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Spectral and Polarization Properties of Coherent Radio Emission from Relativistic Magnetized Pair Plasma Shocks
Yuanhong Qu, Joonas Nättilä, Lorenzo Sironi
Fast radio bursts (FRBs) are millisecond-duration radio transients whose emission mechanism remains an open question. The so-called synchrotron maser instability in relativistic ma…
Pair Discharges and Radio Emission from Millisecond-Pulsar and White-Dwarf Magnetospheres
Tuomo Salmi, Joonas Nättilä
Coherent radio emission is observed from compact astrophysical objects with relatively weak magnetic fields, including millisecond pulsars and white dwarfs, the latter being propos…
Pair Discharges and Radio Emission from Pulsar Magnetospheres
Joonas Nättilä, Tuomo Salmi
Radio pulsars can power their coherent radio emission through intermittent plasma discharges in magnetospheric gaps. The nonlinear coupling between particle acceleration, quantum e…
Studying the mirror acceleration via kinetic simulations of relativistic plasma turbulence
Saikat Das, Siyao Xu, Joonas Nättilä
Efficient relativistic turbulent acceleration of particles is indicated by recent astrophysical observations. The acceleration mechanism due to temporal variations of magnetic fiel…
Neutron Star Atmosphere-Ocean Dynamics
Joonas Nättilä, James Y-K. Cho, Jack W. Skinner +2
We analyze the structure and dynamics of the plasma atmospheres and Coulomb-liquid oceans on neutron stars. Salient dynamical parameters are identified and their values estimated f…
Strongly interacting matter exhibits deconfined behavior in massive neutron stars
Eemeli Annala, Tyler Gorda, Joonas Hirvonen +4
Neutron-star cores contain matter at the highest densities in our Universe. This highly compressed matter may undergo a phase transition where nuclear matter melts into deconfined…
Relativistic Collisionless Shocks in Inhomogeneous Magnetized Plasmas
Camilia Demidem, Joonas Nättilä, Alexandra Veledina
Relativistic collisionless shocks are associated with efficient particle acceleration when propagating into weakly magnetized homogeneous media; as the magnetization increases, par…
Fundamental physics with neutron stars
Joonas Nättilä, Jari J. E. Kajava
Neutron stars are rich laboratories of multiple branches of modern physics. These include gravitational physics, nuclear and particle physics, (quantum) electrodynamics, and plasma…
Heating of Magnetically Dominated Plasma by Alfvén-Wave Turbulence
J. Nättilä, A. M. Beloborodov
Magnetic energy around astrophysical compact objects can strongly dominate over plasma rest mass. Emission observed from these systems may be fed by dissipation of Alfvén wave turb…
Coherent Electromagnetic Emission from Relativistic Magnetized Shocks
Lorenzo Sironi, Illya Plotnikov, Joonas Nättilä +1
Relativistic magnetized shocks are a natural source of coherent emission, offering a plausible radiative mechanism for Fast Radio Bursts (FRBs). We present first-principles 3D simu…
Multimessenger constraints for ultra-dense matter
Eemeli Annala, Tyler Gorda, Evangelia Katerini +4
Recent rapid progress in neutron-star (NS) observations offers great potential to constrain the properties of strongly interacting matter under the most extreme conditions. In orde…
Radiative turbulent flares in magnetically-dominated plasmas
J. Nättilä, A. M. Beloborodov
We perform 2D and 3D kinetic simulations of reconnection-mediated turbulent flares in a magnetized electron-positron plasma, with weak and strong radiative cooling. Such flares can…
Pulsar wind-heated accretion disk and the origin of modes in transitional millisecond pulsar PSR J1023+0038
Alexandra Veledina, Joonas Nättilä, Andrei M. Beloborodov
Transitional millisecond pulsars provide a unique set of observational data for understanding accretion at low rates onto magnetized neutron stars. In particular, PSR~J1023+0038 ex…
Evidence for quark-matter cores in massive neutron stars
Eemeli Annala, Tyler Gorda, Aleksi Kurkela +2
The theory governing the strong nuclear force, Quantum Chromodynamics, predicts that at sufficiently high energy densities hadronic nuclear matter undergoes a deconfinement transit…
Neutron star mass and radius measurements from atmospheric model fits to X-ray burst cooling tail spectra
J. Nättilä, M. C. Miller, A. W. Steiner +3
Observations of thermonuclear X-ray bursts from accreting neutron stars (NSs) in low-mass X-ray binary systems can be used to constrain NS masses and radii. Most previous work of t…
Radiation from rapidly rotating oblate neutron stars
Joonas Nättilä, Pauli Pihajoki
A theoretical framework for emission originating from rapidly rotating oblate compact objects is described in detail. By using a Hamilton-Jacobi formalism, we show how the special…
Variable spreading layer in 4U 1608-52 during thermonuclear X-ray bursts in the soft state
J. J. E. Kajava, K. I. I. Koljonen, J. Nättilä +2
Thermonuclear (type-I) X-ray bursts, observed from neutron star (NS) low-mass X-ray binaries (LMXB), provide constraints on NS masses and radii and consequently the equation of sta…
Flux decay during thermonuclear X-ray bursts analysed with the dynamic power-law index method
J. Kuuttila, J. J. E. Kajava, J. Nättilä +5
The cooling of type-I X-ray bursts can be used to probe the nuclear burning conditions in neutron star envelopes. The flux decay of the bursts has been traditionally modelled with…
The direct cooling tail method for X-ray burst analysis to constrain neutron star masses and radii
Valery F. Suleimanov, Juri Poutanen, Joonas Nättilä +3
Determining neutron star (NS) radii and masses can help to understand the properties of matter at supra-nuclear densities. Thermal emission during thermonuclear X-ray bursts from N…
Detection of burning ashes from thermonuclear X-ray bursts
J. J. E. Kajava, J. Nättilä, J. Poutanen +3
When neutron stars (NS) accrete gas from low-mass binary companions, explosive nuclear burning reactions in the NS envelope fuse hydrogen and helium into heavier elements. The resu…
Equation of state constraints for the cold dense matter inside neutron stars using the cooling tail method
J. Nättilä, A. W. Steiner, J. J. E. Kajava +2
The cooling phase of thermonuclear (type-I) X-ray bursts can be used to constrain the neutron star (NS) compactness by comparing the observed cooling tracks of bursts to accurate t…
Models of neutron star atmospheres enriched with nuclear burning ashes
Joonas Nättilä, Valery Suleimanov, Jari J. E. Kajava +1
Low-mass X-ray binaries hosting neutron stars (NS) exhibit thermonuclear (type-I) X-ray bursts, which are powered by unstable nuclear burning of helium and/or hydrogen into heavier…
The influence of accretion geometry on the spectral evolution during thermonuclear (type-I) X-ray bursts
Jari J. E. Kajava, Joonas Nättilä, Outi-Marja Latvala +6
Neutron star (NS) masses and radii can be estimated from observations of photospheric radius-expansion X-ray bursts, provided the chemical composition of the photosphere, the spect…
The effect of accretion on the measurement of neutron star mass and radius in the low-mass X-ray binary 4U 1608-52
Juri Poutanen, Joonas Nättilä, Jari J. E. Kajava +4
Spectral measurements of thermonuclear (type-I) X-ray bursts from low mass X-ray binaries have been used to measure neutron star (NS) masses and radii. A number of systematic issue…