Research

The common thread in my research interests can be summarized by the question: how can we push further our understanding of the laws of physics by probing the beautiful and complex laboratories that populate the sky above us? Astrophysical objects encompass a variety of extremes that cannot ever be achieved on Earth: of gravitation, energy, density, temperature, and magnetic field. For this reason, the discoveries in the sky in the past century have pushed forward our understanding as dramatically as discoveries on Earth.

Here you can see some of my projects. If you are interested, click on READ MORE to find out more about the topic.

X-ray polarization. A new window on compact objects

Many of my projects are focused on modelling the polarization of X-ray light from neutron stars and black holes. Polarization is an incredible tool to study the geometry of a source, and X-ray polarimetry will soon open a new window on the study of compact objects, as there are several missions under development with a polarimeter on board, including the NASA IXPE, scheduled for launch in 2021.

In particular, I am interested in what the polarization of X-rays can tell us about the accretion geometry in X-ray pulsars, about the structure of the magnetosphere in magnetars and about the role of magnetic fields in black hole accretion and astrophysical accretion in general.

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Mysteries of white dwarfs

White dwarfs are all born in the same manner, as the compact remnants of low and intermediate-mass stars up to about eight times the mass of our Sun. However, many of them present peculiar features that are still matter of debate among astronomers. For example, about a fifth of known white dwarfs show the presence of magnetic fields that range from a few thousand to a billion Gauss, and we still do not know why. Another puzzle is why some white dwarfs are polluted, i.e. they are observed to contain heavy elements in their atmospheres. Using instruments like Gaia, ZTF and Gemini, I hunt for interesting white dwarfs that can help us solve these mysteries.

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Colibrì, measuring the pulses of neutron stars and black holes

In February 2018, the Canadian Space Agency put a call for proposals for science concept studies for space astronomy missions for the 2020s. In response to this call, my collaborators and I gathered a team comprising of nearly all of the high-energy astrophysicists in Canada along with condensed-matter and high-energy physicists to build the first flagship Canadian X- ray telescope, Colibrì. I am the Project Scientist for Colibrì. In July 2018, the CSA chose the Colibrì proposal for an eighteen-month detailed study. We are now working for Colibrì to become an international effort.

Colibrì is a X-ray telescope which is currently in the concept study phase. The main objective of the Colibrì mission is to study the structure of accretion flows in the near vicinity of black holes and neutron stars and the study of emission from the surface of neutron stars thanks unprecedented spectral and timing resolution, paired with high throughput.

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Hunting for ancient brown dwarfs

Brown dwarfs are interesting objects at the boundary between stars and planets. Understanding their physics has important implications in other fields: from star and planet formation and evolution, to dense-matter physics and galaxy evolution. However, modelling a brown dwarf is a hard task, as its appearance depends on many different factors, that are deeply interconnected: its mass and radius, its temperature, composition, age, rotation etc. A new generation of telescope, like JWST, TMT, GMT and ELT, will achieve unprecedented sensitivity in the infrared, where brown dwarfs’ spectra peak. This will enable the detection and study of brown dwarfs that are colder, older, and further away, including the oldest brown dwarfs in the Galaxy: those found in globular star clusters.

For the first time, we will have large samples of brown dwarfs for which these fundamental properties are known to high accuracy, allowing us to break many of the observational degeneracies that arise from their cooling nature. Furthermore, brown dwarfs in globular cluster will provide a new method of measuring the age of globular clusters themselves, completely independent from the ones used until now.

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Other Projects