sgra* x-ray flares with xmm-newton
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SgrA* X-ray Flares with XMM-NewtonSgrA* X-ray Flares with XMM-Newton
P. Goldoni, P. Goldoni,
A. Goldwurm, P. Ferrando, F. Daigne, A. Decourchelle,E. Brion, A. Goldwurm, P. Ferrando, F. Daigne, A. Decourchelle,E. Brion, G. BelangerG. Belanger
Service d’Astrophysque / CEA – Saclay, FranceService d’Astrophysque / CEA – Saclay, France
R.S. WarwickR.S. WarwickPhysics Dept., Leicester University, UKPhysics Dept., Leicester University, UK
P. Predehl, D. Porquet, B. AschenbachP. Predehl, D. Porquet, B. Aschenbach
MPE – Garching, GermanyMPE – Garching, Germany
SgrSgr A*A* • Compact radio source at the dynamical center of our Galaxy
• Very high column density along the line-of-sight
NH
~ 1-2 x 1023 cm-2
=> Only detectable in radio, IR, X-rays, an gamma-rays
• Motions of stars:
=> M = 3.5 ± 1.5 x 106 solar mass (Schödel et al. 2002)
=> Supermassive Black Hole
• Radio: very well known, bright, weakly variable source, 106 day
period
X-ray observations of SgrA*X-ray observations of SgrA*
• Only observable above 2 keV• Old generation of X-ray satellites (e.g, ASCA, BeppoSAX):
spatial confusion with other objects
Chandra
• L (2-10 keV) ~ 2.2 x 1033 erg/s (Baganoff et al. 2003) => 10-11 x Eddington Luminosity (~4.5 x 1044 erg/s)
, photon index ~ 2.5 roughly compatible with ADAF model
Flare detected with Flare detected with ChandraChandra in Sep in Sep 20002000
ChandraChandra detected a 10 ks flare in October detected a 10 ks flare in October 2000 2000 (Baganoff et al(Baganoff et al.. 2020001b1b))
Sgr A* Sgr A* peakpeak L LXX((22-10 keV) -10 keV) 10 103355 erg s erg s–1–1
~50 times stronger than in quiescence~50 times stronger than in quiescence Hard Hard spectrumspectrum:: 1.3 1.3 Fast variations, ~600 sec, small emission Fast variations, ~600 sec, small emission
region ~ 20 Rs for 3 million solar masses BH, region ~ 20 Rs for 3 million solar masses BH, argument against ADAF modelargument against ADAF model
Liu & Melia (2001) viscosity decrease in hot Liu & Melia (2001) viscosity decrease in hot circularized accretion flowcircularized accretion flow
Markoff et al. 2001 Sudden shock accelerationMarkoff et al. 2001 Sudden shock acceleration
XMM-Newton GTO XMM-Newton GTO observations-Iobservations-I
PI Anne Decourchelle Joint Saclay/Leicester/MPE PI Anne Decourchelle Joint Saclay/Leicester/MPE programprogram
Main scientific goal GC region diffuse emissionMain scientific goal GC region diffuse emission Total observing time on Sgr A*: 75 ksecTotal observing time on Sgr A*: 75 ksec XMM observations in september 2000 => solar XMM observations in september 2000 => solar
flare flare Spring 2001 => solar flareSpring 2001 => solar flare September 2001 initial phases of a Sgr A* flare September 2001 initial phases of a Sgr A* flare
(Goldwurm et al. 2002 ApJ)(Goldwurm et al. 2002 ApJ)
The XMM-Newton Observation of the GNThe XMM-Newton Observation of the GNPerformed on 4th September 2001Exposure ~ 26 ks EPIC in Full Frame Imaging mode : MOS 1, MOS 2, PN, Medium FilterRGS in spectral+Q mode, OM blocked
MOS 1+2 central CCD: ~ 4.5 cts/sSome proton flares observed
Complex region, diffuse emission + Complex region, diffuse emission + point sources : excess around Sgr A*point sources : excess around Sgr A*
XMM-Newton EPIC MOS 1 + 2
EPIC MOS 1+2 Central CCD
2-10 keV Count Rate (20s bin)
R= 10"
Search for Variability of Sgr A*Search for Variability of Sgr A*
MOS Image (pixels = 1.1MOS Image (pixels = 1.1" " 1.11.1") with ") with point sources detected by Chandrapoint sources detected by Chandra
Confused region for the XMM PSF (15" HPD) Optimized selections to search for Sgr A* contribution
Region within 10" from Sgr A* (60 % flux) in the 2-10 keV band
Use of Chandra results to model the contribution of other sources (Baganoff et al. 01)
Search for a variable central source
MOS 1+2 0.5 - 7 keV
R= 10"
Light Curves from data within 10Light Curves from data within 10"" from from Sgr A*Sgr A*
region at 1’ from Sgr A*
within 10’’ from Sgr A* MOS 1 + 2
PN
Count Rate from within 10’’ from Sgr A* for both MOS and PN (300 s less of data) : zoom around the end of the observation
7 excess
Comparison of Count Rate (2-10 keV, 180 s bin) from within 10’’ from Sgr A* and CR from a different region (same CCD)
900 s
Images before and during the flareImages before and during the flare
5'
The flare is clearly located at the center of the image compatible with a point source close to Sgr A*
MOS 1+2 2-10 keV
1000 s before flare 1000 s during flare
MOS 1+2 2-10 keV
Sgr A* position
Search & location of other point sources in the total MOS 1+2 0.5-4 keV image (all CCDs)
6 point sources identified with stars Average and rms offset
RA = –0.03" Dec = 0.20" rmsRA = 0.29" rmsDec = 1.5“
Consistent with syst. uncertainties
=> The flaring source is identified with Sgr A*
MOS 1+2 2-10 keV
1000 s during flare
Flaring source locationFlaring source location
1.5" Offset from Sgr A*
PSF fitting of central source on the last 1000 s image
Central source located at (J2000) R.A. = 17h 45m 39.99s Dec. = –29° 00' 26.7" (+/- 0.4" stat. err.)
1.5" from Sgr A* radio position (1.4" in Dec.), compatible with residual systematic errors for XMM
Spectra from data within 10Spectra from data within 10"" from Sgr A* from Sgr A* before the flarebefore the flare
Quiescent spectrum compatible with Chandra measuresQuiescent spectrum compatible with Chandra measures Well fitted by Thermal spectrum (Raymond & Smith 77) with kT ~ 1.3 keV + Well fitted by Thermal spectrum (Raymond & Smith 77) with kT ~ 1.3 keV +
Power law for point sources and backgroundPower law for point sources and background Sgr A* component (12 % of total emission) not required but consistent Sgr A* component (12 % of total emission) not required but consistent
MOS 1 + 2 PN Spectral fit of MOS and PN data with Spectral fit of MOS and PN data with model used for Chandra data of model used for Chandra data of quiescent statequiescent state
Best fit Best fit ((22 = 1.35, = 1.35, =121=121))
Thermal Component (diffuse)Thermal Component (diffuse) NNHH = 11.1 = 11.1 ± 0.6 10± 0.6 102222 cm cm-2-2
kT = 1.3 ± 0.08 keVkT = 1.3 ± 0.08 keV P–L (point sources + background)P–L (point sources + background) = 2.1 ± 0.3= 2.1 ± 0.3
P-L for Sgr A* (fixed to Chandra fit)P-L for Sgr A* (fixed to Chandra fit) = 2.7= 2.7
Spectral Hardening during the FlareSpectral Hardening during the Flare
MOS before flare
MOS during flare
H/R = F(4-10 keV) / F(2.5-4 keV)
Ha
rdn
es
s R
ati
o
Time (s)
Spectral fit of MOS + PN data during flare (last 900 s for MOS, last 600 s for Spectral fit of MOS + PN data during flare (last 900 s for MOS, last 600 s for PN) with model used for the quiescent statePN) with model used for the quiescent state
Thermal and point sources components fixed, Sgr A* Power-Law free Thermal and point sources components fixed, Sgr A* Power-Law free Best fit Best fit ((22
= 0.9, = 0.9, =27=27) ) forfor
Sgr A* Power-Law (NSgr A* Power-Law (NHH = 9.8 = 9.8 10 102222 cm cm-2-2 fixed to Chandra value)fixed to Chandra value)
= 0.9 ± 0.5= 0.9 ± 0.5
MOS 1 + 2
Spectra Parameters during the FlareSpectra Parameters during the Flare
Spectral fit using the Spectral fit using the data before flare data before flare as background componentas background component
Power-Law model Power-Law model (( = 0.98, = 0.98, =20=20))
NNHH = 9.8 = 9.8 10 102222 cm cm-2 -2 (fixed) (fixed)
= 0.7 ± 0.6= 0.7 ± 0.6
Similar result if dust scattering is Similar result if dust scattering is includedincluded
Luminosity 2–10 keV (8 kpc) :Luminosity 2–10 keV (8 kpc) : 3.8 3.8 ±± 0.7 0.7 10103434 erg s erg s-1-1
MOS 1+2
PN
XMM 2001 flare strongly resembles the early phase of the Chandra 2000 flareXMM 2001 flare strongly resembles the early phase of the Chandra 2000 flare Increase of factor 3 in 900 s, implies Sgr A* flux increase of factor 30Increase of factor 3 in 900 s, implies Sgr A* flux increase of factor 30 Spectrum compatible with hard slopeSpectrum compatible with hard slope No indication of lag between soft and hardNo indication of lag between soft and hard
Correlation with Radio dataCorrelation with Radio data
106 day radio cycle from VLA data 106 day radio cycle from VLA data (Zhao et al. 99)(Zhao et al. 99)
XMM 2001 flare at time phase XMM 2001 flare at time phase preceding the main radio peakpreceding the main radio peak (d64) (d64)
Chandra flare : 6 days after (d70)Chandra flare : 6 days after (d70)
Recent radio data show increase in the Recent radio data show increase in the cycle period (Yuan & Zhao 02) cycle period (Yuan & Zhao 02)
Flare Flare close to local max in 2001 Radio LCclose to local max in 2001 Radio LC
ChandraFlare
XMM Flare
XMM Flare
New Chandra 2002 New Chandra 2002 observationsobservations
500 ksec observations with 500 ksec observations with multiwavelength coverage (Keck, VLA,multiwavelength coverage (Keck, VLA,…)…)
Results not yet published, ~0.6 +/-0.3 Results not yet published, ~0.6 +/-0.3 flares/day, mostly weaker (factor ~10)flares/day, mostly weaker (factor ~10)
No obvious correlation with other No obvious correlation with other wavelengthswavelengths
XMM-Newton GTO XMM-Newton GTO Observations IIObservations II
50 ksec pointing on Sgr A* to be 50 ksec pointing on Sgr A* to be performedperformed
~30 ksec in February 2002, observation ~30 ksec in February 2002, observation notnot
completedcompleted Remaining time in October 2002Remaining time in October 2002 Brightest flare from Sgr A* !! (Porquet et Brightest flare from Sgr A* !! (Porquet et
al. 2003 A&A)al. 2003 A&A)
• flare duration ~ 2.7 ks, i.e less than one hour• Shorter variation ~200 sec, ~7 Rs
• flux amplication ~ 160 (peak of the flare/ quiescent) (~ x 3.5 October 2000, Chandra)
• symmetrical light curve shape • Similar light curve shape in the "soft" (2-5 keV) and in the "hard" (5-10 keV) energy bands: no significant spectral evolution between the rise and decay phase
October 2002: X-ray flare from Sgr A* (XMM-October 2002: X-ray flare from Sgr A* (XMM-Newton)Newton)
XMM/EPIC spectrumXMM/EPIC spectrum
photon spectral index :
= 2.50.3 XMM, 10/2002
Very soft compared to the previous ones:
1.3Chandra, 10/2000
1.0XMM, 09/2001
Comparisons with flare Comparisons with flare modelsmodels
The characteristics of this brightest flare in October 2002 (XMM) challenge theoretical Sgr A* flare modelling:
• Circularized flow (Liu & Melia 2002): when the viscosity increases SSC of mm to sub-mm photons is the dominant process: soft spectrum predicted.
A similar increase in the mm and sub-mm, not IR is expected: but not yet reported
• Jet model (Markoff et al. 2001)when the jet power or accretion rate increase: soft spectrum predicted
Simultaneous flaring at all frequencies are expected: but not yet reported
• Star-disk interaction (Nayakshin et al. 2003): for kT=1 and 70 keV a soft spectrum (~ 2.3) is predicted but very fine-tuned.
X-rays have become fundamental to solve Sgr A* puzzle
INTEGRAL/ISGRI Observations of SgrA*INTEGRAL/ISGRI Observations of SgrA*
Spring 2003, 1Msec exposure: Detection of a source at a position compatible with SgrA* in the 20-40 and 40-100 keV Spring 2003, 1Msec exposure: Detection of a source at a position compatible with SgrA* in the 20-40 and 40-100 keV band, implied luminosity ~10band, implied luminosity ~103535 erg s erg s-1-1
INTEGRAL/ISGRI Observations INTEGRAL/ISGRI Observations of SgrA*of SgrA* : variability: variability
SgrA* 20-40 keV lightCurve: Hints ofVariability on a40 min. timescale
But angular resolution12’ and positionerror ~0.8’
Rapid / high-amplitude X-ray flaring of Sgr A* is not a rare eventRapid / high-amplitude X-ray flaring of Sgr A* is not a rare event From XMM and Chandra results : ~0.6+/-0.3 flares/dayFrom XMM and Chandra results : ~0.6+/-0.3 flares/day Hard and soft spectra are observed, non definitive hints on accretion Hard and soft spectra are observed, non definitive hints on accretion
regime and emission mechanismsregime and emission mechanisms Possible hard X-ray source/flaring but source confusion is still a problemPossible hard X-ray source/flaring but source confusion is still a problem
Constraints on models, e.g. in case of change in mass accretion and SSC Constraints on models, e.g. in case of change in mass accretion and SSC is the main X-ray radiative mechanism the increase in radio should be is the main X-ray radiative mechanism the increase in radio should be comparable (Liu & Melia 02) , in all models correlated variability is comparable (Liu & Melia 02) , in all models correlated variability is predictedpredicted
Fast IR variability has very recently been observed (Genzel et al. 2003)Fast IR variability has very recently been observed (Genzel et al. 2003) No radio variability of such amplitude has been ever observedNo radio variability of such amplitude has been ever observed
Present state of ObservationsPresent state of Observations
Long XMM/INTEGRAL observations with ground basedRadio, submm, IR coverage are needed
XMM-Newton AO-3XMM-Newton AO-3 Proposal (Goldwurm et al.) to observe Proposal (Goldwurm et al.) to observe
SgrA* for 500 ksec (large program), SgrA* for 500 ksec (large program), accepted, 4 orbits granted. Goalsaccepted, 4 orbits granted. Goals
1) detect the largest possible number of 1) detect the largest possible number of flares with max. sensitivityflares with max. sensitivity
2) Correlate with Simultaneous hard X-2) Correlate with Simultaneous hard X-rays (INTEGRAL), radio (VLA) and IR(ESO)rays (INTEGRAL), radio (VLA) and IR(ESO)
PerspectivesPerspectives
Detection of several flares with different Detection of several flares with different spectraspectra
Modelization of X-ray sources in IBIS/ISGRIModelization of X-ray sources in IBIS/ISGRI
error box => hard X-ray spectrum of SgrA*error box => hard X-ray spectrum of SgrA* Monitoring of radio,submm and IR Monitoring of radio,submm and IR
flux/variabilityflux/variability Strongest possible constraints on SgrA* Strongest possible constraints on SgrA*
emission mechanisms and accretion regimeemission mechanisms and accretion regime
XMM-Newton October 2002 SgrA* XMM-Newton October 2002 SgrA* Flare Movie (MPE) Flare Movie (MPE)
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