Alpha Cygni Variables as Seen from the Transiting Exoplanet Survey Satellite

TL;DR

This study analyzes TESS light curves of 75 Alpha Cygni variables to identify candidates for further observation, compare data processing pipelines, and enhance understanding of their variability characteristics.

Contribution

It provides the first systematic analysis of TESS data for ACYG variables, identifying potential candidates for ground-based monitoring and evaluating data processing methods.

Findings

Identified 10 ACYG stars similar to Deneb for follow-up studies.

Most ACYG stars lie below the Luminous Blue Variables in the HR diagram.

Compared different data pipelines and discussed their effectiveness for ACYG analysis.

Abstract

The Alpha Cygni (ACYG) variables are blue-white supergiants which display low-amplitude brightness variations of around 0.1 magnitude. The prototype Deneb shows quasi-periodic variations of around 12 days, interrupted by intervals of erratic variability, and occasionally large excursions in amplitude. To gain insight on the behavior of these variables, we examined 27-day light curves from the Transiting Exoplanet Survey Satellite (TESS) for 75 ACYG variables south of the ecliptic plane which are being revisited by TESS in 2025-2026. We use the web-based TESS Extractor app for screening TESS light curves. We identified ten stars with similarities to Deneb that may be good candidates for ground-based monitoring. We approximated the location of these stars on the Hertzsprung-Russell diagram, and find most lie below the Luminous Blue Variables, are cooler than the beta Cephei variables, and are hotter than the RV Tauri stars. We also compare light curves processed with several different pipelines available on the Mikulski Archive for Space Telescopes (MAST) and comment on their utility for ACYG stars.