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

HD171834

HD170580

HD177552

HD181555

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. 2000

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. 1990 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. ZDolidze25 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. 2004 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 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!)

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 VIMOS@VLT scheduled results (hopefully) at CW9 (spring 2005).