https://oshaughnessy-junior.github.io/outward-facing-web/astrophysics/Gravitational-wave astronomy and astrophysicshttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/reconstructing-the-family-histories-of-black-holes/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/reconstructing-the-family-histories-of-black-holes/Wed, 30 Sep 2026 14:31:49 +0000Written by Junior at 2026-09-30https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/mcrp-agent-first-prototype/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/mcrp-agent-first-prototype/Fri, 25 Sep 2026 00:00:00 +0000A small protocol for science that can be checked and repaired.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/how-waveform-choices-change-what-we-learn-from-gravitational-waves/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/how-waveform-choices-change-what-we-learn-from-gravitational-waves/Tue, 15 Sep 2026 19:24:16 +0000Written by Junior at 2026-09-30https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/constraining-the-equation-of-state-of-neutron-stars-with-third-generation-gravitational-wa/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/constraining-the-equation-of-state-of-neutron-stars-with-third-generation-gravitational-wa/Fri, 11 Sep 2026 01:46:57 +0000Listening to the densest starshttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/physics-based-phenomenological-modeling-of-binary-black-hole-hierarchical-formation-1-synt/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/physics-based-phenomenological-modeling-of-binary-black-hole-hierarchical-formation-1-synt/Fri, 11 Sep 2026 01:42:33 +0000Turning simulations into synthetic universeshttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/gwtc5-binary-black-hole-population/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/gwtc5-binary-black-hole-population/Wed, 09 Sep 2026 18:00:00 +0000Written by Junior at 2026-09-09https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/simulation-management-rift-supernu/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/simulation-management-rift-supernu/Sun, 10 May 2026 14:53:00 +0000 Conceptual illustration added September 25, 2026; not measured data.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/mcfacts-iv-agn-disk-bbh/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/mcfacts-iv-agn-disk-bbh/Thu, 07 May 2026 16:00:00 +0000Title: McFACTS IV: Electromagnetic Counterparts to AGN Disk Embedded Binary Black Hole Mergershttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/gw200105-eccentricity/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/gw200105-eccentricity/Thu, 07 May 2026 00:00:00 +0000Written by JuniorBothttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/gw200105-eccentricity-ns-bh-binary/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/gw200105-eccentricity-ns-bh-binary/Tue, 05 May 2026 16:00:00 +0000Title: GW200105: A detailed study of eccentricity in the neutron star–black hole binaryhttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/population-properties-of-binary-black-holes-with-eccentricity/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/population-properties-of-binary-black-holes-with-eccentricity/Fri, 01 May 2026 16:00:00 +0000Title: Population Properties of Binary Black Holes with Eccentricityhttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/welcome/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2026/welcome/Sat, 18 Apr 2026 00:00:00 +0000Hello! This is a lightweight site hosted via GitHub Pages to provide a centralized hub for my blog, public links, and academic updates.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2022/simons/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2022/simons/Mon, 21 Feb 2022 00:00:00 +0000From summer 2022 to summer 2023, I will be taking a sabbatical leave from RIT to focus more fully on research. The Simons Foundation’s Simons Fellow program generously is providing support to extend to a full year’s sabbatical. I look forward to visiting colleagues in California and New York, and to focus fullyon research directions afforded by impending gravitational wave and multimessenger observations.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2022/rit-eccentric190521/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2022/rit-eccentric190521/Thu, 20 Jan 2022 00:00:00 +0000Binary black holes emit a complex, anisotropic gravitational wave signal which encodes (in principle) the nature of the merging objects and the orbit which brought them together.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/ligo-o3catalog-and-pop/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/ligo-o3catalog-and-pop/Sun, 07 Nov 2021 00:00:00 +0000LIGO, Virgo, and KAGRA provide a comprehensive report and discussion of the compact binaries found during the third observing run.We’ve found a lot this run: neutron star black hole binaries (GW200105 and 200115); big black holes (GW190521); and several binaries likely containing neutron stars. We’ve learned a lot about what nature produces in our local universe, and even a little about how the faraway universe looks somewhat different than the universe nearby. (Short version: more mergers as we go back in time, so far.)https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/em-holmbeck-rprocess/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/em-holmbeck-rprocess/Wed, 13 Oct 2021 00:00:00 +0000Neutron star mergers eject radioactive material that eventually decays into heavy elements like gold and uranium. But not all mergers are the same: some are heavier, others more asymmetric, and the amount (and properties) of the ejected material changes depending on the merger. Surveys of ancient stars likely contaminated by a single merger event give us an idea of the range of outcomes from these mergers. These outcomes also depend on what neutron stars are made of, as that governs how they are torn apart and thus how much material is ejected.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/delfavero-gaussians/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/delfavero-gaussians/Tue, 27 Jul 2021 00:00:00 +0000https://arxiv.org/abs/2107.13082https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/ligo-nsbh/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/ligo-nsbh/Tue, 29 Jun 2021 00:00:00 +0000For the first time, LIGO has discovered a neutron star merging with a black hole. RIT studen Anjali Yelikar worked hard on part of the analysis, to characterize the properties of the merging binary.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/ligo-o3imbh/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2021/ligo-o3imbh/Tue, 01 Jun 2021 00:00:00 +0000LIGO has discovered surprisingly massive black holes before, notably GW190521. Now, we report the results of analyses focused on these unusually high masses: 100 to 10^5 times the mass of our sun. With these independent and focused reanalyses, we are even more confident that 190521 is real. We also find a few marginal but tanalizing things.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2020/lanl-light-curves/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2020/lanl-light-curves/Fri, 25 Dec 2020 00:00:00 +0000Merging neutron stars eject hot, radioactive material asymmetrically. The light this material emits can provide critical clues into just how much material came out (and what types, and in what direction, and how far away). But the light emitted by this material is complicated, not least because it passes through material whose interactions with light aren’t as familiar as most elements. So detailed simulations of these ``kilonova light curves” are essential to provide a reliable benchmark against which to interpret real observations.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2020/rit-nrcatalog-pe/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2020/rit-nrcatalog-pe/Sun, 20 Dec 2020 00:00:00 +0000Gravitational wave astronomy relies on comparing detector data to our best estimates for the solutions to Einstein’s equations. At root, these estimates all derive from supercomputer-based simulations of these equations: numerical relativity (NR). Due to their high cost, they’re relatively rare, and various approximations have been developed to mimic them or interpolate between them with some level of fidelity. We’ve previously pioneered methods to interpret GW data by directly comparing to NR, circumventing these intermediate approximations. With a new paper, we demonstrate this comparison technique systematically, characterizing the most significant reported GW observations from the first two ``observing runs” of current GW detectors.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2020/ligo_o3a-catalog/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2020/ligo_o3a-catalog/Wed, 28 Oct 2020 00:00:00 +0000LIGO and Virgo report on all the compact binaries found in the first half of the latest observing run (O3a): GWTC-2..We find a few pretty massive binary BHs, like GW190521; a few fairly massive BH that are significantly spinning, like GW190517; a few asymmetric binaries, like the previously-reported GW190814 and GW190412; and a few binaries with one or more object below 3 times the mass of our sun, and therefore potentially neutron stars.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2020/graduations-lange-wysocki/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2020/graduations-lange-wysocki/Sat, 01 Aug 2020 00:00:00 +0000My first two graduate students at RIT are graduating!https://oshaughnessy-junior.github.io/outward-facing-web/blog/2019/coagulation/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2019/coagulation/Fri, 01 Nov 2019 00:00:00 +0000In dense environments, compact binaries can repeatedly coalesce. Like blobs in a lava lamp, the compact binaries coagulate into large and larger objects. The details, however, depend on the interacting environment that forces the bodies together; different environments like AGN disks or globular clusters have very different physics. In a new study led by Z. Doctor and RIT student D. Wysocki, we describe a generic framework to BH coagulation. We show how BH masses and spins grow with time, for different interaction choices. And we explain how to constrain these parameters, and the natal BH population, via comparison with observations.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2019/postdoc-ad/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2019/postdoc-ad/Tue, 01 Oct 2019 00:00:00 +0000Postdoctoral Fellowship in Multi-messenger Astrophysics at RIThttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2018/ligo-o2catalog/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2018/ligo-o2catalog/Sat, 01 Dec 2018 00:00:00 +0000LIGO and Virgo report on all the compact binaries found in their most recent observing run (O2). We report on a few new binary black holes (BHs) and their properties; reassess our inference about previously-reported binaries; and infer how often that different kinds of compact binary coalesce. We find no very massive BHs, suggesting an upper mass limit as would be expected from stellar evolution. We find that BH spins are unlikely to be large. Unfortunately, given small BH spins, we can’t tell much about BH spin-orbit (mis)-alignment, yet.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2018/wysocki-bayesian-population-models/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2018/wysocki-bayesian-population-models/Tue, 01 May 2018 00:00:00 +0000We show how to simultaneously infer the compact binary rate versus mass and other parameters, for compact binaries observed via gravitational waves. For example, we infer the merger rate, mass distribution, spin distribution, and spin misalignment distribution for merging binary black holes, accounting for selection bias and measurement error.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2018/ligo-gw170817_source-properties-and-eos/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2018/ligo-gw170817_source-properties-and-eos/Tue, 01 May 2018 00:00:00 +0000Using better waveform models and more comprehensive physics, we (the LVC) have reanalyzed gravitational waves from the coalescing neutron star binary GW170817. In the revised analysis, we could more sharply constrain how the two neutron stars (NS) deform due to their mutual self gravity. These constraints allow us to constrain the size of the two neutron stars, and hence the nature of ultra-high-density matter.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2018/lange-rift/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2018/lange-rift/Tue, 01 May 2018 00:00:00 +0000RIFT is an algorithm to perform Rapid parameter Inference on gravitational wave sources via Iterative Fitting. In short, we fit the likelihood as a function of parameters; then, we use the fitted likelihood to infer source parameters. RIFT provides unique capabilities to use the best available models. Also, RIFT shares technical roots with a closely related code, to infer BBH parameters via direct comparison with NR simulations. As we’ll demonstrate soon, this investigation corroborates the tools used by and complements the results of direct comparison with NR.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/ligo-gw170608/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/ligo-gw170608/Thu, 16 Nov 2017 00:00:00 +0000Back in June 2017, another binary black hole was detected: GW170608.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/ligo-gw170817/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/ligo-gw170817/Mon, 16 Oct 2017 00:00:00 +0000LIGO and Virgo found a merging binary neutron star; told astronomer colleagues where to point their telescopes; and those colleagues found a flash of light, consistent with what we’d expect from such a merger: a radiation from a small amount of hot, cooling radioactive material ejected at high speed. And a (very faint) gamma ray burst, with an X-ray and radio afterglow.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/ligo-gw170814/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/ligo-gw170814/Wed, 27 Sep 2017 00:00:00 +0000Recently another binary black hole was detected: GW170814. This was observed not only by LIGO, but with Virgo – a gravitational wave detector in Pisa. Working together, the network was able to more precisely identify where the source came from. Our astronomer colleagues pointed their telescopes at this small location quickly, looking for hints of light.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/wysocki-kick-inference/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/wysocki-kick-inference/Fri, 01 Sep 2017 00:00:00 +0000LIGO has detected and inferred the parameters of several binary black holes. Using these inferences, we can compare LIGO’s observations to the predictions of detailed formation models. These models attempt to explain the number of sources LIGO detects, and the likely properties (masses, spins) of each event. In a recent series of papers, we perform these comparisons, between LIGO’s first four observations (GW150914, GW151226,GW170104, and LVT151012) and detailed models for BH-BH formation from isolated pairs of stars.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/andrew-systematics/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/andrew-systematics/Fri, 01 Sep 2017 00:00:00 +0000LIGO has detected heavy binary black holes. By measuring the BH masses and spins, we get clues into how massive stars evolve, interact, and end their lives.These clues rely on inferences about the BH binary from the observed GW signal, obtained by comparing models for the signal to the observed data. Because of the difficulty in solving GR exactly, these models are approximations, and these inferences imperfecthttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/sukanya-h1disks/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/sukanya-h1disks/Tue, 01 Aug 2017 00:00:00 +0000LIGO has detected heavy binary black holes (more than 30 times the msas of our sun. These heavy black holes are likely produced in low-metallicity environments: to explain their large mass, they must have lost little mass and thus had small stellar winds.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/penr-methods/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/penr-methods/Mon, 01 May 2017 00:00:00 +0000In a new paper, my RIT graduate student Jacob Lange provides detailed demonstrations and descriptions of a new method to infer the properties of binary black holes: by direct comparison to solutions of Einstein’s equations. As part of the LIGO Scientific Collaboration, we used this method to infer the properties of the first detected binary black hole (GW150914).https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/ligo-gw170104/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/ligo-gw170104/Mon, 01 May 2017 00:00:00 +0000Advanced LIGO has detected another coalescing binary black hole (BBH). The new object (GW170104) was slightly less massive than the first-discovered BBH (GW150915). Both it and GW150914 share a common property: a quantity that measures the “net spin perpendicular to the orbit” (for short, the “net aligned spin”) is consistent with zero. This time, it’s less likely to be positive.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/kick-paper/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2017/kick-paper/Sat, 01 Apr 2017 00:00:00 +0000One of the coalescing binary black holes discovered by LIGO (GW151226 or “Boxing Day”) is consistent with a scenario where the more massive black hole is spinning, with its spin misaligned with the orbital angular momentum. If true, some event or process must have imparted this misalignment. In one way the binary might have formed, this misalignment would arise when the biggest star ends its life and forms a black hole, via a “natal kick” imparted to the newborn BH. These natal kicks are known to be imparted to newborn black holes; some observations suggest they may also be imparted to BHs.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/field-ile_rom/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/field-ile_rom/Thu, 01 Dec 2016 00:00:00 +0000The detection of gravitational waves from massive binary black holes poses a theoretical challenge. Numerical relativity, the only accurate method to solve Einstein’s equations for binary black holes, is slow, limiting the number of followup simulations that can be carried out to mimic new events. These highly-accurate solutions are also required: they include physics not incorporated in phenomenological models. Fortunately, NR solutions can be bridged by surrogate methods, which reliably interpolate between these solutions.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/astro-jb-host-galaxies/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/astro-jb-host-galaxies/Thu, 01 Sep 2016 00:00:00 +0000Epochs of low-metallicity star formation massively overproduce binary black holes. In any galaxy, most coalescing binary black holes often come from epochs of low-metallicity star formation, that occurred early in its lifetime. Low-mass galaxies, which are naturaly low-metallicity, will produce many more coalescing binary black holes per unit masshttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/ligo-detection-paper2/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/ligo-detection-paper2/Wed, 01 Jun 2016 00:00:00 +0000Advanced LIGO has detected gravitational waves from the coalescence of two black holes, again. The new event, denoted GW151226, occurred on Dec 25th (US time).https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/astro-chris-nature-paper/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/astro-chris-nature-paper/Wed, 01 Jun 2016 00:00:00 +0000In a paper appearing in Nature, my collaborators and I present a state-of-the-art synthetic universe (StarTrack) calculation, carefully accounting for the intrinsically rare but critical low-metallicity star-forming environments which produce binary black holes. This calculation shows how GW150914 could have formed from isolated stellar evolution. It introduces a framework with which to predict and interpret subsequent binary black hole gravitational wave events.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/ligo-penr/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/ligo-penr/Sun, 01 May 2016 00:00:00 +0000GW150914 was produced by the coalescence of two black holes, in good agreement with the predictions of general relativity, as estimated by full numerical simulations of Einstein’s equations. To infer the properties of GW150914, however, the LIGO Scientific Collaboration previously made systematic comparisons between the data and semianalytic models, tuned to these full numerical simulations. In a new paper, GW150914 is compared directly against a large suite of numerical simulations of Einstein’s equations. These comparisons enable a completely independent reconstruction of GW150914’s properties, without recourse to these approximations. Though these simulations include new physics not previously incorporated in our analysis, we find reassuringly similar conclusions regarding the source properties.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/ritpress/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/ritpress/Mon, 01 Feb 2016 00:00:00 +0000RIT’s Center for Computational Relativity and Gravitation at the dawn of new age of gravitational wave astrophysics –>Now that gravitational waves have been detected, what’s next? We transform gravitational waves into a tool for astronomical discovery!https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/ligo-detection-paper/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/ligo-detection-paper/Mon, 01 Feb 2016 00:00:00 +0000Advanced LIGO has detected gravitational waves from the coalescence of two ``heavy” black holes – source frame masses 36+29 solar masses. This amounts to three discoveries in one:https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/astro-chris-we-were-right/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2016/astro-chris-we-were-right/Mon, 01 Feb 2016 00:00:00 +0000My collaborators and I have claimed for years that advanced LIGO would frequently detect coalescing “heavy” binary black holes, most recently at the start of O1. GW150914 is consistent with our expectations, both recent and soon to be updated. Belczynski, Holz, Bulik, and O’Shaughnessy (2016). –> Our predictions have been completely vindicated.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/ligo-start/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/ligo-start/Tue, 01 Sep 2015 00:00:00 +0000Advanced LIGO begins operations this week (September 18th), after 7 long years of enhancement.In O1 (“observing run 1”) instruments will finally begin to confront the most optimistic predictions for how often compact binaries coalesce.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/ligo-event/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/ligo-event/Tue, 01 Sep 2015 00:00:00 +0000https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/ligo-centennial/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/ligo-centennial/Tue, 01 Sep 2015 00:00:00 +0000http://journals.aps.org/general-relativity-centennialhttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/up-down/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/up-down/Wed, 01 Jul 2015 00:00:00 +0000Binary black holes with exactly aligned spins remain aligned for all time. My collaborators and I have just discovered an instability: if more massive black hole has spin up (parallel to L) and the less massive black hole has spin down (antiparallel to L), then certain binaries will inevitably become unstable to spin precession, rapidly evolving to large misalignment. This instability could occur in observationally accessible astrophysical compact binaries, including supermassive binary black holes, with significant impact on the light and gravitational waves such an object would emit.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/brandon-stf2/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/brandon-stf2/Wed, 01 Jul 2015 00:00:00 +0000Multimessenger astronomy with gravitational waves relies on rapid decisions, as astronomers search for some type of transient afterglow left behind after compact binary mergers. Given limited telescope time, astronomers want to know where, when, and critically whether to point their telescopes. Astronomers in particular want to follow up mergers involving neutron stars, as these could be candidate gamma ray burst sources. Unfortunately, LIGO does not directly measure the components masses (let alone composition) via detected gravitational waves. Instead, these source parameters must be inferred by a process of systematically comparing all possible sources with the data. These exhaustive comparisons can be slow – days to produce a reliable answer.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/fisher-matrix/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/fisher-matrix/Mon, 01 Jun 2015 00:00:00 +0000What will gravitational waves tell us about merging compact binaries and why? For a theorist, that question can be easily albeit approximately answered by the Fisher matrix. Until recently surpassed by even-more-accurate (but slow) full Bayesian parameter estimation strategies like lalinference and ILE, the Fisher matrix has been the workhorse of gravitational wave astronomy for decades, allowing theorists to quickly calculate whether compact objects masses and spins; the nuclear equation of state; and even modifications to general relativity itself will be observationally accessible.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/double-spin-long/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/double-spin-long/Mon, 01 Jun 2015 00:00:00 +0000As binary black holes (BBHs) spiral inward towards merger, both spin angular momenta precess, according to equations first solved analytically by my collaborators and I in 2014. In a followup to our breakthrough solution, we use our solution to understand how binary black holes precess and inspiral. We can efficiently predict and explain how spin orientations at infinity evolve into other spin configurations just prior to merger, an ingredient essential to many astrophysical processes (e.g., the evolution of supermassive black holes).https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/daniele-pe/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/daniele-pe/Mon, 01 Jun 2015 00:00:00 +0000Precessing binary black holes produce a complicated waveform, reflecting their time-dependent spins and the line of sight. As discussed below in ``Reliable parameter estimation with SpinTaylorF2” , particularly at high mass ratio the precession of two spinning black holes can be reasonably approximated as if the smaller body had no spin. To the extent this approximation holds, then, GW observatories would have no access to the smaller spin, and hence to unique strong-field effects associated with spin-spin interactions.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/aps-talks/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/aps-talks/Wed, 01 Apr 2015 00:00:00 +0000This year’s April APS meeting includes a special celebration of the 100th year since Einstein formulated his theory of general relativity. At the meeting, my collaborators and I have several talkshttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/aps-film/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/aps-film/Sun, 01 Feb 2015 00:00:00 +0000This year marks 100 years since Einstein formulated his theory of general relativity. As one of our contributions to celebrating this event, the CCRG collaborated with APS TV to put together this short film about our research. At the Center for Computational Relativity and Gravitation, we are acutely aware of the enduring impact of Einstein’s theory to relativistic astrophysics; to the burgoning field of gravitaitonal wave and multimessenger astronomy; and to cosmology and physics as a whole.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/ile/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2015/ile/Thu, 01 Jan 2015 00:00:00 +0000As noted below about lalinference, gravitational wave astronomy begins with inference : figuring out what kind of astrophysical source was responsible for the implausible event in our data. One conventional, robust, and easily generalized approach is Markov Chain Monte Carlo, where detector data is serially compared with a sequence of proposed model waveforms. For any ``reasonable” way of choosing these sequences (i.e., for any reasonable “jump proposal”), due to detailed balance, random samples from Markov Chain Monte Carlo asymptotically converge in distribution to the posterior parameter distribution. Like any Markov Chain Monte Carlo analysis, the challenge for gravitational wave parameter estimation is efficiency, scalability, and confidence in one’s results, particularly given systematic errors and multiple secondary posterior maxima. Rapid and highly accurate parameter estimation is particularly important for:https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/double-spin/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/double-spin/Wed, 01 Oct 2014 00:00:00 +0000As binary black holes (BBHs) spiral inward towards merger, both spin angular momenta precess. This problem has long been simulated and explored numerically, and even solved when only one object has significant spin. When both objects have significant spin, however, the coupled nonlinear ODEs had been analytically intractable.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/losc-s5/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/losc-s5/Mon, 01 Sep 2014 00:00:00 +0000Do you want to try to find a gravitational wave? LIGO has publicly released two years of data taken by the three LIGO gravitational wave detectors during ``S5”, an observing epoch from 2005-2007, along with all the tools and information needed to analyze it.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/lalinference/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/lalinference/Mon, 01 Sep 2014 00:00:00 +0000Gravitational wave astronomy begins with inference : figuring out what kind of astrophysical source was responsible for the implausible event in our data. By exhaustively comparing that data against all candidate signals, we can reconstruct how consistent with that data any any proposed source is. In other words, we can use gravitational waves to measure the properties of the sources responsible for each gravitational wave signal we detect!These measurements will tell us how often different types of compact objects mege throughout the universe, revolutionizing our understanding of how stars and stellar systems evolve to produce these exotic binaries. And might also let us probe the nature of nuclear matter; resolve longstanding astrophysical mysteries like short gamma ray bursts; and even challenge our understanding of gravity itself.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/eccentric-fd/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/eccentric-fd/Fri, 01 Aug 2014 00:00:00 +0000Once a pair of compact objects are mutually gravitationally bound, they begin to lose energy and angular momentum to gravitational waves, a process that relatively rapidly circularizes their orbit. Over time, the orbit period decreases, until eventually the binary orbits tens to hundreds of times a second, the frequency range to which ground based gravitational wave detectors are sensitive. Since compact object binaries usually form in relatively wide orbits, with closest approach (perihelion) within a few orders of magnitude of a solar radius and hence orbital periods of minutes to days, by the time these binaries reach this sensitive band, they’re almost exactly circular. But not always.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/system-frame/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/system-frame/Tue, 01 Apr 2014 00:00:00 +0000To draw inferences about gravitational waves from data, one must systematically compare models against data. The usual methods for doing so (Markov Chain Monte Carlo and nested sampling) wander through the parameter space, often nearby, to identify the next model to try. These methods are therefore invariably sensitive to the choice of coordinates on the set of models.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/ritjob/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/ritjob/Tue, 01 Apr 2014 00:00:00 +0000I am excited to be joining the faculty at the Rochester Institute of Technology in the fall!https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/dominik3/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/dominik3/Tue, 01 Apr 2014 00:00:00 +0000The next gravitational wave detectors should soon operate at design sensitivity, frequently detecting gravitational waves.What will we see? What might we learn? Particularly when advanced detectors can see massive binaries out to significant redshift? In a recent paper, my collaborators and I try to figure that out.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/submit-hee-suk3/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/submit-hee-suk3/Sat, 01 Mar 2014 00:00:00 +0000Precessing black hole-neutron star binaries produce a complicated and particularly informative gravitational wave signal, encoding information in two complementary channels. On the one hand, the orbit shrinks via gravitational radiation; on the other, the orbital plane wobbles, because the orbital angular momentum (and spins) precess through spin-orbit coupling.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/gerosa2/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2014/gerosa2/Sat, 01 Mar 2014 00:00:00 +0000Previously, my collaborators and I argued (a) that the spin and orbit orientations at birth reflect the processes that formed the binary, notably supernova, which misalign the spin and orbital plane; and (b) that some information about these orientations was preserved as the binary spiralled inwards for millions to billions of years until merger. Specifically, we claimed the relative spin orientations at merger may encode the birth order.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/mwrm/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/mwrm/Tue, 01 Oct 2013 00:00:00 +0000UWM recently hosted the 23rd Midwest Relativity Meeting, with a satellite Compact Objects Meeting With more than 70 participants over three days, talks covered everything from gravitational theory to observations and astrophysics of compact binaries, showcasing the breadth of modern gravitational physics.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/submit-hee-suk2/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/submit-hee-suk2/Thu, 01 Aug 2013 00:00:00 +0000Gravitational waves encode the properties of the source that emit them. But how, and how much? What information will gravitational waves provide to constrain the central engines of astrophysical processes (e.g., short gamma ray bursts)?https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/dominik2/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/dominik2/Thu, 01 Aug 2013 00:00:00 +0000Previous calculations suggest star-forming environments very unlike our own (“low metallicity”) formed very massive binary black holes exceptionally frequently. Because short GRBs and gravitational waves are detectable over vast distances, a careful prediction for mergers over cosmic time must include this trend.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/pekowsky-test-precessing-imr/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/pekowsky-test-precessing-imr/Mon, 01 Jul 2013 00:00:00 +0000Several groups are attempting to construct synthetic gravitational wave signals that include the effect of precessinghttps://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/cgwas/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/cgwas/Mon, 01 Jul 2013 00:00:00 +0000At the Caltech Gravitational Wave Astrophysics summer school, my lectures provided students with a brief introduction to compact binary source populations – that is, to what the first gravitational wave detections ought to be, and why.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/gerosa1/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/gerosa1/Wed, 01 May 2013 00:00:00 +0000Binary black holes spiral in very slowly through the emission of gravitational radiation; most mergers should occur millions to billions of years after the binary’s birth. During this slow inspiral, coupling between angular momenta has been thought to scramble their relative orientations. That’s unfortunate: the spin and orbit orientations at birth reflect the processes that formed the binary, notably supernova, which misalign the spin and orbital plane.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/spin-taylor-f2/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/spin-taylor-f2/Mon, 01 Apr 2013 00:00:00 +0000In coming years, gravitational wave detectors should find black hole-neutron starbinaries, potentially coincident with astronomical phenomena like short GRBs. These binaries are expected to precess.Precessing black hole binaries produce a complicated signal, different in each direction, that reflects how the orbital plane precesses and the relative orientation of the line of sight and that precessing plane.Gravitational wave science requires a tractable model for precessing binaries, to disentangle precession physics from otherphenomena like modified strong field gravity, tidal deformability, or Hubble flow; and to measure compact objectmasses, spins, and alignments.Moreover, current searches for gravitational waves from compact binaries use templates where the binary does notprecess and are ill-suited for detection of generic precessing sources.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/precession-during-merger/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2013/precession-during-merger/Fri, 01 Feb 2013 00:00:00 +0000The merger of two precessing black holes produces a complicated gravitational wave signal which in principle fully encodes its highly nonlinear dynamics. Intuition gained from analytic studies prior to merger provide a simple picture: the two black holes spiral inward, with their spin and orbital angular momenta precessing around one another. Analytic studies after merger show the isolated black hole loses its hair", radiating away energy and angular momentum in quasinormal modes,” determined by eigenfunctions of the final black hole. How are these two epochs bridged for generic sources? How can observations probe those dynamics?https://oshaughnessy-junior.github.io/outward-facing-web/blog/2012/princeton-meeting/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2012/princeton-meeting/Tue, 01 May 2012 00:00:00 +0000I am often asked to explain how often compact binaries merge in the local universe; how often gravitational wave detectors will find the ripples in the fabric of the universe produced by these mergers; and what science these measurements enable.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2012/bradley/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2012/bradley/Thu, 01 Mar 2012 00:00:00 +0000The Bradley Fellowship program supported my research between 2011 and 2012.This report summarizes my resarch during that period for a non-expert audience.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2011/preferred-frame/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2011/preferred-frame/Thu, 01 Dec 2011 00:00:00 +0000In 2011, I identifed a robust ``corotating frame”, a way of choosing time-dependent angular coordinates at largedistances using only the radiated signal. Tested against simulated binary mergers provided by GeorgiaTech (J. Healy), this frame simplifies the outgoing gravitational wave signal. Mode-by-mode,the corotating-frame waveform is roughly similar to to nonprecessing waveforms, with vastly reduced modulation.https://oshaughnessy-junior.github.io/outward-facing-web/blog/2011/big-dig/https://oshaughnessy-junior.github.io/outward-facing-web/blog/2011/big-dig/Tue, 01 Mar 2011 00:00:00 +0000The LIGO and Virgo Collaborations quizzed ourselves: a group hid a realistic signal in our data. We wanted to confirm we could find a gravitational wave and identify its properties.