Field Guide¶
This guide provides detailed information about the different types of variable sources classified by SCoPe, along with examples of bogus variability.
Introduction¶
Classification of time-domain sources can be approached in many different ways. SCoPe uses a two-branch taxonomy (see Coughlin et al. 2021, arXiv:2102.11304):
- Phenomenological classes describe what the light curve looks like — periodic, irregular, sinusoidal, sawtooth, eclipsing, etc. These can be assigned from photometry alone.
- Ontological classes describe what the object physically is — RR Lyrae, W UMa, Cepheid, CV, YSO, etc. These often require additional information beyond the light curve (colors, absolute magnitudes, spectral type, host environment).
In practice, classes overlap. A W UMa contact binary is simultaneously an eclipsing variable (phenomenological) and a non-accreting binary (ontological). An RR Lyrae ab is both a sawtooth variable and a pulsator. The field guide pages below describe both the observational signatures and the physical nature of each class where applicable.
Using this guide¶
Each field guide page includes:
- Classification and numbers: where the class sits in the taxonomy hierarchy and how common it is
- ZTF light curves: example light curves generated from Kowalski
- Light curve characteristics: period range, amplitude, and morphology to look for
- HR and sky diagrams: where these objects fall in color-magnitude space and on the sky
- References: key papers for further reading
Additional resources¶
- Interactive taxonomy visualization — expandable tree view of the full SCoPe taxonomy
- Sterken & Jaschek, Light Curves of Variable Stars — comprehensive atlas of variable star light curves
- AAVSO Variable Star Index (VSX) — catalog of known variable stars with classifications
- Gaia DR3 variability classification — all-sky variable star catalog