Edo Berger (Harvard CfA) Eliot Quataert, Siva Darbha, Dan Kasen, & Daniel Perley (UC Berkeley)

1. EM Counterparts of Neutron Star Binary Mergers and their Detection in the Era of Advanced LIGO Brian Metzger Princeton University NASA Einstein Fellow In Collaboration with: Edo Berger (Harvard CfA) Eliot Quataert, Siva Darbha, Dan Kasen, & Daniel Perley (UC Berkeley) Almudena Arcones (U Basel) & Gabriel Martinez-Pinedo (GSI, Darmstadt) LIGO Open Data Workshop, Livingston, LA, October 27, 2011

2. Electromagnetic Counterparts of NS-NS/NS-BH Mergers Importance of EM Detection:  Astrophysical Context(e.g. Identify Host Galaxy & Environment)  Improve Effective Sensitivity of G-Wave Detectors(e.g. Kochanek & Piran 93)  Cosmology: Redshift  Measurement of H0(e.g. Krolak & Schutz 87; Nissanke+ 10)

3. Electromagnetic Counterparts of NS-NS/NS-BH Mergers Importance of EM Detection:  Astrophysical Context(e.g. Identify Host Galaxy & Environment)  Improve Effective Sensitivity of G-Wave Detectors(e.g. Kochanek & Piran 93)  Cosmology: Redshift  Measurement of H0(e.g. Krolak & Schutz 87; Nissanke+ 10) Four “Cardinal Virtues” of a Promising Counterpart(Metzger & Berger 2011) “Kilonova” Detectable with present or upcoming facilities (given a reasonable allocation of resources). Accompany a high fraction of GW events. Be unambiguously identifiable (a “smoking gun”). Allow for determination of an accurate ~arcsecond sky localization. (see talk by S. Nissanke) Short GRB

4. Electromagnetic Counterparts of NS-NS/NS-BH Mergers Importance of EM Detection:  Astrophysical Context(e.g. Identify Host Galaxy & Environment)  Improve Effective Sensitivity of G-Wave Detectors(e.g. Kochanek & Piran 93)  Cosmology: Redshift  Measurement of H0(e.g. Krolak & Schutz 87; Nissanke+ 10) Four “Cardinal Virtues” of a Promising Counterpart(Metzger & Berger 2011) “Kilonova” Detectable with present or upcoming facilities (given a reasonable allocation of resources). Accompany a high fraction of GW events. Be unambiguously identifiable (a “smoking gun”). Allow for determination of an accurate ~arcsecond sky localization. (see talk by S. Nissanke) Short GRB

5. Credit: M. Shibata (U Tokyo)

6. Short Gamma-Ray Burst (obs < j) (e.g. Eichler et al. 1989; Narayan et al. 1992; Aloy et al. 2005; Rezzolla et al. 2011) j Swift SGRBs Detection Rate >z (yr -1) Metzger & Berger 2011 Redshift z !!! Detection fraction by all sky -ray telescope Accretion Rate

7. On Axis Optical Afterglow (obs < j) • - Detections  - Upper Limits • - Detections  - Upper Limits obs j see Berger (2010) Metzger & Berger 2011 Afterglow models for different jet energy Ej and ISM density n (from van Eerten & MacFadyen 2011) On axis detections constrain jet energy and circumburst density:

8. Off Axis Afterglow (obs = 2j) peak timescale ~ day-weeks j obs Afterglow models for different jet energy Ej and ISM density n (from van Eerten & MacFadyen 2011) Detection fraction: need “LSST” for multiple detections 

9. Far Off Axis Afterglow (obs = 4j) obs j Afterglow models for different jet energy Ej and ISM density n (from van Eerten & MacFadyen 2011)

10. No observed afterglows detectable!!! Off Axis Radio Emission? (Nakar & Piran 2011; see talk by Kaplan) obs j Metzger & Berger 2011 Metzger & Berger 2011 Detection requires Sky error region ~ tens degrees2 Fdetect ~ 0.5 mJy at 1 GHz 100 pointings + 30 hrs EVLA   

11. Electromagnetic Counterparts of NS-NS/NS-BH Mergers Importance of EM Detection:  Astrophysical Context(e.g. Identify Host Galaxy & Environment)  Improve Effective Sensitivity of G-Wave Detectors(Kochanek & Piran 93)  Cosmology: Redshift  Measurement of H0(e.g. Krolak & Schutz 87) Four “Cardinal Virtues” of a Promising Counterpart(Metzger & Berger 2011) “Kilonova” Detectable with present or upcoming facilities (given a reasonable allocation of resources). Accompany a high fraction of GW events. Be unambiguously identifiable (a “smoking gun”). Allow for determination of an accurate ~arcsecond sky localization. Short GRB

12. Sources of Neutron-Rich Ejecta Tidal Tails (Dynamical Ejecta) Rosswog 2005 (e.g. Janka et al. 1999; Lee & Kluzniak 1999; Ruffert & Janka 2001; Rosswog et al. 2004; Rosswog 2005; Shibata & Taniguchi 2006; Giacomazzo et al. 2009; Rezzolla et al. 2010) Accretion Disk Outflows Neutrino-Driven Winds (Early)(McLaughlin & Surman 05; BDM+08; Dessart et al. 2009) Thermonuclear-Driven Winds (Late) (Metzger, Piro & Quataert 2008; Lee et al. 2009) Mej ~ 10-3 - 10-1 M

13. Sources of Neutron-Rich Ejecta Tidal Tails (Dynamical Ejecta) Rosswog 2005 (e.g. Janka et al. 1999; Lee & Kluzniak 1999; Ruffert & Janka 2001; Rosswog et al. 2004; Rosswog 2005; Shibata & Taniguchi 2006; Giacomazzo et al. 2009; Rezzolla et al. 2010) Accretion Disk Outflows Neutrino-Driven Winds (Early)(McLaughlin & Surman 05; BDM+08; Dessart et al. 2009) Thermonuclear-Driven Winds (Late) (Metzger, Piro & Quataert 2008; Lee et al. 2009) Mej ~ 10-3 - 10-1 M } “mini-supernova”

14. Radioactive Heating of NS Merger Ejecta R-Process Network (Martinez-Pinedo 2008) • neutron captures (Rauscher & Thielemann 2000) • photo-dissociations • - and -decays • fission reactions (Panov et al. 2009). 3rd BDM et al. 2010 2nd Nucleosynthesis Calculations by G. Martinez-Pinedo & A. Arcones Ye = 0.1 @ t ~ 1 day : Ye = 0.1 • R-process & Ni heating similar • ~1/2 Fission, ~1/2 -Decays • Dominant -Decays:132,134,135 I, 128,129Sb,129Te,135Xe  t-1.2 fLP = 3 x 10-6

15. Light Curves Color Evolution Bolometric Luminosity “kilo-nova” Blackbody Model Metzger et al. 2010 Monte Carlo Radiative Transfer (SEDONA; Kasen et al. 2006) Peak Brightness MV= -15 @ t ~ 1 day for Mej = 10-2 M CAVEAT: Fe composition assumed for opacity What does a pure r-process photosphere look like?

16. Far Off Axis (obs = 4j) - The Kilonova is Isotropic obs j Range of kilonova models w different ejecta mass Mej ~10-3 - 0.1Mand velocity v ~ 0.1-0.3 c  Detection requires depth r ~ 22-24 and cadence <~ 1 day (standard LSST 4-day survey not sufficient)

17. GRB 080503: Candidate Kilonova(Perley, BDM et al. 2009) Optical Rebrightening @ t ~ 1 day Where’s the Host Galaxy? z = 0.561 Best-Fit Kilonova Parameters: v ~ 0.1 c, Mej ~ few 10-2 M , z ~ 0.1

18. Conclusions • Direct detection of gravitational waves is expected within the next >~5 years, but maximizing the science return requires identifying and localizing an EM counterpart. • Short GRBs are detectable & identifiable, but are limited to <~ 1 detection yr-1 and may not provide localization. These rare detections are nevertheless crucial, so an operational -ray satellite similar to Fermi GBM is important. • No optical or radio facilities can provide all-sky coverage at a cadence and depth matched to the expected counterpart light curves  targeted follow-up is required. • Optical afterglow emission is easily detectable for on-axis events with rapid follow-up. However, off-axis optical afterglows are only detectable for obs < 2 j (even with LSST) and hence are limited to <~ 10% of all mergers. • Radio afterglow emission is isotropic, but existing and planned are not sufficiently sensitive, given the low Ejet/n from existing SGRB afterglows. • Isotropic kilonovae are in principle detectable for most events, but require a follow-up telescope with sensitivity similar to Pan-STARRs/LSST and a short cadence. This is going to be hard, so we need to start planning now!

20. Gamma-Ray Burst “Afterglows” - Synchrotron Emission from Shock Interaction with the Circumburst Medium Zhang & MacFadyen 2009