SED of a Circumstellar Disk

Objective

Description

Acquire normal SED AOT observations of an available, moderately bright circumstellar disk with < 2' spatial extent. Use at least 3 cycles regardless of whether that is needed to get the desired S/N in order to verify correct behavior of the observatory and pipeline for multiple cycles, and examine S/N as a function of integration time to verify the predicted sensitivity.

The source chosen is the F9V star HD 10647, an IRAS source with excess emission at 25 and 60 microns. This source was in the VLS GTO program, but Chas/Beth agreed to let us do it for IOC, as the IOC observation actually gave better S/N than the one they had planned. The 25 and 60 micron fluxes are roughly 250mJy and 630mJy, respectively.

The Photometry companion to this task is mips-275, which uses the same target. The flux calibration of SED mode observations is a meta-task (2030).

This observation is an Early Characterization Observation.

The existing data for this source are summarized in the following figure, which compares photometric measurements to a Kurucz model fit to those data (from Beth Holmes)

Data Collected

3 cycles of the SED AOT using 10 second DCEs.

Data Reformatting Requirements

Array Data Desired:

70µm Array.

Data Reformatting Option:

• SPECIAL, or maybe NORMAL (for use w/ the DAT) and
• NONE (for use w/ pipeline).

Special Instructions:
The enhancer will nominally produce fully coadded on-source and off-source images from an AOR. Until we are confident that the rectification of the images is good enough to allow coaddition of data from two different along-slit positions, it probably makes sense to separately coadd just the A-beam data to produce an object-sky pair of images, and the B-beam data to produce a second pair of object and sky images. This can be accomplished by running dat-pack such that the first 1/2 of the data is put into one file (for A-beam images), and the second 1/2 is put into a separate B-beam images. If early results from the wavelength cal tasks indicates this conservative approach isn't necessary, special packing is not required, and just one pair of images will result.

Task Dependencies

• MIPS-145: SED Wavelength Calibration - set wavelngth scale for comparing the SED spectrum to photometry.
• MIPS-299: SED Illumination Correction - need product to remove stim illumination pattern from the calibrated data
• MIPS-300: SED AOT Validation - do sources go down the slit? 300 probably should be a critical task, but wasn't on the list...
• MIPS-2030: SED IC and Flux Cal - need conversion from DN/s to flux units and to understand any wavelength dependencies in the IC.

Calibration Dependencies

• 70 µm Dark, SED-mode Illumination Correction, and Flux Calibration.

Output and Deliverable Products

• Coadded, dark-subtracted, flat-fielded, calibrated spectral image created using both the DAT and the SSC Pipeline.
• Extracted spectrum of the source overplotted with IRAS data, fitted photosphere model, and photometry from task mips-275, photometry observation of this same source.

Data Analysis

• The reformatted data will be run through mips_sloper and mips_caler using the default settings. SED ICs from at least 2 pointings will be used in mips_sloper to see if they give the same output spectra. Frames will be coadded using the enhancer to verify correct automatic operation w/ the SED AOT data stream, and also coadded 'by hand' using IDP3 as a check.
• The BCD products from the SSC pipeline will be coadded using both the enhancer and the ssc mosaicing tool to produce final coadded, calibrated images. We will use the off-line pipeline so that we can use the identical ICs as were used in the DAT.
• Final coadded images from the DAT and SSC Pipeline will be compared by ratioing and/or differencing to verify overall agreement in the data products.
• IDP3 and/or the MIPS SED extraction tool (mips_seder?) will be used to extract signal vs. pixel position (using the draw-aperture capability) from the final coadded calibrated images from both the DAT and pipeline. The signal in sky apertures to either side of the source will be similarly extracted, and subtracted from the on-source signal (assuming that the source is not significantly extended, see below). The resulting 1-D spectrum will be converted to a wavelength scale using the calibration derived from mips-145.
• A plot will be created showing the stellar photospheric emission, all IRAS data, and both the SSC and DAT versions of SIRTF SED data.
• If the source is extended it will be necessary to subtract the off-source data produced by the SED AOT from the on-source frames. This should be done after all DCEs have been run through the full pipeline or DAT to produce BCDs. It might be worth checking the result of subtracting the off-source images from the on-source ones even if the source is not extended, just as a verification that there are no significant differences from using the on-array sky apertures.

Software Requirements

• DAT - mips_sloper, mips_caler; no special flags needed.
• BCD pipeline processing.
• IDL - IDP3 for rectifying and coadding images and extracting 1-D spectrum.
• SSC mosaicing tool for coadding.
• DAT - enhancer for coadding, rectifying
• DAT - 'mips_seder' for extracting the spectrum, if available.

Actions Following Analysis

• Disagreement between imaging and/or photometry results from the two pipelines.
  • Check data products at relevant intermediate stages.
• Disagreement with IRAS or SIRTF photometry fluxes.
  • Contact calibration working group with the issue.

Additional Notes