Colour-magnitude diagrams reveal a population of blue (hot) sub-luminous objects with respect to the main sequence. These hot sub-luminous stars are the result of evolutionary processes that require stars to expel their obscuring, hydrogen-rich envelopes to reveal the hot helium core. As such, these objects offer a direct window into the hearts of stars that are otherwise inaccessible to direct observation. We showcase MeerLICHT's capabilities of detecting faint hot subdwarfs and identifying the dominant frequency in the photometric variability of these compact hot stars, in comparison to their $Gaia$ DR3 data. We hunt for oscillations, which will be an essential ingredient for accurately probing stellar interiors in future asteroseismology. Comparative MeerLICHT and $Gaia$ colour-magnitude diagrams are presented as a way to select hot subdwarfs from our sample. A dedicated frequency determination technique is developed and applied to the selected candidates to determine their dominant variability using time-series data from MeerLICHT and $Gaia$ DR3. We explore the power of both datasets in determining the dominant frequency. Using the $g-i$ colour, MeerLICHT offers a colour-magnitude diagram that is comparable in quality to that of $Gaia$ DR3. The MeerLICHT colour-colour diagrams allow for the study of different stellar populations. The frequency analysis of MeerLICHT and $Gaia$ DR3 data demonstrates the superiority of our MeerLICHT multi-colour photometry in estimating the dominant frequency compared to the sparse $Gaia$ DR3 data. MeerLICHT's multi-band photometry leads to the discovery of high-frequency faint subdwarfs. Our MeerLICHT results are a proof-of-concept of the capacity of the BlackGEM instrument currently in the commissioning stage at ESO's La Silla Observatory in Chile.

翻译：颜色-星等图揭示了主序带之外一群蓝色（高温）亚光天体。这些热亚矮星是恒星演化过程的产物——恒星需抛掷其遮蔽视线的富氢包层，暴露出炽热的氦核。因此，这类天体为直接观测恒星内部提供了独特的窗口，而这种观测在其它情况下难以实现。通过对比盖亚DR3数据，我们展示了MeerLICHT在探测暗弱热亚矮星及识别这些致密热星光变主导周期方面的能力。我们搜寻振荡信号，这将为未来星震学精确探测恒星内部结构提供关键要素。通过比较MeerLICHT与盖亚DR3的颜色-星等图，我们建立了从样本中筛选热亚矮星的方法。针对选定的候选体，我们开发了专门的频率测定技术，并利用MeerLICHT与盖亚DR3的时序数据确定其主导变率。我们探究了两套数据集在主导频率测定中的效能。采用g-i色指数时，MeerLICHT提供的颜色-星等图质量与盖亚DR3相当。MeerLICHT颜色-颜色图则可用于研究不同恒星种群。对MeerLICHT与盖亚DR3数据的频率分析表明，相较于稀疏的盖亚DR3数据，我们的MeerLICHT多色测光在主导频率估算中具有显著优势。MeerLICHT多波段测光成功发现了高频暗弱亚矮星。本研究作为概念验证，展现了目前正在智利ESO拉西拉天文台调试阶段的BlackGEM仪器的探测能力。