The potential for super-Nyquist asteroseismology with TESS

TL;DR

This paper proposes a method to overcome Nyquist frequency limitations in TESS data for asteroseismology by intentionally introducing a short idle period after downlinks, enabling the recovery of high-frequency stellar oscillations.

Contribution

It introduces a novel observational strategy involving a brief idle period after TESS downlinks to resolve Nyquist ambiguities in asteroseismology data.

Findings

Nyquist ambiguities can be mitigated with a five-minute idle period after downlinks.

Imperfect cadence can improve phase coverage of transit events.

Method allows recovery of high-frequency oscillations without additional observing slots.

Abstract

The perfect 30-min cadence of the full-frame images from the Transiting Exoplanet Survey Satellite (TESS) will impose a hard Nyquist limit of 24 d$^{-1}$ ($\approx 278$ $\mu$Hz). This will be problematic for asteroseismology of stars with oscillation frequencies at or around that Nyquist limit, which will have insurmountable Nyquist ambiguities. TESS does offer some observing slots at shorter cadences, but these will be limited in number and competitive, while the full frame images will be the main data product for many types of variable stars. We show that the Nyquist ambiguities can be alleviated if, when TESS resumes observations after a downlink, integrations are not resumed at perfect cadence with those before the downlink. The time spent idling before integrations are resumed need only be around five minutes for satisfactory results, and observing time can be recouped from the downlink event if the telescope does not wait for a return to perfect cadence before resuming integrations. The importance of imperfect cadence after downlink is discussed in light of phase coverage of transit events.