About the angular diameter of red supergiant stars

Transcription

1 Mass loss of evolved stars Betlegeuse/PIONIER Antares/PIONIER CE Tau/PIONIER Conclusion About the angular diameter of red supergiant stars Miguel Montargès (IRAM) VLTI Community Days ESO Garching - March 9th 17 Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 1/15

2 Stellar evolution Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 2/15

3 Trigerring the RSG mass loss Physical process remains unknown (no flares, no large pulsations) Josselin & Plez (07) suggested a convection triggered mass loss Auriere et al. () observed magnetic field 1 G + Airapetian et al. (00): model Alfvén-wave triggered outflow Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 3/15

4 Trigerring the RSG mass loss Physical process remains unknown (no flares, no large pulsations) Josselin & Plez (07) suggested a convection triggered mass loss Auriere et al. () observed magnetic field 1 G + Airapetian et al. (00): model Alfvén-wave triggered outflow Study of the photosphere + CSE Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 3/15

5 Spatial scales (P. Kervella) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 4/15

6 Mass loss of evolved stars Betlegeuse/PIONIER Antares/PIONIER CE Tau/PIONIER Conclusion PIONIER monitoring of Betelgeuse (α Ori) VLTI/PIONIER observations (4 telescopes, H band, low spectral resolution, R = 40) 4 epochs of monitoring: Jan. 12, Feb. 13, Jan. 14 and Nov. 14 Only the compact array configuration (baseline length [11; 36 m]) Montargès et al. (16), A&A, 588, A130 Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 5/15

7 Shape of the visibilities (13) v (m) 0 Squared visibility u (m) Spatial frequency (arcsec 1 ) Consistent between the 4 epochs (3 different features to avoid detector saturation) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 6/15

8 Shape of the visibilities (13) 25 0 (N) 90 (E) (W) Limb-darkened disk fit: vs mas % difference! 180 (S) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 7/15

9 Shape of the visibilities (13) 25 0 (N) 90 (E) (W) Limb-darkened disk fit: vs mas % difference! AND litterature value 42 mas 180 (S) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 7/15

10 Shape of the closure phase (13) Closure phase (degree) Maximum spatial frequency (arcsec 1 ) Strong signal Incompatible with elliptical model Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 8/15

11 LDD model + gaussian hotspot Chiavassa et al. (09, ) showed that convection can displace the nulls of the visibility function (as a function of P. A.) Difficulty: angular diameter cannot be inferred from the first null anymore Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 9/15

12 LDD model + gaussian hotspot Chiavassa et al. (09, ) showed that convection can displace the nulls of the visibility function (as a function of P. A.) Difficulty: angular diameter cannot be inferred from the first null anymore Good agreement + angular diameter consistent with literature 43 mas) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 9/15

13 LDD model + gaussian hotspot Consistent on the 4 epochs Photocenter displacement up to 2 mas (π 6 mas) Spots already observed on Betelgeuse (see Haubois et al. 09, Ravi et al. 11, Ohnaka et al. 11) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 9/15

14 LDD model + gaussian hotspot Consistent on the 4 epochs Photocenter displacement up to 2 mas (π 6 mas) Spots already observed on Betelgeuse (see Haubois et al. 09, Ravi et al. 11, Ohnaka et al. 11) Consistent with spectro-polarimetric observations at TBL/NARVAL (Aurière et al. 16) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 9/15

15 VLTI/PIONIER observations (4 telescopes, H band, low spectral resolution, R = 40) 3 different configurations (baseline lengths : m) Montargès et al. subm., A&A V (m) Visibility U (m) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars /15

16 dataset 0 Data 1 2 Squared visibility Spatial frequency (arcsec 1 ) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 11/15

17 1st and 2nd lobe Squared visibility Spatial frequency (arcsec 1 ) Position angle ( ) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 12/15

18 1st and 2nd lobe 0 (N) 90 (E) (W) LDD diameters (at 1.61 µm): mas 4% difference AND does not fit the closure phases! 180 (S) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 12/15

19 modeling Weak signal compared to Betelgeuse small spots? Angular resolution 1/16th of the stellar diameter! Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 13/15

20 modeling Weak signal compared to Betelgeuse small spots? Angular resolution 1/16th of the stellar diameter! Modeling using random distribution of spots with a fixed size! Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 13/15

21 modeling Weak signal compared to Betelgeuse small spots? Angular resolution 1/16th of the stellar diameter! Modeling using random distribution of spots with a fixed size! Best match: Gaussian spot distributions with a FWHM of 17 and 2 mas (not resolved!) LDD diameter: ± 0. mas at 1.61 µm χ 2 (V 2 + CP) as low as 28 (627 for best LDD alone) Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 13/15

22 On going DDT program on CE Tau with PIONIER V (m) PA (deg) Squared visibility U (m) Spatial frequency (arcsec 1 ) At 1.62 µm: θ LDD =.07 ± 0.05 mas χ 2 =.89 Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 14/15

23 Conclusions v (m) 0 Squared visibility u (m) Spatial frequency (arcsec 1 ) What would we have concluded with only the red (48.56 mas) or blue (44.21 mas) baselines? Miguel Montargès (IRAM) About the angular diameter of red supergiant stars 15/15