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PhD Defense Samayra Straal

Submitter: Joeri van Leeuwen
Description: Westerbork continues to be one of the most sensitive radio telescopes in the world, and as such it is an excellent training ground for our new astronomers. One of the most recent PhD students to finish their degree and earn the title of doctor is Samayra Straal from the University of Amsterdam.

On Dec 12 Samayra successfully defended her thesis "Young hidden pulsars" in the stately Aula, down town Amsterdam. The thesis is an impressively all-round book based on observations with LOFAR, EVN and Westerbork/Apertif. Using the EVN, Samayra concluded that high-energy source HESS J1943+213 is most likely a BL Lac object, rather than a pulsar wind nebula (PWN) (Straal et al. 2016, ApJ 822, 117). She explored (Ch. 3; Straal at al. 2019 in prep.) to what extent such pulsar wind nebulae, and supernova remnants (SNRs), impact pulsar signal propagation. We find a two-sigma DM excess to these sources; by extrapolating to the kind of fast-spinning, high magnetic-field, young pulsars that may power FRBs, Samayra shows that SNRs and PWNe around FRBs are capable of significantly contributing to the observed dispersion measure. Samayra led the search, using LOFAR and the national supercomputer Cartesius, for young, steep-spectrum pulsars in supernova remnants and pulsar wind nebulae (Straal & van Leeuwen 2019, A&A 623, 90), finding a pulsar candidate in PWN G141.2+5.0, and concluding that our non-detections towards the other point sources and PWNe are the result of beaming and propagation effects. Some of the remaining SNRs should host a black hole rather than a neutron star. Finally, in Chapter 5 Samayra reports on the flux calibration verification we carried out as part of the scientific commissioning of Apertif. Feel free to pick up your personal brightly colored copy of this thesis in Joeri's office.

Congratulations, Dr. Straal.
Copyright: Straal / Oostrum
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