ERC STAREX

Plot of the Week

October 2, 2020

The structure of an accreting supermassive star

AccretingSMS_structure.png

Internal structure of an accreting supermassive star until it reaches 105 solar masses. The black solid and dashed lines represent the radial positions of the stellar surface and mass coordinates enclosing 80%, 60%, 40%, and 20% of the total mass in descending order. The white and yellow areas represent radiative and convective zones where no nuclear fusion takes place. The brown stripe and pink zones indicate the radiative and convective layers where deuterium burning occurs. The green area represents a convective core where hydrogen burning occurs.
Article: Haemmerlé et al. (2020)

June 10, 2020

How to build a star as an IKEA library from different elements?

SNAPSHOT.png

Schematic outline of the construction of snapshot stellar structure models with different core compositions, core masses and envelope masses. We first select a core composition (1A). Secondly, we select a core mass to go with this core composition (1B). Finally, we select an envelope mass (1C). Using a stellar evolution code, the models are allowed to relax to a state of hydrostatic and thermal equilibrium (2). The final stellar model produces both the surface properties, e.g. luminosity and effective temperature, as well as the interior profiles of the standard quantities, e.g. temperature, luminosity, and density (3).
Article: Farrell et al. (2020)

May 29, 2020:

Can the problem of missing young O stars be explained by the process of massive star formation?

YoungO_200529.png

Location of 285 likely single and SB1 Galactic O-type stars in the spectroscopic HR diagram. Crosses indicate stars for which we detected clear or likely signatures of spectroscopic binarity. Open symbols, triangles, and squares are stars for which only an upper or lower limit in any (triangles) or both (squares) of the two parameters used to construct these diagrams could be obtained (Teff and logg). Individual uncertainties are included as error bars. Evolutionary tracks and position of the ZAMS (thick solid line) from the nonrotating solar metallicity models by Ekström et al. (2012) and Georgy et al. (2013) are included for reference. Additional evolutionary tracks of pre-Main-Sequence models evolving at mass accretion of 10-5 solar masses per year is shown by a green line. The red track corresponds to the model in which the accretion rate is changed from 10-5 to 10-4 solar mass per year when the accumulated mass reaches 25 solar masses.
Article: Holgado et al. (2020)

May 20, 2020:

3D convective boundary shape

Representation of the shape of the boundary between a convective region (below) and a stably stratified region (on top). The definition of the boundary used is based here on the chemical composition : the blue region shows the surface where the mean molecular weight is the one inside the convective zone minus one tenth of the difference between the convective zone and the top of the domain.

Simulation run with the Prompi code (Meakin & Arnett, 2007, ApJ 667 448), at the Barcelona Supercomputing Center.

Visualisation made with VisIt.