VIMOS@VLT observations of Dolidze 25 Vincenzo Ripepi INAF-Osservatorio Astronomico di Capodimonte, Naples, Italy Collaborators: J.M. Alcalá, F.Cusano, M. Marconi (INAF-OAC) LOI partecipants-PMS collaboration EGBW

Primary interest the search for PMS  Scuti candidates for COROT Motivation Primary interest the search for PMS  Scuti candidates for COROT  Interest for young open cluster (age < 10 Myr) in the vicinity of COROT Primary targets, i.e. observed in any case in the EXO field.

Dolidze 25: Properties Dolidze 25 is a young cluster associated with the HII region S284 it is far (heliocentric distance > 5.5 Kpc) it is metal poor: Lennon et al. 1990 found that Dolidze 25 is deficient in metals approximately by a factor 6  somewhat in disagreement with respect to the expected abundance gradient of the disc. Dolidze 25 could be connected with the Canis Major Dwarf Galaxy which is supposed to be merging with our Galaxy Dolidze 25 is poorly studies as a SFR. Due to the low metallicity, it represent an ideal object to study matal deficient PMS objects, which would be the counterpart of “normal” TTauri and intermediate mass PMS. Spectral classification (using spectra) for a relevant number of stars  useful for characterize stars in the exo field.

Observations: Imaging Observations in RI with VIMOS@VLT (pre-Imaging data) Data reduction using psf photometry DAOPHOT/ALLSTAR (Stetson 1987) Accurate photometric calibrations using Stetson’s extension of Landolt (1992) standards. Pre-Imaging (+2MASS data+EGBW data) used to select targets for the spectroscopy. High priority to objects showing IR excess. Galactic model by Cignoni & Degl’Innocenti, Private Comm.

Observations:multiobject spectroscopy Medium Resolution: 2.5 Å/pixel (spectral reange 5050-8700 Å)  up to 50 slits per CCD, i.e up to 200 per exposure High Resolution Red: 0.6 Å/pixel (spectral reange 6350-7500 Å)  > 40 slits per CCD, i.e up to 170 per exposure  ~ 900 spectra with MR grism  spectral classification ~ 550 spectra with HR_red grism  study of PMS stars (if any!) Preliminary data reduction with ESO VIMOS pipeline (but no defringing, bad sky subtraction for HR and strange features in Q3 for MR) 100% MR spectra extracted 50% HR spectra extracted

Results: the HR diagram

Results: spectra

Results: spectra

Results: spectra

Results: spectra

Conclusions and future actions Dolidze 25 show a rich population of H emission young stars A few objects are PMS intermediate mass candidates. Four stars fall within the instability strip for PMS  Scuti pulsation faint objects: but for R~16.5 mag we should be able to do asteroseismology for PMS  Scuti candidates no problem to study mid/long term variations (UX Ori like) Several bright KM stars with (and without) H emission In the future we plan to: reduce better the data + calibration in flux obtain spectral classification for all the stars study membership (UCAC2) time series photometry for interesting objects – not easy, faint objects Preparation of proposal in the AP context asking for a few windows in the EXO field. PMS collaboration Open to everybody: if you are interested please contact me: ripepi@na.astro.it