arXiv:1303.2039v1 [astro-ph.HE] 8 Mar 2013 orlto fmliee-aewith millimeter-wave of correlation > 21]adJrtde l 21]frPS1510 PKS for [2010] al. al. et et Jorstad Marscher and by [2010] obtained are results the Similar with imaging VLBA. mm 7 ultrahigh-resolution direct and Cn C121028 eConf h eeainof generation the Introduction 1. oteteeatv aatcnce,dpnson depends nuclei, galactic those active where extreme most 00.Tomi oain ftest of al. site et Tavecchio the of locations 2010, main al. Two Jorstad et & Agudo 2010]. Marscher [e.g., debate considerable 2011a, of subject the ini lzr aebe rpsd h rti close is first The proposed. been ( have blazars in sion rmteB,i eodte“oe hr h jet al. et of the with- region Agudo the wavelengths where scenario, locate unambiguously millimeter second [2011a] “core” this at the Supporting visible ( VLBI. beyond be farther is to much starts BH, region the a from one, second The oaigthe Locating tPre clsTruhMliSeta ag Monitoring Range Spectral Multi Through Scales Parsec at ∼ < u nesadn ftepoesslaigto leading processes the of understanding Our 4p rmteB ntejto J8 through OJ287 of jet the in BH the from pc 14 0 . 1 − nmdltn h ycrto n nes opo fluxes. Compton emis inverse multi-zone variabil and a synchrotron the of the as expectations modulating well in the as with This, agrees tim time-scales. outburst, long shorter on on together propa lin vary poorer and the curves core along the light multi-wavelength in elongated The shock disturbance, recollimation standing a a of through propagation the of 7 6 nteflxadlna oaiain swl scagsi Very in changes reprodu as we well Here as We polarization, 2008. linear [2011b]. in and with al. flux 0235+164 et the Agudo AO in in m object presented centimeter, already Lacertae at observations, outburst BL major the a of of observations present We 12 12 12 11 ocueta h ubrtocre ntejtbt ntequa the in both orderi jet of the in degree maxi at occurred the both pronounced outburst in a the fluctuations that as rapid conclude well indicate as knot, and polarization, jet arguments linear probability optical by in significance statistical high 9 8 10 1 5 4 3 2 .Wehrle E. A .S Smith S. P. .Agudo I. c otesprasv lc oe(BH). hole black supermassive the to pc) 1 ins etefrAtooywt S,Uiest fTurku, of USA University Tucson, ESO, with Arizona, Astronomy of for Centre University Finnish Observatory, Steward eateto srnm,Uiest fMcia,AnArbor Ann Michigan, of University I Astronomy, California Astrophysics, of and Astronomy Department for Center Cahill nttt eAto´sc eAdlcı,CI,Gaaa Sp Granada, CSIC, Andaluc´ıa, de Astrof´ısica de Instituto sa etnIsiueo hl,S.Ptrbr rnh St. Branch, Petersburg St. Mets University, Chile, University State of University, Petersburg Aalto Institute Boston Newton St. Isaac Research, Institute, Astrophysical Astronomical for Institute pc cec nttt,Budr USA Boulder, Institute, Georgia Abastumani, Observatory, Abastumani Science Space nttt eRdoAtoo´aMilim Astronom´ıa Cambridge, Radio Astrophysics, de for Instituto Center Harvard–Smithsonian A,Lnesenat edleg K Heidelberg, Landessternwarte ZAH, ∼ γ 0 > ry rgnt.Ti scurrently is This originate. -rays . 5mlirscn eouin h soito fteevent the of association The resolution. milliarcsecond 15 1 2presdwsra ftesprasv lc oe eint We hole. black supermassive the of downstream parsecs 12 , 2 γ .P Marscher P. A. , 6 13 ryeiso rmbaas the blazars, from emission -ray γ .Nilsson K. , .M Kurtanidze M. O. , ryFaigEiso fBaa O03+6 nteJet the in 0235+164 AO Blazar of Emission Flaring –ray 4 th hv ai bevtr,Kylm Observatory, Radio ahovi ¨ em ypsu otry A:2 c- o 2012 Nov Oct-2 28 : CA Monterey, : Symposium Fermi 7 .C .Readhead S. C. A. , γ 2 .G Jorstad G. S. , rylgtcurves light -ray 14 γ γ ryemis- -ray >> ryflares -ray − 8 and 089 tia rnd,Spain Granada, etrica, ´ ngth,Hiebr,Germany Heidelberg, onigstuhl, ¨ pc) 1 2 , 3 8 .M Larionov M. V. , .F Aller F. M. , n rpriso ai to radio a of properties and respectively. 454.3, 3C LLcra betA 2514(2514here- (0235+164 0235+164 AO after, object Lacertae BL .Observations 2. cp) rma srpyia bevtr (0.7m (0.4m University State Observatory Petersburg St. Astrophysical and Telescope), Tele- Tele- Crimean (0.84m Perkins M´artir Observatory scope), Tele- Pedro (1.83m 1.54m San Observatory scope), (2.2m and pro- Lowell (2.3 Alto MAPCAT Observatory scopes), Calar the Steward under gram), telescopes: observations following Telescope, measurements the optical (3) the from and with Telescope, observations blazar- 30m mm monthly IRAM 3 University (2) program, Boston monitoring the the with from images mm VLBA 7 (1) include 1-3) (Figs. 0235+164 t fteplrzto n h ullcto fthe of location dual the and polarization the of ity ot-al iuain.Asre fsappeaks sharp of series A simulations. Monte-Carlo inmdli hc ublnepasamjrrole major a plays turbulence which in model sion go h antcfil.Teerslsla sto us lead results These field. magnetic the of ng ae ontejtt raetespruia knot. superluminal the create to jet the down gates -cls(otsyas,bttecrepnec is correspondence the but (months/years), e-scales nAuoe l 21b eivsiaetelocation the investigate we [2011b] al. et Agudo In u ht-oaiercmntrn bevtosof observations monitoring photo-polarimetric Our u nte7m oaiaino superluminal a of polarization mm 7 the in mum fsgtb ih-rvltm eas htpasses that delays, time light-travel by sight of e nlz h iigo ut-aeadvariations multi-waveband of timing the analyze isainr oeadi h uelmnlknot, superluminal the in and core si-stationary liee,otcl -a,and X-ray, optical, illimeter, al ogBsln ra VB)iae t7mm 7 at images (VLBA) Array Baseline Long ¨ z siueo ehooy aaea USA Pasadena, Technology, of nstitute ,Finland a, ¨ otn USA Boston, t eesug Russia Petersburg, St. 0 = 9 tdffrn aead scnre at confirmed is wavebands different at s .Heidt J. , . eterslso h nlsso these of analysis the of results the ce 4,wihrslsaerpoue here. reproduced are results which 94), ain USA 3 rrtteotus saconsequence a as outburst the erpret Piikki eesug Russia Petersburg, , USA , 4 .L G L. J. , ,Finland o, ¨ 10 .Gurwell M. , omez ´ γ 1 rywavelengths –ray .L A. , γ ryotus nthe in outburst -ray 11 ahteenm .Thum C. , ¨ aki ¨ 12 5 , , 1 2 4th Fermi Symposium : Monterey, CA : 28 Oct-2 Nov 2012

Figure 1: Sequence of 7 mm VLBA images of 0235+164 convolved with a FWHM = 0.15 mas circular Gaussian beam. Contour levels represent total intensity (levels in factors of 2 from 0.4 to 51.2 % plus 90.0 % of peak= 4.93 Jy/beam), color scale indicates polarized intensity, and superimposed sticks show the orientation of χ. Reproduced from Agudo et al. [2011b].

Telescope). Our total flux light curves (Fig. 2) include ever detected in this object) propagating from the core data from the Fermi-LAT γ-ray (0.1–200 GeV) and at <βapp >= (12.6 ± 1.2) c. Swift-XRT X-ray (2.4–10 keV) observatories, avail- The ejection of Qs was coincident with the core near able from the archives of these missions, and RXTE the start of an extreme mm outburst (08mm in Fig. 2)). at 2.4–10 keV. Optical R-band fluxes come from the Figure 2 shows that radio and mm outbursts in 2008 Tuorla Blazar Monitoring Program, the Yale Univer- (08rad and 08mm) contain contributions from both the sity SMARTS program, and Maria Mitchell and Abas- core and Qs. Their contemporaneous co-evolution tumani Observatories. Longer wavelength light-curves suggests that the disturbance responsible for the ejec- were acquired from the Submillimeter Array (SMA) at tion of Qs extended from the location of the core to 850 µm and 1mm, the IRAM 30m Telescope at 1mm, Qs in the frame of the observer, which could have re- the Mets¨ahovi 14m Telescope at 8 mm, and both the sulted from light-travel delays [e.g., Agudo et al. 2001, Owens Valley Radio Observatory (OVRO) 40m Tele- G´omez et al. 1997, Mimica et al. 2009]. The rarity of scope Fermi Blazar Monitoring Program and Univer- the 08rad, 08mm, and Qs events strongly implies that sity of Michigan Radio Astronomy Observatory (UM- they are physically related. < RAO) 26m Telescope at 2cm. The jet half–opening–angle of 0235+164 [αint/2 ∼ We followed data reduction procedures described 1◦.25, see Agudo et al. 2011b] and the average FWHM in previous studies: VLBA: Jorstad et al. [2005]; of the core measured from our 31 VLBA observ- optical polarimetric data: Jorstad et al. [2010]; ing epochs in [2007,2010] (hFWHMcorei = (0.054 ± IRAM data: Agudo et al. [2006, 2010]; SMA: 0.018)mas), constrain the 7mm core to be at dcore = > Gurwell et al. [2007]; Mets¨ahovi: Ter¨asranta et al. 1.8hFWHMcorei/ tan αint ∼ 12pc from the vertex of [1998]; OVRO: Richards et al. [2011]; UMRAO: the jet cone. Aller et al. [1985]; Swift: Jorstad et al. [2010]; RXTE: Marscher et al. [2010]; and Fermi-LAT: Agudo et al. [2011a], Marscher et al. [2010]. See Agudo et al. [2011b] for further details about the X-ray and γ-ray 4. Contemporaneous Flares from γ-ray data reduction. to Radio Wavelengths

Figure 2 reveals that the 08rad and 08mm flares 3. Major Millimeter Flare in 2008 Related were accompanied by sharp optical, X–ray, and γ-ray counterparts (08opt, 08X, and 08γ flares, respectively). to a New Superluminal Knot Our formal light-curve correlation analysis (Fig. 4) –performed following Agudo et al. [2011a]– confirms We model the brightness distribution of the source the association of γ-ray variability with that at 2 cm, at 7 mm with a small number of circular Gaussian 8 mm, 1 mm, and optical wavelengths at > 99.7% con- components (Fig. 1). Our model fits include a bright fidence. The flux evolution of the VLBI core is also superluminal feature (Qs, the brightest jet feature correlated with the γ-ray light curve at > 99.7% con- eConf C121028 4th Fermi Symposium : Monterey, CA : 28 Oct-2 Nov 2012 3

Coordinated Universal Time [years] Coordinated Universal Time [years] 2003 2004 2005 2006 2007 2008 2009 2010 2011 2008.5 2009.0 /s] /s] 2 2 0.1-200 GeV 0.1-200 GeV 15 15 08γ 10 10 phot/cm phot/cm -7 -7 5 5 [10 [10

F 0 F 0 /s] /s] 2 2 15 2.4-10 keV 15 2.4-10 keV 07X 08X 10 10 erg/cm erg/cm -12 -12 5 5 [10 [10

F 0 F 0 -1.0 -1.0 -1.2 2.4-10 keV-1.2 2.4-10 keV -1.4 -1.4 -1.6 -1.6 -1.8 -1.8 -2.0 -2.0 (photon index) (photon index)

Γ -2.2 Γ -2.2 6 R 6 R 07opt 08opt 4 4 [mJy] [mJy]

S 2 S 2 0 0 6 07 08 3mm 6 3mm mm mm 1mm 1mm 4 850µm 4 850µm [Jy] [Jy] S S 2 2 0 0

6 07rad 08rad 8mm 6 8mm 7mm VLBA 7mm VLBA 4 7mm Core 4 7mm Core [Jy] 7mm Qs[Jy] 7mm Qs S S 2 2cm 2 2cm 0 0 52500 53000 53500 54000 54500 55000 5550054500 54600 54700 54800 54900 55000 RJD [days] RJD [days]

Figure 2: Left: Light curves of 0235+164 from γ-ray to millimeter wavelengths. X-ray photon index evolution from the Swift-XRT data is also plotted. Vertical dotted lines mark the three most prominent 08opt optical peaks. The yellow area represents the time of ejection of feature Qs within its uncertainty. RJD = Julian Date − 2400000.0. Right: Same as left panel for RJD∈ [54500, 55000]. Reproduced from Agudo et al. [2011b].

fidence. Moreover, the evolution of the degree of op- degree of linear polarization (pmm) and that of the < tical linear polarization (popt) and X-ray light curve 7 mm core remain at moderate levels ∼ 5 %, the po- are also correlated with the optical R-band, 1 mm, larization of Qs (pmm,Qs) peaks at the high value of and 2 cm light curves at > 99.7 % confidence (Fig. 5), ∼ 16% close to the time of the second sharp opti- further indicating that the extreme flaring activity re- cal sub-flare. The coincidence of this sharp maximum vealed by our light curves is physically related at all of pmm,Qs in the brightest superluminal feature ever wavebands from radio to γ-rays. detected in 0235+164 with the (1) high optical flux There is, however, no common pattern to the dis- and polarization, (2) flares across the other spectral crete correlation function (DCF) at all spectral ranges. regimes, and (3) flare in the 7-mm VLBI core, implies This implies that, although there is correlation on long that the ejection and propagation of Qs in 0235+164’s < time-scales (years), on short time-scales (∼ 2 months) jet is physically tied to the total flux and polarization the variability pattern does not correspond as closely. variations from radio to γ-rays. This is the result of the intrinsic variability pattern On long time-scales (years), the linear polarization rather than the irregular time sampling at some spec- angle at both optical (χopt) and millimeter (χmm and tral ranges. core χmm ) wavelengths varies wildly, without a preferred orientation or systematic common trend. However, during flare 08opt, χopt maintains a stable orientation 5. Correlated Variability of Linear ◦ Qs at (100 ± 20) , whereas χmm is roughly perpendicular Polarization to this (∼ 0◦), as expected for a plane-perpendicular shock wave propagating to the south towards Qs. Ow- max Figure 3 reveals extremely high, variable optical po- ing to the large peak value of Qs, pmm,Qs ∼ 16 %, > larization, popt ∼ 30 %, during the sharp 08opt opti- one cannot explain the orthogonal optical-millimeter cal peaks. Whereas the integrated millimeter-wave polarizations by opacity effects. Instead, we propose eConf C121028 4 4th Fermi Symposium : Monterey, CA : 28 Oct-2 Nov 2012

Coordinated Universal Time [years] Coordinated Universal Time [years] 2007 2008 2009 2010 2011 2008.5 2009.0 40 Optical 40 Optical 30 30 [%] 20 [%] 20 p p 10 10 0 0 7mm Core mm 7mm Core mm 15 7mm Qs 15 7mm Qs 7 & 3mm 7 & 3mm 10 [%] 10 [%] p p 5 5

0 0 250 250 Optical Optical 200 200 150 150 ] ] o o

[ 100 [ 100 χ 50 χ 50 0 0 -50 -50 300 7mm Core mm 300 7mm Core mm 7mm Qs 7mm Qs 200 7 & 3mm 200 7 & 3mm ] ] o o [ 100 [ 100 χ χ 0 0 -100 -100 54000 54500 55000 55500 54550 54600 54650 54700 54750 54800 54850 RJD [days] RJD [days]

Figure 3: Left: Long term optical and millimeter-wave linear polarization evolution of 0235+164 in the RJD=[54000,55600] range. Right: Same as left panel for RJD∈ [54530, 54850]. Reproduced from Agudo et al. [2011b].

that the optical polarization mainly arises in a con- 7. Observational Evidences ical shock associated with the 7-mm core, while the millimeter-wave polarization results from a propagat- The coincidence of the ejection and propagation ing shock front associated with Qs. We surmise that of Qs –by far the brightest non-core feature ever re- the moving shock also emits polarized optical radia- ported in 0235+164– with the prominent γ-ray to ra- tion, since the optical polarization drops precipitously dio outbursts and the extremely high values of popt when the orthogonal polarization of Qs peaks (Fig. 3- and pmm,Qs provides convincing evidence that all these right). events are physically connected. This is supported by probability arguments and by our formal DCF analy- sis, which unambiguously confirms the relation of the γ-ray outburst in late 2008 with those in the opti- cal, millimeter-wave (including the 7-mm VLBI core) 6. Low Probability of Chance and radio regimes. We locate the millimeter core at > Coincidences dcore ∼ 12 pc from the vertex of the jet.

The relationship among the γ-ray, optical, and 8. Conclusions radio-millimeter flares is supported by probability ar- guments. If the flares occur randomly, the probability We identify the 7-mm core as the first re-collimation of observing, at any time, a γ-ray outburst like the one shock near the end of the jet’s acceleration and colli- > −6 −2 −1 reported here (i.e., with flux ∼ 10 phot cm s mation zone [ACZ Jorstad et al. 2007, Marscher et al. and duration ∼ 70 days) is pγ = 0.08. For optical 2008, 2010]. Superluminal feature Qs is consistent and radio–millimeter wavelengths, this probability is with a moving shock oriented transverse to the jet Qs popt = 0.04 and pmm = 0.15, respectively. Thus, if axis, given the extremely high pmm,Qs, with χmm par- the flares at different wavelengths were random and allel to the direction of propagation of Qs. The flux independent of each other, the probability of observ- evolution of the core appears closely tied to that of Qs, ing a γ-ray, optical, and radio-millimeter flare at any and its light curve is correlated at high confidence with −4 given time is pγ,opt,mm = 5 × 10 . This counters those at γ-ray, optical, and millimeter wavelengths. the null hypothesis of random coincidence at 99.95 % This suggests that Qs is the head of an extended dis- confidence. turbance, perhaps containing a front-back structure eConf C121028 4th Fermi Symposium : Monterey, CA : 28 Oct-2 Nov 2012 5

2 2 2 2

1 1 1 1

0 0 0 0 DCF

-1 -1 -1 -1

-2 γ - 2cm -2 γ - 1mm -2 γ - 7mm Core -2 γ - R-band

-200 -100 0 100 200-200 -100 0 100 200-200 -100 0 100 200-200 -100 0 100 200 3 3 3 3

2 2 2 2

1 1 1 1

0 0 0 0 DCF

-1 -1 -1 -1

-2 -2 -2 -2

-3 R-band - 2cm -3 R-band - 1mm-3 R-band - 7mm Core -3 R-band - X

-200 -100 0 100 200-200 -100 0 100 200-200 -100 0 100 200-200 -100 0 100 200 Time Delay [days] Time Delay [days] Time Delay [days] Time Delay [days]

Figure 4: Grid of DCF of labeled light-curve pairs during the maximum time period RJD = [52200, 55600]. Top row of panels show DFC with γ-ray light-curve, whereas bottom row show DCF with R-band light-curve. Grey dotted curves at positive (negative) DCF values symbolize 99.7 % confidence limits for correlation against the null hypothesis of stochastic variability. Green dashed lines at 0 and −50 day time–lags are drawn for reference. Reproduced from Agudo et al. [2011b].

2 2 2 2

1 1 1 1

0 0 0 0 DCF

-1 -1 -1 -1

-2 -2 -2 -2 1mm - 2cm 1mm - 7mm Core 1mm - p_opt 1mm - X

-200 -100 0 100 200-200 -100 0 100 200-200 -100 0 100 200-200 -100 0 100 200 2 2 2 2

1 1 1 1

0 0 0 0 DCF

-1 -1 -1 -1

-2 2cm - 7mm Core -2 2cm - R-band -2 2cm - p_opt -2 2cm - X

-200 -100 0 100 200-200 -100 0 100 200-200 -100 0 100 200-200 -100 0 100 200 Time Delay [days] Time Delay [days] Time Delay [days] Time Delay [days]

Figure 5: Same as Fig. 4 but for the 1 mm light-curve (top) and the 2 cm light-curve (bottom). Reproduced from Agudo et al. [2011b]. stretched by light-travel delays in the observer’s frame plasma in the back structure through the core. Dur- [see, e.g., Aloy et al. 2003]. ing the different optical sub–flares, the integrated ra- dio/millimeter synchrotron flux keeps rising. This ra- Under this scenario, the radio/millimeter-wave and dio/millimeter outburst is more prolonged owing to optical (and perhaps X-ray) synchrotron flares start the longer synchrotron cooling-time of electrons radi- when the front region crosses the conical shock at ating at these wavelengths and the lower speed of the the core, where the jet is at least partially optically back structure. Indeed, Qs does not reach its maxi- thin (Fig. 6). This interaction accelerates electrons, mum radio/millimeter-wave flux until traveling a pro- and produces inverse Compton γ-ray emission from jected distance of ∼ 0.13 mas from the core. When the up-scattering of IR-optical photons. When the the entire front-back structure passes across the core, back region of the moving perturbation encounters the synchrotron emission declines rapidly at optical the core, their interaction again produces efficient par- (and, if relevant, X-ray) frequencies, as does the γ- ticle acceleration, which is seen as a sudden optical ray emission. The decay of the radio/millimeter-wave and radio/millimeter synchrotron emission enhance- emission is more gradual (see above). ment. The subsequent optical variability is produced by the passage of the remaining shocked turbulent eConf C121028 6 4th Fermi Symposium : Monterey, CA : 28 Oct-2 Nov 2012

Figure 6: Scheme of proposed model for the multi-wavelength flaring behavior of AO 0235+164. Radio-loud AGN sketch adapted from Marscher [ 2006].

Acknowledgments Agudo, I., et al. 2011a, ApJL, 726, L13 Agudo, I., et al. 2011b, ApJL, 735, L10 We acknowledge the anonymous referee for con- Aller, H. D., Aller, M. F., Latimer, G. E., & Hodge, structive comments. This research was funded P. E. 1985, ApJS, 59, 513 by NASA grants NNX08AJ64G, NNX08AU02G, Aloy, M.-A.,´ Mart´ı, J.-M., G´omez, J.-L., Agudo, I., NNX08AV61G, and NNX08AV65G, NSF grant AST- M¨uller, E., & Ib´a˜nez, J.-M. 2003, ApJL, 585, L109 0907893, and NRAO award GSSP07-0009 (Boston G´omez, J. L., Mart´ı,J.-M., Marscher, A. P., Ib´a˜nez, University); RFBR grant 09-02-00092 (St. Petersburg J.-M. & Alberdi, A. 1997, ApJL, 482, L33 State University); MICIIN grant AYA2010-14844, and Gurwell, M. A., Peck, A. B., Hostler, S. R., Darrah, CEIC (Andaluc´ıa) grant P09-FQM-4784 (IAA-CSIC); M. R., & Katz, C. A. 2007, in ASP Conf. Ser. 375, the Academy of Finland (Mets¨ahovi); NASA grants From Z-Machines to ALMA: (Sub)millimeter Spec- NNX08AW56S and NNX09AU10G (Steward Obser- troscopy of Galaxies, ed. A. J. Baker et al. (San vatory); and GNSF grant ST08/4-404 (Abastunami Francisco, CA: ASP), 234 Observatory). The VLBA is an instrument of the Jorstad, S. G., et al. 2005, ApJ, 130, 1418 NRAO, a facility of the NSF under cooperative agree- Jorstad, S. G., et al. 2007, AJ, 134, 799 ment by AUI. The PRISM camera was developed by Jorstad, S. G., et al. 2010, ApJ, 715, 362 Janes et al., and funded by NSF, Boston University, Marscher, A. P., & Jorstad, S. G. 2010, in Fermi and Lowell Observatory. Calar Alto Observatory is Meets Jansky–AGN at Radio and Gamma-rays, ed. operated by MPIA and IAA-CSIC. The IRAM 30m T. Savolainen et al. (Bonn: Max-Planck-Institute Telescope is supported by INSU/CNRS, MPG, and F¨ur Radioastronomie), 171 IGN. The SMA is a joint project between the SAO Marscher, A. P. 2006, in: Relativistic Jets: The Com- and the Academia Sinica. mon Physics of AGN, Microquasars, and Gamma- Ray Bursts. AIP Conference Proceedings, 856, 1 Marscher, A. P., et al. 2008, Nature, 452, 966 Marscher, A. P., et al. 2010, ApJ, 710, L126 References Mimica, P., et al. 2009, ApJ, 696, 1142 Richards, J. L., et al. 2011, ApJS, 194, 29 Agudo, I., G´omez, J.-L., Mart´ı, J.-M., Ib´a˜nez, J.- Tavecchio, F., Ghisellini, G., Bonnoli, G., & M., Marscher, A. P., Alberdi, A., Aloy, M.-A., & Ghirlanda, G. 2010, MNRAS, 405, L94 Hardee, P. E. 2001, ApJL, 549, L183 Ter¨asranta, H., et al. 1998, AASS, 132, 305 Agudo, I., et al. 2006, A&A, 456, 117 Agudo, I., Thum, C., Wiesemeyer, H., & Krichbaum, T. P. 2010, ApJS, 189, 1

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