slice

This is a piece of code published alongside the paper Lisogorskyi et al. 2019, MNRAS, 485, 4804 (DOI:10.1093/mnras/stz694, arXiv:1902.10711).

The code measures active lines equivalent width changes and asymmetries in HARPS (High Accuracy Radial Velocity Planet Searcher) spectra. These lines were identified as "active" using 2010 observations of α Centauri B (see the paper for details). Some example spectra are included in this repository.

Dependencies

Python 3.x and packages:

• numpy
• pandas
• scipy
• astropy
• matplotlib
• joblib

Usage

The code is not a package and doesn't need installation, just clone the repository.

run

Run the code with python slice in the repository.

results

The results are written to the data/results.dat file. It will contain a table with all the spectral lines. The columns are:

name, center - species and rest frame wavelength of a line in Angstrom

ew, ew_diff - equivalent width and the amplitude of its variation, in Angstrom

asym_diff - amplitude of asymmetry variation, measures as flux difference between thr right and left wings of a line

logS_ew_p, logS_ew_pp - two-tailed Pearson correlation, S-index and equivalent width of the line

logS_asym_p, logS_asym_pp - two-tailed Pearson correlation, S-index and asymmetry of the line

rv_ew_p, rv_ew_pp - two-tailed Pearson correlation, radial velocity and equivalent width of the line

rv_asym_p, rv_asym_pp - two-tailed Pearson correlation, radial velocity and asymmetry of the line

Time series results of each line is in data/results folder, filenames containing wavelength of the line in 100 * Angstrom (to avoid decimal point) and the species of the line for readability. Each file contains:

filename - name of the spectrum file the value was measured from

bjd - Barycentric Julian Date, in days

ew - equivalent width of the line in Angstrom

asym - asymmetry of the line

settings

The code relies on a few settings (and files) that have default values for demonstration purposes. These are set in slice/settings.py:

lines_list_path - a file containing the list of lines to measure and spectral ranges to measure the continuum and the line from, defined by 6 wavelengths from left to right (default/example: data/active_lines.dat)

list_path - radial velocity and S-index values for the spectra (default/example: data/rvdata.dat)

s1d_folder - folder containing the _s1d_ spectra (default/example: data/s1d/)

output_path - output directory for the individual line files (default/example: data/results/)

summary_file - summarized table with variation fo all the lines (default/example: data/results.dat)

plots_path - output plots directory (default/example: data/plots/)

template_n - number of spectra with the lowest S-index to average for a low activity template (default/example: 10)

ncores - number of cores to utilize (default/example: 2)