arXiv subjects

J. B. Rodríguez-González

Publications and source records attributed to J. B. Rodríguez-González.

9 recordsLinked to original sources

arXiv2026

Formation and Evolution of [Wolf-Rayet] Planetary Nebulae through a Late Thermal Pulse

We present the first radiation-hydrodynamical simulations of the formation of a born-again planetary nebula (PN) triggered by a late thermal pulse (LTP). The 2D radiation-hydrodynamic simulations, performed with the {\sc pluto} code, have been consistently coupled to stellar evolution calculations using the Modules for Experiments in Stellar Astrophysics ({\sc mesa}) code. Very particularly the stellar evolution model uses (i) updated opacity tables for H-deficient, C-rich mixtures during the LTP, and (ii) a mass-loss prescription tailored for H-deficient [Wolf-Rayet]([WR])-type winds during the post-LTP phase. Our stellar model reproduces the nearly complete depletion of H expected after an LTP event, while matching the observed abundances and spectral types of iconic [WR]-type central stars of PNe. The simulations show for the first time that the H-deficient LTP ejecta forms a transient double-shell structure which, after $\sim$1000 yr, becomes fully mixed with the H-rich PN. The ejecta mass ($\sim3.4\times10^{-4}$~M$_\odot$) is too small to leave a lasting imprint on the nebular abundances, predicting H-rich PNe around [WR] central stars. The injection of LTP material into the hot bubble drives turbulence, clump formation, and enhanced mixing, providing an explanation to the larger expansion velocities and larger turbulent nebular structures of PNe with [WR] central stars compared to those with H-rich central stars. These results provide robust support for the born-again scenario as the origin of H-deficient [WR] central stars within H-rich PNe.

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arXiv2025

Entering the Wind Roche Lobe Overflow realm in Symbiotic Systems

We present a suite of dynamical simulations designed to explore the orbital and accretion properties of compact (2$-$7 AU) symbiotic systems, focusing on wind accretion, drag forces, and tidal interactions. Using three levels of physical complexity, we model systems of accreting white dwarfs (WDs) with masses of 0.7, 1.0, and 1.2 M$_\odot$ orbiting evolving Solar-like stars with 1, 2, and 3 M$_\odot$. We show that systems alternate between standard wind accretion and Wind Roche Lobe Overflow (WRLO) regimes during periods of high mass-loss rate experienced by the donor star (the peak of red giant phase and/or thermal pulses). For some configurations, the standard wind accretion has mass accretion efficiencies similar to those obtained by WRLO regime. Tidal forces play a key role in compact systems, leading to orbital shrinkage and enhanced accretion efficiency. We find that systems with high-mass WDs ($\geq 1$ M$_\odot$) and massive donors (2$-$3 M$_\odot$) are the only ones to reach the Chandrasekhar limit. Interestingly, the majority of our simulations reach the Roche lobe overflow condition that is not further simulated given the need of more complex hydrodynamical simulations. Our analysis shows that increasing physical realism, by including drag and tides, systematically leads to more compact final orbital configurations. Comparison with compact known symbiotic systems seems to suggest that they are very likely experiencing orbital decay produced by tidal forces.

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arXiv2025

The impact of wind accretion in Evolving Symbiotic Systems

We investigate the impact of geometric corrections to the Bondi-Hoyle-Lyttleton (BHL) accretion scheme applied to evolving symbiotic systems. We model systems where 0.7 and 1 M$_\odot$ white dwarfs accrete material from Solar-like stars with initial masses of 1, 2, and 3 M$_\odot$. The primary star is evolved using the MESA stellar evolution code, while the orbital dynamics of the system are calculated using REBOUND. The analysis focuses on systems evolving through the red giant branch and the thermally-pulsating asymptotic giant branch phases that do not experience a Wind Roche Lobe Overflow phase. We compare three scenarios: no accretion, standard BHL accretion, and the improved wind accretion. The choice of accretion prescription critically influences the evolution of symbiotic systems. Simulations using the modified model did not reach the Chandrasekhar limit, suggesting that type Ia supernova progenitors require accretors originating from ultra-massive WDs. In contrast, the standard BHL model predicts WD growth to this limit in compact systems. This discrepancy suggests that population synthesis studies adopting the traditional BHL approach may yield inaccurate results. The revised model successfully reproduces the accretion properties of observed symbiotic systems and predicts transitions between different accretion regimes driven by donor mass-loss variability. These results emphasize the need for updated wind accretion models to accurately describe the evolution of symbiotic binaries.

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arXiv2024

Y Gem, a symbiotic star outshone by its asymptotic giant branch primary component

A considerable number of asymptotic giant branch (AGB) stars exhibit UV excess and/or X-ray emission that indicates a binary companion. AGB stars are so bright that they easily outshine their companions. This almost prevents their identification. Y Gem has been known for some decades to be an AGB star that is bright in the far-UV and X-rays, but it is unclear whether its companion is a main-sequence star or a white dwarf (WD) in a symbiotic system (SySt). Our goal is to uncover the true nature of Y Gem, which will help us to study the possible misidentified population of SySts. Multiwavelength IR, optical, UV, and X-ray observations were analyzed to investigate the properties of the stellar components and the accretion process in Y Gem. In particular, an optical spectrum of Y Gem is presented here for the first time, while X-ray data are interpreted by means of reflection models produced by an accretion disk and material in its vicinity. The optical spectrum exhibits the typical sawtooth-shaped features of molecular absorptions in addition to narrow recombination and forbidden emission lines. The emission lines and the analysis of the extinction-corrected UV spectrum suggest a hot component with $T_\mathrm{eff}\approx$60,000 K, $L$=140 L$_{\odot}$, and $R$=0.11 R$_{\odot}$ that very likely is an accreting WD. The late component is found to be an 1.1 M$_\odot$ AGB star with $T_\mathrm{eff}$=3350 K and $R$=240 R$_\odot$. Using IR, optical, UV, and X-ray data, we found that Y Gem is an S-type SySt whose compact component is accreting at an estimated mass-accretion rate of $\dot{M}_\mathrm{acc}=2.3\times10^{-7}$ M$_\odot$ yr$^{-1}$. At this accretion rate, the accreting WD has reached the stable and steady burning phase in which no recurrent events are expected.

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arXiv2022

Adjusting the bow-tie: A morpho-kinematic study of NGC40

We present a comprehensive study of the ionization structure and kinematics of the planetary nebula (PN) NGC40 (a.k.a. the Bow-tie Nebula). A set of narrow-band images obtained with the ALhambra Faint Object Spectrograph and Camera (ALFOSC) at the Nordic Optical Telescope (NOT) are used to study the turbulent distribution of gas in the main cavity, the ionization stratification and the density of this PN. High-resolution Manchester Echelle Spectrograph (MES) observations obtained at 2.1m telescope of the San Pedro Mártir (SPM) Observatory are used to unveil in great detail the kinematic signatures of all morphological features in NGC40. The images and spectra suggest that NGC40 had multiple mass ejections in its recent formation history. We found 4 jet-like ejections not aligned with the main axis of NGC40 (PA=20$^{\circ}$), some of them having pierced the main cavity along the SW-NE direction as well as the southern lobe. Using a tailor-made morpho-kinematic model of NGC40 produced with SHAPE we found that the main cavity has a kinematic age of 6,500 yr and the two pairs of lobes expanding towards the N and S directions have an averaged age of 4,100$\pm$550 yr. NGC40 thus adds to the group of PNe with multiple ejections along different axes that challenge the models of PN formation.

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arXiv2022

Common envelope evolution in born-again planetary nebulae -- Shaping the H-deficient ejecta of A30

Born-again planetary nebulae (PNe) are extremely rare cases in the evolution of solar-like stars. It is commonly accepted that their central stars (CSPN) experienced a very late thermal pulse (VLTP), ejecting H-deficient material inside the evolved H-rich PN. Given the short duration of this event and the fast subsequent evolution of the CSPN, details of the mass ejection are unknown. We present the first morpho-kinematic model of the H-deficient material surrounding a born-again PN, namely A30. New San Pedro Mártir observations with the Manchester Echelle Spectrograph were recently obtained to map the inner region of A30 which are interpreted by means of the software SHAPE in conjunction with HST WFC3 images. The SHAPE morpho-kinematic model that best reproduces the observations is composed by a disrupted disk tilted $37^\circ$ with respect to the line of sight and a pair of orthogonal opposite bipolar ejections. We confirm previous suggestions that the structures closer to the CSPN present the highest expansion velocities, that is, the disrupted disk expands faster than the farther bipolar features. We propose that the current physical structure and abundance discrepancy of the H-deficient clumps around the CSPN of A30 can be explained by a common envelope phase following the VLTP event. Our proposed scenario is also compared with other known born-again PNe (A58, A78, HuBi1 and the Sakurai's Object).

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arXiv2022

Rings and arcs around evolved stars -- III. Physical conditions of the ring-like structures in the planetary nebula IC 4406 revealed by MUSE

We present the analysis of Very Large Telescope (VLT) Multi Unit Spectroscopic Explorer (MUSE) observations of the planetary nebula (PN) IC 4406. MUSE images in key emission lines are used to unveil the presence of at least 5 ring-like structures North and South of the main nebula of IC 4406. MUSE spectra are extracted from the rings to unambiguously assess for the first time in a PN their physical conditions, electron density (ne) and temperature (Te). The rings are found to have similar Te than the rim of the main nebula, but smaller ne. Ratios between different ionic species suggest that the rings of IC 4406 have a lower ionization state than the main cavity, in contrast to what was suggested for the rings in NGC6543, the Cat's Eye Nebula.

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arXiv2021

Carbon dust in the evolved born-again planetary nebulae A30 and A78

We present an infrared (IR) characterization of the born-again planetary nebulae (PNe) A30 and A78 using IR images and spectra. We demonstrate that the carbon-rich dust in A30 and A78 is spatially coincident with the H-poor ejecta and coexists with hot X-ray-emitting gas up to distances of 50$''$ from the central stars (CSPNs). Dust forms immediately after the born-again event and survives for 1000 yr in the harsh environment around the CSPN as it is destroyed and pushed away by radiation pressure and dragged by hydrodynamical effects. Spitzer IRS spectral maps showed that the broad spectral features at 6.4 and 8.0 $μ$m, attributed to amorphous carbon formed in H-deficient environments, are associated with the disrupted disk around their CSPN, providing an optimal environment for charge exchange reactions with the stellar wind that produces the soft X-ray emission of these sources. Nebular and dust properties are modeled for A30 with Cloudy taking into account different carbonaceous dust species. Our models predict dust temperatures in the 40-230 K range, five times lower than predicted by previous works. Gas and dust masses for the born-again ejecta in A30 are estimated to be $M_\mathrm{gas}=(4.41^{+0.55}_{-0.14})\times10^{-3}$ M$_\odot$ and $M_\mathrm{dust}=(3.20^{+3.21}_{-2.06})\times10^{-3}$ M$_\odot$, which can be used to estimate a total ejected mass and mass-loss rate for the born-again event of $(7.61^{+3.76}_{-2.20})\times10^{-3}$ M$_{\odot}$ and $\dot{M}=[5-60]\times10^{-5}$ M$_{\odot}$ yr$^{-1}$, respectively. Taking into account the carbon trapped into dust grains, we estimate that the C/O mass ratio of the H-poor ejecta of A30 is larger than 1, which favors the very late thermal pulse model over the alternate hypothesis of a nova-like event.

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arXiv2020

Detailed studies of IPHAS sources -- III. The highly extinguished bipolar planetary nebula IPHASX J191104.8$+$060845

We present the first detailed study of the bipolar planetary nebula (PN) IPHASX J191104.8$+$060845 (PN G040.6$-$01.5) discovered as part of the Isaac Newton Telescope Photometric H$α$ Survey of the Northern Galactic plane (IPHAS). We present Nordic Optical Telescope (NOT) narrow-band images to unveil its true morphology. This PN consists of a main cavity with two newly uncovered extended low-surface brightness lobes located towards the NW and SE directions. Using near-IR WISE images we unveiled the presence of a barrel like structure, which surrounds the main cavity, which would explain the dark lane towards the equatorial regions. We also use Gran Telescopio de Canarias (GTC) spectra to study the physical properties of this PN. We emphasise the potential of old PNe detected in IPHAS to study the final stages of the evolution of the circumstellar medium around solar-like stars.

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