Overview: Kilonova 1. Basics 2. Prospects for EM observa-ons 3. Signatures of r-process nucleosynthesis Masaomi Tanaka (Na-onal Astronomical Observatory of Japan) References (Reviews) • RosswoG, S. 2015 “The mul*-messenger picture of compact binary mergers” Interna*onal Journal of Modern Physics D, 24, 1530012-52 • Fernandez, R. & MetzGer, B. D. 2016 “Electromagne*c Signatures of Neutron Star Mergers in the Advanced LIGO Era” Annual Review of Nuclear and Par*cle Science, 66, 23 • Tanaka, M. 2016 “Kilonova/Macronova Emission from Compact Binary Mergers” Advances in Astronomy, 634197 • MetzGer, B. D. 2017 “Kilonovae” Living Reviews in Rela*vity, 20, 3 Timeline r-process Radioac-ve decay MerGer nucleosynthesis => kilonova Dynamical Wind < 10 ms ~< 100 ms < 1 sec ~ days energy deposi-on Diffusing out Masaru’s talk Francois’s talk My talk (Thursday) (Monday) (today) ν-driven winds from NS merger remnants 3145 5 Downloaded from http://mnras.oxfordjournals.org/ MerGer => see Masaru’s talkFigure 12. Vertical slices of the 3D domain (corresponding to the y 0 plane), recorded 20 ms after the beginning of the simulation. In the left-hand panel, 3 = we represent the logarithm of the matter density (in g cm− , left-hand side) and the projected fluid velocity (in units of c,ontheright-handside);thearrows indicate the direction of the projected velocity in the plane. On the right-hand panel, we represent the electron fraction (left-hand side) and the matter entropy 1 Dynamical ejecta (~< 10 ms)(in unit of kB baryon− ,right-handside). Post-dynamical ejecta (~< 100 ms) Side view at National Astronomical Observatory of Japan on January 1, 2016 Side view Top view Sekiguchi+16 Perego+14 Figure 13. Same as in Fig. 12,butat 40 ms after the beginning of the simulation. ≈ FIG. 2. Profiles of the electron number per baryon, Ye, (left in each panel) and the specific entropy, s, (right in each panel) in x-y (lower in-3 each panel)-2 and x-z (upper in each panel) planes. The top three panels-3 show the results for SFHo-135-135h 2 - Mej ~ 10The radial velocity - 10 in the wind increasesMsun from a few times 10− c, experiencing- Mej >~ 10 specific thermodynamicalMsun conditions inside the whole (left), SFHo-130-140h (middle), and SFHo-125-145h (right) at 13ms after the onset5 of the merger. The lower three panels showjust the above results the disc, for DD2-135-135h to a typical asymptotic (left), expansion DD2-130-140h velocity of (middle),system,⇡ and at DD2-125-145h a certain time. (right) at 10ms after the onset of the - v ~ 0.1-0.2 c 0.08–0.09 c. This acceleration is caused by the continuous pressure We- v ~ 0.05 c notice that most of the matter⇡ is extremely dense merger. - 11 3 gradient provided by newly expanding layersn + of matter.νe -> p + e (ρ > 10 gcm− ), neutron rich (Ye < 0.1) and, despite the - wide YeTo characterize the matter properties, we plot in+ Fig. 15 2D - rela-vely high Ye mass histograms for couples of quantities,n + e namely ρ– -> νY (top row),e + p e 2 binaries,ρ–s (central the typical row) and ejectaYe–s (bottom mass wouldrow), at approach three different 10 times− M 5 they estimated the properties of the ejecta at . 5 ms after A formal definition of the plotted quantity can be found in section of Bacca irrespective(t 0, 40, 85 of ms). the Colour EOS coded employed. is a measure We of note the amount that of the matter total et al.the (2012 onset). However, of the in this merger, work we do perhaps not calculate because the time average. of their small ejecta= mass depends only weakly on the grid resolution computational domain employed (L = 750 km). How- as listed in Table I. ever, the ejecta mass wouldMNRAS still443, 3134–3156 increase (2014) with time in such an early phase. This could be one of the reasons As shown in Fig. 1, the ejecta mass increases with time that our results for the ejecta mass are much larger than for the first 10 ms after the onset of the merger. This is ⇠ theirs. Figure 1 also shows that the average of Ye still in particular observed for the SFHo models with q & 0.9 significantly varies with time for the first 5 ms after and all the DD2 models. This indicates that we have to the onset of the merger. This also shows that⇠ it would follow the ejecta motion at least for 10 ms after the be necessary to determine the properties of the ejecta at onset of the merger. In a recent simulation⇡ of Ref. [13], Nucleosynthesis (< 1 sec) => see Francois’s talk d p s f Se Ru Te Nd Er 100 Ye = 0.30 Ye = 0.25 Ye = 0.10-0.40 10-1 10-2 10-3 Mass fraction 10-4 10-5 30 40 50 60 70 80 90 100 Atomic number => Solar abundance? (Discussion yesterday) (from Wanajo+14) Radioac-ve hea-nG (decay of many r-process nuclei)Transients from compact object mergers 2653 3RADIOACTIVEHEATING 3.1 Network calculations NS merGer In this section we present calculations of the radioactive heating of ~ t -1.3 1 hr 1 day 10 days the ejecta. We use a dynamical r-process network (Mart´ınez-Pinedo 2008; Petermann et al. 2008) that includes neutron captures, pho- todissociations, β-decays, α-decays and fission reactions.10 The43 erg s latter-1 includes contributions from neutron-induced fission, β delayed fis- supernova sion and spontaneous fission. The neutron capture rates for nuclei with Z 83 are obtained from the work of Rauscher & Thielemann1040 erg s-1 (2000)≤ and are based on two different nuclear mass models: the Finite Range Droplet Model (FRDM; Moller¨ et al. 1995) and the Quenched version of the Extended Thomas–Fermi with Strutinsky Integral (ETFSI-Q) model (Pearson, Nayak & Goriely 1996). For nuclei with Z > 83 the neutron capture rates and neutron-induced fission rates are obtained from Panov et al. (2010). β-decay rates ˙ including emission of up to three neutrons after β-decay(for M = 0.01 are from ΜFiguresun) 1. Radioactive heating rate per unit mass E in NS mergerMetzger+10 ejecta due to the decay of r-process material, calculated for the Ye 0.1 ejecta Moller,¨ Pfeiffer & Kratz (2003). β-delayed fission and spontaneous = trajectory from Rosswog et al. (1999) and Freiburghaus et al. (1999). The fission rates are determined as explained by Mart´ınez-Pinedo et al. total heating rate is shown with a solid line and is divided into contributions (2007). Experimental rates for α and β decay have been obtained from β-decays (dotted line) and fission (dashed line). For comparison we 1 from the NUDAT data base. Fission yields for all fission processes also show the heating rate per unit mass produced by the decay chain are determined using the statistical code ABLA (Gaimard & Schmidt 56Ni 56Co 56Fe (dot–dashed line). Note that on the day time-scales → → ∼ 1991; Benlliure et al. 1998). All heating is self-consistently added of interest for merger transients (t tpeak;equation3)fissionandβ-decays ∼ to the entropy of the fluid following the procedure of Freiburghaus make similar contributions to the total r-process heating, and that the r- et al. (1999). The change of temperature during the initial expan- process and 56Ni heating rates are similar. sion is determined using the Timmes equation of state (Timmes & 11 3 Table 1. Properties of the dominant β-decay nuclei at t 1d. Arnett 1999), which is valid below the density ρ 3 10 gcm− ∼ × ∼ at which our calculation begins. a b c d avg e As in the r-process calculations performed by Freiburghaus et al. Isotope t1/2 Q ϵe ϵν ϵγ Eγ (h) (MeV) (MeV) (1999), we use a Lagrangian density ρ(t) taken from the NS–NS merger simulations of Rosswog et al. (1999). In addition to ρ(t), the 135I6.572.650.180.180.641.17 initial temperature T,electronfractionYe and seed nuclei properties 129Sb 4.4 2.38 0.22 0.22 0.55 0.86 (A,¯ Z¯ )arespecifiedforagivencalculation.Weassumeaninitial 128Sb 9.0 4.39 0.14 0.14 0.73 0.66 temperature T 6 109 K, although the subsequent r-process heat- 129Te 1.16 1.47 0.48 0.48 0.04 0.22 ing is not particularly= × sensitive to this choice because any initial ther- 132I2.303.580.190.190.620.77 mal energy is rapidly lost to P dV work during the initial expansion 135Xe 9.14 1.15 0.38 0.40 0.22 0.26 127 before the r-process begins (Meyer 1989; Freiburghaus et al. 1999). Sn 2.1 3.2 0.24 0.23 0.53 0.92 134 For our fiducial model we also assume Y 0.1, Z¯ 36, A¯ 118 I 0.88 4.2 0.20 0.19 0.61 0.86 e 56Nif 146 2.14 0.10 0.10 0.80 0.53 (e.g. Freiburghaus et al. 1999). = ≃ ≃ Our results for the total radioactive power E˙ with time are shown aTotal energy released in the decay. in Fig. 1. On time-scales of interest the radioactive power can be b,c,dFraction of the decay energy released in electrons, neutrinos and γ -rays. e divided into two contributions: fission and β-decays, which are Average photon energy produced in the decay. f 56 denoted by dashed and dotted lines, respectively. The large heating Note: Ni is not produced by the r-process and is only shown for compar- ison [although a small abundance of 56Ni may be produced in accretion disc rate at very early times is due to the r-process, which ends when 5 outflows from NS–NS/NS–BH mergers (Metzger et al.