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# RR Lyrae Templates

Fit templates to RR Lyrae to estimate star variability parameters. The code takes data like this:

![alt text](figs/sdss.png "SDSS Stripe 82 RR Lyrae Light Curve")

and outputs 5 parameters (distance modulus, dust, amplitude, frequency, and phase) which can be used to construct the folded light curve:

![alt text](figs/sdss_folded.png "SDSS Stripe 82 RR Lyrae Folded Light Curve")

The model is designed to work even on very sparsely sampled light curves. Fitting the model to this Dark Energy Survey RR Lyrae

![alt text](figs/des.png "DES Light Curve")

we determine it has a period about 0.54 days, distance modulus of 19.2 and folded light curve:

![alt text](figs/des_folded.png "DES Folded Light Curve")


## Using the Software

The fitting code is written in R. This software includes demonstrations in both R and python (via `rpy2`) in the files `demo_R.ipynb` and `demo_python.ipynb`.

The templates were constructed by James Long (jplong@mdanderson.org). Please contact with questions or bug reports. The code used to construct the templates (from SDSS Stripe 82 RR Lyrae) is available from Long upon request.


## License and Citation

This software is covered by an MIT license. See the LICENSE file for details.

These templates were constructed for and used in [Stringer et. al. 2019](https://doi.org/10.3847/1538-3881/ab1f46). Please cite this work if you use the templates for any publications.