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Attention is given to a population of 110 stars in the NGC 6611 cluster ofthe Eagle Nebula that have prominent near-infrared (NIR) excess and opticalcolours typical of pre-main sequence (PMS) stars older than 8 Myr. At leasthalf of those for which spectroscopy exists have a Halpha emission line profilerevealing active accretion. In principle, the V-I colours of all these starswould be consistent with those of young PMS objects (< 1 Myr) whose radiationis heavily obscured by a circumstellar disc seen at high inclination and insmall part scattered towards the observer by the back side of the disc.However, using theoretical models it is shown here that objects of this typecan only account for a few percent of this population. In fact, the spatialdistribution of these objects, their X-ray luminosities, their opticalbrightness, their positions in the colour-magnitude diagram and the weak Liabsorption lines of the stars studied spectroscopically suggest that most ofthem are at least 8 times older than the ~1 Myr-old PMS stars already known inthis cluster and could be as old as ~30 Myr. This is the largest homogeneoussample to date of Galactic PMS stars considerably older than 8 Myr that arestill actively accreting from a circumstellar disc and it allows us to set alower limit of 7% to the disc frequency at ~16 Myr in NGC 6611. These valuesimply a characteristic exponential lifetime of ~6 Myr for disc dissipation.

Pre-main sequence stars older than 8 Myr in the Eagle Nebula