A study of young stellar objects in the γ 2 Vel and Cha I clusters * Antonio Frasca. K. Biazzo, J.M. Alcalá, B. Stelzer, S. Bonito

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1 A study of young stellar objects in the γ 2 Vel and Cha I clusters * Antonio Frasca INAF - Osservatorio Astrofisico di Catania (OACt) JEDI People involved in this work: K. Biazzo, J.M. Alcalá, B. Stelzer, S. Bonito * Frasca, A., Biazzo, K., Lanzafame, A.C., et al. 2015, A&A 575, A4 07/04/15 2nd JEDI progress meexng - Napoli 1

2 The Gaia- ESO Survey h[p:// eso.eu/ Spectrum Extrac<on Pipelines WG7: GIRAFFE ReducXon (CASU, Keele); UVES ReducXon (Arcetri) WG8: Radial VelociXes (Cambridge, Keele, Arcetri, Antwerp, ZAH) WG9: Discrete ClassificaXon Spectrum Analyses WG10: FGK Stars: GIRAFFE (HR10+HR21 for MW; HR15N for OCs 3 nodes) WG11: FGK Stars: UVES ( ~ 11 nodes) WG12: Pre- Main- Sequence stars: UVES ( ) + GIRAFFE (HR15N) 07/04/15 2nd JEDI progress meexng - Napoli 2

3 The Gaia- ESO Survey h[p:// eso.eu/ WG 12 Products Atmospheric parameters (T eff, logg, [Fe/H], ξ) (4 nodes for UVES; 2 for GIRAFFE) Other parameters (Sp.Type, vsini) (1 node: OACt) Lithium EW and abundance (4 nodes for UVES; 3 for GIRAFFE). Accretion parameters (EW Hα ; 10%W Hα ; M acc ; veil) (1-4 nodes) Chromospheric parameters (EW chr Hα ; EWchr Hβ ; F Hα ; F Hβ ) (1 node: OACt) Element abundance (from UVES spectra only) (3 nodes) 07/04/15 2nd JEDI progress meexng - Napoli 3

4 Atmospheric Parameters and vsini: ROTFIT IDL code originally designed for measuring vsini and get an MK classification (e.g., Frasca et al. 2006, A&A 454, 301); Fully automatic determination of T eff, logg, [Fe/H], and vsini by the comparison with template spectra (χ 2 minimization); The UVES spectra are split in 100Å-wide segments independently analysed; Minimum of residuals (or χ 2 ) is found and the templates are sorted according to it; For each spectral segment, the best 10 templates are taken à weighted averages of the parameters and standard errors The weight includes the amount of information contained in each segment, which is quantified by the total line absorption. For Giraffe spectra all the spectral range, eventually masking Hα & LiI 07/04/15 2nd JEDI progress meexng - Napoli 4

5 Atmospheric Parameters and vsini: UVES Templates: ELODIE Archive spectra of slowlyrotating stars with APs redetermined according to the GES prescriptions. vsini is determined in a quite robust way. It is nearly independent on the template within more than 4 subclasses. K1V member of γ 2 Vel EW Li = Å The MK type of the best template is normally the same in all the spectral segments within 1 subclass. Best template 07/04/15 2nd JEDI progress meexng - Napoli 5

6 Atmospheric Parameters and vsini: UVES Templates: ELODIE Archive spectra of slowlyrotating stars with APs redetermined according to the GES prescriptions. vsini is determined in a quite robust way. It is nearly independent on the template within more than 4 subclasses. The MK type of the best template is normally the same in all the spectral segments within 1 subclass. Best template 08/04/15 2nd JEDI progress meexng - Napoli 6

7 Atmospheric Parameters and vsini: UVES Templates: ELODIE Archive spectra of slowlyrotating stars with APs redetermined according to the GES prescriptions. vsini is determined in a quite robust way. It is nearly independent on the template within more than 4 subclasses. <vsini> = 31.3 ± 0.6 km/s The MK type of the best template is normally the same in all the spectral segments within 1 subclass. Best template 08/04/15 2nd JEDI progress meexng - Napoli 7

8 Atmospheric Parameters and vsini: GIRAFFE The same star observed with Giraffe Very Good Agreement with the UVES results! <vsini> = 32.3 ± 1.5 km/s Best template 07/04/15 2nd JEDI progress meexng - Napoli 8

9 AccreXon diagnosxcs EW Hα and 10%W Hα for two members of Cha I log M acc =! "10 3 #10%W H! Natta et al. (2004, A&A 424, 603) 07/04/15 2nd JEDI progress meexng - Napoli 9

10 AccreXon diagnosxcs EW Hα and 10%W Hα for two members of Cha I L Hα à L acc Alcalà et al. (2014) EW M acc " = 1! R * $ # R in % ' &!1 Lacc R * GM * R in =5R * Hartmann (1998) 10/04/15 2nd JEDI progress meexng - Napoli 10

11 Veiling For accretor candidates (10%W Hα 270 km/s) we run ROTFIT with another free parameter: the veil (r) in conxnuum units. AssumpXon: veil constant over a limited wavelength range (100 Å for UVES, 300 Å for GIRAFFE). Templates progressively arxficially veiled F! veil F C = F! F C + veil 1+ veil 07/04/15 2nd JEDI progress meexng - Napoli 11

12 Veiling AccreXng K8 star in Cha I. T eff = 4130 K vsini = 9 km/s UVES spectrum 07/04/15 2nd JEDI progress meexng - Napoli 12

13 Chromospheric AcXvity: spectral subtracxon The MARCS synthexc spectrum fails to reproduce the photospheric line profile in absence of chromosphere. Difference ATLAS9+Synthe spectrum EW chr Hα MARCS spectrum Low- acxvity star K1V acxve star member of Υ 2 Vel. The Hα line is totally filled in by emission Removal of photospheric profile à SubtracXon of a non- acxve template : a spectrum of a low- acxvity standard star degraded to the Giraffe resoluxon, rotaxonally broadened and Doppler- shi{ed. 07/04/15 2nd JEDI progress meexng - Napoli 13

14 Chromospheric AcXvity: EW Hα, F Hα, L Hα /L bol F Hα = F cont * EW Hα L Hα /L bol = F Hα /(σt eff4 ) Largest EW Hα for cooler stars. Contrast effect: Hα emission stands out against a low conxnuum. When converted into flux, the nearly exponenxal behaviour with T eff disappears. 07/04/15 14

15 Chamaeleon I GES observation in ChaI superimposed to an extinction map of Cambresy (1998). Age ~ 2 Myr (e.g., Luhman 2008) GIRAFFE (647 targets) UVES (48 targets) Luhman- 08 members From Spina et al. (2014) 08/04/15 2nd JEDI progress meexng - Napoli 15

16 Gamma Velorum Vela OB2 associaxon Cluster of stars around the massive binary γ2 Vel (~ 5 Myr) in Vela OB2 association. de Zeeuw et al. (1999)!"#$%&'($ γ2 Vel 2 4,5-,,6$6/789$/:!%$;,+/-7.<$ 4=68*>?,$@$A&1B'(1$C?$ *5,$@$A&$DE-$:-/.$FGH$IJ+=K,=-*$,8$ *+L$%11AM$ First cluster observed by the GES: 18 NK=4,>?,$/:$.*66$6,5-,5*O/>$ fields;ip,q-=,6$,8$*+l$%11'm$ 1242 targets; ~ 1deg covered. Distance 350 pc Age = 5-10 Myr Pe[ersson 2008 (5-10 Myr) (35 Myr) (Pozzo et al. 2000, Jeffries et al. 2009) 08/04/15 2nd JEDI progress meexng - Napoli I:-/.$),V,-66/>$%11WM$ 16

17 γ 2 Vel - Member selecxon Pre-selection of candidate members to the Υ 2 Vel cluster based on the lithium 6708 Å line (Jeffries et al. 2014) IC 2391/2602 envelope Baraffe 10, 20 Myr Pop A EW(Li) (ma) Pop B V-I The final members (hatched area) are selected among the candidates from their radial velocity: 8 RV 26 km/s. A contamination by non-members is still possible: Li-rich giants, active field stars, unresolved close binaries, 08/04/15 2nd JEDI progress meexng - Napoli 17

18 Results: vsini distribuxon for γ 2 Vel The two kinemaxc subsamples, idenxfied by Jeffries et al. (2014), have slightly different vsini distribuxons, with a higher frequency of faster rotators for Pop B. 07/04/15 2nd JEDI progress meexng - Napoli 18

19 Results: Chromospheric AcXvity vs. AccreXon Accr ~ 40 % SaturaXon limit (Barrado & MarXn 2003) Dividing line accrexon/chrom. (Present work) Accr ~ 4 % logf Hα = (T eff 3000) 2 Myr F Hα Accretor candidates (W 10% > 270 km/s) occupy a different region from chromospherically acxve stars. 10 Myr Less (or no) accretor candidates at older ages. Fluxes and luminosixes progressively lower than the limit, especially for T eff > K 35 Myr 08/04/15 2nd JEDI progress meexng - Napoli 19

20 Results: Chromospheric AcXvity vs. AccreXon Accr ~ 40 % SaturaXon limit R Hα =- 3.2 (Barrado & MarXn 2003) Dividing line accrexon/chrom. (Present work) Accr ~ 4 % logr Hα = (T eff 3000) 2 Myr R Hα = L Hα /L bol Accretor candidates (W 10% > 270 km/s) occupy a different region from chromospherically acxve stars. 10 Myr Less (or no) accretor candidates at older ages. Fluxes and luminosixes progressively lower than the limit, especially for T eff > K 35 Myr 08/04/15 2nd JEDI progress meexng - Napoli 20

21 Results: Mass AccreXon from 10%W Hα and EW Hα 10%W Hα EW Hα γ 2 Vel Cha I 2M bin ChaI Possible accr. M acc! M 2 Chrom. noise boundaries (Manara et al. 2013) 08/04/15 2nd JEDI progress meexng - Napoli 21

22 Chromospheric AcXvity: Balmer Decrement 08/04/15 2nd JEDI progress meexng - Napoli 22

23 08/04/15 Summary GES spectra with S/N>20 in young OCs form staxsxcally significant samples for the analysis of vsini, chrom. acxvity, accrexon, etc.; Asymmetric distribuxon of vsini for γ 2 Vel with a possible disxncxon between two kinemaxcal subsamples; Till to ~30 Myr all the stars cooler than about 4500 K are near the saturaxon of acxvity (no or weak dependence on vsini); Ho[er stars display a flux F Hα and a R Hα decreasing with the increasing T eff ; Balmer decrements (G- K type stars) intermediate between opxcally thick plage- like and thin prominence- like regions; Low fracxon (~2-4%) of accretors for γ 2 Vel vs. a high fracxon (~35-42%) for Cha I (age effect); AccreXng and acxve stars occupy different regions in T eff - F Hα plane; 10%W Hα can be used for selecxng accrexng candidates but must be complemented with other diagnosxcs. 23

24 PerspecXves idr4 Young Open Clusters Rho Oph 1 Myr Cha I 2 Myr NGC Myr Trumpler 14 6 Myr NGC Myr γ 2 Vel 10 Myr IC Myr NGC Myr IC Myr IC Myr NGC Myr 09/04/15 2nd JEDI progress meexng - Napoli 24

25 Thanks for your a[enxon 07/04/15 2nd JEDI progress meexng - Napoli 25