1. Modeling Sgr A* Flares: Nonthermal Processes in an Outflow
Sera Markoff (MIT)
In collaboration with Heino Falcke
Also Feng Yuan & Peter Biermann

2. Evidence for jets in Sgr A*
Sgr A* is the weakest of the LLAGN class
VLBA sub-arcsecond surveys, some multiwavelength (e.g., Nagar, Wilson, Falcke, Filho, etc.) find:
Radio cores have flat/inverted “signature” like AGN
In brightest sources, pc-scaled jet(s) resolved
Occam’s razor: likely all flat spectra are jets
Same radio spectrum seen in hard state X-ray binaries, only 2 cases resolved but jets considered part of standard model for hard state

3. (Bietenholz, Bartel & Rupen, 2000)
Sgr A*/M81*
M81* is a very similar source to Sgr A*, and it has an imaged radio jet
(Bietenholz, Bartel & Rupen, 2000)
L ~ (1-4) x 103 AU
Scaled to Sgr A* power and relative distances
L ≤ 1 AU!

4. Phenomenology of Flares
Radio
Submm IR
X-ray

5. Big Flare (50x)
(Markoff et al. 2001)

6. Big Flare (50x)
(Markoff et al. 2001)

7. “Average Daily Flares (5-10x)”
Now IR data exists (Genzel et al., Ghez et al., 2003)
Markoff & Falcke, in prep.

8. “Average Daily Flares (5-10x)”
Now IR data exists (Genzel et al., Ghez et al., 2003)
Markoff & Falcke, in prep.

9. Self-absorption  Model Degeneracy

10. Self-absorption  Model Degeneracy F 

11. VLBA mapping as new constraint
(Falcke & Markoff 2000, A&A ; Bower et al. 2004, Science)

12. VLBA map predictions
Z (mas) F
For one 
FWHM

13. VLBA map predictions @ 43 GHz
Input quiescent model

14. VLBA map predictions @ 43 GHz
Jet ~ perpendicular to scattering disk
“fit” intrinsic size:
Major = 60 as
Minor = 212 as

15. VLBA map predictions @ 43 GHz
Jet ~ aligned with scattering disk
“fit” intrinsic size:
Major = 276 as
Minor = 68 as

16. VLBA map predictions @ 43 GHz
Jet ~ inclined 50° from scattering disk
“fit” intrinsic size:
Major = 154 as
Minor = 180 as

17. Summary the base of a jet is a natural solution for the flares,
Non-thermal emission (SSC and/or synchrotron) from
the base of a jet is a natural solution for the flares,
in both cases reconnection could be the driver
Jet models are robust: original model predictions holding up well, but we urgently need simultaneous submm/IR/X-ray data to constrain flare models
In the meantime, VLBA may offer a new way to test model predictions, both for quiescent and flared states. Stay tuned for better simulations.

18. Sgr A* in context
(Falcke, Körding & Markoff, A&A, 2004)

19. Sgr A* in context
(Falcke, Körding & Markoff, A&A, 2004)

20. Sgr A* in context
(Falcke, Körding & Markoff, A&A, 2004)

21. Sgr A* in context
Sgr A* falls on same correlation as other low disk luminosity sources, more so during flares.
Radio associated with jets in the other sources
Several independent studies now argue that jets dominate the power output for these low-lum sources, more so as luminosity goes down
Sgr A* is lowest luminosity LLAGN we currently know of. Jets likely necessary for energy dissipation.