TESS variability of B-type supergiants in the Galaxy

The blue supergiants (BSGs) span phases between the main sequence and the late stages of massive stars, which makes them valuable
for refining our knowledge on the diverse channels that cross the upper evolutionary diagram. By linking the variability properties of these objects to
the accurate stellar parameters, we aim to improve constraints on their interior physics and on the modeling of the post-main-sequence evolution.
We conducted a variability study of Galactic B-type BSGs with known spectroscopic parameters and own derived luminosities using photometry
from the Transiting Exoplanet Survey Satellite. We described the time domain of the stars by means of different statistical measures, and the
frequency domain via extraction of the dominant frequencies and modeling of the ubiquitous stochastic low-frequency (SLF) variability. A significant
positive trend is found between the TESS data amplitudes and the luminosities. This correlation is tighter for the less luminous BSGs, which
display frequencies that comply with the rotational ones, suggesting variability that is driven by a structured wind. On the other hand, the more
luminous objects are mixed with pulsators of the α Cyg class, displaying diverse and/or time-variant photometric properties. Furthermore, we report
a positive significant trend between the SLF variability amplitude and the spectroscopic temperature, indicating an influential role that the stellar age
plays on the emergence of the background signal -beyond- the main sequence. Finally, a weak positive trend is seen between the SLF variability
amplitude and the intrinsic brightness yet for the less luminous BSGs, suggesting an excitation mechanism that depends weakly on metallicity.
Notably, the α Cyg variables display a suppressed SLF variability, which we suggest that it mirrors their rather advanced evolutionary stage as post-red
supergiants.