Welcome to all new group members

15 Mar

Screen Shot 2015-04-14 at 6.45.29 PMWelcome to all new group members of the BinCosmos project group. If you are interested in applying for a postdoctoral fellowship and work with us (Marie Curie or Veni = Eu/Dutch “Hubble Fellowship equivalent”) please check the jobs page and contact me. For Dutch students who want to do BSc or MSc thesis project, please also contact me.

Searching for exoplanets at Palomar Observatory

14 Mar

Just spent a night at Mount Palomar Observatory at the 200 inch (5.1 meter) telescope.  Quite amazing that this mountain, just 2.5 hours from Los Angeles, is the location of the telescope, which used to be the most important telescope for about 4 decades until 1992.

I joined a team lead by Ben Oppenheimer (American Museum of National History) that build a special instrument that can not only detect planets (which is very challenging because it is sitting right next to a very bright star) but also get some information about the properties of the planet through its spectrum (which is even more challenging to get).  The museum made a very nice short video explaining how this works: “Seeing planets like never before”.

Unfortunately, the weather was not very good: it was clear, but the strong winds made the air too turbulent.   So, no new discoveries tonight, but for me a very useful and special experience.

New Paper: How many massive stars are product of a binary merger?

20 Jan

Incidence of mergers and other products among a typical population of massive stars.

A merger between two stars may sound like an exotic event, but for massive stars this is not rare at all.  About a quarter has a companion that is so close that the two stars will coalesce to form a new rejuvenated star (Sana, de Mink et al. Science 2012). In this paper we simulate the evolution of the stars and their interaction processes.  We predict the incidence of stellar mergers and other products of binary evolution among a typical stellar population. Furthermore we show that these products typically appear to be single stars.  Published in Astrophysical Journal, De Mink et al. (2014).

Most massive stars in young starclusters are binary products (new paper, ApJ in press)

13 Nov

Screen Shot 2014-12-07 at 6.14.17 PMSeventy percent of all O-stars is expected to interact with a binary companion during it’s life. The mass changes resulting from such interactions and stellar winds leave characteristic signatures in stellar mass function of young star clusters. Using these we model the mass functions of the Arches and Quintuplet cluster accounting for binary interaction and derive an age of 3.5+/-0.7 Myr and 4.8+/-0.1 Myr.  Based on our simulations, we expect the most massive 9+/-3 stars in Arches and 8+/-3 in Quintuplet to be the product of binary evolution. We propose this as a solution to the long standing age controversy for these clusters and we discuss the implications for the upper stellar mass limit


Globular clusters: Simple after all? (new paper accepted for MNRAS)

18 Sep

Screen Shot 2014-12-07 at 6.19.41 PMGlobular clusters are old compact systems containing up to a about a million of stars. How so many stars form in such a small area still remains unclear.  A particular puzzling feature is that effectively all globular cluster appear to harbor more than one stellar population within them.

In this paper we propose that a first generation of massive stars polluted their lower mass sisters while they were still fully convective PMS stars.  While details still need to be worked out, a very attractive feature of this scenario is that it provides a solution for the long standing mass budget problem.

Early Disc Accretion as the Origin of Abundance Anomalies in Globular Clusters“, by Bastian, Lamers, de Mink, Longmore, Goodwin & Gieles, 2013, MNRAS in press.