Instituto de Astrofísica de La Plata (IALP)http://sedici.unlp.edu.ar:80/handle/10915/867972021-04-11T02:22:51Z2021-04-11T02:22:51ZFormation of solar system analogues: I. Looking for initial conditions through a population synthesis analysisRonco, María PaulaGuilera, Octavio MiguelElía, Gonzalo Carlos dehttp://sedici.unlp.edu.ar:80/handle/10915/1058272020-10-01T04:05:57Z2017-01-01T00:00:00ZArticulo
Monthly Notices of the Royal Astronomical Society; vol. 471, no. 3
Population synthesis models of planetary systems developed during the last ∼15 yr could reproduce several of the observables of the exoplanet population, and also allowed us to constrain planetary formation models.We present our planet formation model, which calculates the evolution of a planetary system during the gaseous phase. The code incorporates relevant physical phenomena for the formation of a planetary system, like photoevaporation, planet migration, gas accretion, water delivery in embryos and planetesimals, a detailed study of the orbital evolution of the planetesimal population, and the treatment of the fusion between embryos, considering their atmospheres. The main goal of this work, unlike other works of planetary population synthesis, is to find suitable scenarios and physical parameters of the disc to form Solar system analogues.We are specially interested in the final planet distributions, and in the final surface density, eccentricity and inclination profiles for the planetesimal population. These final distributions will be used as initial conditions for N-body simulations to study the post-oligarchic formation in a second work. We then consider different formation scenarios, with different planetesimal sizes and different type I migration rates. We find that Solar system analogues are favoured in massive discs, with low type I migration rates, and small planetesimal sizes. Besides, those rocky planets within their habitables zones are dry when discs dissipate. At last, the final configurations of Solar system analogues include information about the mass and semimajor axis of the planets, water contents, and the properties of the planetesimal remnants.
2017-01-01T00:00:00ZPopulation synthesis models of planetary systems developed during the last ∼15 yr could reproduce several of the observables of the exoplanet population, and also allowed us to constrain planetary formation models.We present our planet formation model, which calculates the evolution of a planetary system during the gaseous phase. The code incorporates relevant physical phenomena for the formation of a planetary system, like photoevaporation, planet migration, gas accretion, water delivery in embryos and planetesimals, a detailed study of the orbital evolution of the planetesimal population, and the treatment of the fusion between embryos, considering their atmospheres. The main goal of this work, unlike other works of planetary population synthesis, is to find suitable scenarios and physical parameters of the disc to form Solar system analogues.We are specially interested in the final planet distributions, and in the final surface density, eccentricity and inclination profiles for the planetesimal population. These final distributions will be used as initial conditions for N-body simulations to study the post-oligarchic formation in a second work. We then consider different formation scenarios, with different planetesimal sizes and different type I migration rates. We find that Solar system analogues are favoured in massive discs, with low type I migration rates, and small planetesimal sizes. Besides, those rocky planets within their habitables zones are dry when discs dissipate. At last, the final configurations of Solar system analogues include information about the mass and semimajor axis of the planets, water contents, and the properties of the planetesimal remnants.Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: II. Nonadiabatic analysisCórsico, Alejandro HugoAlthaus, Leandro Gabrielhttp://sedici.unlp.edu.ar:80/handle/10915/1053042020-09-25T04:05:21Z2016-01-01T00:00:00ZArticulo
Astronomy and Astrophysics; vol. 585
Context. Low-mass (M⁎/M⊙ <∼ 0.45) white dwarfs, including the so-called extremely low-mass white dwarfs (ELM, M⁎/M⊙ ≲ 0.18−0.20), are being currently discovered in the field of our Galaxy through dedicated photometric surveys. That some of them pulsate raises the unparalleled chance to investigate their interiors.
Aims. We present a detailed nonadiabatic pulsational analysis of such stars, employing full evolutionary sequences of low-mass He-core white dwarf models derived from binary star evolution computations. The main aim of this study is to provide a detailed description of the pulsation stability properties of variable low-mass white dwarfs during the terminal cooling branch.
Methods. Our nonadiabatic pulsation analysis is based on a new set of He-core white-dwarf models with masses ranging from 0.1554 to 0.4352 M⊙, which were derived by computing the nonconservative evolution of a binary system consisting of an initially 1 M⊙ ZAMS star and a 1.4 M⊙ neutron star. We computed nonadiabatic radial (ℓ = 0) and nonradial (ℓ = 1, 2) g and p modes to assess the dependence of the pulsational stability properties of these objects with stellar parameters such as the stellar mass, the effective temperature, and the convective efficiency.
Results. We found that a dense spectrum of unstable radial modes and nonradial g and p modes are driven by the κ−γ mechanism due to the partial ionization of H in the stellar envelope, in addition to low-order unstable g modes characterized by short pulsation periods that are significantly excited by H burning via the ε mechanism of mode driving. In all the cases, the characteristic times required for the modes to reach amplitudes large enough to be observable (the e-folding times) are always shorter than cooling timescales. We explore the dependence of the ranges of unstable mode periods (the longest and shortest excited periods) with the effective temperature, the stellar mass, the convective efficiency, and the harmonic degree of the modes. We also compare our theoretical predictions with the excited modes observed in the seven known variable low-mass white dwarfs (ELMVs) and found excellent agreement.
2016-01-01T00:00:00ZContext. Low-mass (M⁎/M⊙ <∼ 0.45) white dwarfs, including the so-called extremely low-mass white dwarfs (ELM, M⁎/M⊙ ≲ 0.18−0.20), are being currently discovered in the field of our Galaxy through dedicated photometric surveys. That some of them pulsate raises the unparalleled chance to investigate their interiors.
Aims. We present a detailed nonadiabatic pulsational analysis of such stars, employing full evolutionary sequences of low-mass He-core white dwarf models derived from binary star evolution computations. The main aim of this study is to provide a detailed description of the pulsation stability properties of variable low-mass white dwarfs during the terminal cooling branch.
Methods. Our nonadiabatic pulsation analysis is based on a new set of He-core white-dwarf models with masses ranging from 0.1554 to 0.4352 M⊙, which were derived by computing the nonconservative evolution of a binary system consisting of an initially 1 M⊙ ZAMS star and a 1.4 M⊙ neutron star. We computed nonadiabatic radial (ℓ = 0) and nonradial (ℓ = 1, 2) g and p modes to assess the dependence of the pulsational stability properties of these objects with stellar parameters such as the stellar mass, the effective temperature, and the convective efficiency.
Results. We found that a dense spectrum of unstable radial modes and nonradial g and p modes are driven by the κ−γ mechanism due to the partial ionization of H in the stellar envelope, in addition to low-order unstable g modes characterized by short pulsation periods that are significantly excited by H burning via the ε mechanism of mode driving. In all the cases, the characteristic times required for the modes to reach amplitudes large enough to be observable (the e-folding times) are always shorter than cooling timescales. We explore the dependence of the ranges of unstable mode periods (the longest and shortest excited periods) with the effective temperature, the stellar mass, the convective efficiency, and the harmonic degree of the modes. We also compare our theoretical predictions with the excited modes observed in the seven known variable low-mass white dwarfs (ELMVs) and found excellent agreement.A revisit to the regions of some van den Bergh open clusters using photometric and astrometric parametersOrellana, Rosa BeatrizDe Biasi, María SilvinaPaíz, Leonardo GastónBustos Fierro, I. H.Calderón, J. H.http://sedici.unlp.edu.ar:80/handle/10915/1049022020-09-18T04:04:51Z2015-01-01T00:00:00ZArticulo
New Astronomy; vol. 36
We present results of a study that combines photometry and astrometry for the open clusters vdB80, vdB85 and vdB130. We apply a model which analyses the proper motion distribution and the stellar density to find the kinematic parameters and stellar membership in the region of the mentioned open clusters. The astrometric data are obtained from UCAC4 catalogue. For each cluster, we report the centre coordinates, the components of mean proper motion, the angular diameter and the astrometric members. They are: <math><mrow is="true"><mi is="true">α</mi><mo is="true">=</mo><mn is="true">97</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">73938</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">00846</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><mi is="true">δ</mi><mo is="true">=</mo><mo is="true">-</mo><mn is="true">9</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">66953</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">01177</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">α</mi></mrow></msub><mi mathvariant="italic" is="true">cos</mi><mi is="true">δ</mi><mo is="true">=</mo><mo is="true">-</mo><mn is="true">2.13</mn><mo is="true">±</mo><mn is="true">0.47</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">δ</mi></mrow></msub><mo is="true">=</mo><mo is="true">-</mo><mn is="true">0.95</mn><mo is="true">±</mo><mn is="true">0.47</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><msup is="true"><mrow is="true"><mn is="true">12</mn></mrow><mrow is="true"><mo is="true">′</mo></mrow></msup></mrow></math> , 15 members; vdB85: <math><mrow is="true"><mi is="true">α</mi><mo is="true">=</mo><mn is="true">101</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">71670</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">00808</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><mi is="true">δ</mi><mo is="true">=</mo><mn is="true">1</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">34392</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">01253</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">α</mi></mrow></msub><mi mathvariant="italic" is="true">cos</mi><mi is="true">δ</mi><mo is="true">=</mo><mn is="true">0.89</mn><mo is="true">±</mo><mn is="true">0.43</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">δ</mi></mrow></msub><mo is="true">=</mo><mn is="true">3.24</mn><mo is="true">±</mo><mn is="true">0.43</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msup is="true"><mrow is="true"><mn is="true">8</mn></mrow><mrow is="true"><mo is="true">′</mo></mrow></msup></mrow></math> members; vdB130: <math><mrow is="true"><mi is="true">α</mi><mo is="true">=</mo><mn is="true">304</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">44001</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">01407</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><mi is="true">δ</mi><mo is="true">=</mo><mn is="true">39</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">32745</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">00726</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">α</mi></mrow></msub><mi mathvariant="italic" is="true">cos</mi><mi is="true">δ</mi><mo is="true">=</mo><mo is="true">-</mo><mn is="true">4.14</mn><mo is="true">±</mo><mn is="true">0.25</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">δ</mi></mrow></msub><mo is="true">=</mo><mo is="true">-</mo><mn is="true">5.15</mn><mo is="true">±</mo><mn is="true">0.25</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msup is="true"><mrow is="true"><mn is="true">9</mn></mrow><mrow is="true"><mo is="true">′</mo></mrow></msup></mrow></math> 9 members. We analyse the incidence of the proper motion errors in the determination of the cluster parameters and of the stellar membership and find that they are not significantly changed. We finally compare the astrometric members with the photometric ones given in the literature.
2015-01-01T00:00:00ZWe present results of a study that combines photometry and astrometry for the open clusters vdB80, vdB85 and vdB130. We apply a model which analyses the proper motion distribution and the stellar density to find the kinematic parameters and stellar membership in the region of the mentioned open clusters. The astrometric data are obtained from UCAC4 catalogue. For each cluster, we report the centre coordinates, the components of mean proper motion, the angular diameter and the astrometric members. They are: <math><mrow is="true"><mi is="true">α</mi><mo is="true">=</mo><mn is="true">97</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">73938</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">00846</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><mi is="true">δ</mi><mo is="true">=</mo><mo is="true">-</mo><mn is="true">9</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">66953</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">01177</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">α</mi></mrow></msub><mi mathvariant="italic" is="true">cos</mi><mi is="true">δ</mi><mo is="true">=</mo><mo is="true">-</mo><mn is="true">2.13</mn><mo is="true">±</mo><mn is="true">0.47</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">δ</mi></mrow></msub><mo is="true">=</mo><mo is="true">-</mo><mn is="true">0.95</mn><mo is="true">±</mo><mn is="true">0.47</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><msup is="true"><mrow is="true"><mn is="true">12</mn></mrow><mrow is="true"><mo is="true">′</mo></mrow></msup></mrow></math> , 15 members; vdB85: <math><mrow is="true"><mi is="true">α</mi><mo is="true">=</mo><mn is="true">101</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">71670</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">00808</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><mi is="true">δ</mi><mo is="true">=</mo><mn is="true">1</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">34392</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">01253</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">α</mi></mrow></msub><mi mathvariant="italic" is="true">cos</mi><mi is="true">δ</mi><mo is="true">=</mo><mn is="true">0.89</mn><mo is="true">±</mo><mn is="true">0.43</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">δ</mi></mrow></msub><mo is="true">=</mo><mn is="true">3.24</mn><mo is="true">±</mo><mn is="true">0.43</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msup is="true"><mrow is="true"><mn is="true">8</mn></mrow><mrow is="true"><mo is="true">′</mo></mrow></msup></mrow></math> members; vdB130: <math><mrow is="true"><mi is="true">α</mi><mo is="true">=</mo><mn is="true">304</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">44001</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">01407</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><mi is="true">δ</mi><mo is="true">=</mo><mn is="true">39</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">32745</mn><mo is="true">±</mo><mn is="true">0</mn><mi is="true">°</mi><mo is="true">.</mo><mn is="true">00726</mn><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">α</mi></mrow></msub><mi mathvariant="italic" is="true">cos</mi><mi is="true">δ</mi><mo is="true">=</mo><mo is="true">-</mo><mn is="true">4.14</mn><mo is="true">±</mo><mn is="true">0.25</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msub is="true"><mrow is="true"><mi is="true">μ</mi></mrow><mrow is="true"><mi is="true">δ</mi></mrow></msub><mo is="true">=</mo><mo is="true">-</mo><mn is="true">5.15</mn><mo is="true">±</mo><mn is="true">0.25</mn><mspace width="0.25em" is="true"></mspace><mi mathvariant="normal" is="true">mas</mi><mo is="true">/</mo><mi mathvariant="normal" is="true">yr</mi><mtext is="true">,</mtext><mspace width="0.35em" is="true"></mspace><msup is="true"><mrow is="true"><mn is="true">9</mn></mrow><mrow is="true"><mo is="true">′</mo></mrow></msup></mrow></math> 9 members. We analyse the incidence of the proper motion errors in the determination of the cluster parameters and of the stellar membership and find that they are not significantly changed. We finally compare the astrometric members with the photometric ones given in the literature.Resolving the clumpy circumstellar environment of the B[e] supergiant LHA 120-S 35Torres, Andrea FabianaCidale, Lydia SoniaKraus, M.Arias, María LauraBarbá, Rodolfo HéctorMaravelias, G.Borges Fernandes, M.http://sedici.unlp.edu.ar:80/handle/10915/1047042020-09-15T20:05:41Z2018-01-01T00:00:00ZArticulo
Astronomy and Astrophysics; vol. 612
Context. B[e] supergiants are massive post-main-sequence stars, surrounded by a complex circumstellar environment where molecules and dust can survive. The shape in which the material is distributed around these objects and its dynamics as well as the mechanisms that give rise to these structures are not well understood.
Aims. The aim is to deepen our knowledge of the structure and kinematics of the circumstellar disc of the B[e] supergiant LHA 120-S 35.
Methods. High-resolution optical spectra were obtained in three different years. Forbidden emission lines, that contribute to trace the disc at different distances from the star, are modelled in order to determine the kinematical properties of their line-forming regions, assuming Keplerian rotation. In addition, we used low-resolution near-infrared spectra to explore the variability of molecular emission.
Results. LHA 120-S 35 displays an evident spectral variability in both optical and infrared regions. The P-Cygni line profiles of H I, as well as those of Fe II and O I, suggest the presence of a strong bipolar clumped wind. We distinguish density enhancements in the P-Cygni absorption component of the first Balmer lines, which show variations in both velocity and strength. The P-Cygni profile emission component is double-peaked, indicating the presence of a rotating circumstellar disc surrounding the star. We also observe line-profile variations in the permitted and forbidden features of Fe II and O I. In the infrared, we detect variations in the intensity of the H I emission lines as well as in the emission of the CO band-heads. Moreover, we find that the profiles of each [Ca II] and [O I] emission lines contain contributions from spatially different (complete or partial) rings. Globally, we find evidence of detached multi-ring structures, revealing density variations along the disc. We identify an inner ring, with sharp edge, where [Ca II] and [O I] lines share their forming region with the CO molecular bands. The outermost regions show a complex structure, outlined by fragmented clumps or partial-ring features of Ca II and O I. Additionally, we observe variations in the profiles of the only visible absorption features, the He I lines.
Conclusions. We suggest that LHA 120-S 35 has passed through the red-supergiant (RSG) phase and evolves back bluewards in the Hertzsprung-Russell diagram. In this scenario, the formation of the complex circumstellar structure could be the result of the wind–wind interactions of the post-RSG wind with the previously ejected material from the RSG. The accumulation of material in the circumstellar environment could be attributed to enhanced mass-loss, probably triggered by stellar pulsations. However, the presence of a binary companion cannot be excluded. Finally, we find that LHA 120-S 35 is the third B[e] supergiant belonging to a young stellar cluster.
2018-01-01T00:00:00ZContext. B[e] supergiants are massive post-main-sequence stars, surrounded by a complex circumstellar environment where molecules and dust can survive. The shape in which the material is distributed around these objects and its dynamics as well as the mechanisms that give rise to these structures are not well understood.
Aims. The aim is to deepen our knowledge of the structure and kinematics of the circumstellar disc of the B[e] supergiant LHA 120-S 35.
Methods. High-resolution optical spectra were obtained in three different years. Forbidden emission lines, that contribute to trace the disc at different distances from the star, are modelled in order to determine the kinematical properties of their line-forming regions, assuming Keplerian rotation. In addition, we used low-resolution near-infrared spectra to explore the variability of molecular emission.
Results. LHA 120-S 35 displays an evident spectral variability in both optical and infrared regions. The P-Cygni line profiles of H I, as well as those of Fe II and O I, suggest the presence of a strong bipolar clumped wind. We distinguish density enhancements in the P-Cygni absorption component of the first Balmer lines, which show variations in both velocity and strength. The P-Cygni profile emission component is double-peaked, indicating the presence of a rotating circumstellar disc surrounding the star. We also observe line-profile variations in the permitted and forbidden features of Fe II and O I. In the infrared, we detect variations in the intensity of the H I emission lines as well as in the emission of the CO band-heads. Moreover, we find that the profiles of each [Ca II] and [O I] emission lines contain contributions from spatially different (complete or partial) rings. Globally, we find evidence of detached multi-ring structures, revealing density variations along the disc. We identify an inner ring, with sharp edge, where [Ca II] and [O I] lines share their forming region with the CO molecular bands. The outermost regions show a complex structure, outlined by fragmented clumps or partial-ring features of Ca II and O I. Additionally, we observe variations in the profiles of the only visible absorption features, the He I lines.
Conclusions. We suggest that LHA 120-S 35 has passed through the red-supergiant (RSG) phase and evolves back bluewards in the Hertzsprung-Russell diagram. In this scenario, the formation of the complex circumstellar structure could be the result of the wind–wind interactions of the post-RSG wind with the previously ejected material from the RSG. The accumulation of material in the circumstellar environment could be attributed to enhanced mass-loss, probably triggered by stellar pulsations. However, the presence of a binary companion cannot be excluded. Finally, we find that LHA 120-S 35 is the third B[e] supergiant belonging to a young stellar cluster.Stellar Populations in a semi-analytic model I: Bulges of Milky Way-like galaxiesGargiulo, Ignacio DanielCora, Sofía AlejandraVega Martínez, Cristian AntonioGonzález, Osmar AlcidesZoccali, ManuelaGonzález, R.Ruiz, Andrés NicolásPadilla, Nelson Davidhttp://sedici.unlp.edu.ar:80/handle/10915/1021262020-08-15T20:05:50Z2017-12-01T00:00:00ZPreprint
Monthly Notices of the Royal Astronomical Society; vol. 472, no. 4
We study the stellar populations of bulges of MilkyWay-like (MW-like) galaxies with the aim of identifying the physical processes involved in the formation of the bulge of our Galaxy. We use the semi-analytic model of galaxy formation and evolution SAG adapted to this aim; these kind of models can trace the properties of galaxies and their components like stellar discs, bulges and haloes, but resolution limits prevent them from reaching the scale of stellar populations (SPs). Properties of groups of stars formed during single star formation events are stored and tracked in the model and results are compared with observations of stars in the galactic bulge. MW-like galaxies are selected using two different criteria. One of them considers intrinsic photo-metric properties and the second is focused on the cosmological context of the local group (LG) of galaxies. We compare our model results with spectroscopic and photometric stellar metallicity distributions. We find that 87 per cent of stars in bulges of MW-type galaxies in our model are accreted and formed in starbursts during disc instability events. Mergers contribute to 13 per cent of the mass budget of the bulge and are responsible for the low metallicity tail of the distribution. Abundance ratios of α elements with respect to iron, [α/Fe], are measured in SPs of model galaxies. The patterns found in the model for SPs with different origins help to explain the lack of a gradient of [α/Fe] ratios in observed stars along the minor axis of the bulge.
2017-12-01T00:00:00ZWe study the stellar populations of bulges of MilkyWay-like (MW-like) galaxies with the aim of identifying the physical processes involved in the formation of the bulge of our Galaxy. We use the semi-analytic model of galaxy formation and evolution SAG adapted to this aim; these kind of models can trace the properties of galaxies and their components like stellar discs, bulges and haloes, but resolution limits prevent them from reaching the scale of stellar populations (SPs). Properties of groups of stars formed during single star formation events are stored and tracked in the model and results are compared with observations of stars in the galactic bulge. MW-like galaxies are selected using two different criteria. One of them considers intrinsic photo-metric properties and the second is focused on the cosmological context of the local group (LG) of galaxies. We compare our model results with spectroscopic and photometric stellar metallicity distributions. We find that 87 per cent of stars in bulges of MW-type galaxies in our model are accreted and formed in starbursts during disc instability events. Mergers contribute to 13 per cent of the mass budget of the bulge and are responsible for the low metallicity tail of the distribution. Abundance ratios of α elements with respect to iron, [α/Fe], are measured in SPs of model galaxies. The patterns found in the model for SPs with different origins help to explain the lack of a gradient of [α/Fe] ratios in observed stars along the minor axis of the bulge.Resonance capture and dynamics of three-planet systemsCharalambous, CarolinaMartí, Javier GuillermoBeauge, CristianRamos, Ximena Soledadhttp://sedici.unlp.edu.ar:80/handle/10915/1003492020-07-09T20:05:38Z2018-06-01T00:00:00ZArticulo
Monthly Notices of the Royal Astronomical Society; vol. 477, no. 1
We present a series of dynamical maps for fictitious three-planet systems in initially circular coplanar orbits. These maps have unveiled a rich resonant structure involving two or three planets, as well as indicating possible migration routes from secular to double resonances or pure three-planet commensurabilities. These structures are then compared to the present-day orbital architecture of observed resonant chains. In a second part of the paper, we describe N-body simulations of type-I migration. Depending on the orbital decay time-scale, we show that three-planet systems may be trapped in different combinations of independent commensurabilities: (i) double resonances, (ii) intersection between a two-planet and a first-order three-planet resonances, and (iii) simultaneous libration in two first-order three-planet resonances. These latter outcomes are found for slow migrations, while double resonances are almost always the final outcome in high-density discs. Finally, we discuss an application to the TRAPPIST-1 system. We find that, for low migration rates and planetary masses of the order of the estimated values, most three-planet sub-systems are able to reach the observed double resonances after following evolutionary routes defined by pure three-planet resonances. The final orbital configuration shows resonance offsets comparable with present-day values without the need of tidal dissipation. For the 8/5 resonance proposed to dominate the dynamics of the two inner planets, we find little evidence of its dynamical significance; instead, we propose that this relation between mean motions could be a consequence of the interaction between a pure three-planet resonance and a two-planet commensurability between planets c and d.
2018-06-01T00:00:00ZWe present a series of dynamical maps for fictitious three-planet systems in initially circular coplanar orbits. These maps have unveiled a rich resonant structure involving two or three planets, as well as indicating possible migration routes from secular to double resonances or pure three-planet commensurabilities. These structures are then compared to the present-day orbital architecture of observed resonant chains. In a second part of the paper, we describe N-body simulations of type-I migration. Depending on the orbital decay time-scale, we show that three-planet systems may be trapped in different combinations of independent commensurabilities: (i) double resonances, (ii) intersection between a two-planet and a first-order three-planet resonances, and (iii) simultaneous libration in two first-order three-planet resonances. These latter outcomes are found for slow migrations, while double resonances are almost always the final outcome in high-density discs. Finally, we discuss an application to the TRAPPIST-1 system. We find that, for low migration rates and planetary masses of the order of the estimated values, most three-planet sub-systems are able to reach the observed double resonances after following evolutionary routes defined by pure three-planet resonances. The final orbital configuration shows resonance offsets comparable with present-day values without the need of tidal dissipation. For the 8/5 resonance proposed to dominate the dynamics of the two inner planets, we find little evidence of its dynamical significance; instead, we propose that this relation between mean motions could be a consequence of the interaction between a pure three-planet resonance and a two-planet commensurability between planets c and d.Vinculacion entre varios cúmulos estelares y estructuras del medio interestelarCorti, Mariela AlejandraBaume, Gustavo LuisPanei, Jorge AlejandroSuad, L. A.Testori, Juan CarlosBorissova, J.Kurtev, R.Chené, A. N.Ramirez Alegria, S.http://sedici.unlp.edu.ar:80/handle/10915/988692020-06-24T04:05:26Z2015-08-01T00:00:00ZArticulo
Boletín de la Asociación Argentina de Astronomía; vol. 57
Se estudiaron los cúmulos inmersos DBS 77, 78, 102, 160 y 161 localizados en el plano Galáctico en el cuarto cuadrante de la Vía Láctea y el medio interestelar (MIE) circundante. Se analizó fotometría UBVIc (SOAR) y espectroscopía infrarroja (NTT, ESO). Estos datos fueron complementados con las bandas JHK (VVV+2MASS), H I en 21 cm (SGPS), 1.4 GHz (ATCA) y 4.85 GHz (PMN). Se realizó un análisis multibanda y clasificación espectral de las estrellas brillantes de cada zona. Se identificaron también, estructuras del MIE posiblemente vinculadas con los cúmulos. Finalmente, se obtuvieron valores preliminares para los parámetros fundamentales de los cúmulos estudiados y de las estructuras del MIE. Se estudió la vinculación entre ambos; We study the embedded clusters DBS77, 78, 102, 160, and 161 located in the Galactic plane in the fourth quadrant of the Milky Way and the surrounding interstellar medium (ISM). We analyzed UBVIc photometry (SOAR) and infrared spectroscopy (NTT, ESO). We complemented these data with JHK (VVV2MASS), HI 21 cm bands (SGPS), 1.4 GHz (ATCA), and 4.85 GHz (PMN). We did multiband analysis and spectral classification of the brightest stars in each area. We also identified the ISM structures possibly related to the clusters. Finally, we obtained the main parameters of the studied clusters, the structures of the ISM and the link between them.
2015-08-01T00:00:00ZSe estudiaron los cúmulos inmersos DBS 77, 78, 102, 160 y 161 localizados en el plano Galáctico en el cuarto cuadrante de la Vía Láctea y el medio interestelar (MIE) circundante. Se analizó fotometría UBVIc (SOAR) y espectroscopía infrarroja (NTT, ESO). Estos datos fueron complementados con las bandas JHK (VVV+2MASS), H I en 21 cm (SGPS), 1.4 GHz (ATCA) y 4.85 GHz (PMN). Se realizó un análisis multibanda y clasificación espectral de las estrellas brillantes de cada zona. Se identificaron también, estructuras del MIE posiblemente vinculadas con los cúmulos. Finalmente, se obtuvieron valores preliminares para los parámetros fundamentales de los cúmulos estudiados y de las estructuras del MIE. Se estudió la vinculación entre ambos
We study the embedded clusters DBS77, 78, 102, 160, and 161 located in the Galactic plane in the fourth quadrant of the Milky Way and the surrounding interstellar medium (ISM). We analyzed UBVIc photometry (SOAR) and infrared spectroscopy (NTT, ESO). We complemented these data with JHK (VVV2MASS), HI 21 cm bands (SGPS), 1.4 GHz (ATCA), and 4.85 GHz (PMN). We did multiband analysis and spectral classification of the brightest stars in each area. We also identified the ISM structures possibly related to the clusters. Finally, we obtained the main parameters of the studied clusters, the structures of the ISM and the link between them.The new HI supershell GS263-02+45 and the OB Association Bochum 7: close relatives?Corti, Mariela AlejandraArnal, Edmundo Marcelohttp://sedici.unlp.edu.ar:80/handle/10915/973122020-06-02T20:06:19Z2008-12-01T00:00:00ZArticulo
Revista Mexicana de Astronomía y Astrofísica; vol. 33
Neutral hydrogen (HI) supershells are usually identified, in a given velocity range, as a brightness temperature minimum in the HI distribution that is surrounded by walls of HI emission. McClure-Griffiths et al. (2002) reported the discovery of GSH263+00+47, centered at (l,b) = (263°.0, 0°.0). The OB association Bochum 7 (l,b) = (265°.0, -2°.0) is seen in projection onto the outer border of GSH263+00+47.
2008-12-01T00:00:00ZNeutral hydrogen (HI) supershells are usually identified, in a given velocity range, as a brightness temperature minimum in the HI distribution that is surrounded by walls of HI emission. McClure-Griffiths et al. (2002) reported the discovery of GSH263+00+47, centered at (l,b) = (263°.0, 0°.0). The OB association Bochum 7 (l,b) = (265°.0, -2°.0) is seen in projection onto the outer border of GSH263+00+47.Novel constraints on fermionic dark matter from galactic observables I: The Milky WayArgüelles, Carlos RaúlKrut, A.Rueda, J. A.Ruffini, R.http://sedici.unlp.edu.ar:80/handle/10915/958862020-05-14T20:05:51Z2018-09-01T00:00:00ZPreprint
Physics of the Dark Universe; vol. 21
We have recently introduced a new model for the distribution of dark matter (DM) in galaxies based on a self-gravitating system of massive fermions at finite temperatures, the Ruffini–Argü elles–Rueda (RAR) model. We show that this model, for fermion masses in the keV range, explains the DM halo of the Galaxy and predicts the existence of a denser quantum core at the center. We demonstrate here that the introduction of a cutoff in the fermion phase-space distribution, necessary to account for the finite Galaxy size, defines a new solution with a central core which represents an alternative to the black hole (BH) scenario for SgrA*. For a fermion mass in the range mc2=48–345 keV, the DM halo distribution is in agreement with the Milky Way rotation curve data, while harbors a dense quantum core of about 4×106M⊙ within the S2-star pericenter.
2018-09-01T00:00:00ZWe have recently introduced a new model for the distribution of dark matter (DM) in galaxies based on a self-gravitating system of massive fermions at finite temperatures, the Ruffini–Argü elles–Rueda (RAR) model. We show that this model, for fermion masses in the keV range, explains the DM halo of the Galaxy and predicts the existence of a denser quantum core at the center. We demonstrate here that the introduction of a cutoff in the fermion phase-space distribution, necessary to account for the finite Galaxy size, defines a new solution with a central core which represents an alternative to the black hole (BH) scenario for SgrA*. For a fermion mass in the range mc2=48–345 keV, the DM halo distribution is in agreement with the Milky Way rotation curve data, while harbors a dense quantum core of about 4×106M⊙ within the S2-star pericenter.Discovery of a deep Seyfert-2 galaxy at z = 0.222 behind NGC 300Combi, Jorge ArielGarcía, FedericoRodríguez, María JimenaGamen, Roberto ClaudioCellone, Sergio Aldohttp://sedici.unlp.edu.ar:80/handle/10915/957442020-05-14T20:05:53Z2016-04-01T00:00:00ZArticulo
Monthly Notices of the Royal Astronomical Society; vol. 460, no. 2
We report on the unveiling of the nature of the unidentified X-ray source 3XMM J005450.3–373849 as a Seyfert-2 galaxy located behind the spiral galaxy NGC 300 using <i>Hubble Space Telescope</i> data, new spectroscopic Gemini observations and available <i>XMM–Newton</i> and <i>Chandra</i> data. We show that the X-ray source is positionally coincident with an extended optical source, composed of a marginally resolved nucleus/bulge, surrounded by an elliptical disc-like feature and two symmetrical outer rings. The optical spectrum is typical of a Seyfert-2 galaxy redshifted to z = 0.222 ± 0.001, which confirms that the source is not physically related to NGC 300. At this redshift the source would be located at 909 ± 4 Mpc (comoving distance in the standard model). The X-ray spectra of the source are well fitted by an absorbed power-law model. By tying N<sub>H</sub> between the six available spectra, we found a variable index Γ running from ∼2 in 2000–2001 to 1.4–1.6 in the 2005–2014 period. Alternatively, by tying Γ, we found variable absorption columns of N<sub>H</sub> ∼ 0.34 × 10<sup>−22</sup> cm<sup>−2</sup> in 2000–2001, and 0.54−0.75 × 10<sup>−22</sup> cm<sup>−2</sup> in the 2005–2014 period. Although we cannot distinguish between a spectral or absorption origin, from the derived unabsorbed X-ray fluxes, we are able to assure the presence of long-term X-ray variability. Furthermore, the unabsorbed X-ray luminosities of 0.8–2 × 10<sup>43</sup> erg s<sup>−1</sup> derived in the X-ray band are in agreement with a weakly obscured Seyfert-2 AGN at z ≈ 0.22.
2016-04-01T00:00:00ZWe report on the unveiling of the nature of the unidentified X-ray source 3XMM J005450.3–373849 as a Seyfert-2 galaxy located behind the spiral galaxy NGC 300 using <i>Hubble Space Telescope</i> data, new spectroscopic Gemini observations and available <i>XMM–Newton</i> and <i>Chandra</i> data. We show that the X-ray source is positionally coincident with an extended optical source, composed of a marginally resolved nucleus/bulge, surrounded by an elliptical disc-like feature and two symmetrical outer rings. The optical spectrum is typical of a Seyfert-2 galaxy redshifted to z = 0.222 ± 0.001, which confirms that the source is not physically related to NGC 300. At this redshift the source would be located at 909 ± 4 Mpc (comoving distance in the standard model). The X-ray spectra of the source are well fitted by an absorbed power-law model. By tying N<sub>H</sub> between the six available spectra, we found a variable index Γ running from ∼2 in 2000–2001 to 1.4–1.6 in the 2005–2014 period. Alternatively, by tying Γ, we found variable absorption columns of N<sub>H</sub> ∼ 0.34 × 10<sup>−22</sup> cm<sup>−2</sup> in 2000–2001, and 0.54−0.75 × 10<sup>−22</sup> cm<sup>−2</sup> in the 2005–2014 period. Although we cannot distinguish between a spectral or absorption origin, from the derived unabsorbed X-ray fluxes, we are able to assure the presence of long-term X-ray variability. Furthermore, the unabsorbed X-ray luminosities of 0.8–2 × 10<sup>43</sup> erg s<sup>−1</sup> derived in the X-ray band are in agreement with a weakly obscured Seyfert-2 AGN at z ≈ 0.22.Modelos matemáticos autoconsistentes de galaxias elípticasZorzi, A. F.Muzzio, Juan Carloshttp://sedici.unlp.edu.ar:80/handle/10915/945862020-04-30T04:05:35Z2009-01-01T00:00:00ZObjeto de conferencia
II Congreso de Matemática Aplicada, Computacional e Industrial (MACI) (Rosario, 14 al 16 de diciembre de 2009)
La construcción de modelos matemáticos de sistemas estelares triaxiales autoconsistentes, adecuados para representar galaxias elípticas, es compleja y debe recurrirse a métodos númericos. El método de N-cuerpos ha adquirido últimamente merecida popularidad para esta tarea y lo hemos utilizado en varios trabajos recientes. Sin embargo, el integrador de N-cuerpos que veníamos empleando no resulta del todo satisfactorio, particularmente en el caso de modelos con fuerte concentración central. En este trabajo presentamos nuevos modelos que hemos construido utilizando el programa de N-cuerpos de [6], que resulta más adecuado para ese fin.
2009-01-01T00:00:00ZLa construcción de modelos matemáticos de sistemas estelares triaxiales autoconsistentes, adecuados para representar galaxias elípticas, es compleja y debe recurrirse a métodos númericos. El método de N-cuerpos ha adquirido últimamente merecida popularidad para esta tarea y lo hemos utilizado en varios trabajos recientes. Sin embargo, el integrador de N-cuerpos que veníamos empleando no resulta del todo satisfactorio, particularmente en el caso de modelos con fuerte concentración central. En este trabajo presentamos nuevos modelos que hemos construido utilizando el programa de N-cuerpos de [6], que resulta más adecuado para ese fin.New evolutionary sequences for the hot H-deficient white dwarfs on the basis of a full account of progenitor evolutionAlthaus, Leandro GabrielPanei, Jorge AlejandroMiller Bertolami, Marcelo MiguelGarcía Berro, EnriqueCórsico, Alejandro HugoRomero, Alejandra DanielaKepler, S. O.Rohrmann, Rene Danielhttp://sedici.unlp.edu.ar:80/handle/10915/940482020-04-23T04:05:41Z2009-12-01T00:00:00ZArticulo
Astrophysical Journal; vol. 704
We present full evolutionary calculations appropriate for the study of hot hydrogen-deficient DO white dwarfs, PG 1159 stars, and DB white dwarfs. White dwarf sequences are computed for a wide range of stellar masses and helium envelopes on the basis of a complete treatment of the evolutionary history of progenitors stars, including the core hydrogen and helium burning phases, the thermally pulsing asymptotic giant branch phase, and the born-again episode that is responsible for the hydrogen deficiency. We also provide colors and magnitudes for the new sequences for Teff < 40,000 K, where the NLTE effects are not dominant. These new calculations provide a homogeneous set of evolutionary tracks appropriate for mass and age determinations for both PG 1159 stars and DO white dwarfs. The calculations are extended down to an effective temperature of 7000 K. We applied these new tracks to redetermine stellar masses and ages of all known DO white dwarfs with spectroscopically determined effective temperatures and gravities, and compare them with previous results. We also compare for the first time consistent mass determinations for both DO and PG 1159 stars, and find a considerably higher mean mass for the DO white dwarfs. We discuss as well the chemical profile expected in the envelope of variable DB white dwarfs from the consideration of the evolutionary history of progenitor stars. Finally, we present tentative evidence for a different evolutionary channel, other than that involving the PG 1159 stars, for the formation of hot, hydrogen-deficient white dwarfs
2009-12-01T00:00:00ZWe present full evolutionary calculations appropriate for the study of hot hydrogen-deficient DO white dwarfs, PG 1159 stars, and DB white dwarfs. White dwarf sequences are computed for a wide range of stellar masses and helium envelopes on the basis of a complete treatment of the evolutionary history of progenitors stars, including the core hydrogen and helium burning phases, the thermally pulsing asymptotic giant branch phase, and the born-again episode that is responsible for the hydrogen deficiency. We also provide colors and magnitudes for the new sequences for Teff < 40,000 K, where the NLTE effects are not dominant. These new calculations provide a homogeneous set of evolutionary tracks appropriate for mass and age determinations for both PG 1159 stars and DO white dwarfs. The calculations are extended down to an effective temperature of 7000 K. We applied these new tracks to redetermine stellar masses and ages of all known DO white dwarfs with spectroscopically determined effective temperatures and gravities, and compare them with previous results. We also compare for the first time consistent mass determinations for both DO and PG 1159 stars, and find a considerably higher mean mass for the DO white dwarfs. We discuss as well the chemical profile expected in the envelope of variable DB white dwarfs from the consideration of the evolutionary history of progenitor stars. Finally, we present tentative evidence for a different evolutionary channel, other than that involving the PG 1159 stars, for the formation of hot, hydrogen-deficient white dwarfsXMM-Newton observations of NGC 3268 in the Antlia Galaxy Cluster: characterization of a hidden group of galaxies at z ~0.41Gargiulo, Ignacio DanielGarcía, FedericoCombi, Jorge ArielCaso, Juan PabloBassino, Lilia Patriciahttp://sedici.unlp.edu.ar:80/handle/10915/940472020-04-23T04:05:47Z2018-09-01T00:00:00ZArticulo
Monthly Notices of the Royal Astronomical Society; vol. 479, no. 1
We report on a detailed X-ray study of the extended emission of the intracluster medium (ICM) around NGC3268 in the Antlia Cluster of galaxies, together with a characterization of an extended source in the field, namely a background cluster of galaxies at z ~ 0.41, which was previously accounted as an X-ray point source. The spectral properties of the extended emission of the gas present in Antlia were studied using data from the XMM-Newton satellite, complemented with optical images of Cerro Tololo Inter-American Observatory (CTIO) Blanco telescope, to attain for associations of the optical sources with the X-ray emission. The XMM-Newton observations show that the intracluster gas is concentrated in a region centred in one of the main galaxies of the cluster, NGC3268. By means of a spatially resolved spectral analysis, we derived abundances of the ICM plasma. We found a wall-like feature in the north-east direction, where the gas is characterized by a lower temperature with respect to the rest of the ICM. Furthermore, using combined optical observations, we inferred the presence of an elliptical galaxy in the centre of the extended X-ray source considered as a background cluster, which favours this interpretation.
2018-09-01T00:00:00ZWe report on a detailed X-ray study of the extended emission of the intracluster medium (ICM) around NGC3268 in the Antlia Cluster of galaxies, together with a characterization of an extended source in the field, namely a background cluster of galaxies at z ~ 0.41, which was previously accounted as an X-ray point source. The spectral properties of the extended emission of the gas present in Antlia were studied using data from the XMM-Newton satellite, complemented with optical images of Cerro Tololo Inter-American Observatory (CTIO) Blanco telescope, to attain for associations of the optical sources with the X-ray emission. The XMM-Newton observations show that the intracluster gas is concentrated in a region centred in one of the main galaxies of the cluster, NGC3268. By means of a spatially resolved spectral analysis, we derived abundances of the ICM plasma. We found a wall-like feature in the north-east direction, where the gas is characterized by a lower temperature with respect to the rest of the ICM. Furthermore, using combined optical observations, we inferred the presence of an elliptical galaxy in the centre of the extended X-ray source considered as a background cluster, which favours this interpretation.Tracing the assembly history of NGC 1395 through its Globular Cluster SystemEscudero, Carlos GabrielFaifer, Favio RaúlSmith Castelli, Analía VivianaForte, Juan CarlosSesto, Leandro AlbertoGonzález, Nélida MabelScalia, María Ceciliahttp://sedici.unlp.edu.ar:80/handle/10915/940462020-04-23T04:05:53Z2018-03-01T00:00:00ZArticulo
Monthly Notices of the Royal Astronomical Society; vol. 474, no. 4
We used deep Gemini-South/GMOS g'r'i'z' images to study the globular cluster (GC) system of the massive elliptical galaxy NGC1395, located in the Eridanus supergroup. The photometric analysis of the GC candidates reveals a clear colour bimodality distribution, indicating the presence of 'blue' and 'red' GC subpopulations. While a negative radial colour gradient is detected in the projected spatial distribution of the red GCs, the blue GCs display a shallow colour gradient. The blue GCs also display a remarkable shallow and extended surface density profile, suggesting a significant accretion of low-mass satellites in the outer halo of the galaxy. In addition, the slope of the projected spatial distribution of the blue GCs in the outer regions of the galaxy, is similar to that of the X-ray halo emission. Integrating up to 165 kpc the profile of the projected spatial distribution of the GCs, we estimated a total GC population and specific frequency of 6000 ± 1100 and S N = 7.4 ± 1.4, respectively. Regarding NGC1395 itself, the analysis of the deep Gemini/GMOS images shows a low surface brightness umbrella-like structure indicating, at least, one recent merger event. Through relations recently published in the literature, we obtained global parameters, such as M stellar = 9.32 × 10 11 M⊙ and M h = 6.46 × 10 13 M⊙. Using public spectroscopic data, we derive stellar population parameters of the central region of the galaxy by the full spectral fitting technique. We have found that this region seems to be dominated for an old stellar population, in contrast to findings of young stellar populations from the literature.
2018-03-01T00:00:00ZWe used deep Gemini-South/GMOS g'r'i'z' images to study the globular cluster (GC) system of the massive elliptical galaxy NGC1395, located in the Eridanus supergroup. The photometric analysis of the GC candidates reveals a clear colour bimodality distribution, indicating the presence of 'blue' and 'red' GC subpopulations. While a negative radial colour gradient is detected in the projected spatial distribution of the red GCs, the blue GCs display a shallow colour gradient. The blue GCs also display a remarkable shallow and extended surface density profile, suggesting a significant accretion of low-mass satellites in the outer halo of the galaxy. In addition, the slope of the projected spatial distribution of the blue GCs in the outer regions of the galaxy, is similar to that of the X-ray halo emission. Integrating up to 165 kpc the profile of the projected spatial distribution of the GCs, we estimated a total GC population and specific frequency of 6000 ± 1100 and S N = 7.4 ± 1.4, respectively. Regarding NGC1395 itself, the analysis of the deep Gemini/GMOS images shows a low surface brightness umbrella-like structure indicating, at least, one recent merger event. Through relations recently published in the literature, we obtained global parameters, such as M stellar = 9.32 × 10 11 M⊙ and M h = 6.46 × 10 13 M⊙. Using public spectroscopic data, we derive stellar population parameters of the central region of the galaxy by the full spectral fitting technique. We have found that this region seems to be dominated for an old stellar population, in contrast to findings of young stellar populations from the literature.Computational Taxonomy for Identification of "Moving Groups": Applied to Open ClustersOrellana, Rosa BeatrizPerichinsky, GregorioPlastino, Ángel Luishttp://sedici.unlp.edu.ar:80/handle/10915/940452020-04-23T04:06:00Z2010-11-01T00:00:00ZArticulo
Annals of the Faculty of Engineering Hunedoara; vol. VIII, no. 29
A new method is presented here to identify the members of an open cluster, based on computational taxonomy: “the spectral method”. The characters used for the analysis are position and proper motion of all the stars belonging to the cluster’s region. Taxonomy allows to groups the stars together (OTU’s) in clusters, based on its genotypic characteristic, which shows the similarity, between two or more Stars (OTU’s). The method has been applied to open cluster NGC2516. The outcome list of members agrees very well with the one obtained by applying other methods.
2010-11-01T00:00:00ZA new method is presented here to identify the members of an open cluster, based on computational taxonomy: “the spectral method”. The characters used for the analysis are position and proper motion of all the stars belonging to the cluster’s region. Taxonomy allows to groups the stars together (OTU’s) in clusters, based on its genotypic characteristic, which shows the similarity, between two or more Stars (OTU’s). The method has been applied to open cluster NGC2516. The outcome list of members agrees very well with the one obtained by applying other methods.Stellar systems in the direction of Pegasus I: I. Low surface brightness galaxiesGonzález, Nélida MabelSmith Castelli, Analía VivianaFaifer, Favio RaúlEscudero, Carlos GabrielCellone, Sergio Aldohttp://sedici.unlp.edu.ar:80/handle/10915/940442020-04-23T04:06:04Z2018-12-01T00:00:00ZArticulo
Astronomy and Astrophysics; vol. 620
Context. In spite of the numerous studies of low-luminosity galaxies in different environments, there is still no consensus about their formation scenario. In particular, a large number of galaxies displaying extremely low surface brightnesses have been detected in recent years and the nature of these objects is still under discussion. Aims. In order to enlarge the sample of known low-surface-brightness (LSB) galaxies and to try to provide clues about their nature, we report the detection of eight such objects (μ eff,g′ â 27 mag arcsec -2 ) towards the group of galaxies Pegasus I. They are located, in projection, within a radius of ∼200 kpc in the very center of Pegasus I, close to the dominant elliptical galaxies NGC 7619 and NGC 7626. Methods. We analyzed deep, high-quality GEMINI-GMOS images with ELLIPSE within IRAF in order to obtain their brightness profiles and structural parameters. We also fit Sérsic functions to these profiles in order to compare their properties with those of typical early-Type galaxies. Results. Assuming that these galaxies are at the distance of Pegasus I, we have found that their sizes are intermediate among similar objects reported in the literature. In particular, we found that three of these galaxies can be classified as ultra-diffuse galaxies and a fourth one displays a nucleus. The eight new LSB galaxies show significant color dispersion around the extrapolation towards faint luminosities of the color-magnitude relation defined by typical early-Type galaxies. In addition, they display values of the Sérsic index below 1 (concave brightness profiles in linear scale), in agreement with values obtained for LSB galaxies in other environments. Conclusions. We show that there seems to be a bias effect in the size distributions of the detected LSBs in different environments, in the sense that more distant groups/clusters lack small r eff objects, while large systems are not found in the Local Group and nearby environments. While there may be an actual shortage of large LSB galaxies in low-density environments like the Local Group, the non-detection of small (and faint) systems at large distances is clearly a selection effect. As an example, LSB galaxies with similar sizes to those of the satellites of Andromeda in the Local Group will be certainly missed in a visual identification at the distance of Pegasus I.
2018-12-01T00:00:00ZContext. In spite of the numerous studies of low-luminosity galaxies in different environments, there is still no consensus about their formation scenario. In particular, a large number of galaxies displaying extremely low surface brightnesses have been detected in recent years and the nature of these objects is still under discussion. Aims. In order to enlarge the sample of known low-surface-brightness (LSB) galaxies and to try to provide clues about their nature, we report the detection of eight such objects (μ eff,g′ â 27 mag arcsec -2 ) towards the group of galaxies Pegasus I. They are located, in projection, within a radius of ∼200 kpc in the very center of Pegasus I, close to the dominant elliptical galaxies NGC 7619 and NGC 7626. Methods. We analyzed deep, high-quality GEMINI-GMOS images with ELLIPSE within IRAF in order to obtain their brightness profiles and structural parameters. We also fit Sérsic functions to these profiles in order to compare their properties with those of typical early-Type galaxies. Results. Assuming that these galaxies are at the distance of Pegasus I, we have found that their sizes are intermediate among similar objects reported in the literature. In particular, we found that three of these galaxies can be classified as ultra-diffuse galaxies and a fourth one displays a nucleus. The eight new LSB galaxies show significant color dispersion around the extrapolation towards faint luminosities of the color-magnitude relation defined by typical early-Type galaxies. In addition, they display values of the Sérsic index below 1 (concave brightness profiles in linear scale), in agreement with values obtained for LSB galaxies in other environments. Conclusions. We show that there seems to be a bias effect in the size distributions of the detected LSBs in different environments, in the sense that more distant groups/clusters lack small r eff objects, while large systems are not found in the Local Group and nearby environments. While there may be an actual shortage of large LSB galaxies in low-density environments like the Local Group, the non-detection of small (and faint) systems at large distances is clearly a selection effect. As an example, LSB galaxies with similar sizes to those of the satellites of Andromeda in the Local Group will be certainly missed in a visual identification at the distance of Pegasus I.LP-VIcode: a program to compute a suite of variational chaos indicatorsCarpintero, Daniel DiegoMaffione, Nicolás PabloDarriba, Luciano Arielhttp://sedici.unlp.edu.ar:80/handle/10915/940032020-04-23T04:06:09Z2014-07-01T00:00:00ZPreprint
Astronomy and Computing; vol. 5
An important point in analyzing the dynamics of a given stellar or planetary system is the reliable identification of the chaotic or regular behavior of its orbits. We introduce here the program LP-VIcode, a fully operational code which efficiently computes a suite of ten variational chaos indicators for dynamical systems in any number of dimensions. The user may choose to simultaneously compute any number of chaos indicators among the following: the Lyapunov Exponents, the Mean Exponential Growth factor of Nearby Orbits, the Slope Estimation of the largest Lyapunov Characteristic Exponent, the Smaller ALignment Index, the Generalized ALignment Index, the Fast Lyapunov Indicator, the Orthogonal Fast Lyapunov Indicator, the dynamical Spectra of Stretching Numbers, the Spectral Distance, and the Relative Lyapunov Indicator. They are combined in an efficient way, allowing the sharing of differential equations whenever this is possible, and the individual stopping of their computation when any of them saturates.
2014-07-01T00:00:00ZAn important point in analyzing the dynamics of a given stellar or planetary system is the reliable identification of the chaotic or regular behavior of its orbits. We introduce here the program LP-VIcode, a fully operational code which efficiently computes a suite of ten variational chaos indicators for dynamical systems in any number of dimensions. The user may choose to simultaneously compute any number of chaos indicators among the following: the Lyapunov Exponents, the Mean Exponential Growth factor of Nearby Orbits, the Slope Estimation of the largest Lyapunov Characteristic Exponent, the Smaller ALignment Index, the Generalized ALignment Index, the Fast Lyapunov Indicator, the Orthogonal Fast Lyapunov Indicator, the dynamical Spectra of Stretching Numbers, the Spectral Distance, and the Relative Lyapunov Indicator. They are combined in an efficient way, allowing the sharing of differential equations whenever this is possible, and the individual stopping of their computation when any of them saturates.An upper limit to the secular variation of the gravitational constant from white dwarf starsGarcía Berro, EnriqueLorén Aguilar, PabloTorres, SantiagoAlthaus, Leandro GabrielIsern, Jordihttp://sedici.unlp.edu.ar:80/handle/10915/939352020-04-21T20:05:54Z2011-05-01T00:00:00ZPreprint
Journal Of Cosmology And Astroparticle Physics; vol. 5
A variation of the gravitational constant over cosmological ages modifies the main sequence lifetimes and white dwarf cooling ages. Using an state-of-the-art stellar evolutionary code we compute the effects of a secularly varying G on the main sequence ages and, employing white dwarf cooling ages computed taking into account the effects of a running G, we place constraints on the rate of variation of Newton's constant. This is done using the white dwarf luminosity function and the distance of the well studied open Galactic cluster NGC 6791. We derive an upper bound Ġ/G ~ −1.8 × 10−12 yr−1. This upper limit for the secular variation of the gravitational constant compares favorably with those obtained using other stellar evolutionary properties, and can be easily improved if deep images of the cluster allow to obtain an improved white dwarf luminosity function.
2011-05-01T00:00:00ZA variation of the gravitational constant over cosmological ages modifies the main sequence lifetimes and white dwarf cooling ages. Using an state-of-the-art stellar evolutionary code we compute the effects of a secularly varying G on the main sequence ages and, employing white dwarf cooling ages computed taking into account the effects of a running G, we place constraints on the rate of variation of Newton's constant. This is done using the white dwarf luminosity function and the distance of the well studied open Galactic cluster NGC 6791. We derive an upper bound Ġ/G ~ −1.8 × 10−12 yr−1. This upper limit for the secular variation of the gravitational constant compares favorably with those obtained using other stellar evolutionary properties, and can be easily improved if deep images of the cluster allow to obtain an improved white dwarf luminosity function.Numerical stabilization of the Levitron's realistic modelOlverá, ArturoDe la Rosa, AbrahamGiordano, Claudia Marcelahttp://sedici.unlp.edu.ar:80/handle/10915/939342020-04-21T20:05:56Z2016-12-01T00:00:00ZPreprint
European Journal of Physics; vol. 225, no. 13-14
The stability of the magnetic levitation showed by the Levit- 10 ron was studied by M.V. Berry as a six degrees of freedom Hamiltonian 11 system using an adiabatic approximation. Further, H.R. Dullin found 12 critical spin rate bounds where the levitation persist and R.F. Gans 13 et al. offered numerical results regarding the initial conditions’ manifold 14 where this occurs. In the line of this series of works, first, we extend the 15 equations of motion to include dissipation for a more realistic model, 16 and then introduce a mechanical forcing to inject energy into the sys- 17 tem in order to prevent the Levitron from falling. A systematic study 18 of the flying time as a function of the forcing parameters is carried out 19 which yields detailed bifurcation diagrams showing an Arnold’s tongues 20 structure. The stability of these solutions were studied with the help 21 of a novel method to compute the maximum Lyapunov exponent called 22 MEGNO. The bifurcation diagrams for MEGNO reproduce the same 23 Arnold’s tongue structure.
2016-12-01T00:00:00ZThe stability of the magnetic levitation showed by the Levit- 10 ron was studied by M.V. Berry as a six degrees of freedom Hamiltonian 11 system using an adiabatic approximation. Further, H.R. Dullin found 12 critical spin rate bounds where the levitation persist and R.F. Gans 13 et al. offered numerical results regarding the initial conditions’ manifold 14 where this occurs. In the line of this series of works, first, we extend the 15 equations of motion to include dissipation for a more realistic model, 16 and then introduce a mechanical forcing to inject energy into the sys- 17 tem in order to prevent the Levitron from falling. A systematic study 18 of the flying time as a function of the forcing parameters is carried out 19 which yields detailed bifurcation diagrams showing an Arnold’s tongues 20 structure. The stability of these solutions were studied with the help 21 of a novel method to compute the maximum Lyapunov exponent called 22 MEGNO. The bifurcation diagrams for MEGNO reproduce the same 23 Arnold’s tongue structure.Footprints in the sand: What can globular clusters tell us about NGC 4753 past?Caso, Juan PabloBassino, Lilia PatriciaGómez, Matiashttp://sedici.unlp.edu.ar:80/handle/10915/939332020-04-21T20:05:58Z2015-11-01T00:00:00ZArticulo
Monthly Notices Of The Royal Astronomical Society; vol. 453
NGC 4753 is a bright (Mv~-22.3) lenticular galaxy. It is a very interesting target to test different theories of formation of lenticular galaxies, due to its low-density environment and complex structure. We perform the first comprehensive study of NGC4753 globular cluster system (GCS), using Gemini/GMOS and CTIO/MosaicII images. Our results indicate a rather poor GCS of ~1000 members. Its azimuthal distribution follows the shape of the galaxy bulge. The GC colour distribution is peculiar, presenting an intermediate subpopulation in addition to blue and red ones. This intermediate subgroup can be explained by a single stellar population with an age of 1.53 Gyr and 0.5 − 1 Zo. The GC specific frequency Sn = 1.3 +/- 0.15 is surprisingly low for a galaxy of its class. The GC luminosity function (GCLF) is also peculiar, with an excess of bright GCs compared to the expected gaussian distribution. The underlying galaxy body has significant substructure, with remnants of spiral arms, dust filaments, and isophote twisting. This, and the fact that NGC4753 hosted two type Ia SNe, support the possibility that the intermediate GC subpopulation may have originated during a recent merger, 1-3 Gyr ago.
2015-11-01T00:00:00ZNGC 4753 is a bright (Mv~-22.3) lenticular galaxy. It is a very interesting target to test different theories of formation of lenticular galaxies, due to its low-density environment and complex structure. We perform the first comprehensive study of NGC4753 globular cluster system (GCS), using Gemini/GMOS and CTIO/MosaicII images. Our results indicate a rather poor GCS of ~1000 members. Its azimuthal distribution follows the shape of the galaxy bulge. The GC colour distribution is peculiar, presenting an intermediate subpopulation in addition to blue and red ones. This intermediate subgroup can be explained by a single stellar population with an age of 1.53 Gyr and 0.5 − 1 Zo. The GC specific frequency Sn = 1.3 +/- 0.15 is surprisingly low for a galaxy of its class. The GC luminosity function (GCLF) is also peculiar, with an excess of bright GCs compared to the expected gaussian distribution. The underlying galaxy body has significant substructure, with remnants of spiral arms, dust filaments, and isophote twisting. This, and the fact that NGC4753 hosted two type Ia SNe, support the possibility that the intermediate GC subpopulation may have originated during a recent merger, 1-3 Gyr ago.