GASTON-GP. Source catalogue and millimetre variability of massive protostellar objects

The processes governing protostellar mass growth remain debated, although episodic accretion is now understood as a key feature of protostellar evolution across all masses. Luminosity bursts have been observed in both low- and high-mass protostars, but the overall statistics remain limited, especially for high-mass objects. Over the past decade, numerical simulations of high-mass core collapse have provided a theoretical framework for interpreting protostellar variability, yet additional observational constraints are required to determine the characteristics and importance of bursts. In this work, we analyse data from GASTON-GP programme, which mapped a 2.4 deg(Formula presented) region of the Galactic plane (centred at (Formula presented) ) at 1.15 and 2.00 mm using New IRAM KID Array 2 (NIKA2) on the Institut de radioastronomie millimétrique (IRAM) 30 m telescope. The survey obtained 11 epochs over 4 yr, offering the first opportunity to study millimetre variability in a large sample of massive protostellar sources. From the combined data set, we constructed catalogues of 2925 compact sources at 1.15 mm and 1713 at 2.00 mm. Using a dedicated relative calibration scheme, we generated millimetre light curves for 200 high-signal-to-noise sources and identified one variable candidate. However, it is not protostellar. Consequently, we report no robust detections of variable protostellar sources in GASTON field. This is the direct consequence of observational limitations (i.e. sensitivity, resolution) combined with the lack of any >100-fold luminosity bursts during the observations, which is consistent with estimates inferred from isolated core collapse simulations. This study highlights the need for future high-resolution, high-cadence surveys to constrain the accretion histories of massive protostars.