Search results for "Red supergiant"
showing 10 items of 10 documents
Matter Mixing in Aspherical Core-collapse Supernovae: Three-dimensional Simulations with Single Star and Binary Merger Progenitor Models for SN 1987A
2019
We perform three-dimensional hydrodynamic simulations of aspherical core-collapse supernovae focusing on the matter mixing in SN 1987A. The impacts of four progenitor (pre-supernova) models and parameterized aspherical explosions are investigated. The four pre-supernova models include a blue supergiant (BSG) model based on a slow merger scenario developed recently for the progenitor of SN 1987A (Urushibata et al. 2018). The others are a BSG model based on a single star evolution and two red supergiant (RSG) models. Among the investigated explosion (simulation) models, a model with the binary merger progenitor model and with an asymmetric bipolar-like explosion, which invokes a jetlike explo…
What causes the large extensions of red-supergiant atmospheres? Comparisons of interferometric observations with 1-D hydrostatic, 3-D convection, and…
2015
We present the atmospheric structure and the fundamental parameters of three red supergiants, increasing the sample of RSGs observed by near-infrared spectro-interferometry. Additionally, we test possible mechanisms that may explain the large observed atmospheric extensions of RSGs. We carried out spectro-interferometric observations of 3 RSGs in the near-infrared K-band with the VLTI/AMBER instrument at medium spectral resolution. To comprehend the extended atmospheres, we compared our observational results to predictions by available hydrostatic PHOENIX, available 3-D convection, and new 1-D self-excited pulsation models of RSGs. Our near-infrared flux spectra are well reproduced by the P…
VLTI/AMBER spectro-interferometry of the late-type supergiants V766 Cen (=HR 5171 A), σ Oph, BM Sco, and HD 206859
2017
Aims. We add four warmer late-type supergiants to our previous spectro-interferometric studies of red giants and supergiants. Methods. We measure the near-continuum angular diameter, derive fundamental parameters, discuss the evolutionary stage, and study extended atmospheric atomic and molecular layers. Results. V766 Cen (=HR 5171 A) is found to be a high-luminosity (log L/L = 5.8 ± 0.4) source of effective temperature 4290 ± 760 K and radius 1490 ± 540 R, located in the Hertzsprung-Russell (HR) diagram close to both the Hayashi limit and Eddington limit; this source is consistent with a 40 M evolutionary track without rotation and current mass 27-36 M. V766 Cen exhibits Na i in emission a…
The infancy of core-collapse supernova remnants
2020
We present 3D hydrodynamic simulations of neutrino-driven supernovae (SNe) with the PROMETHEUS-HOTB code, evolving the asymmetrically expanding ejecta from shock breakout until they reach the homologous expansion phase after roughly one year. Our calculations continue the simulations for two red supergiant (RSG) and two blue supergiant (BSG) progenitors by Wongwathanarat et al., who investigated the growth of explosion asymmetries produced by hydrodynamic instabilities during the first second of the explosion and their later fragmentation by Rayleigh-Taylor instabilities. We focus on the late time acceleration and inflation of the ejecta caused by the heating due to the radioactive decay of…
The atmospheric structure and fundamental parameters of Red Supergiants
2013
We present studies of the atmospheric structure and fundamental properties of the red supergiants (RSGs) VY CMa, AH Sco, UY Sct, and KW Sgr based on near-infrared K -band interferometry obtained with the VLTI/AMBER instrument with a spectral resolution of 1500. In our visibility data, we observe the presence of molecular layers of water and CO in extended atmospheres. For a uniform disk modeling, we observe size increases in the water band centered at 1.9 μ m and in the CO band at 2.3–2.5 μ m, with respect to the near-continuum bandpass (2.20–2.25 μ m). With our spectral resolution, we obtain diameters in the near-continuum, that are free from contamination by molecular layers. Using PHOENI…
Fundamental properties and atmospheric structure of the red supergiant VY CMa based on VLTI/AMBER spectro-interferometry
2012
We investigate the atmospheric structure and fundamental properties of the red supergiant VY CMa. We obtained near-infrared spectro-interferometric observations of VY CMa with spectral resolutions of 35 and 1500 using the AMBER instrument at the VLTI. The visibility data indicate the presence of molecular layers of water vapor and CO in the extended atmosphere with an asymmetric morphology. The uniform disk diameter in the water band around 2.0 mu is increased by \sim20% compared to the near-continuum bandpass at 2.20-2.25 mu and in the CO band at 2.3-2.5 mu it is increased by up to \sim50%. The closure phases indicate relatively small deviations from point symmetry close to the photospheri…
VLTI-PIONIER imaging of the red supergiant V602 Carinae
2020
Context. Red supergiant stars possess surface features and extended molecular atmospheres. Photospheric convection may be a crucial factor of the levitation of the outer atmospheric layers. However, the mechanism responsible is still poorly understood. Aims. We image the stellar surface of V602 Carinae (V602 Car) to constrain the morphology and contrast of the surface features and of the extended atmospheric layers. Methods. We observed V602 Car with the Very Large Telescope Interferometer (VLTI) PIONIER instrument (1.53-1.78 $\mathrm{\mu}$m) between May and July 2016, and April and July 2019 with different telescope configurations. We compared the image reconstructions with 81 temporal sna…
Three-dimensional modeling from the onset of the SN to the full-fledged SNR. Role of an initial ejecta anisotropy on matter mixing
2020
Context. The manifold phases in the evolution of a core-collapse (CC) supernova (SN) play an important role in determining the physical properties and morphology of the resulting supernova remnant (SNR). Thus, the complex morphology of SNRs is expected to reflect possible asymmetries and structures developed during and soon after the SN explosion. Aims. The aim of this work is to bridge the gap between CC SNe and their remnants by investigating how post-explosion anisotropies in the ejecta influence the structure and chemical properties of the remnant at later times. Methods. We performed three-dimensional magneto-hydrodynamical simulations starting soon after the SN event and following the…
Multi-epoch VLTI-PIONIER imaging of the supergiant V766 Cen
2017
Context. The star V766 Cen (=HR 5171A) was originally classified as a yellow hypergiant but lately found to more likely be a 27-36 M red supergiant (RSG). Recent observations indicated a close eclipsing companion in the contact or common-envelope phase. Aims. Here, we aim at imaging observations of V766 Cen to confirm the presence of the close companion. Methods. We used near-infrared H-band aperture synthesis imaging at three epochs in 2014, 2016, and 2017, employing the PIONIER instrument at the Very Large Telescope Interferometer (VLTI). Results. The visibility data indicate a mean Rosseland angular diameter of 4.1 ± 0.8 mas, corresponding to a radius of 1575 ± 400 R. The data show an ex…
Near-infrarred spectro-interferometry of red giant and supergiant stars
2015
Las estrellas supergigantes rojas son estrellas frías y muy masivas que se encuentran en la fase previa a las estrellas Wolf-Rayet y a las supernovas. Presentan extensas atmósferas y fuertes vientos estelares que dan lugar a una importante pérdida de masa. El mecanismo que da lugar a estos vientos y a las extensas atmósferas es actualmente tema de debate. Además, la estimación de los parámetros fundamentales de este tipo de estrellas y su posterior localización en el diagrama HR es de gran importancia para calibrar los modelos de evolución estelar, y entender cómo la pérdida de masa afecta a su evolución. En esta tesis hemos estudiado una muestra representativa de estrellas supergigantes ro…