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

Electromagnetic Counterparts of NS-NS/NS-BH Mergers Importance of EM Detection: Improve Effective Sensitivity of G-Wave Detectors (e.g. Kochanek & Piran 93) Cosmology: Redshift  Measurement of H 0 (e.g. Krolak & Schutz 87; Nissanke+ 10)  Astrophysical Context (e.g. Identify Host Galaxy & Environment)  Improve Effective Sensitivity of G-Wave Detectors (e.g. Kochanek & Piran 93)  Cosmology: Redshift  Measurement of H 0 (e.g. Krolak & Schutz 87; Nissanke+ 10)

Importance of EM Detection: Electromagnetic Counterparts of NS-NS/NS-BH Mergers Four “Cardinal Virtues” of a Promising Counterpart (Metzger & Berger 2011) 1) 1)Detectable with present or upcoming facilities (given a reasonable allocation of resources). 2) 2)Accompany a high fraction of GW events. 3) 3)Be unambiguously identifiable (a “smoking gun”). 4) 4)Allow for determination of an accurate ~arcsecond sky localization. (see talk by S. Nissanke) Short GRB “Kilonova” Improve Effective Sensitivity of G-Wave Detectors (e.g. Kochanek & Piran 93) Cosmology: Redshift  Measurement of H 0 (e.g. Krolak & Schutz 87; Nissanke+ 10)  Astrophysical Context (e.g. Identify Host Galaxy & Environment)  Improve Effective Sensitivity of G-Wave Detectors (e.g. Kochanek & Piran 93)  Cosmology: Redshift  Measurement of H 0 (e.g. Krolak & Schutz 87; Nissanke+ 10)

Importance of EM Detection: Electromagnetic Counterparts of NS-NS/NS-BH Mergers Four “Cardinal Virtues” of a Promising Counterpart (Metzger & Berger 2011) 1) 1)Detectable with present or upcoming facilities (given a reasonable allocation of resources). 2) 2)Accompany a high fraction of GW events. 3) 3)Be unambiguously identifiable (a “smoking gun”). 4) 4)Allow for determination of an accurate ~arcsecond sky localization. (see talk by S. Nissanke) Short GRB “Kilonova” Improve Effective Sensitivity of G-Wave Detectors (e.g. Kochanek & Piran 93) Cosmology: Redshift  Measurement of H 0 (e.g. Krolak & Schutz 87; Nissanke+ 10)  Astrophysical Context (e.g. Identify Host Galaxy & Environment)  Improve Effective Sensitivity of G-Wave Detectors (e.g. Kochanek & Piran 93)  Cosmology: Redshift  Measurement of H 0 (e.g. Krolak & Schutz 87; Nissanke+ 10)

Credit: M. Shibata (U Tokyo)

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

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

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

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

Off Axis Radio Emission? (Nakar & Piran 2011; see talk by Kaplan) 100 pointings + 30 hrs EVLA  Metzger & Berger 2011 Detection requires F F detect ~ 0.5 mJy at 1 GHz  Sky error region ~ tens degrees Sky error region ~ tens degrees 2  jjjj  obs No observed afterglows detectable!!! Metzger & Berger 2011

Importance of EM Detection: Improve Effective Sensitivity of G-Wave Detectors (Kochanek & Piran 93) Cosmology: Redshift  Measurement of H 0 (e.g. Krolak & Schutz 87)  Astrophysical Context (e.g. Identify Host Galaxy & Environment)  Improve Effective Sensitivity of G-Wave Detectors (Kochanek & Piran 93)  Cosmology: Redshift  Measurement of H 0 (e.g. Krolak & Schutz 87) Electromagnetic Counterparts of NS-NS/NS-BH Mergers Four “Cardinal Virtues” of a Promising Counterpart (Metzger & Berger 2011) 1) 1)Detectable with present or upcoming facilities (given a reasonable allocation of resources). 2) 2)Accompany a high fraction of GW events. 3) 3)Be unambiguously identifiable (a “smoking gun”). 4) 4)Allow for determination of an accurate ~arcsecond sky localization. Short GRB “Kilonova”

Sources of Neutron-Rich Ejecta Tidal Tails (Dynamical Ejecta) (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) Rosswog 2005 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) Thermonuclear-Driven Winds (Late) (Metzger, Piro & Quataert 2008; Lee et al. 2009) M ej ~ M 

“mini- supernova” } Sources of Neutron-Rich Ejecta Tidal Tails (Dynamical Ejecta) (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) Rosswog 2005 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) Thermonuclear-Driven Winds (Late) (Metzger, Piro & Quataert 2008; Lee et al. 2009) M ej ~ M 

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

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

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

GRB : Candidate Kilonova (Perley, BDM et al. 2009) Best-Fit Kilonova Parameters: v ~ 0.1 c, M ej ~ few M , z ~ 0.1 z = Where’s the Host Galaxy? Optical Rebrightenin t ~ 1 day

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 E jet /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!

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