Pulsating pre-MS stars in the young open cluster NGC 2264: V588 Monocerotis and V589 Monocerotis

We report on the first high-accuracy, photometric multisite campaign to study the two, first-detected pulsating, pre-main sequence stars V588 Mon and V589 Mon in the direction of the young open cluster NGC 2264. We carried out the campaign from November 2002 to February 2003 with a photometric coverage of about 216 h at four observatories. A detailed frequency analysis results in well-populated eigenspectra, typical for delta Scuti type pulsation, with 16 and 20 significant frequencies in the V588 Mon and V589 Mon data, respectively. Using Strogrem uvby beta photometry and spectroscopic observations as well as published Geneva and infrared photometry feasible fundamental parameters we deduced, placing both stars in the d Scuti instability strip and giving strong evidence that both stars are members of NGC 2264 and are indeed in their pre-main sequence phase of evolution.