VIPER - Velocity and IP EstimatoR

viper measures differential radial velocities from stellar spectra taken through iodine or other gas cells. It convolves the product of a stellar template and a gas cell spectrum with an instrumental profile. Via least square fitting, it optimizes the parameters of the instrumental profile, the wavelength solution, flux normalization, and the stellar Doppler shift. viper offers various functions to describe the instrumental profile such as Gaussian, super-Gaussian, skewed Gaussian or mixtures of Gaussians. Optional, it offers a forward modelling of telluric lines, allowing a fast and easy way of processing instruments operating e.g. in the NIR. The code is developed for echelle spectra; and additional instruments can easily be added. A graphical interface facilitates the work with numerous flexible options.

viper is developed by Mathias Zechmeister and Jana Köhler.

If you publish results with viper, please acknowledge it by citing its bibcode from https://ui.adsabs.harvard.edu/abs/2021ascl.soft08006Z.

  Supported Instruments

viper is working for different kinds of instruments in the optical and NIR (covering Y, J, H and K band), no matter of existing gas cell or not. Currently, the following instruments are implemented:

• CES - Coudé Echelle Spectrometer @La Silla
• CRIRES+ - CRyogenic high-resolution InfraRed Echelle Spectrograph @VLT
• GIANO-B - Near-Infrared High Resolution Spectrograph of the TNG @La Palma
• HIRES - High Resolution Echelle Spectrometer @KECK
• OES - Ondrejov Echelle Spectrograph @Ondrejov
• TCES - Tautenburg Coudé Echelle Spectrometer @Tautenburg
• Tull - Tull Coudé Spectrograph @Mc Donald
• UVES - Ultraviolet and Visual Echelle Spectrograph @VLT

If you are interested in using viper for another instrument, please contact us.

  Release Notes

viper 1.1 (2024-01-08):

• Official release of viper.
• Option of using configure files with parameter settings added.
• Option of masking wavelength regions in flag file added.
• Atmosphere data for entire range from visible to K-band added.
• Added GIANO-B instrument.
• Some bug fixes.

viper 0.9 (2023-09-15):

• Early release version. It is made publicly available in order to collect feedback from a larger group of users.

  Downloads

viper can be downloaded from the Github page:

Github VIPER

The manual and test report can be downloaded from:

Manual (last update: 2024-01-08)

Test Report (last update: 2024-01-08)

Test data for CRIRES+ and TCES can be downloaded from:

Demo data

  Installation

Prerequisites

• viper runs with Python3, using common standard packages.

Use pip

• Download viper from Github link above
• Enter the directory
• pip install -e .

Run viper with:

• python3 -m viper [options]

  Getting Support

In case of bugs, questions or requests for feature options or instruments, send email to viper@uni-goettingen.de starting the subject with VIPER. While reporting a bug, please include the following information:

• the viper version used
• the instrument used
• the command used
• the config file, if differing from the default
• the appearing error message
• optionally, the data set used