Observations multi-messager d'une coalescence de système binaire d'étoiles à neutrons - Damir Buskulic - LAPP
←
→
Transcription du contenu de la page
Si votre navigateur ne rend pas la page correctement, lisez s'il vous plaît le contenu de la page ci-dessous
Observations multi-messager d’une coalescence de
système binaire d’étoiles à neutrons
Damir Buskulic
Séminaire d’insertion professionnelle M2 PSC
20 octobre 2017
Détection d’ondes gravitationnelles
Par le réseau de détecteurs interférométriques
Advanced LIGO – Advanced Virgo
LSC : ~900 membres Virgo : ~200 membres
~80 institutions 19 laboratoires
de ~15 pays de 5 pays
Depuis 2007, LVC = LIGO-Virgo Collaboration 2
Ondes gravitationnelles
▶ Masses : accélération du moment ▶ Onde plane transverse
quadripolaire ▶ Se propage à la vitesse de la
lumière
▶ Déformation de l’espace-temps ▶ Deux polarisations (+ et x)
▶ Onde gravitationnelle
▶ Effet sur un ensemble de masses
test en chute libre
3
Ondes gravitationnelles
▶ Production :
▶ Distribution de masses : accélération du moment quadripolaire
▶ Exemples
▶ M = 1000 kg, R = 1 m, f = 1 kHz,
r = 300 m
h ~ 10-35
▶ M = 1.4 M⦿ , R = 20 km, f = 400 Hz,
r = 1023 m (15 Mpc = 48,9 Mlyr )
h ~ 10-21 4
Interféromètre de Michelson :
un “capteur” d’ondes gravitationnelles
Diagramme d’antenne
Moyenne sur les polarisations
5
Résumé des runs O1 et O2
2015 2016 2017
09 10 11 12 01 02 03 04 05 06 07 08 09 10 11 12 01 02 03 04 05 06 07 08 09 10
O1 O2a
Aujourd’hui
12/09/2015
19/01/2016
30/11/2016
25/08/2017
01/08/2017
LVT151012
GW150914 GW151226 GW170104 GW170814
Premier événement Virgo!
GW170817
+ détections multi-messagers!
O2 cycles utiles :
●LIGO H1: ~60%
●LIGO L1: ~60%
●Virgo V1: ~80% (O2b)
6
Recherche de la coalescence
d’un système binaire d’objets compacts
▶ Cible : Signal venant de la coalescence d’un système binaire d’objets compacts
▶ Etoiles à neutrons (BNS), Etoiles à neutrons + Trou noir (NS-BH),
Trou noir binaire (BBH)
▶ Phases de la coalescence:
▶ Spiralante (Inspiral)
▶ Masses m1 et m2 en orbite
l’une autour de l’autre
▶ Emission d’OG
▶ Frequence ↗, amplitude ↗
▶ Forme d’onde caractérisée par la
« masse chirp »
Time
▶ Fusion (Merger) : Calculs de relativité numérique
▶ Relaxation (Ringdown) : décomposition en mode quasi-normaux
7
Recherche de la coalescence
d’un système binaire d’objets compacts
▶ Principe de l’analyse : recherche avec calque
▶ Production d’une banque de calques (formes d’onde théoriques)
Test template
▶ Filtrage adapté =
inter-corrélation pondérée
signal/calque
Recherche de la coalescence
d’un système binaire d’objets compacts
▶ Principe de l’analyse : recherche avec calque
▶ Production d’une banque de calques (formes d’onde théoriques)
▶ Filtrage adapté = inter-corrélation pondérée signal/calque
Densité spectrale de bruit
Signal caché dans le bruit Calque du détecteur
Ä /
Résultat du filtrage adapté : r(t)
Evénement
"Z # candidat
• ã( f ).T
e ⇤( f )
hã, Tei = 2 d f + c.c.
0 Sn( f ) Seuil
▶ Très sensible à l’évolution de la phase 9
Recherche de la coalescence
d’un système binaire d’objets compacts
▶ Paramètres intrinsèques 4
▶ masses, tive
spins
to BBH(mergers
alignés with)total
dirigent
mass ⇠ 30 M or greater [60].
arXiv:1606.04856 [gr-qc]
A bank of template waveforms is used to cover the parame-
la dynamique du système
| 1 | < 0.9895, | 2 | < 0.05
▶ ter space to be searched [53, 61–64]. The gravitational wave-
| 1,2 | < 0.05
| 1,2 | < 0.9895
forms depend upon the masses m1,2 (using the convention that
▶ l’évolution de la forme d’onde
m1 m2 ), and angular momenta S1,2 of the binary compo-
GW150914
GW151226
nents. We characterise the angular momentum in terms of the LVT151012 (gstlal)
espace de paramètres 4-D balayé avec
m2 [M ]
101
▶ dimensionless spin magnitude
LVT151012 (PyCBC)
~250,000 calques a1,2 = c |S1,2| , (2)
Gm21,2
and the component aligned with the direction of the orbital
▶ Paramètres extrinsèques
angular momentum, L, of the binary [65, 66],
100
c
Position dans le ciel, orientation de la binaire,
0 1 2
▶ c1,2 = S1,2 · L̂ . (3) 10 10 10
Gm21,2 m [M ] 1
phase initiale,…
We restrict this template bank to systems for which the spin
impacte of the systems is aligned (or anti-aligned) with the orbital an- FIG. 2. The four-dimensional search parameter space covered by
the template bank shown projected into the component-mass plane,
gular momentum of the binary. Consequently, the waveforms using the convention m > m . The colours indicate mass regions
▶ le temps d’arrivée
primarily upondu signal 1 2
depends the chirp mass [67–69] with different limits on the dimensionless spin parameters c and 1
c . Symbols indicate the best matching templates for GW150914,
▶ l’amplitude globale et la1 mphase
2
(m 3/5
2) GW151226 and LVT151012. For GW150914, GW151226 the tem-
M= , (4)
M 1/5 plate was the same in the PyCBC and GstLAL searches while for
▶ On maximise dessus
the mass ratio [18]
LVT151012 they differed. The parameters of the best matching tem-
plates are not the same as the detector frame masses provided by the
detailed parameter estimation discussed in Section IV.
m2
q= 1, (5)
m1 10
and the effective spin parameter [70–73] non-stationary transients in the data. Events are assigned aTaux de fausse alarme
▶ Taux de fausse alarme
▶ Mesuré avec le bruit de fond estimé à partir des données
▶ Décalages temporels de N x 0.1 s entre H1 et L1
L1
H1
L1-100s
time
▶ Cas de GW150914, première analyse pour l’annonce
▶ Nmax = 107 décalages, Tfond = 200,000 ans
▶ GW150914 plus fort que tous les fonds â limite basse sur la significativité
▶ Importance du veto des perturbations environementales.
▶ Surveillance par un réseau de capteurs
▶ ~105 canaux pour chaque détecteur
11GW170814 : le premier événement Virgo !
▶ Détecté le 14 août 2017 à 10:30:53 UTC
▶ Rapport signal sur bruit combiné (SNR) = 18
▶ Taux de fausse alarme f < 1 sur 27000 ans
-> une coalescence de binaire de trous noirs
comme le premier événement découvert GW150914
12C’est mieux avec Virgo !
Meilleure localisation de la source Premiers tests de polarisation de l’OG
Relativité générale
→ 2 modes de polarisation
Théories métriques de la gravité en général
→ 6 modes autorisés
Avec les deux LIGO seuls : 700 deg2
En incluant Virgo: 80 deg2
Localisation 2D
Nouveaux tests avec GW170814
→ aire dans le ciel réduite d’un facteur ~10 Un interféromètre est sensible à une OG projetée sur le
mode + local du détecteur.
Localisation 3D Étude des modes de polarisation de l’onde avec plusieurs
→ Volume dans le ciel réduit d’un facteur ~20 détecteurs orientés différemment.
→ mode « purs » + et x favorisés par rapport aux
polarisations pures scalaire/vecteur
(mélanges de polarisations pas encore testés)
13Masses des objets binaires compacts
Trous noirs binaires
Etoiles à neutrons
14Physique avec les TN binaires
Formation des TN binaires Détermination de la distribution et du taux de
coalescence de la population de TN binaires
Evolution d’étoiles
binaires
(défavorisé ?)
Implications
Estimation du fond
astrophysiques Capture de TN stochastique d’OG
isolés des coalescences de
TN binaires
Limites sur la masse du graviton et une violation de
l’invariance de Lorentz
Vérification de la
cohérence interne de la
forme d’onde
Tests de la RG
Recherche de déviations de la RG dans la forme d’onde
15▶ Première détection multi-messager d’une
coalescence d’étoiles à neutrons : GW170817
▶ Signal d’OG
▶ Association avec un sursaut gamma (GRB)
▶ Suivi électromagnétique et kilonova
▶ Mesure de la constante de Hubble
▶ Recherche de neutrinos
16Coalescence dans les données LIGO-Virgo
▶ Détecté le 17 août 2017 à 12:41:04.4 UTC
▶ Rapport signal sur bruit combiné (SNR) = 32.4 ▶ Signal faible dans Virgo
▶ Taux de fausse alarme f < 1 sur 80000 ans ▶ Sensibilité la plus faible + orientation défavorable
▶ Ne participe pas à la détection
▶ Mais effet significatif sur l’estimation de paramètres
▶ En particulier la localisation
Diagramme d’antenne
projeté sur la Terre
(sombre = moins sensible)
LIGO (Livingston) Virgo
17Localisation de la source GW170817
▶ La source du signal est la plus proche et la mieux localisée jusqu’à aujourd’hui
▶ Déclenchement d’observations de suivi EM et neutrinos
▶ Identification de NGC4993 comme galaxie hôte
18Comparaison des signaux détectés
Coalescence de binaires de TN
Signaux courts ( information sur le type de source et ses paramètres
19Paramètres intrinsèques
Masses des objets Equation d’état des étoiles à neutrons
Dégénérescence entre le Trace dans la
Champ de marée Déformation de
rapport des masses et les forme de l’OG,
du compagnon l’étoile à neutrons
composantes alignées des pour f>600 Hz
spins
La collision se produit
plus tôt que sans effet
de marée,
spin final modifié
Résultat en défaveur des équations d’état qui prédisent
une étoile moins compacte :
rayon < 15 km
Masses cohérentes avec des étoiles à neutrons
20Contreparties électromagnétiques
▶ Sursaut gamma court (sGRB) :
▶ Jet
▶ Emission gamma rapide (prompt)
▶ Quelques secondes après la fusion
▶ Durée < 2 s
▶ Focalisée
▶ Interaction du jet avec le milieu interstellaire
▶ Emission rémanente (afterglow)
▶ Quelques jours après la fusion
▶ Evolution rayons X -> radio
▶ Kilonova
▶ Conversion de la matière éjectée dans des
éléments issus d’un processus r (r-process),
désintégration et émission thermique
▶ Continuum de corps noir + structures larges
▶ Quelques heures/jours après la fusion
▶ UV / optique / IR
▶ Évolution spectrale rapide
21▶ Première détection multi-messager d’une
coalescence d’étoiles à neutrons : GW170817
▶ Signal d’OG
▶ Association avec un sursaut gamma (GRB)
▶ Suivi électromagnétique et kilonova
▶ Mesure de la constante de Hubble
▶ Recherche de neutrinos
22▶ GRB170817A détecté par Fermi et INTEGRAL Localisation sur le ciel
▶ Emission gamma ~ 1.7 s après la fusion (90% CL)
▶ 3 fois plus probable d’être un GRB court (vs long)
Probabilité d’une association aléatoire : 5.0 x 10-8
-> association validée à 5.3 s
Première preuve que les fusions d’étoiles à
neutrons sont les progéniteurs des GRB courts
(au moins certains)
23Newi
nsi
ghti
ntogamma-
raybur
sts
GW170817 waveform → loose limit on BNS viewing angle, but degeneracy with source distance
● F < 56° from GW data alone
● F < 36° using the known distance to the host galaxy NGC 4993
→ compatible with jet pointing towards Earth
GRB170817A:
● the closest short GRB with know distance (z~0.008)
(previous closest, GRB061201: z ~0;11)
● 10 to 106 times less energetic than other bursts
2
→ implications/questions on the structure of the jet
Prediction of detection rates
●higher rate than previously expected for sGRB to be seen in gamma-rays
●1-50 BNS mergers expected in LIGO-Virgo during run O3 (wrt previously estimated 0.04-100)
→ 0.1 to 1.4 joint detections for GW and Fermi sGRB during run O3 (end 2018-2019)
Abbot at al., ApJ, 848, 13 (2017)
L. Rolland - 10 novembre 2017 - LAPP 24 19Association GW/GRB : célérité des OG
Emission lors de la fusion Propagation
-> OG et rayons g sur au moins 26 Mpc Détection
OG
Rayons g
Hypothèse : rayons g détectés
les g sont émis entre s après les OG
0 et 10 s après les OG de fusion
Différence entre la célérité des OG et la vitesse de la lumière
25▶ Première détection multi-messager d’une
coalescence d’étoiles à neutrons : GW170817
▶ Signal d’OG
▶ Association avec un sursaut gamma (GRB)
▶ Suivi électromagnétique et kilonova
▶ Mesure de la constante de Hubble
▶ Recherche de neutrinos
26T0 T0 + 1.7 s T0 + 5 h T0 + 11 h T0 + 11h T0 + 9 j T0 + 16 j
Détection Détection Localisation Contrepartie Galaxie hôte Contrepartie Contrepartie
GW GRB GW optique NGC4993 X radio
27Evolution du transitoire optique
IR proche
Rouge
Bleu / UV
Bleu IR proche IR moyen
Courbes de lumière
Evolution du spectre
▶ Bon accord avec les modèles de kilonova (=macronova)
▶ Première identification spectroscopique d’une kilonova
▶ Probablement la source principale d’éléments lourds dans l’univers
28▶ Première détection multi-messager d’une
coalescence d’étoiles à neutrons : GW170817
▶ Signal d’OG
▶ Association avec un sursaut gamma (GRB)
▶ Suivi électromagnétique et kilonova
▶ Mesure de la constante de Hubble
▶ Recherche de neutrinos
29Mesure de la constante de Hubble
H0 = taux d’expansion
GW170817 peut être utilisée comme sirène standard
de l’univers aujourd’hui
Estimée directement Déterminée avec le
du signal OG : redshift de la galaxie hôte
à En déduit
Mesure indépendante de H0
à pourra aider à comprendre la « tension » courante
30Liste non exhaustive
des études en cours/à faire
▶ Implications astrophysiques
▶ Formation des binaires de neutrons / trous noirs
▶ Origine des GRB, focalisation du jet
▶ Modélisation des kilonovae
▶ Equation d’état des NS (neutron star)
▶ Etoile à neutron résidu de la fusion : durée de vie longue ou courte ?
▶ Inférence de la distribution de population BNS et du taux de coalescence
▶ Estimation du fond stochastique d’OG de coalescences de BNS
▶ Détecté dans les années à venir
▶ Tests de RG
▶ Différence entre célérité des OG et c
▶ Recherche de déviations à la RG dans la forme d’onde
▶ Etude de la polarisation des OG
▶ Nouvelles limites à la violation de l’invariance de Lorentz
▶ Nouveau test du principe d’équivalence
▶ Cosmologie
▶ Mesure indépendante de la constante de Hubble 31Le futur du coin de l’œil…
Living Rev. Relativity, 19, (2016), 1
32Conclusion
▶ Premières…
▶ Premier tests de la polarisation d’une OG
▶ Première observation de la coalescence d’une binaire à neutrons
▶ Première association BNS – GRB court
▶ Première observation photométrique d’une kilonova
▶ Première mesure de la constante de Hubble avec les OG
▶ A l’avenir, on espère
▶ Détection d’une coalescence étoile à neutrons-trou noir
▶ Détection du fond stochastique BNS et BBH
▶ Détection d’une OG de supernova
▶ Plus de détections multi-messagers
▶ Et il y a du travail sur les OG continues (pulsars) et sur les transitoires non
modélisés
▶ Et on prépare LIGO et Virgo pour le run O3 à l’automne 2018
33▶ Spares
34What does Virgo look like ?
35What does LIGO look like ?
36▶ Horizon = distance at which a
reference compact body
coalescence gives a SNR (Signal
over Noise Ratio) of 8 in the
detectors
▶ Picture : reference = 2 x 1.4 M⦿
neutron star coalescence,
average orientation
▶ Sensitivity x 10 ó Sensitive
volume x 103
37Black holes coalescences ? Yes !
▶ Example of GW150914
▶ Over 0.2 s, frequency and amplitude increase
from 35 Hz to fpeak = 150 Hz (~ 8 cycles)
▶ Reminder : the “chirp mass” characterizes
the inspiral phase
▶ Finds ,
▶ Keplerian separation gets close to
Schwarzschild radius
▶ Very close and compact objects
▶ BNS too light, NSBH merge at lower frequency
▶ Decay of waveform after peak
▶ consistent with damped oscillations of BH
(relaxing to final stationary Kerr configuration)
▶ SNR too low to claim observation of quasi normal modes 38CBC BBH search result : GW150914
2 3 4 5 >5
Statistic
arXiv:1606.04856 [gr-qc]
▶ 104 2 3 4 5 >5
103 Search Result
▶ Search Background
102
Background excluding GW150914
101
Number of events
▶ 100
10 1
Significance 10 2
▶ 3
GW150914
10
▶ GW150914 is the loudest event in the 10 4
5
10
search, = 22.7 10 6
10 7
10 8
▶ Individual triggers in L1 and H1 8 10 12 14 16 18 20 22 24
Detection statistic ˆc
(forming GW150914): highest in each
detector
▶ Significance Coincidences between single
Background excluding contribution detector triggers from GW150914
from GW150914 (gauge significance and noise in other detector
of other triggers)
39Testing GR with GW150914 (II)
▶ No evidence for deviation from GR in waveform
arXiv:1606.04856 [gr-qc]
▶ No evidence for dispersion in signal propagation
FIG. 6. Posterior density distributions and 90% credible intervals for relative deviations d p̂i in the PN parameters pi , as well
▶ Bounds : bi and merger-ringdown parameters ai . The top panel is for GW150914 by itself and the middle one for GW15
parameters
while the bottom panel shows combined posteriors from GW150914 and GW151226. While the posteriors for deviations in
from GW150914 show large offsets, the ones from GW151226 are well-centered on zero as well as being more tight, causing
posteriors to similarly improve over those of GW150914 alone. For deviations in the bi , the combined posteriors improve over
event individually. For the ai , the joint posteriors are mostly set by the posteriors from GW150914, whose merger-ringdo
frequencies where the detectors are the most sensitive.
▶ More constraining than bounds from
up to 3.5PN. Since the source of GW151226 merged at merical waveforms and tend to multiply speci
▶ Solar
⇠ 450System observations
Hz, the signal provides the opportunity to probe the f , and they characterize the gravitational-wave a
PN inspiral with many more waveform cycles, albeit at rel- phase in different stages of the coalescence proc
▶ binary pulsar
atively low SNR.observations
Especially in this regime, it allows us to allow for possible departures from general rela
▶ Lesstighten
constraining
further our than
boundsmodel dependent
on violations bounds from
of general relativity.
As in [41], to analyze GW151226 we start from the IMR-
eterized by a set of testing coefficients d p̂i , w
form of fractional deviations in the pi [135, 13
▶ large
Phenomscale dynamics
waveform of[35–37]
model of galactic clusters
which is capable of de- replace pi ! (1 + d p̂i ) pi and let one or more of
scribing inspiral, merger, and ringdown, and partly accounts freely in addition to the source parameters tha
▶ weak gravitational lensing observations
for spin precession. The phase of this waveform is charac- 40
in pure general relativity waveforms, using the
terized by phenomenological coefficients {pi }, which include ativity expressions in terms of masses and spi
themselves. Our testing coefficients are thoseFuture Localization Prospects
Face-on BNS
@ 80 Mpc
2016-17 2017-18
Face-on BNS
@ 160 Mpc
2019+ 2022+
HLV = Hanford-Livingston-Virgo HILV = Hanford-LIGO India-Livingston-Virgo
41From one generation to the next (II)
Terrestrial detectors Einstein Telescope (ET)
Advanced LIGO,
Advanced Virgo,
GEO HF, KAGRA
Foundations of
multi-messenger astronomy First
detection
Enhanced LIGO, Virgo+
Initial LIGO, Virgo,
GEO600
First generation Second generation Third generation
Data taking Towards routine observations, In-depth observation of
Rates upper limits GW astronomy the universe with GW
Building the network
42Table 3 Summary of a plausible observing schedule, expected sensitivities, and source localization with
the Advanced LIGO, Advanced Virgo and KAGRA detectors, which will be strongly dependent on the
Plan and sensitivity evolution
detectors’ commissioning progress. Ranges reflect the uncertainty in the detector noise spectra shown in
Figure 1. The achieved binary neutron star (BNS) ranges for 2016 – 2017 are characteristic of performance
to date, not for the complete run. The burst ranges assume standard-candle emission of 10 2 M c2 in
1/2
gravitational waves at 150 Hz and scale as EGW , so it is greater for more energetic sources (such as binary
Prospects for Observing and Localizing GW Transients with aLIGO, AdV and KAGRA 5
black holes). The BNS localization is characterized by the size of the 90% credible region (CR) and the
searched area. These are calculated by running the BAYESTAR rapid sky-localization code [189] on a
Advanced LIGO Advanced Virgo
Monte Carlo sample of simulated signals, assuming senisivity curves in the middle of the plausible Living Rev. Relativity, 19, (2016), 1
ranges
(the geometric meansMidof(2016the upper and lower bounds). The variation
Early (2015 – 16, 40 – 80 Mpc)
– 17, 80 – 120 Mpc)
in the localization reflects both the
Early (2017, 20 – 65 Mpc)
Mid (2018 – 19, 65 – 85 Mpc)
variation in duty cycleLatebetween
(2018 – 19, 120 –70%
170 Mpc)and 75% as well as Monte Carlo statistical uncertainty. The estimated
1/2
1/2
Late (2020 – 21, 65 – 115 Mpc)
number of BNS detections uses
Design (2020, 190 Mpc) the actual BNS for 2015 – 2016, and the 125
Design (2021, expected
Mpc) range otherwise; future
Strain noise amplitude/Hz
Strain noise amplitude/Hz
21 21
10 10
BNS-optimized (210 Mpc) BNS-optimized (140 Mpc)
runs assume a 70 – 75% duty cycle for each instrument. The BNS detection numbers also account for
the uncertainty in the BNS source rate density [73]. Estimated BNS detection numbers and localization
estimates are computed assuming a signal-to-noise
10 22
10 ratio greater than 12. Burst localizations are expected to
22
be broadly similar to those derived from timing triangulation, but vary depending on the signal bandwidth;
the median burst searched area (with a false alarm rate of ⇠ 1 yr 1 ) may be a factor of ⇠ 2 – 3 larger than
the values quoted for BNS signals [202]. No burst detection numbers are given, since the source rates
23 23
10 10
are currently unknown. Numbers for 2016 – 2017 include Virgo, and do not take into account that Virgo
only joined the observations for the latter part the run. The 2024+ scenario includes LIGO-India at design
24 24
sensitivity.
10 10
1 2 3 1 2 3
10 10 10 10 10 10
Frequency/Hz Frequency/Hz
KAGRA
Opening (2018 – 19, 3 – 8 Mpc)
Epoch 2015 – 2016 2016 – 2017 2018 – 2019
Early (2019 – 20, 8 – 25 Mpc)
2020+ 2024+
1/2
Planned run duration 4 months 9 months 12 months
Mid (2020 – 21, 25 – 40 Mpc)
(per year) (per year)
Late (2021 – 22, 40 – 140 Mpc)
Strain noise amplitude/Hz
21
LIGO 40 140 – 60 60 – 75 75 – 90 105 105
10
Design (2022, Mpc)
Expected burst range/Mpc Virgo — 20 – 40 40 – 50 40 – 70 80
KAGRA — 22
— — — 100
10
LIGO 40 – 80 80 – 120 120 – 170 190 190
Expected BNS range/Mpc Virgo — 20 – 65 65 – 85 65 – 115 125
10
KAGRA — 23 — — — 140
LIGO 60 – 80 60 – 100 — — —
Achieved BNS range/Mpc Virgo — 25 – 30 — — —
10 KAGRA — 24
1 2
— — 3
— —
10 10 10
Estimated BNS detections Frequency/Hz 0.002 – 2 0.007 – 30 0.04 – 100 0.1 – 200 0.4 – 400
Actual BNS detections 0 — — — —
Fig. 1 Regions of aLIGO (top left), AdV (top right) 2 and KAGRA (bottom) target strain sensitivities as a
function of frequency. The%binary
5 deg
neutron star (BNS)Generic Transient Search
q Operates without a specific search model
▶ Identifies coincident
excess power in time-
frequency
representations of h(t)
▶ Frequency < 1 kHz
▶ Duration < a few seconds
q Reconstructs signal waveforms consistent with common GW signal in
both detectors using multi-detector maximum likelihood method
q Detection statistic Ec: dimensionless coherent signal energy obtained by
cross-correlating the two reconstructed waveforms
Ø En: dimensionless residual noise energy after
reconstructed signal is subtracted from data
q Signals divided into 3 search classes based on their time-frequency
morphology
Ø C3 : Events with frequency increasing with time – CBC like 44Expected BBH Stochastic Background
▶ GW150914 suggests population of
BBH with relatively high mass
▶ Stochastic GW background from
BBH could be higher than
expected
▶ Incoherent superposition of all
merging binaries in Universe
▶ Dominated by inspiral phase
▶ Estimated energy density
▶ Statistical uncertainty due to
poorly constrained merger rate
currently dominates model
uncertainties
▶ Background potentially detectable
by Advanced LIGO / Advanced
Virgo at projected final sensitivity 45Sensitivity
Phys. Rev. Lett. 116, 131103 (2016)
Seismic noise S6
Improved
O1
seismic
aLIGO
isolation
design
Future
upgrade
Thermal noise Quantum noise
Monolithic suspensions Higher laser power
Improved mirror coatings Thermal compensation
Larger beam size Signal recycling
DC detection 46Intrinsic Parameters
week ending
L 116, 241103 (2016) PHYSICAL REVIEW LETTERS 17 JUNE 2016
arXiv:1606.04856 [gr-qc]
Inspiral
PRL 116, 241103 (2016) Merger + Ringdown
▶ Encoded in GW signal :
. 5. Estimated gravitational-wave strain from GW151226 projected onto the LIGO Livingston detector with times relative to
▶ Inspiral
ember 26, 2015 at 03:38:53.648 UTC. This shows the full bandwidth, without the filtering used for Fig. 1. Top: The 90% credible
on (as in [57]) for a nonprecessing spin waveform-model reconstruction (gray) and a direct, nonprecessing numerical solution of 8
▶chirp mass, mass ratio, spin components
stein’s equations (red) with parameters consistent with the 90% credible region. Bottom: The gravitational-wave frequency f (left
) computed from the numerical-relativity waveform. The cross denotes the location of the maximum of the waveform amplitude,
roximately coincident with the merger of the two black holes. During the inspiral, f can be related to an effective relative velocity arXiv:1606.04856 [gr-qc]
▶Additional spin effect
ht axis) given by the post-Newtonian parameter v=c ¼ ðGMπf=c3 Þ1=3, where M is the total mass.
If not // orbital angular
VI. ASTROPHYSICAL▶IMPLICATIONS momentum:
evolutionary history of orbital plane
the observed black hole mergers
are further discussed in [5].
precession
The inferred black hole masses are within the range of
namically measured masses of black holes found in x-ray
The first observing period of Advanced LIGO provides
evidence for a population of stellar-mass binary black holes
liesAmplitude and phase to a modulation
ck hole, there is a probability of 4% that itâ
aries [76–80], unlike GW150914. For the secondary
contributing stochastic background that could be
in the
higher than previously expected [87]. Additionally, we
ited 3–5M ⊙ gap between observed neutron star and
▶
ck hole masses [76,77], Merger and ringdown
and there is no support for the
find the rate estimate of stellar-mass binary black hole
mergers in the local Universe to be consistent with the
mary black hole to have a mass in this range.
ranges presented in [88]. An updated discussion of the rate
Binary black hole formationPrimarily governed by final black hole mass and
▶ has been predicted through a
ge of different channels involving either isolated binaries
estimates can be found in [5].
A comprehensive discussion of inferred source param-
spin
dynamical processes in dense stellar systems [81]. At
sent all types of formation channels predict binary black
eters, astrophysical implications, mass distributions, rate
estimations, and tests of general relativity for the binary
e merger rates and black hole masses consistent with the
Masses and spins of binary fully determine mass and
▶ GW150914 [82–84]. Both
ervational constraints from
black hole mergers detected during Advanced LIGO’s first
observing period may be found in [5].
ssical isolated binary evolution through the common
spin of final black hole in general relativity
elope phase and dynamical formation are also consistent
VII. CONCLUSION
FIG. 4. Posterior probability densities of the masses, spins and distance to the th
h GW151226, whose formation time and time delay to two dimensional distributions, the contours show 50% and47
90% credible regions.
rger cannot be determined from the merger observation. LIGO has detected a second gravitational-wave the convention that msource
signal
events. We use 1 msource
2 , which produces the sharp
en our current understanding of massive-star evolution, from the coalescence of two stellar-mass black holes with
measured black hole masses are also consistent with any lower masses than those measured for GW150914. the contours follow lines of constant chirp mass (M source = 8.9+00
LVT151012, PublicExtrinsic Parameters arXiv:1606.04856 [gr-qc]
▶ Amplitude depends on masses, distance,
and geometrical factors
▶ Distance – inclination degeneracy
▶ Source location on the sky
FIG. 4. Posterior probability densities of the masses, spins and distance to the three events GW150914, LVT151012 and GW151226. For the
two dimensional distributions, the contours show 50% and 90% credible regions. Top left: component masses msource and msource for the three
Interf. B
events. We use the convention that m1 source m2source ▶ inferred primarily from 1 2
, which produces the sharp cut in the two-dimensional distribution. For GW151226 and
LVT151012, the contours follow lines of constant chirp mass (M source =▶8.9time 0.3 M of
+0.3
andflight
M source = 15.1+1.4
1.1 M for respectively).
GW150914 In all three
cases, both masses are consistent with being black holes. Top right: The mass and dimensionless spin magnitude of the final black holes.
Bottom left: The effective spin and mass ratios of the binary components. ▶ amplitude
Bottom and phase
right: The luminosity distanceconsistency
to the three events.
▶ Limited accuracy with two detector
a greater impact upon the inspiral. We find that smaller spins Observations for all three events are consistent with small
Interf. A are favoured, and place 90% credible bounds on the primary network
values of the effective spin: |ceff | 0.17, 0.28 and 0.35 at
spin a1 0.7 for GW150914, a1 0.7 for LVT151012, and▶ 90% probability
2-D 90% for GW150914,
credible region LVT151012
230 deg2and GW151226
a1 0.8 for GW151226. In the case of GW151226, we infer respectively. This indicates that large parallel spins aligned or
that at least one of the components has a spin of 0.2 at the (GW150914)
antialigned with the orbital angular momentum are disfavored.
99% credible level. ▶ 3-DIt may
uncertainty
be possiblevolume contains
to place tighter constraints on each com-
While the individual component spins are poorly con- ponent’s
~10 spinWay
5 Milky by using waveforms
equivalent that include the full effects
galaxies 48
PRL 116, 241102
strained, there are combinations that(2016)
can be better inferred. of precession [39]. This will be investigated in future analy-
The effective spin ceff , as defined in Equation 6, is a mass- ses.Testing GR
▶ Most relativistic binary pulsar known today
▶ J0737-3039, orbital velocity
▶ GW150914
▶ Strong field, non linear, high velocity regime
▶ “Loud” SNR -> coarse tests
▶ Waveform internal consistency check
▶ No evidence for deviation from General Relativity in waveform
▶ Bound on Compton wavelength (graviton mass)
▶ No evidence for dispersion in signal propagation
▶ More contraining than bounds from the solar system
▶ Less constraining than model dependent bounds from large scale
dynamics of galactic clusters
49Rate of BBH mergers
0.6
arXiv:1606.04856 [gr-qc]
Event Based total
GW150914
Astrophysical rate inference
0.5
▶ LVT151012
▶ Counting signals in experiment 0.4
GW151226
Estimating sensitivity to population of sources
R p(R)
▶ 0.3
▶ Depends on mass distribution
(hardly known) 0.2 FIG. 11. The posteri
ferred masses for our
LVT151012, and GW
0.1 a = 2.35 that correspo
infer the rate of BBH
the posterior, which a
0.0
median and 90% cred
Low statistics and variety of assumptions 10 1 100 101 102
▶ R (Gpc 3
yr 1
)
-> broad rate range more, due to the ob
cant signal GW151
▶ R ~ 9 – 240 Gpc-3 yr-1
FIG. 9. The posterior density on the rate of GW150914-like BBH, In particular, the 90
arXiv:1606.04856 [gr-qc]
Probability of N>10, N>35 and N>70
LVT151012-like BBH, and GW151226-like BBH mergers. The to 9–240 Gpc 3 yr
event based rate is the sum of these. The median and 90% credi-
▶ Previsously : R ~ 0.1 – 300 Gpc-3 yr-1 ble levels are given in Table II.
N>35
flat in log mass popu
law population distr
(electromagnetic observations and population modeling) With three signifi
and GW151226, all
N>10 ity, we can begin t
lescing BBHs. Her
the mass distributio
method that can fit
▶ Project expected number of highly significant events sented in future wo
fully in Appendix D
as a function of surveyed time x volume N>70 We assume that t
alescing binaries fo
with Mmin m2 m
distribution on the s
V x T relative to V x T of O1 50 m1 . With a = 2.35
distribution used in
is driven by a desiAstrophysics implications
▶ Relatively massive black holes (> 25 M) exist in nature
▶ Massive progenitor stars
=> low mass loss during its life
=> weak stellar wind
▶ Metallicity = proportion of elements heavier than He
▶ High metallicity => strong stellar wind
▶ => formation of progenitors
in a low metallicity environment
51Astrophysics implications
▶ Binary black holes form in nature
▶ Formation :
▶ Isolated binaries
▶ Dynamical capture (dense stellar regions)
▶ Detected events do not allow to identify formation channel
▶ Future : information on the spins can help
▶ Binary Black Holes merge within age of Universe at detectable rate
▶ Inferred rate consistent with higher end of rate predictions
(> 1 Gpc-3 yr-1)
5253
54
Vous pouvez aussi lire
