Sebastien Guillot

I am currently a FONDECYT Postdoctoral Fellow at the Instituto de Astrofísica of the Pontificia Universidad Católica de Chile. I am part of the ANSWERS group led by Prof. Andreas Reisenegger. My work focuses on observations of neutron stars.
In July 2014, I completed my PhD in Physics at McGill University, under the supervision of Prof. Robert Rutledge. My thesis was entitled "Neutron Stars and the Determination of the Dense Matter Equation of State". I was a Vanier Canada Graduate Scholar.

Interested in my research?

My Research

Observations of neutron stars

Neutron stars are fascinating objects. Born from the supernova explosion of a massive star, they contain between 1 and 2 times the mass of our Sun within a sphere of 10 to 13 km in radius. They are extremely compact and made of a type of matter than we do not understand. If something could compress a neutron star a little more, they would collapse into a black-hole. Neutron stars emit light in a variety of form: some have beams of radio emission from their poles sweeping across space as they rotate with an extreme regularity; for some neutron stars, we can actually see the emission from their hot 1,000,000 K surface, so hot that they emit X-rays instead of the visible light that we are used to see from stars. I am particularly interested in this surface emission from neutron stars.

The dense matter equation of state

I use astrophysical observations of neutron stars to help understand the nuclear physics of ultra-dense matter. Because such matter cannot be produced in laboratories, neutron stars are the only place where it can be studied. The many different predictions of nuclear physics lead to many different proposed interior composition of neutron stars (see Figure, each part shows a different prediction of the neutron star interior structure). Measuring the radius of neutron stars is one of the few existing methods to understand their interior structure and therefore to constrain the dense matter equation of state. This is done by comparing the measured radius with the predictions of theoretically proposed equations of state.

Here are my publications as first author.

Here are my publications as co-author.

A High Braking Index for a Pulsar

Robert F. Archibald, Eric V. Gotthelf, Robert D. Ferdman, Victoria M. Kaspi, Sebastien Guillot, Fiona A. Harrison, Evan F. Keane, Michael J. Pivovaroff, Daniel Stern, Shriharsh P. Tendulkar, John A. Tomsick
March 2016, ApJL, 819, 16

Phase-Resolved Nustar And Swift-XRT Observations Of Magnetar 4U 0142+61

Shriharsh P. Tendulkar, Romain Hascöet, Chengwei Yang, Victoria M. Kaspi, Andrei M. Belobodorov, Hongjun An, Matteo Bachetti, Steven E. Boggs, Finn E. Christensen, William W. Craig, Sebastien Guillot, Charles A. Hailey, Fiona A. Harrison, Daniel Stern, William Zhang
July 2015, ApJ, 808, 32


I have a passion for astronomy and science communication, and I don't miss an opportunity to interact with the general public or with kids of all ages. During my PhD at McGill, I have been very actively involved in astronomy outreach and communication. I co-founded with Ryan Lynch and co-chaired for 3 years the outreach group AstroMcGill, which now runs a very successful outreach program.
Now that I am in Chile, I am currently improving my spanish to be able to interact with the Chilean public, and continue the outreach activities that I love.

Public lectures

I love giving public lectures on any subject of astronomy. I have had the chance to give several public lectures of the AstroMcGill Public Astro Night series, in community centers, and for local astronomy clubs.


I have been the host of over 40 podcast interviews of the AstroMcGill Podcast series. During those, I interviewed astrophysicists visiting McGill University to discuss their research in a way accessible to everyone.

School Activities

As part of the AstroMcGill program of school activities, I visited over 30 schools to present hands astronomy activities to kids of all ages. I also organized all these visits with the team of AstroMcGill volunteers.

Night sky observations

I have also organized and led numerous star parties, either following the AstroMcGill Public Astro Nights, or with undergraduate astronomy classes, primary schools and summer camps, or for special astronomical events.

TV and Radio Interviews

During my time as co-chair of AstroMcGill, I did multiple recorded and live interviews on local and national television and radio to discuss astronomical events (transit of Venus or the landing of robot Philae on the Comet 67P)

Accessible PhD Thesis Summary

My PhD thesis contains a summary of the subject and the results written for a general audience. It is available in English and in French. Feel free to send me comments.
Image credits: NASA GSFC.

AAS Astronomy Ambassador

I was part of the first cohort of the American Astronomical Society Astronomy Ambassador Program. This program provides mentoring and training experiences for young astronomers, as well as access to resources and a network of contacts within the astronomy EPO community

Here is how you can contact me

sguillot at astro dot puc dot cl

Mailing address:
Instituto de Astrofisica
Pontificia Universidad Catolica de Chile
Av. Vicuna MacKenna 4860
782-0436 Macul,
Santiago, Chile

I am also on some social networks