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Search Results: 1 - 10 of 655343 matches for " J. A. Caballero "
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General study of superscaling in quasielastic $(e,e')$ and $(ν,μ)$ reactions using the relativistic impulse approximation
J. A. Caballero
Physics , 2006, DOI: 10.1103/PhysRevC.74.015502
Abstract: The phenomenon of superscaling for quasielastic lepton induced reactions at energies of a few GeV is investigated within the framework of the relativistic impulse approximation. A global analysis of quasielastic inclusive electron and charged-current neutrino scattering reactions on nuclei is presented. Scaling and superscaling properties are shown to emerge from both types of processes. The crucial role played by final state interactions is evaluated by using different approaches. The asymmetric shape presented by the experimental scaling function, with a long tail in the region of positive values of the scaling variable, is reproduced when the interaction in the final state between the knockout nucleon and the residual nucleus is described within the relativistic mean field approach. The impact of gauge ambiguities and off-shell effects in the scaling function is also analyzed.
Gaia and brown dwarfs from Spain
J. A. Caballero
Physics , 2014,
Abstract: Gaia will not observe 50000 brown dwarfs, but about 100 times less. However, these <~ 500 brown dwarfs will be benchmarks for many substellar topics. It is possible to identify them in advance and make the list public to all astronomers worldwide through a virtual observatory-compliant "Gaia brown dwarf" catalogue. This M-, L- and T-dwarf Archive of Interest for Astrophysics would tabulate precise Gaia astrometry, multiband photometry, high- and low-resolution spectroscopy and homogeneously derived astrophysical parameters. Spanish observatories may play a key role in the catalogue preparation.
Cool dwarfs in wide multiple systems: Paper 2: A distant M8.5V companion to HD 212168 AB
J. A. Caballero,D. Montes
Physics , 2012,
Abstract: DENIS J222644.3-750342 is a nearby, very-low-mass, M8.5 V-type star that has been repeatedly targeted by kinematic and activity studies. Thought to be an isolated star, it is actually a wide common-proper-companion at 265 arcsec from the bright G0 V Hipparcos star HD 212168. The third member in the trio is CD-75 1242, a poorly investigated K dwarf. We confirm the physical binding of the triple system, to which we call Koenigstuhl 5, by compiling common radial velocities and proper-motions and measuring constant angular separations and position angles between components A, B and C over very long time baselines (A-B: 114 yr; A-C: 22 yr). With about 0.095 Msol, the M8.5 V star at 6090 AU to the G0 V primary is one of the least-bound, ultracool dwarfs in multiple systems.
Stellar and substellar mass function of the young open cluster candidates Alessi 5 and beta Monocerotis
S. Boudreault,J. A. Caballero
Physics , 2010,
Abstract: Although the stellar and substellar populations have been studied in various young and old open clusters, additional studies in clusters in the age range from 5 to 100 Myr is crucial (e.g. to give more constrains on initial mass function variation with improved statistics). Among the open cluster candidates from recent studies, two clusters are best suited for photometric survey of very-low mass stars and brown dwarfs, considering their youth and relative proximity: Alessi 5 (t ~ 40 Myr, d ~ 400 pc) and beta Monocerotis (t ~ 9.1 Myr, d ~ 400 pc). For both clusters, we performed an optical and near-infrared photometric survey, and a virtual observatory survey. Our survey is predicted to be sensitive from the massive B main sequence stars down to brown dwarfs of 30 M_Jup. Here, we present and discuss preliminary results, including the mass function obtained for Alessi 5, which is surprisingly very similar to the mass function of the Hyades (t ~ 600 Myr), although they are of very different ages.
Music and Astronomy
J. A. Caballero,S. Gonzalez Sanchez,I. Caballero
Physics , 2008, DOI: 10.1007/978-3-642-11250-8_170
Abstract: What do Brian May (the Queen's lead guitarist), William Herschel and the Jupiter Symphony have in common? And a white dwarf, a piano and Lagartija Nick? At first glance, there is no connection between them, nor between Music and Astronomy. However, there are many revealing examples of musical Astronomy and astronomical Music. This four-page proceeding describes the sonorous poster that we showed during the VIII Scientific Meeting of the Spanish Astronomical Society.
ácaros Oribátidos interesantes del País Vasco. Nuevas citas (Acari, Oribatida)
Caballero, A. I.,Iturrondobeitia, J. C.
Graellsia , 2000,
Abstract: Not available No disponible
Cool dwarfs in wide multiple systems. Paper 4: a common-proper-motion pair of two identical mid-M dwarfs separated by about 10000 AU
F. M. Rica,J. A. Caballero
Physics , 2012,
Abstract: LSPM J0651+1843 and LSPM J0651+1845 are two high-proper-motion stars recently claimed to form a binary system, FMR 83, by Rica (2012). Here we characterize the system in detail, using astrometric and photometric data, and find that the pair consists of two M4+/-1 dwarfs separated by 9500^(+6200)_(-3800) AU. With these results, FMR 83 becomes one of the very few 'ultrafragile' systems (i.e., systems with very low total masses and very wide physical separations), many of which have been identified in this series of papers.
Analysis of Meson Exchange and Isobar Currents in (e,e'p) Reactions from O-16
J. E. Amaro,A. M. Lallena,J. A. Caballero
Physics , 1999, DOI: 10.1103/PhysRevC.60.014602
Abstract: An analysis of the effects of meson exchange and isobar currents in exclusive (e,e'p) processes from O-16 under quasi-free kinematics is presented. A model that has probed its feasibility for inclusive quasi-elastic (e,e') processes is considered. Sensitivity to final state interactions between the outgoing proton and the residual nucleus is discussed by comparing the results obtained with phenomenological optical potentials and a continuum nuclear shell-model calculation. The contribution of the meson-exchange and isobar currents to the response functions is evaluated and compared to previous calculations, which differ notably from our results. These two-body contributions cannot solve the puzzle of the simultaneous description of the different responses experimentally separated. Copyright 1999 by The American Physical Society
Uncorrelated scattering approximation revisited
A. M. Moro,J. A. Caballero,J. Gomez-Camacho
Physics , 2004, DOI: 10.1016/j.nuclphysa.2004.10.030
Abstract: The formalism to describe the scattering of a weakly bound projectile nucleus by a heavy target is investigated, using the Uncorrelated Scattering Approximation. The main assumption involved is to neglect the correlation between the fragments of the projectile in the region where the interaction with the target is important. It is shown that the angular momentum of each fragment with respect to the target is conserved. Moreover, when suitable approximations are assumed, the kinetic energy of each fragment is also shown to be conserved. The S-matrix for the scattering of the composite system can be written as a combination of terms, each one being proportional to the product of the S-matrices of the fragments.
One dimensional scattering of a two body interacting system by an infinite wall
A. M. Moro,J. A. Caballero,J. Gomez-Camacho
Physics , 2010,
Abstract: The one-dimensional scattering of a two body interacting system by an infinite wall is studied in a quantum-mechanical framework. This problem contains some of the dynamical features present in the collision of atomic, molecular and nuclear systems. The scattering problem is solved exactly, for the case of a harmonic interaction between the fragments. The exact result is used to assess the validity of two different approximations to the scattering process. The adiabatic approximation, which considers that the relative co-ordinate is frozen during the scattering process, is found to be inadequate for this problem. The uncorrelated scattering approximation, which neglects the correlation between the fragments, gives results in accordance with the exact calculations when the scattering energy is high compared to the oscillator parameter.
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