1. Astrostatistics, and Brown Dwarfs Chris Koen, Dept. Statistics, University of the Western Cape

2. The GMC mass distribution in M33, as determined from radio flux measurements

3. HartRAO observations of G12.89+0.49

4. HartRAO observations of G12.89+0.49: detail

5. What are brown dwarfs? Stars : stable fusion of Hydrogen, M>70 Planets: no nuclear reactions, M<13 Intermediate objects with can sustain burning of Deuterium

6. A few properties Radius ~ 0.1 R₀ Surface temperature < 3000 K Luminosity ~ 10⁻⁴ L₀ Central temperature ~ 10⁶ K Deuterium burning lifetime a few Myr Spectral classes M, L, T

7. A conventional Hertzsprung-Russell diagram

8. The ultracool bottom end of the HR diagram

9. The Sun; M, L, T dwarfs; the planet Jupiter

10. “Only a few hundred stellar radio sources are now known” (SKA website). Because of their low temperatures and small radii, radiation levels of brown dwarfs are lower than those of stars.

11. Nonetheless, radio emission has been detected from a few late M (i.e. spectral types M7-M9) and L dwarfs. The emission is non-thermal, i.e. it is due to the action of magnetic fields.

12. What do astronomers hope to learn from the radio emission of brown dwarfs? Only direct access to magnetic fields Field configuration

13. Extent of the study to data About 90 objects have been studied (more than 500 L and T dwarfs known) Only 9 detections Quiescent, flaring and burst emission have been seen Quiescent emission not always at the same level Mostly single frequency

14. Quiescent radio emission from UCDs Name Spectral type Flux (microJy) LHS3003 M7 270±40 2M1048-3956 M8 140±40 TVLM513-46 M8.5 190±15 LSR1835+3259 M8.5 525±15 LP944-20 M9 74±13 BRI0021-0214 M9.5 83±18 2M0746+2000 L0.5 286±24 2M0523-1403 L2.5 231±14 2M0036+1821 L3.5 134±16

15. Flaring radio emission from UCDs Name Spectral type Flux (microJy) 2M1048-3956 M8 (29.6±1)X10⁴ TVLM513-46 M8.5 980±40 LP944-20 M9 2600±200 2M0036+1821 L3.5 720±40

16. DENIS 1048-3956 flaring emission at 4.80 (gray) and 8.64 GHz (black)

17. 8.44 GHz observations of TVLM 513-46546

18. 8.44 GHz observations of 2M0036+2000

19. Acknowledgments Comparison of the sun, MLT dwarfs, and Jupiter: Dr. Robert Hurt of the Infrared Processing and Analysis Center First HR diagram: Wikipedia Second HR diagram : Space Telescope Science Institute Maser data: Dr. Sharmila Goedhart TVLM 513-46546: Hallinan et al. (ApJ 663, L25; 2007) 2M0036+2000: Hallinan et al. (ApJ 684, 644; 2008) Denis 1048-3956: Burgasser & Putman (ApJ 626, 486; 2005)