AGILE results on relativistic outflows above 100 MeV Carlotta Pittori, ASI Space Science Data Center on behalf of the AGILE Coll. C. Pittori, INAF-OAR and SSDC HEPRO 6 in Moscow, 15-09-2017

The AGILE Payload: the most compact instrument for HE astrophysics only ~100 kg (~ 60  60 cm) GRID gamma-ray imager (30 MeV - 30 GeV) SuperAGILE hard X-ray imager (18 - 60 keV) MCAL Minicalorimeter (0.3 - 100 MeV) Italian Space Agency (ASI) Mission with INFN, INAF participation

Low Earth equatorial orbit: 550 Km and < 3º inclination angle 2007-2017: AGILE is 10! India April 23, 2007: Launch Low Earth equatorial orbit: 550 Km and < 3º inclination angle

Malindi Ground Station Satellite Malindi Ground Station Fucino TZP MOC ASDC AGILE Team Guest Observers Public data access AGILE: “very fast” Ground Segment ~1 hr ~0.5 hr Automatic data processing ~0.5-1 hr ~(2-2.5) hr Record for a gamma-ray mission! App AGILEScience for mobile dev Now even faster (25 min latency) optimized for GW counterpart hunt!

??? TERRA INCOGNITA ???

Recent discovery from HE astrophysics above 100 MeV Gamma-ray intense transients on short timescales (< minutes, days) in different astrophysical systems: Gamma-ray flares E>100 MeV in Microquasars (binary systems as Cyg X-3 and Cyg X-1) Almost monochromatic gamma-ray flares from Crab Pulsar Wind Nebula Gamma-ray flares up to TeV from FSRQ, with fast observed timescale variability of the order of minutes

High Energy Astrophysics: new lessons Role of the magnetic field Crab phenomenon (super-acceleration) Plasma instabilities Galactic compact objects (e. g. Cygnus X-3) Quasars and relativistic jets, GRBs

The 3 results for which AGILE will be remembered: Discovery of transient gamma-ray emission above 100 MeV from Cygnus X-3 microquasar in correlation with a repetitive pattern of multiwavelength (radio and X-ray) emission Discovery of a new acceleration mechanism inducing intense and rapid flux variations in the Crab Nebula in the energy band above 100 millions of elettronvolt! First direct evidence of cosmic ray acceleration in Supernovae remnants with the AGILE observations of the SNR W44 (2017 Matteucci Medal of the National Academy of Sciences to Marco Tavani) (topic not included in this talk)

Other results for which AGILE should be remembered: The ‘‘Crazy Diamond’’ 3C 454.3, since August 2007 and other bright gamma-ray blazars The remarkable short GRB 090510 (and the GW counterpart hunt) Transient and subsequent discovery of the ‘‘hidden black hole’’ MCW 656 in a Be star binary (topic not included in this talk) Surprises also from the Earth atmosphere: detection of Terrestrial Gamma-Ray Flashes (TGF) up to 100 MeV!! (topic not included in this talk)

Microquasars in the Cygnus region: Cygnus X-3 and Cygnus X-1 In this talk I will speak about AGILE observations of relativistic outflows at high energy from: Microquasars in the Cygnus region: Cygnus X-3 and Cygnus X-1 Crab Nebula gamma-ray flares Extreme flaring blazars: 3C 454.3 and 3C 279 The short GRB 090510 as a template for Gravitational Waves counterpart hunt

Microquasars: Galactic X-ray binary sources with radio emitting rel. jets Open questions pre-AGILE and Fermi: Can jet formation accelerate relativistic particles? Can the jet emit γ-rays above 100 MeV? The discovery of the γ-ray activity from Cygnus X-3 is the proof of extreme particle acceleration in microquasars!

Micro-quasars before the AGILE/Fermi era: The X-ray picture Cygnus X-3 Cygnus X-1 γ? S. Sabatini - Gamma-ray emission from Microquasars (Zdziarski et al. 2002) (Szostek et al., 2008)‏ Comptonization of soft thermal photons from disk by a hybrid population of electrons (thermal + non-thermal) in the corona. backward step 2 main X-ray spectral states: Soft → thermal emission (BB)‏ from disk + Comptonization by cold thermal electrons (Soft Excess) + Comptonization by non-thermal high-energy electrons (power-law tail) Hard→ Comptonized emission by hot quasi-thermal population of electrons S. Sabatini

Slide adapted from G. Piano The Cygnus region in γ-rays: AGILE Intensity Map (100 MeV-10 GeV) Pointing Mode: Nov. 2007 – Oct. 2009, ~13 Ms net exposure time SNR G78.2+2.1 (Gamma Cygni) AGILE GO pulsar (Halpern) 3 pulsars 3 TeV sources 2 microquasars Slide adapted from G. Piano 13

The γ-ray detection of Cygnus X-3: brief story of a discovery December 2, 2009: The AGILE-GRID detects 4 γ-ray flares from Cygnus X-3 (“Extreme particle acceleration in the microquasar Cygnus X-3”, Tavani et al., Nature) γ-ray flaring-fluxes greater than 1 order of magnitude with respect to the steady flux coincident with prominent minima of the hard X-ray flux a few days before major radio flares December 11, 2009: Fermi-LAT confirms AGILE detections (“Modulated High-Energy Gamma-Ray Emission from the Microquasar Cygnus X-3”, Abdo et al., Science) γ-ray detection of the orbital period (4.8 hours) → temporal signature of the microquasar In 9 days a long-lasting mystery has been solved: Cygnus X-3 is able to accelerate particles up to relativistic energies and to emit γ-rays above 100 MeV!

Major gamma-ray flares in special transitional states in preparation of radio flares! (Tavani et al, Nature 2009) 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 figure adapted from Szostek Zdziarski & McCollough (2008)

Cygnus X-1 Cygnus X-3 SPORADIC REPETITIVE PATTERN !! Compact Object 4-15 M BH 1.4 M NS or 10 M BH Companion O9.7 Supergiant, L ~ 1039 erg/s Wolf Rayet, L ~ 1039 erg/s Companion wind ~ 10-6 M/yr, v ~ 2000 km/s ~ 10-5 M☉/yr, v ~ 1000 km/s Period 5.6 days, orb. r. ~ 3.4 x 1012 cm 4.8 h, orb. r. ~ 3 x 1011 cm Inclination Angle 30? < 14 Sabatini et al. 2012 Tavani et al. Nature 2009 2 AGILE detected episodes in 2010 1 marginal FERMI detection in 2015 Hard state Hard-to-soft transition SPORADIC REPETITIVE PATTERN !! bright soft X-ray states (soft-to-hard state transitions) state preceeding strong radio flares.

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 (latest gamma-ray flares reported in March - April 2017, Fermi and AGILE ATels # 10109, 10138, 10179, 10243) Emission must be produced not to far away from the central object (4,8 hours 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 max energy previously 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

AGILE DISCOVERY OF THE CRAB NEBULA VARIABILITY IN -RAYS MOST UNEXPECTED DISCOVERY FROM THE -RAY SKY: AGILE DISCOVERY OF THE CRAB NEBULA VARIABILITY IN -RAYS Tavani et al., Science, 331, 736 (2011) Fermi confirmation: Abdo et al., Science, 331, 739 (2011)

The Crab Nebula: a spectacular cosmic accelerator THE STANDARD REFERENCE SOURCE IN ASTROPHYSICS POWERFUL PULSAR (Neutron Star rotating 30 times a sec) NEBULA SHOCKED BY THE PULSAR WIND Crab Nebula: a remnant of a supernova that exploded in AD 1054 (Chinese astronomers). X-ray data from Chandra (light blue), visible light data from Hubble (dark blue and green) and infrared data from Spitzer (red), 31/1/2001 Marco Tavani, "AGILE Discovery of Gamma-Ray flares from the Crab Nebula" 19

Updated Crab Nebula spectrum from radio to TeV Synchrotron burn-off Synchrotron emission IC Linear accelerator in ideal MHD framework Diffusive acceleration Eγ,max ≈ 25 MeV Eγ,max = 9/4 mc2/α E/B ≈ 150 MeV E/B Synchrotron burn-off (E/B<1) (De Jager et al. 92, Arons 2012) (Slide adapted from E. Striani, PhD Thesis)

The variable Crab Nebula! FIRST PUBLIC ANNOUNCEMENT Sept. 22, 2010: AGILE issues the Astronomer’s Telegram n. 2855 announcing a gamma-ray flare from the Crab Nebula Science Express (6 January 2011) Marco Tavani, "AGILE Discovery of Gamma-Ray flares from the Crab Nebula" 21

Crab Sept. 2010 flare: gamma-ray flare peak luminosity L ≈ 5·1035 erg cm-2 s-1 kin. power fraction of PSR spindown Lsd, ε ≈ 0.001 (η-1/0.1) ≈ 0.01 timescales: risetime: ≤ 1 day decay: ~ 2-3 days very efficient acceleration ! fast cooling, B, Lorentz γ

Crucial constraints on shock particle acceleration theory ! e-/e+ shock acceleration by magnetic turbulence (diffusive vs. non-diffusive) Crab Nebula shocks able to accelerate electrons/positrons at γ ~ 109 (PeV) !? Variability never observed before within a 1-day timescale

Big theoretical challenge: Flare date Duration Peak γ-ray flux Instruments October 2007 ~ 15 days ~ 6∙10-6 ph cm-2 s-1 AGILE February 2009 ~ 4∙10-6 ph cm-2 s-1 Fermi September 2010 ~ 4 days ~ 5∙10-6 ph cm-2 s-1 AGILE, Fermi April 2011 ~ 2 days ~ 30∙10-6 ph cm-2 s-1 Fermi, AGILE Other -ray flaring states seen by Fermi and AGILE: Mar and Oct 2013, Aug 2014, Oct 2016... Rate: ≈1/year Big theoretical challenge: the Crab Nebula is not a standard candle in gamma-rays! 24

Modelling of the April 2011 super-flare AGILE Fermi No apparent relation between Optical, X-ray and Gamma-ray flaring emission Mono-energetic (Maxwellian relativistic) distribution is favored power-law Maxwellian

Strong and impulsive flares (12-24 hr), ∼1/year Striani et al., ApJ 2013 Strong and impulsive flares (12-24 hr), ∼1/year Slower, less intense variability, and rather more frequent “waves” found in AGILE and Fermi data Challenge to MHD models    

South-East jet 2001 2010 Promising candidate for the gamma-ray flaring site? Remarkable time variability and jet wiggling High X-ray variability Highly magnetized plasma Kink instability in the jet could be responsible for the observed jet wiggling and trigger magnetic reconnection and particle acceleration. 3D rel. MHD simulations + resistivity: Mignone, Striani, et al. 2013-2014

Crab lessons: very exciting: the Crab Nebula is not a standard candle in gamma-rays we “lost” the stability of an ideal reference source, but gained tremendous information about the fundamental process of particle acceleration a big theoretical challenge, crucial feedback with laboratory plasma physics the ultimate source of particle enhancements in the pulsar wind needs to be established: future surprises

Gamma-ray flaring blazars: 3C 454.3, 3C 279 Ratios between optical and -rays variation factors may be AAopt > 2 or more. Compton dominance varies Gamma-ray only “orphan” flares. The Compton dominance attains values of 100 or more. Very fast variability: -flux shows doubling times of few minutes High energy spectrum can be unusually hard (and PKS 1830-211, PKS 1510 ...)

3C 279 flares show different kinds of correlation opt -  orphan = 6 = 1 = 0 = 4 3C 279 flares show different kinds of correlation opt -  The correlation is often absent. Compton dominance rises to values > 100 in few hours. Variations required in the external photon field seen by the moving blob. Mirrowing effect between plasmoids? See Vittorini et al., ApJL 2017 (Fig. from Hayashida et al. 2015)

Donnarumma

AGILE and GW astrophysics very fast reaction to external GW trigger new processing pipelines great potential for fast discovery of gamma-ray transients associated with NS-NS, NS-BH and BH-BH (if any) coalescences AGILE GW-Team monitoring shifts (24/7) during the O2 GW LIGO-Virgo observing run.

First gravitational wave event: GW150914 T0 = 9:50:45 UT, 14 September, 2015 Announced by LIGO/Virgo on Feb. 11, 2016 We learned about the event on Feb. 11, 2016 (no MoU active yet): archival search AGILE publication on the first GW event: Tavani et al., Ap.J. 825, L4 (2016) 35

AGILE-GRID in spinning: revolution including T0 of GW150914 Adapted from F. Verrecchia

AGILE field at T0 = 09:50:45 UT

AGILE just missed the T0 !

but only ~300 sec later…

AGILE exposure 330 sec (+/- 50 sec)

The “short” GRB 090510 lightcurve used as a possible HE template counterpart of the GW event AGILE and the “short” GRB 090510 ”AGILE DETECTION OF DELAYED GAMMA-RAY EMISSION FROM THE SHORT GAMMA-RAY BURST GRB 090510” A. Giuliani et al., ApJL 708, 2010 z = 0.9

AGILE and the short GRB 090510 (61 degrees off-axis) Delayed HE emission 1 2 GRID counts MCAL counts MCAL precursor < 1 MeV

AGILE and Fermi-LAT upper limits in the GRB 090510 light curve (repositioned at z = 0.1, adapted from Fermi-LAT Collab., 2016) AGILE-GRID: blu, Fermi/LAT: black, AGILE-GRID UL: red , AGILE UL extrapolation back to 1 s: green Fermi-LAT UL > 4500 s after T0 AGILE upper limit 250-350 sec after T0

4π detector AGILE-MCAL and Fermi-GBM visibility regions at the GW150914 prompt time Back: AGILE-GRID exposure map. Cross: Fermi-GBB candidate event location (about 0.4 s after T0)

AGILE-MCAL did not detect the transient reported by the Fermi GBM team AGILE-GRID provided the most stringent constraint to any delayed emission above 50 MeV shortly after (~250 sec) the GW150914 event Great potential for AGILE observations of GW error boxes: prompt, minutes, hours, days

2016-2017: AGILE in the MoU promptly reacted to GW candidate events communicated by LIGO-Virgo Several AGILE internal LVC-GCN Circulars were issued with reaction time of 2-3 hrs (including manual refined validation if data are available) 1 possible AGILE-MCAL gamma-ray transient candidate found as counterpart of the latest GW published event GW170104 Verrecchia et al. to appear in ApJL 2017, arXiv:1706.00029

GW170104 – Jan. 4 2017 AGILE gamma-ray exp map AGILE gamma-ray counts map AGILE ASI Meeting, ASI HQ, Mar 9, 2017 47 47

MCAL candidate event E2 occurring 0 MCAL candidate event E2 occurring 0.46 sec before the final BH-BH coalescence time. E2 very similar in timing and intensity to the famous 2009 precursor of GRB 090510 E2 post-trial probability between 2.5 and 3 sigma (low signif., but similar to other claims) being checked by other satellites NEW MCAL pipeline developed for “sub- threshold events” (STE) btw 4 ÷ 5 sigma pre- trial

Let’s wait for the elephant!! Thank you

EXTRA SLIDES

From S. Sabatini - Gamma-ray emission from Microquasars Cygnus X-1 Cygnus X-3 Compact Object 4-15 M BH 1.4 M NS or 10 M BH Companion O9.7 Supergiant, L ~ 1039 erg/s Wolf Rayet, L ~ 1039 erg/s Companion wind ~ 10-6 M/yr, v ~ 2000 km/s ~ 10-5 M☉/yr, v ~ 1000 km/s Period 5.6 days, orb. r. ~ 3.4 x 1012 cm 4.8 h, orb. r. ~ 3 x 1011 cm Inclination Angle 30? < 14 Cygnus X-1 (Cyg X-1) is one of the brightest X-ray sources in the sky. It is a binary system composed of a compact object and the O9.7 Iab supergiant star HDE 226868, fill- ing 97 % of its Roche Lobe, with a mass ranging be- tween ∼ 15 and ∼ 30 M⊙ (see for example Gierlin ́ski et al. 1999; Caballero-Nieves et al. 2009). The measurement of the mass of the compact object, with a range between 4.8 M⊙ and 14.7 M⊙ by Herrero et al. (1995) and 8.7±0.8 M⊙ from Shaposhnikov & Titarchuk (2007), suggests identifi- cation with a black hole. The distance to the binary system is measured as 2.1 ± 0.1 kpc by Zi ́ol􏰀kowski (2005). BECAUSE OF ITS BRIGHTNESS AND PERSISTENCY OF EMISSION, ITS OBSERVATIONAL AND THEORETICAL STUDIES HAVE BEEN OF GREAT IMPORTANCE FOR UNDERSTANDING THE PROCESS OF ACCRETION ONTO BLACK HOLES IN GENERAL Cygnus X-3 is unique in orbital separation, luminosity of the companion star and inclination -> different behaviour can be expected in the two systems From S. Sabatini - Gamma-ray emission from Microquasars

Vittorini, Tavani & Cavaliere: Mirrowing Effects in Flat Spectrum Radio Quasars

Non only gamma-rays from cosmic origin but also: surprises from the EARTH atmosphere!!

TGF Cumulative spectrum In 2011: 110 TGFs 1806 photons 142  E> 10 MeV 26  E> 20 MeV Broken powerlaw model b = -2.7 Significant detection of  >40 MeV!! Uneplained by standard RREA model: challenge for emission models RREA cutoff powerlaw model AGILE-MCAL crucial spectral contribution up to 100 MeV!! Tavani et al., Phys. Rev. Letters 106, 018501 (2011) 57 57

AGILE GRB ON-BOARD SEARCH PROCEDURE Super-A & MCAL EVENTS 8 (SA) + 12 (MCAL) DETECTOR RATEMETERS (1 ms) sub-ms search NORMAL BURST SEARCH 1 ms 16 ms 64 ms 256 ms 1.024 s 8.192 s HARDWARE HARDWARE by dedicated state-machine SOFTWARE

AGILE two "lives": pointing and spinning time period Jul.07 – Oct.09 Nov. 2009 - today attitude fixed variable (rotation ~ 0.8º/sec) sky coverage 1/5 ~ 70-80 % 1-day exposure ( 30 deg off-axis, @ 100 MeV) ~ 2 x 107 (cm2 sec) (0.5 - 1) x 107 (cm2 sec)