Jets from stellar tidal disruptions
by supermassive black holes
Dimitrios Giannios
Princeton University
HEPRO3, Barcelona, June 30
Galactic centers: some are active,
most are dormant
NGC 3115
AGN
Canada-France-Hawaii
Telescope
M87; NASA/Hubble
Sgr A*
starburst
galaxies
Ghez et al. 2005
Baldwin, Phillips & Terlevich 1981
Kormendy & Richstone 1995; Kauffmann et al. 2003
Rare glimpses to quiescent SMBHs from
tidal disruption of a star
When a wandering star finds
itself within
MBH 1/ 3
Rp  Rt ~ 
 R*
M
 * 
it is tidally disrupted

For solar type star
Rt  Rs 
2GMBH
, for MBH 108 M
2
c
Rate of TDEs~10-4-10-5 yr-1gal-1
(e.g. Magorrian & Tremaine 1999)
Rt
(Rees 1988; Phinney 1989; Evans & Kochanek 1989)
1. Disruption
2. Fall-Back
3. Circularization
and Accretion
5 / 3


M
t
*
Ý
M


fallback ~
t fallback t fallback 
t fallback ~ days
Figures Courtesy of Linda Strubbe
Tidal Disruption of a Star by a Supermassive Black Hole
Thermal “Flares” from Accretion Disk (Optical, UV, X-ray)
(e.g. Rees 1988; Ulmer 1997; Ayal et al. 2000; Strubbe & Quataert 2009, 2010)
Gezari et al. 2008
Galex D1-9
~10 Candidate Detections So Far by
- ROSAT All-Sky Survey (Komossa 2002)
- XMM Slew Survey (Esquej et al. 2007)
- Galex Deep Imaging (Gezari et al. 2009)
- SDSS Stripe 82 (van Velzen et al. 2010)
- PTF (Cenko et al. 2010)
Where there is accretion to BH, there are jets!
A substantial fraction of gravitational energy
may be channeled into relativistic jets
 Non-thermal signatures from TDEs
M87; NASA/Hubble
jets in galactic centers
stellar binaries
gamma-ray bursts
“Radio transients from Stellar Tidal Disruptions by
Massive Black Holes” Giannios & Metzger 2011
 jet ~ 0.1
jets?
jet ~ 10
jets?
Ýfallback
M


ÝEdd
M

ÝEdd
0.03M


t
energy released E rel ~ 0.1Maccc 2 ~ 1053 erg
jet
erg
energy in jets E jet ~  jet E rel ~ 10 51
0.01
Supernova or GRB!

Radio Transients by Stellar Tidal Disruptions by
Massive Black Holes
Jet Interaction with ISM
Prediction: radio synchrotron emission
peaking at tpeak ~ 1 – a few years:
 syn
 e 2   B 1/ 2  n ism 1/ 2
~ 25  
 
 GHz
0.1 0.01 10cm-3 
F syn
  j   B 1/ 2 jet 1 D 2
~ 2
   

 m Jy
0.010.01 10  1Gpc 
Blind radio surveys may detect
tens of TDEs per year
Giannios & Metzger 2011

And then came the … Event
GRB 110328A/Swift 1644+57
(Levan et al. 2011; Bloom, Giannios et al. 2011; Burrows et al. 2011)
• Triggered Swift BAT on
March 28, 2011
/X-ray
• Triggered BAT 3 more times
over next few days
• Remains bright in X-rays
• IR and Radio Brightening
IR-Optical
• Host galaxy at z = 0.35
• NOT a (normal) GRB
- duration ~ months
•NOT a normal AGN
- no evidence for AGN or
past activity
Radio
Levan et al. 2011
- low luminosity
Compact Host Galaxy at z = 0.35
Levan et al. 2011
 SMBH origin
• ~100 s variability and
7
bulge mass Mb < 1010 M  MBH< 10 M
• LX > 1047 erg s-1 > 100 LEdd 
super-Edd accretion and/or beaming
Levan et al. 2011
• Within < 150 pc of galactic center
Not an AGN
“Mini Blazar” Hypothesis
Bloom, Giannios et al. 2011; see also Burrows et al. 2011, …
radio
t ~ 3 days
X-rays
• synchrotron self-absorption  Rradio > 1016 cm  vej ~ c  external shock from ISM
interaction (Giannios & Metzger 2011)
• X-ray variability  RX ~ c tX 2 ~ 3x1014 (/10)2 cm  “internal” process (e.g.
shocks, reconnection)
jets from TDEs: (Rough) energetics and rates
• observed (0.3-10) keV fluence Ex,iso~2x1053 erg
▫ ~ x3 for likely bolometric corrections
▫ ~ x2 for radiative efficiency of flow
Ek,iso ~ 1054 erg
or Ek,true ~ 1051 erg depending on beaming
• Rates very uncertain: 1 event in 7 years of Swift
operation (Ωfov=4π/7 sr); observable out to z~0.4-0.8
Robs ~ 10-9 - 10-8 gal-1yr-1 or Rtrue ~ 10-6 – 10-5 gal-1yr-1
~3-30% of ALL TDEs accompanied by powerful jets?
Predictions
Updated X-ray light curve
• X-ray emission will continue to fade
over the next few months (no later
re-brightening/repetition)
• If jet turns off, thermal disk
emission may become visible (?)
• GHz Radio emission will remain
bright for ~ years
• relativistic motion observable with
VLBI (?)
Implications
Sw 1644+57
blazar
•
Detections: Future TDE detections
with blind radio surveys
IR/radio
Giannios & Metzger 2011
•
•
Jet physics: B fields responsible
for accelerating AGN jets can be
generated in situ (e.g. via disk dynamo)
TDE jets may accelerate UHECRs
(Farrar & Gruzinov 2009), but production
rate may be insufficient
optical/UV/ X-ray