Compact binaries as strong gravitational wave sources and progenitors of type Ia supernovae

Projektinformationen

CompactBINARIES

ID Finanzhilfevereinbarung: 101078773

DOI

10.3030/101078773

EK-Unterschriftsdatum 3 April 2023

Startdatum 1 September 2023

Enddatum 31 August 2028

Finanziert unter

• European Research Council (ERC)

Gesamtkosten

€ 1 685 375,00

EU-Beitrag

€ 1 685 375,00

Koordiniert durch

UNIVERSITY OF HAMBURG
Germany

Periodic Reporting for period 1 - CompactBINARIES (Compact binaries as strong gravitational wave sources and progenitors of type Ia supernovae)

Berichtszeitraum: 2023-09-01 bis 2026-02-28

Zusammenfassung vom Kontext und den Gesamtzielen des Projekts

Many of the most spectacular events in the Universe — such as exploding stars and the merging of ultra-dense objects — originate in compact binary systems: pairs of stars orbiting each other at very small distances. These systems can contain white dwarfs, neutron stars, or other dense stellar remnants. They are key to understanding how Type Ia supernovae occur (which are essential tools for measuring the expansion of the Universe) and how gravitational waves are produced, which will be detected from space by the LISA mission.

Despite their importance, many compact binaries remain undiscovered. In particular, systems hidden in the crowded and dusty region of our Galaxy known as the Galactic Plane have been largely overlooked. In addition, the evolutionary pathways that lead to supernova explosions are not yet fully understood.

The overall objective of this project is to discover, characterise, and understand compact binary systems across the Milky Way. This includes identifying the shortest-period binaries, modelling their evolution from birth to explosion, and predicting which systems will be detectable as gravitational-wave sources. By combining observations from optical, ultraviolet, and X-ray surveys with detailed theoretical modelling, the project aims to build a coherent picture of how compact binaries form, evolve, and end their lives.

The expected impact is significant: improving our understanding of supernova progenitors, preparing for future gravitational-wave discoveries, and uncovering previously hidden populations of compact stellar systems. This work strengthens Europe’s leading role in time-domain astronomy and gravitational-wave science.

Arbeit, die ab Beginn des Projekts bis zum Ende des durch den Bericht erfassten Berichtszeitraums geleistet wurde, und die wichtigsten bis dahin erzielten Ergebnisse

The project developed a systematic strategy to identify compact binary candidates using large astronomical surveys. By combining colour information from multiple sky surveys and carefully correcting for dust extinction, especially in the Galactic Plane, we identified thousands of new candidate systems that had been missed in previous searches. In parallel, we selected additional candidates using X-ray observations to target the most compact and actively accreting systems. We collected and analysed time-series data from several facilities to search for periodic brightness variations, which are a key signature of close binary systems. Advanced statistical methods were used to detect short orbital periods.

Extensive follow-up observations were conducted using European and international telescopes. These included spectroscopic observations to measure stellar motions and high-speed photometry to precisely map brightness changes. This allowed us to confirm several new compact binaries, including rare systems containing helium stars orbiting compact objects. For the most interesting systems, we combined spectroscopic measurements with detailed light-curve modelling to determine precise stellar masses and sizes. This enables us to reconstruct their past evolution and predict their future, including whether they will emit detectable gravitational waves.

On the theoretical side, we developed state-of-the-art computer models to simulate the full life cycle of compact binaries. A major achievement was the first complete evolutionary model of a Type Ia supernova progenitor, following the system from normal stars through binary interactions to explosion. We also created models to predict which newly discovered systems will be detectable by the future LISA gravitational-wave mission.

Overall, the project has discovered new compact binaries, developed new analysis methods, and significantly improved our theoretical understanding of how these extreme systems evolve.

Fortschritte, die über den aktuellen Stand der Technik hinausgehen und voraussichtliche potenzielle Auswirkungen (einschließlich der bis dato erzielten sozioökonomischen Auswirkungen und weiter gefassten gesellschaftlichen Auswirkungen des Projekts)

The project goes beyond previous work in several important ways.

First, it systematically explored the Galactic Plane, a region traditionally avoided because of observational difficulties. By overcoming challenges related to dust and source crowding, we uncovered large numbers of previously unknown compact binaries. This significantly expands the known population and reduces biases in our understanding of binary evolution.

Second, the project achieved the first fully self-consistent evolutionary model of a confirmed Type Ia supernova progenitor. This represents a major step forward in understanding how such explosions are formed and helps refine models used across astrophysics and cosmology.

Third, we applied advanced machine learning techniques to large spectroscopic datasets to identify rare compact systems. While such methods are common in photometric surveys, their successful use for spectroscopic classification opens new possibilities for analysing future large-scale astronomical data.

The results have strong potential impact. The newly discovered systems provide prime targets for future space missions such as LISA. The modelling framework can be extended to larger samples and incorporated into population studies. The data analysis tools developed in this project are directly applicable to upcoming surveys and can be further refined.

To ensure continued success, further observational follow-up, expanded theoretical modelling, and sustained access to large survey data will be important. The groundwork laid by this project positions Europe at the forefront of compact binary and gravitational-wave research.

In summary, the project has uncovered hidden stellar systems, advanced our understanding of stellar explosions, and developed innovative tools for the analysis of large astronomical datasets, contributing lasting value to astrophysics and space science.