Probing Sgr A* flares with VLTI/GRAVITY

Transcription

1 Probing Sgr A* flares with VLTI/GRAVITY Frédéric Vincent 1 T. Paumard, G. Perrin, P. Varniere, F. Casse, F. Eisenhauer, S. Gillessen, P. Armitage 1 Centrum Astronomiczne M. Kopernika, Warsaw, Poland 1/26 Frédéric Vincent GRAVITY and SgrA* flares

2 1 The source: Sgr A* 2 The instruments: GRAVITY, EHT 3 Constraining Sgr A* flare models with GRAVITY 2/26 Frédéric Vincent GRAVITY and SgrA* flares

3 Baganoff+03: size = 1 2 pc Credit : Stellarium, Bob King 3/26 Frédéric Vincent GRAVITY and SgrA* flares

4 Genzel+10: size = 10" 0.5 pc 4/26 Frédéric Vincent GRAVITY and SgrA* flares

5 0.4 S27 S12 S31 S19 S S6 S5 S14 S4 S17 S2 Dec " 0. S38 S S8 S1 S13 S S9 S24 S R.A. " S-stars cluster (Gillessen+09): size = pc The central dark mass Astrometric measurements of close stars central mass. Sgr A* SMBH of M, θ app,sch 50 µas 5/26 Frédéric Vincent GRAVITY and SgrA* flares

6 40 20 y (µas) 0 20 Silhouette x (µas) Sgr A* flare : light curve (Hamaus+09) Sgr A* silhouette Probing the vicinity of the horizon Variability: flares (period 30 minutes) - cause?? Imaging: silhouette - GR probe 6/26 Frédéric Vincent GRAVITY and SgrA* flares

7 1 The source: Sgr A* 2 The instruments: GRAVITY, EHT 3 Constraining Sgr A* flare models with GRAVITY 7/26 Frédéric Vincent GRAVITY and SgrA* flares

8 GRAVITY VLT 4 main telescopes will be combined by GRAVITY in infrared First light end of 2015! 8/26 Frédéric Vincent GRAVITY and SgrA* flares

9 GRAVITY s astrometric performance Astrometric precision: 10 µas Integration time needed: a few minutes So what? Follow the motion of a source very close to Sgr A* Can GRAVITY help understand what Sgr A* flares are? 9/26 Frédéric Vincent GRAVITY and SgrA* flares

10 Event Horizon Telescope ( ) Quiescent state imaging Sub-mm VLBI network 10 stations worldwide (including ALMA) Imaging resolution 15 µas Testing strong-field general relativity Complementary with GRAVITY 10/26 Frédéric Vincent GRAVITY and SgrA* flares

11 a=0,i=45 a=0, i= e-3. 2e e e-4. 1e 04 y (µas) 0 y (µas) e e-4. 6e e e-4 1.2e x (µas) x (µas) Vincent, Yan, Straub, Zdziarski, Abramowicz, A&A, 574, 48 (2015) EHT constraints Imaging the vicinity of Sgr A* Constraining the black hole properties? 11/26 Frédéric Vincent GRAVITY and SgrA* flares

12 1 The source: Sgr A* 2 The instruments: GRAVITY, EHT 3 Constraining Sgr A* flare models with GRAVITY 12/26 Frédéric Vincent GRAVITY and SgrA* flares

13 GRAVITY observation simulation Using GYOTO to ray-trace light curves Using GRAVISIM to simulate GRAVITY data 13/26 Frédéric Vincent GRAVITY and SgrA* flares

14 Ray-tracing: GYOTO Integrates light rays to distant observer Radiative transfer inside the source Open-source: gyoto.obspm.fr 14/26 Frédéric Vincent GRAVITY and SgrA* flares

15 Date (x th,y th,i th ) V obs (u,v) = V th (u,v)+noise Fitting on (x ret,y ret,i ret ) point-source Instrument simulator Noise: σ V, σ φ Generating astrometry: GRAVISIM 15/26 Frédéric Vincent GRAVITY and SgrA* flares

16 Astrometric precision with a single source in the field PSF Astrometric error (µas) Errors in the direction of the major and minor axes of the PSF mk GRAVITY has access to Schwarzschild radius scale astrometry Vincent et al MNRAS /26 Frédéric Vincent GRAVITY and SgrA* flares

17 Hot spot Hot spot [Genzel et al., 2003] Rossby wave [Tagger & Melia, 2006; Falanga et al., 2007] Weather forecasting Red noise [Do et al., 2009] Ejection Plasmon [Van der Laan, 1966; Yusef-Zadeh et al., 2006] Jet [Falcke & Markoff, 2000; Markoff et al., 2001] 17/26 Frédéric Vincent GRAVITY and SgrA* flares

18 Three astrometric classes of models Hot-spot like, equatorial plane Weather forecasting, equatorial plane Ejection, out of the equatorial plane Question Can GRAVITY distinguish these classes? 18/26 Frédéric Vincent GRAVITY and SgrA* flares

19 Three models Rossby wave: hydro, 2D disk, pseudo-newtonian potential, synchrotron emission [P. Varniere] Red noise: MHD, 2D (vertically-averaged) disk, pseudo-newtonian potential, B-stress proxy emission [P. Armitage] Ejected blob: MHD, axisymmetric 3D blob ejection, pseudo-newtonian potential, synchrotron emission [F. Casse] 19/26 Frédéric Vincent GRAVITY and SgrA* flares

20 Normalized flux 0.8 y (µas) Time (ISCO) x (µas) Rossby Wave 20/26 Frédéric Vincent GRAVITY and SgrA* flares

21 1.0 0 Normalized flux 0.8 y (µas) Time (ISCO) x (µas) Red Noise 21/26 Frédéric Vincent GRAVITY and SgrA* flares

22 Normalized flux 0.5 y (µas) Time (ISCO) x (µas) Ejected blob 22/26 Frédéric Vincent GRAVITY and SgrA* flares

23 10 HOT SPOT μas RED NOISE 150 JET 0 0 y (µas) 10 y (µas) 10 y (µas) μas μas x (µas) x (µas) x (µas) 1 night GRAVITY observation: Rossby / Red Noise / Blob 45 inclination, m K = 14 23/26 Frédéric Vincent GRAVITY and SgrA* flares

24 Inclination: 5 deg, max magnitude: 14 Inclination: 45 deg, max magnitude: 14 Inclination: 85 deg, max magnitude: Dispersion y (µas) Dispersion y (µas) Dispersion y (µas) Dispersion x (µas) Dispersion x (µas) Dispersion x (µas) Dispersion of retrieved positions Inclination: 5, 45, 85 inclination, m K = 14, t = 2 h 24/26 Frédéric Vincent GRAVITY and SgrA* flares

25 Section conclusion GRAVITY can distinguish an ejected blob from "disk-glued models" This is valid for a typical flare (m K = 15, t = 1 h 30) First possibility to start distinguishing flare models Vincent, Paumard, Perrin, Varniere, Casse, Eisenhauer, Gillessen, Armitage, MNRAS, 441, 3477 (2014) 25/26 Frédéric Vincent GRAVITY and SgrA* flares

26 Conclusion Sgr A* flares: - Today: impossible to distinguish models - With GRAVITY (2015): will distinguish an ejected blob Sgr A* imaging: - Today: no direct observation of an accretion structure - With EHT ( ): astrophysical probe near Sgr A*, testing strong-field GR? Thanks for your attention! 26/26 Frédéric Vincent GRAVITY and SgrA* flares

27 Conclusion Sgr A* flares: - Today: impossible to distinguish models - With GRAVITY (2015): will distinguish an ejected blob Sgr A* imaging: - Today: no direct observation of an accretion structure - With EHT ( ): astrophysical probe near Sgr A*, testing strong-field GR? Thanks for your attention! 26/26 Frédéric Vincent GRAVITY and SgrA* flares