Astrophysics Brown Bag Lunch Talk 11/1/2021 Speakers: Floor Broekgaarden (Harvard University) And Victoria Fawcett (Durham University)
Monday, November 1, 2021
12:00 – 12:30pm
Floor Broekgaarden, Harvard University
(What) Can we learn about Massive Stars from observations of Black Holes and Neutron Stars?
The population of observed NS/BH binaries from pulsar- and gravitational-wave surveys is rapidly growing. These detections carry valuable information about the properties of BHs and NSs, such as their rates, masses and spins, that we aim to use to probe the formation, lives and explosive deaths of massive stars throughout the Universe. However, uncertainties in the modeling of these sources are large, limiting such work. In this talk we will discuss – therefore the question: what can we really learn about massive stars from these BH/NS binaries?
Bio: Floor completed her BSc in Mathematics and Physics and her MSc in Astronomy at the University of Amsterdam. After doing a few short research internships in Birmingham, Edinburg and Monash she joined Harvard in 2019 as a PhD student in Astronomy where she is co-developing the binary population synthesis code COMPAS. She is currently in her third year working on gravitational wave sources in LIGO, LISA and the CE, binary evolution, black holes, neutron stars and astro-statistics. Besides her research she is also actively involved in several initiatives for early-career astronomers.
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12:30 – 1:00pm
Abstract: An important fraction of quasars are red at optical wavelengths, indicating (in the vast majority of cases) that the accretion disc is obscured by a column of dust which extinguishes the shorter-wavelength blue emission. In recent work by our group, we have shown fundamental differences in the radio properties of SDSS optically selected red quasars, which cannot be explained with a simple viewing angle hypothesis (Klindt et al. 2019, Fawcett et al. 2020, Rosario et al. 2020, Rosario et al. 2021). In our latest work, we use VLT/X-shooter spectroscopy of a sample of red and typical quasars to gain insight into these differences. We confirm that dust reddening is the main cause of the red colours and explore the emission line properties of our sample. We confront our spectra against accretion disc models and confirm that red quasars are powered by standard thin-disc accretion once corrected for dust extinction. These results suggest that dusty winds could be driving the fundamental differences in red quasars, and so they may represent an important phase in galaxy evolution. Using DESI spectra, we can now push to more extinguished, lower luminosity systems, which will test whether these results extend to more extreme reddened systems.
Speakers
- Floor Broekgaarden, Harvard University
- Victoria Fawcett, Durham University