Recent Observations of Supernova Remnants with VERITAS Amanda Weinstein (Iowa State University) For the VERITAS Collaboration

Overview 2 recently-discovered TeV sources that are GeV-TeV SNR Tycho Very young (historical) SNR Remnant not resolved in gamma rays. Models strongly favor hadron-dominated emission. Possible molecular cloud interaction G /Gamma Cygni (VER J ) Remnant easily resolved in gamma rays. Does not fit into molecular cloud paradigm. Possible interaction with wall of wind-blown cavity SNR association, hadronic-emission-dominated model currently favored 8/15/2011ICRC 2011, Beijing, China2

Tycho’s SNR Remnant of Type 1a Supernova event of 1572 X-ray morphology suggests efficient hadron acceleration (Warren et al. 05) VERITAS: 5σ post- trials detection in 68 hours Molecular cloud (FCRAO 12CO ) (Heyer et al. 1998) Acciari et al Chandra X-ray contours (Hwang et al. 2002) 8/15/2011ICRC 2011, Beijing, China3

Tycho: Model Constraints dN/dE = C(E/3.42 TeV) -Γ Γ = 1.95 ± 0.51 stat ± 0.30 sys C = (1.55 ± 0.43 stat ± 0.47 sys) x cm -2 s -1 TeV -1 Integral flux ~0.9% of Crab Nebula flux above 1 TeV Fits assume no influence from molecular cloud to north. Hadronic-dominated model favored. lowest allowed B field: ~80 μG Enhanced B signature of accelerated cosmic rays IC π 8/15/2011ICRC 2011, Beijing, China4

Model Constraints with Fermi Sub-GeV to TeV spectrum consistent with single power law (Giordano et al., 2011, Morlino and Caprioli 2011). Leptonic-dominated scenario strongly disfavored. No cutoff in TeV → acc time = SNR age → max proton energy Giordano et al “far” case CaseE p,max (TeV) Dist- ance (kpc) E SNR (erg) “near” “far” x /15/2011ICRC 2011, Beijing, China5

G (Gamma Cygni) Middle-aged SNR: ~7kyr Distance: ~1.7 kpc (Higgs et al. 1977, Lozinskaya et al. 2000) H I shell surrounds remnant (Gosachinskij 2001). Enhanced thermal X-rays and “void” of CO emission in NW (Ladouceur and Pineault 2008). Contains GeV pulsar (LAT PSR J ). Covered by VERITAS as part of Cygnus Region Survey; detected after follow-up observations. CGPS 1420 MHz radio continuum 8/15/2011ICRC 2011, Beijing, China6

VER J FGL J % CL ellipse 2FGL position tagged as unstable (TS map peak outside 68% location contour). Fitted VER J extension 0.18°±0.03° stat ° sys -0.01° sys >7.5σ post-trials detection in ~20 hours CGPS 1420 MHz radio continuum PSF LAT PSR J Aliu et al. in prep. 8/15/2011ICRC 2011, Beijing, China7

VER J2019 in X-Rays Image and spectrum extracted from ASCA data Diffuse thermal emission correlated with GeV-TeV No clear evidence for non-thermal component Aliu et al. in prep. Acciari et al. in prep keV 8/15/2011ICRC 2011, Beijing, China8

VER J : Interpretations Acceleration in SNR shock: Optical emission lines, thermal X-rays suggest shock-heating Emission likely hadronic (lack of correlation with non-thermal X- rays) Not a molecular cloud interaction (differs from IC443, W28, etc.) Could be hadronic emission in a wind-bubble scenario Inferred pre-shock density from optical: 1-10 cm -3 Estimated HI shell density (Gosachinskij 2001) : 2.5 cm -3 Required density inferred from TeV: 2-15 cm -3 Offset PWN? implausible if associated with LAT PSR J ° offset between pulsar and core emission (15 pc distance) No overlap between GeV-TeV emission and pulsar position 8/15/2011ICRC 2011, Beijing, China9

BACKUP 8/15/2011ICRC 2011, Beijing, China10

Model Constraints with Fermi Sub-GeV to TeV spectrum consistent with single power law Strong claims now being made that the lepton –dominated scenario is ruled out (Morlino and Caprioli 2011) Morlino and Caprioli 2011 Half-Pevatron? (Morlino and Caprioli model has accelerated protons up to 470 TeV) 8/15/2011ICRC 2011, Beijing, China11