GAIA/VLTI - 25 Janvier 2010 Surface Brightness Asymmetries of LPV stars probed by NIR-Interferometric measurements Prospects for the correction on the

GAIA/VLTI - 25 Janvier 2010

Surface Brightness Asymmetries of LPV stars probed by NIR-Interferometric measurements

Prospects for the correction on the GAIA parallax

S. Sacuto, Vienna Institute of Astronomy

A. Jorissen P. Cruzalèbes, E. Pasquato, A. Chiavassa, A. Spang, O. Chesneau & Y. Rabbia


VLTI-AMBER observations

Observing date (2009)

Object Spectral Type v (mas) Diam (mas)

charm / cadar

May & August d Oph M0.5III 19.2 10

May & August a Tra K5Ib/K3IIa 8.0 9

May & August z Ara K3III 5.7 11

May & August TW Oph CII 3.6 10

November TX Psc CII 4.3 10

November R Scl CII 2.1 10

November T Cet M5IIe 4.2 13

November a Car F0II 10.4 6

November o1 CMa K2.5Iab 1.6 9

November L2 Pup M5II 16.5 13

November W Ori CII 4.7 10

November 119 Tau M2Iab 1.7 10

(Proposals P83 and P84: Mid-resolution / l0=2.3µm)


Objects

+

Time

119 Tau

6:30

Alp Car

8:32

Alp Tra

3:54

Del Oph

6:28

L2 Pup

7:06

Omi1

CmA

5:39

R Scl

2:02

T Cet

1:13

Tw Oph

10:02

Tx Psc

2:50

W Ori

7:59

Zet Ara

8:27

Base

+

Bpmax

D0-H0-K0

90.4 m

D0-H0-K0

92.8 m

A0-DO-H0

95.3 m

A0-DO-H0

91.0 m

D0-H0-K0

95.0m

D0-H0-K0

81.8 m

D0-H0-K0

95.3 m

D0-H0-K0

94.9 m

A0-D0-H0

54.9 m

D0-H0-K0

92.7 m

D0-H0-K0

93.7 m

A0-D0-H0

79.0 m

Seeing

+

Airmass

0.64

1.39

0.74

1.14

0.70

1.44

0.46

1.18

0.99

1.13

1.13

1.25

0.51

1.03

0.54

1.01

0.73

1.75

0.82

1.24

0.70

1.19

0.53

1.40

Finito ON ON ON ON OFF ON ON ON ON ON ON ON

Total number of cal.

in the night

15 4 3 4 3 11 12 6 3 12 15 4

Cal.

used

+

Time

5

5:46

to 7:43

3

2:47

to 8:15

3

2:50

to 4:15

3

5:19

to 7:17

3

6:09

to 7:21

3

1:47

to 2:37

4

1:47

to 3:06

3

0:11

to 01:31

3

8:52

to 10:22

4

1:47

to 3:06

3

6:46

to 7:43

4

5:19

to 8:04

comments

No. Last calib. (8:47) lead to div.

No. No. No. Strong div. for some calib.

+

first lobe

No. No. First lobe

No. No. No.

Err. Visi

2nd lobe

Err. CP

0.3%

1°

0.1%

10°

0.2%

2°

0.01%

<1°

0.1%

peculiar case

1°

first lobe (1%)

1°

0.5%

1°

0.1%

peculiar case

1°

first lobe (5%)

2°

0.2%

1°

0.1%

1°

0.01%

1°

Observation and calibration process


Calibrated Squared Visibility


Calibrated Cloture Phases


Categories

1. Clear evidence of SBA (119 Tau / Alp Tra / Tx Psc)

2. Evidence of SBA (Del Oph / R Scl / W Ori)

3. Poor evidence of SBA (Alp Car / Zet Ara*)

4. First lobe* (Omi1 Cma / TW Oph)

5. Peculiar cases (L2 Pup / T Cet)

* : Use of larger baselines


1. Clear evidence of SBA (119 Tau / Alp Tra / Tx Psc)


119 Tau 119 Tau

TX Psc TX Psc


2. Evidence of SBA (Del Oph / R Scl / W Ori)


Del Oph


3. Poor evidence of SBA (Alp Car / Zet Ara)

A0-H0(p)=79m

A0-K0=128m


4. First lobe (Omi1 Cma / TW Oph)

Circumstellarenvironment?

A0-K0=128m

D0-K0(p)=81m A0-H0(p)=55m

A0-K0=128m


5. Peculiar cases (L2 Pup / T Cet)


Uniform disk

L2 Pup

UD=35mas

Binary (Hipparcos)

base

line

Prim.=40mas

Comp.=4mas

Sep=27.5mas

Fc/Fp=2.8%

~3 times larger than the 13 mas catalog value !


Summary and conclusion

12 Objects (5 categories):

Objects Morphology

119 Tau

Alp Tra

Tx Psc

Clear evidence of SBA

(CP very different from 0±180° / smooth slope 0->180°)

Del Oph

R Scl

W Ori

Evidence of SBA

(CP¹0±180° / smooth vertical jump 0->180°)

Alp Car Zet Ara

Poor evidence of SBA

(CP~0±180° / clear vertical jump 0->180°)

o1 Cma

TW Oph

Visibility in the first lobe (possible CE for o1 Cma!)

(Use of larger baseline: A0-K0=128m)

L2 Pup

T Cet

Peculiar cases (L2 Pup is 3 times larger than predicted!)

(modulation in the visibility profile: possible binarity)

The P86 proposal (recently submited) uses the triplet D0-G1-H0 and will constraint this result

D0

H0

G1


GBOG Nice, 18 Novembre 2009


Deviation from the UD model in the 2nd lobe

Presence of asymmetries in the second lobe

The example of the M0.5III Giant: d Oph (Teff = 3679 K; log g = 1.4)

Closure phase:

Interferometric measurements of d Oph reveal asymmetric structures on its photosphere.

As the signature of these asymmetries appears in the second lobe of visibility, it means that structures of 10 to 30% (1-3 mas) size of the star are detected.

Therefore, the size of the spots is about 10 times larger than the one predicted from the simulations of Svensson et al., 2005.

This means that SBA could affect the astrometry of LPVs located closer than 300 pc at the level of accuracy of GAIA (~10 µas).

We can thus re-evaluate the number of possible threats to the parallax to maybe half of the LPVs observable with GAIA.

2.3µm

Visibility:

Uniform Diskof 10 mas

Measurements

2.3µm1st lobe

2nd lobe

Documents

GAIA/VLTI - 25 Janvier 2010 Surface Brightness Asymmetries of LPV stars probed by NIR-Interferometric measurements Prospects for the correction on the