New physics and the Black Hole Mass Gap
Djuna Lize Croon (TRIUMF) University of Michigan, September 2020 [email protected] | djunacroon.com GW190521
LIGO/Virgo’s biggest discovery yet: the impossible black holes Phys. Rev. Le . 125, 101102 (2020). From R. Abbo et al. (LIGO Scien fic Collabora on and Virgo Collabora on), GW190521
LIGO/Virgo’s biggest discovery yet: the impossible black holes Phys. Rev. Le . 125, 101102 (2020). From R. Abbo et al. (LIGO Scien fic Collabora on and Virgo Collabora on), GW190521
LIGO/Virgo’s biggest discovery yet: the impossible black holes … let’s wind back a bit “The Stellar Binary mergers in LIGO/Virgo O1+O2 Graveyard” Adapted from LIGO-Virgo, Frank Elavsky, Aaron Geller “The Stellar Binary mergers in LIGO/Virgo O1+O2 Graveyard”
Mass Gap?
“Mass Gap” Adapted from LIGO-Virgo, Frank Elavsky, Aaron Geller What populates the stellar graveyard?
• In the LIGO/Virgo mass range: remnants of heavy, low-metallicity population-III stars • Primarily made of hydrogen (H) and helium (He)
• Would have existed for z ≳ 6, M ∼ 20 − 130 M⊙ • Have not been directly observed yet (JWST target)
• Collapsed into black holes in core-collapse supernova explosions. (Or did they?) • We study their evolution from the Zero-Age Helium Branch (ZAHB)
Min = 120M Min = 40M Min = 70M
109 Stellar evolution simulated with MESA 12778*
108 102 103 104 105 106 107
*Paxton et al, arXiv:1710.08424 [astro-ph.SR]
Min = 120M Min = 40M Main nuclear reactions: Min = 70M
109 + 12C(α, γ)16O Stellar evolution simulated with MESA 12778*
108 102 103 104 105 106 107
*Paxton et al, arXiv:1710.08424 [astro-ph.SR]
109 Stellar evolution simulated with MESA 12778*
108 102 103 104 105 106 107
*Paxton et al, arXiv:1710.08424 [astro-ph.SR]
Min = 120M Min = 40M Min = 70M
109 Stellar evolution simulated with MESA 12778*
108 102 103 104 105 106 107
*Paxton et al, arXiv:1710.08424 [astro-ph.SR] Pair-instability
• The high temperatures of the pop-III stars lead to electron-positron + − 10 pair creation in the thermal plasma via γγ → e e (2me ≃ 10 K)
• Stars supported by radiation Relativistic electrons pressure Γ = ∂P/∂ρ ≈ 4/3 ( )s
• Instability occurs for Γ < 4/3 Ion pressure 109 ‣ Non-relativistic electrons destabilize the star γγ → e+e− Boltzmann suppressed ‣ Rapid thermonuclear burning 102 103 104 105 106 of 16O follows
Min = 120M Min = 40M Min = 70M
109 Stellar evolution simulated with + − 10 MESA 12778* γγ → e e (2me ≃ 10 K) softens the equation of state
108 102 103 104 105 106 107
*Paxton et al, arXiv:1710.08424 [astro-ph.SR] Extremely massive (P)PISN stars ( ) Min > 200 M⊙
Very, very massive stars
(Min > 90 M⊙)
Very massive stars
(Min > 50 M⊙)
Adapted from Renzo et al [2002.05077] Pair-instability and the BHMG
−3 Z = Z⊙/10 = 1.42 × 10
60
40
20
0 40 50 60 70 80 90 DC, McDermott, Sakstein arXiv:2007.00650 [hep-ph] Known physics dependence of the BHMG
• Astrophysical + nuclear + numerical uncertainties
• Most important uncertainty: 12C(α, γ)16O rate • Using updated deBoer et al rate, BHMG found at +0 51−4 M⊙
deBoer et al arXiv:1709.03144 [hep-ex] Farmer, Renzo, de Mink, Fishbach, Justham arXiv:2006.06678 [astro-ph.SR] Farmer, Renzo, de Mink, Marchant, Justham arXiv:1910.12874 [astro-ph.SR] Known physics dependence of the BHMG
• Astrophysical + nuclear + numerical uncertainties
• Most important uncertainty: 12C(α, γ)16O rate • Using updated deBoer et al rate, BHMG found at +0 51−4 M⊙
deBoer et al arXiv:1709.03144 [hep-ex] Farmer, Renzo, de Mink, Fishbach, Justham arXiv:2006.06678 [astro-ph.SR] Farmer, Renzo, de Mink, Marchant, Justham But GW190521?! arXiv:1910.12874 [astro-ph.SR] Sam McDermott Jeremy Sakstein
What about new physics?
Eric Baxter Maria Straight DC, McDermott, Sakstein arXiv:2007.00650 [hep-ph] DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc] Sakstein, DC, McDermott, Straight, Baxter arXiv:2009.01213 [gr-qc]
18 DC, McDermott, Sakstein arXiv:2007.00650 [hep-ph] The BHMG and new physics DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc]
• Scenario 1: new, light particles coupled to material in the star introduce new loss channels
• Case studies: • the electrophilic axion ℒae = − igaeψ¯eγ5ψea (will also work with 26 2 α26 ≡ 10 gae/4π for convenience)* 1 ˜μν • the photophilic axion ℒaγ = − gaγaFμν F (will also define 10 4 g10 ≡ 10 gaγ GeV) 2 ϵ mA′ μν μ • the hidden photon ℒ = − F′ F + A A (and define nothing) A′γ 2 μν 2 μ *Interesting in light of the XENON1T excess, arXiv:2006.09721 [hep-ex] DC, McDermott, Sakstein arXiv:2007.00650 [hep-ph] The BHMG and new physics DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc]
• Scenario 1: new, light particles coupled to material in the star introduce new loss channels
Extra scenarios: large extra dimensions (d = 4 + 2) and neutrino • Case studies: magnetic moment work through essentially the same mechanism • the electrophilic axion ℒae = − igaeψ¯eγ5ψea (will also work with 26 2 α26 ≡ 10 gae/4π for convenience)* 1 ˜μν • the photophilic axion ℒaγ = − gaγaFμν F (will also define 10 4 g10 ≡ 10 gaγ GeV) 2 ϵ mA′ μν μ • the hidden photon ℒ = − F′ F + A A (and define nothing) A′γ 2 μν 2 μ *Interesting in light of the XENON1T excess, arXiv:2006.09721 [hep-ex] DC, McDermott, Sakstein arXiv:2007.00650 [hep-ph] Energy loss due to electrophilic axions
• Semi-Compton scattering, e + γ → e + a: 2 6 40 ζ6αEMgae YeT 6 erg T � = F ≃ 33 α Y T F T8 ≡ • sC 2 4 deg 26 e 8 deg ( 8 ) π mNme g⋅s 10 K 2 d3p F = f −(1 − f −), where f − is the Fermi-Dirac distribution • deg 3 e e e ne ∫ (2π) • Bremsstrahlung, e + (Z, A) → e + (Z, A) + a: 2 2 5/2 32 αEMgaeρT 5/2 erg ρ �b,ND = Fb,ND ≃ 582 α26 ρ6 T Fb,ND ρ6 ≡ 3 8 ( 6 −3 ) - 45 π 2 7/2 g⋅s 10 g cm 2 mNme π Z2 α2 g2 T4 erg � = EM ae F ≃ 10.8 α T4 F • b,D 2 b,D 26 8 b,D 60 A mNme g⋅s DC, McDermott, Sakstein arXiv:2007.00650 [hep-ph] Energy loss due to electrophilic axions
• Semi-Compton scattering, e + γ → e + a: 2 6 40 ζ6αEMgae YeT 6 erg T � = F ≃ 33 α Y T F T8 ≡ • sC 2 4 deg 26 e 8 deg ( 8 ) π mNme g⋅s 10 K 2 d3p F = f −(1 − f −), where f − is the Fermi-Dirac distribution • deg 3 e e e ne ∫ (2π) • Bremsstrahlung, e + (Z,0A<) F→deg • Primakov effect (Z, A) + γ → (Z, A) + a 2 7 2 2 gaγT kS 2 erg kS 2 � = f[(k /2T) ] ≃ 283.16 g2 T7ρ−1 f[(k /2T) ] aγ 4π2ρ ( 2T ) S g ⋅ s 10 8 3 ( 2T ) S • With Debye momentum 8 2 k ρ 6 S = 0.166 3 Y Z2 • j j 4 ( ) 3 ∑ Screened at high 2T T8 j 2 T and low ρ 0 0 50 100 150 200 DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc] DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc] Energy loss due to hidden photons • Plasma production, dominated by longitudinal modes (in a non- relativistic plasma) 2 2 ω3 2 2 ω2T 2 ϵ mA′ p ϵ mA′ p 3 erg Z ϵ mA′ �A′ = ≃ ≃ 1.8 × 10 T8 4π ρ eωp/T − 1 4π ρ g ⋅ s A ( 10−7 meV ) In the limit ωp ≪ T 4παEMne Z • Where photons have plasma mass ωp ≃ ≃ 654eV ρ3 me A DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc] Loss rates 1010 109 108 106 104 6 108 102 Electrophilic axion: �ae ∝ T 108 109 106 104 Photophilic axion: 4 108 �aγ ∝ T 102 109 106 5 108 10 Hidden photon: �A′ ∝ T 100 101 102 103 104 105 106 107 DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc] Example track of Min = 55 M⊙ progenitor Implications of enhanced losses 60 63 50 62.7 2× 108 3× 108 4× 108 40 108 109 1010 Implications of enhanced losses The wind losses 60 are a bit lower The pulsation losses 63 are much lower 50 62.7 2× 108 3× 108 4× 108 40 108 109 1010 What does the extra energy loss do? 3. Greater energy losses lead to Min = 63 M⊙ shorter He-burning phases 2.5 2. Extra dissipation scales linearly with α26 0.17 0.16 0.15 0.14 0.13 Less time for 12C(α, γ)16O: 0.12 C/O is larger at the time of 0.11 0 20 40 60 80 100 helium depletion (HD) Helium burning The BHMG and new physics Carbon burning Oxygen burning → Enhanced losses, larger C/O at HD Enhanced losses → greater progenitors collapse → larger black holes Adapted from Farmer, Renzo, de Mink, Fishbach, Justham [2006.06678] 60 60 50 50 40 40 30 30 20 20 10 10 0 0 20 30 40 50 60 70 GW150914 GW151012 GW151226 GW170104 GW170608 GW170729 GW170809 GW170814 GW170818 GW170823 DC, McDermott, Sakstein arXiv:2007.00650 [hep-ph] 60 60 50 50 40 40 30 30 In strong tension with stellar cooling constraints but interesting complementary 20 probe in light of XENON1T 20 10 10 0 0 20 30 40 50 60 70 GW150914 GW151012 GW151226 GW170104 GW170608 GW170729 GW170809 GW170814 GW170818 GW170823 DC, McDermott, Sakstein arXiv:2007.00650 [hep-ph] 50 50 40 40 30 30 20 20 10 10 0 0 20 30 40 50 60 70 GW150914 GW151012 GW151226 GW170104 GW170608 GW170729 GW170809 GW170814 GW170818 GW170823 DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc] 70 70 60 60 50 50 40 40 30 30 20 20 10 10 0 0 30 40 50 60 70 GW150914 GW151012 GW151226 GW170104 GW170608 GW170729 GW170809 GW170814 GW170818 GW170823 DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc] New physics and the black hole mass gap 160 160160 160160 160 140 140140 140140 140 120 120120 120120 120 100 100100 100100 100 80 8080 8080 80 60 6060 6060 60 40 4040 4040 40 20 2020 2020 20 0 20 40 60 80 100 0 1 2 3 4 5 0 1 2 3 4 5 6 4 �ae ∝ T �aγ ∝ T �A′ ∝ T Potentially large shifts of the mass gap! DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc] Heavier degrees of freedom? Heavier degrees of freedom may instead be thermalized in the core 1010 Then, they may give rise to an instability in the same way that electron-positron pairs do 109 Equilibration time (vector): −1 −1 2 −mA′ /Tc t ≃ Γ ≃ ϵ σ n e A′ A′ ( T e ) 108 so for ϵ = 3 × 10−12, we find 5 tA′ ≃ 10 years, a timescale similar to the lifetime of helium burning 100 101 102 103 104 105 106 107 108 109 DC, McDermott, Sakstein arXiv:2007.07889 [gr-qc] Heavier degrees of freedom? May probe this parameter space ∼ 107K ∼ 108K Adapted from Ann, Pospelov, Pradler, Ritz arXiv:2006.13929 [hep-ph] Sakstein, DC, McDermott, Straight, The BHMG and new physics Baxter arXiv:2009.01213 [gr-qc] Straight, Sakstein, Baxter, in progress • Scenario 2: screened modified gravity (MG) • Increased local strength of gravity → need larger pressure gradient to maintain hydrostatic equilibrium → larger core temperature at fixed density • Pair instability is exacerbated →Lighter black holes 109 • Decreased local strength of gravity works in reverse Heavier black holes → 108 102 103 104 105 106 107 GW190521, the impossible black holes … and Beyond the Standard Model physics |||| |||| ||| | | | || | | | | | | || 50 60 70 80 90 Sakstein, DC, McDermott, Straight, Baxter arXiv:2009.01213 [gr-qc] Looking ahead… Posterior PDFs using the first 4 BBH mergers, and assuming a power law mass distribution, −α p(m1 |α) ∝ m1 With the complete O3 data set (and beyond), the field of black hole population studies will really take off! from Fishbach & Holz, arXiv:1709.08584 [astro.ph] To conclude, • Gravitational waves offer an exciting new opportunity to study open questions in particle astrophysics and cosmology • Binary mergers allow for black hole population studies • The black hole mass gap is an exciting probe of new physics, which will come into focus in the next few years • GW190521 constitutes an intriguing puzzle which could be (partially) explained by BSM physics 40 Thank you! …ask me anything you like! [email protected] | djunacroon.com 41 Helium burning rates as a function of T 105 100 10-5 10-10 10-15 10-20 10-25 Source: STARLIB catalogue 10-30 108 109 1010 Farmer, Renzo, de Mink, Fishbach, Justham arXiv:2006.06678 [astro-ph.SR] (Kunz is currently used in STARLIB) 2. 1.5 1. 0.5 108 109 1010 Farmer, Renzo, de Mink, Fishbach, Justham arXiv:2006.06678 [astro-ph.SR] (Kunz is currently used in STARLIB) 2. 1.5 1. 0.5 108 109 1010 Large black hole in LB-1? • Last year, a 70 M⊙ black hole was reported in a binary with a high- metallicity smaller star (from the radial velocity variability of the Hα emission line, suggesting an accretion disk) • It was suggested (1911.12357) that it was formed due to the core- collapse of a high metallicity progenitor with reduced stellar winds • However, those simulations did not include pulsations (they were stopped at carbon burning) • The observation has since also been disputed (1912.04185 and 1912.03599) - apparent shifts instead originate from shifts in the luminous star’s Hα absorption line Binary merger events (M1≈M2) • >50 LIGO/Virgo observations • 2017 Nobel Prize in Physics • Can be used to learn about new physics in various ways • Most GW radiation from the inspiral phase, ending in fISCO Image credit: LIGO collaboration • Solvable in a (v/c) expansion → Weak gravity, small velocity 46 Compact object merger sensitivity • Best detection prospects for fmin < fpeak ∼ fISCO < fmax SNR ≥ 8 • Defines an CO sensitivity band • Sensitivity determined by masses, compactness and luminosity distance Giudice, McCullough, Urbano [JCAP, 1605.01209] 47 What can we learn from the inspiral waveform?* A lot, for example, Hints of mass-gap mergers: 1. Component masses • GW190814 → downgraded mass gap probability <1% → 2. Tidal effects → equation of state publication June ‘20 • GW190924 (24 September ‘19) 3. Dynamical friction → environmental effects • GW190930 (30 September ’19) 4. Long-range (dark) forces → BSM effects 5. Extra dissipation channels → BSM effects 6. Redshift distribution of events → age of objects Image credit: LIGO collaboration 7. “Hair”: multipolar metric deviations (EMRIs) → tests of GR So what about new physics? May show up in various ways, I will give a (unabashedly biased) selection of examples *Further information could come (for example) from multi-messenger signals (or absence thereof), or post-merger quasi-normal modes or “echoes”