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Beyond the Limb

A Narrow Band EUV search for Background Objects with the AIA. Beyond the Limb. Sam Schonfeld. Advisors: Paola Testa and Steve Saar. Contents. Motivation Cross calibrating solar measurements Methods: Finding Targets Tracking targets Modeling stellar emission Estimating Signal

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Beyond the Limb

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  1. A Narrow Band EUV search for Background Objects with the AIA Beyond the Limb Sam Schonfeld Advisors: Paola Testa and Steve Saar

  2. Contents • Motivation • Cross calibrating solar measurements • Methods: Finding Targets • Tracking targets • Modeling stellar emission • Estimating Signal • Methods: Preparing Observations • Off-Limb Intensity Decay • Satellite Path Correction • Conclusions AIA 171Å AIA 193Å

  3. Motivation: Comparing Sun and Stars • Sun is a Star at 1 AU • Spatial resolution • Test stellar models • This proximity is also a problem • Difficult to measure the Sun and anything else with the same instrument • Different telescopes use different techniques • Possible discrepancies between instruments

  4. Motivation: The AIA • Constant full sun imaging from SDO • Narrow band EUV telescopes • High resolution and cadence • Chance to observe Sun and stars together • Objectives: • Primary: Determine whether possible to observe background objects • Secondary: If possible, make observations

  5. Methods: Can AIA Detect Stars? • Pros • Star is point a source • Sun is relatively dim • AIA is sensitive • Dynamic range ≈ 104 DN • Object must be ≈103more Luminous than Sun! • Cons • Star is > 107 farther • Flux=L / (4πD2) • Extinction due to ISM

  6. Methods: Candidate Objects Selected from ROSAT x-ray observations

  7. Methods: Path Elimination 1 pixel ≈ 0.6 arc seconds

  8. Methods: Remaining Objects • 4 Stars, 3 Galaxies, 2 Galaxy Clusters, 2 Unknown

  9. Methods: Stellar EM Models PZ Tel • Emission Measure • Differential Emission Measure • Amount of emitting material • P(T)=emissivity • Use models of similar stars • Scale with distance and luminosity • AIA Temperature response functions • Based on atomic models Argiroffi et al. 2004 94 131 171 193 211 335

  10. Methods: Predicted Count Rates AIA exposure ≈ 2.9 sec

  11. Methods: Observational Techniques • Track Single pixel across field for hours • Integrate signal • Acts like a longer exposure • Takes advantage of point source • Subtract out background • Off-limb coronal emissions AIA 171Å

  12. Methods: Off-limb Coronal Emission AIA 171Å

  13. Methods: Exponential Decay 171 Å Consistent with exponential decay of coronal density 94 Å Suggests AIA noise ≈3 DN

  14. Methods: Image Offset Problem SDO is in Orbit! Earth Geostationary Geosynchronous Corrected Earth Geostationary Geosynchronous Corrected April 2011 June 2010 Dr. Bart De Pontieu

  15. Conclusion • Observation appears possible but… • Stellar sources produce count rates within the noise level • Future Work: to make observations • Finish orbit corrections • Longer exposures would allow observations • Off pointing from disk would increase number of targets • Include non-stellar targets

  16. Supplemental • HD 199143 • PMS AeFe • HD 206301 • Variable RS CVn type • HD 210803 • PMS • HD 245924 • T-Tau type

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