  T Tauri stars are low-mass pre-main sequence stars that are intrinsically
variable. Due to the intense magnetic fields they possess, they develop dark
spots on their surface that, because of rotation, introduce a periodic
variation of brightness.In addition, the presence of surrounding disks could
generate flux variations by variable extinction or accretion. Both can lead to
a brightness decrease or increase, respectively. Here, we have compiled a
catalog of light curves for 379 T Tauri stars in the Lagoon Nebula (M8) region,
using VVVX survey data in the Ks-band. All these stars were already classified
as pre-MS stars based on other indicators. The data presented here are spread
over a period of about eight years, which gives us a unique follow-up time for
these sources at this wavelength. The light curves were classified according to
their degree of periodicity and asymmetry, to constrain the physical processes
responsible for their variation. Periods were compared with the ones found in
literature, on a much shorter baseline. This allowed us to prove that for 126
stars, the magnetically active regions remain stable for several years.
Besides, our near-IR data were compared with the optical Kepler/K2 light
curves, when available, giving us a better understanding of the mechanisms
responsible for the brightness variations observed and how they manifest at
different bands. We found that the periodicity in both bands is in fairly good
agreement, but the asymmetry will depend on the amplitude of the bursts or dips
events and the observation cadence.
