arXiv subjects

Inma Domínguez

Publications and source records attributed to Inma Domínguez.

8 recordsLinked to original sources

arXiv2026

The host galaxies of 2003fg-like type Ia supernovae

SN~2003fg-like events are a peculiar type Ia supernova (SN~Ia) subtype characterized by broader light curves, higher near-infrared luminosities, and stronger carbon absorptions at early times. Here we present observations of the largest compilation of 2003fg-like SN Ia host galaxies to date, obtained with Integral Field Spectroscopy (IFS). For 20 objects, we study both the global host-galaxy properties and, for the first time for a sizeable sample, the local environment at the SN position. Globally, 2003fg-like SNe~Ia occur in galaxies with lower stellar mass, lower oxygen abundance, and marginally higher specific star-formation rate (sSFR) than those of normal SNe~Ia, although their hosts are not as extreme in such properties as superluminous SNe, nor representative of metal-poor dwarf-galaxy samples. Locally, the SN positions show lower star-formation-rate, stellar-mass surface densities, and lower sSFR, than normal SN~Ia environments, consistent with a significant preference for the outskirts of their hosts, while their stellar age indicators are typical. The most distinctive local property is metallicity, with 2003fg-like SNe~Ia occupying the most metal-poor environments among SNe~Ia. We also find a tentative positive correlation between the light-curve width and the oxygen abundance for 2003fg-like events. Our results imply that 2003fg-like SNe~Ia arise from the merger of two white dwarfs (WDs) or the core-degenerate scenario, but disfavor the single, rapidly rotating super-M$_{ch}$ C-O WD progenitor, as this channel requires a young stellar population that we do not observe at the SN positions. The preference of 2003fg-like SNe~Ia for low-metallicity environments suggests that they may have been more common in the early Universe. (abridged)

astro-ph.CO↗

arXiv2026

s-process nucleosynthesis in low-mass AGB stars by the $^{13}$C($α$,n)$^{16}$O neutron source

In this review we outline our knowledge on slow neutron captures, concentrating on its main part occurring during the final stages of stellar evolution for low or intermediate-mass stars when they evolve during the Asymptotic Giant Branch, or AGB, stars. We focus our attention on how, in this field, studies passed from a first era of inquiries based on nuclear systematics, to numerical nucleosynthesis computations performed in stellar codes. We then discuss how these last were forced, by observational constraints, to almost abandon, for the synthesis of nuclei between Sr and Pb, the rather naturally activated Ne22 neutron source (operating efficiently at T > 30 keV, and producing a neutron density N_n > 5 10^8 cm^-3). This implied considering the alternative reaction 13C(alpha,n)16O, that can be activated locally after each of the TDU. The mentioned crucial reaction occurs at T< 8 keV, in the time intervals separating two subsequent thermal pulses (TP). The layers where 13C(alpha,n)16O operates are characterized by a radiative equilibrium and their low temperature also yields low values for the neutron density (N_n < 10^7 cm^-3).

astro-ph.SR↗

arXiv2022

Sub-stellar engulfment by a main sequence star: where is the lithium?

In this work, we study whether the engulfment of a brown dwarf (BD) by a solar-like main-sequence (MS) star can significantly alter the structure of the star and the Li content on its surface. We perform 3D Smoothed Particle Hydrodynamics simulations of the engulfment of a BD with masses 0.01 and 0.019 Msun, onto an MS star of 1 Msun and solar composition, in three different scenarios: a head-on collision, a grazing collision, and a merger. We study the dynamics of the interaction in detail, and the relevance of the type of interaction and the mass of the BD on the final fate of the sub-stellar object and the host star in terms of mass loss of the system, angular momentum transfer, and changes in the Li abundance in the surface of the host star. We found that most of the BD mass is diluted in the denser region of the MS star. Only in the merger scenario a significant fraction (40%) of the BD material would remain in the outer layers. We find a clear increase in the surface rotational velocity of the host star after the interaction, ranging between 25 km/s (grazing collision) to 50 km/s (merger). We also find a significant mass loss from the system (1e-4 - 1e-3 Msun) due to the engulfment, which in the case of the merger, may form a circumstellar disk-like structure. Assuming that neither the depth of the convective envelope of the host star nor its mass content are modified during the interaction, a small change in the surface Li abundance in the head-on and grazing collisions is found. However, in the merger we find large Li enhancements, by factors 20-30, depending on the BD mass. Some of these features could be detected observationally in the host star provide they remain long enough time.

astro-ph.SR↗

arXiv2022

Chandrasekhar-mass white dwarfs are the progenitors of a small fraction of Type Ia supernovae according to nucleosythesis constraints

The precise progenitor system of type Ia supernovae (SNe Ia), whether it is a white dwarf (WD) close to the Chandrasekhar limit or substantially less massive, has been a matter of debate for decades. Recent research by our group on the accretion and simmering phases preceding the explosion of a massive WD has shown that the central density at thermal runaway lies in the range $(3.6-6.3)\times10^9$ g cm$^{-3}$ for reasonable choices of accretion rate onto the WD and progenitor metallicity. In this work, we have computed one-dimensional simulations of the explosion of such WDs, with special emphasis on the chemical composition of the ejecta, which in all cases is extremely rich in neutronized isotopes of chromium ($^{54}$Cr) and titanium ($^{50}$Ti). We show that, in order to reconcile such a nucleosynthesis with the isotopic abundances of the Solar System, Chandrasekhar-mass white dwarfs can account for at most 26 per cent of normal-luminosity SNe Ia, or at most 20 per cent of all SNe Ia.

astro-ph.SR↗

arXiv2016

The puzzle of the CNO isotope ratios in AGB carbon stars

Previous determinations of the oxygen isotopic ratios in AGB carbon stars were at odds with the existing theoretical predictions. We aim to redetermine the oxygen ratios in these stars using new spectral analysis tools and further develop discussions on the carbon and nitrogen isotopic ratios in order to elucidate this problem. Oxygen isotopic ratios were derived from spectra in the K-band in a sample of galactic AGB carbon stars of different spectral types and near solar metallicity. Synthetic spectra calculated in LTE with spherical carbon-rich atmosphere models and updated molecular line lists were used. The CNO isotope ratios derived in a homogeneous way, were compared with theoretical predictions for low-mass (1.5-3 M_o) AGB stars computed with the FUNS code assuming extra mixing both during the RGB and AGB phases. For most of the stars the 16O/17O/18O ratios derived are in good agreement with theoretical predictions confirming that, for AGB stars, are established using the values reached after the FDU according to the initial stellar mass. This fact, as far as the oxygen isotopic ratios are concerned, leaves little space for the operation of any extra mixing mechanism during the AGB phase. Nevertheless, for a few stars with large 16O/17O/18O, the operation of such a mechanism might be required, although their observed 12C/13C and 14N/15N ratios would be difficult to reconcile within this scenario. Furthermore, J-type stars tend to have lower 16O/17O ratios than the normal carbon stars, as already indicated in previous studies. Excluding these peculiar stars, AGB carbon stars occupy the same region as pre-solar type I oxide grains in a 17O/16O vs. 18O/16O diagram, showing little spread. This reinforces the idea that these grains were probably formed in low-mass stars during the previous O-rich phases.

astro-ph.SR↗

arXiv2015

On the dependence of the type Ia SNe luminosities on the metallicity of their host galaxies

The metallicity of the progenitor system producing a type Ia supernova (SN Ia) could play a role in its maximum luminosity, as suggested by theoretical predictions. We present an observational study to investigate if such a relationship there exists. Using the 4.2m WHT we have obtained intermediate-resolution spectroscopy data of a sample of 28 local galaxies hosting SNe Ia, for which distances have been derived using methods independent to those based on the own SN Ia parameters. From the emission lines observed in their optical spectrum, we derived the gas-phase oxygen abundance in the region where each SN Ia exploded. Our data show a trend, with a 80% of chance not to be due to random fluctuation, between SNe Ia absolute magnitudes and the oxygen abundances of the host galaxies, in the sense that luminosities tend to be higher for galaxies with lower metallicities. This result seems like to be in agreement with both the theoretically expected behavior, and with other observational results. This dependence $M_{B}$-Z might induce to systematic errors when is not considered in deriving SNe Ia luminosities and then using them to derive cosmological distances.

astro-ph.GA↗

arXiv2011

Incomplete carbon-oxygen detonation in Type Ia supernovae

Incomplete carbon-oxygen detonation with reactions terminating after burning of 12C in the leading 12C + 12C reaction (C-detonation) may occur in the low density outer layers of white dwarfs exploding as Type Ia supernovae (SNIa). Previous studies of carbon-oxygen detonation structure and stability at low densities were performed under the assumption that the "velocity" of a detonation wave derives from complete burning of carbon and oxygen to iron. In fact, at densities <10^6 g/cm3 the detonation in SNIa may release less than a half of the available nuclear energy. In this paper we study basic properties of such detonations. We find that the length of an unsupported steady-state C-detonation is 30-100 times greater than previously estimated, and that the decreased energy has a drastic effect on the detonation stability. In contrast to complete detonations which are one-dimensionally stable, C-detonations may be one-dimensionally unstable and propagate by periodically re-igniting themselves via spontaneous burning. The re-ignition period at rho < 10^6 g/cm3 is estimated to be greater than the time-scale of a SNIa explosion. This suggests that propagation and quenching of C-detonations at these densities could be affected by the instability. Potential observational implications of this effect are discussed.

astro-ph.SR↗

arXiv1998

Type Ia Supernovae: Influence of the Progenitor on the Explosion

The influence of the initial composition and structure of the exploding white dwarf on the nucleosynthesis and structure of Type Ia Supernovae has been studied. The progenitor structures are based on detailed stellar evolutionary tracks for stars in the mass range between 1 to 9 $M_\odot$ using the state of the art code FRANEC. The calculations of the thermonuclear explosions are based on a set of delayed detonation models which give a good account of the optical and infrared light curves and of the spectral evolution. Our code solves the hydrodynamical equations explicitly by the piecewise parabolic method. Nuclear burning is taken into account using an extended network of 218 nuclei. In principle, our calculations allow the observed spectra and light curve to be linked to the progenitor. Moreover, our study is relevant to estimate potential evolution in the progenitor population at cosmological time scales.

astro-ph↗