Stellar Cusp

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NIR Emission and Flares from Sgr A
R. Schödel, A.Eckart Universität zu Köln
R. Genzel MPE, Garching
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Gravitational Potential near SgrA
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(No Transcript)
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S2 orbit in non-Keplerian potential Search for
Extended Mass

• Best fit
• Mtot 4.1 x 106 solar masses
• thereof 10 extended
• M/L gt 90
• could be explained e.g. by
• cluster of stellar mass BHs
• (Miralda-Escudé Gould, 2000)

Mouawad et al., 2004, submitted
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Sgr A and beyond, infinity 2001, A Space
Odyssey
NIR emission from Sagittarius A
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SgrA NIR flares!
NACO/VLT 8/9 May 2003 1.7 µm
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SgrA NIR flares!

• VLT 1.7 3.8 µm flares from SgrA Keck 3.8 µm
  
• Similar to X-ray flares (Baganoff et al., 2001)
• position within lt 10 mas from Sgr A
• Frequency 3 - 6/day!
• Factors 1.5 (3.8 µm) to 6 (1.7 µm )
• Time scales ? origin lt10 RS of 3.6x106 Msol BH

Genzel et al. 2003, Nature Ghez et al., 2003
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SgrA SED and models
Genzel et al. 2003, Nature, in press Ghez et al.
2003, ApJ Lett submitted
Radio Zhao, Falcke, Bower, Aitken, et al.
1999-2003 X-ray Baganoff et al. 2001, 2003,
Goldwurm et al. 2003, Porquet et al.
2003, models Markoff, Falcke, Liu, Melia,
Narayan, Quataert, Yuan et al. 1999-2001
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NIR flares quasi-periodicity
Genzel et al. 2003, Nature
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Spin measurement of Sgr A?

• Period at last stable orbit for 3.6 x106 Msol
• Schwarzschild BH 27 min
• Orbital frequency is shortest one of all
  expected frequencies
• near a BH.
• Interpretation of 17 min quasi-periodicity
• emission from accreting matter near LSO of
  spinning (Kerr) BH

Genzel et al., NATURE 2003
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SgrA K-band flare and quiescent emission
NACO/VLT June 16, 2003
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First Simultaneous NIR/X-rayObservation of Sgr A
Eckart, Morris, Baganoff, et al., submitted to
AA available on astro-ph
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Flare Activity in the Past
Consistent with our current knowledge of flares!
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To be continued
2004 will be the international year of SgrA.
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Astrometry
VLA/VLBA positions of SiO maser stars ?SgrA
position to lt10mas ? Positions of stars
to lt 10mas (within 10 of SgrA)
Menten et al. (1997) Reid et al. (2003)
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First Simultaneous NIR/X-rayObservation of Sgr A

• First simulataneous detection of Sgr A
• NIR/X-ray (quiescent and flaring state!)
• Spectral index for both states similar, 1.3
• SSC-model fits very well to data
• Upper limit of 15 min on time lag NIR/X-ray

Eckart, Morris, Baganoff, Schödel et al., in
preparation
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SgrA known SED before 2003
E

(
e
V
)
3
3
n (Hz)

Radio Zhao, Falcke, Bower, Aitken, et al.
1999-2003 X-ray Baganoff et al. 2001, 2003,
Goldwurm et al. 2003, Porquet et al.
2003, models Markoff, Falcke, Liu, Melia,
Narayan, Quataert, Yuan et al. 1999-2001
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Spin measurement of Sgr A?

• Period at last stable orbit for 3.6 x106 Msol
• Schwarzschild BH 27 min
• Orbital frequency is shortest one of all
  expected frequencies
• near a BH.
• Interpretation of 17 min
• quasi-periodicity
• emission from accreting matter
• near LSO of spinning (Kerr) BH
• with
• spin parameter
• a 0.52 (0.1, 0.07,0.14)

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IR flares quiescent emission from SgrA
RSgrA-flares lt 3 mas ( 350 Rs)
Genzel et al. 2003, Nature
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• Stellar Dynamics in the Nuclear Cluster
• The Nature of Sagittarius A
• The Stellar Cusp around Sagittarius A
• NIR Emission from Sgr A Flares

Were on the road toward a highly detailed
picture of an exemplary quiescent galaxy
nucleus! Black Hole physics at our doorstep!