1. Star-Massive Black Holes Encounters
J.-P.Luminet
Observatoire de Paris (LUTH)
Tidal Disruption Events
Esa, Madrid 2012

2. Supermassive black holes (M > 106 MS) in active galactic nuclei
quasars
radiogalaxies
Supermassive black holes (M > 106 MS) in active galactic nuclei
Seyfert 2

3. Massive black holes (M > 106 MS) in quiescent galactic nuclei
Sagittarius A*
2,7 106 MS < M < 3,5  106 MS)

4. Intermediate mass black holes (103 < M < 106 MS)
in globular clusters
M15
4000 MS
G1/M31 MS

5. The « octopus » model for AGN
Luminet (1986)

6. BH’s gravitational radius
Characteristic distances
Accretion radius
Collision radius
Hills limit
108 MO
Ablation radius
Tidal radius
BH’s gravitational radius 6

7. Tidal field = relative acceleration between elements of matter
Newtonian tidal field
Tidal field = relative acceleration between elements of matter
tidal potential
tidal tensor
deviation tensor

8. (planet-satellite couple in circular orbit)
• For incompressible homogeneous bodies
• static field
(planet-satellite couple in circular orbit)
Edouard Roche
Roche limit (1847)

9. • incompressible bodies in dynamical field
(asteroid-black hole encounter in parabolic orbit)
Luminet & Carter (1986)
Kostic et al. (2009)
Cigar-like regime
Disk-like regime
0.16 RT ≤ Rp ≤ RT
Rp ≤ RT

10. Luminet et al. 1982-1986 : « affine » model
• compressible bodies
in dynamical field
(star-black hole encounter in parabolic orbit)
Luminet et al : « affine » model
Non-disruptive regime
Oscillating Riemann ellipsoid
=> variable star ?

11. From equilibrium to stellar disruption
Compare : timescale of varying tidal field / internal timescale of the star
Far from the tidal radius :
Star adjusts its equilibium configuration
Close to and inside the tidal radius :
Pionneer work : Hills, 1975 ; Frank & Rees, 1976
Strongly dynamical tidal field => Star cannot respond

12. the penetration factor
Parabolic orbit
Crucial parameter :
the penetration factor
Carter & Luminet (Nature, 1982)
Tidal radius
Black hole RP RT

13. Slight penetration (b ~ 1) in the tidal radius
Disruption process in the ellipsoidal model (Luminet & Carter, 1986)
« cigar-like » configuration after leaving the tidal radius

14. Disruption process reproduced by hydrodynamical simulations
Slight penetration
in the tidal radius
Disruption process reproduced by
hydrodynamical simulations
Ejected matter
« cigar-like » configuration after leaving the tidal radius
« S-like » configuration at the periastron

15. Lidskii & Ozernoy (1979), Rees (1988)
Accretion of stellar debris (50%)  Tidal Flares
Lidskii & Ozernoy (1979), Rees (1988)
Tidal radius
Massive black hole

16. UV flare in NGC 4252 (Renzini et al. 1995)
X-ray flare in RXJ
(Komossa & Greiner, 1999)
UV flare in NGC 4252 (Renzini et al. 1995)

17. Giant X-UV luminous flares
Detection (ROSAT, Chandra, Galex…) of X-UV flares from (non active) galactic nuclei

18. X-UV-optical luminous flares
Detection (Chandra, Galex, Pan-starrs…) of flares from (non active) galactic nuclei
(Komossa et al., Saxton et al. , Esquej et al., Gezari et al., etc.)
« Relativistic » Tidal Flares
Detection (Swift) of hard-X flares (Lx ~1047 ergs)
(Zauderer et al. 2011, Cenko et al. 2012)
Relativistic jets from tidal ejecta ?

19. (Carter & Luminet, Nature, 1982)
The Pancake Effect
(Carter & Luminet, Nature, 1982)
Fixed compressive principal direction of the tidal tensor in the « vertical » direction ==>
For deep penetration ( > 3)

20. The « Rolling Mill » Effect
Cartoon version
fixed compressive point after periastron
But relativistc velocity at periastron => almost instantenous flattening

21. Disruption process in the ellipsoidal model (Luminet & Carter, 1986)
Deep penetration (b > 3) in the tidal radius
Disruption process in the ellipsoidal model (Luminet & Carter, 1986)

22. Explosive stellar disruption ?
Compression and heating strongly dependent from the penetration factor
Maximum values for an ideal gas with polytropic index 5/3 :
Conditions required for explosive thermonuclear reactions

23. Detonation of metals (C, N, O, …) by radiative proton captures (Luminet & Pichon 1989)
Helium detonation by triple alpha (Pichon 1985)

24. Tidally induced supernovae?
Luminet, 1986
Rosswog et al., 2008
A special type of GRB ?
Carter, 1992
Lu et al. 2008; Gao et al. 2011

25. The pancake triangle (solar type stars)
Star enters the Black hole
Black hole enters the star
107 K
108 K
109 K
log (
No disruption
log(M•/M*)

26. Shock waves in stellar pancakes
(Brassart & Luminet, )

27. Problematics
Stellar pancakes calculated in the affine model (Luminet et al )
==> Elliptical deformations of the star
• Stellar pancakes calculated by 3D hydro
(Bicknell & Gingold 1983; Laguna et al. 1993; Fulbright 1996)
==> SPH method (uses artificial viscosity to simulate shock waves)
N.B. : Generalized affine model (Ivanov et al )

28. Due to shock waves occuring during the phase of vertical direction ??
Disagreement : compression of the stellar core less than in the affine model:
max ~ 1.5 for  < 10
max ~ const for  > 10
Due to shock waves occuring during the phase of vertical direction ??
Or bad treatment (SPH) of shock waves ?

29. New Hydrodynamical Model Euler eqs. + Godunov methods
1D approximation
valid from the tidal radius to periastron
Principal axes of the tidal tensor

30.  = 7 velocity Phase1: collapse Tidal radius periastron
max.compression
Phase1:
collapse

31.  = 7 velocity Phase 2: bounce max.compression Subsonic expansion
Subsonic collapse
Supersonic collapse
Subsonic expansion

32. collapse Shock  = 7 density (after bounce) Tidal radius periastron
max.compression
and bounce
Shock
(after bounce)

33.  = 7
temperature
shock

35. = 15
shock 1
(before bounce)
velocity
shock 2
(after bounce)

36.  = 15
shock 1
(before bounce)
density
shock 2
(after bounce)

38. maximum central density
maximum central temperature

39. Shock-driven maximum temperature
 = 10
Shock-driven maximum temperature

40. Number of disruption events:
Wang & Merritt (2004), Tal (2005) BH binaries : Chen et al (2009)
UV/X/gamma-ray flares

41. Modelisation of Gamma-Ray Bursts
jet
Long GRB
Short GRB 41

42. • g-ray transients Swift J1644+57 and Swift J2058+05 (Zauderer 2011, Cenko 2012)
interpreted as a relativistic outflow from transient accretion onto a 106 Ms black hole
• GRB (long ~100 s) without SN remnant : disruption of a WD by an intermediate mass BH ? (Lu et al. 2008)
• A new class of g-ray bursts from stellar disruptions by IMBH ? (Gao et al., 2010)
 From a total of 328 Swift GRBs with accurate measured durations and without SN association, 25 GRBs satisfying the criteria for GRB type bursts…

43. Relativistic tidal field
Luminet & Marck, 1985
E = specific total energy
L = specific angular momentum
for parabolic orbits :
E = 1

44. Precession effect : self-crossing orbit

45. Double point inside the tidal radius:
Luminet & Marck, 1985

46. Double point inside the tidal radius
Brassart & Luminet, 2011
Double point inside the tidal radius
Several compressions

47. Multi-pancake effect and X/ bursts
• Multi-peak structure and timescales compatible with GRB (and others ?)

48. Recent hydro models …
• 3D simulations coupling hydrodynamics and nuclear network (Guillochon et al., 2011):
Confirm the occurrence of tidally induced supernovae
• Red giants / BH interactions (Mac Leod et al., 2012):
Tidal stripping of atmosphere
• White dwarfs / IM BH strong encounters (Rosswog et al. 2010, Hass et al. 2012):
Confirm nuclear ignition (e.g. helium detonation)

49. Supermassive BH > 108 MS
Analogy with stellar collisions
Around a 109 MS black hole, the typical collisional velocities are > 5000 km/s within a distance 0.1 pc from the black hole
b = vcoll/v*
crushing factor
b = RT/Rp
Massive BH ( MS)
Supermassive BH > 108 MS
Glob. Clusters, GN, Seyfert
Quasars, Giant elliptical …

50.  : disruption /  : pancake effect
High velocity head-on collisions, polytropes 5/3
Barnes, 2003
Makino, 1999

51. The End