Chandra Observations of Sgr A*

1
Chandra Observations of Sgr A
Frederick Baganoff
Massachusetts Institute of Technology
MIT Mark Bautz George Ricker
Penn State Niel Brandt Gordon Garmire
UCLA Mark Morris
2
Chandra Galactic Center Deep Field
17 x 17 arcmin 40 x 40 pc 590 ks
Red 2-3.7 keV Green 3.7-4.5 keV Blue 4.5-8 keV
3
Chandra Galactic Center Deep Field
8.4 x 8.4 arcminutes
4
Chandra 3-Color Image of the Central Parsec
5
VLA 6 cm Image of Sgr A West Minispiral
6
Radio Image of Sgr A West and Circumnuclear Disk
Red HCN Blue 6 cm
7
X-ray Image and 6 cm Contours of Sgr A West
8
2000 October 26-27
(Baganoff et al. 2001)
Oct 27 0542 UT 45x, 4 hr
9
Multiwavelength Monitoring of the Supermassive
Black Hole in the Galactic Center
F.K. Baganoff1
M.W. Bautz1, G.R. Ricker1, W.N. Brandt2, G.
Chartas2, E.D. Feigelson2, G.P. Garmire2, M.
Morris3, E.E. Becklin3, A.M. Ghez3, S.D.
Hornstein3, A.M. Tanner3, A.S. Cotera4, P.M.
Hinz4, W.F. Hoffmann4, M.R. Meyer4, A. Eckart5,
R. Genzel6, J.-H. Zhao7, R.M. Herrnstein7, J.L.
Hora7, J.-P. Macquart8, Y. Maeda9, R.J.
Sault10, G.B. Taylor11, F. Walter11
1MIT, 2UCLA, 3Penn State, 4Steward Obs., 5U.
Cologne, 6MPE, 7CfA, 8U. Groningen, 9ISAS,
10ATNF, 11NRAO
10
Observatories Participating in Sgr A Monitoring
Campaign

• Chandra (12-62 nm)
• Keck (2 10 mm)
• Very Large Telescope (3-5 mm)
• Magellan (10 mm)
• Submillimeter Array (1.3 mm)
• Caltech OVRO Millimeter Array (3 mm)
• Australia Telescope Compact Array (3 mm)
• Very Large Baseline Array (7 mm)
• Very Large Array (7mm, 1.3 cm, 2 cm)

11
2002 May 22-23 Orbit 1, Part 1
12
2002 May 24 Orbit 1, Part 2
May 24 1942 UT 5x, 1.7 hr
13
2002 May 25-27 Orbit 2
May 26 0424 UT 6x, 0.75 hr
May 24 1942 UT 5x, 1 hr
May 26 1347 UT 5x, 0.5 hr
14
2002 May 28-30 Orbit 3
May 28 1536 UT 25x, 1 hr
May 29 1833 UT 13x, 0.5 hr
May 29 0603 UT 12x, 1.5 hr
15
2002 June 3-4 Orbit 5
16
Sgr A Multiwavlength Monitoring Campaign
17
Three Large X-ray Flares from Sgr A
18
Very Long Baseline Array 7 mm

• No significant flux variability detected (upper
  limit about 30)
• No extended structure appeared within 5 hour
  track (upper limit about 10 mJy)

19
Model Absorbed, Dust-Scattered Power Law
Integrated X-ray Spectrum of Sgr A Flares
20
Summary - Sgr A Flares

• Chandra observed Sgr A for 139 hr over a
  two-week period in late May to early June 2002
• 3 X-ray flares with amplitudes gt10x detected in a
  28-hr period
• 4 X-ray flares with amplitudes 5x detected in
  addition
• Typical flare duration is about 1 hr (0.5-4 hr)
• XMM-Newton has detected 2 large X-ray flares
  (Goldwurm et al. 2002 Porquet et al. 2003)
• Amplitudes, durations, and rise/fall timescales
  similar to Chandra flares
• First flare had hard spectrum G 1.1
• Second flare - brightest to date (90x) - has soft
  spectrum G 2.5
• Distribution of flare properties? Different
  physical conditions?

21
Summary - Sgr A Flares (continued)

• Strong X-ray flares occur about once per day
• Observed frequent, large-amplitude,
  short-duration flaring behavior of Sgr A is
  unique among SMBHs
• Probably selection effect flares too faint to
  detect in other galaxies
• Behavior inconsistent with X-ray binaries and not
  seen from any of the other gt2,300 X-ray point
  sources in the field

22

Integrated X-ray Spectrum of Sgr A Quiescent
Emission
Model Absorbed, Dust-Scattered, NIE Plasma
NH 5.9 x 1022 cm-2 G 4-5 keV EFe 6.59
(6.54-6.64) keV Line is narrow and NIE FX 1.8
x 10-13 erg cm-2 s-1 LX 1.4 x 1033 erg s-1 D
8 kpc ltLFgt / ltLQgt 14.0
23
Radial Profile of Central 10 Arcseconds
Slope 1.0
24
Chandra Lightcurve of Sgr A
Eckart, Baganoff et al. (2004)
19-20 June 2003
2-8 keV
Counts per second
Minutes
25
VLT Lightcurve of Sgr A
2.2 um
19-20 June 2003
Eckart, Schoedel, et al.
26
VLT AO Images
Sgr A bright
Sgr A bright
Sgr A dim
27
Bayesian Blocks Representation of X-ray
Lightcurve

• Excess amplitude x2
• Duration 40-60 min
• 99.923 confidence

Scargle (1998)
28
X-ray and NIR Lightcurves

• First simultaneous detection of X-ray and NIR
  flare
• At least in this case, X-ray and NIR photons
  appear to come from a single electron population
• Lx 6x1033 erg/s
• Lnir 5x1034 erg/s
• Spectral index 1.3
• X-rays coincident within 180 mas
• NIR coincident within 14 mas
• X-ray flares from Sgr A

29
Sgr A and X-ray Transients in the Central
Arcminute of the Galaxy
1 hour / frame 6 days 17 hours