VEGA/CHARA: Status and First ScienceSPIE 2010 San Diego

M. Tallon, D. MourardThe VEGA and CHARA Teams

High Angular (0.3mas) and up to 30000 spectral resolution

Mode 3THD3360- 10-08 Differential measurements

Fundamental parametersJune 27th 2010 2VEGA SPIE San Diego

Old GI2T Facility

CHARA Array

09-2007: Integration07-2008: First observations07-2009: Remote operation06-2010: First science papers

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Summary of performances (Mourard et al, A&A 508 2009)

Spectrograph Characteristics

Instrumental visibility

Limiting magnitude

Polarisation behaviour

Differential phase

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R0=8cm R0=15cmV²Cal≈2%

≈1-2°

Recent advances

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1. Routine remote operations thanks to the CHARA staff

2. Blind recording with IR tracking (CLIMB, new IR CHARA instrument)

3. Simultaneous observations between visible VEGA and IR FLUOR

4. End of night automated pipeline for quality check

5. Off line data analysis compatible with the OI-FITS norm.

6. Standard use of the JMMC web-service like LITPro (model fitting)

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Summary of the VEGA Science Programs

• First science papers – AB Aur: Perraut et al, A&A 516, L1 (2010)– A/B Supergiants: Chesneau et al, A&A in press (2010)

• Circumstellar environments– Kinematics study in the circumstellar environment of Be stars (Delaa et al.)– Interactive massive stars: ups Sgr (Chesneau et al.) and bet Lyr (Bonneau et

al.)

• Fundamental parameters– 13 Cyg (exoplanet host star)– bet Cep (extended environnement and companion)– ro Ap stars (angular diameter and Teff)– sub giants radii and orbits (class IV stars)

• But also: eps Aur (famous eclipsing system), alp Cep (rotation), P Cyg (stellar wind), theta OriC (Hline forming region)…

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AB Aur is a prototype of Herbig Ae/Be stars and, as such, it has been fully observed in spectroscopy, in infrared interferometry (PTI, IOTA, …)– Spectral type : A0– Magnitudes : V = 7.1 / K = 4.4– Distance : 144 pc– Luminosity : 47 L

– Large infrared excess– No jets, no CO flow– Variability of the H emission at a scale of a few hours

Stellar activity, link wind and disc, …

Fukagawa, 2004. Subaru

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VEGA observations

• 2008. S1S2: Clear spatial resolution of AB Aur in H

• 2008. W1W2: Fringes but SNR too poor

• 2009. S1S2: Tracking problem 0

0,2

0,4

0,6

0,8

1

1,2

610 620 630 640 650 660 670 680 690 700

Wavelength (nm)

Cal

ibra

ted v

isib

ilit

y s

quar

ed

0

0,5

1

1,5

2

2,5

640 645 650 655 660 665 670

Wavelength (nm)

Cal

ibra

ted fl

ux

PCygni profileWind modelling

V²

H

1

X-WindD-Wind

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Interpretation

Additional component

• A wind only does not allow us to reproduce the spectrum AND the visibility curve, even if this wind is very extended. Another component has to be considered. We assume a brightness

assymetry in agreement with : - the spiral arms detected at few hundreds of AU- the non-null closure phase measured by Millan-Gabet et al. (2006)- the binarity signals recorded by spectro-astrometry by Baines et al. (2006)

7% of flux @ ~40mas (5.5 AU)

Perspectives:- Observe AB Aur in 2010 with larger baselines to resolve its photosphere- Take benefit of IR fringe tracking

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Interpretation

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Interests in the visible of A/B supergiants (e.g. Deneb A2Ia, and Rigel B8Ia):- Very bright and used as stellar candles,- large diameters (60-100 solar radii), Deneb and Rigel are 2-3mas sources- Variability in H line (R>10000), sensitive to mass-loss and its perturbation, time scale weeks to months.

Rigel, Kaufer et al. 1997, PhD thesis Deneb, Przybilla et al. 2008

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VEGA/CHARA observations of Deneb: the H line

V

I

Time variability

I

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Spatial variability

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Full 1D modeling of the wind of Deneb

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Parameters from the model of Schiller et al. 2008Conclusions:• The H line is complex with subtle opacity effects,• The visibility curve is a sensitive indicator of mass-loss rate. The current modeling succeeds in fitting the data by changing the mass-loss rate. • The differential phase signals clearly indicates asymmetries in the wind, changing with time. Progresses in the modeling are necessary.

Synthetic spectra for different mass-loss rates

V

I

I

Fundamental stellar parametersWorks in progress

•Angular diameters: 13 Cyg : F4V (Exoplanets) Equ : A9p (roAp)• Massβ Cep : B2IIIev (pulsating binary)48 And : F5IVe (sub-giants)• Rotation α Cep : A7IV (fast rotator)Be stars envelopes

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VEGA/CHARA high angular resolutionallows the study of main sequence stars

Measurements of angular diameters

1%

2%

4000 stars brighter than mV=6.5 that can be detected by VEGA with accuracy better than 2% constraints on models (Creevey et al. 2007, Kervella et al. 2008)

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Visible 3T observations and infrared FT

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Cal: <0.4 Target:<1.0

O 4 12

B 35 112

A 7 176

F 243

G 481

K 501

M

Cal: <0.4 Target:<1.0

O 7 15

B 108 197

A 88 321

F 4 487

G 559

K 504

M 2

mK<4.5

mK<5.0

Conclusions• VEGA/CHARA is now operational in routine and remote in 2T mode:

– medium and high spectral resolution for circumstellar at atmosphere/chromosphere studies– Medium and low spectral resolution for fundamental stellar parameters– Mourard et al. A&A 2009, Perraut et al. A&A 2010, Chesneau et al. A&A 2010 (accepted)

• Development of the 3T mode external fringe tracker.

• Publications submitted or in preparation: Nardetto et al. A&A (environnement of beta Cephei) Delaa et al. A&A (kinematics of Be stars) Chesneau et al. A&A (environnement of ups Sgr) Bonneau et al. A&A (environnement of beta Lyrae) Perraut et al. A&A (ro Ap diameter and Teff determination) Bério et al. A&A (chromospheres of K giant stars) Mourard et al. (HinAur) Mourard et al. (characterization of exoplanets host stars)

Thanks a lot to CHARA and VEGA colleagues!More detailed informations on http://www-g.oca.eu/gemini/projets/vega/en/present/

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