arXiv subjects

Peter Shawhan

Publications and source records attributed to Peter Shawhan.

At least 19 recordsLinked to original sources

arXiv2026

4th TDAMM Workshop White Paper

Time-Domain and Multi-Messenger Astrophysics (TDAMM) is entering a new era in which the rate and diversity of transient discoveries will grow rapidly across electromagnetic, gravitational-wave, neutrino, and cosmic-ray facilities. The scientific return from these investments will increasingly depend not on discovery alone, but on the ability to identify, prioritize, and coordinate follow-up observations across a heterogeneous and globally distributed network of observatories. This white paper summarizes the outcomes of the Fourth TDAMM Workshop and assesses the near-term discovery landscape, the infrastructure and tools that support coordinated observations, and the technical, policy, and capability gaps that may limit future progress. The workshop identified three principal challenges: insufficiently scalable and interoperable alert and coordination infrastructure, policies that impede rapid multi-facility observations and rare-event science, and the potential loss of critical high-energy, rapid-response, and spectroscopic capabilities. The white paper identifies the need for sustained support for alert distribution, brokers, standardized observatory metadata, cross-facility coordination platforms, and unified follow-up repositories; expanded joint observing opportunities and funding mechanisms for coordinated analysis; and strategic investment in future TDAMM facilities. The white paper also present a framework for community observing plans that would establish pre-coordinated responses to rare, high-impact events, supported by transparent governance, immediate public data release, and regular community revision. Science overviews and detailed observing strategies are provided for gamma-ray bursts, tidal disruption events, X-ray binaries, novae, supernovae, magnetars, compact binary mergers, and high-energy neutrino sources.

astro-ph.HE↗

arXiv2025

Exploring Direct Detection of Massive Particles Using Wave Propagation from Gravitational Coupling with a Wire Under Tension

We investigate the feasibility of detecting galactic orbit dark matter passing through Earth by measuring its gravitational coupling with a wire under tension. We do so by exploring the transverse and longitudinal waves induced on the wire to detect a massive particle passing within $\sim 1$ m of the wire. The particle's $r^{-2}$ interaction with the wire provides an initial momentum which develops into a propagating wave carrying a distinctive time dependent displacement. Most interestingly, we find that both transverse and longitudinal waves develop with unique profiles, allowing for a full, three dimensional reconstruction of the particle's trajectory and its mass over velocity ratio. We find that, at interaction distances of 0.1 to 100 mm with a 90 micron diameter copper beryllium wire, Planck scale dark matter with mass $\sim 10^{19}$ GeV/$c^2$ would create immeasurable displacements on the scale of $10^{-24}$ to $10^{-26}$ m. In order to create displacements detectable by modern, commercially available, displacement sensors on the nanometer scale we require dark matter with a particle mass greater than $4 \times 10^7$ kg ($\sim 2 \times 10^{32}$ GeV/$c^2$). This is outside the upper limit of the Planck scale by 13 orders of magnitude and would also have such a low particle flux that a detection event would be implausible. Finally, we perform a similar analysis for a charged wire and an elementary charged particle with their electrostatic interaction, finding that a sufficiently slow charged particle would produce a transverse displacement comparable to the sensitivity of currently available sensors.

astro-ph.CO↗

arXiv2025

Multidisciplinary Science in the Multimessenger Era

Astrophysical observations of the cosmos allow us to probe extreme physics and answer foundational questions on our universe. Modern astronomy is increasingly operating under a holistic approach, probing the same question with multiple diagnostics including how sources vary over time, how they appear across the electromagnetic spectrum, and through their other signatures, including gravitational waves, neutrinos, cosmic rays, and dust on Earth. Astrophysical observations are now reaching the point where approximate physics models are insufficient. Key sources of interest are explosive transients, whose understanding requires multidisciplinary studies at the intersection of astrophysics, gravity, nuclear science, plasma physics, fluid dynamics and turbulence, computation, particle physics, atomic, molecular, and optical science, condensed matter and materials science, radiation transport, and high energy density physics. This white paper provides an overview of the major scientific advances that lay at the intersection of physics and astronomy and are best probed through time-domain and multimessenger astrophysics, an exploration of how multidisciplinary science can be fostered, and introductory descriptions of the relevant scientific disciplines and key astrophysical sources of interest.

astro-ph.HE↗

arXiv2023

A general approach to backaction-evading receivers with magnetomechanical and electromechanical sensors

Today's mechanical sensors are capable of detecting extremely weak perturbations while operating near the standard quantum limit. However, further improvements can be made in both sensitivity and bandwidth when we reduce the noise originating from the process of measurement itself -- the quantum-mechanical backaction of measurement -- and go below this 'standard' limit, possibly approaching the Heisenberg limit. One of the ways to eliminate this noise is by measuring a quantum nondemolition variable such as the momentum in a free-particle system. Here, we propose and characterize theoretical models for direct velocity measurement that utilize traditional electric and magnetic transducer designs to generate a signal while enabling this backaction evasion. We consider the general readout of this signal via electric or magnetic field sensing by creating toy models analogous to the standard optomechanical position-sensing problem, thereby facilitating the assessment of measurement-added noise. Using simple models that characterize a wide range of transducers, we find that the choice of readout scheme -- voltage or current -- for each mechanical detector configuration implies access to either the position or velocity of the mechanical sub-system. This in turn suggests a path forward for key fundamental physics experiments such as the direct detection of dark matter particles.

quant-ph↗

arXiv2022

The All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) Mission Concept

The All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) is designed to identify and characterize gamma rays from extreme explosions and accelerators. The main science themes include: supermassive black holes and their connections to neutrinos and cosmic rays; binary neutron star mergers and the relativistic jets they produce; cosmic ray particle acceleration sources including Galactic supernovae; and continuous monitoring of other astrophysical events and sources over the full sky in this important energy range. AMEGO-X will probe the medium energy gamma-ray band using a single instrument with sensitivity up to an order of magnitude greater than previous telescopes in the energy range 100 keV to 1 GeV that can be only realized in space. During its three-year baseline mission, AMEGO-X will observe nearly the entire sky every two orbits, building up a sensitive all-sky map of gamma-ray sources and emission. AMEGO-X was submitted in the recent 2021 NASA MIDEX Announcement of Opportunity.

astro-ph.IM↗

arXiv2022

The Future of Gamma-Ray Experiments in the MeV-EeV Range

Gamma-rays, the most energetic photons, carry information from the far reaches of extragalactic space with minimal interaction or loss of information. They bring messages about particle acceleration in environments so extreme they cannot be reproduced on earth for a closer look. Gamma-ray astrophysics is so complementary with collider work that particle physicists and astroparticle physicists are often one in the same. Gamma-ray instruments, especially the Fermi Gamma-ray Space Telescope, have been pivotal in major multi-messenger discoveries over the past decade. There is presently a great deal of interest and scientific expertise available to push forward new technologies, to plan and build space- and ground-based gamma-ray facilities, and to build multi-messenger networks with gamma rays at their core. It is therefore concerning that before the community comes together for planning exercises again, much of that infrastructure could be lost to a lack of long-term planning for support of gamma-ray astrophysics. Gamma-rays with energies from the MeV to the EeV band are therefore central to multiwavelength and multi-messenger studies to everything from astroparticle physics with compact objects, to dark matter studies with diffuse large scale structure. These goals and new discoveries have generated a wave of new gamma-ray facility proposals and programs. This paper highlights new and proposed gamma-ray technologies and facilities that have each been designed to address specific needs in the measurement of extreme astrophysical sources that probe some of the most pressing questions in fundamental physics for the next decade. The proposed instrumentation would also address the priorities laid out in the recent Astro2020 Decadal Survey, a complementary study by the astrophysics community that provides opportunities also relevant to Snowmass.

astro-ph.HE↗

arXiv2021

Exploring the MeV Sky with a Combined Coded Mask and Compton Telescope: The Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO)

The sky at MeV energies is currently poorly explored. Here we present an innovative mission concept that builds on and improves past and currently proposed missions at such energies. We outline the motivations for combining a coded mask and a Compton telescope and we define the scientific goals of such a mission. The Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO) is a novel concept for a next-generation telescope covering hard X-ray and soft gamma-ray energies. The potential and importance of this approach that bridges the observational gap in the MeV energy range are presented. With the unprecedented angular resolution of the coded mask telescope combined with the sensitive Compton telescope, a mission such as GECCO can disentangle the discrete sources from the truly diffuse emission. Individual Galactic and extragalactic sources are detected. This also allows to understand the gamma-ray Galactic center excess and the Fermi Bubbles, and to trace the low-energy cosmic rays, and their propagation in the Galaxy. Nuclear and annihilation lines are spatially and spectrally resolved from the continuum emission and from sources, addressing the role of low-energy cosmic rays in star formation and galaxy evolution, the origin of the 511 keV positron line, fundamental physics, and the chemical enrichment in the Galaxy. Such an instrument also detects explosive transient gamma-ray sources, which enable identifying and studying the astrophysical objects that produce gravitational waves and neutrinos in a multi-messenger context. By looking at a poorly explored energy band it also allows discoveries of new astrophysical phenomena.

astro-ph.HE↗

arXiv2020

Can we use next-generation gravitational wave detectors for terrestrial precision measurements of Shapiro delay?

Shapiro time delay is one of the fundamental tests of general relativity and post-Newtonian theories of gravity. Consequently, its measurements can be used to probe the parameter $γ$ which is related to spacetime curvature produced by a unit mass in the post-Newtonian formalism of gravity. To date all measurements of time delay have been conducted on astronomical scales. It was asserted in 2010 that gravitational wave detectors on Earth could be used to measure Shapiro delay on a terrestrial scale via massive rotating systems. Building on that work, we consider how measurements of Shapiro delay can be made using next-generation gravitational wave detectors. We perform an analysis for measuring Shapiro delay with the next-generation gravitational wave detectors Cosmic Explorer and Einstein Telescope to determine how precisely the effect can be measured. Using a rotating mass unit design, we find that Cosmic Explorer and Einstein Telescope can measure the Shapiro delay signal with amplitude signal to noise ratios upwards of $\sim28 $ and $\sim43$ in 1 year of integration time, respectively. By measuring Shapiro delay with this technique, next-generation interferometers will allow for terrestrial measurements of $γ$ in the paramaterized post-Newtonian formalism of gravity with sub-percent precision.

gr-qc↗

arXiv2020

Back-action evading impulse measurement with mechanical quantum sensors

The quantum measurement of any observable naturally leads to noise added by the act of measurement. Approaches to evade or reduce this noise can lead to substantial improvements in a wide variety of sensors, from laser interferometers to precision magnetometers and more. In this paper, we develop a measurement protocol based upon pioneering work by the gravitational wave community which allows for reduction of added noise from measurement by coupling an optical field to the momentum of a small mirror. As a specific implementation, we present a continuous measurement protocol using a double-ring optomechanical cavity. We demonstrate that with experimentally-relevant parameters, this protocol can lead to significant back-action noise evasion, yielding measurement noise below the standard quantum limit over many decades of frequency.

quant-ph↗

arXiv2019

BurstCube: Concept, Performance, and Status

The first simultaneous detection of a short gamma-ray burst (SGRB) with a gravitational-wave (GW) signal ushered in a new era of multi-messenger astronomy. In order to increase the number of SGRB-GW simultaneous detections, we need full sky coverage in the gamma-ray regime. BurstCube, a CubeSat for Gravitational Wave Counterparts, aims to expand sky coverage in order to detect and localize gamma-ray bursts (GRBs). BurstCube will be comprised of 4 Cesium Iodide scintillators coupled to arrays of Silicon photo-multipliers on a 6U CubeSat bus (a single U corresponds to cubic unit $\sim$10 cm $\times$ 10 cm $\times$ 10 cm) and will be sensitive to gamma-rays between 50 keV and 1 MeV, the ideal energy range for GRB prompt emission. BurstCube will assist current observatories, such as $Swift$ and $Fermi$, in the detection of GRBs as well as provide astronomical context to gravitational wave events detected by Advanced LIGO, Advanced Virgo, and KAGRA. BurstCube is currently in its development and testing phase to prepare for launch readiness in the fall of 2021. We present the mission concept, preliminary performance, and status.

astro-ph.IM↗

arXiv2019

Multi-Messenger Astrophysics Opportunities with Stellar-Mass Binary Black Hole Mergers

The conventional view of stellar-mass binary black hole (sBBH) mergers is that there should not be enough matter present to produce a detectable electromagnetic transient. However, there ARE a number of mechanisms for producing such a counterpart through accretion of matter from various reserves, charged black holes, or interactions with magnetic or exotic fields. After reviewing these mechanisms, we describe what we can learn from multi-messenger observations of sBBH mergers in the areas of stellar evolution and compact binary formation, cosmological measurements, searches for charged black holes, and tests of general relativity and fundamental physics. We end with some remarks about the need to support both observing capabilities and modeling in the next decade and beyond.

astro-ph.HE↗

arXiv2018

Multi-Messenger Astrophysics: Harnessing the Data Revolution

The past year has witnessed discovery of the first identified counterparts to a gravitational wave transient (GW 170817A) and a very high-energy neutrino (IceCube-170922A). These source identifications, and ensuing detailed studies, have realized longstanding dreams of astronomers and physicists to routinely carry out observations of cosmic sources by other than electromagnetic means, and inaugurated the era of "multi-messenger" astronomy. While this new era promises extraordinary physical insights into the universe, it brings with it new challenges, including: highly heterogeneous, high-volume, high-velocity datasets; globe-spanning cross-disciplinary teams of researchers, regularly brought together into transient collaborations; an extraordinary breadth and depth of domain-specific knowledge and computing resources required to anticipate, model, and interpret observations; and the routine need for adaptive, distributed, rapid-response observing campaigns to fully exploit the scientific potential of each source. We argue, therefore, that the time is ripe for the community to conceive and propose an Institute for Multi-Messenger Astrophysics that would coordinate its resources in a sustained and strategic fashion to efficiently address these challenges, while simultaneously serving as a center for education and key supporting activities. In this fashion, we can prepare now to realize the bright future that we see, beyond, through these newly opened windows onto the universe.

astro-ph.IM↗

arXiv2017

BurstCube: A CubeSat for Gravitational Wave Counterparts

BurstCube will detect long GRBs, attributed to the collapse of massive stars, short GRBs (sGRBs), resulting from binary neutron star mergers, as well as other gamma-ray transients in the energy range 10-1000 keV. sGRBs are of particular interest because they are predicted to be the counterparts of gravitational wave (GW) sources soon to be detectable by LIGO/Virgo. BurstCube contains 4 CsI scintillators coupled with arrays of compact low-power Silicon photomultipliers (SiPMs) on a 6U Dellingr bus, a flagship modular platform that is easily modifiable for a variety of 6U CubeSat architectures. BurstCube will complement existing facilities such as Swift and Fermi in the short term, and provide a means for GRB detection, localization, and characterization in the interim time before the next generation future gamma-ray mission flies, as well as space-qualify SiPMs and test technologies for future use on larger gamma-ray missions. The ultimate configuration of BurstCube is to have a set of $\sim10$ BurstCubes to provide all-sky coverage to GRBs for substantially lower cost than a full-scale mission.

astro-ph.IM↗

arXiv2016

Simultaneous Observations of Giant Pulses from Pulsar PSR B0950+08 at 42 MHz and 74 MHz

We report the detection of giant pulse emission from PSR~B0950+08 in 12 hours of observations made simultaneously at 42~MHz and 74~MHz, using the first station of the Long Wavelength Array, LWA1. We detected 275 giant pulses (in 0.16\% of the pulse periods) and 465 giant pulses (0.27\%) at 42 and 74~MHz, respectively. The pulsar is weaker and produces less frequent giant pulses than at 100~MHz. Here, giant pulses are taken as having $\geq$ 10 times the flux density of an average pulse; their cumulative distribution of pulse strength follows a power law, with a index of $-$4.1 at 42~MHz and $-$5.1 at 74~MHz, which is much less steep than would be expected if we were observing the tail of a Gaussian distribution of normal pulses. We detected no other transient pulses in a wide dispersion measure range from 1 to 5000~pc~cm$^{-3}$. There were 128 giant pulses detected within in the same periods from both 42 and 74~MHz, which means more than half of them are not generated in a wide band. We use CLEAN-based algorithm to analyze the temporal broadening and conclude that the scattering effect from the interstellar medium can not be observed. We calculated the altitude $r$ of the emission region using the dipolar magnetic field model. We found $r$(42~MHz) = 29.27~km ($0.242\%$ of $R_{LC}$) and $r$(74~MHz) = 29.01~km ($0.240\%$ of $R_{LC}$) for the average pulse, while for giant pulses, $r$(42~MHz) = 29.10~km ($0.241\%$ of $R_{LC}$) and $r$(74~MHz) = 28.95~km ($0.240\%$ of $R_{LC}$). Giant pulses, which have a double-peak structure, have a smaller mean peak-to-peak separation compared to the average pulse.

astro-ph.HE↗

arXiv2015

Multi-messenger astronomy of gravitational-wave sources with flexible wide-area radio transient surveys

We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of gravitational waves and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, LOFAR and MWA. We find that a broad range of models may be tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a $\usim 30$ second time window and $\usim 200 \mendash 500 \punits{deg}^{2}$ sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a \emph{prompt} radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of $\usim 2$. For some models, we also map the parameter space that may be constrained by non-detections.

astro-ph.HE↗

arXiv2015

Planned search for LIGO-GBM coincidence in the first advanced LIGO data run

In the fall of 2015 the first scientific observing run (O1) of the advanced LIGO detectors will be conducted. Based on the recent commissioning progress at the LIGO Hanford and Livingston sites, the gravitational wave detector range for a neutron star binary inspiral is expected to be of order 60 Mpc. We describe here our planning for an O1 search for coincidence between a LIGO gravitational wave detection and a gamma-ray signal from the Fermi Gamma-ray Burst Monitor. Such a coincidence would constitute measurement of an electromagnetic counterpart to a gravitational wave signal, with significant corresponding scientific benefits, including revealing the central engine powering the gamma-ray burst, enhanced confidence in the event as a genuine astrophysical detection, and a determination of the relative speed of the photon and graviton.

astro-ph.HE↗

arXiv2015

Observations of Giant Pulses from Pulsar PSR B0950+08 using LWA1

We report the detection of giant pulse emission from PSR B0950+08 in 24 hours of observations made at 39.4 MHz, with a bandwidth of 16 MHz, using the first station of the Long Wavelength Array, LWA1. We detected 119 giant pulses from PSR B0950+08 (at its dispersion measure), which we define as having SNRs at least 10 times larger than for the mean pulse in our data set. These 119 pulses are 0.035% of the total number of pulse periods in the 24 hours of observations. The rate of giant pulses is about 5.0 per hour. The cumulative distribution of pulse strength $S$ is a steep power law, $N(>S)\propto S^{-4.7}$, but much less steep than would be expected if we were observing the tail of a Gaussian distribution of normal pulses. We detected no other transient pulses in a dispersion measure range from 1 to 90 pc cm$^{-3}$, in the beam tracking PSR B0950+08. The giant pulses have a narrower temporal width than the mean pulse (17.8 ms, on average, vs. 30.5 ms). The pulse widths are consistent with a previously observed weak dependence on observing frequency, which may be indicative of a deviation from a Kolmogorov spectrum of electron density irregularities along the line of sight. The rate and strength of these giant pulses is less than has been observed at $\sim$100 MHz. Additionally, the mean (normal) pulse flux density we observed is less than at $\sim$100 MHz. These results suggest this pulsar is weaker and produces less frequent giant pulses at 39 MHz than at 100 MHz.

astro-ph.HE↗

arXiv2014

GR 20 Parallel Session A3: Modified Gravity

This is the contribution representing Parallel Session A3, on Modified Gravity, in the Proceedings of the GR 20 Conference (July 2013, Warszawa, Poland). It consists of three invited chapters, selected by the Session Chair (P.H.) to represent the broad spectrum of topics discussed in the Session, which ranged from theoretical and phenomenological, to experimental, observational and numerical aspects of gravity. The three chapters are "Einstein-Aether Theory: Thermodynamics of Universal Horizons" by Arif Mohd, "The Curious Case of Conformal Anomalies in Horava-Lifshitz Gravity" by Charles M. Melby-Thompson, and "Detectability of Scalar Gravitational-Wave Bursts with LIGO and Virgo" by Peter Shawhan.

gr-qc↗