New evidence for extreme particle acceleration in Microquasars Edoardo Striani on behalf of the AGILE Team

AGILE: inside the cube… ANTICOINCIDENCE HARD X-RAY IMAGER (SUPER-AGILE) Energy Range: 18–60 keV SILICON TRACKER GAMMA-RAY IMAGER (GRID) Energy Range: 100 MeV - 10 GeV (MINI) CALORIMETER Energy Range: 0.3–100 MeV

Galactic Center Cygnus Region Carina-Vela Regions pointing AGILE: 24-month intensity map (E > 100 MeV) (July 2007 – August 2009)

AGILE in spinning: 5-month intensity map (E > 100 MeV) (Nov – Mar. 2010)

AGILE observations of microquasars Sporadic gamma-ray emission from Cyg X-1 Cygnus X-3 (currently the most prolific above 100 MeV) Non-detections (so far) of other microquasars despite many AGILE monitoring observations (hard X-rays and gamma-rays)

Cyg X-1

Most of its time in the “hard state”: –low flux of soft X-ray(1-10 KeV) –peak in the hard X-ray band (around 100 KeV) –energy cutoff around 1 MeV. Ocasionally in “soft state”: –large flux in soft X-rays –low flux in hard X-rays –tail extending up to 1 MeV. Spectral states modelled by Comptonizzation models –Thermal component –Non-thermal component that can reproduce the spectral cutoff near 1 MeV

Example: Comptonization-hybrid model (Coppi 1999)

Cyg X-1 modelling (Coppi 1999)

Cyg X-1 MAGIC Cherenkov telescope –high-energy emission above 300 GeV in 2006 (Albert et al 2007) during a hard X-ray spectral state INTEGRAL detected an intense peak in hard X-rays 1 day later (Malzac et al. 2008) First hint that extreme particle acceleration processes may occour also during a hard spectral state  non-thermal component can be detected also in states believed to be characterized by a cutoff above few MeV

AGILE and Cyg X-1 No detection in deep integration (2007 July – 2009 October) Detection at 5.3 sigma (15 october 2009, transient emission) –Cyg X-1 was in the HARD STATE –The system was detected to subsequently evolve into one of the relatively rare dips of the hard X-ray light curve

2-12 keV keV

AGILE and Cyg X-1: discussion Lack of detection on deep integrations (when the source was in the hard state) confirms the existence of a spectral cutoff between 1 and 100 MeV in the hard state

Spectral energy distribution in tipical states for Cyg X-1 Agile 2-sigma upper limits above 100 MeV for A)2 weeks B)4 weeks C)315 days The gamma-ray average spectral behavior in the hard state during week-month-year timescales is in agreement with Comptonizzation models of Black Hole Candidates (Coppi 1999).

AGILE and Cyg X-1: discussion Flare episode Efficient particle acceleration occours also in states characterized by the presence of a hot corona that should be in pair- Comptonized equilibrium (Zdziarsky et al. 2009) The physics of the system can occasionally be more complex than predicted by current models. Unfortunatly no simultaneus MAGIC data –Both detection in hard state –MAGIC spectral index (3.2±0.6) in qualitative agreement with our spectral detection

Spectral energy distribution for Cyg X-1 and AGILE data above 100 MeV for the flaring episode

Cyg X-1: conclusions Even in the hard state Cyg X-1 is capable of producing transient episodes of extreme particle acceleration (1-day or less). Need of a more detailed model of thermal Comptonized coronae and non-thermal particle acceleration (for short timescales) Flaring activity detected during decreasing hard X-ray emission (Cyg X-3 – Tavani et al 2009)

Cyg X-3

Cyg X-3 appears to be “special” A very variable microquasar Very strong (up to Jy) radio flares Jets pointing towards the Earth Correlated radio/soft X-ray/hard X-ray states

Spectral shapes of Cyg X-3 (Szostek et Zdziarski 2004) 5 spectral states with increasing softness

Radio vs. soft X-ray (Szostek et al 2008) Considering the radio and soft-X data, we can find 6 distinct states Soft X-ray Flux (log)‏ Radio Flux (log)‏

Cyg X-3: Bringing together the radio & X-ray ( Szostek,Zdziarski, McCollough, 2008; Hannakainen, Koljonen, 2010) Radio vs. soft X- ray After quenched state always major flare log Energy [keV] log E*F E [keV cm -1 s -2 ] SZM08 Koljonen MSc thesis Quenched state always followed by a major radio flare. Major radio flares when the source was in the soft state

AGILE and Cygnus X-3 AGILE detects weak persistent emission above 100 MeV and several gamma-ray flares from Cygnus X-3 –16-17 Apr 2008 –2-3 Nov 2008 –11-12 Dec 2008 –20-21 Jun 2009 Flares are all associated with special CygX-3 radio and X-ray/hard X-ray states Gamma-ray flares usually before radio flares

Agile and Cyg X-3 All gamma-ray flares occur either in coincidence with low hard-X-ray fluxes or during transitions from low hard-X-ray fluxes to high The Cyg X-3 hard-X-ray fluxes (20 keV and above) and regular-X-ray fluxes (1–10 keV) are anticorrelated. Therefore, gamma-ray flares occur only during soft-X-ray states or during transitions between such states and quenched hard-Xray states.

Cygnus X-3 in April 2008 Very strong radio-flare reaching ~20 Jy on Apr. 18, 2008 (RATAN) The gamma-ray flare partially overlaps a 1-day peak of the soft X-ray emission Cyg X-3 changed state immediately following the soft-X-ray/gamma-ray peak, from a soft X- ray to an intermediate hard X-ray state in a few hours

very strong radio flare, presumably with jet ejection strong gamma-ray flare X-ray (1-10 keV) flare Hard X-ray flux state change (Super-A monitoring)

November 3, 2008 Cyg X-3 was in a prolonged soft state with apparently no peculiar high-energy characteristic but the gamma-ray flare occurred when Cyg X-3 was just entering in a rare “quenched radio state” (AMI Large Array (AMI-LA)): This state was followed a few days later by a major radio flare reaching about 1 Jy at 15 GHz. Once again, the gamma-ray flare near 100 MeV occurred at a peculiar transition in preparation of a major radio flare.

”quenched” radio state !

December 12, 2008 Prolonged soft state lasting about a month changed in mid December, 2008 into a hard state. This transition coincided with a major radio flare that occurred on December 20, 2008 after a very interesting evolution of the radio flux

3 Nov Dec. 08 AMI-LA

RATAN, December Dec. 2008

Dec gamma- ray flare

June-July, different flaring episode, during a decrease and increase of the hard-X emission Swift/BAT lightcurve

22 Jun. 09 AMI-Large Array apparently not followed a few days later by a major radio flare – lack of data, BUT… June 21-22, 2009

Radio and AGILE/GRID data of Cygnus X-3 during Jun-Jul 2009 July 2009: Again a radio flare follows a gamma-ray flare…

AGILE/GRID and Swift/BAT data of Cygnus X-3 during Jun-Jul 2009 …and again Hard X-ray flux change

Major gamma-ray flares in special transitional states in preparation of radio flares ! figure adapted from Szostek Zdziarski & McCollough (2008) Gamma-ray flares tend to occur in the rare low-flux/pre- flare radio states. For all gamma-ray flaring episodes, the radio and hard- X-ray fluxes are low or very low, while the soft X-ray flux is large

Cygnus X-3 lessons: Direct evidence that extreme particle acceleration (above 100 MeV) and non-thermalized emission can occur in microquasars with a repetitive pattern Emission must be produced not to far away from the central object (see orbital modulation revealed by Fermi) Cyg X-3 is capable of accelerating particles by a very efficient mechanism leading to photon emission at energies thousands of times larger than the maximum energy so far detected (E ~ 300 keV). Comptonization models (thermal and non-thermal) that reproduce the spectral states up to 300 keV must take into account the new data above 100 MeV

Implications… Cygnus X-3 can teach about BH systems and possibly also about blazars Its jet is pointing at us, it is a “micro-blazar” “preparation” for a major jet ejection and non-thermal extreme particle acceleration with GeV emission before plasmoid production is suggested also in some blazars Bright future for understanding BHs

Watch it now !

Conclusions Very exciting time for Galactic gamma-ray source studies, AGILE and FERMI Remarkable Cyg X-3 detection: a “clock” with a clear pattern of gamma-ray emission; crucial theoretical implications Cyg X-1 also detected and more sporadic Beginning of a new era for microquasar studies

Thank You

Gamma-ray orbital modulation for Cyg X-3 (Fermi)

Cyg X-1: AGILE and Fermi time coverage and off-axis angle

4.1 Galactic Centre 2-days integration (13-14 Mar 2010) – spinning mode

4.2 Galactic Centre 1-month integration (20 Feb-20 Mar 2010)

5. Cyg X-1 Region (25 Mar 2010) – spinning mode

Cyg X-3 AGILE average spectrum (non-simultaneous spectra)