Multiwavelength observations of the gamma-ray blazars detected by AGILE Filippo D’Ammando INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Roma INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Roma Università degli Studi di Roma “Tor Vergata” Università degli Studi di Roma “Tor Vergata” Ph.D in Astronomy - Cycle XXII Roman Young Researchers Meeting 2009

Active Galactic Nuclei - Unification Model central Black Hole ( M ʘ ) accretion disk rotating around the SMBH clouds of gas gravitational attracted by the black hole and illuminated by the disk radiation optically thick torus of molecular gas and dust two collimated relativistic jets Urry and Padovani 1995 RYRM 2009 Filippo D’Ammando 21 July 2009

Almost all galaxies contains a massive black hole but 99% of them are silent and 1% is active (mostly radio-quiet AGNs)... and only 0.1% is radio-loud AGNs Blazar characteristics: - compact radio core, flat or inverted spectrum - apparent superluminal motion - irregular, rapid and often very large variability at all frequencies - high and variable polarization at optical and radio frequencies RYRM 2009 Filippo D’Ammando 21 July 2009

Emission mechanisms in blazars Leptonic processes: - synchrotron emission - inverse Compton where seed photons came from the internal synchrotron radiation - inverse Compton where seed photons came from external radiation (accretion disk, BLR and/or torus) Hadronic processes: - synchrotron emission - proton-initiated cascades - proton-synchrotron emission RYRM 2009 Filippo D’Ammando 21 July 2009

Synchrotron SSC Synchrotron Self-Compton (SSC) Electrons in a magnetic field can work twice: first producing synchrotron radiation, and then Comptonizing it (SSC) RYRM 2009 Filippo D’Ammando 21 July 2009

Sikora, Begelman and Rees 1994 In External Compton model the seed photons come from outside to the jet RYRM 2009 Filippo D’Ammando 21 July 2009

The blazar (spectral) sequence Fossati et al Donato et al FSRQ BL Lac E pk of synchrotron and Compton components inversely correlated with L L peak RYRM 2009 Filippo D’Ammando 21 July 2009

Low power slow cooling large ɣ peak cooling small peak Big power fast cooling small ɣ peak Ghisellini et al. 1998, 2002 RYRM 2009 Filippo D’Ammando 21 July 2009

Giuliani, D’Ammando, Vercellone, et al. 2009, A&A, 494, 509 First extragalactic source detected in gamma-ray by AGILE-GRID, monitored simultaneously in optical band by REM telescope and in X-rays by Swift = (210  38) ph cm -2 s -1 E > 100 MeV Gamma-ray flux similar to the EGRET high state but soft spectrum The soft spectrum during a flaring episode could be an indication of a dominant contribution of EDC emission compared to ECC emission model July 2007 First AGILE multi-λ campaign: 3C 279 ECD ECC RYRM 2009 Filippo D’Ammando 21 July 2009

R-band light curve between December 2006 and December 2007: a strong minimum occurred about 2 months before the AGILE observation This optical minimum might be correlated with a low accretion state of the disk and then with a ECC component deficit, delayed of about two months Hartman et al RYRM 2009 Filippo D’Ammando 21 July 2009

Pucella, Vittorini, D’Ammando, et al. 2008, A&A, 491, L21 = (195  30) ph cm -2 s -1 E >100 MeV Possible correlation between optical and gamma-ray bands: contemporaneous decrease in fluxes The IC contribution from the BLR can explain the observed hard gamma-ray spectrum 23 August - 1 September 2007 PKS RYRM 2009 Filippo D’Ammando 21 July 2009

D’Ammando, Pucella, Raiteri, et al., submitted to A&A Serendipitous detection during an AGILE pointing towards the Galactic Center 3 ToO by Swift/XRT: the spectrum becomes harder when the source is brighter GASP-WEBT observed intense optical activity between January and April March 2008 PKS : a rapid gamma-ray flare in March 2008 RYRM 2009 Filippo D’Ammando 21 July 2009

Between January and April 2008, the blazar PKS showed intense optical activity with several episodes of fast variability detected by GASP - WEBT Peaks was detected in the optical band on 15 February, 29 March and 11 April 2008 After two episodes of medium intensity the source was not detected for some days in gamma-ray band and suddenly a rapid flare was observed by AGILE on March 2008 RYRM 2009 Filippo D’Ammando 21 July 2009

Radio-to-optical behaviour The light curve at GHz suggests that the mechanism producing the flaring event observed in optical in the second half of February and in late March-April 2008 also interested the millimetric emitting zone, with some delay At GHz a hint of flux increase is visible in the second part of the light curve, while the radio flux at 5-15 GHz shows no trend RYRM 2009 Filippo D’Ammando 21 July 2009

Spectral Energy Distribution - March 2008 Likely signatures of the little and big blue bumps hard X-ray spectrum: soft X-ray excess? RYRM 2009 Filippo D’Ammando 21 July 2009

PKS showed an extraordinary gamma-ray activity during March 2009, with several flaring episodes D’Ammando et al., in preparation PKS March 2009 RYRM 2009 Filippo D’Ammando 21 July 2009

GASP observations of PKS During March 2009 the optical activity of PKS is greatly increased with a peak on 26 March 2009 D’Ammando et al., in preparation RYRM 2009 Filippo D’Ammando 21 July 2009

Chen, D’Ammando, Villata, et al. 2008, A&A, 489, L37 = (97  15) ph cm -2 s -1 E >100 MeV with a peak level of (193  42) ph cm -2 s -1 z = 0.31  0.08 (Nilsson et al., 2008) Total power transported in the jet is extremely high ( L tot > 3 x erg s -1 ), at the limit of the maximum power generated by a spinning black hole of 10 9 M ʘ September 2007 S in September - October 2007 RYRM 2009 Filippo D’Ammando 21 July 2009

The Discrete Correlation Function (DCF) displays a significant peak for a time-lag of -1 day Possible delay in the gamma-ray flux variations with respect to optical variations of the order of 1 day To fit the SED we use 2 different SSC components: - the first component reproduces the ground state - the second components dominates the optical and gamma-ray bands RYRM 2009 Filippo D’Ammando 21 July 2009

Giommi, Colafrancesco, Cutini, et al., 2008, A&A, 487, L49 = (47 ± 11) ph cm -2 s -1 E >100 MeV The gamma-ray flux is about a factor of 2 lower than in September Strong variability in soft X-ray, moderate variability at optical/UV and approximately constant behavior in hard X-rays The SED is consistent with a two-components SSC model 23 October - 13 November 2007 Swift and AGILE simultaneous obs. in October - November 2007 RYRM 2009 Filippo D’Ammando 21 July 2009

Pacciani, Donnarumma, Vittorini, et al. 2009, A&A, 494, 49 = (22  6) ph cm -2 s -1 E >100 MeV F ɣ [peak] = (33 11) ph cm -2 s -1 E >100 MeV Multi-wavelength campaign: REM, Swift, RXTE, INTEGRAL and AGILE No optical variability during the entire campaign. Hint of a possible anti-correlated variability between X-rays and gamma-rays SSC + EC: spectral variability consistent with an acceleration episode of the electron population 16 December 2007 – 8 January C 273: simultaneous detection by GRID & SA RYRM 2009 Filippo D’Ammando 21 July 2009

Vercellone, Chen, Giuliani, et al. 2008, ApJL, 676, 13 AGILE repointing the source during a period of strongly enhanced optical emission = (280 ± 40) ph cm -2 s -1 E >100 MeV Highest gamma-ray flux from this source in the last 15 years but see Fermi obs. 3C 454.3: July July 2007 RYRM 2009 Filippo D’Ammando 21 July 2009

MW Observations of 3C in November November - 1 December 2007 Vercellone, Chen, Vittorini, Giuliani, D’Ammando et al. 2009, ApJ, 690, 1018 = (170  13) ph cm -2 s -1, with a peak of ~400 x ph cm -2 s -1 E >100 MeV Rapid variability in the optical band Emission in the optical range appears to be correlated with that at gamma-ray energies The DCF indicate a moderate correlation with no lag between gamma-ray and optical flux variations RYRM 2009 Filippo D’Ammando 21 July 2009

The contribution of ECD radiation alone cannot account for the hardness of the spectrum. The gamma-ray emission seems to be dominated by IC scattering of the external photons from the broad line region clouds ECD ECC RYRM 2009 Filippo D’Ammando 21 July 2009

MW Observations of 3C in December 2007 Donnarumma et al., 2009, submitted to ApJ Simultaneous multi-wavelength campaign with the contribution of Spitzer, REM, GASP- WEBT, MITSuME, Swift, Suzaku and AGILE = ~ 250 x ph cm -2 s -1 E >100 MeV A leptonic EC model is considered, with also a contribution of EC on a hot corona (T=10 6 K), to account for the hard ɣ -ray spectrum

RYRM 2009 Filippo D’Ammando 21 July 2009 DCF analysis shows a (possible) delay of the gamma-ray flux variations with respect to the optical ones of about 10 hours The longest monitor so far of a blazar in the gamma-ray band A factor of about 10 in dynamic range in about 2 years with a possible spectral trend (harder when brighter) Vercellone et al., in preparation

Mrk 421: WEBT + AGILE + VERITAS + MAGIC = … RYRM 2009 Filippo D’Ammando 21 July 2009

Donnarumma, Vittorini, Vercellone et al., 2009, ApJ 691, L13 = (42 ± 13) ph cm -2 s -1 E >100 MeV Swift/XRT: Flux ( keV) = 2.6 x ph cm -2 s -1 Possible correlated variability between optical, X-rays and high-energy parts of the spectrum SSC model: hardening/softening of electron energy distribution caused by particle acceleration process Mrk 421 from optical to TeV energies

Summary and remarks Gamma-ray astronomy is still a largely unexplored territory, in particular for the class of blazars AGILE (and EGRET) detected only few objects with flux greater than 100 x ph cm -2 s -1 ? Why? Selection effects or there is a subclass of blazar with peculiar characteristics? SSC vs EC vs more complex models? How to distinguish? AGILE observations has brought to light a more complex behaviour of blazars with respect to the standard models: - the presence of two emission components in any BL Lacs - the possible contributions of an hot corona as source of seed photons for the EC in FSRQs The study of multi-wavelength correlations is the key to understanding the structure of the inner jet and the origin of the seed photons for the IC process The study of sources in different activity states, not only during flaring states, could provide new informations

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