The June 2008 Flare of Markarian 421 from Optical to TeV Energies

none295siWe present optical to very-high energy (VHE) gamma-ray observations of Mrk 421 between 2008 May 24 and June 23. A high-energy (HE) gamma-ray signal was detected by AGILE-GRID during June 9-15, brighter than the average flux observed by EGRET in Mrk 421 by a factor of approx. 1.5. In 20-60 keV X-rays, a large-amplitude 5-day flare (June 9-15) was resolved with a maximum flux of approx. 55 mCrab. SuperAGILE, RXTE/ASM and Swift/BAT data show a clearly correlated flaring structure between soft and hard X-rays, with a high flux/amplitude variability in hard X-rays. Hints of the same flaring behavior is also detected in the simultaneously recorded GASP-WEBT optical data. A target of opportunity observation by Swift near the flare maximum on June 12-13 revealed the highest 2-10 keV flux ever observed (>100 mCrab) and a peak synchrotron energy of approx. 3 keV, a large shift from typical values of 0.5-1 keV. Observations at VHE (E>200 GeV) gamma-rays during June 6-8 show the source flux peaking in a bright state, well correlated with the simultaneous peak in the X-rays. The gamma-ray flare can be interpreted within the framework of the Synchrotron Self Compton model in terms of a rapid acceleration of leptons in the jet.mixedDonnarumma I; Vittorini V; Vercellone S; del Monte E; Feroci M; DAmmando F; Pacciani L; Chen A W; Tavani M; Bulgarelli A; Giuliani A; Longo F; Pucella G; Argan A; Barbiellini G; Boffelli F; Caraveo P; Cattaneo P W; Cocco V; Costa E; DeParis G; Di Cocco G; Evangelista Y; Fiorini M; Froysland T; Frutti M; Fuschino F; Galli M; Gianotti F; Labanti C; Lapshov I; Lazzarotto F; Lipari P; Marisaldi M; Mastropietro M; Mereghetti S; Morelli E; Morselli A; Pellizzoni A; Perotti F; Picozza P; Porrovecchio G; Prest M; Rapisarda M; Rappoldi A; Rubini A; Soffitta P; Trifoglio M; Trois A; Vallazza E; Zambra A; Zanello D; Pittori C; Santolamazza P; Verrecchia F; Giommi P; Colafrancesco S; Salotti L; Villata M; Raiteri C M; Chen W P; Efimova N V; Jordan B; Konstantinova T S; Koptelova E; Kurtanidze O M; Larionov V M; Ros J A; Sadun A C; Anderhub H; Antonelli L A; Antoranz P; Backes M; Baixeras C; Balestra S; Barrio J A; Bartko H; Bastieri D; González J Becerra; Becker J K; Bednarek W; Berger K; Bernardini E; Biland A; Bock R K; Bonnoli G; Bordas P; Tridon D Borla; Bosch-Ramon V; Bretz T; Britvitch I; Camara M; Carmona E; Chilingarian A; Commichau S; Contreras J L; Cortina J; Costado M T; Covino S; Curtef V; Dazzi F; DeAngelis A; DeCea del Pozo E; de los Reyes R; DeLotto B; DeMaria M; DeSabata F; Mendez C Delgado; Dominguez A; Dorner D; Doro M; Elsaesser D; Errando M; Ferenc D; Fernández E; Firpo R; Fonseca M V; Font L; Galante N; García López R J; Garczarczyk M; Gaug M; Goebel F; Hadasch D; Hayashida M; Herrero A; Höhne-Mönch D; Hose J; Hsu C C; Huber S; Jogler T; Kranich D; La Barbera A; Laille A; Leonardo E; Lindfors E; Lombardi S; López M; Lorenz E; Majumdar P; Maneva G; Mankuzhiyil N; Mannheim K; Maraschi L; Mariotti M; Martínez M; Mazin D; Meucci M; Meyer M; Miranda J M; Mirzoyan R; Moldón J; Moles M; Moralejo A; Nieto D; Nilsson K; Ninkovic J; Oya I; Paoletti R; Paredes J M; Pasanen M; Pascoli D; Pauss F; Pegna R G; Perez-Torres M A; Persic M; Peruzzo L; Prada F; Prandini E; Puchades N; Raymers A; Rhode W; Ribó M; Rico J; Rissi M; Robert A; Rügamer S; Saggion A; Saito T Y; Salvati M; Sanchez-Conde M; Sartori P; Satalecka K; Scalzotto V; Scapin V; Schweizer T; Shayduk M; Shinozaki K; Shore S N; Sidro N; Sierpowska-Bartosik A; Sillanpää A; Sitarek J; Sobczynska D; Spanier F; Stamerra A; Stark L S; Takalo L; Tavecchio F; Temnikov P; Tescaro D; Teshima M; Tluczykont M; Torres D F; Turini N; Vankov H; Venturini A; Vitale V; Wagner R M; Wittek W; Zabalza V; Zandanel F; Zanin R; Zapatero J; Acciari V; Aliu E; Arlen T; Beilicke M; Benbow W; Bradbury S M; Buckley J H; Bugaev V; Butt Y; Byrum K; Cannon A; Cesarini A; Chow Y C; Ciupik L; Cogan P; Colin P; Cui W; Daniel M K; Dickherber R; Duke C; Ergin T; Fegan S J; Finley J P; Finnegan G; Fortin P; Furniss A; Gall D; Gillanders G H; Guenette R; Gyuk G; Grube J; Hanna D; Holder J; Horan D; Hui C M; Humensky T Brian; Imran A; Kaaret P; Karlsson N; Kertzman M; Kieda D; Kildea J; Konopelko A; Krawczynski H; Krennrich F; Lang M J; LeBohec S; Maier G; McCann A; McCutcheon M; Milovanovic A; Moriarty P; Nagai T; Ong R A; Otte A N; Pandel D; Perkins J S; Pichel A; Pohl M; Ragan K; Reyes L C; Reynolds P T; Roache E; Rose H J; Schroedter M; Sembroski G H; Smith A W; Steele D; Swordy S P; Theiling M; Toner J A; Valcarcel L; Varlotta A; Wakely S P; Ward J E; Weekes T C; Weinstein A; Williams D A; Wissel S; Wood M; Zitzer BDonnarumma I; Vittorini V; Vercellone S; del Monte E; Feroci M; DAmmando F; Pacciani L; Chen A W; Tavani M; Bulgarelli A; Giuliani A; Longo F; Pucella G; Argan A; Barbiellini G; Boffelli F; Caraveo P; Cattaneo P W; Cocco V; Costa E; DeParis G; Di Cocco G; Evangelista Y; Fiorini M; Froysland T; Frutti M; Fuschino F; Galli M; Gianotti F; Labanti C; Lapshov I; Lazzarotto F; Lipari P; Marisaldi M; Mastropietro M; Mereghetti S; Morelli E; Morselli A; Pellizzoni A; Perotti F; Picozza P; Porrovecchio G; Prest M; Rapisarda M; Rappoldi A; Rubini A; Soffitta P; Trifoglio M; Trois A; Vallazza E; Zambra A; Zanello D; Pittori C; Santolamazza P; Verrecchia F; Giommi P; Colafrancesco S; Salotti L; Villata M; Raiteri C M; Chen W P; Efimova N V; Jordan B; Konstantinova T S; Koptelova E; Kurtanidze O M; Larionov V M; Ros J A; Sadun A C; Anderhub H; Antonelli L A; Antoranz P; Backes M; Baixeras C; Balestra S; Barrio J A; Bartko H; Bastieri D; González J Becerra; Becker J K; Bednarek W; Berger K; Bernardini E; Biland A; Bock R K; Bonnoli G; Bordas P; Tridon D Borla; Bosch-Ramon V; Bretz T; Britvitch I; Camara M; Carmona E; Chilingarian A; Commichau S; Contreras J L; Cortina J; Costado M T; Covino S; Curtef V; Dazzi F; DeAngelis A; DeCea del Pozo E; de los Reyes R; DeLotto B; DeMaria M; DeSabata F; Mendez C Delgado; Dominguez A; Dorner D; Doro M; Elsaesser D; Errando M; Ferenc D; Fernández E; Firpo R; Fonseca M V; Font L; Galante N; García López R J; Garczarczyk M; Gaug M; Goebel F; Hadasch D; Hayashida M; Herrero A; Höhne-Mönch D; Hose J; Hsu C C; Huber S; Jogler T; Kranich D; La Barbera A; Laille A; Leonardo E; Lindfors E; Lombardi S; López M; Lorenz E; Majumdar P; Maneva G; Mankuzhiyil N; Mannheim K; Maraschi L; Mariotti M; Martínez M; Mazin D; Meucci M; Meyer M; Miranda J M; Mirzoyan R; Moldón J; Moles M; Moralejo A; Nieto D; Nilsson K; Ninkovic J; Oya I; Paoletti R; Paredes J M; Pasanen M; Pascoli D; Pauss F; Pegna R G; Perez-Torres M A; Persic M; Peruzzo L; Prada F; Prandini E; Puchades N; Raymers A; Rhode W; Ribó M; Rico J; Rissi M; Robert A; Rügamer S; Saggion A; Saito T Y; Salvati M; Sanchez-Conde M; Sartori P; Satalecka K; Scalzotto V; Scapin V; Schweizer T; Shayduk M; Shinozaki K; Shore S N; Sidro N; Sierpowska-Bartosik A; Sillanpää A; Sitarek J; Sobczynska D; Spanier F; Stamerra A; Stark L S; Takalo L; Tavecchio F; Temnikov P; Tescaro D; Teshima M; Tluczykont M; Torres D F; Turini N; Vankov H; Venturini A; Vitale V; Wagner R M; Wittek W; Zabalza V; Zandanel F; Zanin R; Zapatero J; Acciari V; Aliu E; Arlen T; Beilicke M; Benbow W; Bradbury S M; Buckley J H; Bugaev V; Butt Y; Byrum K; Cannon A; Cesarini A; Chow Y C; Ciupik L; Cogan P; Colin P; Cui W; Daniel M K; Dickherber R; Duke C; Ergin T; Fegan S J; Finley J P; Finnegan G; Fortin P; Furniss A; Gall D; Gillanders G H; Guenette R; Gyuk G; Grube J; Hanna D; Holder J; Horan D; Hui C M; Humensky T Brian; Imran A; Kaaret P; Karlsson N; Kertzman M; Kieda D; Kildea J; Konopelko A; Krawczynski H; Krennrich F; Lang M J; LeBohec S; Maier G; McCann A; McCutcheon M; Milovanovic A; Moriarty P; Nagai T; Ong R A; Otte A N; Pandel D; Perkins J S; Pichel A; Pohl M; Ragan K; Reyes L C; Reynolds P T; Roache E; Rose H J; Schroedter M; Sembroski G H; Smith A W; Steele D; Swordy S P; Theiling M; Toner J A; Valcarcel L; Varlotta A; Wakely S P; Ward J E; Weekes T C; Weinstein A; Williams D A; Wissel S; Wood M; Zitzer