Sean MacBride

Hi. I am a physicist studying cosmology. I am currently earning my Ph.D in physics at the University of Michigan-Ann Arbor under the direction of Marcelle Soares-Santos.

Current Research

At Michigan, I studying dark energy and cosmology under the direction of Marcelle Soares-Santos. Michigan was the primary contributor to the focal plane of the Dark Energy Spectroscopy Instrument (DESI). I currently have two foci in instrumentation: improving the precision of the existing DESI focal plane, and prototyping the next generation of instruments for dark energy surveys.

The DESI focal plane is composed of 5,000 robotic positioners, each holding a fiber-optic cable. An unforseen challenge of the DESI focal plane design is the development of radial cracks in small pinion gears critical to the movement of the robotic positioner. To test these issues, a telescope simulator was built, with a single fiber positioner for testing installed inside. We are currently testing different operational procedures to rectify the problem through without significant hardware changes.

In parallel to refining the existing DESI instrument, we are planning for the next generation of dark energy surveys. Development of the telescope simulator will enable future testing of prototype instruments. The primary design improvement would be increasing the fiber-positioner density on the focal plane, resulting in an order of magnitude increase in data volume and scientific capabilities.

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Past Research

Continuous Gravitational Waves

Previously at Michigan, I studied continuous gravitational waves from rapidly spinning neutron stars. I am developing specialized tools for detecting continuous gravitational waves from post-merger binary star systems that have recently coalesced into a single compact object, usually another neutron star.

Think of this less cosmic example: If a perfectly spherical ball was spinning on the surface of a still body of water, the ball would not generate any ripples in the water due to the uniform surface of the ball. If a rugby ball or any other non-spherical object was rapidly spinning on the surface of a still body of water, it would generate ripples, due to the non-spherical surface interacting with the water differently as the ball progresses through a single rotation.

When neutron stars rotate very fast, they deform from a perfectly spherical star to an oblate spheroid, which looks somewhat like a rugby ball, or an American football. The “ripples in the water” are instead ripples in space, which can be detected with interferometers. These continuous ripples are very weak in comparison to the ripples from mergers, so I use data collected from the LIGO interferometers over their two-year observation runs.

I developed code to model the gravitational wave ringdown of a neutron star binary merger, and separately developed a detection statistic to measure if a given model template is properly detecting an injected signal. I tested different signal models to ensure the robustness of the detection statistic under the tuning of different parameters.

Integrating the LLAMAS spectrograph at the Massachusetts Institute of Technology

I earned the opportunity to further my technical repertoire when I joined the Astronomical Instrumentation Team (AIT) at the Massachusetts Institute of Technology in November 2020, under principal investigator Gábor Fûresz and faculty lead Prof. Rob Simcoe. AIT is building the LLAMAS spectrograph for the Magellan Telescopes at Las Campanas Observatory in Chile, scheduled to be installed in July 2022. I assembled optical mounts and ground support equipment, designed optical mounting fixtures, and tested diffraction gratings to ensure they met optical-design requirements.

Bonding the first fiber in the LLAMAS spectrograph

My principal responsibility was integrating the fiber run of the spectrograph. I found that my early attempt to bond fibers with the required precision was too slow to meet our project deadlines. To remedy this, I wrote LabView code to allow for simple DC motor control through a computer interface, removing a critical project bottleneck. These adjustments enabled exceptional accuracy in the fiber run when compared to the design requirements (100% fiber yield vs. 99.5% requirement). I presented the science and engineering status of the LLAMAS instrument to an astronomy class at Wheaton College in November 2021.

The LLAMAS Team!

The STellar Activity Recorder and SpectroPhotometric ObservaTory

In parallel to LLAMAS, I have developed software tools to support a research proposal for AIT, concentrating on using solar spectrophotometry to extend photosphere and chromosphere events on the sun to activity on exoplanet host stars. AIT has installed a multi-channel solar spectrometer at Lowell Observatory in Flagstaff Arizona to perform a preliminary ground-based study. I created analysis tools for this spectrometer and organized meetings between AIT members and collaborators at other institutions.

Early in the project, I struggled with developing a data pipeline that maintained compatibility with all of the observations, as their file structure was constantly being modified to accommodate the high data volume. After iteration, I constructed a robust and flexible data pipeline with the capability to accurately represent all solar observations. This pipeline enabled a detailed analysis of several solar events in the second half of 2021 and served as supporting evidence in a forthcoming publication that describe the project scope.

Cold-gas and dust evolution in star-forming galaxies

I investigated cold-gas and dust scaling relationships in star-forming galaxies in a joint venture between associate professor Amélie Saintonge at University College London and Professor Maitra at Wheaton College. I built a data pipeline for use with derived data from the xCOLD GASS, JINGLE, and SDSS galaxy surveys. I developed a Markov-chain Monte-Carlo sampler to constrain the relationship between different matter components and the Balmer emission of star-forming galaxies in the xCOLD GASS and JINGLE surveys.

Adjusting to the COVID-19 pandemic to work from home

When the full effects of the COVID-19 pandemic began to impact the world, I adjusted to working from home to complete the project within the modified school year. I applied the smaller survey calibration to a wider set of galaxies in SDSS to discover a bias from galactic inclination. Through a virtual thesis defense, I presented these results to faculty and peers from both institutions and submitted a final report, earning the highest distinction from the faculty of both colleges.

Following this presentation, I generalized the calibration to include the effects of galactic inclination to better constrain the cold-gas and dust content. This study will be used with the Bright Galaxy Survey from the newly commissioned Dark Energy Spectroscopy Instrument (DESI) to provide a critical understanding of the evolution of baryons in the dark-energy dominated universe.

Nanophysics for medical diagnostics

I studied at University College London (UCL) during the spring semester of my junior year. The pinnacle achievement of the spring came during a Group Project with other UCL students and the Royal Institute of London, determining the detection limits of lateral flow assays through photothermal heating of magnetic nanoparticles.

While I was unacquainted with the other members of my group and had no previous experience in biophysics, the project provided an opportunity to test my intellectual flexibility and management skills in an unfamiliar environment. I took a leading role in the project by coordinating laboratory logistics, maintaining safety measures, and preparing solutions and samples for observation.

I aided in the design of the sample and laser apparatus, conducted sample experiments, and analyzed photothermal heating data to determine the optimal solution concentration and membrane type to maximize the photothermal signal. The results of this study were documented in a report, presented at a poster session, and received the highest marks from UCL and Royal Institute faculty.

Tidal disruptions in dwarf satellite galaxies

In the summer following my sophomore year at Wheaton College, I earned a position in the National Science Foundation Research Experiences for Undergraduates program at Rutgers University. I was paired with Professor Carlton Pryor to study dwarf satellite galaxies using astrometry from the second data release of the Gaia space observatory. I developed a data pipeline with photometric and kinematic filters that could be applied to any Gaia data selection. After failing to discover a structural disruption in the Boötes dwarf satellite, I detected a tidal tail induced by the proper motion of the dwarf satellite Carina.

The cohort of the 2018 REU physics and astronomy at Rutgers University

Accepting the minor setbacks that preceded this awe-inspiring scientific discovery was a crucial moment that pivoted my research philosophy towards appreciating every step of the process that precipitates success. I presented a poster at the Rutgers Summer Research Symposium and the 234th meeting of the American Astronomical Society in St. Louis, Missouri. I also delivered oral presentations to faculty and peers at both Rutgers University and Wheaton College.

My poster showcasing the observational evidence of tidal disruption in Carina at the 234th meeting of the AAS in St. Louis MO.

Presenting at Wheaton College enabled an opportunity to become an active peer advisor to other Wheaton students, providing academic, professional, and personal guidance on a formal and informal basis. Studying at Rutgers offered me the chance to be a principal contributor in an astronomy research project and to improve the careers and lives of fellow students, even after I graduated.

P.A.N.O.P.T.E.S.

In my sophomore year at Wheaton College, I shifted my focus towards astronomy. I sought out Professor of astronomy, Dipankar Maitra. Professor Maitra connected me with another Wheaton student, and we began collaborating on a citizen-science exoplanet collaboration called project PANOPTES. In coordination with software engineer James Synge of Google, we installed a robotic telescope inside an observatory dome at Wheaton. When installing the unit, it became clear that some modifications to the magnetic sensors in the dome were necessary to ensure continuous compatibility.

PANOPTES giving us some trouble, staring at the sky, exposing its non-weather-proofed lenses to the elements

After amending the sensor placement with hand tools, I aligned the unit over three nights of precise adjustments in the frigid February weather of Massachusetts while the PANOPTES team communicated through an online chat. Once operating, I presented the PANOPTES instrumentation at the Northeast Astronomy Forum 2018 in Suffern New York in the hopes of attracting other amateur astronomers to expand the PANOPTES network.

My peer, collaborator, and good friend Joseph Casarella standing alongside PANOPTES at NEAF 2018

I continued maintenance on the PANOPTES telescope and observatory dome until it was removed for weather-proofing upgrades in December 2018.

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CV

My most recent C.V. is available for view or download here.

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Contact

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