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Eruptive Mass Loss in Massive Stars Nathan Smith - University of Arizona

Eruptive Mass Loss in Massive Stars Nathan Smith - University of Arizona. OUTLINE. Intro: Mass Loss in Massive-Star Evolution Winds vs. Eruptions: Mass/ Metallicity dependence? Lessons from Eta Carinae : 1843 Eruption: Poster child for episodic mass loss events

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Eruptive Mass Loss in Massive Stars Nathan Smith - University of Arizona

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  1. Eruptive Mass Loss in Massive Stars Nathan Smith - University of Arizona

  2. OUTLINE • Intro: Mass Loss in Massive-Star Evolution • Winds vs. Eruptions: Mass/Metallicity dependence? • Lessons from Eta Carinae: 1843 Eruption: Poster child for episodic mass loss events • Diversity of LBVs and Extragalactic Transients: LBVs: Diversity of winds, eruptions, spectra. • Type IIn Supernovae and Circumstellar Gas: Pre-SN mass loss: Evidence for precursor LBV-like eruptions. • Dust formation/survival in Type IInSNe: Special circumstances: Dense CSM.

  3. END FATES of MASSIVE STARS: What type of supernova from which type of star? Single-star mass-loss (STELLAR WINDS and ERUPTIONS) Type II-P II-L IIb Type Ib Type Ic (GRB) Heger et al. Woosley et al. Maeder & Meynet Type IIn /Ibn Binary-star mass-transfer (ROCHE LOBE OVERFLOW) Mass loser Mass gainer Mass gainer Paczynski et al. 67; Podsiadlowski et al. 92 Image courtesy M. Modjaz

  4.       Mass loss and stellar evolution: LBV winds/eruptions  = L/4GMc LBV 120 M SUPER EDDINGTON CONTINUUM-DRIVEN WINDS/OUTBURSTS Smith & Owocki 2006 Owocki et al. 2004 Shaviv et al. 2001 ? 60 M WR SN Ib/c Theorists don’t know what makes LBVs erupt

  5. Single-Star Evolution (consequences of overestimated mass loss rates)  Evolutionary tracks for massive stars depend on adopted steady mass loss rates (e.g., Maeder & Meynet 1994, 2000, 2003; Heger et al. 2003). Problem: more recent modeling of spectra of O stars winds find LOWER mass-loss rates than “standard” by factors of 3-10 or more. (Factor of >3; Bouret et al. 2005; Factor of >10; Fullerton et al. 2005). Why are O-star winds clumpy? See papers by Owocki & Rybicki and this morning’s talk by Sunqvist zero metallicity? 120 MS clumped Smith & Owocki 2006 ? M/M MS homogeneous WR 20 2.5-3 Myr t = 0

  6. Single-Star Evolution (consequences of overestimated mass loss rates)  Evolutionary tracks for massive stars depend on adopted steady mass loss rates (e.g., Maeder & Meynet 1994, 2000, 2003; Heger et al. 2003). Problem: more recent modeling of spectra of O stars winds find LOWER mass-loss rates than “standard” by factors of 3-10 or more. (Factor of >3; Bouret et al. 2005; Factor of >10; Fullerton et al. 2005). zero metallicity? 120 MS clumped Smith & Owocki 2006 LBVs M/M MS homogeneous Type IIn Type Ib/c WR 20 2.5-3 Myr t = 0

  7. DUST MASS Md ~ 0.1-0.15 M in one event! (Smith et al.) Up to Md ~ 0.4 M including previous events? (Gomez et al. 2011) Gemini South/Phoenix R=60,000 1.644 m [Fe II] 2.122 m H2 1-0 S(1) Smith (2006) ApJ, 644, 1151 Range of Ejecta Speed = 40 - 650 km/s Follows a Hubble law Ejected mass = 10-15 M KE = 1049.6 - 1050 erg Erad = 1049.7 erg Eta Carinae’s 1843 eruption: Wind or Explosion? KE/Erad ≈ 1

  8. Massive Dusty Molecular Shell Outer shell Cool dust 140 K Molecular hydrogen Thin shell Inner Shell Warm dust 200 K [Fe II] emission, etc. Thick shell ne=104 cm-3 CLOUDY models: survival of H2 requires a density of nH = 106.7-7 cm-3 in the outer shell, implying a total gas mass of 17-35 M. Smith & Ferland (2007, ApJ, 655, 911)

  9. Massive Dusty Molecular Shell • Despite Eta Car being an extremely luminous hot star, several molecules have been detected: •  Near-IR H2 lines – first detection of molecules • (Smith & Davidson 2001; Smith 2002; Smith 2006) • NH3 (3,3) - Ammonia detected with ATCA • (Smith et al. 2006) • CH, OH detected in UV absorption with STIS • (Verner et al. 2006; Nielsen et al.; Gull et al.) •  CO, 13CO, CN, HCO+, HCN, HNC, H13CN, N2H+ detected with APEX (Loinard et al. 2012; arXiv:1203.1559) • Eta Car is unique laboratory for rapid molecule and dust formation in N-rich ejecta around hot stars. • Will the Dust & Molecules survive the SN? Ammonia in the outer H2 shell of Eta Carinae (Smith et al. 2006, ApJL, 645, L41)

  10. [O II] [O III] Hb CHEMICAL ABUNDANCE CHANGES IN THE OUTER EJECTA Smith & Morse 2004 Multiple eruptions… N/O ≥ 20 N/O ≈ 1 HST/WFPC2 F502N [O III]F658N [N II] N/O ≈ 0.1 LBV eruptions can trigger sudden changes in chemical abundances… Nitrogen enrichment gets weaker at larger radii.

  11. Eta Carinae had multiple previous eruptions. Another generation of stars is still forming nearby… Most massive stars live fast, die young, etc. This might actually matter in starburst regions, early universe, proto-GC’s …

  12. P Cygni: the only other nebula from a Galactic giant LBV eruption that was actually observed. ERad = 2.51048 ergs The historical light curve of P Cygni (de Groot 1983) Smith & Hartigan 2006, ApJ, 638, 1045 [Fe II] 1.644 um NICFPS Ginsburg, Smith, & Bally (in prep.) 1600 AD shell: From [Fe II] lines: M = 0.1-0.2 M . M = 0.01 M/yr KE = 1047 ergs Mass and KE similar to 1890 outburst of Eta Car’s Little Homunculus. ~1200 yr old { 400 yr

  13. P Cygni OBSERVED MASSES OF LBV NEBULAE In LBV shells, mass of ~10 M is typical for L* > 106 L. Mass-loss rates of 0.01-1 M/yr… …beyond limitations of a line-driven wind (~10-4 M/yr * L6) Requires continuum driving or hydrodynamic explosions. Both are insensitive to metallicity. Smith & Owocki (2006) ApJ Letters, 645, L45 HD 168625 (Smith 2007) Sher 25 (Brandner+97) AG Car (S. White) Pistol Star (Figer+99) Eta Car

  14. Observing Giant Eruptions of Massive Stars Review of giant eruption light curves and spectra (see Smith et al. 2011, MNRAS, 415, 773) Unpredictable, violent, and erratic variability

  15. “giant eruptions” Luminous Blue Variables (a.k.a. Hubble-Sandage variables) H&S ’53 • Eta Car • Pistol *  ~ 0.9 WNH .Sher 25 +  ~ 0.5 Wolf-Rayet (WC, WN) RSGs . SN1987A Lower-Luminosity LBV-like ERUPTIONS? MS Smith, Vink, & de Koter (2004)

  16. Main Lesson: LBVs and related phenomena are more diverse than we thought Broad spectrum of energy, luminosity, duration, spectral properties… • Eta Car • Pistol * Explosions / eruptions / winds Surface instability? …or deep energy deposition? Covering a wider range of initial Mass Don’t have good observational constraints on brief and relatively faint eruptive events. (so far, just tip of the iceberg…) …PTF, Pan-STARRS, LSST RSG ? . M.S. SN1987A AGB PNe also: binary mergers, electron capture SNe, etc.

  17. Massive Star Eruptions Create Dense and Dusty Circumstellar Shells… What happens when they explode as Supernovae? Type IIn Supernovae (n = narrow H lines) Efficient conversion of KE Light

  18. CONSTRAINTS FROM SUPERNOVA PROGENITOR STARS IIb IIn II-P II-L Smith et al. (2011) MNRAS, 412, 1522 Type II-P RSGs with initial mass 8.5 – 20 M (20) Type Ibc Zero detections. Type IIb 13-18 Mbinary (2) Type II-L 18-25 M (2) Type IIn >25 M (3+) Type IIn supernovae are seen over a range of metallicity, including low-Z dwarf galaxies.

  19. PROPERTIES OF SN2006gy’s CSM A Massive LBV-like Shell: Clues from Spectral Evolution • .Time evolution of narrow H • (Smith et al. 2010, ApJ, 709, 856) • Narrow absorption gets weaker... • …running out of CSM? • Narrow absorption gets broader... • …faster CSM at larger radii? Narrow Int. Broad

  20. PROPERTIES OF SN2006gy’s CSM A Massive LBV-like Shell: Clues from Spectral Evolution • .Time evolution of narrow H • (Smith et al. 2010, ApJ, 709, 856) • Narrow absorption gets weaker... • …running out of CSM? • Narrow absorption gets broader... • …faster CSM at larger radii? Hubble Flow at 150-500 km/s Suggests 1049 erg ejection ~8 yr before SN (fall 1998) Narrow Int. Broad

  21. PROPERTIES OF SN2006gy’s CSM 1-2 Years Later…IR Echo from dusty outer shell Keck LGS/AO infrared visual Smith et al. 2008, ApJ, 686, 485 Smith et al. 2010, ApJ, 709, 856 Miller et al. 2010, AJ, 139, 2218 IR/optical echo: Massive dust shell at R=0.5-1 light year (ejected 1500 yr before SN). Requires at least 0.1 M of dust ( > 10 M total mass).

  22. PROPERTIES OF SN2006gy’s CSM 1-2 Years Later…IR Echo from dusty outer shell Multiple massive shell ejections. Inner massive shell, H-rich, 10-20 M, 100-600 km/s, Hubble law Keck LGS/AO infrared visual Dusty light echo: Outer massive shell, R ~ 1 ly ejected ~1000-2000 yr earlier …another 10 M

  23. SN2006jc SN 2006jc had an observed precursor eruption 2 yr before exploding as a supernova… 2 yr Explosion of WR star with dense CSM  Foley et al. 200, ApJ, 657, L105 Pastorello et al. 2007, Nature, 447, 829 Smith, Foley, & Filippenko 2008, ApJ, 680, 568 Dust Formation 

  24. Foley et al. (2007) Surprising Dust Formation in SN 2006jc Smith, Foley, & Filippenko 2008 3 lines of evidence: #1 Rapid fading #2 Infrared emission from hot dust #3 Far side blocked …faster than 56Co decay

  25. Surprising Dust Formation in SN 2006jc Smith, Foley, & Filippenko 2008 3 lines of evidence: #1 Rapid fading #2 Infrared emission from hot dust #3 Far side blocked Day 51 Day 75 Day 102 Hot dust at ~1600 K. Dust cools fast and piles up downstream. Total dust formed: Md0.01M (Smith et al. 2008) From later near/mid-IR obs: Md 0.008M (Matilla et al. 2008) Day 128 Smith et al. 2008

  26. Vel. (103 km/s) Surprising Dust Formation in SN 2006jc Smith, Foley, & Filippenko 2008 3 lines of evidence: #1 Rapid fading #2 Infrared emission from hot dust #3 Far side blocked This is Wavelength- Dependent (stronger in blue em. lines) …but only seen in the narrow He I lines in the post-shock gas (swept-up CSM)

  27. SN2006jc • . • Where did the dust form? Blueshifted narrow He I lines: also from Zone 2 DUST FORMED IN THE SHOCK • Shocked CSM gas? (forward shock) • Shocked SN ejecta? (reverse shock) Type Ic SN SN ejecta C-rich? CSM He-rich

  28. Dust in/around Type IIn Supernovae • IR Echoes from Pre-existing dust • SN 2006gy ~0.1 M (Smith+08; Miller+10) • SN2010jl 0.03-0.35 M( Andrews+11) • several SNe IIn (Fox et al. 2009. 2011) • Blueshifts suggest some new dust formation • in post-shock gas as well. • SN 1995N (Fransson+02) • SN 1998S (Pozzo+04; • molecules - Gerardy+00) • SN 2005ip, 2006tf, 2008iy, 2010jl, others… • (Smith+2008,2009,2012; Miller et al. 2010) dust formation in post-shock shell.

  29. Massive star eruptions: Potential sources of dust in the early Universe? • Pre-SN Eruptions enable dust production in 2 ways: • Pre-existing dust seen as IR echoes. • LOTS of dust – of order 0.01-0.2 M • 2. New dust formation in post-shock gas when SN collides with dense CSM. • Radiative cooling and collapse of post- shock shell facilitates efficient dust formation. • Key questions: • Will that new dust survive? • SNe IIn: slower shocks • no UV flash from shock breakout • dust already behind shock • Are there enough eruptive stars to do it? • ? … Early universe, low-Z, etc. 1.2 mm observations of z>6 quasars reveal huge amounts of dust. (Bertoldi et al. 2003, AA, 406, L55) MD = few  108 M Dust production of ~1 M/yr. ~0.01 M per SN…

  30. SUMMARY • Intro: Mass Loss in Massive-Star Evolution • Eruptions: Dominate mass return, work at low-Z • Eruptions of LBVs - Eta Carinae et al.: Lots of mass return: CNO processed, dusty, molecule rich • Luminous Type IIn Supernovae and Circumstellar Gas: • Pre-SN mass loss: Evidence for precursor LBV-like eruptions. 9% of all ccSNe: probably large fraction of very massive stars. • Dust formation/survival in Type IIn SNe: Special circumstances: Dense CSM, more dust than other SNe. • Qualitatively different from normal SNe: post-shock dust, • no (or weak) UV flash from shock breakout…

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