Browsing by Author "Calderón Espinoza, Diego Nicolás"

Now showing 1 - 11 of 11
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    A massive binary system can feed Sgr A*
    (2017) Calderón Espinoza, Diego Nicolás; Cuadra, Jorge
    The enigmatic G2 cloud just passed pericentre around the Galactic Centre super-massive black hole, Sgr A. Despite all theoretical and observational efforts, its nature remains unclear. If purely gaseous, it is possible to explain it as a gas clump formed in a colliding wind binary. Here we study the hypothesis of G2 being one of such clumps ejected from the massive binary IRS 16SW....
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    Analysis of the velocity data of cluster A562
    (2014) Calderón Espinoza, Diego Nicolás; Gómez, P.
    We present a recent study of the dynamics of the cluster of galaxies Abell 562 intended to determine if ram pressure is responsible for the jet bending in the Wide-Angle Tailed (WAT) radio source located in the central elliptical galaxy. Given the properties of the jet and of the intra-cluster medium (ICM), a relative velocity between the galaxy and the ICM greater than 800 km/s is needed for this mechanism to bend the WAT jet. We find that the peculiar velocity of the WAT galaxy is 170 ± 140 km/s which is not enough to produce the bending. This is based on the analysis of the velocity of 146 galaxy cluster members obtained with the Gemini Multi-Object Spectrometer (GMOS) at Gemini North. However, our analysis of these velocity data and archival Chandra data suggests that an off-axis merger occurred in this system. This type of merger typically produces bulk flow motions with peak velocities greater than 1000 km/s which should be enough to explain the bending of the jets....
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    Clump formation through colliding stellar winds in the galactic centre
    (2016) Calderón Espinoza, Diego Nicolás; Ballone, A.; Cuadra Stipetich, Jorge Rodrigo; Schartmann, M.; Burkert, A.; Gillessen, S.
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    Clump formation through colliding stellar winds in the Galactic Centre
    (2017) Calderón Espinoza, Diego Nicolás; Ballone, A.; Cuadra, Jorge; Schartmann, Marc; Burkert, A.; Gillessen, S.
    We study the process of clump formation from hydrodynamic instabilities in stellar wind collisions, using analytical and numerical techniques. We show that the cloud G2 in the Galactic Centre could have been formed in this way, with the most promising sources being compact massive binaries, such as IRS 16SW....
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    Interacting stellar winds: clump formation and accretion onto Sgr A*
    (2018) Calderón Espinoza, Diego Nicolás; Schartmann, Marc; Burkert, . Andreas; Cuadra, Jorge
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    Optical/Near-Infrared Light-Curve Properties of Pulsating Variables in the Cepheid Instability Strip
    (2014) Calderón Espinoza, Diego Nicolás; Hajdu, Gergely; Dékány, I.; Catelan, Márcio
    Making the distinction between Type I and II Cepheids found in the Vista Variables in the Via Lactea (VVV) ESO Public Survey is crucial for the studies of Galactic structure using these variables. As VVV provides only K_{S}-band light curves, this distinction has to be based on near-IR light-curve properties. Because of their reduced amplitudes in the near-IR, however, it is not immediately obvious whether such a distinction can be unambiguously made. To assess this problem, we have compared the VVV and VVV Templates K_{S}-band light-curve properties of 213 Type I and 215 Type II Cepheids using Fourier decomposition. The Fourier parameters of these types were found to be different enough for the purposes of classification. For example, over most of the Cepheid period range, there is an upper limit for the amplitudes of Type I Cepheids. As 50 percent of the Type II variables lie above this limit, half of the variables that could be confused with Type I Cepheids are sorted out by this simple feature alone, suggesting that the automatic classification schemes under development for the VVV Survey will be able to classify such variables with a high degree of accuracy. We have also found that bump Cepheids can be easily identified using VVV data, as the bump feature also appears in the near-IR light curves. Detailed modeling of the light curves of the bump Cepheids found in the VVV data will provide accurate stellar parameters for these stars....
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    Pressure drop may negatively impact supercritical CO2 extraction of citrus peel essential oils in an industrial-size extraction vessel
    (2019) Del Valle Lladser, José Manuel; Calderón Espinoza, Diego Nicolás; Núñez Montoya, Gonzalo Alexis
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    Stellar Winds Pump the Heart of the Milky Way
    (2020) Calderón Espinoza, Diego Nicolás; Cuadra Stipetich, Jorge Rodrigo; Schartmann, M; Burkert, A; Russell, CMP
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    The Galactic Centre source G2 was unlikely born in any of the known massive binaries
    (2018) Calderón Espinoza, Diego Nicolás; Cuadra, Jorge; Schartmann, Marc; Burkert, Andreas; Plewa, P.; Eisenhauer, F.; Habibi, M.
    The source G2 has already completed its pericentre passage around Sgr A*, the supermassive black hole in the centre of our Galaxy. Although it has been monitored for 15 yr, its astrophysical nature and origin still remain unknown. In this work, we aim to test the hypothesis of G2 being the result of a stellar wind collision. To do so, we study the motion and final fate of gas clumps formed as a result of collisions of stellar winds in massive binaries. Our approach is based on a test-particle model in order to describe the trajectories of such clumps. The model takes into account the gravitational field of Sgr A*, the interaction of the clumps with the interstellar medium as well as their finite lifetimes. Our analysis allows us to reject the hypothesis based on four arguments: (i) if G2 has followed a purely Keplerian orbit since its formation, it cannot have been produced in any of the known massive binaries since their motions are not consistent, (ii) in general, gas clumps are evaporated through thermal conduction on very short timescale (⁠<100yr⁠) before getting close enough to Sgr A*, (iii) IRS 16SW, the best candidate for the origin of G2, cannot generate clumps as massive as G2, and (iv) clumps ejected from IRS 16SW describe trajectories significantly different to the observed motion of G2.
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    The role of interacting stellar winds feeding Sagittarius A*.
    (2019) Calderón Espinoza, Diego Nicolás; Cuadra, Jorge; Pontificia Universidad Católica de Chile. Instituto de Astrofísica
    The central parsec of the Milky Way is among the most enigmatic regions in the entire Galaxy. The existence of the central super-massive black hole, Sgr A*, and its proximity allow us to use it as a laboratory for understanding the astrophysics of galactic nuclei, in general. Although it is well known that this is a very hostile environment due to the presence of tens ofWolf-Rayet (WR) stars with strong outflows, the recent detection of cold gas (-104 K) has challenged our understanding of the gas dynamics and thermodynamics of the region. The so-called G2 source, the dusty sources in the IRS 13E cluster, as well as the disc-like structure in the immediate vicinity of Sgr A* are examples of such cold material. In this thesis, we present a detailed study of the formation of cold gas as a potential result of the collision of the many stellar winds, which are constantly taking place. The main aims of this study are: i) testing the hypothesis of G2 being a gaseous clump formed in a massive binary system, ii) constraining the initial properties and final fate of clumps formed in unstable wind interactions, iii) establishing whether it is possible or not for the system of WR stars orbiting Sgr A* to reach and remain in a steady state between the supplying and inflowing/outflowing material. We find that the properties and dynamics of the clumps produced in the known massive binaries are not consistent with G2’s, ruling out this hypothesis. Additionally, we perform adaptive-mesh refinement hydrodynamical simulations of idealised stellar wind collisions in order to characterise the clump formation process. The results show that clumps formed through thin-shell instabilities are not massive enough to impact significantly the state of the material enclosed within the inner parsec. Finally, the simulation of the complete system of WR stars orbiting Sgr A* shows that the natural outcome of its long-term evolution is the accumulation of material at its centre. Thus, we speculate that the WR stars and their outflows could explain all the phenomenology related to the activity of Sgr A* inferred from observations without the need of invoking external agents.
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    Three-dimensional simulations of clump formation in stellar wind collisions
    (OUP, 2020) Calderón Espinoza, Diego Nicolás; Cuadra Stipetich, Jorge Rodrigo; Schartmann, M.; Burkert, A.; Prieto, J.; Russell, Christopher M. P.
    The inner parsec of our Galaxy contains tens of Wolf–Rayet stars whose powerful outflows are constantly interacting while filling the region with hot, diffuse plasma. Theoretical models have shown that, in some cases, the collision of stellar winds can generate cold, dense material in the form of clumps. However, their formation process and properties are not well understood yet. In this work, we present, for the first time, a statistical study of the clump formation process in unstable wind collisions. We study systems with dense outflows ( ∼10−5 M⊙ yr−1 ), wind speeds of 500– 1500 km s−1 , and stellar separations of ∼20– 200 au . We develop three-dimensional high-resolution hydrodynamical simulations of stellar wind collisions with the adaptive-mesh refinement grid-based code ramses. We aim at characterizing the initial properties of clumps that form through hydrodynamic instabilities, mostly via the non-linear thin-shell instability (NTSI). Our results confirm that more massive clumps are formed in systems whose winds are close to the transition between the radiative and adiabatic regimes. Increasing either the wind speed or the degree of asymmetry increases the dispersion of the clump mass and ejection speed distributions. Nevertheless, the most massive clumps are very light (∼10 −3 – 10−2 M⊕ ), about three orders of magnitude less massive than theoretical upper limits. Applying these results to the Galactic Centre, we find that clumps formed through the NTSI should not be heavy enough either to affect the thermodynamic state of the region or to survive for long enough to fall on to the central supermassive black hole.