tokens: 2015 ). Although the SED of these CDs presents several overlapping features with a ‘normal’ SED of TDs, it would be misleading to treat them in a similar way. For instance, the implications for the presence of another star in the star--disc system entails an incorrect measurement of the luminosity and temperature, which translates into inaccurate age and mass estimates. This is the case of Coku Tau/4 and CS Cha that were originally described as TDs (Forrest et al. 2004 ; Espaillat et al. 2007 ), but eventually were presented as CDs (Guenther et al. 2007 ; Ireland Kraus 2008 ). This misclassification would be reflected in the estimation of birthplaces and time-scales for formation of sub-stellar companions (brown dwarfs) and/or planetary systems, and the demographic properties of these populations (e.g. Najita, Andrews Muzerolle 2015 ). Therefore, determining a more accurate relative picture of the lifetime of TDs and CDs requires a comprehensive survey capable of resolving close binaries ( ≲ 30 au) and measuring their frequency in objects previously classified as TDs through their SEDs. Although the open gap in the inner region of the disc might have different physical origins, in this paper we seek to identify if the dispersion of the primordial material in the inner region of the disc is a result of the tidal interaction between a close binary system and the disc. At small separations, detecting faint companions orbiting bright stars, that in addition, are surrounded by dusty material, can be challenging due to the high contrast between the companion and the primary star. However, observations of objects at early ages provide favourable IR contrast ratios for the detection of so far unresolved faint companions because of their intrinsically higher luminosity (Δ K 5 mag). We use the Non-Redundant Mask interferometry (NRM) technique and NIRC2 instrument located at the Keck II telescope, which offers a solution to reach angular resolutions with the necessary contrast and is resistant to speckle noise in the image by measuring a self-calibrating quantity known as closure phase (e.g. Martinache 2011 ). In order to achieve a higher accuracy in the detection limits of our data, the NRM completeness as a function of position and contrast utilizes a combination of a MonteCarlo Integration approach, giving a random sample of artificial binary stars, and Bayesian Inference , which uses prior probability density functions of the binary orbital parameters. We have restricted the selection of objects to regions with an age of ∼1–3 Myr and within a distance of about 220 pc. Taurus-Aurigae, IC348 region (Perseus) and Ophiucus star-forming regions satisfy these criteria (Loinard et al. 2008 ; Wilking, Gagné Allen 2008 ). This article is arranged as follows. In Section 2 , we present the motivation for the sample selection, description of observations together with the data analysis and a review of the target properties such as distance to the star-forming
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