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.
This is an exciting time for stellar astrophysics as high-cadence time domain surveys (Gaia, PTF, ZTF, ATLAS, Kepler, TESS, and, in the near future, the Vera Rubin Observatory) are revolutionizing the landscape of stellar studies by allowing the exploration of the dynamic sky. Furthermore, spectroscopic surveys are ongoing (SDSS V, DESI, WEAVE etc.), which will provide spectral classifications for millions of stars. Space missions are also opening new windows on stars and their remnants: December of 2021 alone saw the launch of JWST, with its unprecedented sensitivity in the infrared, and of IXPE, the first mission dedicated to X-ray polarimetry. And LISA and Roman are just around the corner.
I have expertise in both theory and observations, and I investigate stars and their remnants by mining rich datasets from large surveys, leading multi-wavelength observational campaigns, and developing theoretical models for their emission processes, structure, and evolution. Here you can see some of my projects. If you are interested, click on READ MORE to find out more about the topic.
Stellar Evolution in Star Clusters
Star clusters are excellent laboratories for testing theories of stellar evolution, as they comprise a large sample of stars over a broad mass spectrum, at the same distance from Earth and with similar ages and chemical compositions. The HST legacy of archival observations of clusters is truly impressive, amounting to thousands of hours in almost every energy band, and new capabilities have been opened by observatories like JWST, Gaia, and, in the near future, by the ELTs.
A careful look at clusters can finally provide the answers to many open questions about their formation and evolution, as well as help us understand key phases of stellar evolution.
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, there are several aspects of white dwarf evolution that are unconstrained and have dramatic consequences for a wide variety of astrophysical fields - from planetary system evolution, to the interior physics of massive stars, to cosmology. What causes some white dwarfs to be magnetic? Why are some white dwarfs deprived of hydrogen and what is the physics behind white dwarf spectral evolution? Why are some white dwarfs' atmospheres polluted with metals and what do they tell us about the evolution of planetary systems after their stars die? What are the progenitors of type Ia supernovae?
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. After nearly five decades from the flight of OSO-8 and the first detection of polarized X-rays from the Crab, we just entered the era of X-ray polarimetry, with the launch of the Imaging X-ray Polarimetry Explorer, or IXPE, in December of 2021. Polarization provides information on the geometry of the emission region: it allows us to zoom in on the one-kilometer-wide emission region on a neutron star or accreting black hole several kiloparsecs away. Furthermore, quantum electrodynamics (QED) can dramatically modify the polarization of X-rays traveling in the magnetospheres of neutron stars and black holes, so X-ray polarization probes both the birefringence of the magnetized vacuum, one of the first predictions of QED as yet undetected, and the magnetic field structure of these objects. I am currently collaborating with IXPE team members to interpret several of the new spectropolarimetry observations
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.