iSpec now exclusively uses Python 3 (previous versions of Python were deprecated on January 1st 2020). The v2020.10.01 release does not remove or modify any of iSpec functionalities. It should be completely compatible with user written scripts as far as they are converted to Python 3.

In addition, most radiative transfer codes were updated, as well as the external Equivalent Width measurement tool (ARES), and the Gaia-ESO linelist version 6 was added. Regarding the input file, pre-computed grids were re-computed using the latest radiative transfer code versions, and line selections were re-done for a resolution of 47,000.

Summary:

  • Python 3
  • Updated SPECTRUM to v2.77
  • Updated Turbospectrum to v19.1
  • Updated MOOG to November 2019 version
  • Updated SME to v574
  • Updated ARES to June 28th 2020 commit
  • Added Gaia-ESO linelist v6


Multiple codes are available to derive atmospheric parameters and individual chemical abundances from high-resolution spectra of AFGKM stars. Almost every spectroscopist has its own preferences regarding which code and method to use. But intrinsic differences between codes and methods lead to complex systematics that depend on multiple variables such as the selected spectral regions and the radiative transfer code used. I expanded iSpec, the popular open source spectroscopic tool, to support the most known radiative transfer codes and I assessed their similarities and biases when using multiple setups based on the equivalent width method and the synthetic spectral fitting technique (interpolating from a pre-computed grid of spectra or synthesizing with interpolated model atmospheres). This work shows that systematics on atmospheric parameter and abundances between most of the codes can be reduced when using the same method and a careful spectral feature selection is executed, but it may not be possible to ignore the remaining differences depending on what is the scientific case and the required precision. Regarding methods, equivalent width-based and spectrum fitting-analyses exhibit large differences that emerge due to their intrinsic differences, which is relevant given the popularity of these two methods. The results help us identify the key caveats of modern spectroscopy that any scientist should be aware of before trusting its own results or being tempted to combine atmospheric parameters and abundances from the literature.

Access to the article preprint and the ADS record.


The University of Wroclaw (Poland) is pleased to announce the international summer school "Spectroscopic data analysis with iSpec". That will take place in Wroclaw, Poland between 26 and 29 June 2018.

The aim of this school is to give participants a thorough introduction into the treatment and analysis of stellar spectra, including deriving the atmospheric parameters and the chemical abundances. The tool which will be used for this purpose is the code iSpec.

iSpec is a tool for the treatment and analysis of stellar spectra. Some of the main functionalities for spectra treatment and library creation that are integrated into iSpec are the following: cosmic rays removal, continuum normalization, resolution degradation, radial velocity determination and correction, telluric lines identification, re-sampling. iSpec is also capable of determining atmospheric parameters (i.e effective temperature, surface gravity, metallicity, micro/macroturbulence, rotation) and individual chemical abundances for FGKM stars by using two different approaches: synthetic spectra fitting technique or equivalent widths method. iSpec integrates MARCS and ATLAS model atmospheres together with the following radial transfer codes: SPECTRUM (R. O. Gray), Turbospectrum (Bertrand Plez), SME (Valenti & Piskunov), MOOG (Chris Sneden), and Synthe/WIDTH9 (Kurucz/Atmos). The user-friendly interface is perfect for learning and testing. However, to take advantage of the full potential, iSpec can be used from Python. This is the recommended way to use iSpec for complex scientific studies, it ensures reproducibility and give access to a wider range of functionalities and options.

The participants of the school "Spectroscopic data analysis with iSpec" will be given introductory lectures to iSpec and some hands-on experience with determination of the atmospheric parameters of A, F, G, K, and M type stars. The exercises will be based on publicly available stellar spectra as well as on pre-computed synthetic spectra.


Planetary systems with several planets in compact orbital configurations such as TRAPPIST-1 are surely affected by tidal effects. Its study provides us with important insight about its evolution. We developed a second generation of a N-body code based on the tidal model used in Mercury-T, re-implementing and improving its functionalities using Rust as programming language (including a Python interface for easy use) and the WHFAST integrator. The new open source code ensures memory safety, reproducibility of numerical N-body experiments, it improves the spin integration compared to Mercury-T and allows to take into account a new prescription for the dissipation of tidal inertial waves in the convective envelope of stars. Posidonius is also suitable for binary system simulations with evolving stars.

Links: Article, Github, Documentation.


The astrophysics community uses different tools for computational tasks such as complex systems simulations, radiative transfer calculations or big data. Programming languages like Fortran, C or C++ are commonly present in these tools and, generally, the language choice was made based on the need for performance. However, this comes at a cost: safety. For instance, a common source of error is the access to invalid memory regions, which produces random execution behaviors and affects the scientific interpretation of the results.

In 2015, Mozilla Research released the first stable version of a new programming language named Rust. Many features make this new language attractive for the scientific community, it is open source and it guarantees memory safety while offering zero-cost abstraction.

We explore the advantages and drawbacks of Rust for astrophysics by re-implementing the fundamental parts of Mercury-T, a Fortran code that simulates the dynamical and tidal evolution of multi-planet systems.

Links: Article, Benchmark codes, Hacker news and Rust subreddit comments.