Reconstructing the past activity of the supermassive black hole at the Galactic Centre R. Terrier, APC Paris M. Clavel, A. Goldwurm, M. Morris, G. Ponti, S. Soldi COSPAR, Aug. 2014, Moscow

Active and inactive SMBH in the Universe IC 2497: an extinct quasar? 10 9 M o SMBH Light echo of past quasar emission emitted ~ 70 kyr ago Current luminosity is up to 10 4 smaller Timescale of ~ 10 kyr is consistent with state changes observed in Galactic XRB (~1h) Schawinski et al. (2010) Transition timescale for Sgr A*: 50 yrs What timescales for state transition of SMBH?

Active and inactive SMBH in the Universe GRB a/Sw : Stellar disruption by SMBH? Burrows et al. (2011), Levan et al. (2011) etc IGR J : ~150 days transient Peak luminosity at erg/s ~ 0.2 L edd Radiated energy ~ erg a tidal capture of Jupiter-like object? Nikolajuk & Walter (2013) Timescales and recurrence time of catastrophic events near SMBH?

Diffuse non-thermal emission from the central 100 pc 100 pc Hard X-ray continuum emission from the central 200pc detected by ART-P: reflection of X-ray source? Sunyaev+93 Intense 6.4 keV FeK a line emission resolved from GC clouds: Past Sgr A* flare (300 yrs ago)? Koyama+96 ASCA 6.4 keV

100 pc XMM 6.4 keV Diffuse non-thermal emission from the central 100 pc Hard X-ray continuum emission from the central 200pc detected by ART-P: reflection of X-ray source? Sunyaev+93 Intense 6.4 keV FeK a line emission resolved from GC clouds: Past Sgr A* flare (300 yrs ago)? Koyama+96

100 pc XMM 6.4 keV Diffuse non-thermal emission from the central 100 pc Hard X-ray continuum emission from the central 200pc detected by ART-P: reflection of X-ray source? Sunyaev+93 Intense 6.4 keV FeK a line emission resolved from GC clouds: Past Sgr A* flare (300 yrs ago)? Koyama+96

Hard X-rays from Sgr B2 100 pc Integral discovered hard X-ray emission (up to >100 keV) from Sgr B2 and G clouds Revnivtsev+04, Belanger+06 The 6.4 keV & hard X-ray continuum emission from Sgr B2 is consistent with an echo from some past Sgr A* intense activity erg/s ~ 300 yrs ago Are there other possible explanations? 200 pc

Origin of the non thermal X-ray emission from GC clouds? Cosmic-ray bombardement? Illumination by past bright X-ray source? 1 keV 10 keV 1 keV 10 keV Key observable is time variability!

SF2A 2004 Hard X-ray echo of past activity Line Continuum Clavel 14

SF2A 2004 Hard X-ray echo of past activity Line Continuum Clavel 14

SF2A 2004 Hard X-ray echo of past activity Line Continuum Clavel 14

Early evidences for variations of the emission PRELIMINARY Sgr B2 (20-60 keV) 6.4 keV flux variations in Sgr B2 region Inui+09 Sgr B2 (20-60 keV) 100 pc XMM 6.4 keV Moving continuum diffuse clumps seen by Chandra in Sgr A region Muno+07

Hard X-ray emission from Sgr B2 is fading! Analysis of 20 Ms of Integral data from 2003 to 2009 PRELIMINARY Sgr B2 (20-60 keV) Sgr B2 Integral IBIS/Isgri : keV 2007 Illumination ! Terrier+10 Sgr B2 (20-60 keV) Oph cluster t = 8.2 ± 1.7 yr

Hard X-ray emission from Sgr B2 is fading! Suzaku observes similar decay in 2009 at 6.4 keV and in hard continuum band PRELIMINARY Sgr B2 Integral IBIS/Isgri : keV 2007 Nobukawa+11 Sgr B2 (20-60 keV)

A past flare of the SMBH is illuminating Sgr B2! Distance implies Sgr A* is the most likely candidate to Earth

Photons scattered by Sgr B2 were emitted ~ 100 yrs Parallax measurement: Sgr B2 is 130 ± 60 pc in front of Sgr A* direct pathscattered path Delay 100 yrs (70-150) (H 2 O maser, VLBI, Reid et al, 2009)

Time variability in the Sgr A complex? 100 pc Sgr A

PRELIMINARY the central 30 pc observed for 8 years XMM-Newton Fe Ka 6.4 keV: pc

PRELIMINARY Flux variations in the central 30 pc Fe Ka 6.4 keV: pc Fe Ka flux

PRELIMINARY Some propagation effects? Fe Ka 6.4 keV: pc

PRELIMINARY Apparent superluminal motion! Most solid proof that Fe Ka emission is caused by illumination Sgr A* is illuminating most of the clouds in the GC Ponti+10 To the GC

Apparent superluminal motion? Effect discussed by Sunyaev & Churazov (1998) Curves of constant delay (isochrons) : parabola Apparent light crossing times: 120 yrs 70 yrs 45 yrs

If the « bridge » and Sgr B2 are illuminated by the same flare (10 39 erg/s): Bridge located 60 pc behing Sgr A* & flare began 400 years ago? A possible lightcurve of Sgr A* over past centuries? Ponti+10

SF2A 2004 Sgr A* is fed by winds of surrounding massive stars: Intrinsic accretion rate variability likely to weak Stochastic infall of clumps from nearby massive stellar winds? Cuadra et al. (2008) Origin of the high Sgr A* state?

SF2A 2004 Deceleration of jet produced by stellar tidal disruption event? Yu et al (2011) Asteroids and planet disruption? Zubovas et al (2012) Accretion of debris produced by stellar collisions? Sazonov et al. (2012) Multiple cloud accretion events? Czerny et al. (2013) Origin of the high Sgr A* state?

SF2A 2004 Intrinsic accretion rate variability due to stochastic infall of clumps from nearby massive stellar winds? Cuadra et al. (2008) Deceleration of jet produced by stellar tidal disruption event? Yu et al (2011) Asteroids and planet disruption? Zubovas et al (2012) Accretion of debris produced by stellar collisions? Sazonov et al. (2012) Multiple cloud accretion events? Czerny et al. (2013) Origin of the high Sgr A* state? Can we determine the light curve of Sgr A* over the last centuries?

PRELIMINARY Constraining Sgr A* light curve over the past centuries To reconstruct Sgr A* past activity: L Sgr A* is a function of cloud N H and radius Time delay given by cloud position along LoS 3D distribution of GC molecular clouds is critical! oror ? Sofue95 Molinari+11 Existing 3D models from radio measurements are very uncertain

PRELIMINARY Constraining Sgr A* light curve over the past centuries Solution: Use X-rays to constrain the GC clouds Line of Sight (LoS) position Different approaches: Use angular dependency of 6.4 keV Equiv. Width Capelli+12 Use X-ray intrinsic N H and measure partial absorption of GC thermal plasmas to locate cloud along LoS Ryu+09, Ryu+13 Use lightcurve of echoes to associate clouds with similar delays: X-ray tomography of GC ISM Clavel+13

SF2A 2004 Constrain cloud position along the line of sight using EW of Fe Ka line, and deduce Sgr A* luminosity from N H deduced from X-ray spectrum Towards a Sgr A* lightcurve Capelli+12

SF2A 2004 Towards a Sgr A* lightcurve Ryu+13

Clavel+13 Detailed timing of the echoes with Chandra Chandra Fe Kα line flux: Variations & propagation in all Sgr A complex clouds More complex pattern than previous studies suggest 30pc

Clavel+13 Propagation follow-up in 2011 Chandra Fe Kα line flux: A new thin (0.2 pc!) filament : Flux increases by a factor greater than 10 Filament illuminated by L X >10 39 erg/s 30pc Size: 0.2 x 1.0 pc 2 d SgrA* ≥ 23 pc N H ≤ cm

Clavel+13 Distinct timing behaviours in the Sgr A complex echoes 2 distinct time behaviours: 10 yr linear increase or decrease 2 yr peaked variation Systematic lightcurve extraction in 15'' boxes (4-8 keV)

Clavel+13 Two distinct events reflected in Sgr A complex! 2 distinct events are required ( erg/s Absolute timing still unkown short var. long var.

SF2A 2004 Intense hard non-thermal X-ray emission (G~1.6 up to 30 keV) around the Arches cluster Capelli+10, Tatischeff+12, Krivonos+13 Inverse bremstrahlung emission of subrelativistic ions? Required power in CR ions: P CR = (0.5 – 1.8)×10 39 erg s -1 Powered by collision between the Arches cluster and ambient cloud? The Arches cluster: an accelerator of CR ions? Arches cluster CR energy density: ~ 1000 eV cm -3 The Arches cluster: an extreme CR dominated region? Tatischeff+12

SF2A 2004 The Arches cluster: an accelerator of CR ions? Look for time variability of 6.4 keV and continuum emission over 13 yrs A 30% flux variation observed in Most of the non-thermal X-ray flux from Arches cluster surroundings is due to reflection of Sgr A* past flare Clavel+14, see poster STW-S-132, presentation by R. Krivonos continuum Fe Ka

The Fe K a emission of the CMZ 10 years apart Comparison of XMM surveys reveals variations over the whole CMZ: Overall decrease Strong variations in Sgr C complex See S. Soldi presentation 100 pc XMM, 6.4 keV FeK a line 2012

 Solid proof that Sgr A* activity has changed in recent past  Hard X-ray and Fe Ka emission is highly variable in the central 200pc  Reflection of hard & energetic events from Sgr A*  Arches emission is dominated by reflection Towards a lightcurve of Sgr A* over the last millenium? Strong uncertainties in the LoS distribution of clouds X-rays can be used to constrain it Use X-ray echoes timing (tomography) and large scale surveys to improve knowledge on cloud position Detailed Chandra monitoring reveal at least 2 distinct events High luminosities >10 39 erg/s Durations: <2 yrs, ~10 yrs respectively Disruption events? Strong fluctuations in accretion rate? Further constraints from XMM (Soldi's talk), Suzaku (Nobukawa's talk) Conclusions

Sgr A* : the dormant SMBH of the Milky Way 0.3 pc Faint Galactic Centre source Sgr A* powered by a M o SMBH (Ghez et al., 2008, Gillessen et al, 2009) Sgr A*: a laboratory to study dormant SMBH and their possible state transitions

Sgr A*: quiescent emission Quiescent emission luminosity ~ erg/s i.e. a few L edd Resolved by Chandra (r~1.4'' ~ R bondi ), aligned with massive star disk L X ~ erg/s Baganoff et al. (2003), Wang et al. (2013) Massive stars wind accretion rate at Bondi radius M o /yr Accretion rate at the SMBH < M o /yr! Sgr A* Chandra Genzel et al (2010) Wang et al. (2013)

Looking for Sgr A* flares in hard X-rays Sgr A* exhibits flaring activity in X-rays Flare frequency: 1.1± 0.2 day -1 Typical duration: ~ 1 ks dN/dL µ L -1.9 Neilsen et al. (2013) Most intense flare detected at L X ~ erg/s (e.g. Goldwurm et al. 2003, Porquet et al., 2008, Nowak et al 2012) XMM-Newton Apr Trap et al. (2010)

X-ray spectrum w.r.t. to LoS position Constrain geometry with the full spectrum X-ray – hard X-ray NuStar/Astro-H?