Merging Compact Binaries. Dong Lai Cornell University

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1 Merging Compact Binaries Dong Lai Cornell University U.Chicago Astrophysics Colloquium, 10/29/2014

2 Merging Compact Binaries 1. Neutron Star/Black Hole Binaries 2. White Dwarf Binaries

3 Transient & Variable Universe Wide-field, fast imaging telescopes in optical: PTF(iPTF,ZTF) Pan-Starrs LSST

4 Transient & Variable Universe Wide-field, fast imaging telescopes in optical: PTF, Pan-Starrs, LSST

5 Gravitational Wave Astronomy LIGO VIRGO

6 Merging NS and BH Binaries

7 NS/NS Binaries: Binary Pulsars Nobel Prize 1993 Hulse-Taylor Pulsar Weisberg et al. 2010

8 NS/NS Binaries: Binary Pulsars Hulse-Taylor Pulsar Weisberg et al Double pulsars Kramer et al. 2014

9 NS/NS Binaries: Binary Pulsars Hulse-Taylor Pulsar Weisberg et al Double pulsars Kramer et al (Based on 3 systems in Galaxy that will merge within Hubble time; No observed NS/BH and BH/BH yet!)

10 NS-NS Merger Shibata et al. 2006

11 BH-NS Merger F. Foucart et al (Cornell) 2011,13 Ph.D. 11 CITA UCB

12 BH-BH Merger Cornell-Caltech collaboration

13 The last few minutes: Gravitational Waveform

14 Gravitational Waves Warpage of Spacetime Generated by time-dependent quadrupoles Detector response to passage of GWs:

15 Gravitational Wave Interferometer Kip Thorne

16 iligo: reached h~10-21 (2006) eligo: h ~ 1/2 smaller (2010) aligo: h ~1/10 smaller (2018?), reach 200 Mpc

17 Kip Thorne

18 Gravitational waves probe nonlinear gravity Cornell-Caltech collaboration

19 Gravitational waves probe NS EOS Masses well measured from inspiral waveform Final cut-off frequency ~ (GM/R 3 ) 1/2 Cutler et al. 92; DL & Wiseman 96; Shibata et al. 06; Bauswein, Janka... 12,14

20 NS/NS and NS/BH Mergers: Electromagnetic Counterparts

21 Gamma-Ray Bursts --Bursts of MeV gamma-rays --From all directions, z~ Very energetic ~ erg --Rare: GRB rate ~ 10-6 /yr/galaxy -- Long (~30s) and short (~0.3s)

22 Merging NS/BH (or NS/NS?): Central Engine of Short GRBs Bloom et al GRB Elliptical z=0.2 Properties of host galaxies: Fong et al. 13

23 Merging NS/BH and NS/NS: Optical/IR Transients (?) Foucart et al. (Cornell-Caltech) Ejecta evolution: Initially mostly hot neutrons, decompression, r-process, beta decays heating Matzger, Quataert, etc.

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25 Pre-Merger Phase: Anything interesting?

26 Pre-Merger Phase: Non-magnetic Neutron Stars Tides -- Equilibrium tides -- Dynamical tides

27 Equilibrium Tide M M, R (Missing GW cycles) ==> Important only at small separation (just prior to merger) (Bildsten & Cutler 1992; Kochenek 92; DL, Rasio & Shaipro, etc) Numerical GR Quasi-equilibrium NS binary sequence (Baumgarte, Shapiro, Teukolsky, Shibata, Meudon group, etc. 1990s--200x) Recent (semi-analytic) GR calculation of tidal effect (Hinderer, Flanagan, Poisson, Damour, Penner, Andersson, Jones, etc., 2008+)

28 Dynamical Tides: Excitations of Internal Waves/Modes NS has low-frequency oscillation modes: g-modes (~100 Hz) (depends on symmetry energy) inertial modes (incl. r-modes), Resonance:

29 Dynamical Tides: Excitations of Internal Waves/Modes Rosonant tidal excitations of NS modes during inspiral transfer orbital energy to NS Missing GW cycles ==> Probe NS EOS using Inspiral Waveform

30 Resonant Excitations of NS Oscillations During Inspiral Non-rotating NS: G-mode (Reisenegger & Goldreich 94; Shibata 94; DL 94) Rotating NS: G-mode, F-mode, R-mode (Ho & DL 99) Inertial modes (DL & Wu 06) R-mode (excited by gravitomagnetic force; Racine & Flanagan 06) General Results: For R=10 km NS, the number of missing cycles < 0.1, bearly measurable (unless NS is rapidly rotating) Number of missing cycles Important for larger NS

31 Resonant Excitations of NS Oscillations During Inspiral Non-rotating NS: G-mode (Reisenegger & Goldreich 94; Shibata 94; DL 94) Rotating NS: G-mode, F-mode, R-mode (Ho & DL 99) Inertial modes (DL & Wu 06) R-mode (excited by gravitomagnetic force; Racine & Flanagan 06) New Results: G-modes: Systematic exploration of nuclear symmetry energy with existing N constraints can be ~ 1 (W. Newton & DL 2015) Crustal modes: -- Could shatter crust, pre-cursor of short GRB (Tsang et al. 12) -- Resonant excitation of spheroidal shear modes David Tsang Ph.D.10 Caltech McGill

32 Pre-Merger Phase: Magnetic NSs Cf. Double Pulsars: PSR J A,B pulsar A: ~10 10 G pulsar B: ~a few x10 12 G

33 Consider a binary with -- magnetic NS (>10 12 G) + non-magnetic NS -- embedded in a tenuous plasma (magnetosphere)

34 B

35 Flux tube Flux tube

36 DC Circuit Powered by Orbital Motion

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38 DC Circuit Powered by Orbital Motion Applications to: WD-WD Binaries (K.Wu et al. 02,09; Dall Osso, Israel, Stella 06,07 ) NS-NS, NS-BH Binaries (Hansen & Lyuitikov 01; McWilliams & Levin 11; Piro 12) Exoplanetary systems (Laine & Lin 12, ) Caution: Some of these were wrong

39 DC Circuit Powered by Orbital Motion Results depend on the resistance:

40 DC Circuit Powered by Orbital Motion Problems with small ( large ): Flux tube is twisted

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42 DC Circuit Powered by Orbital Motion Circuit will break when ~

43 Energy Dissipation in the Magnetosphere of Pre-merging NS Binary DL 2013 Actual dissipation rate: This Edot will not affect orbital decay rate (GW signal) Radio emission prior to binary merger (?) cf. Vietri 96; Hansen & Lyutikov 01 cf. isolated pulsars:

44 Energy Dissipation in the Magnetosphere of Pre-merging NS Binary Q: What happens if both NSs are magnetic? Ponce Lehner 2014

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46 Compact White Dwarf Binaries (mins - hour)

47 Compact White Dwarf Binaries (mins - hour) -- Dominant sources of gravitational waves ( Hz) Space interferometer (elisa-ngo??) -- Lead to various outcomes: R CrB stars, AM CVn binaries, transients If total mass ~ 1.4M sun : AIC => NS or SN Ia

48 Type Ia Supernovae

49 Type Ia Supernovae Thermonuclear explosion of CO white dwarfs of ~1.4M sun Progenitors?? WD + non-deg. star: Single-degenerate Scenario WD + WD merger: Double-degenerate Scenario WD + WD collision? Various arguments for/against each scenario: Rates, super-soft sources, delay time Recent observations in favor of DD: e.g., Absence of ex-companion stars in SN Ia remnant SNR ==> rule out V=26.9 Schaefer & Pagnotta 2012 (cf Di Stefano & Kilic 2012; Shen et al.13)

50 Radial Velocity Surveys of Compact WD Binaries Brown et al Brown et al. 2013

51 12 min orbital period double WD eclipsing binary SDSS J Primary & secondary eclipses Ellipsoidal (tidal) distortion Doppler boosting Brown et al will merge in 0.9 Myr -- large GW strain (elisa verification source) -- orbital decay measurable from eclipse timing (Hermes et al 2012) 20 min double WD binary WD (Kilic et al. 2014)

52 WD Binary Merger Dan, Rosswog,et al. 14

53 WD Binary Merger Transient sources

54 WD Binary Merger Dan, Rosswog,et al. 14 Outcome depends on WD masses, composition, and pre-merger conditions (rotation)

55 Dynamical Tides in Compact WD Binaries with Jim Fuller (Ph.D DuBridge Fellow, Caltech/KITP) Issues: -- Spin-orbit synchronization? -- Tidal dissipation and heating? -- Effect on orbital decay rate? (e.g. elisa) Fuller & DL

56 Equilibrium Tide M, R M Problems: -- Parameterized theory -- The physics of tidal dissipation is more complex: Excitation/damping of internal waves/modes (Dynamical Tides)

57 Wave Propagation inside White Dwarf N = Local Buoyancy Freq CO WD He-core WD

58 Continuous Excitation of Gravity Waves Waves are excited in the interior/envelope, propagate outwards and dissipate near surface

59 Continuous Excitation of Gravity Waves Waves are excited in the interior/envelope, propagate outwards and dissipate near surface

60 AA AA

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62 Spin-Orbit Synchronization 1 hour

63 Tidal Heating Rate

64 Consequences of Tidal Heating Depend on where the heat is deposited If deposited in shallow layer: thermal time short ==> change T eff Explain SDSS J If deposited in deeper layer: (common: critical layer ) thermal time longer than orbital ==> Nuclear flash * Tidal Nova

65 Merging NS and BH Binaries: Summary -- May be detected this decade by advanced LIGO/VIRGO -- Most severe test of gravity -- Probe NS EOS: Resonant excitations of modes -- EM counterparts: GRBs, Optical/IR detectable by LSST (?), pre-merger magnetic interactions precursors (??) Merging WD Binaries: -- Being detected in recent/ongoing surveys -- Produce various outcomes (e.g. SN Ia transient sources (PTF/ZTF, LSST) Pre-merger phase important/interesting: dynamical tides: Continuous excitations of waves, nonlinear breaking spin synchronization, tidal heating Tidal nova -- Low-frequency GWs (elisa?)

66 Thanks!

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68 Transient & Variable Universe Wide-field, fast imaging telescopes in optical: PTF, Pan-Starrs, LSST 26 PTF11agg iptf13dsw Relativistic Explosions Luminous Supernovae SCP06F iptf13bxl SN2005ap SN2006gy PTF10cwr SN2008esPTF09cnd PTF09cwl PTF09atu Peak Luminosity [M V ] SN2002bj Thermonuclear Supernovae SN2007bi PTF10bhp PTF12bho Core Collapse.Ia Explosions SN2007ke Supernovae PTF11bij PTF09dav PTF10xfh PTF11kmb SN2012hn PTF10iuv SN2005E Ca rich Transients SN2008ha SN2008S Intermediate PTF10acbp Luminosity NGC300OT Red Transients PTF10fqs Peak Luminosity [erg s 1 ] 10 8 P60 M81OT P60 M82OT Classical Novae Luminous Red Novae M85 OT V838 Mon M31 RV V1309 Sco Characteristic Timescale [day] Kasliwal 2014