nir emission and flares from sgr a*
DESCRIPTION
NIR Emission and Flares from Sgr A*. R. Schödel, A.Eckart Universität zu Köln. R. Genzel MPE, Garching. Gravitational Potential near SgrA*. 3.35( ±0.15 ) x 10 6 M sol point mass plus visible star cluster ( χ 2 red = 1.02). enclosed mass (solar masses). dark cluster - PowerPoint PPT PresentationTRANSCRIPT
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*.