Premise GW-GRB association GW Inference EMGW Inference Follow-up

GW170817/GRB 170817AAn Astronomy/Astrophysics Viewpoint

Deep Chatterjee12

on behalf of the LIGO-Virgo Collaboration

1University of Wisconsin – Milwaukee

2LIGO–Virgo Collaboration

Rencontres de Moriond, La ThuileMarch 26, 2019

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Lights, Camera, Follow-up...

GW170817[Abbott et al., 2017c]GRB 170817A[Goldstein et al., 2017,Abbott et al., 2017b]

SSS17aEM170817...AT 2017gfo[Abbott et al., 2017d]

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Notice TimelineUnprecedented Follow-up Operations

10−4 10−3 10−2 10−1 100 101

t− tmerger (days)

GWDetection

InitialCircular

InitialSkymap

FinalSkymapGWs

γ Rays

X rays/UV

Optical/IR/UV

Radio

Radio, X-ray follow-up operations ∼ 1yr.

Speed of gravity = c ?

On August 17, it was established correctup to 15 decimal places!

Premise GW-GRB association GW Inference EMGW Inference Follow-up

The Story it Told...In this talk

The astrophysics:

• Independent measurement of H0

• Tidal deformability & neutron star equation of state (EoS)

• Physics of “kilonova”

• Progenitor model

• Post-merger remnant

• Stochastic background & merger rates

Multi-messenger astronomy:

• Follow-up operations

• Looking ahead at the third observing run (O3)

Premise GW-GRB association GW Inference EMGW Inference Follow-up

GW-GRB Association

• GW170817 - GRB 170817A unambiguous association

• Chance spatio-temporal coincidence, p = 5× 10−8 ⇒ 5.3σsignificance. [Abbott et al., 2017b]

BNS system are progenitors of, at least, some short GRBs

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Parameter EstimatesGW170817 Masses and Spins

1.4 1.5 1.6 1.7 1.8m1 (M)

1.05

1.10

1.15

1.20

1.25

1.30

1.35

1.40

m2

(M

)

TaylorF2

SEOBNRv4NRT

IMRPhenomPv2NRT

SEOBNRv4T

TEOBResumS

0

30

60

90

120

150

180

0.0

0.2

0.4

0.6

0.8

0

30

60

90

120

150

180

0.0

0.2

0.4

0.6

0.8

0

30

60 90

120

150

180

0

30

60 90

120

150

180

GW170817

cS1/(Gm21) cS2/(Gm

22)

Credits [Abbott et al., 2018b]

Mc↑

Chirp mass

= 1.186M; ∆Ω↑

Sky loc.

= 16deg2; dL↑

Lumin. dist.

= 40Mpc; SNR↑

Signal to noise

= 33

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Parameter EstimatesTidal Deformability

Tidal Deformability

↓Λ︸︷︷︸

in signal

= (2/3)

EoS dependent︷ ︸︸ ︷k2

(Gm

c2R

)−5

Effective tidal parameters enter waveform @ 5 PNCredits [Abbott et al., 2018a]

8 10 12 14

R (km)

0.5

1.0

1.5

2.0

2.5

3.0

m(M

)

WF

F1

AP

R4

SL

yM

PA

1

H4

BHlim

it

Buchd

ahl lim

it0

1

0 10 250 500 750 1000 1250

Λ1

0

500

1000

1500

2000

Λ2

WFF1

APR4

SLy

MPA1

H4

MS1b

MS1

More Compact

Less Compact

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Neutron Star Equation of State

0 200 400 600 800 1000 1200 1400 1600

Λ

0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

0.0035

PD

F

WF

F1

AP

R4

SL

y

MP

A1

H4

MS

1b

MS

1

IMRPhenomPv2NRT

SEOBNRv4NRT

SEOBNRv4T

TEOBResumS

TaylorF2

Prior

Low Spin Prior

0 200 400 600 800 1000 1200 1400 1600

Λ

0.0000

0.0005

0.0010

0.0015

0.0020

0.0025

0.0030

0.0035

PD

F

WF

F1

AP

R4

SL

y

MP

A1

H4

MS

1b

MS

1

IMRPhenomPv2NRT

SEOBNRv4NRT

SEOBNRv4T

TEOBResumS

TaylorF2

Prior

High Spin Prior

Low Support for stiff EoS

MS1 like EoS ruled out with ≥ 90% confidence

• Compact NS favored

• For GW170817, R1 = 11.9+1.4−1.4km; R2 = 11.9+1.4

−1.4km[Abbott et al., 2018a]

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Dynamical EjectaGW parameters → Mej

Mej = Mej(m, mb↑

Baryon mass

, R↑

Radius

)

m,Λ︸︷︷︸from GW

EoS−−→ mb,R

NR fitting [Dietrich and Ujevic, 2017]

4 3 2 1 0 1

log10(Mej/M¯)

0.0

0.2

0.4

0.6

0.8

1.0

H4 (low spin)

SLy (low spin)

MPA1 (low spin)

APR4 (low spin)

H4 (high spin)

SLy (high spin)

MPA1 (high spin)

APR4 (high spin)

100 101

tpeak (hr)

15

16

17

18

19

20

Pea

ki-

ban

dA

pp

aren

tM

agn

itu

de

−4.0

−3.6

−3.2

−2.8

−2.4

−2.0

−1.6

−1.2

log 1

0(M

ej/M

)

Credits [Abbott et al., 2017a]

Premise GW-GRB association GW Inference EMGW Inference Follow-up

r -process Abundance

ρrp = frp︸︷︷︸fraction converted

×Mej ×merger rate︷︸︸︷R ×

Total time considering SFR

↓〈Tmergers〉

Xrp︸︷︷︸r -process fraction

= ρrp/ ρ∗︸︷︷︸Star form.

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

log10(ρrp/frp [M Mpc−3])

0.0

0.2

0.4

0.6

0.8

1.0

PD

F

H4

MPA1

SLy

APR4

−8 −7 −6 −5log10(Xrp/frp)

Credits [Abbott et al., 2017a]

frp ≥ 10%accounts forMW abundance[Abbott et al., 2017a]

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Post-Merger RemnantGW Signatures

• Possible scenarios:• Prompt collapse into BH; quasi-normal modes• Hypermassive NS; collapse to BH . 1s• Supramassive NS; collapse to BH ∼ 10− 104s• Stable NS

• Absence of template waveform

• Generic search for excess power in spectrogram

• Whatever the scenario, optimistic GW emission @SNR ∼ 1− 2 in LIGO-Virgo band.

No GW signature found

Signal, if present, is too weak for current sensitivity/searches[Abbott et al., 2017f, Abbott et al., 2019]

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Progenitor of GW170817Occurrence ∼ 2kpc from center of NGC 4993, constrains:

• Delay time, Tdelay

• Distance of second CC-SNe, RSN

• Natal kick, vkick

Credits [Abbott et al., 2017e]

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Progenitor of GW170817

Progenitor properties robust if stellar properties of NGC 4993 isolder that ∼ 1Gyr [Abbott et al., 2017e]

v90%kick ' 300+250

−200kms−1; R90%SN ' 2.0+4.0

−1.5kpc

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Hubble Constant Measurement

50 60 70 80 90 100 110 120 130 140H0 (km s 1 Mpc 1)

0.00

0.01

0.02

0.03

0.04p(

H0)

(km

1sM

pc)

p(H0 GW170817)Planck17

SHoES18

Credits [The LIGO Scientific Collaboration et al., 2017]

General agreement with H0 from SNIa’s and CMBMore detections will sharpen posterior

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Looking ahead in O3Implication of Rates

Detector BNS range (Mpc)LIGO ∼ 120–140

Virgo ∼ 50

Kagra . 25

• Expected Rates 1:• Total BNS count ∼ 1–10.• BBH candidates are expected once a week.• NSBH rates uncertain at this stage.

• Skymaps:• BNS systems will have median 90% sky areas between

120− 180 deg2.• 12− 21% such systems expected to be localized ≤ 20 deg2.

1https://dcc.ligo.org/LIGO-G1800370/public

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Follow-up campaign

• GW170817:

• First success story ofelectromagnetic &gravitational-wave (EMGW)astronomy.

• Follow-up operations wereunprecedented.

O2 partners

• Need for a rapid, robust alert infrastructure:• Semi-automated with low false alarm.• Data products from GW side to aid EM follow-up.• Crucial to capture the transient at early times.

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Public AlertsFor the first time, LIGO-Virgo Alerts will be public!

PreliminaryAlert Sent

Rapid Localization Classification

Automated Vetting Set Preferred Event

Original Detection

Initial Alert orRetraction Sent

Classification Human Vetting

Parameter Estimation

10 second 1 minute 1 hour 1 day 1 week

UpdateAlert Sent Classification

Parameter Estimation

• All alerts are sent over Gamma-ray Coordinate Network (GCN)

• Retractions might happen at the Initial stage

• Circulars are sent during Initial alert

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Low-latency Data ProductsSkymaps Chances of EM-counterpart

100 101 102

m1[M ]

100

101

m2[

M]

BNS NSBH

BBH

Mrem =0

Pastro by source category

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Combined SkymapsWill be sent for Fermi and IceCube

(a) GW170817 (HL) (b) Fermi GBM

(c) Combined

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Userguide for alerts in O3

https://emfollow.docs.ligo.org/userguide/

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Abbott, B. P. et al. (2017a).

Estimating the contribution of dynamical ejecta in the kilonova associated with GW170817.The Astrophysical Journal, 850(2):L39.

Abbott, B. P. et al. (2017b).

Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A.The Astrophysical Journal Letters, 848:L13.

Abbott, B. P. et al. (2017c).

GW170817: Observation of gravitational waves from a binary neutron star inspiral.Phys. Rev. Lett., 119:161101.

Abbott, B. P. et al. (2017d).

Multi-messenger Observations of a Binary Neutron Star Merger.ApJ Lett., 848:L12.

Abbott, B. P. et al. (2017e).

On the progenitor of binary neutron star merger GW170817.The Astrophysical Journal, 850(2):L40.

Abbott, B. P. et al. (2017f).

Search for Post-merger Gravitational Waves from the Remnant of the Binary Neutron Star MergerGW170817.ApJ Lett., 851:L16.

Abbott, B. P. et al. (2018a).

GW170817: Measurements of Neutron Star Radii and Equation of State.Phys. Rev. Lett., 121:161101.

Abbott, B. P. et al. (2018b).

GWTC-1: A Gravitational-Wave Transient Catalog of Compact Binary Mergers Observed by LIGO andVirgo during the First and Second Observing Runs.arXiv e-prints, page arXiv:1811.12907.

Abbott, B. P. et al. (2019).

Premise GW-GRB association GW Inference EMGW Inference Follow-up

Properties of the Binary Neutron Star Merger GW170817.Physical Review X, 9:011001.

Dietrich, T. and Ujevic, M. (2017).

Modeling dynamical ejecta from binary neutron star mergers and implications for electromagneticcounterparts.Classical and Quantum Gravity, 34:105014.

Goldstein, A. et al. (2017).

An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB170817A.ApJL, 848:L14.

The LIGO Scientific Collaboration, The Virgo Collaboration, The 1M2H Collaboration, The Dark Energy

Camera GW-EM Collaboration, The DES Collaboration, The DLT40 Collaboration, The Las CumbresObservatory Collaboration, The VINROUGE Collaboration, and The MASTER Collaboration (2017).A gravitational-wave standard siren measurement of the Hubble constant.Nature, 551(7678):85–88.