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Gabriel Martínez-Pinedo Kilonova Kilonova: An electromagnetic signal of heavy element nucleosynthesis Gabriel Martínez-Pinedo Colloquia Severo Ochoa, IFIC, Valencia, May 10, 2018 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Signatures of nucleosynthesis Neutron capture processes: s process r process • Heavy elements produced in neutron capture processes • r process operates at early Galactic history Metal-poor stars observations 2 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Implications from observations Individual stars, Milky Way Halo Sneden, Cowan & Gallino, 2008 Ji et al 2016 found that only 1 of 10 ultrafaint dwarf galaxies is enriched in r-process elements R process related to rare high yield events not correlated with Iron enrichment Similar results obtained by 60Fe and 244Pu observations in deep sea sediments (Wallner et al, 2015; Hotokezaka et al, 2015) 3 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process R process nuclear needs Astrophysical environment should provide enough neutrons per seed for the r process to operate 퐴final = 퐴initial + 푛seed nseed depends mainly on neutron richness ejecta requires properties of exotic neutron-rich nuclei: • Nuclear masses • Beta-decay rates • Neutron capture rates • Fission rates and yields 4 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Astrophysical sites Core-collapse supernova Compact binary mergers Stephan Rosswog 푌푒 Supernova Mergers Optimal conditions Yield / Frequency Direct signature 5 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Supernova nucleosynthesis Heavy elements produced in neutrino winds from protoneutron star cooling. Neutrino interactions determine proton- to-nucleon ratio, 푌푒 − 휈푒 + 푛 ⇄ 푝 + 푒 + 휈푒 + 푝 ⇄ 푛 + 푒 Supernova produce only medium mass nuclei GMP, et al., JPG 41, 044008 (2014) 6 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Nucleosynthesis dependence on 풀풆 Nucleosynthesis mainly sensitive to proton-to-nucleon ratio, 푌푒 − + 휈푒 + 푛 ⇄ 푝 + 푒 vs 휈푒 + 푝 ⇄ 푛 + 푒 푌푒 ≳ 0.25 푌푒 ≈ 0.15−0.25 푌푒 ≲ 0.15 Lanthanides Actinides 7 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Mergers: variety of ejecta Two main sources of ejecta: • Dynamical ejecta (M < 0.01 M⊙) • Accretion disk ejecta (M < 0.1 M⊙) Depend on merger system, relative mass ratio and equation of state S. Rosswog, et al, Class. Quantum Gravity 34, 104001 (2017). 8 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Neutron rich ejecta BH-NS ejecta and NS-NS ejecta in the equatorial plane is very neutron rich 9 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Dependence on nuclear masses Mendoza-Temis, et al, PRC 92, 055805 (2015) • Robustness astrophysical conditions, sensitive nuclear physics • Second peak (A ~ 120) sensitive to fission yields • Third peak (A ~ 195) sensitive to masses and half-lives • Elements lighter than A ~ 120 are not produced 10 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Impact beta-decay half-lives • Beta-decay half-lives determine the speed at which heavy elements are build starting from light ones • Theoretical advances allow for fully microscopic calculations Zhi et al, PRC 87, 024803 (2013) Marketin, …, GMP, PRC 93, 25805 (2016) • Microscopic calculations reproduce available data • Predict shorter half-lives for nuclei 푍 > 80 having a strong impact on the position of the A ~ 195 peak [Eichler et al, ApJ 808, 30 (2015)] 11 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Impact of neutrinos on NS-NS mergers Prompt collapse BH Delayed collapse BH , 2016 al, et 푅1.40 = 11.9 km 푅1.40 = 13.2 km Sekiguchi 7 Shibata, 201 al, et Shibata, 12 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Nucleosynthesis delayed BH case An HyperMassive Neutron Star produces large neutrino fluxes that drive the nucleosynthesis to light elements Perego, et al, MNRAS 443, 3134 (2014) Martin, et al, ApJ 813, 2 (2015) No Lanthanides are produced 13 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Nucleosynthesis after BH formation • Accretion disk around BH ejects relatively neutron rich matter [Fernández & Metzger, MNRAS 435, 502 (2013)] • Produces all r-process nuclides (Lanthanide rich ejecta) [Wu et al, MNRAS 463, 2323 (2016)] See also Just et al, MNRAS 448, 541 (2015), Siegel and Metzger PRL 119, 231102 (2017). 14 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Electromagnetic signatures of nucleosynthesis Supernova light curves follow the 56 decay of Ni (푡1/2 = 6 d) and later 56 Co (푡1/2 = 77 d) Diehl & Timmes, PASP 110, 637 (1998) 15 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Radioactive heating from r process ejecta For the r process a broad distribution of nuclei decay producing energy as (Way & Wigner 1948, Metzger et al 2010) 휀 ~푡−훼, 훼 ≈ 1.3 Heating sensitive to (Barnes et al, 2016): • Total energy produced: depends on decay mode (beta, alpha, fission) • Thermalization efficiency: depends also on decay and particle. 16 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Kilonova: Electromagnetic signature of the r process • Ejecta produces electromagnetic signatures [Li & Paczyński 1998] • Transient due to radioactive decay of r-process nuclei [Metzger et al, 2010] Heating: 휀 ~ 푡−1.3 Luminosity like 1000 novas: Kilonova Peak on timescales days in optical/blue • Presence of Lanthanides reduces luminosity and delays peak to ~ week in red/infrared [Barnes & Kasen, 2013] • Similar effect due to Actinides [Mendoza- Temis et al, 2015] • Accurate treatment of thermalization of radioactive products [Barnes, et al, 2016] Metzger, GMP, Darbha, Quataert, Arcones et al, MNRAS 406, 2650 (2010) 17 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Simple Kilonova model Light curve is expected to peak when photon diffusion time is comparable to elapsed time (Metzger et al 2010, Kasen et al 2017) 휌휅푅2 푀 푡 = , 휌 = , 푅 = 푣푡 diff 푐 4휋푅3 3 1 1 1 1 3휅푀 2 푀 2 푣 −2 휅 2 푡peak ≈ ≈ 2.7 days 2 −1 4휋푐푣 0.01 푀⊙ 0.01푐 1 cm g −훼 푡 The Luminosity is 퐿 푡 ≈ 푀 휀 푡 , 휀 푡 ≈ 1010 erg s−1 g−1 1 day 훼 훼 훼 1−2 −2 40 −1 푀 푣 2 휅 퐿peak ≈ 5 × 10 erg s 2 −1 0.01 푀⊙ 0.01푐 1 cm g Very sensitive to atomic opacity 휅 ≈ 1 cm2 g−1 , light r process material (blue emission) 휅 ≈ 10 cm2 g−1 , heavy (lanthanide/actinide rich) r process (red emis.) 18 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process GW170817: First detection gravitational waves from NS merger On August 17, 12:41:04 UTC advanced LIGO and Virgo detect the first GW signal from a binary neutron star inspiral Abbott, et al, PRL 119, 161101 (2017). 3/5 푚1푚2 +0.004 Frequency growth determined by chirp mass ℳ = 1/5 = 1.188−0.002 M⊙ 푚1+푚2 5∕3 96 퐺ℳ 3 휋8∕3 푡 + 푓−8∕3 + 퐶 = 0 5 푐3 8 19 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process GW170817: Individual masses Individual masses depend on assumed spin parameter 휒 = 푐 퐽 ∕ (퐺푀2) For the low spin case masses are very well constrained +0.04 Total mass: 푀 = 2.74−0.01 M⊙, 푞 = 푚2 푚1 = 0.7 − 1.0 Primary mass: 푚1 ∈ 1.36−1.60 M⊙ Secondary mass: 푚2 ∈ 1.17−1.36 M⊙ +8 Abbott, et al, PRL 119, 161101 (2017). Distance: 40−14 Mpc 20 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process GW170817: A big reveal from the cosmos . 1.7 s later Fermi and INTEGRAL detected the short GRB 170817 A . Despite being the closest SGRB is 2-6 order of magnitude weaker than typical SGRBs. Explained assuming jet forms ~ 30° with line of view. Combined analysis favors formation BH on timescales ≲ 100 ms. 30° B. P. Abbott, et al, Astrophys. J. 848, L13 (2017). 21 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Optical transient identified Kilonova identified 10.9 hours after the merger in the Galaxy NGC 4993 near the constellation of Hydra (Southern hemisphere) 22 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Kilonova: An electromagnetic signal of r-process nucleosynthesis Metzger, GMP, …, AA et al, 2010 predictions Cowperthwaite, et al 2017 Kilonova observations . Time evolution determined by the radioactive decay of r-process nuclei . Two components: . blue dominated by light elements (Z < 50) . Red due to presence of lanthanides (Z = 57-71) and/or Actinides (Z = 89-103) . Likely source of heavy elements including Gold, Platinum and Uranium 23 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Light curve and spectra evolution ESO/E. Pian/S. Smartt & ePESSTO/N. Tanvir/VIN-ROUGE, Pian et al, Nature 551, 67, 2017 24 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Two components model Kasen et al, Nature 551, 80 (2017) • Blue component from polar ejecta subject to strong neutrino fluxes (light r process) −4 푀 = 0.025 푀⊙, 푣 = 0.3푐, 푋lan = 10 • Red component disk ejecta after NS collapse to a black hole (light and heavy r process) −1.5 푀 = 0.04 푀⊙, 푣 = 0.15푐, 푋lan = 10 25 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Unified scenario EM counterparts orphan X-ray, radio afterglow t ~ 2 weeks Al Cameron Γ >>1 0.02 M⊙ GRB jet t ~ day light Blue KN r-nuclei t ~ week v ~ 0.25 c NS NS disk winds Red KN HMNS heavy v ~ 0.1 c r-nuclei BH 0.04 M⊙ Sketch from B. Metzger 26 G. Martínez-Pinedo / Kilonova: Electromagnetic signature of the r process Are NS mergers the r process site? Rate of mergers times ejected mass should account for r process material in the Galaxy ℛ 푀푒푗 = ℳ푟,퐺푎푙 ℳ푟,퐺푎푙 ≈ 19000 푀⊙ Rosswog, arXiv:1710.05445 Cote et al, ApJ 855, 99 (2018) LIGO/Virgo NS merger rate requires that mergers produce the whole inventory of r-process elements 27 G.
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