T. P. Bondarescu, R. Bondu, F. Bonelli, L. Bonnand, R. Bork, R. Born, M. Boschi, V. Bose, S. Bosi, L. Bouhou, B. Boyle, M. Braccini, S. Bradaschia, C. Brady, P. R. Bragin
    Physical Review D 04/2012; 85. DOI:10.1103/PhysRevD.85.089904 · 4.86 Impact Factor
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    ABSTRACT: We report on the surprisingly high metallicity measured in two absorption systems at high redshift, detected in the Very Large Telescope spectrum of the afterglow of the gamma-ray burst (GRB) GRB 090323. The two systems, at redshift z= 3.5673 and 3.5774 (separation Δv≈ 660 km s−1), are dominated by the neutral gas in the interstellar medium of the parent galaxies. From the singly ionized zinc and sulphur, we estimate oversolar metallicities of [Zn/H] =+0.29 ± 0.10 and [S/H] = +0.67 ± 0.34, in the blue and red absorber, respectively. These are the highest metallicities ever measured in galaxies at z > 3. We propose that the two systems trace two galaxies in the process of merging, whose star formation and metallicity are heightened by the interaction. This enhanced star formation might also have triggered the birth of the GRB progenitor. As typically seen in star-forming galaxies, the fine-structure absorption Si ii* is detected, both in z= 3.5774 ± 0.0005 and 3.5673 ± 0.0003. From the rest-frame ultraviolet emission in the GRB location, we derive a relatively high, not corrected for dust extinction, star formation rate ≈6 M⊙ yr−1. These properties suggest a possible connection between some high-redshift GRB host galaxies and high-z massive submillimetre galaxies, which are characterized by disturbed morphologies and high metallicities. Our result provides additional evidence that the dispersion in the chemical enrichment of the Universe at high redshift is substantial, with the existence of very metal-rich galaxies less than two billion years after the big bang.
    Monthly Notices of the Royal Astronomical Society 02/2012; 420(1):627 - 636. DOI:10.1111/j.1365-2966.2011.20074.x · 5.23 Impact Factor
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    ABSTRACT: We present the results of a LIGO search for gravitational waves (GWs) associated with GRB 051103, a short-duration hard-spectrum gamma-ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral galaxy M81, which is 3.6 Mpc from Earth. Possible progenitors for short-hard GRBs include compact object mergers and soft gamma repeater (SGR) giant flares. A merger progenitor would produce a characteristic GW signal that should be detectable at the distance of M81, while GW emission from an SGR is not expected to be detectable at that distance. We found no evidence of a GW signal associated with GRB 051103. Assuming weakly beamed gamma-ray emission with a jet semi-angle of 30 deg we exclude a binary neutron star merger in M81 as the progenitor with a confidence of 98%. Neutron star-black hole mergers are excluded with > 99% confidence. If the event occurred in M81 our findings support the the hypothesis that GRB 051103 was due to an SGR giant flare, making it the most distant extragalactic magnetar observed to date.
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    ABSTRACT: The gravitational-wave (GW) sky may include nearby pointlike sources as well as stochastic backgrounds. We perform two directional searches for persistent GWs using data from the LIGO S5 science run: one optimized for pointlike sources and one for arbitrary extended sources. Finding no evidence to support the detection of GWs, we present 90% confidence level (C.L.) upper-limit maps of GW strain power with typical values between 2-20×10(-50)  strain(2) Hz(-1) and 5-35×10(-49)  strain(2) Hz(-1) sr(-1) for pointlike and extended sources, respectively. The latter result is the first of its kind. We also set 90% C.L. limits on the narrow-band root-mean-square GW strain from interesting targets including Sco X-1, SN 1987A and the Galactic center as low as ≈7×10(-25) in the most sensitive frequency range near 160 Hz.
    Physical Review Letters 12/2011; 107(27):271102. DOI:10.1103/PhysRevLett.107.271102 · 7.73 Impact Factor
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    ABSTRACT: We report on the surprisingly high metallicity measured in two absorption systems at high redshift, detected in the Very Large Telescope spectrum of the afterglow of the gamma-ray burst GRB 090323. The two systems, at redshift z=3.5673 and z=3.5774 (separation Delta v ~ 660 km/s), are dominated by the neutral gas in the interstellar medium of the parent galaxies. From the singly ionized zinc and sulfur, we estimate oversolar metallicities of [Zn/H] =+0.29+/-0.10 and [S/H] = +0.67+/- 0.34, in the blue and red absorber, respectively. These are the highest metallicities ever measured in galaxies at z>3. We propose that the two systems trace two galaxies in the process of merging, whose star formation and metallicity are heightened by the interaction. This enhanced star formation might also have triggered the birth of the GRB progenitor. As typically seen in star-forming galaxies, the fine-structure absorption SiII* is detected, both in G0 and G1. From the rest-frame UV emission in the GRB location, we derive a relatively high, not corrected for dust extinction, star-formation rate SFR ~ 6 Msun/yr. These properties suggest a possible connection between some high-redshift GRB host galaxies and high-z massive sub-millimeter galaxies, which are characterized by disturbed morphologies and high metallicities. Our result provides additional evidence that the dispersion in the chemical enrichment of the Universe at high redshift is substantial, with the existence of very metal rich galaxies less than two billion years after the Big Bang.
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    ABSTRACT: We present direct upper limits on continuous gravitational wave emission from the Vela pulsar using data from the Virgo detector's second science run. These upper limits have been obtained using three independent methods that assume the gravitational wave emission follows the radio timing. Two of the methods produce frequentist upper limits for an assumed known orientation of the star's spin axis and value of the wave polarization angle of, respectively, 1.9 × 10–24 and 2.2 × 10–24, with 95% confidence. The third method, under the same hypothesis, produces a Bayesian upper limit of 2.1 × 10^–24, with 95% degree of belief. These limits are below the indirect spin-down limit of 3.3 × 10^–24 for the Vela pulsar, defined by the energy loss rate inferred from observed decrease in Vela's spin frequency, and correspond to a limit on the star ellipticity of ~10^–3. Slightly less stringent results, but still well below the spin-down limit, are obtained assuming the star's spin axis inclination and the wave polarization angles are unknown.
    The Astrophysical Journal 08/2011; 737(2):93. DOI:10.1088/0004-637X/737/2/93 · 6.28 Impact Factor
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    ABSTRACT: The X-ray observations of the Lockman Hole took place between April 2000 and December 2002 with XMM-Newton. The optical observations of the Lockman Hole were conducted with the Large Binocular Telescope (U-B-V bands) and the Subaru Telescope (RC-IC-z' bands). The LBT observations were taken from February 2007 to March 2009. The RC, IC, and z' bands have been observed with the Suprime-Cam of the Subaru telescope between November 2001 and April 2002. (1 data file).
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    ABSTRACT: Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are thought to be magnetars: neutron stars powered by extreme magnetic fields. These rare objects are characterized by repeated and sometimes spectacular gamma-ray bursts. The burst mechanism might involve crustal fractures and excitation of non-radial modes which would emit gravitational waves (GWs). We present the results of a search for GW bursts from six galactic magnetars that is sensitive to neutron star f-modes, thought to be the most efficient GW emitting oscillatory modes in compact stars. One of them, SGR 0501+4516, is likely ~1 kpc from Earth, an order of magnitude closer than magnetars targeted in previous GW searches. A second, AXP 1E 1547.0–5408, gave a burst with an estimated isotropic energy >1044 erg which is comparable to the giant flares. We find no evidence of GWs associated with a sample of 1279 electromagnetic triggers from six magnetars occurring between 2006 November and 2009 June, in GW data from the LIGO, Virgo, and GEO600 detectors. Our lowest model-dependent GW emission energy upper limits for band- and time-limited white noise bursts in the detector sensitive band, and for f-mode ringdowns (at 1090 Hz), are 3.0 × 1044 d 2 1 erg and 1.4 × 1047 d 2 1 erg, respectively, where and d 0501 is the distance to SGR 0501+4516. These limits on GW emission from f-modes are an order of magnitude lower than any previous, and approach the range of electromagnetic energies seen in SGR giant flares for the first time.
    The Astrophysical Journal Letters 05/2011; 734(2):L35. DOI:10.1088/2041-8205/734/2/L35 · 5.60 Impact Factor
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    ABSTRACT: We present direct upper limits on continuous gravitational wave emission from the Vela pulsar using data from the Virgo detector's second science run. These upper limits have been obtained using three independent methods that assume the gravitational wave emission follows the radio timing. Two of the methods produce frequentist upper limits for an assumed known orientation of the star's spin axis and value of the wave polarization angle of, respectively, $1.9\ee{-24}$ and $2.2\ee{-24}$, with 95% confidence. The third method, under the same hypothesis, produces a Bayesian upper limit of $2.1\ee{-24}$, with 95% degree of belief. These limits are below the indirect {\it spin-down limit} of $3.3\ee{-24}$ for the Vela pulsar, defined by the energy loss rate inferred from observed decrease in Vela's spin frequency, and correspond to a limit on the star ellipticity of $\sim 10^{-3}$. Slightly less stringent results, but still well below the spin-down limit, are obtained assuming the star's spin axis inclination and the wave polarization angles are unknown.
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    ABSTRACT: We present the observed-frame optical, near- and mid-infrared properties of X-ray selected AGN in the Lockman Hole. Using a likelihood ratio method on optical, near-infrared or mid-infrared catalogues, we assigned counterparts to 401 out of the 409 X-ray sources of the XMM-Newton catalogue. Accurate photometry was collected for all the sources from U to 24um. We used X-ray and optical criteria to remove any normal galaxies, galactic stars, or X-ray clusters among them and studied the multi-wavelength properties of the remaining 377 AGN. We used a mid-IR colour-colour selection to understand the AGN contribution to the optical and infrared emission. Using this selection, we identified different behaviours of AGN-dominated and host-dominated sources in X-ray-optical-infrared colour-colour diagrams. More specifically, the AGN dominated sources show a clear trend in the f_x/f_R vs. R-K and f_24um/f_R vs. R-K diagrams, while the hosts follow the behaviour of non X-ray detected galaxies. In the optical-near-infrared colour-magnitude diagram we see that the known trend of redder objects being more obscured in X-rays is stronger for AGN-dominated than for host-dominated systems. This is an indication that the trend is more related to the AGN contaminating the overall colours than any evolutionary effects. Finally, we find that a significant fraction (~30%) of the reddest AGN are not obscured in X-rays.
    Astronomy and Astrophysics 02/2011; 529. DOI:10.1051/0004-6361/201015763 · 4.48 Impact Factor
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    ABSTRACT: We present the first modeled search for gravitational waves using the complete binary black hole gravitational waveform from inspiral through the merger and ringdown for binaries with negligible component spin. We searched approximately 2 years of LIGO data taken between November 2005 and September 2007 for systems with component masses of 1-99 solar masses and total masses of 25-100 solar masses. We did not detect any plausible gravitational-wave signals but we do place upper limits on the merger rate of binary black holes as a function of the component masses in this range. We constrain the rate of mergers for binary black hole systems with component masses between 19 and 28 solar masses and negligible spin to be no more than 2.0 per Mpc^3 per Myr at 90% confidence.
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    ABSTRACT: The physical mechanisms responsible for pulsar timing glitches are thought to excite quasinormal mode oscillations in their parent neutron star that couple to gravitational-wave emission. In August 2006, a timing glitch was observed in the radio emission of PSR B0833-45, the Vela pulsar. At the time of the glitch, the two colocated Hanford gravitational-wave detectors of the Laser Interferometer Gravitational-wave observatory (LIGO) were operational and taking data as part of the fifth LIGO science run (S5). We present the first direct search for the gravitational-wave emission associated with oscillations of the fundamental quadrupole mode excited by a pulsar timing glitch. No gravitational-wave detection candidate was found. We place Bayesian 90% confidence upper limits of 6.3×10-21 to 1.4×10-20 on the peak intrinsic strain amplitude of gravitational-wave ring-down signals, depending on which spherical harmonic mode is excited. The corresponding range of energy upper limits is 5.0×1044 to 1.3×1045erg.
    Physical review D: Particles and fields 02/2011; DOI:10.1103/PhysRevD.83.042001 · 4.86 Impact Factor
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    ABSTRACT: Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs) are thought to be magnetars: neutron stars powered by extreme magnetic fields. These rare objects are characterized by repeated and sometimes spectacular gamma-ray bursts. The burst mechanism might involve crustal fractures and excitation of non-radial modes which would emit gravitational waves (GWs). We present the results of a search for GW bursts from six galactic magnetars that is sensitive to neutron star f-modes, thought to be the most efficient GW emitting oscillatory modes in compact stars. One of them, SGR 0501+4516, is likely ~1 kpc from Earth, an order of magnitude closer than magnetars targeted in previous GW searches. A second, AXP 1E 1547.0-5408, gave a burst with an estimated isotropic energy >10^{44} erg which is comparable to the giant flares. We find no evidence of GWs associated with a sample of 1279 electromagnetic triggers from six magnetars occurring between November 2006 and June 2009, in GW data from the LIGO, Virgo, and GEO600 detectors. Our lowest model-dependent GW emission energy upper limits for band- and time-limited white noise bursts in the detector sensitive band, and for f-mode ringdowns (at 1090 Hz), are 3.0x10^{44} d_1^2 erg and 1.4x10^{47} d_1^2 erg respectively, where d_1 = d_{0501} / 1 kpc and d_{0501} is the distance to SGR 0501+4516. These limits on GW emission from f-modes are an order of magnitude lower than any previous, and approach the range of electromagnetic energies seen in SGR giant flares for the first time.
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    ABSTRACT: The physical mechanisms responsible for pulsar timing glitches are thought to excite quasi-normal mode oscillations in their parent neutron star that couple to gravitational wave emission. In August 2006, a timing glitch was observed in the radio emission of PSR B0833-45, the Vela pulsar. At the time of the glitch, the two co-located Hanford gravitational wave detectors of the Laser Interferometer Gravitational-wave observatory (LIGO) were operational and taking data as part of the fifth LIGO science run (S5). We present the first direct search for the gravitational wave emission associated with oscillations of the fundamental quadrupole mode excited by a pulsar timing glitch. No gravitational wave detection candidate was found. We place Bayesian 90% confidence upper limits of 6.3e-21 to 1.4e-20 on the peak intrinsic strain amplitude of gravitational wave ring-down signals, depending on which spherical harmonic mode is excited. The corresponding range of energy upper limits is 5.0e44 to 1.3e45 erg.
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    ABSTRACT: We have acquired optical spectra with the VLT, using the Visible Multi-Object Spectrograph (VIMOS) in Oct-Dec 2004, Jan and Oct 2005, Dec 2007 and Jan-Feb 2008. We have carried out two pointings, each with two different setups, in the northern half of the E-CDF-S field. Optical spectra were also obtained in January of 2007, 2008, and 2010 on Keck II with the Deep Imaging Multi-object Spectrograph (DEIMOS). (3 data files).
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    ABSTRACT: We present the results of a program to acquire high-quality optical spectra of X-ray sources detected in the E-CDF-S and its central area. New spectroscopic redshifts are measured for 283 counterparts to Chandra sources with deep exposures (t~2-9 hr per pointing) using multi-slit facilities on both the VLT and Keck thus bringing the total number of spectroscopically-identified X-ray sources to over 500 in this survey field. We provide a comprehensive catalog of X-ray sources detected in the E-CDF-S including the optical and near-infrared counterparts, and redshifts (both spectroscopic and photometric) that incorporate published spectroscopic catalogs thus resulting in a final sample with a high fraction (80%) of X-ray sources having secure identifications. We demonstrate the remarkable coverage of the Lx-z plane now accessible from our data while emphasizing the detection of AGNs that contribute to the faint end of the luminosity function at 1.5<z<3. Our redshift catalog includes 17 type 2 QSOs that significantly increases such samples (2x). With our deepest VIMOS observation, we identify "elusive" optically-faint galaxies (R~25) at z~2-3 based upon the detection of interstellar absorption lines; we highlight one such case, an absorption-line galaxy at z=3.208 having no obvious signs of an AGN in its optical spectrum. In addition, we determine distances to eight galaxy groups with extended X-ray emission. Finally, we measure the physical extent of known large-scale structures (z~0.7) evident in the CDF-S. While a thick sheet (radial size of 67.7 Mpc) at z~0.67 extends over the full field, the z~0.73 structure is thin (18.8 Mpc) and filamentary as traced by both AGNs and galaxy groups. In the appendix, we provide spectroscopic redshifts for 49 counterparts to fainter X-ray sources detected only in the 1 and 2 Ms catalogs, and 48 VLA radio sources not detected in X-rays.
    The Astrophysical Journal Supplement Series 10/2010; 191(1):124. DOI:10.1088/0067-0049/191/1/124 · 14.14 Impact Factor
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    ABSTRACT: We present the results of a comprehensive study of the gamma-ray burst 080928 and of its afterglow. GRB 080928 was a long burst detected by Swift/BAT and Fermi/GBM. It is one of the exceptional cases where optical emission had already been detected when the GRB itself was still radiating in the gamma-ray band. For nearly 100 seconds simultaneous optical, X-ray and gamma-ray data provide a coverage of the spectral energy distribution of the transient source from about 1 eV to 150 keV. In particular, we show that the SED during the main prompt emission phase agrees with synchrotron radiation. We constructed the optical/near-infrared light curve and the spectral energy distribution based on Swift/UVOT, ROTSE-IIIa (Australia), and GROND (La Silla) data and compared it to the X-ray light curve retrieved from the Swift/XRT repository. We show that its bumpy shape can be modeled by multiple energy-injections into the forward shock.Furthermore, we investigate whether the temporal and spectral evolution of the tail emission of the first strong flare seen in the early X-ray light curve can be explained by large-angle emission (LAE). We find that a nonstandard LAE model is required to explain the observations. Finally, we report on the results of our search for the GRB host galaxy, for which only a deep upper limit can be provided.
    Astronomy and Astrophysics 07/2010; DOI:10.1051/0004-6361/201015324 · 4.48 Impact Factor
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    ABSTRACT: We used the large binocular camera (LBC) mounted on the Large Binocular Telescope (LBT) to observe the Lockman Hole in the U, B, and V bands. Our observations cover an area of 900 arcmin2. We reached depths of 26.7, 26.3, and 26.3 mag(AB) in the three bands, respectively, in terms of 50% source detection efficiency. We extracted a large number of sources (˜89000), detected in all three bands and examined their surface density, comparing it with models of galaxy evolution. We find good agreement with previous claims of a steep faint-end slope of the luminosity functions, caused by late-type and irregular galaxies at z>1.5. A population of dwarf star-forming galaxies at 1.5
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    ABSTRACT: Progenitor scenarios for short gamma-ray bursts (short GRBs) include coalescenses of two neutron stars or a neutron star and black hole, which would necessarily be accompanied by the emission of strong gravitational waves. We present a search for these known gravitational-wave signatures in temporal and directional coincidence with 22 GRBs that had sufficient gravitational-wave data available in multiple instruments during LIGO's fifth science run, S5, and Virgo's first science run, VSR1. We find no statistically significant gravitational-wave candidates within a [ – 5, + 1) s window around the trigger time of any GRB. Using the Wilcoxon-Mann-Whitney U-test, we find no evidence for an excess of weak gravitational-wave signals in our sample of GRBs. We exclude neutron star-black hole progenitors to a median 90% confidence exclusion distance of 6.7 Mpc.
    The Astrophysical Journal 05/2010; 715(2):1453. DOI:10.1088/0004-637X/715/2/1453 · 6.28 Impact Factor

Publication Stats

9k Citations
526.85 Total Impact Points

Institutions

  • 2002–2012
    • Max Planck Institute for Extraterrestrial Physics
      Arching, Bavaria, Germany
    • Brown University
      • Department of Physics
      Providence, Rhode Island, United States
  • 2011
    • California Institute of Technology
      • Department of Physics
      Pasadena, California, United States
  • 2009–2011
    • Eötvös Loránd University
      • Institute of Physics
      Budapest, Budapest fovaros, Hungary
  • 2008
    • Thüringer Landessternwarte Tautenburg
      Tautenburg, Thuringia, Germany
  • 2006
    • Honolulu University
      Honolulu, Hawaii, United States
  • 2005
    • Università Degli Studi Roma Tre
      Roma, Latium, Italy
    • University of Illinois, Urbana-Champaign
      • Department of Astronomy
      Urbana, Illinois, United States
  • 2004
    • Università degli Studi di Trieste
      Trst, Friuli Venezia Giulia, Italy
  • 2001
    • University of Michigan
      • Department of Physics
      Ann Arbor, Michigan, United States
  • 2000–2001
    • Pennsylvania State University
      • Department of Astronomy and Astrophysics
      University Park, Maryland, United States
  • 1998
    • Johns Hopkins University
      • Department of Physics and Astronomy
      Baltimore, Maryland, United States