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00 Shocking Truth about Massive Stars Lidia Oskinova Wolf-Rainer Hamann & Achim Feldmeier Potsdam University, Germany ACIS Raw Detector Image of O-type supergiant ζ Puppis, CXO archive Chandra’s First Decade of Discovery 22 - 25 September 2009, Boston, Massachusetts, USA Massive Stars and Stellar Winds Initial mass M∗ > 15M⊙ Main Sequence: OB-type Fast evolution (~Myr) star formation trace Hot. T eff > 10 000 K high surface brightness → Photon momentum → acceleration of matter Radiative acceleration larger than gravitation → supersonic STELLAR WIND nasaimages.org 03 OB stars are X-ray active (Einstein observatory 1978) Hot stars: radiatively driven stellar winds Supersonic stellar winds are intrinsically unstable Shocks Heating X-Rays Shocks also result from: Collision of streams in magnetically confined wind Collision of winds in binaries 04 X-Ray Spectroscopy of Massive Stars ζ Ori Prediction of hydrodynamic models NASA/EIT/W.Waldron, J.Cassinelli Models predict: X-ray emitting plasma (T X = 1...10 MK) permeated with warm (T = 10 kK) absorbing wind X-rays originate at few R * from the core X-ray spectroscopy is needed! Distance [R ] Feldmeier et al. 1997 Photo: G. Emerson, E.E. Barnard Observatory 05 Chandra is in Orbit!!! Cheering crowd prague-life.com 06 O-type stars NVII OVII OVIII FeXVII FeXVII OVIII FeXVII NeIX FeXVIII NeX NeX MgXI MgXII SiXIV SiXIII SXV 07 ζ Pup O4I 0.2 0.1 0.0 ζ Ori O9.7I o normalized counts/sec/A 0.1 0.0 0.03 ξ Per O7.5III 0.02 0.01 0.00 0.10 ζ Oph O9V 0.05 0.00 4 6 8 10 12 14 16 o Wavelength (A ) 18 20 22 24 26 Oskinova etal. 2007 08 Analyses of the HETGS spectra Emission line profiles Broad; width scales with wind speed Line formation: deep in the wind Similar accross the spectrum Clumped wind treatment is needed FIR line ratios Formed close to the photosphere Temperature decreases outward Abundances Agree with wind abundances Wojdowski & Schulz (2005), Oskinova etal (2006), Waldron & Cassinelly (2007), Zhekov & Palla (2007), etc. v∞ = 2450 km/s ξ Per o O7.5III 0.02 0.01 0.00 0.12 v∞ = 1550 km/s 0.10 o Range from 2 MK to 10 MK Flux (Counts/sec/A ) Temperature Flux (Counts/sec/A ) 0.03 ζ Oph O9V 0.08 0.06 0.04 0.02 0.00 12.0 12.1 12.2 o Wavelength (A ) 09 Wind-shock Theory has Predictive Power UV and X-ray spectra P V 3p 2 P - 3s 2 S 1.5 microclumping PV resonance doublet Rel. Flux micro- & macroclumping Mass-loss rates! 1.0 X-ray line profiles 0.5 X-ray spectra 0.0 1100 1110 1120 1130 o λ/A 1140 Oskinova et al. 2007 0.20 DEM distribution Ç same M Normalized Flux o 10 clumped wind Flux (Counts/sec/A ) 8 0.2 −4 7 10 T [K] −8 6 10 −12 0.1 smooth wind 5 10 0 5 10 15 x = r/R∗ 20 Krticka et al. 2009 25 30 0.0 −1.0 −0.5 0.0 0.5 Normalized Frequency Oskinova et al. 0.15 ζ Pup NeX 0.10 0.05 0.00 1.0 12.0 12.1 12.2 o Wavelength (A ) 10 B- 11 15 16 17 18 α Cru OVII OVIII FeXVII FeXVII OVIII FeXVII 20 21 NVII 19 22 23 24 α Cru 37 38 25 26 27 28 29 30 31 32 33 39 40 41 42 43 44 45 46 o Wavelength A 47 48 35 36 FeXVI SiX FeXVI 24 SiXI MgX 23 SiXI FeXVII SiX Normalized counts CVI 14 NVII 13 FeXVIII NeIX Chandra observations of α Cru 34 49 50 51 X-ray brightest massive star on sky B0.5IV+BV at d=98 pc Companion B1V Soft spectrum T X =1..3 MK 37 52 Oskinova et al. in prep. 12 Stationary plasma in B-stars Wind speed is 1500 km/s But lines are narrow Comparable to instrumental profile! He−like ions: f/i line ratio probes distance to stellar photosphere Flux (Counts/sec/Angstrom) OVII α Cru Capella λR 0.0 21.5 21.6 λI 21.7 21.8 X−ray plasma in B−stars Close to the photosphere Stationary Different from shocks in O−type winds Pulsations? Coronae? λF 21.9 22.0 22.1 22.2 12a The evolution of (very) massive stars 7 100 T eff / kK 50 20 10 5 Mass removal by wind drives the evolution OB (short LBV) WR Winds are getting dense and more enriched log L / L 6 WR Wolf−Rayet (WR) stars LBV OB 40 M WN → WC → WO → SN 5 ZAM S 4 5 4 log T eff / K Credit: NASA/CXC/SAO/F.Seward et al 13 WR124 WN8−type Observed serendipitously by Chandra WN8 stars are X−ray quiet Wolf-Rayet type stars Image courtesy of D.Ducros and ESA 14 X-ray view on Wolf-Rayet Stars Not all WN−type stars emit X−rays. Lack of X−rays cannot be attributed only to the wind opacity (Oskinova et al. ’06) X−ray spectra of single WN stars are harder than spectra of O−stars (Ignace et al. 2003) Single WC stars are X−ray quiet (Oskinova et al. 2003) X−ray bright WR stars are binaries (Oskinova & Hamann 2008) ζ Pup (O−type) WR 1 (WN) WR 114 (WC) 16 Closest WO-type Star WR142 in the Star Cluster Berkeley 87 Combined Spitzer (red+green) and EPIC (blue) image of the SFR ON 2 Only three WO stars are known in the MW WO is the latest possible evolutionary stage of massive star Core−collapse within 10 000 yr WR 142 Oskinova et al. in prep. Strongly influence their environment 17 Glimpse at the pre core-collapse star Rel. Flux 9.54 8.89 8.60 -14 7.63 7.23 7.10 -15 2 1 0 6.69 He II 5 - 4 3 -13 o log F λ [erg s -1 cm -2 A -1 ] -12 10000 10500 λ/A o -16 5.35 -17 3.5 Oskinova et al. 2009 4.0 4.5 o log λ / A 5.0 5.5 Requires state−of−the art non−LTE models to fit observed optical and UV spectra. Such as PoWR code (Hamann et al. 2006) T =160 kK, R =0.5R , wind speed v=6000 km/s * * Our analysis indicates that star may be a FAST ROTATOR V rot sin i =4000 km/s. Current mass ~10 M 18 Discovery of X-ray emission from a WO-type star Strong enhancement by CO * opaque for the X−rays * winds should be very X-rays are too hard to be explained by wind shocks Hint on the presence of magnetic field B(r=2R ) > 7 kG * * Chandra detects hard X−rays from another compact fast * rotator WR2 (WN2) 0.00300 0.00250 0.00200 0.00150 0.00100 WR142 0.00050 1.0 Oskinova et al. (2009) 2.0 3.0 4.0 5.0 keV 6.0 7.0 8.0 Mystery of X-rays from WR stars: Connection With Collapsars (?) ’’A very energetic explosion of a massive star is likely to create a ... fireball.... the inner core of a massive, rapidly rotating star collapses into a ~10 M Kerr black hole ... A superstrong ~10 15 G magnetic field is needed to make the object ... a microquasar. Such events must be vary rare...to account for the ... GRBs’’ Do we indeed observe in our Galaxy massive, magnetic, rapidly rotating stars on latest stages of their evolution ? 20 Shocking truth? O−stars: X−rays are generated by wind shocks B−stars: not clear: magnetic fields, pulsation, winds. WR−stars: no hi−res spectrum exists! Magnetic field, rotation. X−rays are sensitive probe of stellar winds Generation of X−rays in stellar winds is important physical problem X−rays provide insights in stellar structure and evolution Chandra