# VaST: a variability search toolkit

## TL;DR

VaST is a versatile software toolkit for detecting variable objects in sky images, capable of handling complex distortions and non-linear detectors, and has discovered around 1800 variable stars across various telescopes.

## Contribution

It introduces a flexible variability search method relying on source list matching instead of image subtraction, suitable for diverse imaging conditions and detectors.

## Key findings

- Discovered approximately 1800 variable stars.
- Successfully applied to images from telescopes of 0.08 to 2.5m.
- Effective in transient detection for the NMW nova patrol.

## Abstract

Variability Search Toolkit (VaST) is a software package designed to find variable objects in a series of sky images. It can be run from a script or interactively using its graphical interface. VaST relies on source list matching as opposed to image subtraction. SExtractor is used to generate source lists and perform aperture or PSF-fitting photometry (with PSFEx). Variability indices that characterize scatter and smoothness of a lightcurve are computed for all objects. Candidate variables are identified as objects having high variability index values compared to other objects of similar brightness. The two distinguishing features of VaST are its ability to perform accurate aperture photometry of images obtained with non-linear detectors and handle complex image distortions. The software has been successfully applied to images obtained with telescopes ranging from 0.08 to 2.5m in diameter equipped with a variety of detectors including CCD, CMOS, MIC and photographic plates. About 1800 variable stars have been discovered with VaST. It is used as a transient detection engine in the New Milky Way (NMW) nova patrol. The code is written in C and can be easily compiled on the majority of UNIX-like systems. VaST is free software available at http://scan.sai.msu.ru/vast/