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Working Area 4:
Electromagnetic signals from
compact stars

The properties of NSs are deduced mainly through the observations of their EM radiation. Isolated NSs, as well as violent processes involving NSs, such as X-ray bursts and BNS mergers, are characterized by extraordinarily intense EM signatures via X-ray and gamma-ray emissions, kilonova signals and GWs (WA2), all of which are routinely detected by numerous Earth- and/or space-based instruments. The observed light-curves of X-ray bursts and kilonovae reflect the complex microphysical processes at play in these cosmic events. Based on the nuclear-physics inputs provided by WA1-WA3, in this WA we will model the corresponding EM light-curves and compare them to observations. Furthermore, because of the presence of strong EM fields, general-relativistic and QED effects can play an important role and will be addressed in this WA.

Reference of the figure: A. Arcones, S. Rosswog, 10.1103/PhysRevLett.116.121101 .
Reference of the figure: 10.1126/science.aaq0049, © Copyright: APS
Reference of the figure: NASA

The properties of NSs are deduced mainly through the observations of their EM radiation. Isolated NSs, as well as violent processes involving NSs, such as X-ray bursts and BNS mergers, are characterized by extraordinarily intense EM signatures via X-ray and gamma-ray emissions, kilonova signals and GWs (WA2), all of which are routinely detected by numerous Earth- and/or space-based instruments. The observed light-curves of X-ray bursts and kilonovae reflect the complex microphysical processes at play in these cosmic events. Based on the nuclear-physics inputs provided by WA1-WA3, in this WA we will model the corresponding EM light-curves and compare them to observations. Furthermore, because of the presence of strong EM fields, general-relativistic and QED effects can play an important role and will be addressed in this WA.

Kilonova: EM signatures of r-process nucleosynthesis

ELEMENTS will develop kilonova models able to predict not only the bolometric light curve but also the spectral evolution based on the most accurate simulations in full general relativity which account for realistic EOSs, the presence of strong magnetic fields, and sophisticated models for the radiative impact of neutrino emission and absorption.

With the goal of providing urgently needed accurate data for benchmarking atomic-structure codes used for calculations of EM opacities, we will employ the low-energy storage ring CRYRING@ESR. Within ELEMENTS, we will develop instrumentation at CRYRING@ESR to address experimentally the structure of ionized atoms in the lanthanide region. CRYRING@ESR will be developed into a world-unique laboratory-astrophysics facility, well beyond its defined role in GSI/FAIR research.

Light curve observations for AT2017gfo compared with a light curve model that assumes production of r-process nuclei in solar proportions up to a minimum value Amin [Wu]. DOI: 10.1103/PhysRevLett.122.062701
Evolution of the spectra for AT2017gfo showing the identification of absorption lines associated to Sr [Watson]. DOI: 10.1038/s41586-019-1676-

EM radiation from isolated and accreting NS

The properties of atmospheres of isolated and accreting NS and the transport of EM radiation through such environments are not fully understood. ELEMENTS aims at understanding the properties of EM radiation in the presence of strong EM fields. In a low-mass X-ray binary system, a NS mainly accretes hydrogen and helium from its less-evolved companion star until a thermonuclear explosion occurs and is followed by a rapid proton-capture nucleosynthesis process (rp-process), revealed in space by an intense EM signature, i.e., an X-ray burst. ELEMENTS will constrain the light-curves of the X- ray bursts through precision measurements of key nuclear reactions.

Storage and trapping facilities at GSI/FAIR available for research within ELEMENTS

The following milestones have been formulated in work area 4:

  • Provide an advanced theoretical description of the r-process in BNS mergers and predictions of the spectral energy distribution
  • Establish the experiment for high-precision investigations of medium-charged heavy ions at the CRYRING@ESR stand-alone operation
  • Carry out high-precision experiments with highly-charged ions at the ESR, CRYRING@ESR and HITRAP
  • Develop reaction technique using CRYRING@ESR storage ring to study key proton- and alpha-induced reactions for the rp-process

PIs in this work area include: A. Arcones, A. Bauswein, Y.Litvinov, G. Martínez-Pinedo, R. Reifarth, L. Rezzolla, S. Schippers,  and T. Stöhlker