Abel Lawrence Peirson
alpv95 at stanford dot edu
[News | Xp | Research | Projects |
Misc. | Blog]
I am a Ph.D student in Physics at Stanford University,
where I research
high energy astrophysics, astrostatistics and applications of machine learning as a
FINESST fellow and Stanford data science
I am interested in scientific applications of machine learning and statistics that incorporate
One of my ongoing projects has been increasing the science output of NASA's flagship X-ray polarimetry
mission IXPE using simulation based inference
I am equally interested in the science made possible by these improvements, for example, how the
geometry of relativistic jets affects their polarized emission, and statistical techniques to properly
See my research highlights below for an overview.
Previously, I received my bachelors and masters (MPhys) in Physics from the University of Oxford,
Christ Church, where I specialised in theoretical and particle
- 12/05/22 Invited Talk at IAUS 375:
The Multimessenger Chakra of Blazar Jets in Kathmandu, Nepal.
- 11/18/22 Talk at Columbia theoretical high-energy astrophysics group (THEA)
- 11/15/22 Talk at Alphabet ML summit.
- 09/11/22 Finished Ironman 70.3 Santa Cruz in 5hr55.
- 06/20/22 Starting an internship at Google Brain!
- 06/13/22 Grant to attend the Nordic Probabilistic AI School in
- 02/10/22 Invited talk at Max-Planck-Institut für Radioastronomie blazar seminar.
- 12/13/21 Talk + poster at 4th Workshop on Machine Learning and the Physical Sciences
- 12/09/21 Invited to NASA IXPE telescope launch (via Space X Falcon 9) at Cape Canaveral.
- 10/31/21 Contributed a chapter to the Springer Nature Handbook of X-ray and Gamma-ray
- 10/30/21 Made official science collaborator for NASA's IXPE telescope mission.
- 00/13/21 Awarded Stanford Data Science Scholarship and joined the program. [Profile]
- 09/23/21 Invited Naval Research Laboratory
Astrophysics colloquium in Washington D.C. [Slides]
- 06/20/21 Quantitative research internship at G-Research in London (job offer).
- 06/01/21 Invited Talk at the IXPE Third Science Collaboration Meeting on optimal
signal extraction for IXPE.
- 05/26/21 Talk at RoboPol conference Looking at the polarized Universe: past, present
and future. [Recording]
- 09/20/19 Selected as Bay Area Wonderfest science envoy. [Profile]
- 09/14/19 Awarded NASA Future Investigator of NASA Earth and Space Sciences (FINESST) grant.
- 08/24/19 President of the Stanford Judo Club 2019-20.
- 11/12/18 Panel discussion at the Pratt institute NY on the future of AI in jewellery design.
- 08/29/18 Interviewed on episode 68 of the NVIDIA AI podcast. [Recording]
- 06/15/18 My work featured in Techcrunch: Dank learning
system autogenerates memes.
- Google Brain, Student Researcher
June - September 2022
Research into practical optimization methods for deep learning.
Working with Rohan Anil,
and Manfred Warmuth. [Webpage]
- G-Research, Quantitative research intern
June - September 2021
Forecasting capital markets and identifying trading strategies. [Webpage]
- Stanford PHYS113: Computational Physics, Teaching Assistant and Lecturer
January - April 2021
Prepared and delivered lectures on optimization and statistical inference. [Slides 1][Slides
- Stanford PHYS100: Observational Astrophysics, Teaching Assistant
April - June 2019
Optical telescopes, practical observation and data analysis.
Open Source Software
- MulensModel: Fast gravitational microlensing simulation/fitting package.
- SSCpol: Polarized relativistic jet simulation in C with Python wrapper.
- Dank Learning: 'Show and Tell' image captioning for meme generation.
Presently, I am developing second order optimization methods for and understanding the training dynamics of
deep neural networks at Google Brain, further improving IXPE's spatial and energy resolutions with
simulation-based inference, and interpreting IXPE's ongoing scientific discoveries.
Representative publications are highlighted.
The X-ray Polarization View of Mrk~421 in an Average Flux State as Observed by the Imaging X-ray
Laura Di Gesu et al. (IXPE collaboration, incl. A.L.
ApJ Letters, 2022, accepted.
First X-ray polarization measurements of Mrk 421.
The extremely high and constant polarization fraction compared to the optical is exciting --
I'm working on the subsequent observations of this source where we found hints of EVPA rotation.
Polarized Blazar X-rays imply particle acceleration in shocks
I. Liodakis et al. (IXPE collaboration, incl. A.L. Peirson)
Nature, 2022, accepted.
Very exciting observations of X-ray polarization in Mrk 501.
I did some of the data analysis for this one and I am designing its potential Nature cover with DALL-E2!
Polarized X-rays Constrain The Disk-Jet Geometry in a Black Hole X-ray Binary
H. Krawczynski, et al. (IXPE collaboration, incl.
Science, 2022, submitted.
IXPE observes Cyg X-1, finding a higher than expected polarization -- revealing the structure of its accretion
disk and jet.
Testing High-Energy Emission Models for Blazars with X-ray Polarimetry
A.L. Peirson, I. Liodakis, R.W.Romani
The Astrophysical Journal, 2022
Here we show how a well placed IXPE observation could potentially measure both synchrotron and SSC polarization
probing our current understanding of blazar jets and testing hadronic emission scenarios.
Neural network analysis of X-ray polarimeter data
Springer Nature, 2022
Invited chapter for the Springer Nature textbook "Handbook of X-ray and Gamma-ray Astrophysics",
editors: Cosimo Bambi and Andrea Santangelo.
An in depth summary of many of the simulation based inference
techniques we have developed for X-ray polarimetry.
A Deep Ensemble Approach to X-ray polarimetry
Fourth Workshop on Machine Learning and the Physical Sciences (NeurIPS), 2021
Setting the state of the art signal recovery in X-ray Polarimetry.
The code from this and my previous works will eventually be used as part of IXPE's official data analysis pipeline.
We model the uncertainties on heteroskedastic photoelectron track angle predictions using deep
ensembles of CNNs
and derive the appropriate maximum likelihood estimator for polarization parameter reconstruction.
Our work will reduce telescope exposure times by up to 40% for a given signal-to-noise ratio.
New Tests of Millilensing in the Blazar PKS 1413+135
A.L. Peirson, I. Liodakis, A.C.S. Readhead et al.
The Astrophysical Journal, 2021
We fit a complex binary lens magnification model to multiwavelength blazar lightcurves using Bayesian
nested sampling (MultiNest).
To speed up the algorithm, I used convex optimization to marginalize over the (constrained) linear
parameters in real time, reducing the number of free parameters to be sampled.
Our empirical results tentatively suggest that the blazar could be lensed.
Towards Optimal Signal Extraction for Imaging X-ray Polarimetry
The Astrophysical Journal, 2021
We show our polarization estimators using deep ensemble quantified uncertainties are optimize the
signal-to-noise ratio for realistic observations.
Using a CNN based classifier we can exclude, with high confidence, events converting outside of the main
We apply our new technique to a selection of astrophysical spectra, including complex extreme examples.
The Relativistic Jet Orientation and Host Galaxy of the Peculiar Blazar PKS 1413+135
A. C. S. Readhead,
A. L. Peirson et al.
The Astrophysical Journal, 2021
PKS 1413+135 is one of the most peculiar blazars known.
We provide observational evidence suggesting that the blazar could be gravitationally microlensed.
Deep Ensemble Analysis for X-ray Polarimetry
Nuclear Instruments and Methods in Physics Research A , 2020
Our first work using deep ensembles and heteroskedastic uncertainty quantification to improve IXPE's sensitivity by more than 30%.
In order to measure polarization using a gas pixel detector, a distribution of photoelectron angles
must be extracted
from noisy images of their individual tracks on a hexagonal grid. We use a ResNet-18
architecture to predict the initial photoelectron angle and its uncertainty for each track image, as
well as the absorption point and energy. By combining predictions from an ensemble of networks in a
weighted maximum likelihood analysis, we estimate the polarization fraction and EVPA of the X-ray
The Polarization Behavior of Relativistic Synchrotron Self-Compton Jets
The Astrophysical Journal, 2019
Exploring the expected synchrotron self-Compton polarization from blazar jets. A continuation of our
multizone geometric jet model.
For low-synchrotron peaked blazars, the X-ray emission will be dominated by synchrotron self-Compton.
what polarization levels IXPE is likely to see in this case is
for distinguishing between hadronic and leptonic blazar emission models. Importantly we find that a
rise in synchrotron polarization fraction at high energies is guaranteed by basic relativity
Prospects for Detecting X-Ray Polarization in Blazar Jets
The Astrophysical Journal, 2019
A study in the detectability of X-ray polarization in blazars for IXPE.
Using the models developed in the adjacent relativistic jet papers and optical polarization
by RoboPol, we are able to make predictions of the average expected
X-ray polarization fraction.
This work helped the IXPE team choose appropriate first year observing targets.
The X-ray Polarization Probe Mission Concept
L.Peirson et al.
Decadal Survey on Astronomy and Astrophysics , 2020
A white paper for the upcoming Decadal survey introducing XPP, a second generation X-ray polarimeter
that will cover
0.2 - 60keV energies (IXPE covers 1-10keV).
Hopefully we will demonstrate the potential of imaging X-ray polarimeters with IXPE.
The Polarization Behavior of Relativistic Synchrotron Jets
The Astrophysical Journal, 2018
Using simple helical geometry and relativistic aberration effects to explain blazar polarization angle
Our follow up paper for the synchrotron self-Compton emission is above.
Unbiased sample of projects outside of my usual research.
Dank Learning: Generating Memes Using Deep Neural Networks
A.L.Peirson V, E.M.Tolunay
Accepted to Advances in Intelligent Systems and Computing, 2018
An image captioning system that can take any image and turn it into a first generation meme. Uses pre
trained Inception CNN followed by an LSTM with temperature selection for language generation.
Trained on a dataset of over 300,000 image caption pairs I scraped from
What started as a fun class project ended up being featured on
Inspired, I worked together with Dylan Freedman to create the
free iOS app
Dank Learning so anyone can use the 'AI' to generate memes.
I discuss the work in the
podcast, and its implications
for the future of art and jewellery at the Pratt Institute.
Making and displaying unique exoplanet inspired art.
We bought a 1982 HP7470a plotter printer
make it plot starfields around exoplanets. Check out our gallery
of all the exoplanets we
know of (we can plot other astronomical objects too... The image on the left is M51: the whirlpool
We have also made a 3d version in Unity: Achtung, 3die Kurve!, not available online yet.
I hope to build an RL agent in collaboration with Taylor Howell
that solves Achtung, die Kurve!
- Ironman 70.3, Santa Cruz 2022. [S: 35m, B: 3hr05, R: 2hr02, T: 5hr55]
- San Jose Buddhist Judo Tournament, Team Champions 2018.
- Oxford Summer Eights, Head of the river 2017.
- Native Spanish speaker.