Fermi-Jansky: Our evolving understanding of AGN Saint Michaels, MD - November 10-12 2011 Meeting Blazar observations above 100 GeV with VERITAS Manel Errando Title (Barnard College / Columbia University) • TeV blazars • The VERITAS observatory Authors • VERITAS blazar program • New blazar discoveries • Mrk 421 flare • BL Lac flare • Conclusions
TeV AGN population -9 10 ] -1 SMA s Mrk 421 -2 VLBA_core(BP143) [erg cm VLBA(BP143) -10 VLBA(BK150) 10 Metsahovi � Noto F � VLBA_core(MOJAVE) 10 -11 VLBA(MOJAVE) OVRO RATAN Swift/UVOT MAGIC Medicina -12 Effelsberg ROVOR Fermi 10 NewMexicoSkies Swift/BAT MITSuME RXTE/PCA GRT Swift/XRT -13 10 GASP WIRO OAGH -14 10 10 12 14 16 18 20 22 24 26 28 10 10 10 10 10 10 10 10 10 10 � [Hz] Radio IR-optical-UV X-ray Fermi VHE low 20 Γ t var state IBL 15 detecta 4 HBL harder ~3 min HBL ble LBL 33 10 IBL 4 weak 1 day 5 FSRQ not LBL ~15min 3 seen FR I ? 4 0 0.03 0.1 0.3 not FSRQ softer ~10min seen redshift 2
• Situated at 1280m altitude at Whipple Observatory in Arizona • 499 PMTs 12 m 3.5° • 106 m 2 tessellated • 500 MSPS sampling FADCs • Recoated every ~4 years • 3-level trigger 4
VERITAS observatory VERITA VERITAS Location 31°40 ′ N, 110°57 ′ W, 1.3km Array configuration 4 x 12m telescopes Energy range 100 GeV < E ɣ < 30 TeV Energy resolution 15 - 20% Field of view 3.5° Angular resolution < 0.1° Sensitivity 1% Crab in 26hr Duty cycle 10-12% (1000hr\yr) 5
VERITAS AGN program • Multi-year plan to observe 14 northern TeV blazars Name Class z M 87 FR I 0.004 – Mid-distance hard spectrum HBLs Mrk 421 HBL 0.031 Mrk 501 HBL 0.034 – Bright nearby HBLs 1ES 2344+514 HBL 0.044 – All northern IBLs and LBLs 1ES 1959+650 HBL 0.048 BL Lacertae LBL 0.069 W Comae IBL 0.102 RGB J0710+591 HBL 0.125 • Discovery program 1H 1426+428 HBL 0.129 1ES 1215+303 LBL 0.130? – Most of it is ToO based (optical, Fermi-LAT) 1ES 0806+524 HBL 0.138 1ES 0229+200 HBL 0.140 – Extensive program for FSRQs 1ES 1440+122 HBL 0.163 RX J0648.7+1516 HBL 0.179 – Accumulating long exposures on good 1ES 1218+304 HBL 0.182 candidates RBS 0413 HBL 0.190 1ES 0414+009 HBL 0.287 1ES 0502+675 HBL 0.341? PG 1553+114 HBL 0.350 • Multiwavelength campaigns 3C 66A IBL 0.444? PKS 1424+240 IBL ? VER J0521+211 HBL ? 6
VERITAS blazar discoveries Abdo et al. 2010 • All VERITAS discoveries in the TeV band 3C 66A triggered MWL observations and SEDs are published with GeV (Fermi-LAT), X- ray (Swift, RXTE), optical & radio data. • Typically SSC models reproduce the SED of HBLs, while low-frequency-peaked objects seem to prefer SSC + EC. 7
New low-latitude blazars RX J0648.7+1516 1 period = 1 month = 1 dark run VER J0521+211 8 � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �
New low-latitude blazars Aliu et al 2011, arXiv:1110.5949 RX J0648.7+1516 Flux (10 � 14 erg s � 1 cm � 2 Å � 1 ) Flux (10 � 14 erg s � 1 cm � 2 Å � 1 ) 2.5 2.5 G band Ca K Ca H z = 0.179 2.0 2.0 1.5 1.5 1.0 1.0 0.5 0.5 0.0 0.0 VER J0521+211 4000 4000 4200 4200 4400 4400 4600 4600 4800 4800 5000 5000 5200 5200 5400 5400 Wavelength (Å) Wavelength (Å) Flux (10 � 14 erg s � 1 cm � 2 Å � 1 ) Flux (10 � 14 erg s � 1 cm � 2 Å � 1 ) 10 2.5 2.5 40 ] Swift XRT -1 s -2 Mg I Na I 35 ergs cm 2.0 2.0 30 -11 25 1.5 1.5 XRT Flux 2-10 keV [10 20 1.0 1.0 15 10 0.5 0.5 5 0 0.0 0.0 ] -1 VERITAS s 7 -2 5500 5500 6000 6000 6500 6500 7000 7000 m 6 -7 VHE Flux > 200 GeV [10 Wavelength (Å) Wavelength (Å) 5 4 3 2 1 Redshift of 0.179 55120 55130 55140 55150 55160 55170 55180 55190 55200 55210 MJD Aliu et al, in prep. 9 � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �
Mrk 421 • Major flares in 2008 and 2010 ApJ submitted (2010) • Huge flare on Feb 17 2010 – Flux reaches ~10 crab spectral hardening with increasing flux – doubling times ~5-10min – 10 σ /2min bin Aliu et al, in prep. 10
BL Lac flare • Very bright flare observed in June 28 • 20 σ in a 20 min run • Intra-night variability • Coincident with a ‘extreme hardening’ of the GeV spectrum measured by Fermi BL Lacertae Aliu et al, in prep. 11
BL Lac flare halving time ~ 15 min 40 min Aliu et al, in prep. 12
Multiwavelength observations -7 10 ] -1 s -2 • Diagnostic to better understand GeV [erg cm -8 10 spectral features in LBLs and FSRQs: see � F if the spectrum continues beyond 100 � -9 10 GeV -10 • Extensive MW campaign to observe 10 flaring FSRQs (3C 279 and 4C 21.35) Pointed mode ( 10) × -11 10 North survey ( 1.0) from radio to TeV energies. × Standard survey ( 0.1) × -12 • Approved Fermi -LAT pointed 10 2 1 10 10 Energy [GeV] observations simultaneous with X-ray and ground-based observations. 3 × 10 3000 Pointed mode • Coverage at VHE (VERITAS & MAGIC), North survey 2500 Standard survey gamma-ray (Fermi), X-ray & UV (Swift), ] -1 2000 s Optical-IR (SMARTS, MDM, KVA, ...) and -2 Exposure [cm 1500 radio (OVRO). 1000 500 0 0 100 200 300 400 500 600 700 time [minutes] 13
Summary • VERITAS is monitoring a sample of northern TeV blazars 1ES 1218+304 • Continuous observations allow better studies of spectral and flux 1ES 1215+303 variations, sub-hour variability • Multiwavelength program with GeV, X-ray, optical coverage • Discovery efforts continue: new HBLs, extend to LBLs, FSRQs • Good synergy with Fermi: – Trigger for gamma-ray high states W Comae – Good sampling of Compton peak 14
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