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)