Details of the eleanor Pipeline

These slides were presented virtually at the Earth 2.0 workshop I on December 10, 2020.

Transcript

1. Unpacking eleanor, a Python tool for TESS FFI light curve extraction Adina Feinstein, Benjamin Montet, Dan Foreman-Mackey, Megan Bedell, Nicholas Saunders, Jacob Bean, Jessie Christiansen, Christina Hedges, Rodrigo Luger, Daniel Scolnic, José Vinícius de Miranda Cardoso !1 December 10, 2020 ET Workshop @afeinstein20
2. !2 Image Credit: Ethan Kruse The TESS FFIs cover ~107 stars brighter than Tmag < 16.
3. eleanor was really designed with the user in mind. !3 • Flexibility • Durability • Open source • Well documented • Easy to integrate with other software
4. What steps are taken to extract and create a light curve? !4 • Background estimation & subtraction • Aperture selection • Creation of quality flags • Detrending using co-trending basis vectors (CBVs) • Optimization of light curve for transit searches
5. What steps are taken to extract and create a light curve? !5 • Background estimation & subtraction • Aperture selection • Creation of quality flags • Detrending using co-trending basis vectors (CBVs) • Optimization of light curve for transit searches
6. The eleanor pipeline takes the FFIs and breaks them into smaller, more space manageable “postcards.” !6
7. Background approach #1: We mask the stars and estimate a constant background from each cadence across the postcard. !7
8. Background approach #2: After masking bright sources, we linearly interpolate across the postcard to model the expected background. !8
9. The modeled pixel values are subtracted from the TPF before the light curve is created. !9
10. Background approach #3: We estimate a constant background from each cadence from the Target Pixel File (TPF). !10
11. There is a difference between the postcard and TPF estimated 1D backgrounds, but both capture large features nicely. !11
12. We store each of the three backgrounds in the eleanor FITS file and indicate the best background through the header keyword `BKG_LVL`. !12
13. What steps are taken to extract and create a light curve? !13 • Background estimation & subtraction • Aperture selection • Creation of quality flags • Detrending using co-trending basis vectors (CBVs) • Optimization of light curve for transit searches
14. We test out a variety of aperture shapes, sizes, and pixel weightings for each target. !14
15. We limit faint (Tmag > 13) targets to the smallest apertures in the library. !15
16. And we do the reverse for the brightest 
 (Tmag < 8) targets as well. !16
17. What steps are taken to extract and create a light curve? !17 • Background estimation & subtraction • Aperture selection • Creation of quality flags • Detrending using co-trending basis vectors (CBVs) • Optimization of light curve for transit searches
18. Quality flags are taken from the 2-minute targets and we create our own from regions with large, non-astrophysical centroid motions and bad background. !18
19. The centroid motion is tracked from the pointing model we create per each sector. !19
20. What steps are taken to extract and create a light curve? !20 • Background estimation & subtraction • Aperture selection • Creation of quality flags • Detrending using co-trending basis vectors (CBVs) • Optimization of light curve for transit searches
21. The co-trending basis vectors are provided by the SPOC pipeline. We bin them down to 30-minutes to work with the FFIs. !21
22. The eleanor light curves are optimized for transit searches by calculating the combined differential photometric precision (CDPP). !22 eleanor corrected flux light curve for CDPP calculation
23. !23 There are 4 light curves set as the default per each method in eleanor.
24. Each light curve was processed with a different technique. !24
25. The raw flux has only the background removed and no other processing. !25
26. The corrected flux is a combination of CBVs and regressing against a linear model of position, background, and time. !26
27. The PCA flux detrends the raw flux by only applying the CBVs. !27
28. The eleanor software allows for PSF modeling of light curves. This is not available in the data product. !28
29. There are pros and cons to each of the flux options created through eleanor. !29 Raw Corrected PCA PSF Transits/eclipses x x x Long term trends x x Short term variability x x Solar system science x
30. eleanor was really designed with the user in mind. !30 • Flexibility • Durability • Open source • Well documented • Easy to integrate with other software
31. We provide every raw & corrected light curve for each aperture tested. !31
32. Software users are also able to input their own apertures and apply all of the eleanor detrending techniques. !32
33. The eleanor software also includes visualization tools developed to make light curve vetting easier. !33
34. eleanor was really designed with the user in mind. !34 • Flexibility • Durability • Open source • Well documented • Easy to integrate with other software
35. Maintaining an open source package leads to community-driven improvements. !35
36. eleanor was really designed with the user in mind. !36 • Flexibility • Durability • Open source • Well documented • Easy to integrate with other software
37. By creating thorough example notebooks, and updating them as we learned, makes it easy for users to explore their own science with our tool. !37
38. eleanor was really designed with the user in mind. !38 • Flexibility • Durability • Open source • Well documented • Easy to integrate with other software
39. One of the biggest lessons learned is to check different light curves to make sure your source is truly astrophysical. !39 OS19 = Oelkers & Stassun (2019) TASOC = TESS Asteroseismic Science Consortium
40. We’ve incorporated functions to easily input eleanor light curve outputs to lightkurve objects. !40
41. eleanor Resources !41 • PASP paper: https://ui.adsabs.harvard.edu/abs/2019PASP..131i4502F/abstract • Documentation: http://adina.feinste.in/eleanor • GitHub: https://github.com/afeinstein20/eleanor • YouTube Tutorial: https://www.youtube.com/watch?v=xpvniFrA6V0 • ET Google Colab Notebook: https://bit.ly/3mXY9ex