NIR Emission and NIR Emission and Flares Flares

from Sgr A*from Sgr A*

R. Schödel, A.EckartUniversität zu Köln

R. GenzelMPE, Garching

Gravitational Potential near

SgrA*

radius (parsec)

enc

lose

d m

ass

(so

lar

ma

sse

s)

dark clusterρ0 = 1.6x1018 Msol pc-3

α = 5visible star clusterρ0 = 1.5 x 106 Msol pc-3

rcore = 0.46 pc, α = 1.7

3.35(±0.15) x 106 Msol point massplus visible star cluster(χ2

red = 1.02)

S2 orbit in non-Keplerian potentialSearch for Extended Mass

Mouawad et al., 2004, submitted

Best fit: Mtot = 4.1 x 106 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 2003

1.7 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 RS of 3.6x106 Msol BH

Radio: Zhao, Falcke, Bower, Aitken, et al. 1999-2003X-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

SgrA* SED and models

Genzel et al. 2003, Nature, in pressGhez et al. 2003, ApJ Lett submitted

0.01

1

100

10000

109

1011

1013

1015

1017

1019

10-4

10-2

100

102

104

RIAF + 5.5% p=1 power lawRIAF + 1.5% p=3.5 power lawRIAF + SSCjet-disk

(Hz)

L (

3.8

x10

33 e

rg/s

)E (eV)

NIR flares: quasi-periodicity

0

4

8

12

0 50 100

S1SgrA*

K 16.06.2003 to=4h47m46s (UT)

0

5

10

15

20

25

0 50 100

S1 x2

K 15.06.2003 to=3

h 01

m07

s (UT)

t-to (min)

dere

dden

ed fl

ux d

ensi

ty (

mJy

)

0

0.1

0.2

0.3

0.4

0.5

2x10-4 5x10-4 10-3 2x10-3 5x10-3 10-2

SgrA* June 16S1 June16 allSgrA* June 15

K-band flares June15th & 16th

T=16.52.5 min

frequency (Hz)

norm

aliz

ed F

FT

am

plitu

de

Genzel et al. 2003, Nature

Spin measurement of Sgr A*?

a’=0.52 a’=0.52 ((±0.1,±0.07,±0.14)±0.1,±0.07,±0.14)

0

1 0

2 0

3 0

0 0 . 2 0 . 4 0 . 6 0 . 8 1 . 0

o r b i t a l p e r i o d a t l a s t

s t a b l e o r b i t

a / ( G M / c )

Tls

to

(m

in)

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 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

SgrA*: K-band flare and quiescent emission

NACO/VLT June 16, 2003

Sgr A*, June 20, 2003

First Simultaneous NIR/X-rayObservation 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

10-3

Ja

nsk

ys

Consistent with our current knowledge of flares!

To be continued…

2004 will be the international year of SgrA*.