Proto-Neutron Star Winds with Magnetic Fields & Rotation (and - PowerPoint PPT Presentation

Proto-Neutron Star Winds with Magnetic Fields & Rotation (and other non-traditional r-process sites) Brian Metzger NASA Einstein Fellow, Princeton University with Todd Thompson (OSU), Eliot Quataert (UC Berkeley), Tony Piro (UC Berkeley) Metzger, Thompson & Quataert 2007, 2008 Metzger, Piro & Quataert 2008, 2009 EMMI r-Process Workshop - July 16, 2010

Astrophysical R-Process Sites τ n << τ β ⇒ NS or BH accretion disk 1) Low Entropy < 1 k b nuc -1 , Y e ~ 0.1 ⇒ Neutron Star Mergers (Dynamical Ejecta) (Lattimer & Schramm 1974, 76; Eichler et al.1989; Freiburghaus et al. 1999; see talk by Goriely) 2) High Entropy > 10 2 k b nuc -1 , 0.4 < Y e < 0.5 ⇒ Neutrino-Driven Wind - Proto-Neutron Stars in Core Collapse Supernovae - Hyper-Accreting Disks (Collapsars & NS Mergers) 3) “Intermediate” Entropy ~ 10 k b nuc -1 , Y e ~ 0.2-0.4 ⇒ Thermonuclear-Driven Winds - Hyper-Accreting Disks (Late Times)

Astrophysical R-Process Sites τ n << τ β ⇒ NS or BH accretion disk 1) Low Entropy < 1 k b nuc -1 , Y e ~ 0.1 ⇒ Neutron Star Mergers (Dynamical Ejecta) (Lattimer & Schramm 1974, 76; Eichler et al.1989; Freiburghaus et al. 1999; see talk by Goriely) 2) High Entropy > 10 2 k b nuc -1 , 0.4 < Y e < 0.5 ⇒ Neutrino-Driven Wind - Proto-Neutron Stars in Core Collapse Supernovae - Hyper-Accreting Disks (Collapsars & NS Mergers) 3) “Intermediate” Entropy ~ 10 k b nuc -1 , Y e ~ 0.2-0.4 ⇒ Thermonuclear-Driven Winds - Hyper-Accreting Disks (Late Times)

Proto-Neutron Star Winds (Duncan et al. 1986; Takahashi et al. 1994; Burrows et al. 1995; Qian & Woosley 1996) Neutrinos Heat Proto-NS Atmosphere (e.g. ν e + n ⇒ p + e - ) ⇒ Drives Thermal Wind Behind Outgoing Supernova Shock Grav. Binding Energy GM NS m n ~ 200 MeV R NS >> Avg. Neutrino Energy � ~ 10 � 20 MeV � ⇒ (1) Final Y e ~ 0.5 set by competition btw � e +n & � e +p (2) High Entropy � � � > GM NS m n � dQ � � � S = � � T Burrows, Hayes & Fryxell 1995 R NS � T NS � � R NS �

Conditions for 2nd/3rd Peak R-Process (e.g. Meyer & Brown 1997; Hoffman et al. 1997) • Low Electron Fraction Ye (fast expansion @ α formation) } • High Entropy S α -rich Freeze Out • Short Dynamical Timescale τ dyn 4 He( α n) 9 Be( α n) 12 C Bottleneck (e.g. Woosley & Hoffman 1992 ) Third-Peak Hoffman et al. 1997 Threshold: S 3 � dyn > f ( Y e )

R-Process Fail Path through S- τ dyn Space (Qian & Woosley 1996; Hoffman et al. 1997; Otsuki et al. 2000; Thompson et al. 2001; Hudepohl et al. 2010) Thompson et al. 2001 Alternative Ideas Entropy Dynamical Time ⇒ 87 Rb, 88 Sr, 89 Y, 90 Zr (see talks by Roberts and Arcones)

R-Process Fail Path through S- τ dyn Space (Qian & Woosley 1996; Hoffman et al. 1997; Otsuki et al. 2000; Thompson et al. 2001; Hudepohl et al. 2010) Thompson et al. 2001 Alternative Ideas • Very Massive NSs (e.g. Cardall & Fuller 1997; Thompson et al. 2001) • Neutrino Oscillations Entropy (e.g. Duan et al. 2010; but see Hudepohl et al. 2010) • Wind-SN Ejecta Interaction (e.g. Wanajo et al. 2001; Arcones et al. 2007) • Wave Heating Dynamical Time – Acoustic (Burrows et al. 2006) ⇒ 87 Rb, 88 Sr, 89 Y, 90 Zr – MHD (Suzuki & Nagataki 2005; Metzger et al. 2007) (see talks by Roberts and Arcones) • Electron Capture SNe (Ning et al. 2007; but see Hoffman et al. 2008) • Magnetic Fields & Rotation

Magnetars (Thompson & Duncan 1995; Kouveliotou et al. 1998; Woods & Thompson 2006) SGR1806-20 Giant Flare December 4, 2004 Counts per second (courtesy: A. Watts & T. Strohmayer) Time (seconds)  Soft Gamma-Ray Repeaters & Anomalous X-ray Pulsars  Surface magnetic fields B dip ~ 10 14 -10 15 G  Rapid rotation at birth as source of strong fields? (e.g. α - Ω dynamo or magneto-rotational instability; Duncan & Thompson 1992; Akiyama et al. 2003)  Fairly common (at least ~10% of neutron stars are born magnetars)

“Helmet - Streamer” Effects of Strong Magnetic Fields • Microphysics (EOS, Neutrino Heating & Cooling) Ω – Important for B > 10 16 G (Duan & Qian 2005) • Closed Zone Heating / Eruptions (Thompson 2003) • Magneto-Centrifugal Outflows (Weber & Davis 1967)

“Helmet - Streamer” Effects of Strong Magnetic Fields • Microphysics (EOS, Neutrino Heating & Cooling) Ω – Important for B > 10 16 G (Duan & Qian 2005) • Closed Zone Heating / Eruptions (Thompson 2003) • Magneto-Centrifugal Outflows (Weber & Davis 1967) R α Top View Outflow Co-Rotates R A with Neutron Star while R heat B 2 8 � > 12 � v r 2 ⇒ 1) Magnetic Acceleration (lower τ dyn ) 2) Enhanced Mass Loss 3) Early Weak Freeze Out (lower Y e )

Proto-Neutron Star Winds with Magnetic Fields & Rotation (BDM, Thompson & Quataert 2007, 2008) INPUT: “Equatorial”  NS Mass, Radius, Rotation Rate, Surface Field Strength Flux Tube  Neutrino Luminosities & Spectrum Ω  Free Outer Boundary OUTPUT: Steady-State Radial Wind Profile: ρ , T, v r , v φ , B φ   Captures 3 MHD Critical Points  Eigenvalues: Mass, Angular Momentum, & Energy Loss Rate +

“Normal” Thermally-Driven Wind L � e ~ 8 � 10 51 ergs s -1 ; B 0 = 10 13 G; P =100 ms (sound speed) R A R s M ~ 10 � 4 M � s � 1 ; S ~ 70 k b nuc -1 ; � dyn ~ 25 ms ˙

Magnetically-Driven Wind L � e ~ 8 � 10 51 ergs s -1 ; B 0 = 10 15 G; P =1.2 ms R A R s M ~ 3 � 10 � 3 M � s � 1 ; S ~ 20 k b nuc -1 ; � dyn ~ 0.5 ms ˙

BDM et al. 2007 Dynamical Timescale 10 13 G τ dyn decreased if 10 14 G 2 G 5/ 6 � � ,10 B dip > 4 � 10 13 L � ,52 5/ 3 P ms 10 15 G

BDM et al. 2007 Dynamical Timescale 10 13 G τ dyn decreased if 10 14 G 2 G 5/ 6 � � ,10 B dip > 4 � 10 13 L � ,52 5/ 3 P ms S 3 / τ dyn 10 15 G But…. MHD acceleration also decreases entropy

Latitude-Dependent Wind Properties? High τ dyn Low τ dyn High S High S R α ? R A R heat Low τ dyn Low S

Latitude-Dependent Wind Properties? High τ dyn Low τ dyn High S High S R α ? R A R heat Low τ dyn Low S R Ye

Electron Fraction (& Mass Loss Rate) Electron Fraction ˙ M BDM et al. 2008 0.7 ms 1.6 ms To appreciably reduce Y e a ⇔ by a factor > GM NS m n R NS � enhancement in ˙ M � ~ 10

Binary Compact Object Mergers NS NS NS NS NS NS BH BH Hulse-Taylor Hulse-Taylor Known Galactic NS-NS Binaries Known Galactic NS-NS Binaries Pulsar Pulsar merge ~ 10 -5 � 10 -4 yr -1 T merge = 300 = 300 Myr Myr T merge ˙ N (Kalogera ( Kalogera et al. 2004) et al. 2004)

Credit: M. Shibata (U Tokyo) Credit: M. Shibata (U Tokyo)

Remnant Accretion Disk Lee et al. (2004) Lee et al. (2004) • Disk Mass ~ 10 -3 - 0.1 M  & Size ~ 10-100 km • Midplane Hot (T > MeV), Dense, & Neutron Rich • Cooling via Neutrinos: ( τ γ >>1, τ ν ~ 0.01-100 ) M ~ 10 � 2 � 10 M • s -1 Accretion Rate ˙ Accretion Rate Short GRB Central Engine?

Magnetized Accretion Disks MHD Turbulence MHD Turbulence Redistributes Redistributes Angular Angular Momentum Momentum J � M d ( GM BH R d ) 1/ 2 � 2 � R d J � M d BH BH Accretion ⇔ Expansion to Larger Radii Hawley & Balbus Balbus (2002) (2002) Hawley &

1D Height-Integrated Disk Evolution M d,0 = 0.1 M  , r d,0 = 30 km, α = 0.3 Angular Momentum Angular Momentum Local Disk Mass πΣ r 2 (M  ) Transport Transport (Viscous Spreading) (Viscous Spreading) Entropy Entropy Heating Heating Cooling Cooling Nuclear Composition Nuclear Composition

Three Accretion 2 Phases (Metzger, Piro & Quataert 2008) 3 1 ˙ 1) High Thick Disk : H ~ R M - Optically Thick; Matter Accretes Before Cooling � e - � Neutrino-sphere Deeper (and Hotter) than Neutrino-sphere e - ν -Driven Wind with low Ye ⇒ r-Process? (e.g. Surman et al. 2006, 2008) 2) Neutrino-Cooled Thin Disk: H ~ 0.2 R ˙ - Optically Thin; Neutrino Luminosity L ν ~ 0.1 c 2 M - ν -Driven Wind with Ye > 0.5 ⇒ ν p-Process? (Kizivat et al. 2010) ˙ 3) Low Thick Disk : H ~ R M - Low Temperature ⇒ inefficient neutrino cooling & weak freeze-out

Late Time Winds Late Time Winds After t ~ After t ~ 0.1-1 seconds, R ~ 500 km & 0.1-1 seconds, R ~ 500 km & T < 1 T < 1 MeV MeV • Recombination: n + p ⇒ He E BIND ~ GM BH m n /2R ~ 3 3 MeV MeV nucleon nucleon -1 -1 E BIND ~ GM BH m n /2R ~ E NUC ~ 7 7 MeV MeV nucleon nucleon -1 -1 Δ E NUC ~ Δ • Thick Disks Marginally Bound

Late Time Winds Late Time Winds After t ~ After t ~ 0.1-1 seconds, R ~ 500 km & 0.1-1 seconds, R ~ 500 km & T < 1 T < 1 MeV MeV • Recombination: n + p ⇒ He } E BIND ~ GM BH m n /2R ~ 3 3 MeV MeV nucleon nucleon -1 -1 E BIND ~ GM BH m n /2R ~ Powerful Winds ⇒ E NUC ~ 7 7 MeV MeV nucleon nucleon -1 -1 Δ E NUC ~ Blow Apart Disk Δ • Thick Disks Marginally Bound M ej ~ M disk /3 ~ 10 -3 - 10 -2 M  BH Neutron-Rich Freeze- Out Composition (Metzger et al. 2008, 2009) ~20-50% of Initial Disk ~20-50% of Initial Disk Ejected Back into Space! Ejected Back into Space! (see also Lee et al. 2009)