I'm interested in how the geometry of relativistic jets affects their polarized emission, and how we can improve high energy polarimetry using statistical learning and computer vision techniques. I am currently incorporating convex optimization into
searches for rare blazar lensing events, further improving IXPE's spatial and energy resolutions,
and taking Dank Learning to the next stage.
Towards Optimal Signal Extraction for Imaging X-ray Polarimetry
The Astrophysical Journal, 2021
Again setting the state of the art signal recovery in X-ray Polarimetry.
We describe an optimal signal extraction process for imaging X-ray polarimetry using an ensemble of deep neural networks.
We show how the expected modulation amplitude from each event gives an optimal weighting to maximize signal-to-noise ratio of the recovered polarization.
Applying this weighted maximum likelihood event analysis yields sensitivity (MDP99) improvements of ~10% over earlier heuristic weighting schemes and
mitigates the need to adjust said weighting for the source spectrum.
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,
M. L. Lister,
M. F. Aller,
R. D. Blandford,
I. W. A. Browne,
K. J. B. Grainge,
M. A. Gurwell,
M. W. Hodges,
T. J. Pearson,
A. L. Peirson,
E. S. Perlman,
R. A. Reeves,
B. T. Soifer,
G. B. Taylor,
H. K. Vedantham,
P. N. Wilkinson,
J. A. Zensus
The Astrophysical Journal, 2021
A additional piece of evidence for gravitational lensing in this blazar.
PKS 1413+135 is one of the most peculiar blazars known.
Its strange properties led to the hypothesis almost four decades ago that it is gravitationally lensed by a mass concentration associated with an intervening galaxy.
Intensive efforts to understand this blazar have hitherto failed to resolve even the questions of the orientation of the relativistic jet and the host galaxy.
We show that the jet axis is aligned close to the line of sight and PKS 1413+135 is almost certainly not located in the apparent host galaxy,
but is a background object in the redshift range 0.247 < z < 0.5. The intervening spiral galaxy at z = 0.247 provides a natural host for the putative lens responsible for
symmetric achromatic variability and is shown to be a Seyfert 2 galaxy.
Deep Ensemble Analysis for X-ray Polarimetry
Nuclear Instruments and Methods in Physics Research A , 2020
Using Deep ensembles and parametric density estimation with uncertainty to improve IXPE's sensitivity by more than 30%.
In order to measure polarization using a GPD, a distribution of photoelectron angles must be extracted
from noisy images of their individual tracks on a hexagonal grid. We use a convolutional neural network
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 source. This work sets the new state of the art in high energy polarimetry.
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 jet model.
For low-synchrotron peaked blazars, the X-ray emission will be dominated by synchrotron self-Compton. Understanding
what polarization levels IXPE is likely to see in this case is important
for distinguishing between hadronic and leptonic blazar emission models. We find that our multizone model recovers
simple predictions for SSC polarization, but describes new dependencies on jet viewing geometry. Importantly we find that a
rise in synchrotron polarization fraction at high energies is guaranteed by basic relativity considerations.
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 observations
by RoboPol, we are able to make predictions of the average expected X-ray polarization fraction.
This work will help the IXPE team choose appropriate first year observing targets.
The X-ray Polarization Probe Mission Concept
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!
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 rotations.
Follow up paper for the synchrotron self-Compton emission coming soon.
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.
Transverse Beam Phase-Space Measurement Experience at CTF3
S.Dobert, L.Malina, L.Martin,
A.Peirson Serratosa, T.Persson, J.Roberts, A.Rollings, Piotr Skowroński, Frank Tecker
8th International Particle Accelerator Conference, 2017   ,
Characterising the transverse phase space of the CTF3 beam before and after beam recombination with the Delay Loop.
I'm indebted to Dylan Freedman for introducing me to the very American
concept of a side project -- as such many of my projects are collaborations with him. For fun and more...
Making and displaying unique exoplanet inspired art.
We bought a 1982 HP7470a plotter printer and we
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 galaxy).
this one was mainly D (I still smash him at the game though); one of my main contributions was including a poisson distribution for generating threadable gaps
in the curves. We have also made a 3d version in Unity: Achtung, 3die Kurve!, not available online yet.