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SPASE point source search - PowerPoint PPT Presentation

iliana-schmidt
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SPASE point source search

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  1. SPASE point source search Look for ~100 TeV gamma-rays from 3 specific HESS sources high in the southern sky

  2. Three HESS sources • Shell-type SNR RX J0852.0-4622 (q=43.8o) • differential G = 2.1 ± 0.1; Eg,max > 10 TeV • F(>TeV) = 1.9 x 10-11 cm-2s-1 (astro-ph/0505380) • Pulsar wind nebula MSH 15-52 (q=38o) • G = 2.27 ± 0.20; Eg,max > 30 TeV • F(>TeV) = 4.5 x 10-12 cm-2s-1 (astro-ph/0504120) • Unidentified HESS J1303-631 (q=26.9o) • G = 2.44 ± 0.2; Eg,max > 10 TeV • F(>TeV) = 3.0 x 10-12 cm-2s-1 (A&A 439, 2005, 1013)

  3. Sensitivity of SPASE • S30 (fitted density at 30 m from fitted core) is proxy for Energy. For protons • E ~ 50 TeV (S30)0.9 (E ~ 100 TeV at S30 ~2.2) • Median S30 ~ 2.5 corresponds to E ~ 115 TeV for near vertical events • Angular resolution • ~3o for S30 < 2 • ~2o for S30 > 2, plus response more stable, but energy threshold higher

  4. Sensitivity of SPASE (cont.) • Angular response: • dN / dcos(q) ~ exp[ - 7 x (sec(q) – 1)] • due to attenuation at greater slant depth • implies relation for attenuation of S30 • dN / d S30 ~ exp[ - ( X(q) – X(0)) / 160 g/cm2 ) • Energy response: • Threshold energy increases with angle • SPASE-1 search  Eth ~ 50, 100, 200 TeV • for q = 26.9o, 38o, 43.8o, respectively • (see J. van Stekelenborg et al., PRD48(1993) 4504 )

  5. Sensitivity of SPASE (cont.) • Exposure: ~104 m2 x 3 live yrs ~1016 cm2s • Multiply by cos(q) (projected area) • Background: 2 x 108, from all directions • Look at 3o x 3o, all events; 2o x 2o, S30 > 2 • Background/bin: 3 x 105, 1.6 x 105, 8 x 104for q = 26.9o, 38o, 43.8o, respectively, for all evnts • Background/bin: 7 x104, 3.4 x 104, 1.8 x 104for q = 26.9o, 38o, 43.8o, respectively, for S30 > 2

  6. Expected signal all events, 3o x 3o search bin, assuming no cutoff • SNR RX J0852.0-4622 (q=43.8o) • F(>200 TeV) ~ 6 x 10-14 cm-2 s-1 • 400 signal / 8 x104 background (1.5 s) • PWN MSH 15-52 (q=38o) • F(>100 TeV) ~ 1.3 x 10-14 cm-2s-1 • 100 signal / 1.6 x105 background (0.25 s) • Un-ID J1303-631 (q=26.9o) • F(>50 TeV) ~ 1.1 x 10-14 cm-2s-1 • 100 signal / 3 x105 background (0.2 s)

  7. Expected signal all events, 2o x 2o search bin, assuming no cutoff • SNR RX J0852.0-4622 (q=43.8o) • F(>400 TeV) ~ 2.8 x 10-14 cm-2 s-1 • 200 signal / 1.8 x104 background (1.5 s) • PWN MSH 15-52 (q=38o) • F(>200 TeV) ~ 5 x 10-15 cm-2s-1 • 45 signal / 3.4 x104 background (0.25 s) • Un-ID J1303-631 (q=26.9o) • F(>100 TeV) ~ 4 x 10-15 cm-2s-1 • 36 signal / 1.8 x104 background (0.25 s)