Infrared variability of young solar analogs in the Lagoon Nebula

TL;DR

This study presents a comprehensive eight-year near-infrared variability catalog of 379 T Tauri stars in the Lagoon Nebula, analyzing their light curves to understand the physical processes behind their brightness variations.

Contribution

It provides the first long-term near-IR variability analysis of T Tauri stars in the Lagoon Nebula, comparing optical and infrared data to identify stable magnetic activity regions.

Findings

126 stars have stable magnetic regions over several years

Periodicities in IR and optical bands are in good agreement

Brightness variation asymmetries depend on burst/dip amplitudes and observation cadence

Abstract

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.