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The physics and forensics of neutron star explosions

Descrizione del progetto

Una tecnica innovativa per sondare le profondità delle stelle di neutroni

Le stelle di neutroni rappresentano il banco di prova perfetto per le forze forti in condizioni estreme, con densità del nucleo fino a 10 volte superiori a quelle dei nuclei atomici. Esaminando l’equazione di stato, i ricercatori sono in grado di studiare la fisica della materia densa attraverso osservabili macroscopici come la massa e il raggio. Il progetto CSINEUTRONSTAR, finanziato dal Consiglio europeo della ricerca, utilizzerà una tecnica innovativa per misurare simultaneamente la massa e il raggio, basata sulle oscillazioni dei burst, che si verificano quando il materiale proveniente da una stella compagna provoca un’esplosione termonucleare sulla superficie della stella di neutroni. I ricercatori cercheranno di scoprire il meccanismo finora sconosciuto che genera le oscillazioni a raffica.

Obiettivo

Neutron stars offer a unique environment in which to develop and test theories of the strong force. Densities in neutron star cores can reach up to ten times the density of a normal atomic nucleus, and the stabilizing effect of gravitational confinement permits long-timescale weak interactions. This generates matter that is neutron-rich, and opens up the possibility of stable states of strange matter, something that can only exist in neutron stars. Strong force physics is encoded in the Equation of State (EOS), the pressure-density relation. This is linked to macroscopic observables such as mass M and radius R via the stellar structure equations. By measuring and inverting the M-R relation we can recover the EOS and diagnose the underlying dense matter physics.

This proposal focuses on a very promising technique for simultaneous measurement of M and R. It exploits hotspots (burst oscillations) that form on the neutron star surface when material accreted from a companion star undergoes a thermonuclear explosion (a Type I X-ray burst). As the star rotates, the hotspot gives rise to a pulsation. Relativistic effects then encode information about M and R into the pulse profile. However the mechanism that generates burst oscillations remains unknown, 18 years after their discovery. This is frustrating in terms of our understanding of thermonuclear bursts. It also leads to uncertainties in the precise form of the underlying surface emission pattern (a key factor in the pulse profile fitting process), which must be addressed to cement their reliability as diagnostics of M and R.

This proposal has two objectives. Firstly, to resolve the burst oscillation mechanism via an ambitious programme of theoretical and observational analysis. Secondly, to ensure that burst oscillations are a robust tool for measurement of M and R by determining the effect of the surface pattern uncertainty on pulse profile fitting, independent of efforts to constrain the mechanism.

Meccanismo di finanziamento

ERC-STG - Starting Grant

Istituzione ospitante

UNIVERSITEIT VAN AMSTERDAM
Contribution nette de l'UE
€ 1 499 999,00
Indirizzo
SPUI 21
1012WX Amsterdam
Paesi Bassi

Mostra sulla mappa

Regione
West-Nederland Noord-Holland Groot-Amsterdam
Tipo di attività
Higher or Secondary Education Establishments
Collegamenti
Costo totale
€ 1 499 999,00

Beneficiari (1)