[Everyone] MATINS (magneto-thermal evolutIon of isolated neutron stars in 3D): public release

[Nanda Rea]

Dear all,

Over the past decades, significant effort has been devoted to
understanding the evolution of isolated neutron stars during their
lifetimes, which presents challenges from both physical and numerical
perspectives. The temperature and magnetic field of neutron stars
evolve together in a complex way. Extremely strong magnetic fields
influence how heat flows through the star’s solid crust, channeling
thermal energy along preferred directions and insulating some regions
while exposing others. At the same time, these magnetic fields are not
static: they can change their geometry due to the Hall drift,  and as
they gradually decay, they release energy that can partially reheat
the star. Understanding this coupled magnetothermal evolution is
therefore essential to correctly interpret neutron-star observations,
and especially their apparent diversity.

Several magneto-thermal codes in the past had to choose to either
employ detailed microphysics in simplified (axially symmetric)
geometries or addressing fully three-dimensional configurations at the
expense of using more approximate physical assumptions. In the past
few years, we tried to overcome this by developing MATINS (MAgneto
Thermal evolutIon of Isolated NSs), funded by the European Research
Council (ERC 'MAGNESIA' No. 817661): a three-dimensional numerical
framework designed to model the magnetothermal evolution of the crust
of isolated neutron stars. MATINS computes the neutron star structure
by solving the Tolman–Oppenheimer–Volkoff equations for a range of
nuclear matter equations of state, enabling systematic studies across
different stellar masses. The code solves the induction equation in
the crust, including both Ohmic dissipation and Hall drift, to
describe magnetic-field evolution. This is coupled to a fully 3D
thermal cooling model based on state-of-the-art microphysical inputs:
conductivities, heat capacities, neutrino processes, with the options
of different superfluid and superconductive gap models. To solve the
governing equations in three-dimensional spherical geometry, MATINS
employs a finite-volume scheme on a cubed-sphere grid. Each radial
shell is covered by six smoothly connected patches, analogous to
inflating a cube into a sphere, thereby avoiding the coordinate
singularities at the axis of standard spherical coordinates. This new
framework stems directly from the 2D magneto-thermal code developed in
the past 20 years at the University of Alicante, adapted to a 3D grid
and with additional features including parallelization with openMP.
The code can be used to model a variety of observable properties of
isolated neutron stars, including X-ray thermal emission, surface
magnetic fields, temperature maps, and rotational evolution (spin
period and its derivative).

We are happy to announce the public release of the MATINS code that
can be now accessed at:
https://ice-csic-astroexotic.github.io/code/matins .

Details on how to install and run the code are also available at the
above website, together with the reference articles explaining more
technical details. For any queries you can write at:
matins at ice.csis.es . Apologies if you receive this message more than
once.

Best wishes,

Stefano Ascenzi
Clara Dehman
Davide De Grandis
José A. Pons
Nanda Rea
Daniele Viganò



______________________________________________________

Prof. Nanda Rea  | CSIC Research Professor
Instituto de Ciencias del Espacio (ICE, CSIC)
Institut d'Estudis Espacials de Catalunya (IEEC)
Email: rea at ice.csic.es; Tel: +34937379788 (ext: 430423)
_______________________________________________________
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