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Mennella V.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Capodimonte | Hornekaer L.,University of Aarhus | Thrower J.,University of Aarhus | Accolla M.,Parthenope University of Naples
Astrophysical Journal Letters | Year: 2012

We present the results of an experimental study on the interaction of atomic deuterium with coronene films. The effects of Datom irradiation have been analyzed with infrared spectroscopy. The spectral changes provide evidence for deuteration of the outer edge coronene C sites via a D addition reaction. A cross section of 1.1 2 is estimated for the deuteration process of coronene. HD and D2 molecules form, through abstraction reactions, on deuterated coronene sites with a cross section of 0.06 2. The magnitude of both cross sections is in line with an Eley-Rideal type process. The results show that hydrogenated neutral polycyclic aromatic hydrocarbon molecules act as catalysts for the formation of molecular hydrogen. © 2012. The American Astronomical Society. All rights reserved.

Van Putten M.H.P.M.,Korea Institute for Advanced Study | Kanda N.,Osaka City University | Tagoshi H.,Osaka City University | Tatsumi D.,Japan National Astronomical Observatory | And 3 more authors.
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

Observational evidence for black hole spin down has been found in the normalized light curves of long gamma-ray bursts in the BATSE catalog. Over the duration T90 of the burst, matter swept up by the central black hole is susceptible to nonaxisymmetries, producing gravitational radiation with a negative chirp. A time-sliced matched filtering method is introduced to capture phase coherence on intermediate time scales, τ, here tested by the injection of templates into experimental strain noise, hn(t). For TAMA 300, hn(f) 10-21Hz-1/2 at f=1kHz gives a sensitivity distance for a reasonably accurate extraction of the trajectory in the time-frequency domain of about D 0.07-0.10Mpc for the spin down of black holes of mass M=10-12M with τ=1s. Extrapolation to advanced detectors implies D 35-50Mpc for hn(f) 2×10-24Hz -1/2 around 1 kHz, which will open a new window to rigorous calorimetry on Kerr black holes. © 2011 American Physical Society.

Fabrizio M.,University of Rome Tor Vergata | Merle T.,University of Nice Sophia Antipolis | Thevenin F.,University of Nice Sophia Antipolis | Nonino M.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Trieste | And 22 more authors.
Publications of the Astronomical Society of the Pacific | Year: 2012

We have performed accurate iron abundance measurements for 44 red giants (RGs) in the Carina dwarf spheroidal (dSph) galaxy. We used archival, high-resolution spectra (R ~ 38, 000) collected with UVES at ESO/VLT either in slit mode (five RGs) or in fiber mode (39 RGs, FLAMES/GIRAFFE-UVES). The sample is more than a factor of 4 larger than any previous spectroscopic investigation of stars in dSphs based on high-resolution (R ≥ 38000) spectra. We did not impose the ionization equilibrium between neutral and singly ionized iron lines. The effective temperatures and the surface gravities were estimated by fitting stellar isochrones in the V, B - V color-magnitude diagram. To measure the iron abundance of individual lines we applied the LTE spectrum-synthesis fitting method using MARCS model atmospheres of appropriate metallicity. For the 27 stars for which we measured both Fe I and Fe II abundances, we found evidence of NLTE effects between neutral and singly ionized iron abundances. The difference is ~0.1 dex, on average, but steadily increases when moving from the metal-rich to the metal-poor regime. Moreover, the two metallicity distributions differ at the 97% confidence level. Assuming that the Fe II abundances are minimally affected by NLTE effects, we corrected the Fe I stellar abundances using a linear fit between Fe I and Fe II stellar abundance determinations. We found that the Carina metallicity distribution based on the corrected Fe I abundances (44 RGs) has a weighted mean metallicity of [Fe/H] = -1.80 and a weighted standard deviation of σ = 0.24 dex. The Carina metallicity distribution based on the Fe II abundances (27 RGs) gives similar estimates ([Fe/H] = -1.72, σ = 0.24 dex). The current weighted mean metallicities are slightly more metal-poor when compared with similar estimates available in the literature. Furthermore, when we restricted our analysis to stars with the most accurate iron abundances, ~20 Fe I and at least three Fe II measurements (15 stars), we found that the range in iron abundances covered by Carina RGs (~1 dex) agreed quite well with similar estimates based on high-resolution spectra; however, it is a factor of 2-3 smaller than abundance estimates based on the near-infrared calcium triplet. This finding supports previous estimates based on photometric metallicity indicators. © 2012. The Astronomical Society of the Pacific. All rights reserved.

Schipani P.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Capodimonte | Arcidiacono C.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Bologna | Argomedo J.,European Southern Observatory | Dall'Ora M.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Capodimonte | And 6 more authors.
Review of Scientific Instruments | Year: 2012

The VLT survey telescope is the latest telescope installed at European Southern Observatorys Paranal observatory that is considered one of the best sites for optical astronomy for the excellent seeing conditions. The exceptional quality of the site imposes tight requirements for the telescope tracking system that shall perform very well to fully exploit the extreme sharpness of the Chilean sky. We describe the specific solutions adopted for pointing, servo and guiding systems and the results obtained during the commissioning of the telescope. The hardware implementation relies on industry components and the control solutions privilege both the performance and the future maintainability of the system. © 2012 American Institute of Physics.

Schipani P.,Istituto Nazionale di Astrofisica Osservatorio Astronomico di Capodimonte | Noethe L.,European Southern Observatory | Arcidiacono C.,Istituto Nazionale di Astrofisica Osservatorio Astrofisico di Arcetri | Argomedo J.,European Southern Observatory | And 7 more authors.
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2012

The wavefront sensor in active and adaptive telescopes is usually not in the optical path toward the scientific detector. It may generate additional wavefront aberrations, which have to be separated from the errors due to the telescope optics. The aberrations that are not rotationally symmetric can be disentangled from the telescope aberrations by a series of measurements taken in the center of the field, with the wavefront sensor at different orientation angles with respect to the focal plane. This method has been applied at the VLT Survey Telescope on the ESO Paranal observatory. © 2012 Optical Society of America.

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