39 results on '"E. Camisassa"'
Search Results
2. A positive PSMA PET/CT Predicts more aggressive disease progression in patients with biochemical recurrence after radical prostatectomy
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L. Nocera, G. Gandaglia, N. Fossati, V. Cucchiara, D. Robesti, F. Barletta, S. Scuderi, A. Rizzo, E. Zito, A. Gallina, E. Camisassa, L. Sciacqua, M. Droghetti, G. Sorce, F. Pellegrino, E. Mazzone, A. Stabile, C.A. Bravi, A. Martini, P.I. Karakiewicz, M. Moschini, F. Montorsi, and A. Briganti
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Diseases of the genitourinary system. Urology ,RC870-923 ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,RC254-282 - Published
- 2020
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3. Can multiparametric MRI improve our ability to predict early biochemical recurrence after radical prostatectomy in contemporary patients? Results from a multi-institutional analysis
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G. Gandaglia, G. Ploussard, M. Valerio, A. Mattei, G. Marra, J. Beauval, B. Malavaud, M. Roumiguié, A. Marquis, L. Afferi, M. Moschini, A. Rakauskas, R. Van Den Bergh, F. De Cobelli, C. Fiori, F. Porpiglia, P. Gontero, N. Fossati, F. Barletta, D. Cannoletta, E. Zito, E. Camisassa, F. Montorsi, and A. Briganti
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Diseases of the genitourinary system. Urology ,RC870-923 ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,RC254-282 - Published
- 2020
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4. Prognostic value of high PIRADS score lesions at mp-MRI of the prostate in men with low risk prostate cancer managed with active surveillance: Results from a single institution series
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M. Bandini, L. Nocera, A. Stabile, R. Leni, G. Gandaglia, N. Fossati, N. Suardi, V. Cucchiara, F. Barletta, D. Cannoletta, E. Camisassa, S. Comana, L. Sciacqua, M. Droghetti, G. Rosiello, E. Mazzone, M. Tutolo, C. Bravi, A. Mottrie, M. Moschini, V. Mirone, N. Longo, F. Montorsi, and A. Briganti
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Diseases of the genitourinary system. Urology ,RC870-923 ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,RC254-282 - Published
- 2020
- Full Text
- View/download PDF
5. A positive PSMA PET/CT predicts more aggressive disease progression in patients with biochemical recurrence after radical prostatectomy
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D. Robesti, G. Gandaglia, N. Fossati, V. Cucchiara, L. Nocera, F. Barletta, S. Scuderi, A. Rizzo, E. Zito, A. Gallina, E. Camisassa, L. Sciacqua, D. Santangelo, M. Droghetti, G. Sorce, F. Pellegrino, E. Mazzone, A. Stabile, C.A. Bravi, A. Martini, P.I. Karakiewicz, M. Moschini, F. Montorsi, and A. Briganti
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Diseases of the genitourinary system. Urology ,RC870-923 ,Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,RC254-282 - Published
- 2020
- Full Text
- View/download PDF
6. Assessing the Observability of Deep Meridional Flow Cells in the Solar Interior
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J. R. Fuentes, Bradley W. Hindman, Junwei Zhao, Catherine C. Blume, Maria E. Camisassa, Nicholas A. Featherstone, Thomas Hartlep, Lydia Korre, and Loren I. Matilsky
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Helioseismology ,Solar meridional circulation ,Solar interior ,Hydrodynamical simulations ,Astrophysics ,QB460-466 - Abstract
Meridional circulation regulates the Sun’s interior dynamics and magnetism. While it is well accepted that meridional flows are poleward at the Sun’s surface, helioseismic observations have yet to provide a definitive answer for the depth at which those flows return to the equator, or the number of circulation cells in depth. Here, we explore the observability of multiple circulation cells stacked in radius. Specifically, we examine the seismic signature of several meridional flow profiles by convolving time–distance averaging kernels with mean flows obtained from a suite of 3D hydrodynamic simulations. At mid and high latitudes, we find that weak flow structures in the deep convection zone can be obscured by signals from the much stronger surface flows. This contamination of 1–2 m s ^−1 is caused by extended side lobes in the averaging kernels, which produce a spurious equatorward signal with flow speeds that are 1 order of magnitude stronger than the original flow speeds in the simulations. At low latitudes, the flows in the deep layers of the simulations are stronger (>2 m s ^−1 ) and multiple cells across the convection zone can produce a sufficiently strong signal to survive the convolution process. Now that meridional flows can be measured over two decades of data, the uncertainties arising from convective noise have fallen to a level where they are comparable in magnitude to the systematic biases caused by nonlocal features in the averaging kernels. Hence, these systematic errors are beginning to influence current helioseismic deductions and need broader consideration.
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- 2024
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7. Triggering micronovae through magnetically confined accretion flows in accreting white dwarfs
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S Scaringi, P J Groot, C Knigge, J-P Lasota, D de Martino, Y Cavecchi, D A H Buckley, and M E Camisassa
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- 2022
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8. Solar-like to Antisolar Differential Rotation: A Geometric Interpretation
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Maria E. Camisassa and Nicholas A. Featherstone
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- 2022
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9. Can we reveal the core-chemical composition of ultra-massive white dwarfs through their magnetic fields?
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Maria E Camisassa, Roberto Raddi, Leandro G Althaus, Jordi Isern, Alberto Rebassa-Mansergas, Santiago Torres, Alejandro H Córsico, Lydia Korre, Universitat Politècnica de Catalunya. Departament de Física, Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica, National Aeronautics and Space Administration (US), Consejo Nacional de Ciencia y Tecnología (México), Universidad Nacional de La Plata, Ministerio de Economía y Competitividad (España), Ministerio de Ciencia, Innovación y Universidades (España), Agencia Estatal de Investigación (España), and European Commission
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High Energy Astrophysical Phenomena (astro-ph.HE) ,Stars: magnetic field ,Stars -- interiors ,Stars -- magnetic fields ,FOS: Physical sciences ,White dwarfs ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Estels nans ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,Stars: interiors ,Astrophysics::Solar and Stellar Astrophysics ,Stars--Magnetic fields ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,White dwarf stars ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
Ultra-massive white dwarfs (1.05M⊙≲MWD) are particularly interesting objects that allow us to study extreme astrophysical phenomena such as type Ia supernovae explosions and merger events. Traditionally, ultra-massive white dwarfs are thought to harbour oxygen–neon (ONe) cores. However, recent theoretical studies and new observations suggest that some ultra-massive white dwarfs could harbour carbon–oxygen (CO) cores. Although several studies have attempted to elucidate the core composition of ultra-massive white dwarfs, to date, it has not been possible to distinguish them through their observed properties. Here, we present a new method for revealing the core-chemical composition in ultra-massive white dwarfs that is based on the study of magnetic fields generated by convective mixing induced by the crystallization process. ONe white dwarfs crystallize at higher luminosities than their CO counterparts. Therefore, the study of magnetic ultra-massive white dwarfs in the particular domain where ONe cores have reached the crystallization conditions but CO cores have not, may provide valuable support to their ONe core-chemical composition, since ONe white dwarfs would display signs of magnetic fields and CO would not. We apply our method to eight white dwarfs with magnetic field measurements and we suggest that these stars are candidate ONe white dwarfs., This work was supported by the NASA grants 80NSSC17K0008, 80NSSC20K0193, and 80NSSC21K0455, the postdoctoral fellowship programme Beatriu de Pinós agreement no. 801370, by AGENCIA through the Programa de Modernización Tecnológica BID 1728/OC-AR, by the PIP 112200801-00940 grant from CONICET, by grant G149 from National University of La Plata, by the MINECO grant PID2020-117252GB-I00, by the ESP 2017-82674-R, by grant RYC-2016-20254 funded by MCIN/AEI/10.13039/501100011033 and by ESF Investing in your future.
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- 2022
10. Constraining the solar neighbourhood age–metallicity relation from white dwarf–main sequence binaries
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N. Castro-Rodríguez, M. E. Camisassa, Mark Hollands, Detlev Koester, Tim Cunningham, A. T. Knowles, Roberto Raddi, Pier-Emmanuel Tremblay, Alberto Rebassa-Mansergas, Santiago Torres, Jinwei Ren, Matthew J. Hoskin, Jesus Maldonado, and Boris T. Gänsicke
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Physics ,Proper motion ,010308 nuclear & particles physics ,media_common.quotation_subject ,Metallicity ,Neighbourhood (graph theory) ,food and beverages ,FOS: Physical sciences ,White dwarf ,Astronomy and Astrophysics ,Astrophysics ,Astrophysics - Astrophysics of Galaxies ,01 natural sciences ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Sky ,Astrophysics of Galaxies (astro-ph.GA) ,0103 physical sciences ,Binary star ,10. No inequality ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Main sequence ,Open cluster ,media_common - Abstract
The age-metallicity relation is a fundamental tool for constraining the chemical evolution of the Galactic disc. In this work we analyse the observational properties of this relation using binary stars that have not interacted consisting of a white dwarf - from which we can derive the total age of the system - and a main sequence star - from which we can derive the metallicity as traced by the [Fe/H] abundances. Our sample consists of 46 widely separated, but unresolved spectroscopic binaries identified within the Sloan Digital Sky Survey, and 189 white dwarf plus main sequence common proper motion pairs identified within the second data release of Gaia. This is currently the largest white dwarf sample for which the metallicity of their progenitors have been determined. We find a flat age-metallicity relation displaying a scatter of [Fe/H] abundances of approximately 0.5 dex around the solar metallicity at all ages. This independently confirms the lack of correlation between age and metallicity in the solar neighbourhood that is found in previous studies focused on analysing single main sequence stars and open clusters., Comment: Accepted for publication by MNRAS
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- 2021
11. The evolution of ultra-massive carbon-oxygen white dwarfs
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María E Camisassa, Leandro G Althaus, Detlev Koester, Santiago Torres, Pilar Gil Pons, Alejandro H Córsico, Universitat Politècnica de Catalunya. Departament de Física, Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica, National Aeronautics and Space Administration (US), European Commission, Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina), and Ministerio de Economía y Competitividad (España)
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High Energy Astrophysical Phenomena (astro-ph.HE) ,FOS: Physical sciences ,evolution [Stars] ,White dwarfs ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Stars -- evolution ,Estels nans ,Stars: interior ,Stars: evolution ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Stars -- interior ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,Astrophysics::Solar and Stellar Astrophysics ,Stars--Evolution ,Astrophysics::Earth and Planetary Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena ,interior [Stars] ,White dwarf stars ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Estels--Evolució - Abstract
Ultra-massive white dwarfs ($\rm M_{WD} \gtrsim 1.05\, M_{\odot}$) are considered powerful tools to study type Ia supernovae explosions, merger events, the occurrence of physical processes in the Super Asymptotic Giant Branch (SAGB) phase, and the existence of high magnetic fields. Traditionally, ultra-massive white dwarfs are expected to harbour oxygen-neon (ONe) cores. However, new observations and recent theoretical studies suggest that the progenitors of some ultra-massive white dwarfs can avoid carbon burning, leading to the formation of ultra-massive white dwarfs harbouring carbon-oxygen (CO) cores. Here we present a set of ultra-massive white dwarf evolutionary sequences with CO cores for a wide range of metallicity and masses. We take into account the energy released by latent heat and phase separation during the crystallization process and by $^{22}$Ne sedimentation. Realistic chemical profiles resulting from the full computation of progenitor evolution are considered. We compare our CO ultra-massive white dwarf models with ONe models. We conclude that CO ultra-massive white dwarfs evolve significantly slower than their ONe counterparts mainly for three reasons: their larger thermal content, the effect of crystallization, and the effect of $^{22}$Ne sedimentation. We also provide colors in several photometric bands on the basis of new model atmospheres. These CO ultra-massive white dwarf models, together with the ONe ultra-massive white dwarf models, provide an appropriate theoretical framework to study the ultra-massive white dwarf population in our Galaxy., Comment: 9 pages, 6 figures, Accepted for publication in MNRAS
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- 2022
12. Structure and evolution of ultra-massive white dwarfs in general relativity
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Leandro G. Althaus, María E. Camisassa, Santiago Torres, Tiara Battich, Alejandro H. Córsico, Alberto Rebassa-Mansergas, Roberto Raddi, Agencia Nacional de Promoción Científica y Tecnológica (Argentina), Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina), Universidad Nacional de La Plata, Agencia Estatal de Investigación (España), Ministerio de Ciencia, Innovación y Universidades (España), European Research Council, European Commission, Generalitat de Catalunya, Ministerio de Economía y Competitividad (España), Universitat Politècnica de Catalunya. Departament de Física, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica
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Stars -- interiors ,FOS: Physical sciences ,White dwarfs ,Astronomy and Astrophysics ,General Relativity and Quantum Cosmology (gr-qc) ,Stars -- evolution ,Estels nans ,Stars -- white dwarfs ,General Relativity and Quantum Cosmology ,Physical data and processes -- relativistic processes ,Stars: evolution ,Activitat estelar ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,Stars -- oscillations (including pulsations) ,Stars: interiors ,Stars--Evolution ,Stellar oscillations ,White dwarf stars ,Solar and Stellar Astrophysics (astro-ph.SR) - Abstract
[Context] Ultra-massive white dwarfs (M ABSTRACT 1.05 M) are of utmost importance in view of the role they play in type Ia supernovae explosions, merger events, the existence of high-magnetic-field white dwarfs, and the physical processes in the super asymptotic giant branch phase., [Aims] We aim to present the first set of constant rest-mass ultra-massive oxygen-neon white dwarf cooling tracks with masses of M>1.29Mwhichfullytake into account the effects of general relativity on their structural and evolutionary properties., [Methods] We computed the full evolution sequences of 1.29, 1.31, 1.33, 1.35, and 1.369 Mwhite dwarfs with the La Plata stellar evolution code, LPCODE. For this work, the standard equations of stellar structure and evolution have been modified to include the effects of general relativity. Specifically, the fully general relativistic partial differential equations governing the evolution of a spherically symmetric star are solved in a way so that they resemble the standard Newtonian equations of stellar structure. For comparison purposes, the same sequences have been computed for the Newtonian case., [Results] According to our calculations, the evolutionary properties of the most massive white dwarfs are strongly modified by general relativity effects. In particular, the resulting stellar radius is markedly smaller in the general relativistic case, being up to 25% smaller than predicted by the Newtonian treatment for the more massive ones. We find that oxygen-neon white dwarfs more massive than 1.369 Mbecome gravitationally unstable with respect to general relativity effects. When core chemical distribution due to phase separation on crystallization is considered, such instability occurs at somewhat lower stellar masses, 1.36 M. In addition, cooling times for the most massive white dwarf sequences are about a factor of two smaller than in the Newtonian case at advanced stages of evolution. Finally, a sample of white dwarfs have been identified as ideal candidates to test these general relativistic effects., [Conclusions] We conclude that the general relativity effects should be taken into account for an accurate assessment of the structural and evolutionary properties of the most massive white dwarfs. These new ultra-massive white dwarf models constitute a considerable improvement over those computed in the framework of the standard Newtonian theory of stellar interiors., Part of this work was supported by PICT-2017-0884 from ANPCyT, PIP 112-20080100940 grant from CONICET, grant G149 from University of La Plata, NASA grants 80NSSC17K0008 and 80NSSC20K0193. S.T. and A.R.M. acknowledge support from MINECO under the PID2020-117252GB-I00 grant. A.R.M. acknowledges support from Grant RYC-2016-20254 funded by MCIN/AEI/10.13039/501100011033 and by ESF Investing in your future. R.R. has received funding from the postdoctoral fellowship program Beatriu de Pinós, funded by the Secretary of Universities and Research (Government of Catalonia) and by the Horizon 2020 programme of research and innovation of the European Union under the Maria Skłodowska-Curie grant agreement No. 801370.
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- 2022
13. Kinematic properties of white dwarfs. Galactic orbital parameters and age-velocity dispersion relation
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N. P. Gentile Fusillo, Pier-Emmanuel Tremblay, Tim Cunningham, Detlev Koester, Juanjuan Ren, Jesus Maldonado, Roberto Raddi, M. Dimpel, Alberto Rebassa-Mansergas, Santiago Torres, María E. Camisassa, Ulrich Heber, Universitat Politècnica de Catalunya. Departament de Física, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica
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Proper motion ,Population ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Thick disk ,Astrophysics::Solar and Stellar Astrophysics ,education ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Physics ,education.field_of_study ,Computer Science::Information Retrieval ,White dwarfs ,White dwarf ,Velocity dispersion ,Astronomy and Astrophysics ,Astrometry ,Astrophysics - Astrophysics of Galaxies ,Radial velocity ,Kinematics and dynamics [Galaxy] ,Thin disk ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,Astrophysics of Galaxies (astro-ph.GA) ,Matèria fosca (Astronomia) ,Astrophysics::Earth and Planetary Astrophysics ,White dwarf stars ,General [binaries] - Abstract
We present the first detailed 3D kinematic analysis of a sample of 3133 white dwarfs that use Gaia astrometry plus radial velocities, which were measured either by Gaia or by ground based spectroscopic observations. The sample includes either isolated white dwarfs that have direct radial velocity measurements, or white dwarfs that belong to common proper motion pairs that contain nondegenerate companions with available radial velocities. A subset of common proper motion pairs also have metal abundances that have been measured by large scale spectroscopic surveys or by our own follow-up observations. We used the white dwarfs as astrophysical clocks, by determining their masses and total ages via interpolation with dedicated evolutionary models. We also used the nondegenerate companions in common proper motions to chemically tag of the population. Combining accurate radial velocities with Gaia astrometry and proper motions, we derived the velocity components of our sample in the Galactic rest frame and their Galactic orbital parameters. The sample is mostly located within ~300 pc from the Sun. It contains predominantly (90-95%) thin-disk stars with close-to-circular Galactic orbits, while the remaining 5-10% of stars have more eccentric trajectories and belong to the thick disk. We identified seven isolated white dwarfs and two common proper motion pairs as halo members. We determined the age - velocity dispersion relation for the thin-disk members, which shows signatures of dynamical heating and saturation after 4-6 Gyr. We observed a mild anti-correlation between [Fe/H] and the radial component of the average - velocity dispersion, showing that dynamical mixing of populations takes place in the Galactic disk, as was detected via the analysis of other samples of FGK stars. [Abridged], Accepted for publication (Raddi et al. 2022, A&A, 658, A22). 16 pages, 14 figures, 9 tables. Tables 2, 4, 5, 6, and 7 are available as pdf files and in electronic form via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/658/A22
- Published
- 2021
14. Increased awareness of surgical outcomes improves long-term functional outcomes after robot-assisted radical prostatectomy. A prospective assessment following implementation of prospective data collection
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G.O. Cirulli, G. Rosiello, E. Mazzone, N. Fossati, F. Barletta, S. Scuderi, D. Robesti, G. Gandaglia, L. Toneatto, G. Colandrea, R. Leni, L. D’Ambrosio, A. Pellegrino, L. Quarta, A. Gallina, V. Cucchiara, A. Martini, S. Comana, A. Stabile, E. Camisassa, F. Dehò, F. Montorsi, and A. Briganti
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Urology - Published
- 2022
15. Evolution and asteroseismology of ultra-massive DA white dwarfs
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F. C. De Gerónimo, A. H. Córsico, Leandro Gabriel Althaus, and M. E. Camisassa
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Physics ,010308 nuclear & particles physics ,Space and Planetary Science ,0103 physical sciences ,White dwarf ,Astronomy ,Astronomy and Astrophysics ,010303 astronomy & astrophysics ,01 natural sciences ,Asteroseismology - Abstract
Ultra-massive (⩾M⊙) oxygen/neon (ONe) core white dwarfs (WDs) are the result of the evolution of isolated progenitor stars with masses above 6−M⊙. It is expected that hydrogen-rich (DA) ultra-massive WDs harbor crystallized cores at the typical temperatures of the ZZ Ceti instability strip. These stars offer a unique opportunity to study the processes of crystallization and to infer their core chemical composition. We present a study of the evolution and asteroseismology of ultra-massive DA WDs. We found that all pulsating WDs known to date with M⩾1.1M⊙ should have more than 80% of their mass crystallized, if a ONe-core is assumed. Finally, we present a complete asteroseismological analysis to the well known ZZ Ceti BPM 37093 and a preliminary analysis to GD 518 and SDSS J0840+5222.
- Published
- 2019
16. The Gaia DR2 halo white dwarf population: The luminosity function, mass distribution, and its star formation history
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Santiago Torres, Roberto Raddi, M. E. Camisassa, Alberto Rebassa-Mansergas, and Ministerio de Economía y Competitividad (España)
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Ciencias Astronómicas ,Population ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Stars: luminosity function ,01 natural sciences ,Luminosity ,Galactic halo ,Halo ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,halo [Galaxy] ,stellar content [Galaxy] ,education ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,luminosity function [Stars] ,Luminosity function (astronomy) ,Physics ,education.field_of_study ,Galaxy: stellar content ,010308 nuclear & particles physics ,Star formation ,White dwarf ,White dwarfs ,Astronomy and Astrophysics ,Astrophysics - Astrophysics of Galaxies ,Galaxy ,Galaxy: halo ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Mass function ,Astrophysics::Earth and Planetary Astrophysics - Abstract
We analyze the volume-limited nearly complete 100 pc sample of 95 halo white dwarf candidates identified by the second data release of Gaia. Based on a detailed population synthesis model, we apply a method that relies on Gaia astrometry and photometry to accurately derive the individual white dwarf parameters (mass, radius, effective temperature, bolometric luminosity and age). This method is tested with 25 white dwarfs of our sample for which we took optical spectra and performed spectroscopic analysis. We build and analyse the halo white dwarf luminosity function, for which we find for the first time possible evidences of the cut-off at its faintest end, leading to an age estimate of $\simeq12\pm0.5 $Gyr. The mass distribution of the sample peaks at $0.589\,M_{\odot}$, with $71\%$ of the white dwarf masses below $0.6\,M_{\odot}$ and just two massive white dwarfs of more than $0.8\,M_{\odot}$. From the age distribution we find three white dwarfs with total ages above 12 Gyr, of which J1312-4728 is the oldest white dwarf known with an age of $12.41\pm0.22 $Gyr. We prove that the star formation history is mainly characterised by a burst of star formation that occurred from 10 to 12 Gyr in the past, but extended up to 8 Gyr. We also find that the peak of the star formation history is centered at around 11 Gyr, which is compatible with the current age of the Gaia-Enceladus encounter. Finally, $13\%$ of our halo sample is contaminated by high-speed young objects (total age, 15 pages, 9 figures, 2 tables; accepted for publication in MNRAS
- Published
- 2021
17. Forever young white dwarfs: When stellar ageing stops
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Pier-Emmanuel Tremblay, Sihao Cheng, Santiago Torres, María E. Camisassa, Roberto Raddi, Leandro Gabriel Althaus, Alberto Rebassa-Mansergas, Alejandro H. Córsico, Ministerio de Ciencia, Innovación y Universidades (España), Generalitat de Catalunya, European Commission, Universitat Politècnica de Catalunya. Departament de Física, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica
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Population ,FOS: Physical sciences ,evolution [Stars] ,Astrophysics ,Compact star ,01 natural sciences ,purl.org/becyt/ford/1 [https] ,0103 physical sciences ,010306 general physics ,education ,010303 astronomy & astrophysics ,Stellar evolution ,Solar and Stellar Astrophysics (astro-ph.SR) ,Physics ,education.field_of_study ,End point ,interiors [Stars] ,White dwarf ,White dwarfs ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,Estels ,Stars: evolution ,Supernova ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Space and Planetary Science ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,Stars: interiors ,Energy source ,White dwarf stars - Abstract
White dwarf stars are the most common end point of stellar evolution. Of special interest are the ultramassive white dwarfs, as they are related to type Ia Supernovae explosions, merger events, and Fast Radio Bursts. Ultramassive white dwarfs are expected to harbour oxygen-neon (ONe) cores as a result of single standard stellar evolution. However, a fraction of them could have carbon-oxygen (CO) cores. Recent studies, based on the new observations provided by the {\it Gaia} space mission, indicate that a small fraction of the ultramassive white dwarfs experience a strong delay in their cooling, which cannot be attributed only to the occurrence of crystallization, thus requiring an unknown energy source able to prolong their life for long periods of time. In this study we find that the energy released by $^{22}$Ne sedimentation in the deep interior of ultramassive white dwarfs with CO cores and high $^{22}$Ne content is consistent with the long cooling delay of these stellar remnants. On the basis of a synthesis study of the white dwarf population, based on Monte Carlo techniques, we find that the observations revealed by {\it Gaia} can be explained by the existence of these prolonged youth ultramassive white dwarfs. Although such a high $^{22}$Ne abundance is not consistent with the standard evolutionary channels, our results provide sustain to the existence of CO-core ultramassive white dwarfs and to the occurrence of $^{22}$Ne sedimentation., Comment: 5 pages, 4 figures. Accepted for publication in A&A Letters
- Published
- 2021
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18. Assessing the need for systematic biopsies in addition to targeted biopsies according to the volume of the index lesion diagnosed at mpmri. Results from a large multi-institutional database
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F. Pellegrino, E. Mazzone, A. Stabile, G. Sorce, L. Nocera, S. Scuderi, G. Basile, G. Colandrea, R. Leni, D. Cannoletta, M. De Angelis, A. Pellegrino, L. Sciacqua, S. Comana, E. Camisassa, G. Gandaglia, F. De Cobelli, F. Montorsi, and A. Briganti
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Urology - Published
- 2021
19. A positive PSMA PET/CT predicts more aggressive disease progression in patients with biochemical recurrence after radical prostatectomy
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Andrea Gallina, P.I. Karakiewicz, M. Moschini, Francesco Montorsi, Vito Cucchiara, Luigi Nocera, Alberto Martini, Armando Stabile, A. Rizzo, E. Zito, Francesco Barletta, A. Briganti, C.A. Bravi, Simone Scuderi, Matteo Droghetti, Gabriele Sorce, G. Gandaglia, D. Santangelo, F. Pellegrino, E. Mazzone, N. Fossati, Daniele Robesti, L. Sciacqua, and E. Camisassa
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Biochemical recurrence ,medicine.medical_specialty ,Prostatectomy ,business.industry ,Urology ,medicine.medical_treatment ,Aggressive disease ,lcsh:Diseases of the genitourinary system. Urology ,lcsh:RC870-923 ,lcsh:Neoplasms. Tumors. Oncology. Including cancer and carcinogens ,lcsh:RC254-282 ,medicine ,In patient ,Psma pet ct ,business - Published
- 2020
20. An ultra-massive white dwarf with a mixed hydrogen–carbon atmosphere as a likely merger remnant
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Alejandro H. Córsico, Boris T. Gänsicke, María E. Camisassa, N. P. Gentile-Fusillo, Matthew J. Hoskin, Danny Steeghs, A. Aungwerojwit, Detlev Koester, Tom Marsh, V. S. Dhillon, Paul Chote, Paula Izquierdo, Pier-Emmanuel Tremblay, and Mark Hollands
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Ciencias Astronómicas ,010504 meteorology & atmospheric sciences ,Hydrogen ,FOS: Physical sciences ,chemistry.chemical_element ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,purl.org/becyt/ford/1 [https] ,Atmosphere ,Neon ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Solar and Stellar Astrophysics ,Physics::Atomic Physics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Helium ,Astrophysics::Galaxy Astrophysics ,0105 earth and related environmental sciences ,QB ,Physics ,White dwarf ,White dwarfs ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,Carbon ,Astronomía ,chemistry ,Convection zone ,Astrophysics - Solar and Stellar Astrophysics ,13. Climate action ,Astrophysics::Earth and Planetary Astrophysics ,Mass fraction - Abstract
White dwarfs are dense, cooling stellar embers consisting mostly of carbon and oxygen, or oxygen and neon (with a few percent carbon) at higher initial stellar masses. These stellar cores are enveloped by a shell of helium which in turn is usually surrounded by a layer of hydrogen, generally prohibiting direct observation of the interior composition. However, carbon is observed at the surface of a sizeable fraction of white dwarfs, sometimes with traces of oxygen, and it is thought to be dredged-up from the core by a deep helium convection zone. In these objects only traces of hydrogen are found as large masses of hydrogen are predicted to inhibit hydrogen/helium convective mixing within the envelope. We report the identification of WDJ055134.612+413531.09, an ultra-massive (1.14 solar masses (M⊙)) white dwarf with a unique hydrogen/carbon mixed atmosphere (C/H=0.15 in number ratio). Our analysis of the envelope and interior indicates that the total hydrogen and helium mass fractions must be several orders of magnitude lower than predictions of single star evolution: less than 10−9.5 and 10−7.0, respectively. Due to the fast kinematics (129 ± 5 km s−1 relative to the local standard of rest), large mass, and peculiar envelope composition, we argue that WDJ0551+4135 is consistent with formation from the merger of two white dwarfs in a tight binary system., Instituto de Astrofísica de La Plata
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- 2020
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21. Asteroseismological analysis of the ultra-massive ZZ Ceti stars BPM~37093, GD~518, and SDSS~J0840+5222
- Author
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María E. Camisassa, Alejandro H. Córsico, Leandro Gabriel Althaus, and Francisco C. De Gerónimo
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oscillations [stars] ,Ciencias Astronómicas ,Stellar mass ,FOS: Physical sciences ,chemistry.chemical_element ,Context (language use) ,Astrophysics ,stars: interiors ,stars: evolution – white dwarfs ,evolution – white dwarfs [stars] ,01 natural sciences ,purl.org/becyt/ford/1 [https] ,Neon ,0103 physical sciences ,010306 general physics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,white dwarfs ,Physics ,interiors [stars] ,White dwarf ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,Effective temperature ,Stars ,Amplitude ,Astrophysics - Solar and Stellar Astrophysics ,chemistry ,Space and Planetary Science ,evolution [stars] ,stars: oscillations ,Instability strip - Abstract
Ultra-massive hydrogen-rich (DA) white dwarfs (WD) are expected to have a substantial portion of their cores in a crystalline state at the effective temperatures characterizing the ZZ Ceti instability strip, as a result of Coulomb interactions. Asteroseismological analyses of these WDs can provide valuable information related to the crystallization process, the core chemical composition and the evolutionary origin of these stars. We present a thorough asteroseismological analysis of the ultra-massive ZZ Ceti star BPM~37093, which exhibits a rich period spectrum, on the basis of a complete set of fully evolutionary models that represent ultra-massive oxygen/neon(ONe)-core DA WD stars harbouring a range of hydrogen (H) envelope thicknesses. We also carry out preliminary asteroseismological inferences on two other ultra-massive ZZ Ceti stars that exhibit fewer periods, GD~518, and SDSS~J0840+5222. We found a mean period spacing of $\Delta \Pi \sim 17$ s in the data of BPM~37093, associated to $\ell= 2$ modes. We found asteroseismological models for the three objects under analysis, two of them (BPM~37093 and GD~518) characterized by canonical (thick) H envelopes, and the third one (SDSS~J0840+5222) with a thinner H envelope. We also derive asteroseismological distances which are somewhat different to the astrometric measurements of {\it Gaia} for these stars. Asteroseismological analyses like the one presented in this paper could lead to a more complete knowledge of the processes occurring during crystallization inside WDs. Also, they could make it possible to deduce the core chemical composition of ultra-massive WDs, and in this way, to infer their evolutionary origin, i.e., if the star has a ONe core and then is the result of single-star evolution, or if it harbour a carbon/oxygen (CO) core and is the product of a merger of the two components of a binary system., Comment: 13 pages, 10 figures, 7 tables. To be published in Astronomy and Astrophysics
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- 2019
22. Reducing the risk of postoperative complications after robot-assisted radical prostatectomy in prostate cancer patients: results of a prospective audit and feedback intervention following the implementation of prospective data collection
- Author
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G. Rosiello, G. Gandaglia, N. Fossati, V. Cucchiara, S. Scuderi, F. Barletta, E. Mazzone, C. Andrea Bravi, D. Robesti, D. Cannoletta, L. Sciacqua, S. Comana, E. Camisassa, A. Stabile, A. Gallina, F. Montorsi, and A. Briganti
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Urology - Published
- 2021
23. The detection of a PI-RADS 4-5 lesion at multiparametric MRI before confirmatory biopsy. Is the strongest predictor of disease progression among men with low-risk prostate cancer included in an active surveillance prospective protocol
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L. Nocera, G. Gandaglia, R. Leni, E. Mazzone, C. Bravi, A. Martini, G. Rosiello, S. Scuderi, F. Barletta, D. Cannoletta, G. Cirulli, M. De Angelis, L. Sciacqua, E. Camisassa, A. Stabile, N. Fossati, F. Montorsi, and A. Briganti
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Urology - Published
- 2021
24. Development of a classification system for reporting postoperative complications in prostate cancer patients treated with robot-assisted radical prostatectomy: A comprehensive analysis based on the EAU guidelines recommendations
- Author
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Simone Scuderi, Donato Cannoletta, A. Briganti, Armando Stabile, Elio Mazzone, Giuseppe Rosiello, E. Camisassa, Antony Pellegrino, G. Gandaglia, F. Montorsi, N. Fossati, Carlo Andrea Bravi, Vito Cucchiara, S. Comana, L. Sciacqua, Alberto Martini, Daniele Robesti, and Francesco Barletta
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Prostate cancer ,medicine.medical_specialty ,business.industry ,Prostatectomy ,Guidelines recommendations ,Urology ,medicine.medical_treatment ,General surgery ,Medicine ,business ,medicine.disease - Published
- 2021
25. 68Ga-PSMA PET/CT for Recurrent Prostate Cancer after Radical Prostatectomy: What’s next? Analysis from a single, high volume tertiary referral center
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Elio Mazzone, P.I. Karakiewicz, Daniele Robesti, Vito Cucchiara, Andrea Necchi, Renzo Colombo, A. Briganti, F. Montorsi, N. Fossati, Giuseppe Rosiello, Armando Stabile, G. Gandaglia, Riccardo Leni, Marco Moschini, and E. Camisassa
- Subjects
PET-CT ,medicine.medical_specialty ,business.industry ,Prostatectomy ,Urology ,medicine.medical_treatment ,68ga psma ,Referral center ,Medicine ,Recurrent prostate cancer ,Radiology ,business ,Volume (compression) - Published
- 2021
26. Reducing the risk of postoperative complications after robot-assisted radical prostatectomy in prostate cancer patients: results of a prospective audit and feedback intervention following the implementation of prospective data collection
- Author
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Alberto Martini, Donato Cannoletta, Elio Mazzone, Francesco Barletta, E. Camisassa, L. Sciacqua, Daniele Robesti, Andrea Gallina, Vito Cucchiara, S. Comana, Simone Scuderi, F. Montorsi, Carlo Andrea Bravi, Armando Stabile, A. Briganti, Giuseppe Rosiello, G. Gandaglia, and N. Fossati
- Subjects
medicine.medical_specialty ,Prostate cancer ,Prospective audit ,Prostatectomy ,business.industry ,Urology ,General surgery ,Intervention (counseling) ,medicine.medical_treatment ,medicine ,Prospective data ,medicine.disease ,business - Published
- 2021
27. The effects of $^{22}$Ne sedimentation and metallicity on the local 40 pc white dwarf luminosity function
- Author
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María E. Camisassa, Leandro Gabriel Althaus, Alberto Rebassa-Mansergas, Jordi Tononi, Enrique García-Berro, Santiago Torres, Universitat Politècnica de Catalunya. Departament de Física, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica
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Sedimentation (water treatment) ,Stars--Luminosity function ,Metallicity ,Astrophysics::High Energy Astrophysical Phenomena ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Stars - luminosity function ,purl.org/becyt/ford/1 [https] ,luminosity function [stars] ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Luminosity function (astronomy) ,Physics ,010308 nuclear & particles physics ,White dwarfs ,White dwarf ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,Estels nans ,Astrophysics - Astrophysics of Galaxies ,Astrophysics - Solar and Stellar Astrophysics ,mass function ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,Astrophysics::Earth and Planetary Astrophysics ,White dwarf stars - Abstract
We analyze the effect of the sedimentation of $^{22}$Ne on the local white dwarf luminosity function by studying scenarios under different Galactic metallicity models. We make use of an up-to-date population synthesis code based on Monte Carlo techniques to derive the synthetic luminosity function. Constant solar metallicity models are not able to simultaneously reproduce the peak and cut-off of the white dwarf luminosity function. The extra release of energy due to $^{22}$Ne sedimentation piles up more objects in brighter bins of the faint end of the luminosity function. The contribution of a single burst thick disk population increases the number of stars in the magnitude interval centered around $M_{\rm bol}=15.75$. Among the metallicity models studied, the one following a Twarog's profile is disposable. Our best fit model was obtained when a dispersion in metallicities around the solar metallicity value is considered along with a $^{22}$Ne sedimentation model, a thick disk contribution and an age of the thin disk of $8.8\pm0.2$ Gyr. Our population synthesis model is able to reproduce the local white dwarf luminosity function with a high degree of precision when a dispersion in metallicities around the solar value model is adopted. Although the effects of $^{22}$Ne sedimentation are only marginal and the contribution of a thick disk population is minor, both of them help in better fitting the peak and the cut-off regions of the white dwarf luminosity function., 11 pages, 9 figures and 2 tables; accepted for publication in A&A
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- 2019
28. The evolution of ultra-massive white dwarfs
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María E. Camisassa, M. L. Novarino, Leandro Gabriel Althaus, Francisco C. De Gerónimo, Alejandro H. Córsico, René D. Rohrmann, Enrique García-Berro, F. C. Wachlin, and M. M. Miller Bertolami
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Physics ,interiors [stars] ,010308 nuclear & particles physics ,FOS: Physical sciences ,Astronomy and Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,purl.org/becyt/ford/1.3 [https] ,01 natural sciences ,purl.org/becyt/ford/1 [https] ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,evolution [stars] ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,white dwarfs [stars] ,010303 astronomy & astrophysics ,Humanities ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics - Abstract
Ultra-massive white dwarfs are powerful tools to study various physical processes in the Asymptotic Giant Branch (AGB), type Ia supernova explosions and the theory of crystallization through white dwarf asteroseismology. Despite the interest in these white dwarfs, there are few evolutionary studies in the literature devoted to them. Here, we present new ultra-massive white dwarf evolutionary sequences that constitute an improvement over previous ones. In these new sequences, we take into account for the first time the process of phase separation expected during the crystallization stage of these white dwarfs, by relying on the most up-to-date phase diagram of dense oxygen/neon mixtures. Realistic chemical profiles resulting from the full computation of progenitor evolution during the semidegenerate carbon burning along the super-AGB phase are also considered in our sequences. Outer boundary conditions for our evolving models are provided by detailed non-gray white dwarf model atmospheres for hydrogen and helium composition. We assessed the impact of all these improvements on the evolutionary properties of ultra-massive white dwarfs, providing up-dated evolutionary sequences for these stars. We conclude that crystallization is expected to affect the majority of the massive white dwarfs observed with effective temperatures below $40\,000\, \rm K$. Moreover, the calculation of the phase separation process induced by crystallization is necessary to accurately determine the cooling age and the mass-radius relation of massive white dwarfs. We also provide colors in the GAIA photometric bands for our H-rich white dwarf evolutionary sequences on the basis of new models atmospheres. Finally, these new white dwarf sequences provide a new theoretical frame to perform asteroseismological studies on the recently detected ultra-massive pulsating white dwarfs., 13 pages, 15 figures, 4 tables. Accepted for publication in Astronomy & Astrophysics
- Published
- 2019
29. Gaia DR2 white dwarfs in the Hercules stream
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Hector Canovas, C. Cantero, Thomas Thelemaque, María E. Camisassa, Leandro Gabriel Althaus, Santiago Torres, Alberto Rebassa-Mansergas, Teresa Antoja, Universitat Politècnica de Catalunya. Departament de Física, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica
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KINEMATICS AND DYNAMICS [GALAXY] ,Solar neighborhood ,Astrometria ,Population ,FOS: Physical sciences ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Space (mathematics) ,01 natural sciences ,purl.org/becyt/ford/1 [https] ,0103 physical sciences ,Velocity space ,Astrophysics::Solar and Stellar Astrophysics ,DATA ANALYSIS [METHODS] ,education ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Physics ,education.field_of_study ,010308 nuclear & particles physics ,Galaxy - kinematics and dynamics ,White dwarf ,White dwarfs ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,Astrometry ,Methods - data analysis ,Estels nans ,Astrophysics - Astrophysics of Galaxies ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,Astrophysics of Galaxies (astro-ph.GA) ,Age distribution ,Astrophysics::Earth and Planetary Astrophysics ,White dwarf stars - Abstract
We analyzed the velocity space of the thin and thick-disk Gaia white dwarf population within 100 pc looking for signatures of the Hercules stellar stream. We aimed to identify those objects belonging to the Hercules stream and, by taking advantage of white dwarf stars as reliable cosmochronometers, to derive a first age distribution. We applied a kernel density estimation to the $UV$ velocity space of white dwarfs. For the region where a clear overdensity of stars was found, we created a 5-D space of dynamic variables. We applied a hierarchichal clustering method, HDBSCAN, to this 5-D space, identifying those white dwarfs that share similar kinematic characteristics. Finally, under general assumptions and from their photometric properties, we derived an age estimate for each object. The Hercules stream was firstly revealed as an overdensity in the $UV$ velocity space of the thick-disk white dwarf population. Three substreams were then found: Hercules $a$ and Hercules $b$, formed by thick-disk stars with an age distribution peaked $4\,$Gyr in the past and extended to very old ages; and Hercules $c$, with a ratio of 65:35 thin:thick stars and a more uniform age distribution younger than 10 Gyr., Comment: 5 pages, 3 figures, accepted for publication in A&A Letters
- Published
- 2019
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30. Pulsation properties of ultra-massive DA white dwarf stars with ONe cores
- Author
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María E. Camisassa, Alejandro H. Córsico, Leandro Gabriel Althaus, F. C. Wachlin, and Francisco C. De Gerónimo
- Subjects
EVOLUTION [STARS] ,WHITE DWARFS ,chemistry.chemical_element ,FOS: Physical sciences ,Context (language use) ,Astrophysics ,01 natural sciences ,purl.org/becyt/ford/1 [https] ,Neon ,Phase (matter) ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Diffusion (business) ,010306 general physics ,Adiabatic process ,010303 astronomy & astrophysics ,Astrophysics::Galaxy Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Phase diagram ,Physics ,White dwarf ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,INTERIORS [STARS] ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,chemistry ,Space and Planetary Science ,OSCILLATIONS [STARS] - Abstract
Ultra-massive DA WD stars are expected to harbor ONe cores resulting from the progenitor evolution through the Super-AGB phase. As evolution proceeds during the WD cooling phase, a crystallization process resulting from Coulomb interactions in very dense plasmas is expected to occur, leading to the formation of a highly crystallized core. Pulsating ultra-massive WDs offer a unique opportunity to infer and test the occurrence of crystallization in WD interiors as well as physical processes related with dense plasmas. We aim to assess the adiabatic pulsation properties of ultra-massive DA WD with ONe cores. We studied the pulsation properties of ultra-massive DA WD stars with ONe cores. We employed a new set of ultra-massive WD evolutionary sequences of models with stellar masses in the range 1.10 $\leq M_{star}/M_{sun} \leq$ 1.29 computed by taking into account the complete evolution of the progenitor stars and the WD stage. When crystallization set on in our models, we took into account latent heat release and also the expected changes in the core chemical composition that are due to phase separation according to a phase diagram suitable for O and Ne plasmas. We computed nonradial pulsation g-modes of our sequences of models at the ZZ Ceti phase by taking into account a solid core. We explored the impact of crystallization on their pulsation properties, in particular, the structure of the period spectrum and the distribution of the period spacings. We find that it would be possible, in principle, to discern whether a WD has a nucleus made of CO or a nucleus of ONe by studying the spacing between periods. The features found in the period-spacing diagrams could be used as a seismological tool to discern the core composition of ultra-massive ZZ Ceti stars, something that should be complemented with detailed asteroseismic analysis using the individual observed periods., Comment: 10 pages, 12 figures, 1 table. Accepted for publication in Astronomy \& Astrophysics
- Published
- 2019
31. On the existence of warm H-rich pulsating white dwarfs
- Author
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María E. Camisassa, Leandro Gabriel Althaus, Andrzej S. Baran, M. Vučković, Francisco C. De Gerónimo, Roberto Silvotti, Alejandro H. Córsico, Leila M. Calcaferro, Murat Uzundag, Keaton J. Bell, and Souza Oliveira Kepler
- Subjects
010504 meteorology & atmospheric sciences ,Star (game theory) ,FOS: Physical sciences ,Astrophysics ,01 natural sciences ,Instability ,purl.org/becyt/ford/1 [https] ,Ionization ,Evolucao estelar ,0103 physical sciences ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,0105 earth and related environmental sciences ,Physics ,White dwarfs ,White dwarf ,Order (ring theory) ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,Effective temperature ,Evolution [Stars] ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Anãs brancas ,Pulsacoes estelares ,Space and Planetary Science ,Content (measure theory) ,Oscillations [Stars] - Abstract
The possible existence of warm ($T_{\rm eff}\sim19\,000$ K) pulsating DA white dwarf (WD) stars, hotter than ZZ Ceti stars, was predicted in theoretical studies more than 30 yr ago. However, to date, no pulsating warm DA WD has been discovered. We re-examine the pulsational predictions for such WDs on the basis of new full evolutionary sequences. We analyze all the warm DAs observed by TESS satellite up to Sector 9 in order to search for the possible pulsational signal. We compute WD evolutionary sequences with H content in the range $-14.5 \lesssim \log(M_{\rm H}/M_{\star}) \lesssim -10$, appropriate for the study of warm DA WDs. We use a new full-implicit treatment of time-dependent element diffusion. Non-adiabatic pulsations were computed in the effective temperature range of $30\,000-10\,000$ K, focusing on $\ell= 1$ $g$ modes with periods in the range $50-1500$ s. We find that extended He/H transition zones inhibit the excitation of $g$ modes due to partial ionization of He below the H envelope, and only in the case that the H/He transition is assumed much more abrupt, models do exhibit pulsational instability. In this case, instabilities are found only in WD models with H envelopes in the range of $-14.5 \lesssim \log(M_{\rm H}/M_{\star}) \lesssim -10$ and at effective temperatures higher than those typical of ZZ Ceti stars, in agreement with previous studies. None of the 36 warm DAs observed so far by TESS satellite are found to pulsate. Our study suggests that the non-detection of pulsating warm DAs, if WDs with very thin H envelopes do exist, could be attributed to the presence of a smooth and extended H/He transition zone. This could be considered as an indirect proof that element diffusion indeed operates in the interior of WDs., Comment: 13 pages, 15 figures, 2 tables. Accepted for publication in Astronomy and Astrophysics
- Published
- 2019
- Full Text
- View/download PDF
32. Pulsations powered by hydrogen shell burning in white dwarfs
- Author
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Alejandro H. Córsico, Hiromoto Shibahashi, María E. Camisassa, and Leandro Gabriel Althaus
- Subjects
Ciencias Astronómicas ,Oscillations ,Hydrogen ,oscillations [Stars] ,Astrophysics::High Energy Astrophysical Phenomena ,chemistry.chemical_element ,FOS: Physical sciences ,evolution [Stars] ,Context (language use) ,Astrophysics ,Astrophysics::Cosmology and Extragalactic Astrophysics ,01 natural sciences ,Evolution of stars ,Galactic halo ,0103 physical sciences ,Stars: oscillations ,Astrophysics::Solar and Stellar Astrophysics ,010303 astronomy & astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Physics ,010308 nuclear & particles physics ,interiors [Stars] ,White dwarf ,White dwarfs ,Astronomy and Astrophysics ,Dipole ,Stars ,Stars: evolution ,Interior stars ,chemistry ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Excited state ,Globular cluster ,Stars: interiors ,Astrophysics::Earth and Planetary Astrophysics - Abstract
Context. In the absence of a third dredge-up episode during the asymptotic giant-branch phase, white dwarf models evolved from low-metallicity progenitors have a thick hydrogen envelope, which makes hydrogen shell burning be the most important energy source. Aims. We investigate the pulsational stability of white dwarf models with thick envelopes to see whether nonradial g-mode pulsations are triggered by hydrogen burning, with the aim of placing constraints on hydrogen shell burning in cool white dwarfs and on a third dredge-up during the asymptotic giant-branch evolution of their progenitor stars. Methods. We construct white-dwarf sequences from low-metallicity progenitors by means of full evolutionary calculations that take into account the entire history of progenitor stars, including the thermally pulsing and the post-asymptotic giant-branch phases, and analyze their pulsation stability by solving the linear, nonadiabatic, nonradial pulsation equations for the models in the range of effective temperatures Teff ~ 15 000-8000 K. Results. We demonstrate that, for white dwarf models with masses M★ ≲ 0.71 M⊙ and effective temperatures 8500 ≲ Teff ≲ 11 600 K that evolved from low-metallicity progenitors (Z = 0.0001, 0.0005, and 0.001), the dipole (ℓ = 1) and quadrupole (ℓ = 2) g1-modes are excited mostly as a result of the hydrogen-burning shell through the ϵ-mechanism, in addition to other g-modes driven by either the κ-γ or the convective driving mechanism. However, the ϵ mechanism is insufficient to drive these modes in white dwarfs evolved from solar-metallicity progenitors. Conclusions. We suggest that efforts should be made to observe the dipole g1-mode in white dwarfs associated with low-metallicity environments, such as globular clusters and/or the galactic halo, to place constraints on hydrogen shell burning in cool white dwarfs and the third dredge-up episode during the preceding asymptotic giant-branch phase., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata
- Published
- 2016
33. The effect of 22Ne diffusion in the evolution and pulsational properties of white dwarfs with solar metallicity progenitors
- Author
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Alejandro H. Córsico, M. M. Miller Bertolami, Aldo Serenelli, Jordi Isern, María E. Camisassa, Leandro Gabriel Althaus, Núria Vinyoles, Enrique García–Berro, Universitat Politècnica de Catalunya. Departament de Física, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica
- Subjects
Ciencias Astronómicas ,Nuclear Theory ,Ciencias Físicas ,Astrophysics ,stars: interiors ,Evolution of stars ,01 natural sciences ,Diffusion ,purl.org/becyt/ford/1 [https] ,Asymptotic giant branch ,Astrophysics::Solar and Stellar Astrophysics ,stars: evolution ,Diffusion (business) ,010303 astronomy & astrophysics ,white dwarfs ,Physics ,diffusion ,Asteroseismology ,Estels nans ,Astrophysics - Solar and Stellar Astrophysics ,Astrophysics::Earth and Planetary Astrophysics ,White dwarf stars ,Dense matter ,CIENCIAS NATURALES Y EXACTAS ,dense matter ,Metallicity ,FOS: Physical sciences ,chemistry.chemical_element ,Astrophysics::Cosmology and Extragalactic Astrophysics ,asteroseismology ,Nuclear Theory (nucl-th) ,0103 physical sciences ,010306 general physics ,Condensed Matter - Statistical Mechanics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Helium ,Astrophysics::Galaxy Astrophysics ,interiors [stars] ,Statistical Mechanics (cond-mat.stat-mech) ,White dwarfs ,White dwarf ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,Astrophysics - Astrophysics of Galaxies ,Astronomía ,Interior stars ,Stars ,chemistry ,Space and Planetary Science ,evolution [stars] ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,Astrophysics of Galaxies (astro-ph.GA) - Abstract
Because of the large neutron excess of 22Ne, sedimentation of this isotope occurs rapidly in the interior of white dwarfs. This process releases an additional amount of energy, thus delaying the cooling times of the white dwarf. This influences the ages of different stellar populations derived using white dwarf cosmochronology. Furthermore, the overabundance of 22Ne in the inner regions of the star modifies the Brunt-Väisälä frequency, thus altering the pulsational properties of these stars. In this work we discuss the impact of 22Ne sedimentation in white dwarfs resulting from solar metallicity progenitors (Z = 0.02). We performed evolutionary calculations of white dwarfs with masses of 0.528, 0.576, 0.657, and 0.833 derived from full evolutionary computations of their progenitor stars, starting at the zero-Age main sequence all the way through the central hydrogen and helium burning, the thermally pulsing asymptotic giant branch (AGB), and post-AGB phases. Our computations show that at low luminosities (), 22Ne sedimentation delays the cooling of white dwarfs with solar metallicity progenitors by about 1 Gyr. Additionally, we studied the consequences of 22Ne sedimentation on the pulsational properties of ZZ Ceti white dwarfs. We find that 22Ne sedimentation induces differences in the periods of these stars larger than the present observational uncertainties, particularly in more massive white dwarfs., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata
- Published
- 2016
34. The white dwarf population of NGC 6397
- Author
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María E. Camisassa, Leandro Gabriel Althaus, Santiago Torres, Enrique García-Berro, Universitat Politècnica de Catalunya. Departament de Física, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica
- Subjects
Ciencias Astronómicas ,Ciencias Físicas ,Monte Carlo method ,Globular clusters: general ,Astrophysics ,Stellar evolution ,purl.org/becyt/ford/1 [https] ,Galaxies--Formation ,Astrophysics::Solar and Stellar Astrophysics ,Omega Centauri ,MAIN-SEQUENCE ,Physics ,education.field_of_study ,luminosity function mass function [Stars] ,White dwarf ,Estels nans ,Astrophysics - Solar and Stellar Astrophysics ,Globular clusters: individual: NGC 6397 ,Mass function ,general [Globular clusters] ,CIENCIAS NATURALES Y EXACTAS ,NGC 6397 ,Population ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,GLOBULAR-CLUSTER NGC-6397 ,luminosity function [stars] ,OMEGA-CENTAURI ,COOLING SEQUENCE ,DEEP ADVANCED CAMERA ,education ,FINAL MASS RELATIONSHIP ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,Luminosity function (astronomy) ,individual: NGC 6397 [Globular clusters] ,Luminosity function ,White dwarfs ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,Stars: luminosity function mass function ,Astrophysics - Astrophysics of Galaxies ,White dwarfs stars ,Astronomía ,Space and Planetary Science ,Astrophysics of Galaxies (astro-ph.GA) ,COLOR-MAGNITUDE DIAGRAM ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,MONTE-CARLO SIMULATIONS - Abstract
Context. NGC 6397 is one of the most interesting, well-observed, and most thoroughly theoretically studied globular clusters. The existing wealth of observations allows us to study the reliability of the theoretical white dwarf cooling sequences of low-metallicity progenitors, to determine the age of NGC 6397 and the percentage of unresolved binaries. We also assess other important characteristics of the cluster, such as the slope of the initial mass function or the fraction of white dwarfs with hydrogen-deficient atmospheres. Aims. We present a population synthesis study of the white dwarf population of NGC 6397. In particular, we study the shape of the color-magnitude diagram and the corresponding magnitude and color distributions. Methods. To do this, we used an advanced Monte Carlo code that incorporates the most recent and reliable cooling sequences and an accurate modeling of the observational biases. Results. Our theoretical models and the observed data agree well. In particular, we find that this agreement is best for those cooling sequences that take into account residual hydrogen burning. This result has important consequences for the evolution of progenitor stars during the thermally pulsing asymptotic giant branch phase, since it implies that appreciable third dredge-up in low-mass, low-metallicity progenitors is not expected to occur. Using a standard burst duration of 1.0 Gyr, we obtain that the age of the cluster is 12.8+0.50-0.75 Gyr. Greater ages are also compatible with the observed data, but then unrealistic longer durations of the initial burst of star formation are needed to fit the luminosity function. Conclusions. We conclude that a correct modeling of the white dwarf population of globular clusters, used in combination with the number counts of main-sequence stars, provides a unique tool for modeling the properties of globular clusters., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata
- Published
- 2015
35. White dwarf evolutionary sequences for low-metallicity progenitors: The impact of third dredge-up
- Author
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M. M. Miller Bertolami, María E. Camisassa, Leandro Gabriel Althaus, Alejandro H. Córsico, Enrique García-Berro, Universitat Politècnica de Catalunya. Departament de Física Aplicada, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica
- Subjects
Ciencias Astronómicas ,ZZ-CETI STARS ,PULSATIONAL PROPERTIES ,Ciencias Físicas ,OPACITIES ,Astrophysics::High Energy Astrophysical Phenomena ,Metallicity ,MODELS ,COOLING SEQUENCES ,FOS: Physical sciences ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,MASS ,Dredge-up ,purl.org/becyt/ford/1 [https] ,AGE ,Starts -- Evolution ,Astrophysics::Solar and Stellar Astrophysics ,Solar and Stellar Astrophysics (astro-ph.SR) ,Astrophysics::Galaxy Astrophysics ,white dwarfs ,Luminosity function (astronomy) ,interiors [stars] ,Physics ,GLOBULAR-CLUSTER ,White dwarfs ,White dwarf ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,HYDROGEN ,Estels nans ,Planetary nebula ,ASTEROSEISMOLOGY ,Astronomía ,Stars: evolution ,Stars ,Astrophysics - Solar and Stellar Astrophysics ,Space and Planetary Science ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,evolution [stars] ,Globular cluster ,Stars: interiors ,Astrophysics::Earth and Planetary Astrophysics ,Energy source ,White dwarf stars ,CIENCIAS NATURALES Y EXACTAS - Abstract
Context. White dwarfs are nowadays routinely used as reliable cosmochronometers, allowing several stellar populations to be dated. Aims. We present new white dwarf evolutionary sequences for low-metallicity progenitors. This is motivated by the recent finding that residual H burning in low-mass white dwarfs resulting from Z = 0.0001 progenitors is the main energy source over a significant part of their evolution. Methods. White dwarf sequences have been derived from full evolutionary calculations that take the entire history of progenitor stars into account, including the thermally pulsing and the post-asymptotic giant branch (AGB) phases. Results. We show that for progenitor metallicities in the range 0.00003 ≲ Z ≲ 0.001, and in the absence of carbon enrichment from the occurrence of a third dredge-up episode, the resulting H envelope of the low-mass white dwarfs is thick enough to make stable H burning the most important energy source even at low luminosities. This has a significant impact on white dwarf cooling times. This result is independent of the adopted mass-loss rate during the thermally-pulsing and post-AGB phases and in the planetary nebulae stage. Conclusions. We conclude that in the absence of third dredge-up episodes, a significant part of the evolution of low-mass white dwarfs resulting from low-metallicity progenitors is dominated by stable H burning. Our study opens the possibility of using the observed white dwarf luminosity function of low-metallicity globular clusters to constrain the efficiency of third dredge up episodes during the thermally-pulsing AGB phase of low-metallicity progenitors., Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata
- Published
- 2015
36. Updated evolutionary sequences for hydrogen-deficient white dwarfs
- Author
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Enrique García-Berro, F. C. Wachlin, Alejandro H. Córsico, René D. Rohrmann, Santiago Torres, María E. Camisassa, Leandro Gabriel Althaus, Universitat Politècnica de Catalunya. Departament de Física, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica
- Subjects
Ciencias Astronómicas ,Hydrogen ,Ciencias Físicas ,chemistry.chemical_element ,Astrophysics ,01 natural sciences ,purl.org/becyt/ford/1 [https] ,0103 physical sciences ,Astrophysics::Solar and Stellar Astrophysics ,Boundary value problem ,010306 general physics ,010303 astronomy & astrophysics ,Helium ,white dwarfs ,Physics ,interiors [stars] ,White dwarf ,Astronomy and Astrophysics ,purl.org/becyt/ford/1.3 [https] ,Estels nans ,Stars ,Estels ,Stars: white dwarfs ,Astronomía ,Stars: evolution ,chemistry ,Space and Planetary Science ,Homogeneous ,Física::Astronomia i astrofísica [Àrees temàtiques de la UPC] ,evolution [stars] ,Stars: interiors ,Astrophysics::Earth and Planetary Astrophysics ,Energy source ,CIENCIAS NATURALES Y EXACTAS - Abstract
We present a set of full evolutionary sequences for white dwarfs with hydrogen-deficient atmospheres. We take into account the evolutionary history of the progenitor stars, all the relevant energy sources involved in the cooling, element diffusion in the very outer layers, and outer boundary conditions provided by new and detailed non-gray white dwarf model atmospheres for pure helium composition. These model atmospheres are based on the most up-to-date physical inputs. Our calculations extend down to very low effective temperatures, of ∼2500 K, provide a homogeneous set of evolutionary cooling tracks that are appropriate for mass and age determinations of old hydrogen-deficient white dwarfs, and represent a clear improvement over previous efforts, which were computed using gray atmospheres., Instituto de Astrofísica de La Plata
37. Updated Evolutionary Sequences for Hydrogen-deficient White Dwarfs.
- Author
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María E. Camisassa, Leandro G. Althaus, René D. Rohrmann, Enrique García-Berro, Santiago Torres, Alejandro H. Córsico, and Felipe C. Wachlin
- Subjects
- *
WHITE dwarf stars , *HYDROGEN spectra , *BOUNDARY value problems , *HELIUM spectra , *STELLAR atmospheres - Abstract
We present a set of full evolutionary sequences for white dwarfs with hydrogen-deficient atmospheres. We take into account the evolutionary history of the progenitor stars, all the relevant energy sources involved in the cooling, element diffusion in the very outer layers, and outer boundary conditions provided by new and detailed non-gray white dwarf model atmospheres for pure helium composition. These model atmospheres are based on the most up-to-date physical inputs. Our calculations extend down to very low effective temperatures, of ∼2500 K, provide a homogeneous set of evolutionary cooling tracks that are appropriate for mass and age determinations of old hydrogen-deficient white dwarfs, and represent a clear improvement over previous efforts, which were computed using gray atmospheres. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
38. THE EFFECT OF 22Ne DIFFUSION IN THE EVOLUTION AND PULSATIONAL PROPERTIES OF WHITE DWARFS WITH SOLAR METALLICITY PROGENITORS.
- Author
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María E. Camisassa, Leandro G. Althaus, Alejandro H. Córsico, Núria Vinyoles, Aldo M. Serenelli, Jordi Isern, Marcelo M. Miller Bertolami, and Enrique García–Berro
- Subjects
- *
SEMICONDUCTOR doping , *PROPERTIES of matter , *MOLECULAR vibration , *SOLID solutions , *PACKED towers (Chemical engineering) - Abstract
Because of the large neutron excess of 22Ne, sedimentation of this isotope occurs rapidly in the interior of white dwarfs. This process releases an additional amount of energy, thus delaying the cooling times of the white dwarf. This influences the ages of different stellar populations derived using white dwarf cosmochronology. Furthermore, the overabundance of 22Ne in the inner regions of the star modifies the Brunt–Väisälä frequency, thus altering the pulsational properties of these stars. In this work we discuss the impact of 22Ne sedimentation in white dwarfs resulting from solar metallicity progenitors (Z = 0.02). We performed evolutionary calculations of white dwarfs with masses of 0.528, 0.576, 0.657, and 0.833 derived from full evolutionary computations of their progenitor stars, starting at the zero-age main sequence all the way through the central hydrogen and helium burning, the thermally pulsing asymptotic giant branch (AGB), and post-AGB phases. Our computations show that at low luminosities (), 22Ne sedimentation delays the cooling of white dwarfs with solar metallicity progenitors by about 1 Gyr. Additionally, we studied the consequences of 22Ne sedimentation on the pulsational properties of ZZ Ceti white dwarfs. We find that 22Ne sedimentation induces differences in the periods of these stars larger than the present observational uncertainties, particularly in more massive white dwarfs. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
39. Green Solid Lipid Nanoparticles by Fatty Acid Coacervation: An Innovative Nasal Delivery Tool for Drugs Targeting Cerebrovascular and Neurological Diseases.
- Author
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Bozza A, Bordano V, Marengo A, Muntoni E, Marini E, Lazzarato L, Dianzani C, Monge C, Rosa AC, Cangemi L, Valsania MC, Colitti B, Camisassa E, and Battaglia L
- Abstract
Cerebrovascular and neurological diseases are characterized by neuroinflammation, which alters the neurovascular unit, whose interaction with the choroid plexus is critical for maintaining brain homeostasis and producing cerebrospinal fluid. Dysfunctions in such process can lead to conditions such as idiopathic normal pressure hydrocephalus, a common disease in older adults. Potential pharmacological treatments, based upon intranasal administration, are worthy of investigation because they might improve symptoms and avoid surgery by overcoming the blood-brain barrier and avoiding hepatic metabolism. Nasal lipid nanocarriers, such as solid lipid nanoparticles, may increase the nasal retention and permeation of drugs. To this aim, green solid lipid nanoparticles, obtained by coacervation from natural soaps, are promising vehicles due to their specific lipid matrix composition and the unsaponifiable fraction, endowed with antioxidant and anti-inflammatory properties, and thus suitable for restoring the neurovascular unit function. In this experimental work, such green solid lipid nanoparticles, fully characterized from a physico-chemical standpoint, were loaded with a drug combination suitable for reverting hydrocephalus symptoms, allowing us to obtain a non-toxic formulation, a reduction in the production of the cerebrospinal fluid in vitro, and a vasoprotective effect on an isolated vessel model. The pharmacokinetics and biodistribution of fluorescently labelled nanoparticles were also tested in animal models.
- Published
- 2024
- Full Text
- View/download PDF
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