Neutron star mergers and how to study them

AbstractNeutron star mergers are the canonical multimessenger events: they have been observed through photons for half a century, gravitational waves since 2017, and are likely to be sources of neutrinos and cosmic rays. Studies of these events enable unique insights into astrophysics, particles in the ultrarelativistic regime, the heavy element enrichment history through cosmic time, cosmology, dense matter, and fundamental physics. Uncovering this science requires vast observational resources, unparalleled coordination, and advancements in theory and simulation, which are constrained by our current understanding of nuclear, atomic, and astroparticle physics. This review begins with a summary of our current knowledge of these events, the expected observational signatures, and estimated detection rates for the next decade. I then present the key observations necessary to advance our understanding of these sources, followed by the broad science this enables. I close with a discussion on the necessary future capabilities to fully utilize these enigmatic sources to understand our universe.

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Fundamental Physics from Space and in Space

International Journal of Modern Physics A ◽

10.1142/s0217751x9700147x ◽

1997 ◽

Vol 12 (15) ◽

pp. 2623-2638 ◽

Cited By ~ 1

Author(s):

M. Jacob

Keyword(s):

Cosmic Rays ◽

Gravitational Waves ◽

Particle Physics ◽

Astroparticle Physics ◽

Fundamental Physics ◽

Key Questions

Whereas most of the key questions in particle physics are still addressed with accelerators, one sees at present an increasing activity in cosmic rays, based on the use of large and sophisticated detectors on the ground and underground (or under water). A new discipline, "astroparticle physics" is born and rapidly expanding. Whereas much of this research is carried out on Earth, it is likely that part of it will eventually transfer to space. The detection of gravitational waves is now attempted with a new promising vigor, using interferometers. This physics at present on the ground will have to extend to space. The talk reviews facts and trends in this research in fun damental physics from space now, but increasingly in space later on.

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Transport Coefficients of Hyperonic Neutron Star Cores

Universe ◽

10.3390/universe7060203 ◽

2021 ◽

Vol 7 (6) ◽

pp. 203

Author(s):

Peter Shternin ◽

Isaac Vidaña

Keyword(s):

Thermal Conductivity ◽

Neutron Star ◽

Shear Viscosity ◽

Transport Coefficients ◽

Dense Matter ◽

Baryon Number ◽

Nucleon Nucleon ◽

Total Thermal Conductivity ◽

Nucleon Force ◽

Density Region

We consider transport properties of the hypernuclear matter in neutron star cores. In particular, we calculate the thermal conductivity, the shear viscosity, and the momentum transfer rates for npΣ−Λeμ composition of dense matter in β–equilibrium for baryon number densities in the range 0.1–1 fm−3. The calculations are based on baryon interactions treated within the framework of the non-relativistic Brueckner-Hartree-Fock theory. Bare nucleon-nucleon (NN) interactions are described by the Argonne v18 phenomenological potential supplemented with the Urbana IX three-nucleon force. Nucleon-hyperon (NY) and hyperon-hyperon (YY) interactions are based on the NSC97e and NSC97a models of the Nijmegen group. We find that the baryon contribution to transport coefficients is dominated by the neutron one as in the case of neutron star cores containing only nucleons. In particular, we find that neutrons dominate the total thermal conductivity over the whole range of densities explored and that, due to the onset of Σ− which leads to the deleptonization of the neutron star core, they dominate also the shear viscosity in the high density region, in contrast with the pure nucleonic case where the lepton contribution is always the dominant one.

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Geodesy, Geophysics and Fundamental Physics Investigations of the BepiColombo Mission

Space Science Reviews ◽

10.1007/s11214-021-00808-9 ◽

2021 ◽

Vol 217 (2) ◽

Author(s):

Antonio Genova ◽

Hauke Hussmann ◽

Tim Van Hoolst ◽

Daniel Heyner ◽

Luciano Iess ◽

...

Keyword(s):

Magnetic Field ◽

Surface Composition ◽

Current Knowledge ◽

Laser Altimeter ◽

Fundamental Physics ◽

Radio Science ◽

Nasa Mission ◽

Gravity And Magnetic ◽

Working Groups ◽

Science Investigations

AbstractIn preparation for the ESA/JAXA BepiColombo mission to Mercury, thematic working groups had been established for coordinating the activities within the BepiColombo Science Working Team in specific fields. Here we describe the scientific goals of the Geodesy and Geophysics Working Group (GGWG) that aims at addressing fundamental questions regarding Mercury’s internal structure and evolution. This multidisciplinary investigation will also test the gravity laws by using the planet Mercury as a proof mass. The instruments on the Mercury Planetary Orbiter (MPO), which are devoted to accomplishing the GGWG science objectives, include the BepiColombo Laser Altimeter (BELA), the Mercury orbiter radio science experiment (MORE), and the MPO magnetometer (MPO-MAG). The onboard Italian spring accelerometer (ISA) will greatly aid the orbit reconstruction needed by the gravity investigation and laser altimetry. We report the current knowledge on the geophysics, geodesy, and evolution of Mercury after the successful NASA mission MESSENGER and set the prospects for the BepiColombo science investigations based on the latest findings on Mercury’s interior. The MPO spacecraft of the BepiColombo mission will provide extremely accurate measurements of Mercury’s topography, gravity, and magnetic field, extending and improving MESSENGER data coverage, in particular in the southern hemisphere. Furthermore, the dual-spacecraft configuration of the BepiColombo mission with the Mio spacecraft at higher altitudes than the MPO spacecraft will be fundamental for decoupling the internal and external contributions of Mercury’s magnetic field. Thanks to the synergy between the geophysical instrument suite and to the complementary instruments dedicated to the investigations on Mercury’s surface, composition, and environment, the BepiColombo mission is poised to advance our understanding of the interior and evolution of the innermost planet of the solar system.

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UNDERGROUND LABORATORIES AND THEIR PHYSICS REACH

International Journal of Modern Physics A ◽

10.1142/s0217751x12300086 ◽

2012 ◽

Vol 27 (08) ◽

pp. 1230008

Author(s):

E. COCCIA

Keyword(s):

Dark Matter ◽

Cosmic Rays ◽

Nuclear Astrophysics ◽

Astroparticle Physics ◽

The World ◽

Radioactive Background ◽

Earth's Crust ◽

Silence Condition ◽

Rare Phenomena ◽

Fundamental Forces

Underground laboratories, shielded by the Earth's crust from the particles that rain down on the surface in the form of cosmic rays, provide the low radioactive background environment necessary to host key experiments in the field of particle and astroparticle physics, nuclear astrophysics and other disciplines that can profit of their characteristics and of their infrastructures. The cosmic silence condition existing in these laboratories allows the search for extremely rare phenomena and the exploration of the highest energy scales that cannot be reached with accelerators. Major fundamental challenges are within the scope of these laboratories, notably, understanding the properties of neutrinos and dark matter, and exploring the unification of the fundamental forces of nature. I will review the physics reach and briefly describe the main underground facilities that are presently in operation around the world.

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UV and X-ray observations of the neutron star LMXB EXO 0748–676 in its quiescent state

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3734 ◽

2020 ◽

Vol 501 (1) ◽

pp. 1453-1462

Author(s):

A S Parikh ◽

N Degenaar ◽

J V Hernández Santisteban ◽

R Wijnands ◽

I Psaradaki ◽

...

Keyword(s):

Neutron Star ◽

Thermal Emission ◽

Hubble Space Telescope ◽

Dense Matter ◽

Continuum Emission ◽

Quiescent State ◽

X Ray ◽

Low Level ◽

Low Mass ◽

Different Origins

ABSTRACT The accretion behaviour in low-mass X-ray binaries (LMXBs) at low luminosities, especially at <1034 erg s−1, is not well known. This is an important regime to study to obtain a complete understanding of the accretion process in LMXBs, and to determine if systems that host neutron stars with accretion-heated crusts can be used probe the physics of dense matter (which requires their quiescent thermal emission to be uncontaminated by residual accretion). Here, we examine ultraviolet (UV) and X-ray data obtained when EXO 0748–676, a crust-cooling source, was in quiescence. Our Hubble Space Telescope spectroscopy observations do not detect the far-UV continuum emission, but do reveal one strong emission line, C iv. The line is relatively broad (≳3500 km s−1), which could indicate that it results from an outflow such as a pulsar wind. By studying several epochs of X-ray and near-UV data obtained with XMM–Newton, we find no clear indication that the emission in the two wavebands is connected. Moreover, the luminosity ratio of LX/LUV ≳ 100 is much higher than that observed from neutron star LMXBs that exhibit low-level accretion in quiescence. Taken together, this suggests that the UV and X-ray emission of EXO 0748–676 may have different origins, and that thermal emission from crust-cooling of the neutron star, rather than ongoing low-level accretion, may be dominating the observed quiescent X-ray flux evolution of this LMXB.

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Bounds on the speed of sound in dense matter, and neutron star structure

Physical Review C ◽

10.1103/physrevc.95.045801 ◽

2017 ◽

Vol 95 (4) ◽

Cited By ~ 23

Author(s):

Ch. C. Moustakidis ◽

T. Gaitanos ◽

Ch. Margaritis ◽

G. A. Lalazissis

Keyword(s):

Neutron Star ◽

Speed Of Sound ◽

Dense Matter ◽

Star Structure

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THE ALICE EXPERIMENT AT CERN LHC: STATUS AND FIRST RESULTS

International Journal of Modern Physics A ◽

10.1142/s0217751x11051925 ◽

2011 ◽

Vol 26 (03n04) ◽

pp. 517-522

Author(s):

◽

ERMANNO VERCELLIN

Keyword(s):

Data Analysis ◽

Cosmic Rays ◽

Dense Matter ◽

Heavy Ion ◽

Short Description ◽

Alice Experiment ◽

Ion Collisions ◽

Physics Program ◽

Accelerate Proton ◽

First Results

The ALICE experiment is aimed at studying the properties of the hot and dense matter produced in heavy-ion collisions at LHC energies. In the first years of LHC operation the ALICE physics program will be focused on Pb - Pb and p - p collisions. The latter, on top of their intrinsic interest, will provide the necessary baseline for heavy-ion data. After its installation and a long commissioning with cosmic rays, in late fall 2009 ALICE participated (very successfully) in the first LHC run, by collecting data in p - p collisions at c.m. energy 900 GeV. After a short stop during winter, LHC operations have been resumed; the machine is now able to accelerate proton beams up to 3.5 TeV and ALICE has undertaken the data taking campaign at 7 TeV c.m. energy. After an overview of the ALICE physics goals and a short description of the detector layout, the ALICE performance in p - p collisions will be presented. The main physics results achieved so far will be highlighted as well as the main aspects of the ongoing data analysis.

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Multimessenger approaches to exploring dense matter in neutron stars

10.21248/gups.61856 ◽

2021 ◽

Author(s):

◽

Lukas Weih

Keyword(s):

Phase Transition ◽

Neutron Star ◽

Nuclear Physics ◽

Computational Cost ◽

Dense Matter ◽

High Energy ◽

Radiative Transport ◽

Binary Neutron Star ◽

Starting Point ◽

Numerical Astrophysics

High-energy astrophysics plays an increasingly important role in the understanding of our universe. On one hand, this is due to ground-breaking observations, like the gravitational-wave detections of the LIGO and Virgo network or the black-hole shadow observations of the EHT collaboration. On the other hand, the field of numerical relativity has reached a level of sophistication that allows for realistic simulations that include all four fundamental forces of nature. A prime example of how observations and theory complement each other can be seen in the studies following GW170817, the first detection of gravitational waves from a binary neutron-star merger. The same detection is also the chronological starting point of this Thesis. The plethora of information and constraints on nuclear physics derived from GW170817 in conjunction with theoretical computations will be presented in the first part of this Thesis. The second part goes beyond this detection and prepares for future observations when also the high-frequency postmerger signal will become detectable. Specifically, signatures of a quark-hadron phase transition are discussed and the specific case of a delayed phase transition is analyzed in detail. Finally, the third part of this Thesis focuses on the inclusion of radiative transport in numerical astrophysics. In the context of binary neutron-star mergers, radiation in the form of neutrinos is crucial for realistic long-term simulations. Two methods are introduced for treating radiation: the approximate state-of-the-art two-moment method (M1) and the recently developed radiative Lattice-Boltzmann method. The latter promises to be more accurate than M1 at a comparable computational cost. Given that most methods for radiative transport or either inaccurate or unfeasible, the derivation of this new method represents a novel and possibly paradigm-changing contribution to an accurate inclusion of radiation in numerical astrophysics.

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