About

Amy L. Halverson, MD, is a Professor of Surgery specializing in Gastrointestinal and Endocrine surgery at Northwestern University Feinberg School of Medicine. She also serves as the Vice Chair of Surgical Education. Her role involves overseeing surgical education initiatives within the department, contributing to the training and development of future surgeons. The page highlights her position and responsibilities but does not provide specific details about her research focus or key contributions.

Research topics

• Computer Science
• Data science
• Astronomy
• Systems engineering
• Physics

Selected publications

• GW-integration

  Zenodo (CERN European Organization for Nuclear Research) · 2026-03-25 · 1 citations

  otherOpen accessSenior author

  v0.1.0 of the Github repository of GW-integration, which contains an integrator of Peters' equations for gravitational wave inspiral calculations in ln-space.

  PublisherDOI

• GW-integration

  Zenodo (CERN European Organization for Nuclear Research) · 2026-03-25

  otherOpen accessSenior author

  v0.1.0 of the Github repository of GW-integration, which contains an integrator of Peters' equations for gravitational wave inspiral calculations in ln-space.

  PublisherDOI

• Forming Double Neutron Stars Using Detailed Binary Evolution Models with POSYDON: Comparison to the Galactic Systems

  The Astrophysical Journal · 2026-01-13 · 2 citations

  articleOpen access

  Abstract With over two dozen detections in the Milky Way, double neutron stars (DNSs) provide a unique window into massive binary evolution. We use the POSYDON binary population synthesis code to model DNS populations and compare them to the observed Galactic sample. By tracing their origins to underlying single and binary star physics, we place constraints on the detailed evolutionary stages leading to DNS formation. Our study reveals a bifurcation within the well-known common envelope (CE) formation channel for DNSs, which naturally explains an observed split in the orbital periods of the Galactic systems. The two subchannels are defined by whether the donor star has a helium core (Case B mass transfer) or a carbon-oxygen core (Case C) at the onset of the CE, with only the helium core systems eventually merging due to gravitational-wave-modulated orbital decay. We find that across different treatments of the CE phase, the formation of DNSs through both subchannels requires either a generous core definition of ≃30% H-fraction or a high CE ejection efficiency of α CE ≳ 1.2. By testing different supernova kick velocity models, we find that galactic DNSs are best reproduced using a prescription that favors low velocity kicks (≲50 km s −1 ), in agreement with previous studies. Furthermore, our models indicate that merging DNSs are born from a stripped progenitor with a median pre-supernova envelope mass ∼0.2 M ⊙ . Our results highlight the value of detailed evolutionary models for improving our understanding of exotic binary star formation.

  PublisherDOI

• Evidence for a Catastrophically Disrupted Open Cluster

  The Astrophysical Journal · 2025-06-03 · 2 citations

  articleOpen accessCorresponding

  Abstract Of the many discoveries uncovered by the Gaia astrometric mission, some of the most exciting are related to nearby dispersed stellar structures. We analyze one such structure in the Milky Way disk, OCSN-49, a coeval stellar stream with 257 identified members spanning approximately 30° across the sky. We obtained high-resolution spectroscopic data for four members that span the stream’s extent, finding these four stars to have solar metallicities and remarkably homogeneous chemistry. Through a combination of isochrone fitting, lithium abundance analysis, and gyrochronology, we find a consistent stellar age of 400–600 Myr. Integrating stellar orbits backwards reveals that OCSN-49 converged to a single point at a much younger age. By integrating unbound model stars forward and comparing them to the current phase-space distribution of OCSN-49, we derive a dynamical age of 83 ± 1 Myr, inconsistent with the age of the stellar population. The discrepancy between the kinematic and stellar age indicators is naturally explained by a disruptive event that unbound OCSN-49 roughly 500 Myr into its lifetime. Based on rate estimates, disruption due to a passing giant molecular cloud (GMC) is the most likely culprit. Assuming a single encounter, we find that a nearly head-on collision with a fairly massive GMC (∼10 5 M ⊙ ) was necessary to unbind the cluster, although encounters with multiple GMCs may be responsible. To our knowledge, OCSN-49 serves as the first known remnant of a catastrophically disrupted open cluster, and therefore serves as a benchmark for further investigating cluster disruption in the Milky Way.

  PublisherDOI

• Emulators for stellar profiles in binary population modeling

  Astronomy and Computing · 2025-01-31 · 2 citations

  preprintOpen access
  PublisherOA PDFDOI

• Forming Double Neutron Stars using Detailed Binary Evolution Models with POSYDON: Comparison to the Galactic Systems

  ArXiv.org · 2025-07-31

  preprintOpen access

  This dataset contains the downsampled data, as well as the trained classification and interpolation models from the CO-HMS_RLO and CO-HeMS grids at Solar metallicity. A detailed description of these datasets can be found in Section 2.3 of Chattaraj et al. (2025). The simulations follow the same setup as in Fragos et al. (2023) and Andrews et al. (2025). If you make use this dataset, please cite the following references: Chattaraj et al. (2025) Andrews et al. (2025) Fragos et al. (2023)

  PublisherOA PDFDOI

• Interacting binaries as a significant progenitor channel for Type II-P supernovae

  Research Square · 2025-06-12

  preprintOpen access
  PublisherOA PDFDOI

• A binary merger product as the direct progenitor of a Type II-P supernova

  Research Square · 2025-01-07

  preprintOpen access
  PublisherOA PDFDOI

• The demographics of binary companions to stripped-envelope supernovae: confronting population synthesis models with observations

  Monthly Notices of the Royal Astronomical Society · 2025-12-16 · 5 citations

  articleOpen access

  ABSTRACT Stripped-envelope supernovae (SESNe) mark the deaths of massive stars without hydrogen-rich envelopes. Most SESNe likely originate from binary systems where a companion stripped the progenitor of its envelope. Years of HST imaging of nearby SESN sites have produced a statistically meaningful sample of constraints on surviving binary companions. We assemble the current sample of six companion detections and six non-detections from the literature, re-analysing whenever needed. We then conduct the first statistical comparison with binary population-synthesis predictions, primarily based on new calculations performed with the POSYDON framework. Across a metallicity range, our models predict that 80–90 % of Type Ib/c and 60–85 % of IIb SNe explode with a rapidly rotating main-sequence companion. The observed luminosity distribution favours fairly inefficient mass accretion and failed explosions of the most massive stripped stars. The companion detection fraction broadly matches predictions, given the imaging depth, but appears elevated for SN IIb. In all but one non-detection, a faint undetected companion is the most likely scenario. The red apparently evolved companions in a few SN Ib/c may result from strong interaction with the ejecta, expected in $\sim 12~\%$ of them. Companion demographics offer a powerful independent probe of SESN progenitor systems, with the current sample disfavouring efficient accretion and supporting Wolf–Rayet non-explodability. Larger companion samples and follow-up studies will further clarify binary pathways to SESNe, serving as benchmarks for transient surveys.

  PublisherOA PDFDOI

• A new long gamma-ray burst formation pathway at solar metallicity

  DIGITAL.CSIC (Spanish National Research Council (CSIC)) · 2025-02-13

  preprintOpen access

  Context. Long gamma-ray bursts (LGRBs) are generally observed in low-metallicity environments. However, 10 to 20 per cent of LGRBs at redshift $z<2$ are associated with near-solar to super-solar metallicity environments, remaining unexplained by traditional LGRB formation pathways that favour low metallicity progenitors. Aims. In this work, we propose a novel formation channel for LGRBs that is dominant at high metallicities. We explore how a stripped primary star in a binary can be spun up by a second, stable reverse-mass-transfer phase, initiated by the companion star. Methods. We use POSYDON, a state-of-the-art population synthesis code that incorporates detailed single- and binary-star mode grids, to investigate the metallicity dependence of the stable reverse-mass-transfer LGRB formation channel. We determine the available energy to power an LGRB from the rotational profile and internal structure of a collapsing star, and investigate how the predicted rate density of the proposed channel changes with different star formation histories and criteria for defining a successful LGRB. Results. Stable reverse mass transfer can produce rapidly rotating, stripped stars at collapse. These stars retain enough angular momentum to account for approximately 10-20% of the observed local LGRB rate density, under a reasonable assumption for the definition of a successful LGRB. However, the local rate density of LGRBs from stable reverse mass transfer can vary significantly, between 1 and 100 Gpc$^{-3}$ yr$^{-1}$, due to strong dependencies on cosmic star formation rate and metallicity evolution, as well as the assumed criteria for successful LGRBs.

  PublisherDOI

Frequent coauthors

• Konstantinos Kovlakas

  78 shared

• Tassos Fragos

  University of Geneva

  72 shared

• Emmanouil Zapartas

  National Observatory of Athens

  61 shared

• Simone S. Bavera

  51 shared

• A. Zezas

  Center for Astrophysics Harvard & Smithsonian

  49 shared

• Devina Misra

  47 shared

• Kyle A. Rocha

  47 shared

• Katelyn Breivik

  45 shared

Education

• PhD, Astronomy

  Columbia University

  2015

• BA, Physics

  Northwestern University

  2009