The present work aims at performing a comprehensive census and
characterisation of the pre-main sequence (PMS) population in the cometary
cloud L1615/L1616, in order to assess the significance of the triggered star
formation scenario and investigate the impact of massive stars on its star
formation history and mass spectrum. Our study is based on UBVRcIc and JHKs
photometry, as well as optical multi-object spectroscopy. We performed a
physical parametrisation of the young stellar population in L1615/L1616. We
identified 25 new T Tauri stars mainly projected on the dense head of the
cometary cloud, almost doubling the current number of known members. We studied
the spatial distribution of the cloud members as a function of the age and
Hα emission. The star formation efficiency in the cloud is about 7-8 %,
as expected for molecular clouds in the vicinity of OB associations. The slope
of the initial mass function (IMF), in the mass range 0.1<M<5.5 M⊙, is
consistent with that of other T and OB associations, providing further support
of an universal IMF down to the hydrogen burning limit, regardless of
environmental conditions. The cometary appearance, as well as the high star
formation efficiency, can be explained in terms of triggered star formation
induced by the strong UV radiation from OB stars or supernovae shockwaves. The
age spread as well as both the spatial and age distribution of the PMS objects
provide strong evidence of sequential, multiple events and possibly still
ongoing star formation activity in the cloud.Comment: 59 pages, 14 figures, accepted for publication in Ap