Post-SM4 Sensitivity Calibration of the STIS Echelle Modes

1. Post-SM4 Sensitivity Calibration of the STIS Echelle Modes Azalee Bostroem With help from: Ralph Bohlin, Alessandra Aloisi, Charles Proffitt, Kenneth Hart, Phil Hodge

2. Echelle Modes Increasing Order/ Decreasing Wavelength Grating disperses light vertically Higher orders are chosen and dispersed horizontally Orders have overlapping wavelength ranges Allows for broadband high resolution spectroscopy STIS has 4 modes medium and high resolution modes Increasing Wavelength

3. Convert net count rate to flux • Models the shape of the blaze function of each order • Shape varies continuously with location on the detector and time • Temporal component can experience a discontinuity with instrument changes (e.g. switch from Side 1 to Side 2 electronics • Discontinuity expected following SM4 • Program 11866 executed in Cycle 17 to characterize the echelle blaze function Photometric Conversion Table (PHOTTAB)

4. Status following SM4 Net Counts Pre-SM4 Flux Calibration on Post-SM4 Data (smoothed)

5. Making a new PHOTTAB • Steps: • Divide net counts of each order by a model spectrum • Fit each order with a spline • Smooth splines across orders • Record smoothed nodes for each order of every central wavelength in a table

6. But its never that simple… • First PHOTTAB created using STScI CalSTIS calibrated data • Created grating dependent bad pixel tables • Created new ripple tables • Look for the E140H flux anomaly • Data not in current PHOTTAB not extracted

7. Bad Pixel Tables • NUV Bad Pixel Table: • NUV corners are vignetted • Vignetting is grating dependent • Previously in flat field • Now in bad pixel table • FUV Bad Pixel Table: • Repeller wire across detector • Previously in flat field • Location is grating dependent • Now in bad pixel table

8. Ripple Tables • Echelle 2D scattered light background subtraction • Normalized blaze function • Only delivered once in 2002, no information on the creation • Solve issue in E140H data background subtraction

9. Flux Anomaly • Decreased throughput directly following SM4 in E140H and E230M

10. Flux Anomaly Cont. • Observed again after MAMA shutdown in fall 2010 • Not observed in next monitoring Observation: April 2010 • Echelle Flux calibration program executed November 28, 2009 - January 6, 2010

11. Data not affected • If affected, then flux of new data should be too high

12. Edge Orders • When PHOTTAB was created in 2006, the program was taken at extreme mode select mechanism positions • Monthly offsetting turned off for Echelle data • Some orders are off the detector • CalSTIS will not extract data not in the PHOTTAB unless fluxcorr is set to omit • These orders were evaluated and included on an individual basis

13. PHOTTAB Creation • Find sensitivity for each order: • Sensitivity = Observed Net Count Rate/Model Flux • Exclude bad pixels and strong absorption lines

14. Sensitivity

15. PHOTTAB Creation • Find sensitivity for each order: • Sensitivity = Observed Net Count Rate/Model Flux • Exclude bad pixels and strong absorption lines • Fit a 7 (9 for E230M) node spline to sensitivity for each order

16. Spline

17. PHOTTAB Creation • Find sensitivity for each order: • Sensitivity = Observed Net Count Rate/Model Flux • Exclude bad pixels and strong absorption lines • Fit a 7 (9 for E230M) node spline to sensitivity for each order • Smooth spline nodes for each order in the cross dispersion direction

18. Smooth

19. PHOTTAB Creation • Find sensitivity for each order: • Sensitivity = Observed Net Count Rate/Model Flux • Fit a 7 (9 for E230M) node spline to sensitivity for each order • Smooth spline nodes for each order in the cross dispersion direction • Back out the TDS to reflect sensitivity at Launch • Extrapolate to infinite aperture and extraction box height

20. Final Calibration

21. Changes in CalSTIS 2.38 Phottab: A DUMMY pedigree will still be extracted X1D Table: Add net_err column, set flux, err = 0 for DUMMY pedigree

22. Future Work: Blaze Function Shift Evolution