Eta Carinae: Clues to Its Binarity Ted Gull Krister Nielsen* Mike Corcoran John Hillier Kenji Hamaguchi Stefan Ivarsson Gerd Weigelt* & AMBER Team * Lead authors in prep

OUTLINE Brief background of Eta Carinae including periodicity Binarity evidence from: Weigelt D STIS spectra ‘Stellar’ Line profiles A Simple model VLTI/AMBER - first result Visualization of wind structure

 Car In late CNO cycle -- N overproduced at expense of C, O the Great Event in 1840s -1 magnitude; bright for 20 years > 12 M o Ejected -> Homunculus another event in the 1890s ~> 0.5 M o Ejected -> Little Homunculus Luminosity~ 5x10 6 L o T e ~15,000K ==>MASS>100 M o Mass Loss Rate: ~10 -3 M o /yr Wind Velocity: km/s Historical spectrum highly variable

Periodic Variability implies Binarity: Damineli (1996) noted spectroscopic 5.52-year periodicity Confirmed in X-rays, IR, visible, UV in Coordinated observations of minimum RXTE period days (M. Corcoran 2005) GTO (Gull), GO and Hubble Treasury (Davidson) monitoring FUSE (fuv dropped during minimum), CHANDRA (dropped to few % during minimum), VLT/UVES + STIS (echelle disp A) Much being learned about properties of ejecta Much being learned about properties of ejecta Homunculus: -513 km/s Fe I, V II, Ti 760K H 2 photoexcited during max, CH, OH, NH, CH + 60K Homunculus: -513 km/s Fe I, V II, Ti 760K H 2 photoexcited during max, CH, OH, NH, CH + 60K Little Homunculus: -146 km/s Fe II, Cr 6400K --> 5000K minimum Little Homunculus: -146 km/s Fe II, Cr 6400K --> 5000K minimum Strontium filament : Neutral emission region excited by Balmer continuum Strontium filament : Neutral emission region excited by Balmer continuum

B, C and D are very bright emission clumps located to NE Photoexcited by Eta A & Eta B Projected distance: AU Proper motion, velocity suggest in skirt between lobes, tilted at 45 0 to skyplane  Car and Weigelt Blobs Weigelt et al 1995 RMxACSmith et al 2005 ApJ Weigelt blob excitation requires UV flux of 37,000K Companion (Eta B) Verner, Bruhweiler, Gull 2005

Balmer alpha changes: periastron to apastron Periastron: Near-Apastron: Red=Periastron Blue=Near-Apastron Eta Carinae Weigelt D (D) _D_D D  _D_D P Cygni Absorption not present in Weigelt D except during periastron

He I lines blueshifted relative to H I wind lines He I lines appear to have narrow substructure for most of period He I 7065 H I 4103

H I 4103, He I 7065, Fe II 5170, [N II] 5756 comparison He I 7065H I 4013

STIS Radial Curves derived from: 9 H I Balmer, Paschen lines 4 He I: 2 singlet & 2 triplet RXTE X-ray flux H I Absorption He I Absorption Velocities

Geometry of Wind Interactions 15000K 500 km/s 3x10 -4 M o /yr 37000K 3000km/s M o /yr Gas pileup from primary wind Primary wind envelopes most of binary system, except dynamic cavity carved out by secondary wind.

2-D model of wind- wind Interface in orbital plane. Pittard & Corcoran: D=30 AU, e=0.9

VLTI/AMBER Weigelt et al. In prep. ~ 5 mas H I Br  He I 2 1 S P R= 10,000 R= 1500 R=1500

VLTI/AMBER IR Cont: 4 mas H I: 4-6 X centered on continuum He I emis~3X; offset? He I absor: ~4 mas R=1500

Apastron: March 2006 VLTI/AMBER observations: We look for Eta B in continuum ~2% flux of Eta A ~8 mas PA  135 o ; He I emission velocity components along wind-wind interface Issue: sufficient UV-plane sampling? Conclusion/ Frustration STIS observations of H I, He I, Fe II ‘wind’ lines & Weigelt blobs consistent with hot binary companion blowing cavity in primary wind and He II ionization leading to He I recombination Prediction: The Holy Grail --> Eta Car B Velocity curve does not (easily) provide mass ratio.