We present narrow-band photometric measurements of the exoplanet GJ 1214b using the 10.4Â m Gran Telescopio Canarias ( GTC ) and the OSIRIS instrument .
Using tuneable filters we observed a total of five transits , three of which were observed at two wavelengths nearly simultaneously , producing a total of eight individual light curves , six of these probed the possible existence of a methane absorption feature in the 8770Â –Â 8850Â Ã Â region at high resolution .
We detect no increase in the planet-to-star radius ratio across the methane feature with a change in radius ratio of \Delta \overline { R } = -0.0007 \pm 0.0017 corresponding to a scale height ( H ) change of -0.5 \pm 1.2 ~ { } H across the methane feature , assuming a hydrogen dominated atmosphere .
We find a variety of water and cloudy atmospheric models fit the data well , but find that cloud-free models provide poor fits .
These observations support a flat transmission spectrum resulting from the presence of a high-altitude haze or a water-rich atmosphere , in agreement with previous studies .
In this study the observations are predominantly limited by the photometric quality and the limited number of data points ( resulting from a long observing cadence ) , which make the determination of the systematic noise challenging .
With tuneable filters capable of high resolution measurements ( R \approx  600–750 ) of narrow absorption features , the interpretation of our results are also limited by the absence of high resolution methane models below 1 \mu m .