Young open cluster in the vicinity of COROT primary targets: the case of Collinder 96 and Dolidze 25 Vincenzo Ripepi INAF-Osservatorio Astronomico di Capodimonte, Naples, Italy Collaborators: J.M. Alcalá, F.Cusano, M. Marconi (INAF-OAC) LOI partecipants EXOdat team

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. HD43587 HD52265 HD49933-HD49434 HD HD HD HD HD49434

Collinder 96  Young cluster (age~10 Myrs); only 12 stars observed by Moffat & Vogt (1975)  No association with SFR or OB  Unfortunately no info on membership.   New observations carried out during winter 2004 with the 1.5m Loiano telescope (Italy).  UBVR-H  filters for a FOV of ~ 14’x13’.  Data reduction performed with DAOPHOTII/ALLFRAME (Stetson, 1987, 1993).

Isochrones by Girardi et al CMD for Collinder 96 Preliminary Conclusions:  Collinder 96 is probably not as young as found in previous works (Age ~ 60 Myrs)  Quite large uncertaintis due to the lack of membership information  improvements are expected by the study of new proper motion measurement (UCAC2)  Echelle spectra for brightest stars scheduled (Loiano).

Dolidze 25: what we know up to now  Dolidze 25 is associated with the HII region S284  it should be young (< 10 Myrs, Turbide & Moffat, 1993)  it is far (heliocentric distance > 5.5 Kpc)  Only UBV photometry in the literature for the brighest stars (Moffat & Vogt, 1975) + slighly deeper UBV CMD on a small region (Turbide & Moffat, 1993).  Spectral classification for some 30 stars (Babu, 1983), but not very precise.  Lennon et al on the basis of high resolution spectroscopy for three OB stars, have found that Dolidze 25 is deficient in metals approximately by a factor 6 (i.e. Z Dolidze25  0.003, similar to SMC)  somewhat in disagreement with respect to the expected abundance gradient of the disc.

Additional motivations for Dolidze 25  Martin et al claimed the discovery of a dwarf galaxy remnant in Canis Major: the fossil of an in-plane accretion on to the Milky Way. Dolidze 25 position correspond to the one of the Canis Major object  “Dolidze 25 …. could be the consequence of the strong perturbation of the disc by the accreted dwarf Galaxy and the resulting star formation activity in the disc.”  a detailed study of this cluster could allow us to verify this statement  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 (hopefully) intermediate mass PMS.  Dolidze 25 has a good probability to fall in the EXO field of COROT  characterization of stars of the cluster (spectra!) needed  proposal to obtain EXO planet windows to study interesting candidates.  Spectral classification (using spectra) for a relevant number of stars  important to check the photometric classification by EXO planet team (see Magali’s talk).

Efforts to study Dolidze 25  UBVR-H  imaging (  20’x20’ FOV) on the north-east of the cluster (Loiano, 1.5m telescope). Data not fully reduced and not presented here.  VIMOS proposal in collaboration with J.M. Alcalá (Naples): multiobject spectroscopy on two pointings centered on Dolidze 25: ACCEPTED!  How to select targets for spectroscopy?  Literature not sufficient (few IRAS, ROSAT sources…)  Need for a reliable HR diagram on a wide area.  VIMOS pre-imaging in R and I + EXO planet preparatory program photometry (FUNDAMENTAL!)

18’x17’ Membership by Dias, Lèpine, Alessi (2002)

 Preliminary data reduction of VIMOS pre-imaging data using Sextractor (Bertin, 1999)  Cross-correlation with EXOdat observations  photometric calibration and marging of the catalogues (VLT data deeper, but saturation problems below I=13) Data reduction

CMDs from EXOdat

 We know from the literature the approximate distance and reddening  From Lennon et al. (1990) we know logTe and logg for three bright stars.  We can use all these info to constrain the age of the cluster by using the isochrones (Padua group: Girardi et al. 2000). Hints on PMS star position in HRD by using the Siess et al. (2000) tracks and Isochrones (6 Myr). Cluster parameters 20 Mo 0.8 Mo 3 Mo 6 Mo

Cignoni & Degl’Innocenti, Private Comm. Target selection (R-I) I

VIMOS multiobject spectroscopy Two different grisms:  Medium Resolution: 2 Å/pixel (spectral reange Å)  up to 50 slits per CCD, i.e up to 200 per exposure  High Resolution Red: 0.6 Å/pixel (spectral reange 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!)

Conclusions  A few open clusters will probably fall in the EXO field of COROT.  Collinder 96 and Dolidze 25 were selected to be studied on the basis of the their supposed young age and low crowding.  Collinder 96 probably not very young; near a low priority primary target.  Dolidze 25 is a very interesting object under many point of views.  Our data confirms that Dolidze 25 is young age ~ 4-10 Myrs  Multiobject spectroscopy with scheduled  results (hopefully) at CW9 (spring 2005).