1. Tidal Disruption Events
Andrew Levan
University of Warwick

2. rT = R* (MCO / M*)1/3
Bound, falls back
Unbound,
escapes

3. rT = R* (MCO / M*)1/3
Bound, falls back
Unbound,
escapes
WD, NS, BH

4. rT = R* (MCO / M*)1/3 Bound, falls back Unbound, escapes
Asteroid, planet, star (MS, WD, RG, NS)
WD, NS, BH

5. rT = R* (MBH / M*)1/3
Rs ~ 2 GM / c2

6. rT = R* (MBH / M*)1/3 tmin ~ R*3/2 MBH1/2 Duration of event:
WD = hours
MS = months - years
RG = decades - centuries

7. Tidal disruption events – around massive black holes
Probe of the existence of massive BHs in faint galaxies, even globular clusters?
Timescales much more rapid than in AGN to probe accretion physics
Contribution to the AGN LF
Reverberation mapping of circumnuclear material
Signposts of gravitational wave sources
Signatures of merging BHs (disruption rates 1 per decade)
Possible accelerators of ultra-high energy cosmic rays

8. Finding TDEs Nuclear X-ray and/or optical flares
Hot blackbody components (UV, soft X-ray spectrum)
Characteristic decay t-5/3
Rates /yr/L* galaxy (0.1-1% of core collapse SNe rate)

9. Except…… Nuclear AGN and multiple variable X-ray sources.
Often relatively poor X-ray cadence (don’t realise until it is late)
X-ray’s often give poor positions compared to optical/radio
Nuclear supernovae more common than TDEs
Some UV bright at early times, extinction always a concern.
Nuclei are bright, and often excluded from optical transient searches due to difficulties in subtractions
Contributions from disc, wind etc complicate the lightcurve.

10. Early work(X-ray’s) Halpern, Gezari & Komossa 2004 ApJ 604 572
Komossa & Bade 1999 A&A

11. Recent work(X-ray’s)
Saxton et al A&A

12. Recent work (optical)
Wavelength (A)
Gezari et al Nature

13. Recent work (optical) Opt UV ASASSN-14ae (200 Mpc) HST (13 June 2014)
Holoein et al arXiv:

14. Why not both? PS1-10jh NUV X-ray Just disc/wind temperature?
Different components at different times?
Lodato & Rossi 2011 MNRAS

15. Why not both? ASASSN-14ae NUV X-ray Just disc/wind temperature?
Different components at different times?
Lodato & Rossi 2011 MNRAS

16. SGRB
LGRB
ULGRB
TDE?
SGR
Galactic Sources
Levan et al ApJ

17. Swift J1644+57 Levan et al. 2011 Science 333 199
Levan et al Science , Bloom et al Science

18. Levan et al. 2011, Cenko et al. 2012, Brown et al. in prep

19. In context
Levan et al. 2011, Cenko et al. 2012

20. Host Galaxies All 3 events consistent with nuclei of their hosts
Levan et al Science
All 3 events consistent with nuclei of their hosts

21. Bloom et al 2011 Science

22. Relativistic outflow Swift J1644+57
Zauderer et al Nature

23. Switch-off
Swift J

24. Switch-off
Swift J

25. Implications
Host galaxies with MB <-18 have massive black holes in their cores
A unique probe of galactic nuclei
Miller & Gultekin 2011 ApJ ; Berger et al arXiv

26. Jets are rare 3 relativistic TDEs at z=0.35, 0.89, 1.19
All well detected by Swift
No other compelling candidates in BAT archive
Jetted TDE rate ~10-6 “classical TDEs”
Jet angles much larger than this
Requirements for jet creation unclear

27. UV/optical X-ray Relativistic PS1-10jh D23H-1 D3-13 D1-9 PS1-11af
ASASSN-14ae
PTF09ge
PTF09axc
PTF09djl
UV/optical
NGC5905
RXJ
RXJ
NGC3599
SDSSJ
TDXFJ
SDSSJ
2MMMi J
SDSSJ
X-ray
Swift J
Swift J
Swift J
Ultra-long GRBs?
Relativistic
PTF10iya
Are these all TDEs? Why are they so diverse?
A naming convention ala SNe is urgently needed (NT-X 2014A?)

28. Summary and next steps
TDEs are exceptionally useful astrophysical probes
But: Candidates to date are extremely diverse.
X-ray detected events have poor optical follow-up
Many optically detected events don’t have detectable X-ray’s
Jetted events appear to be extremely rare
We still need to understand the physical mechanisms at play to cleanly identify TDEs from other transients, and deploy them as probes.
Multiwavelength follow-up in close to real time is essential
Rule out SNe
Tie events to SMBH as tightly as possible
Map emission processes