Gravitational-wave (GW) detections are now starting to probe the mass distribution of stellar-mass black holes (BHs). We investigate the predicted gap in the BH mass distribution and find that the location of the lower edge of the gap, at 45 solar masses, is remarkably robust against model assumptions and composition variations, making it the most robust predictions for the final stages of massive star evolution we have. We do find a dependency on the reaction rates, which implies that GW detections will constrain nuclear astrophysics. The robustness implies that there is a universal maximum for the location of the lower edge of the gap insensitive to the formation environment and redshift for first-generation BHs. This is promising for the possibility to use the location of the gap as a “standard siren” across the Universe.
Farmer, Renzo, de Mink et al. (2019, ApJ in press)
Rob Farmer, the lead other, is a postdoc in my group in Amsterdam and is a visiting scientist at Harvard University.
Former Ph.D. student Ylva Götberg (now Nashman theory fellow at Carnegie observatories) estimated the relative contribution of massive stars, stars stripped in binaries and active galactic nuclei to the epoch of reionization. We estimate that stripped stars contributed tens of percent of the photons that caused cosmic reionization of hydrogen, depending on the assumed escape fractions. More importantly, stripped stars harden the ionizing emission. At high redshift, stripped stars and massive single stars combined dominate the He II-ionizing emission, but we still expect active galactic nuclei drive cosmic helium reionization.
Götberg, de Mink, Mcquinn et al. (2019, A&A in press)
From Birth to Chirp – Astrophysics of Massive Stars as Gravitational Wave Progenitors.
Abstract: How did they form?’ is a question many asked when LIGO announced the first direct detection of gravitational waves originating from two surprisingly heavy stellar-mass black holes. With masses of about 30 solar masses each, they outweighed all of the known black holes known from X-ray binaries. Now, four years after the first detection, alerts of new triggers come in at a rate of almost one per week. The analysis of the first eleven events has been published and we learned that the first system was not exceptional: the majority of detected events involve heavy black holes. In parallel, classical telescopes have been revolutionizing our understanding of the properties of young massive stars.Continue reading
Time for an update with all new faces of our cross Atlantic group. In (crimson) red all those that are Harvard based and in orange all those that are in Amsterdam.
Ylva Götberg’s third thesis paper has accepted for publication A&A. In this paper, we present predictions for the integrated spectra of stellar populations including the hard ionizing photons expected from hot stars that have lost their envelope through interaction with a binary companion. The SED’s will be made available through the STARBURST99 portal. https://arxiv.org/abs/1908.06102
August 1, 2019, I started at Harvard University. I keep being affiliated with the University of Amsterdam. Incredibly excited to start a new (transatlantic) group.
Manos Zapartas is a very recent BinCosmos PhD graduate, who only left our group a few months ago for Geneva observatory. We are very excited to share that he has been awarded the competitive Swiss Government Excellence Fellowship. This allows him to pursue his research on the final fate of massive binary stars. He will do so as a member of the group of dr. Tassos Fragos, who recently joined Geneva Observatories last year as an assistant professor.
Group member Athira Menon, postdoc in the BinCosmos group, won the Dutch final of FameLab on 9 May. FameLab is a pitch competition for young researchers, in which they have only three minutes to explain their research to the general public. By winning the national final, she won a trip to Cheltenham, England, to compete at the annual Cheltenham Science Festival (June 4-9) against 24 other FameLab winners from around the world.