Preprint: Pulsational pair-instability supernovae in very close binaries

4 Jan

Anticipating new gravitational wave detections of heavy binary black holes, Pablo Marchant (CIERA) together with Bincosmos group members Mathieu Renzo and Rob Farmer’s explore the effects of pulsations experienced by the most massive stars. Find a preview here.

“Pulsational pair-instability supernovae in very close binaries” by Pablo Marchant, Mathieu Renzo,Robert Farmer, Kaliroe M. W. Pappas, Ronald E. Taam, Selma de Mink, and Vassiliki Kalogera.

Gaia & HST astrometry of a very massive ˜150 M⊙ candidate runaway star

1 Jan

A 150 Msun candidate runaway star.

Mathieu Renzo’s investigation of what is probably the most massive runaway star currently known. Using Gaia and Hubble Space Telescope data he tries to determine the origin of this extreme star, which has likely been ejected by the very young star cluster R136. The cluster is famous for harboring several of these monster stars as shown in earlier work. Now published in MNRAS.

Floor Broekgaarden, David Hendriks and Karel Temmink ready to start their PHD studies

12 Dec

Three BinCosmos students obtained their MSc degree today. Floor Broekgaarden (who will continue her PhD studies at Harvard), David Hendriks (who will move to Surrey to work with Rob Izzard) and Karel Temmink (who will move to Nijmegen to work with Onno Pols). Floor was also awarded the shared prize for the best thesis and the second prize for the best student colloquium and obtained her degree cum laude.

Dr. Zapartas thesis defense

10 Dec
Manos Zapartas and proud group members after Manos’ successful defense of his PhD
thesis on the impact of binarity on the statistical properties of core collapse
supernovae. He will be continuing as a postdoc in Geneva in the group of Tassos Fragos.

Unifying Subdwarfs and Wolf-Rayet stars as a sequence of stripped-envelope stars

12 Feb

Ylva Götberg’s second paper on the spectra of the stripped stars stripped is now accepted, featuring “obese subdwarfs”, “underweight Wolf-Rayet stars” and everything in between, including a demonstration of why astronomers are effectively colorblind, making these stars nearly invisible to us when they have a companion.

Y. GötbergS. E. de MinkJ. H. GrohT. KupferP. A. CrowtherE. ZapartasM. Renzo (2018) “Spectral models for binary products: Unifying Subdwarfs and Wolf-Rayet stars as a sequence of stripped-envelope stars”,  accepted for publication in Astronomy and Astrophysics, preprint available here https://arxiv.org/abs/1802.03018. 

On the overluminous hot subdwarf in the Phi Persei binary

7 Feb

Credit: ESA/Hubble

Image result for abel schootemeijerAbel Schootemeijer‘s MSc thesis paper got accepted, co-supervised by Ylva Götberg and @Manos Zapartas.

Abel investigated the binary system ϕ Persei, using new data by Douglas Gies and collaborators. The system contains one star, a subdwarf, with about the same mass as the Sun, but it is 10 times hotter and nearly 10,000 times brighter. It contains a second star, a Be star, that is nearly 10 times as massive as the Sun, which is spinning very rapidly. It is thought that the hot star is the remaining core of a star that has lost its envelope, transferring part of it to the companion which is now spinning very fast.

A. SchootemeijerY. GotbergS. E. de MinkD. R. GiesE. Zapartas, Clues about the scarcity of stripped-envelope stars from the evolutionary state of the sdO+Be binary system phi Persei, accepted for publication in A&A, 2018  https://arxiv.org/abs/1803.02379 Continue reading

Paper in Science: Excess of Massive Stars in the Tarantula Nebula

4 Jan

Obesitas in heelal: aantal sterren met overgewicht veel groter dan gedacht

Published in Science  05 Jan 2018, “The number of stars that form at each mass is known as the initial mass function (IMF). For most masses, the IMF follows a power-law distribution, first determined by Edwin Salpeter in 1955. Fabian Schneider et al. used observations of the nearby star-forming region 30 Doradus (also known as the Tarantula Nebula) and combined these with stellar modeling to determine its IMF. They found more stars above 30 solar masses than predicted by the Salpeter distribution. Because the most massive stars also have the biggest influence on their surroundings—for instance, through ultraviolet radiation, stellar winds, supernova explosions, and production of heavy elements—this excess will have wide-ranging implications. ” Editor summary in journal science.

Press coverage: Cosmos magazine by Richard A Lovett
Dutch Press interviewing Dutch Coauthors: Volkskrant by Govert Schilling.