How much information can we gain by pushing numerical relativity to its limit by simulating black hole scattering encounters? My latest paper (below) explores these extreme regions of the black-hole scattering parameter space using simulations generated using the Spectral Einstein Code (SpEC).
Three papers from the Multiscale Self-Force (MSF) collaboration on the arXiv yesterday that made use of the BHPToolkit. The first was "Spin-aligned inspiral waveforms from self-force and post-Newtonian theory" by Loïc Honet et al. arxiv.org/abs/2510.16112
In all the papers I’ve been first author on, I’ve gone with no hyphens. But I have also co-authored papers with “extreme mass-ratio inspiral” and “extreme-mass-ratio inspiral”, so it depends how much you personally like hyphens
Groundbreaking new image! The EHT reveals the dynamic environment around black hole M87*.
The 2021 image shows a distinct shift in polarization patterns, tracing changes in magnetic fields near the event horizon.
eventhorizontelescope.org/new-eht-imag...
Recent paper the cites the BHPToolkit: "Systematic errors in fast relativistic waveforms for Extreme Mass Ratio Inspirals" by Hassan Khalvati, Philip Lynch, Ollie Burke, Lorenzo Speri, Maarten van de Meent, Zachary Nasipak, arxiv.org/abs/2509.08875
A Decade of Gravitational Waves
This is just a quick post to mark the fact that it is now ten years to the day since the first detection of gravitational waves by Advanced LIGO. The acronym LIGO stands for Laser Interferometer Gravitational-wave Observatory. It wasn't until February 11th 2016 that…
In short: so long as we're careful, fast EMRI waveforms can be accurate enough for LISA’s science goals including pushing general relativity to its limits
The good news is if interpolation errors are controlled so that they’re no bigger than the small mass ratio (say 1 part in 100,000), they won’t hurt parameter estimation.
We found that:
1️⃣ For rapidly spinning black holes, you need to include at least ~30 modes to avoid bias.
2️⃣ A smart interpolation method using Chebyshev polynomials can be more efficient, reaching the needed accuracy with far fewer data points, while still being fast enough
Our new study looks at hidden systematic errors that can crop up when calculating the flux. We focused on two culprits:
1️⃣ Cutting off the calculation of higher modes
2️⃣ Errors introduced when using interpolating the flux to create fast waveform models
We focus on leading order (adiabatic) waveform models where one only needs to balance the flux of energy leaving the system in the form of gravitational waves with the orbital energy lost by smaller black hole
But there’s a challenge: to decode these signals, we need waveform models that are both super accurate (tiny phase errors matter!) and super fast (millions of templates are needed to search data).
EMRIs can orbit hundreds of thousands of times before merging. Their gravitational waves carry a detailed map of spacetime near supermassive black holes, providing a unique test of Einstein’s theory in the strongest gravity we can observe.
Future space missions like LISA will listen to gravitational waves from some of the most extreme events in the universe: Extreme Mass-Ratio Inspirals (EMRIs). These are systems where a stellar mass black hole spirals into a supermassive one while emitting low frequency graviational waves
A posting on the arXiv preprint server. Title: Systematic errors in fast relativistic waveforms for Extreme Mass Ratio Inspirals Authors: Hassan Khalvati, Philip Lynch, Ollie Burke, Lorenzo Speri, Maarten van de Meent, Zachary Nasipak Abstract: Accurate modeling of Extreme Mass-Ratio Inspirals (EMRIs) is essential for extracting reliable information from future space-based gravitational wave observatories. Fast waveform generation frameworks adopt an offline/online architecture, where expensive relativistic computations (e.g. self-force and black hole perturbation theory) are performed offline, and waveforms are generated rapidly online via interpolation across a multidimensional parameter space. In this work, we investigate potential sources of error that result in systematic bias in these relativistic waveform models, focusing on radiation-reaction fluxes. Two key sources of systematics are identified: (i) the intrinsic inaccuracy of the flux data, for which we focus on the truncation of the multipolar mode sum, and (ii) interpolation errors from transitioning to the online stage. We quantify the impact of mode-sum truncation and analyze interpolation errors by using various grid structures and interpolation schemes. For circular orbits in Kerr spacetime with spins larger than a≥0.9, we find that ℓmax≥30 is required for the necessary accuracy. We also develop an efficient Chebyshev interpolation scheme, achieving the desired accuracy level with significantly fewer grid points compared to spline-based methods. For circular orbits in Kerr spacetimes, we demonstrate via Bayesian studies that interpolating the flux to a maximum global relative error that is equal to the small mass ratio is sufficient for parameter estimation purposes. For 4-year long quasi-circular EMRI signals with SNRs=O(100) and mass-ratios 10^−4−10^−6, a global relative error of 10−6 yields mismatches <10^−3 and negligible parameter estimation biases.
New paper on the arXiv today about systematic errors when modelling the gravitation waveform from extreme mass ratio inspirals and their impact on LISA data science
Huge thanks to my collaborators, especially Hassan Khalvati, for getting this project over the line! 🧪⚛️🔭🧮
arxiv.org/abs/2509.08875
I’m incredibly proud to be part of this and to have my simulations turn into the first publicly available scattering and dynamical capture waveforms!
Below is a plot I made for the Einstein Toolkit Blue Book (arXiv:2503.12263) showing the waveforms SXS:BBH:3999 (scatter) and SXS:BBH:4000 (capture).
When simulating orbiting black holes, we move our grid with the holes! One of the key lessons of general relativity is coordinates are meaningless. We exploit this to choose comoving coordinates where the metric changes as little as possible.
www.youtube.com/watch?v=j4WG...
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Welcome to the #LECSTalks! series, where we showcase the people, activity, and science taking place around the LISA Early Career Scientists community. 🎤
Today we feature Ben Leather, postdoctoral researcher at the MPI for Grav Physics, talking about Waveform Modelling with Gravitational Self-Force.
🍾The LIGO - Virgo - KAGRA Collaboration has announced the detection of the 200th candidate gravitational wave signal in this fourth observation period O4!
Saturn's outer moon system viewed from the north pole of Saturn. Moons orbiting in clockwise (retrograde) orbits have red-colored orbits while moons orbiting counterclockwise (prograde; in the direction of Saturn's spin) are colored blue. With so many irregular moons occupying the same region and intersecting each other, the irregular moon system looks like a donut-shaped vortex surrounding Saturn. Each of the 128 new moons is highlighted in the diagram with a white point representing their location, and a brighter-colored orbit. Previously-known moons of Saturn are included in the diagram, but are colored darker. The regular moons of Saturn are colored turquoise and the outermost regular moons (Titan, Hyperion, and Iapetus) labeled with their name. At the lower left corner are scale indicators to help visualize the scale of Saturn's irregular moon system. A small gray circle at the left left corner is shown to represent the diameter of the Earth-Moon orbital distance. A linear scale bar is labeled "10 million km" (6.2 million mi) to give a standard distance.
View of Saturn's irregular moon system, tilted at an angle to show the toroidal belt-like shape of the system. Each moon is labeled with their names in turquioise. Red orbits = retrograde direction, and blue orbits = prograde direction. Turquoise curves closer to the center are orbits of Saturn's regular moons.
Side view of Saturn's irregular moon system, tilted at an angle to show the toroidal belt-like shape of the system. Red orbits = retrograde direction, and blue orbits = prograde direction. Turquoise curves closer to the center are orbits of Saturn's regular moons. The irregular moons of Neptune (dark green) are also visible in the background to the right of Saturn. The horizontal red line protruding right of Saturn is the orbit path of Saturn.
I spent almost 2 hours painstakingly copying the orbits of all 128 Saturnian moons from the announcement MPEC and reformatting them for visualization...
Behold, here are the orbits of ALL 128 MOONS OF SATURN. This isn't just a moon system—it's a literal asteroid belt around Saturn! 🧪🔭☄️
I just don't know what else to say at this point except call your reps (5calls.org) and keep fighting. Do not ignore the chaos. Keeping your head down will not protect you 🔭 #PlanetaryScience #Exoplanets
nasawatch.com/ask-the-admi...
Neutron star poster, shown with geometric pulsars going out of it and a magnetic field, geometric, art deco, futuristic #sciart
The hardest part of creating a design? Posting it on social media, but anyway, here it is! Neutron stars are insanely dense,(teaspoon of neutron star would weight 4 billion tons on Earth). Some are pulsars, like beacons in space or/and magnetars!
🔭Store: kategraphiccreations.etsy.com
#sciart
Poster of two binary stars orbiting each other, it has elements that come from the merge of the two stars coming out, like Au,Ag,Th,Rh,Gd,Pu,Pd,Eu art deco style, minimalistic #Sciart
"The team predicts that the two neutron stars will spiral slowly toward each other in a cosmic dance, ultimately colliding in a kilonova explosion." Inspired by @skuthunur.bsky.social article & thanks to @astro-jje.bsky.social for patiently answering all my silly binary star questions! #Sciart
The 🎉200th paper 🎉 that cites the BHPToolkit: "Lensing and wave optics in the strong field of a black hole" by Juno C. L. Chan, Conor Dyson, Matilde Garcia, Jaime Redondo-Yuste, Luka Vujeva, arxiv.org/abs/2502.14073
Ever wonder how gravitational wave detectors like LISA would hear the signal of binary black holes orbiting around a supermassive black hole? 🔭
Well check out my first 1st author paper investigating that very topic, live on the arXiv today!
🔥📄 arxiv.org/abs/2502.10591
Explainer in 🧵👇 1/10
#February11 is the International Day of Women and Girls in Science #IDWGS. Meet some of our international #WomenInSTEM through #HumansOfLIGO
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A new major update to the Teukolsky package has been released (version 1.1.0). A major new feature the the ability to PN expand various Teukolsky radial functions (contribution from Jakob Neef)
Ok doomscrollers, here is a HAPPY news story from Gizmodo about LISA, the gravitational wave observatory that will be launched by ESA, with NASA support, in the mid-2030s (I’m quoted, as are @jakepost.tech & Emanuele Berti).
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A figure from the paper (Figure 4). It shows the locations of known hypervelocity stars as black circles, with the predicted overdensity that the LMC would cause shown in red. Full caption: Predicted on-sky overdensity of hypervelocity stars originating from a 6 × 105M⊙ supermassive black hole in the LMC. The black open circles denote the Galactic coordinates of hypervelocity stars detected in the HVS Survey, while the grey-shaded regions mark areas excluded from the survey. The current position of the LMC is illustrated with a representative image, and its orbital trajectory is drawn with a red arrow. The forward model incorporating an SMBH in the LMC along with the selection effects of the HVS Survey predicts a prominent overdensity of HVS in the region enclosed by the red contours. The overdensity arises because stars are boosted in the direction of the LMC’s orbit. This model accurately reproduces the observed overdensity location, supporting the hypothesis of an SMBH in the LMC as a source of these stars.
A very fascinating paper went up on the arXiv today!
Jesse Han & El-Badry et al. reanalysed the 21 known 'hypervelocity' stars in the #milkyway.
They find strong evidence that the LMC (Large Milky/Magellanic Cloud) has a supermassive black hole at its core! 🤯 arxiv.org/abs/2502.00102
When things go well, preparing for a lecture is one of my happy places. I get to read, and understand better, stuff that I'm interested in. I get to make diagrams and animations, always fun. Here is an animation of the motion of a star in a disk galaxy for your viewing pleasure: 1/ 🧪🔭
