416 research outputs found
Signatures of rocky planet engulfment in HAT-P-4. Implications for chemical tagging studies
Aims. To explore the possible chemical signature of planet formation in the
binary system HAT-P-4, by studying abundance vs condensation temperature Tc
trends. The star HAT-P-4 hosts a planet detected by transits while its stellar
companion does not have any detected planet. We also study the Lithium content,
which could shed light on the problem of Li depletion in exoplanet host stars.
Conclusions. The exoplanet host star HAT-P-4 is found to be ~0.1 dex more metal
rich than its companion, which is one of the highest differences in metallicity
observed in similar systems. This could have important implications for
chemical tagging studies, disentangling groups of stars with a common origin.
We rule out a possible peculiar composition for each star as lambda Boo, delta
Scuti or a Blue Straggler. The star HAT-P-4 is enhanced in refractory elements
relative to volatile when compared to its stellar companion. Notably, the
Lithium abundance in HAT-P-4 is greater than in its companion by ~0.3 dex,
which is contrary to the model that explains the Lithium depletion by the
presence of planets. We propose a scenario where, at the time of planet
formation, the star HAT-P-4 locked the inner refractory material in
planetesimals and rocky planets, and formed the outer gas giant planet at a
greater distance. The refractories were then accreted onto the star, possibly
due to the migration of the giant planet. This explains the higher metallicity,
the higher Lithium content, and the negative Tc trend detected. A similar
scenario was recently proposed for the solar twin star HIP 68468, which is in
some aspects similar to HAT-P-4. We estimate a mass of at least Mrock ~ 10
Mearth locked in refractory material in order to reproduce the observed Tc
trends and metallicity.Comment: 5 pages, 6 figures, A&A Letters accepte
High-precision analysis of binary stars with planets. I. Searching for condensation temperature trends in the HD 106515 system
We explore the probable chemical signature of planet formation in the
remarkable binary system HD 106515. The A star hosts a massive long-period
planet with 9 MJup detected by radial velocity. We also refine stellar and
planetary parameters by using non-solar-scaled opacities when modeling the
stars. Methods. We carried out a simultaneous determination of stellar
parameters and abundances, by applying for the first time non-solar-scaled
opacities in this binary system, in order to reach the highest possible
precision. Results. The stars A and B in the binary system HD 106515 do not
seem to be depleted in refractory elements, which is different when comparing
the Sun with solar-twins. Then, the terrestrial planet formation would have
been less efficient in the stars of this binary system. Together with HD
80606/7, this is the second binary system which does not seem to present a
(terrestrial) signature of planet formation, and hosting both systems an
eccentric giant planet. This is in agreement with numerical simulations, where
the early dynamical evolution of eccentric giant planets clear out most of the
possible terrestrial planets in the inner zone. We refined the stellar mass,
radius and age for both stars and found a notable difference of 78% in R
compared to previous works. We also refined the planet mass to mp sini = 9.08
+/- 0.20 MJup, which differs by 6% compared with literature. In addition, we
showed that the non-solar-scaled solution is not compatible with the classical
solar-scaled method, and some abundance differences are comparable to NLTE or
GCE effects specially when using the Sun as reference. Then, we encourage the
use of non-solar-scaled opacities in high-precision studies such as the
detection of Tc trends.[abridged]Comment: 9 pages, 10 figures, A&A accepted. arXiv admin note: text overlap
with arXiv:1507.0812
Quantum-dot based nanothermometry in optical plasmonic recording media
We report on the direct experimental determination of the temperature increment caused by laser irradiation in a optical recording media constituted by a polymeric film in which gold nanorods have been incorporated. The incorporation of CdSe quantum dots in the recording media allowed for single beam thermal reading of the on-focus temperature from a simple analysis of the two-photon excited fluorescence of quantum dots. Experimental results have been compared with numerical simulations revealing an excellent agreement and opening a promising avenue for further understanding and optimization of optical writing processes and media
Absorption efficiency of gold nanorods determined by quantum dot fluorescence thermometry
In this work quantum dot fluorescence thermometry, in combination with double-beam confocal microscopy, has been applied to determine the thermal loading of gold nanorods when subjected to an optical excitation at the longitudinal surface plasmon resonance. The absorbing/heating efficiency of low (≈3) aspect ratio gold nanorods has been experimentally determined to be close to 100%, in excellent agreement with theoretical simulations of the extinction, absorption, and scattering spectra based on the discrete dipole approximation
Low X-Ray Luminosity Galaxy Clusters: Main goals, sample selection, photometric and spectroscopic observations
We present the study of nineteen low X-ray luminosity galaxy clusters (L 0.5--45 erg s), selected from the ROSAT
Position Sensitive Proportional Counters (PSPC) Pointed Observations (Vikhlinin
et al. 1998) and the revised version of Mullis et al. (2003) in the redshift
range of 0.16 to 0.7. This is the introductory paper of a series presenting the
sample selection, photometric and spectroscopic observations and data
reduction. Photometric data in different passbands were taken for eight galaxy
clusters at Las Campanas Observatory; three clusters at Cerro Tololo
Interamerican Observatory; and eight clusters at the Gemini Observatory.
Spectroscopic data were collected for only four galaxy clusters using Gemini
telescopes. With the photometry, the galaxies were defined based on the
star-galaxy separation taking into account photometric parameters. For each
galaxy cluster, the catalogues contain the PSF and aperture magnitudes of
galaxies within the 90\% completeness limit. They are used together with
structural parameters to study the galaxy morphology and to estimate
photometric redshifts. With the spectroscopy, the derived galaxy velocity
dispersion of our clusters ranged from 507 km~s for [VMF98]022 to 775
km~s for [VMF98]097 with signs of substructure. Cluster membership has
been extensively discussed taking into account spectroscopic and photometric
redshift estimates. In this sense, members are the galaxies within a projected
radius of 0.75 Mpc from the X-ray mission peak and with cluster centric
velocities smaller than the cluster velocity dispersion or 6000 km~s,
respectively. These results will be used in forthcoming papers to study, among
the main topics, the red cluster sequence, blue cloud and green populations;
the galaxy luminosity function and cluster dynamics.Comment: 13 pages, 6 tables, 9 figures. Uses emulateapj. Accepted for
publication in The Astronomical Journal. Some formatting errors fixe
Anisotropic pinning enhancement in Nb films with arrays of submicrometric Ni lines
Arrays of submicrometric Ni lines have been fabricated in superconducting Nb films by electron beam lithography. In the mixed state, these arrays induce strong anisotropy in the dissipation behavior. The dissipation is reduced several orders of magnitude, in the whole applied magnetic field range, when the vortex motion is perpendicular to the Ni lines (applied current parallel to them) in comparison with dissipation of vortices moving parallel to the lines. In addition, for the samples studied in this work, a change in the slope of the ρ(B) curves is observed when the vortices move perpendicular to the lines and the vortex lattice parameter matches the width of the Ni lines. © 2002 American Institute of Physics.The authors want to thank Spanish CICYT MAT2002-
04543 and ESF Vortex program. D.J. and E.M.G. thank Ministerio de Ciencia y Tecnologı´a ~Spain! for Ramo´n y Cajal
Contracts.Peer reviewe
Anisotropic lattice changes in femtosecond laser inscribed Nd3+:MgO:LiNbO3 optical waveguides
We report on the fabrication and microspectroscopy imaging of femtosecond laser written
double-filament based Nd3+ :MgO:LiNbO3 optical waveguides. The waveguiding high
refractive-index regions are identified by blueshifts of the Nd3+ ion fluorescence lines with no
deterioration in the fluorescence efficiency, whereas filamentary low-index regions are identified by
both a Nd3+ line redshift and a fluorescence efficiency reduction. The lattice structural
micromodifications at the origin of both waveguide formation and Nd3+ fluorescence changes have
been investigated by means of confocal micro-Raman experiments. We have found that the direct
laser written filaments are mainly constituted by a large density of defects, together with a marked
axial compression perpendicular to the filaments �along the optical c-axis�. Conversely, the
high-index waveguiding regions are characterized by a pronounced anisotropic dilatation of the
LiNbO3 lattice xy-planes
Interrupted Vs. Uninterrupted Training on BMD During Growth
This study compared a resistance training program where the exercise was uninterrupted (UT, i.e., continuous repetitions) against a resistance training program where the exercise was interrupted (IT, i.e., 3 exercise sessions during a training day) for enhancing bone modeling and bone mineral density (BMD) in maturating animals. The total volume of work performed between the two resistance training programs was equivalent by design. 24 young male rats were randomly divided into Control (Con, n = 8), UT (n = 8) and IT (n=8) resistance trained groups. The UT and IT groups were conditioned to climb a vertical ladder with weights appended to their tail 3 days/wk for 6 wks. After the 6-wk program, serum osteocalcin was not significantly different between groups, whereas the adjusted urinary deoxypyridinoline (DPD) was significantly lower for both UT (81.03 +/- 5.53) and IT (88.30 +/- 7.29) compared to Con (128.13 +/- 9.99). Tibial BMD (assessed via DXA) was significantly greater for UT (0.222 +/- 0.005g/cm(2)) and IT (0.219 +/- 0.003g/cm(2)) when compared to Con (0.205 +/- 0.004g/cm(2)). There was no significant difference in DPD or BMD between UT and IT groups. The results indicate that both interrupted and continuous, uninterrupted resistance training programs were equally effective in stimulating bone modeling
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