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The magnetic activity of low-mass stars changes as they age. The primaryprocess decreasing the stellar activity level is the angular momentum loss viamagnetized stellar wind. However, processes like tidal interactions betweenstars and their close companions may slow down the braking effect and thesubsequent decrease of the activity level. Until now, the tidal impact ofsubstellar objects like brown dwarfs on the evolution of their central starshas not been quantified. Here, we analyse the X-ray properties of NLTT 41135,an M dwarf tightly orbited by a brown dwarf, to determine the impact of tidalinteractions between them. We find that NLTT 41135 is more than an order ofmagnitude brighter in the X-ray regime than its stellar companion NLTT 41136,also an M dwarf star, with whom it forms a wide binary system. To characterizethe typical intrinsic activity scatter between coeval M dwarf stars, we analysea control sample of 25 M dwarf wide binary systems, observed with XMM-Newtonand Chandra telescopes and the eROSITA instrument onboard the SpectrumR\"ontgen Gamma satellite. The activity difference in the NLTT 41135/41136system is a $3.44 \sigma$ outlier compared to the intrinsic activity scatter ofthe control systems. Therefore, the most convincing explanation for theobserved activity discrepancy is tidal interactions between the M dwarf and itsbrown dwarf. This shows that tidal interactions between a star and a substellarcompanion can moderately alter the expected angular-momentum evolution of thestar, making standard observational proxies for its age, such as X-rayemission, unreliable.

The first evidence of tidally induced activity in a brown dwarf-M dwarf pair: A Chandra study of the NLTT 41135/41136 system