Found 7 talks width keyword subdwarfs

Planetary systems have been found systematically orbiting main sequence stars and red giants. But the detection of planets per se during the white dwarf phase has been more elusive with only 3 systems.  We have, however, ample indirect evidence  of the existence of planetary debris around these systems in the form of material acreted onto the white dwarf, disks and even planetesimals. In this talk, I will review how we can put the pieces together: how we can reconcile what we see in white dwarfs with what we can infer regarding the evolution of planetary systems from the main sequence phase.

Wide hot subdwarf B (sdB) binaries with main-sequence companions are outcomes of stable mass transfer from evolved red giants. The orbits of these binaries show a strong correlation between their orbital periods and mass ratios. The origins of this correlation have, so far, been lacking a conclusive explanation.
We have performed a small but statistically significant binary population synthesis study with the binary stellar evolution code MESA. We have used a standard model for binary mass loss and a standard Galactic metallicity history.  We have achieved an excellent match to the observed period - mass ratio correlation without explicitly fine-tuning any parameters. Furthermore, our models produce a good match to the observed period - metallicity correlation.
We demonstrate, for the first time, how the metallicity history of the Milky Way is imprinted in the properties of the observed post-mass transfer binaries. We show that Galactic chemical evolution is an important factor in binary population studies of interacting systems containing at least one evolved low-mass (Mi < 1.6 Msol) component. Finally, we provide an observationally supported model of mass transfer from low-mass red giants onto main-sequence stars.

Zoom link: https://rediris.zoom.us/j/98017007654

We report on the discovery of a fourth component in the HD 221356 star system, previously known to be formed by an F8V, slightly metal-poor primary ([Fe/H]= -0.26), and a distant M8V+L3V pair. In our ongoing common proper motion search based on VISTA Hemisphere Survey (VHS) and 2MASS catalogues, we have detected a faint (J = 13.76 ± 0.04 mag) co-moving companion of the F8 star located at a projected distance of ~312 AU. Near-infrared spectroscopy of the new companion indicates an L1±1 spectral type. Using evolutionary models the mass of the new companion is estimated at ~0.08 solar masses, which places the object close to the stellar-substellar borderline. This multiple system provides an interesting example of objects with masses slightly above and below the hydrogen burning mass limit.

The proper characterization of the least massive population of the young Sigma Orionis star cluster is required to understand the form of the cluster mass function and its impact on our comprehension of the substellar formation processes. SOri70 (T5.5±1) and SOri73, two T-type cluster member candidates, would have likely masses between 3 and 7 MJup if their age is 3 Myr. SOri73 awaits confirmation of its methane atmosphere. Here I present the results of a search of T-type objects in an area of ~120 arcmin^2 in the Sigma Orionis cluster, the confirmation of the presence of methane absorption in SOri73 and the study of SOri70 and 73 cluster membership via photometric colors and accurate proper motion analysis. This results would have a dramatic impact in the cluster mass function, in one of the scenarios explored, they suggest a decrease in cluster members with planetary masses in the interval 3.5-6 Mjup.