# A search for transits among the δ Scuti variables in Kepler

**Authors:** Daniel R. Hey, Benjamin T. Montet, Benjamin J. S. Pope, Simon J. Murphy, Timothy R. Bedding  
**arXiv:** [2108.03785](https://arxiv.org/abs/2108.03785)  
**Date:** 2021-08-09  
**Summary page:** https://www.summarizepaper.com/en/arxiv-id/2108.03785v1/

## Key points

- Hey et al. searched for transits around all known pulsating δ Sct variables with effective temperatures between 6500 K and 10,000 K in the long-cadence Kepler data.
- They developed a method to distinguish between low-frequency pulsations and transits in light curves by subtracting the pulsation signal through an automated routine.
- The authors identified three new candidate transit events that were previously hidden behind the pulsations but cautioned that they are likely to be false positive events.
- The team also examined the Kepler Objects of Interest catalog and identified 13 additional host stars showing δ Sct pulsations.
- For each star in their sample, they used the non-detection of pulsation timing variations for a planet known to be transiting a δ Sct variable to obtain both an upper limit on the mass of the planet and the expected radial velocity semi-amplitude of the host star.
- Simple injection tests of their pipeline imply 100% recovery for planets of 0.5 RJup or greater.
- The authors extrapolated their number of Kepler δ Sct stars and expect 12 detectable planets above 0.5 RJup in TESS.
- Hey et al made available their code and pulsation-subtracted light curves online to facilitate further analysis using Python packages such as astropy, matplotlib, and numpy.
- Techniques for dealing with coherent pulsations in light curves will be fundamental for searching for planets around hot variable stars.

## Summary

In their study, Hey et al. searched for transits around all known pulsating δ Sct variables with effective temperatures between 6500 K and 10,000 K in the long-cadence Kepler data. They developed a simple and computationally inexpensive method to distinguish between low-frequency pulsations and transits in light curves by subtracting the pulsation signal through an automated routine. The authors identified three new candidate transit events that were previously hidden behind the pulsations but cautioned that they are likely to be false positive events. The team also examined the Kepler Objects of Interest catalog and identified 13 additional host stars showing δ Sct pulsations. For each star in their sample, they used the non-detection of pulsation timing variations for a planet known to be transiting a δ Sct variable to obtain both an upper limit on the mass of the planet and the expected radial velocity semi-amplitude of the host star. Simple injection tests of their pipeline imply 100% recovery for planets of 0.5 RJup or greater. The authors extrapolated their number of Kepler δ Sct stars and expect 12 detectable planets above 0.5 RJup in TESS. Their sample contains some of the hottest known transiting planets around evolved stars, making it the first complete sample of transits around δ Sct variables. Despite finding a dearth of planetary candidates around A/F stars, Hey et al. 's pipeline is applicable to all space-based photometric missions such as TESS and PLATO which are expected to yield a massive amount of δ Sct variables across the sky. Techniques for dealing with coherent pulsations in light curves will be fundamental for searching for planets around hot variable stars. To facilitate further analysis using Python packages such as astropy (Astropy Collaboration et al., 2013), matplotlib (Hunter 2007), and numpy (Oliphant 2015), Hey et al made available their code and pulsation-subtracted light curves online. The study was accepted for publication in AAS journals.