Eta Carinae: A Demanding Mistress…

Ted Gull NASA/GSFC Outline of Talk: Description of Eta Carinae and its ejecta The central source Interacting winds revealed by [Fe III], [Fe II] Modeling the 3D wind structures Mapping the structures with phase A short glimpse of Herschel data

Working assumption: Eta Carinae is not an unusual massive binary. . . One of its members has gone through a very brief transition common to most massive stars. . . i.e. massive ejection before Wolf-Rayet stage leading eventually to SN, hypernova or GRB Multispectral studies will provide insight to massive star evolution, possibly of the first stars.  Tom Madura, Jose Groh, Gerd Weigelt, MPIR  Stan Owocki, Chris Russell, Univ Del, USA  Atsuo Okazaki, Hokkai Univ, Japan  Mike Corcoran, Kenji Hamaguchi, GSFC, USA  John Hillier, Krister Nielsen, Univ Pittsburgh, USA  Sveneric Johansson*, Henrik Hartman, Univ Lund, Sweden  Manuel Bautista, N Michigan Univ, USA  Vincent Icke & Chael Kruip, Univ Leiden, Netherlands  Karl Henize* & Bart Bok* who introduced Eta Car to me!  * deceased 0.2-1.5/1.5-3.0/3.0-8.0 keV

X-rays

blue (oxygen) green (warm hydrgen) Optical/IR red (cool sulfur)  A Luminous Blue Variable 6  Total luminosity: 4-5 x 10 L  Actually a massive binary with LBV primary

 Currently Eddington Limit: >110 M

 Initial total mass of system ≈150 M?

 Primary ~ 90 M LBV; Secondary ~30 M O? or WN?  A near-supernova explosion in the 1840s

 >12-40 M at 600 km/s, yet the binary survived!  External structures suggest previous ejections, fossil winds  Sufficiently nearby  We can study its ejecta and wind structures in some detail  Clues on evolution to GRB, hypernova or SN end states Great Eruption Great Eruption

(10 – 40 Mo) 0 Eta Car has had two historical Formation of eruptions, but is gradually Homunculus (3-20M ) brightening…  Is this unveiling of the 40-fold circumstellar extinction, or evidence of future instability?

See Smith & Frew Lesser Eruption 2011 MNRAS 415, 2009 6 for revised light curve (0.5 Mo)

see Fernández-Lajús et al. (2009, A&A, 493, 1093) http://etacar.fcaglp.unlp.edu.ar/ 1000’s of emission & absorption lines from: Homunculus Nebula:

 an outer dusty bipolar shell with skirt (10-40 M) +  Tion=720 K; Tmolecules <40K (H2, NH, OH, CH )  expanding at 600 km s-1 (the 1840s event)  Metals Fe, Ni, Na, Ti, Mg, Mn … plus V, Sr, Sc not seen in ISM Little Homunculus:

 interior bipolar shell with skirt (0.1 – 1 M)  ionized: T ≈5000K low state, 6000K high state  -1 expanding at 200 km s (1890s event) H2 + Weigelt Blobs at ~-40 km s-1 Homunculus  1840 Great Eruption [Fe II] Little Homunculus  1890 brightening  Massive stars (40 to 100 M) last only a few million years, lose -5 mass by their winds at 10 M/year yet their supernovae are <10M. How do they lose more than half of their mass?  The most massive stars, by CNO nuclear reactions, overproduce N at the expense of C and O, the bases for dust and molecules.  Yet dust is significant in the Homunculus… How did dust form?  What molecules exist in the Homunculus? What is the dust?  Eta Carinae in the 1840s suffered a massive ejection with energies comparable to a supernova, yet the binary survived. How?  Which star underwent the ejection?  What explosive force led to ejection, but survival of a binary?  What are the near term and long term fates of Eta Carinae?  Does Eta Carinae provide clues to the evolution of the first stars, hypernovae, Gamma Ray Bursters?  Luminous Blue Variable  Top of HR diagram  CNO cycle w/convection has led to huge excess N, greatly depleted C, O.  Future Evolution  Evolve through Wolf Rayet stages with episodic mass loss?  A Future SN or GRB/ Hypernova Candidate?  How do massive stars shed most of their mass before SN stage? Langer et al. 1994, A&A, 290, 819  Optical: long high state, short low state (ground-based)  high state: (> 14 eV) broad lines of He I, He II and high excitation ([N II], [S III], [Ar III], [Fe III], [Ne III])  low state: (< 8 eV) He I weakens, [Fe II], [Ni II] strengthen, high excitation lines disappear  X-ray: coincident with optical variations (RXTE, M. Corcoran)

High state High State Low Low Low  X-ray Minimum: drops by 100 from peak  Three major puzzles:  Eclipse : Why minimum continued for ≈3 months?  What is the mechanism for X-ray drop?  Why shorter recovery in 2009.0?  High Excitation  FUV tracer  Both suggest  wind-wrap  new cavity  Drop in primary wind

 The central source has been cloaked for >160 years  100’s of broad lines in the UV/optical spectra originate from winds.  Dust within 0.1” diameter (230 AU) occults the central source 40-fold  Yet the dust clears 115AU w/i 1 year  Hence dust continuously forms. How?  Properties of Eta Car A and B can only be inferred indirectly.  Weigelt B, C & D are photoionized by Eta Car B  He I, [Ne III], [Fe IV] narrow lines  Little or no dust between Eta & blobs  Other, fainter ionized condensations and non-FUV ionized! Parameter! Value! -1! V∞ (Eta Car B)! 3000 km s -4 -1 ! M . Eta Car A 3.5x10 M yr ??

-5 -1! M Eta Car B! 1.4x10 M yr . e! >0.9! a! 15 AU!

P! 2022.7+/- 1.3 days!

ω! 270o!

θ=0! φ=0 (start of X-ray minimum)!

-1 V∞ (Eta Car A)! 550 km s ??! He 10830 seen by CRIRES R~100,000, 0.2” spatial • Advantage of HST/STIS: R=8000, 0.1” angular

GTO, GO and Treasury programs 1998-2004.3 resolution separates the spectrum of Eta Car provided a wealth of info. from the nebular spectra. ERO, CHANDRA/HST and now multi-cycle mapping •But… samples only part of the wind structure! observations enhance that treasure. Must map the extended interactions!

STIS 52”X0.1” slit

HST red image Weigelt et al 1995 RMxAC High State Low State

He I

[Fe II]

[Ar III]

H I [Fe III] [Fe III]

He I [Ne III] [N II] [Fe II]

[Ar III] [S III] [Fe II] Fe II  Using these spectro-images, I deduced that the wind cavity had to be pointed towards us (blue-shifted arc) and that the hot secondary likely was moving clockwise (what structures disappeared first), possibly in the skirt plane.  Proving such was a bigger challenge. Very simplistic model explained He I emissions and velocity shifts coming from wind-wind interaction zone.  3D models deemed too challenging by several researchers.  Owocki & Okazaki: Smoothed Particle Hydro  Tom Madura builds SPH as thesis project . . . Needed a bulldog approach. Still to come: full hydro with radiative transfer . . . Courtesy of Vincent Icke -3 Primary = 10 Mo/yr Cube with physical sides P = 2024 days = 5.54 years 308 AU ~0.13” … HST/STIS slit 0.10” width ε = 0.9, a = 15.4 AU, η = 50/3  FUV radiation or shocks ionize wind structures  [Fe III] > 16 eV … [Ar III] … [Fe IV] … [Ne III] >40 eV  He I > 24 eV or collisions to 2S, He II > 54 eV  Wind-wind collisions compress gas  X-ray emission from apex of wind-wind collision zone  He I, He II emission from near the apex of the collision zone in the primary wind gas.  Extended ballistic wind collision zone that is illuminated by FUV from Eta Car B at/near critical density, 8 -3 Ne~10 cm , traced by [Fe III] out to ~700AU  More extensive regions of primary wind excited by mid- UV, ~8 eV, and/or collisions near critical density revealed by [Fe II] out to ~1700AU [Fe III] from wind-wind interface [Fe II] from primary wind: Requires FUV AND critical density! NUV AND crit density

1”X1” FOV [Fe III] 4659A [Fe III] 4703A [Fe II] 4815A

-600 0 km/s +600 -600 0 km/s +600 -600 0 km/s +600 [Fe III] 4659A [Fe III] 4702A [Fe II] 4815A

0.045

0.213

0.407

0.952

1.040

1.122 10 X Bigger

-3 Primary = 10 M/yr P = 2024 days = 5.54 years Cube is ~3000AU or 1.3” ε = 0.9, a = 15.4 AU, η = 50/3

Synthetic Slit Spectra from 3-D SPH Sims i ≈ 130 to 145°, θ≈ -15 to +30° PA z ≈ 302 to 327°

Orbital axis is aligned with Homunculus polar axis in 3-D space

Companion orbits clockwise on sky • Emission originates from inner (<0.1’’) current wind-wind collision zone & • the blue-shifted, 0.3”arc emission is from ballistic shell formed in previous 5.5-year cycle. • Phase variations are due to eccentric binary and distorted wind-wind collision zone. • STIS 0.1”-wide aperture sampled only a central slice of the extended wind structures. • Models constrain absolute orientation of orbit, with i≈138°,

θ≈ -15 to 30°, and PA z ≈ 302 to 326°, implying an orbital axis aligned in 3-D space with the Homunculus polar axis • The secondary star orbits clockwise on the sky. • Improved model and future mappings across 2014.5 periastron will constrain wind parameters, changes with time and FUV properties of the hidden secondary. [Ni II]7413A

Center

[Fe II] 4815A

[Fe III] 4659A

[Fe III] 4702A

Position Angle is +79o Spacing 0.1” between frames. Each box is a spectro-image: Vertical scale 2”, Horizontal scale: 1200 km/s +++./0120334++5,67+&++ 9:*+;;;<++5=%7& 9:*+;;;<++5,$>& 9?;;<++%,%=& "#$ !"# !$# !%# !&# $#%

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Molecules and dust form in the interacting wind structures. But in a C, O-depleted gas, what molecules and dust form?  Radiative-transfer combined w/hydrodynamical modeling will lead to prediction of cooling structures within the winds.  Test by HST/STIS maps of [Fe III] and [Fe II]  Herschel observations search for molecular products  ALMA will map molecular ejecta and the wind- wind interactions regions.