Group Members


The new Compact Objects Group in Leiden is composed by young scientists mainly funded by an NWO Vidi Fellowship.


Alessandro Patruno: I am the principal investigator of the project and new members are currently joining to expand the group. I am a high energy astrophysicist interested in compact objects (primarily neutron stars but also white dwarfs and black holes). My main field of research are accreting millisecond X-ray pulsars and accreting neutron stars. You can see my biography and research interests by exploring this website.


Caroline D’Angelo, Postdoc: Caroline D’Angelo’s research focuses on understanding why stars with very strong magnetic fields (like neutron stars) look the way they do in the night sky. She is especially interested in understanding how gas falling onto the star will interact with the star’s magnetic field, which can lead to all kinds of interesting effects, such as large changes in the star’s brightness and spin rate, and even a complete burial of the magnetic field. Born in Toronto, Canada, she did her Bachelor’s Degree (2004) and Master’s Degree (2006) in Physics and Astronomy, where she worked with Marten van Kerkwijk, Yuri Levin and Roman Rafikov. She then moved to Munich, Germany, to do her PhD at the Max Planck Institute for Astrophysics under the supervision of Henk Spruit, which she finished in 2011. Continuing her European adventure, in 2011 she moved to Amsterdam, Netherlands, to work with Anna Watts for a three-year post-doc and is excited to stay in the Netherlands for another three years in Leiden.

Ann-SofieAnn-Sofie Bak Nielsen, Ph.D. student: Ann-Sofie Bak Nielsen studied at Dark Cosmology Centre at the University of Copenhagen. She obtained her Bachelors degree in 2012 on the subject of evolution and abundance of dust in the Milky Way and was supervised by Anja C. Andersen. For her master thesis she examined dust formation in type IIn supernova, supervised by Jens Hjorth. She has started her PhD in Leiden on September 2014. Her research field is accreting neutron stars and slowly rotating accreting pulsars with strong magnetic fields.

magdaotMagdalena Otulakowska Hypka, Postdoc:  Magdalena Otulakowska-Hypka is interested in all kinds of close and interacting binary systems, especially in accreting white dwarfs. Her research interests include dwarf novae, classical novae, and symbiotic stars, as well as observational techniques. She did her Master’s Degree (2008) at A. Mickiewicz University in Poznan, Poland, and at Max Planck Institute for Radioastronomy in Bonn, Germany, in the group of Prof. Gerd Weigelt. Then, she did her PhD (2014) at N. Copernicus Astronomical Center in Warsaw, Poland, under the supervision of Arkadiusz Olech. During that time she worked also with Prof. Joanna Mikołajewska (N. Copernicus Astronomical Center), Prof. Olivier Chesneau (Observatoire de la Côte d’Azur), and Prof. Joe Patterson (Columbia University). After a maternity break for her beautiful baby boy, she’s back to science now at Leiden Observatory.

algeraHiddo Algera, M.Sc. student (now PhD student):  I obtained my Bachelor’s degree in Astronomy at Leiden University in 2015, with a research project focused on characterizing the ring structure of the protoplanetary disk HL Tau by modelling its visibilities, under supervision of Dr. Michiel Hogerheijde. My main research interests are in the fields of high-energy astrophysics and cosmology and currently I’m doing research on accreting millisecond neutron stars, specifically on the phenomenon of intermittent X-ray pulsations.


Ph.D. Students

  • Peter Bult (UvA, now NASA fellow at Goddard Space Flight Center) (PhD thesis)

Master Students


Bachelor Students

  • Erik de Bok (UvA, now Master student at the UvA)
  • Mathijs Elbers (UvA) (Bachelor thesis)
  • Chao Kang Tai (UvA, now Master student at the Utrecht University)
  • Ortwin Spaargaren (UvA)

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