Stellar Tidal Disruption by a Supermassive Black Hole Binary

Angelo Ricarte In collaboration with Priya Natarajan and Jane Lixin Dai

What is a Tidal Disruption Event?

•Debris  creates  transient  accre-on  disk  —>  flare  •Stars  come  from  far  away  via  two  body  relaxa-on  (Magorrian  and  Tremaine  1999)  •10-­‐5  events/yr/galaxy  (e.g.,  Donley  et  al.  2002)

Rees  (1988)

Thousands are soon to be detected

Komossa  (2004)

•X-­‐ray  luminosi-es  peak  up  to  1045  erg/s,  then  decline  by  factors  of  1000-­‐6000.    (See  Komossa  2012  for  a  recent-­‐ish  review)  

•Today,  we  know  of  30-­‐40  (hSp://astrocrash.net/resources/tde-­‐catalogue/)  

•We  expect  thousands  from  mul-  wavelength  surveys.    (Strubbe  &  Quataert  2011)

• Presence  of  a  binary  can  change  the  -dal  disrup-on  rate  by  many  orders  of  magnitude,  depending  on  separa-on  (Chen  et  al.  2007,  2009)  

• Liu  et  al.  (2009)  predict  a  modified  light  curve  with  truncated  power  law  and  accre-on  islands.

What about a SMBH binary?

TDE  by  SMBH  binary?  Liu  et  al.  (2014)

Truncation

“Accretion Islands”

Goal: Understand debris behavior

• Start  with  star  on  coplanar  parabolic  orbit  at  -dal  disrup-on  radius.  

• Use  Runge-­‐KuSa  4(5)  integra-on  for  individual  par-cles.  

• Non-­‐interac-ng  par-cles,  no  GR.  

The Setup

Are  there  observables  that  can  be  inverted  back  to  physical  parameters?

Mass Fallback Rates

Trunca-on:    stream  misses  -dal  disrup-on  radius.      

Accre-on  Islands:    secondary  passes  parallel  to  stream  and  primary.

Close binaries can inhibit flares

Theorists  overpredict  the  rate  of  -dal  disrup-ons  by  1-­‐2  orders  of  magnitude  (Magorrian  &  Tremaine  1999,  Wang  &  MerriS  2004).      

Perhaps  perturber  objects  can  reduce  detectability.

Accretion by Secondary BH?

Possible  flares  when  crossing  streams?      

Hydrodynamics  might  help.

New stream crossings

Crossings  should  dissipate  energy  and  may  be  important  in  determining  accre-on  onto  the  secondary.  

Shiokawa  et  al.  (2015)

Complex Large Scale Structure

Large  surface  areas  may  have  implica-ons  for  reprocessed  emission.  

Could  broad  emission  lines  be  a  signature  of  a  binary?

Conclusions

• Fallback  rates  (and  maybe  spectra?)  encode  informa-on  about  the  geometry  of  the  black  hole  binary.  

• Close  secondary  perturber  objects  may  decrease  the  detectability  of  -dal  disrup-on  flares.  

• On  my  to-­‐do  list:  

• Complete  analysis  of  fallback  rate  curves.    Move  to  Fourier  space?  

• Explore  prospects  of  reprocessed  emission  as  signature  for  binary