Abstract:
We present the time series photometry of stars located in the extremely young open cluster
Berkeley 59. Using the 1.04-m telescope at Aryabhatta Research Institute of Observational
Sciences (ARIES), Nainital, we have identified 42 variables in a field of ∼13 × 13 arcmin²
around the cluster. The probable members of the cluster have been identified using a (V, V −
I) colour–magnitude diagram and a (J − H, H − K) colour–colour diagram. 31 variables
have been found to be pre-main-sequence stars associated with the cluster. The ages and
masses of the pre-main-sequence stars have been derived from the colour–magnitude diagram
by fitting theoretical models to the observed data points. The ages of the majority of the
probable pre-main-sequence variable candidates range from 1 to 5 Myr. The masses of these
pre-main-sequence variable stars have been found to be in the range of ∼0.3 to ∼3.5 Mꙩ , and
these could be T Tauri stars. The present statistics reveal that about 90 per cent T Tauri stars
have period <15 d. The classical T Tauri stars are found to have a larger amplitude than the
weak-line T Tauri stars. There is an indication that the amplitude decreases with an increase
in mass, which could be due to the dispersal of the discs of relatively massive stars.
