The Hobby-Eberly Telescope at McDonald Observatory, Texas, USA
My Research
PhD Work
PhD Supervisor: Dr. Stanimir Metchev
University of Western Ontario
London, Ontario, Canada
Sept 2017 - Dec 2021
My doctoral thesis work was on sub-stellar objects known as brown dwarfs. Brown dwarfs are too small to be stars, but too large to be planets. They have complex atmospheres with clouds and hazes of carbon monoxide, water, methane, and other molecules. Large-scale atmospheric features such storms and banding (like those on Jupiter) occur in the atmospheres of brown dwarfs.
During my PhD I led an ambitious spectroscopic follow-up of every variable brown dwarf in the "Weather On Other Worlds" brown dwarf variability project. As the principal investigator on nine successful telescope proposals for the Gemini Observatory and NASA Infrared Telescope Facility, I have obtained over 150 hours of spectroscopic data. I designed and programmed a tool for fitting model spectra to these data to determine the projected rotation velocities and other physical parameters of these objects.
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In the first publication of my doctoral work (Tannock et al, 2021), I identified the three fastest rotating brown dwarfs ever observed, with incredible rotation periods of just one hour (a typical brown dwarf has a rotation period between two and 10 hours). I determined other physical parameters of these objects including their temperatures, surface gravities, and viewing geometries. The clustering of the shortest rotation periods near one hour suggests that brown dwarfs are unlikely to spin much faster.
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Related Publication: AJ, ADS link
Press Releases & Articles: NASA, NOIR Lab,
Nature Research Highlights, Western, Gizmodo, Weather Network, syfy.com, Physics World Magazine
Audio: Physics World Weekly Podcast
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Accurate models of brown dwarf atmospheres are a key took in determining physical parameters of brown dwarfs. In the second publication of my doctoral work (Tannock et al. 2022), I rigorously tested the available atmospheric models with one of the highest-resolution brown dwarf data sets ever observed. I assessed which of the currently-available models are the most reliable and described how to accurately measure fundamental properties of brown dwarfs with these models. In this work I also provide the first detections of hydrogen sulfide (H2S) and molecular hydrogen (H2) absorption features in an extra-solar atmosphere. The H2S detection confirms the assumption of rain-out chemistry – a process where materials condense and sink deeper in to the atmosphere of a brown dwarf. The detection of H2S confirms the rain-out of iron; the preferred molecule for sulfur is iron sulfide (FeS), and so if iron did not rain out, all of the sulfur would be trapped in FeS, and none would be available to form H2S – we wouldn’t see H2S in the spectrum! With the H2 detection, I placed an upper limit on the atmospheric dust concentration of this brown dwarf: at least 500 times less than the interstellar value, implying that the atmosphere is effectively dust-free. I additionally identified several features that do not appear in the model spectra, telling us there is more work to be done in understanding brown dwarf atmospheres!
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Related Publication: MNRAS, ADS link
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Link to My Full Thesis: UWO Libraries
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Image: Visiting the Gemini South Observatory in the Andean Mountains of Chile.
MSc Work
MSc Supervisor: Dr. Stanimir Metchev
University of Western Ontario
London, Ontario, Canada
Sept 2015 - Aug 2017
Brown dwarfs, like every thing in space, are rotating. As the large-scale surface features (spots and banding) rotate in and out of view, the brightness of brown dwarfs varies. From this variability we can determine the rotation periods of brown dwarfs and learn about weather in these atmospheres.
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During my MSc I processed and analysed nearly 500 hours of Spitzer Space Telescope mid-infrared photometry to produce light curves and search for variability in a large sample of brown dwarfs. These results will be presented in a future publication by the Metchev research group at Western University.
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Image: Standing in the barrel of the NASA IRTF telescope at the top of Maunakea, Hawaii.
Undergraduate Thesis
University of Victoria
Victoria, BC, Canada
April 2015
Thesis Title: Constraining models of high-mass star formation with IRAS 20126+4104
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For my final-year undergraduate thesis project, I reduced and analysed near-infrared images from the WIRCam instrument on the Canada France Hawaii Telescope (CFHT) to test whether high mass stars must always form in clusters, or if they may also form in isolation. My study found a large number of previously over-looked young stellar objects embedded in the dust of star forming region IRAS 20126+4104, supporting the cluster theory for an object that was previously thought to form in isolation. For this project I wrote a telescope proposal and observed my own data while visiting the CFHT in Waimea, Hawaii, USA.
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Image: A JHK colour-composite image of IRAS 20126+4104 assembled by me.
ATLAS Electronics Upgrades
University of Victoria
Victoria, BC, Canada
May 2014 - Sept 2014
I designed, built, and tested high-precision, low-noise, voltage controlled current sources for the testing of new electronics for the ATLAS liquid-argon calorimeter. Calorimeters measure the energy of protons and electrons as they interact with matter. ATLAS is one of the four major experiments at the Large Hadron Collider at CERN, in Geneva, Switzerland.
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Image: Prototyping current sources in the lab.
Data Analyst and Software Development Intern
Canada France Hawaii Telescope
Waimea, HI, USA
May 2013 - Sept 2013
I performed a statistical analysis of data from the WIRCam instrument on CFHT to determine the source of artifacts in calibration images called “darks.” I also implemented upgrades the I’iwi Pipeline, a data processing pipeline for the WIRCam instrument, written in IDL. WIRCam is a wide-field infrared mosaic imager.
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Image: Standing with the WIRCam instrument at CFHT at the top of Maunakea, Hawaii.
Exoplanet Research Intern
Herzberg Institute of Astrophysics
Victoria, BC, Canada
Jan 2013 - May 2013
I reduced and analyzed high-contrast images from the Keck Observatory, Spitzer Space Telescope, and the Hubble Space Telescope to study the HR 8799 planetary system. I investigated objects at wide separations to determine if they were bound to the star or background objects, and I developed an optimized point spread function (PSF) subtraction method to investigate the debris disk around the star. HR 8799 is a well-known exoplanetary system hosting at least four planets and a debris disk. The planets around HR 8799 were the first ever to be directly imaged.
Related Publication: ADS Link
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Image: Visiting the Keck Observatory at the top of Maunakea, Hawaii.
Software Development Intern
Canada France Hawaii Telescope
Waimea, HI, USA
May 2012 - Sept 2012
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I wrote, tested, and optimized image classes and data processing modules for the OPERA Pipeline, a data processing pipeline for the ESPaDOnS instrument, written in C and C++. ESPaDOnS is a high-resolution echelle spectrograph and spectropolarimeter.
Related Publication: ADS Link
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Image: Taking mirror selfies in the barrel of the CFHT telescope at the top of Maunakea, Hawaii during mirror cleaning.
Instrument Monitoring and Support Intern
Gemini Observatory
Hilo, HI, USA
Sept 2011 - Jan 2012
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I debugged and completed a fully automatic Python script for monitoring the performance and health of the GNIRS instrument. GNIRS is an infrared spectrograph. My work has come full circle over the last 10 years, and I am now a regular user of the GNIRS instrument for my PhD thesis work!
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Image: Taking data at the Gemini North Observatory at the top of Maunakea, Hawaii.