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 EM Counterparts of Neutron Star Binary Mergers and their Detection in the Era of Mergers and their Detection in the Era of

Advanced LIGOAdvanced LIGO

In Collaboration with:In Collaboration with:

Princeton University NASA Einstein Fellow

LIGO Open Data Workshop, Livingston, LA, October 27, LIGO Open Data Workshop, Livingston, LA, October 27, 20112011

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 DetectorsImprove Effective Sensitivity of G-Wave Detectors (e.g. Kochanek & Piran 93) (e.g. Kochanek & Piran 93)

Cosmology: Redshift Cosmology: Redshift Measurement of H Measurement of H00 (e.g. Krolak & Schutz 87; (e.g. Krolak & Schutz 87;

Nissanke+ 10)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) Detectable with present or upcoming facilities (given a reasonable allocation of resources).

2) Accompany a high fraction of GW events.

3) Be unambiguously identifiable (a “smoking gun”).

4) Allow for determination of an accurate ~arcsecond sky localization. (see talk by S. Nissanke)

Short GRB

“Kilonova”

Astrophysical Context (e.g. Identify Host Galaxy & Environment)

Improve Effective Sensitivity of G-Wave DetectorsImprove Effective Sensitivity of G-Wave Detectors (e.g. Kochanek & Piran 93) (e.g. Kochanek & Piran 93)

Cosmology: Redshift Cosmology: Redshift Measurement of H Measurement of H00 (e.g. Krolak & Schutz 87; (e.g. Krolak & Schutz 87;

Nissanke+ 10)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) Detectable with present or upcoming facilities (given a reasonable allocation of resources).

2) Accompany a high fraction of GW events.

3) Be unambiguously identifiable (a “smoking gun”).

4) Allow for determination of an accurate ~arcsecond sky localization. (see talk by S. Nissanke)

Short GRB

“Kilonova”

Astrophysical Context (e.g. Identify Host Galaxy & Environment)

Improve Effective Sensitivity of G-Wave DetectorsImprove Effective Sensitivity of G-Wave Detectors (e.g. Kochanek & Piran 93) (e.g. Kochanek & Piran 93)

Cosmology: Redshift Cosmology: Redshift Measurement of H Measurement of H00 (e.g. Krolak & Schutz 87; (e.g. Krolak & Schutz 87;

Nissanke+ 10)Nissanke+ 10)

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Short Gamma-Ray Burst (obsobs < jj ) (e.g. Eichler et al. 1989; Narayan et al. 1992; Aloy et al.

2005; Rezzolla et al. 2011)

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˙ M ~ 10−2 −10M8 s-1Accretion RateAccretion Rate

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Detection fraction by all sky -ray telescope

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Swift SGRBs

On Axis Optical Afterglow (obsobs < jj )

jjobs

- Detections

- Upper Limits

On axis detections constrain jet energy and

circumburst density:

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E j

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Afterglow models for different jet energy Ej and ISM density n (from van Eerten & MacFadyen 2011)

- Detections

- Upper Limits

Metzger & Berger 2011

see Berger (2010)

Off Axis Afterglow (obsobs = 2jj )

jj obs

Afterglow models for different jet energy Ej and ISM density n (from van Eerten & MacFadyen 2011)

Detection fraction:

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fopt < 3.4 ×(2θ j)

2

2 ~ 0.25 θ j0.2

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peak timescale ~ day-weekspeak timescale ~ day-weeks

need “LSST” for multiple detections

Far Off Axis Afterglow (obsobs = 4jj )

jjobs

Afterglow models for different jet energy Ej and ISM density n (from van Eerten & MacFadyen 2011)

Off Axis Radio Emission? (Nakar & Piran 2011; see talk by Kaplan)

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Sky error Sky error

region ~ tens region ~ tens degreesdegrees2

jj

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No observed afterglows detectable!!!No observed afterglows detectable!!!

Metzge

r & B

erger 2011

Importance of EM Detection: Astrophysical Context (e.g. Identify Host Galaxy & Environment)

Improve Effective Sensitivity of G-Wave DetectorsImprove Effective Sensitivity of G-Wave Detectors (Kochanek & Piran 93) (Kochanek & Piran 93)

Cosmology: Redshift Cosmology: Redshift Measurement of H Measurement of H00 (e.g. Krolak & Schutz 87)(e.g. Krolak & Schutz 87)

Electromagnetic Counterparts of NS-NS/NS-BH Mergers

Four “Cardinal Virtues” of a Promising Counterpart (Metzger & Berger 2011)

1) Detectable with present or upcoming facilities (given a reasonable allocation of resources).

2) Accompany a high fraction of GW events.

3) Be unambiguously identifiable (a “smoking gun”).

4) Allow for determination of an accurate ~arcsecond sky localization.

Short GRB

“Kilonova”

Sources of Neutron-Rich Ejecta

Tidal Tails (Dynamical Tidal Tails (Dynamical Ejecta)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)

Rossw

og

20

05

Accretion Disk OutflowsAccretion Disk Outflows Neutrino-Driven Winds (Early) (McLaughlin & Surman 05; BDM+08; Dessart et al. 2009)

Thermonuclear-Driven Winds (Late) Thermonuclear-Driven Winds (Late) (Metzger, Piro & Quataert 2008; Lee et al. 2009)(Metzger, Piro & Quataert 2008; Lee et al. 2009)

Mej ~ 10-3 - 10-1 M

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Lpeak

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tpeak““mini-mini-supernova”supernova”}

Sources of Neutron-Rich Ejecta

Tidal Tails (Dynamical Tidal Tails (Dynamical Ejecta)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)

Rossw

og

20

05

Accretion Disk OutflowsAccretion Disk Outflows Neutrino-Driven Winds (Early) (McLaughlin & Surman 05; BDM+08; Dessart et al. 2009)

Thermonuclear-Driven Winds (Late) Thermonuclear-Driven Winds (Late) (Metzger, Piro & Quataert 2008; Lee et al. 2009)(Metzger, Piro & Quataert 2008; Lee et al. 2009)

Mej ~ 10-3 - 10-1 M

Radioactive Heating of NS Merger Radioactive Heating of NS Merger EjectaEjecta

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• R-process & Ni heating similar

• ~1/2 Fission, ~1/2 -Decays

• Dominant -Decays: 132,134,135

I, 128,129Sb,129Te,135Xe

YYee = 0.1 = 0.1

tt-1.2-1.2

YYee = 0.1 = 0.1

fLP = 3 x 10-6

R-Process Network (Martinez-Pinedo 2008)

• neutron captures (Rauscher & Thielemann 2000)

• photo-dissociations

• - and -decays

• fission reactions (Panov et al. 2009).

2nd

3rd

BD

M e

t al. 2

01

0

Light Curves

Blackbody Model

Bolometric LuminosityColor EvolutionColor Evolution

Peak Brightness MPeak Brightness MVV= -15 @ t ~ 1 day for M= -15 @ t ~ 1 day for Mejej = 10 = 10-2-2 M M

Monte Carlo Radiative Transfer Monte Carlo Radiative Transfer (SEDONA; Kasen et al. 2006)(SEDONA; Kasen et al. 2006)

CAVEAT: Fe composition assumed for opacity CAVEAT: Fe composition assumed for opacity

What What doesdoes a pure r-process photosphere look like? a pure r-process photosphere look like?

““kilo-nova”kilo-nova”

Metzg

er et al. 2010

Far Off Axis (obsobs = 4jj ) - The Kilonova is Isotropic

jjobs

Range of kilonova models w different ejecta mass Mej ~10-3 - 0.1 M 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)

GRB 080503: Candidate Kilonova

(Perley, BDM et al. 2009)

Best-Fit Kilonova Parameters: v ~ 0.1 c, Mej ~ few 10-2 M , z ~ 0.1

z = 0.561z = 0.561

Where’s the Host Where’s the Host Galaxy?Galaxy?

Optical Rebrightening @ t ~ 1 day

ConclusionsConclusions Direct detection of gravitational waves is expected within the next Direct detection of gravitational waves is expected within the next >~5 years, but maximizing the science return requires identifying >~5 years, but maximizing the science return requires identifying and localizing an EM counterpart. and localizing an EM counterpart.

Short GRBs are detectable & identifiable, but are limited to <~ 1 Short GRBs are detectable & identifiable, but are limited to <~ 1 detection yrdetection yr-1-1 and may not provide localization. These rare and may not provide localization. These rare detections are nevertheless crucial, so an operational detections are nevertheless crucial, so an operational -ray satellite -ray satellite similar to Fermi GBM is important.similar to Fermi GBM is important.

No optical or radio facilities can provide all-sky coverage at a No optical or radio facilities can provide all-sky coverage at a cadence and depth matched to the expected counterpart light cadence and depth matched to the expected counterpart light curves curves targeted follow-up is required. targeted follow-up is required.

Optical afterglow emission is easily detectable for on-axis events Optical afterglow emission is easily detectable for on-axis events with rapid follow-up. However, off-axis optical afterglows are only with rapid follow-up. However, off-axis optical afterglows are only detectable for detectable for obsobs < 2 < 2 j j (even with LSST) (even with LSST) and hence are limited to and hence are limited to <~ 10% of all mergers.<~ 10% of all mergers.

Radio afterglow emission is isotropic, but existing and planned are Radio afterglow emission is isotropic, but existing and planned are not sufficiently sensitive, given the low Enot sufficiently sensitive, given the low Ejetjet/n from existing SGRB /n from existing SGRB afterglows.afterglows.

Isotropic kilonovae are in principle detectable for most events, but Isotropic kilonovae are in principle detectable for most events, but require a follow-up telescope with sensitivity similar to Pan-require a follow-up telescope with sensitivity similar to Pan-STARRs/LSST and a short cadence.STARRs/LSST and a short cadence.

This is going to be hard, so we need to start planning now! This is going to be hard, so we need to start planning now!

Zhang & MacFadyen 2009Zhang & MacFadyen 2009

Gamma-Ray Burst “Afterglows” - Synchrotron Emission Gamma-Ray Burst “Afterglows” - Synchrotron Emission from Shock Interaction with the Circumburst Mediumfrom Shock Interaction with the Circumburst Medium