NIR Emission and Flares from Sgr A* R. Schödel, A.Eckart Universität zu Köln R. Genzel MPE, Garching

Gravitational Potential near SgrA*

radius (parsec) enclosed mass (solar masses) dark cluster ρ 0 = 1.6x10 18 M sol pc -3 α = 5 visible star cluster ρ 0 = 1.5 x 10 6 M sol pc -3 r core = 0.46 pc, α = (±0.15) x 10 6 M sol point mass plus visible star cluster (χ 2 red = 1.02)

S2 orbit in non-Keplerian potential Search for Extended Mass Mouawad et al., 2004, submitted Best fit: M tot = 4.1 x 10 6 solar masses thereof 10% extended  M/L > 90 could be explained e.g. by cluster of stellar mass BHs (Miralda-Escudé & Gould, 2000)

NIR emission from Sagittarius A* Sgr A* „… and beyond, infinity“ 2001, A Space Odyssey

SgrA* NIR flares! NACO/VLT 8/9 May μm

SgrA* NIR flares! Genzel et al. 2003, Nature; Ghez et al., 2003 VLT: 1.7 – 3.8 μm flares from SgrA*; Keck 3.8 μm Similar to X-ray flares (Baganoff et al., 2001) position within < 10 mas from Sgr A* Frequency: 3 - 6/day! Factors 1.5 (3.8 μm) to 6 (1.7 μm ) Time scales  origin <10 R S of 3.6x10 6 M sol BH

Radio: Zhao, Falcke, Bower, Aitken, et al 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 SgrA* SED and models Genzel et al. 2003, Nature, in press Ghez et al. 2003, ApJ Lett submitted

NIR flares: quasi-periodicity Genzel et al. 2003, Nature

Spin measurement of Sgr A*? a’=0.52 a’=0.52 (±0.1,±0.07,±0.14) orbital period at last stable orbit a/(GM/c) T l s t o ( m i n ) orbital period at last stable orbit a/(GM/c) T (min) a‘ = 0.52 (±0.1, ±0.07,±0.14) Period at last stable orbit for 3.6 x10 6 M sol 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

SgrA*: K-band flare and quiescent emission NACO/VLT June 16, 2003

Sgr A*, June 20, 2003 First Simultaneous NIR/X-ray Observation of Sgr A* Eckart, Morris, Baganoff, et al., submitted to A&A; available on astro-ph

March 1996 SHARP/NTT Flare Activity in the Past SgrA* S2 S8 Minutes Janskys Consistent with our current knowledge of flares!

To be continued… 2004 will be the international year of SgrA*.

Astrometry VLA/VLBA positions of SiO maser stars  SgrA* position to <10mas  Positions of stars to < 10mas (within 10“ of SgrA*) Menten et al. (1997); Reid et al. (2003)

First Simultaneous NIR/X-ray Observation of Sgr A* 1.First simulataneous detection of Sgr A* NIR/X-ray (quiescent and flaring state!) 2.Spectral index for both states similar, ~1.3 3.SSC-model fits very well to data 4.Upper limit of 15 min on time lag NIR/X-ray Eckart, Morris, Baganoff, Schödel et al., in preparation

Radio: Zhao, Falcke, Bower, Aitken, et al 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 SgrA*: known SED before 2003  z  3 3 E (eV) Submm „bump“ sharp drop-off in NIR X-ray: quiet time and flare emision (Chandra) Jet-disk model Yuan et al.

Spin measurement of Sgr A*? Period at last stable orbit for 3.6 x10 6 M sol 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)

IR flares & quiescent emission from SgrA* Genzel et al. 2003, Nature R SgrA*-flares < 3 mas ( 350 R s )

1. Stellar Dynamics in the Nuclear Cluster 2. The Nature of Sagittarius A* 3. The Stellar Cusp around Sagittarius A* 4. NIR Emission from Sgr A*: Flares ρ * ( R )=3x10 7 (R/arcsec) -1.4 (M  pc -3 ) H+K, K s  17 crowding corrected corrected S2 50mas 2 light days We‘re on the road toward a highly detailed picture of an exemplary quiescent galaxy nucleus! + Black Hole physics at our doorstep!