PRE-COSTAR FOS APERTURE TRANSMISSIONS FOR POINT SOURCES (update of CAL/FOS-106) R. C. Bohlin FOS Instrument Science Report CAL/FOS-120 94 February ABSTRACT The FOS absolute sensitivities are determined by observations of standard stars in the 4.3" acquisition aperture. For estimates of absolute fluxes of point sources that are observed in smaller apertures, the apparent, measured transmission of the smaller aperture relative to the 4.3" aperture is required. In addition to the proposals 3106 and 4211 that were analyzed for the earlier CAL/FOS-106 (Bohlin 1993), more recent data from propids 5046 and 5048 confirm the throughputs for the B3(1") and C2(slit) single apertures. Along with an early propid 2823, the 5046 and 5048 data also determine aperture corrections for some of the square aperture pairs C1(1"), A2(.5"), and A3(.25"). 1. OBSERVATIONS The same methodology is used as in CAL/FOS-106 (Bohlin 1993); and all of the analysis presented there remains valid. The newly analyzed data and the average aperture corrections that change slightly are discussed here. In order to compute the relative aperture throughput, the countrate spectrum in the smaller apertures is divided by the countrate spectrum of the same star in the A1(4.3") aperture. All of the mean measured aperture corrections in Table 1 are derived from countrates that are corrected to the optimal (zero) OTA focus as described in CAL/FOS-106. The 53 new values along with the 75 earlier values provide the updated Table 1. The 53 new measures include 6 more through B3(1") to supplement the original 21, 13 more through the C2(slit) to supplement the original 18, and 34 for paired apertures. 2. DISCUSSION AND RECOMMENDATIONS The recommended average aperture corrections are summarized in Table 2. The largest change in the averages from CAL/FOS-106 for the single apertures is a drop in the recommended average for the C2(slit) on the red side prism from 0.39 to 0.38. Changes in the quadratic fits for the single aperture corrections in Table 3 are less than 2-3%. Some of the uncertainties in Table 2 are less than quoted in CAL/FOS-106, because the new B3(1") and C2(slit) data demonstrate good repeatability. For high dispersion, the small scatter in Table 1 suggests that an average of each column might lower the uncertainties further. An exception is H78, which is slightly low in all four cases. An alternative suggested by the new data for the C1(1") paired apertures is a smoothly dropping transmission with wavelength. The amount of this potential systematic effect is comparable to the uncertainty. In order to fully appreciate this uncertainty, a spectrum of interest could be reduced using the value for the particular grating in Table 1 and compared with the flux from the recommended average correction in Table 2. In the low dispersion modes, only a few of the non-supported paired aperture tranmissions have been measured. The unmeasured throughputs could be guessed to a fair accuracy from the symmetries in Table 2. The new data for the square paired apertures shows no significant differences between the upper and lower aperture of the pair in either the average level or the slope, so Tables 2 and 3 contain the average of the upper and lower aperture corrections, while Figure 1 shows the data for each of the new paired aperture measurements separately. The measured red H27 C-1L(1") transmission is ~7% lower than the C-1U correction but is probably low because of jitter or some other pointing problem. The new single aperture data are mostly redundant to the CAL/FOS-106 results and are NOT shown in Figure 1. In Figure 1, the individual quadratic fits to the data are solid lines, and these coefficients are written on the plots. The dashed lines are the final adopted average aperture corrections from Table 3, where these fits are normalized to the average corrections of Table 2. 3. FUTURE CALIBRATION CHANGES The new aperture corrections will be implemented in the PODPS pipeline along with the full scheme to handle the FOS changes in sensitivity with time that is in preparation by Lindler & Bohlin. Any reprocessing of old pre-COSTAR archival data will then have the best estimates for absolute fluxes. REFERENCE Bohlin, R. C. 1993, FOS Instrument Science Report CAL/FOS-106. TABLE 3 SUMMARY OF AVERAGE FOS APERTURE COEFICIENTS DETEC FGWA APER C0 C1 C2 WMIN WMAX NAV BLUE H13 B-1 7.40123e-01 -3.69668e-04 9.36560e-08 1151.00 1609.00 1 BLUE H13 B-2 2.43460e-01 3.89984e-05 -1.41963e-08 1151.00 1609.00 1 BLUE H13 B-3 4.40583e-01 3.33357e-04 -1.66872e-07 1151.00 1610.00 2 BLUE H13 C-1 8.21033e-01 -2.06966e-04 2.83924e-08 1151.00 1610.00 2 BLUE H13 C-2 2.52585e-01 2.36710e-04 -9.84914e-08 1151.00 1610.00 2 BLUE H19 B-1 8.82408e-02 3.21723e-04 -7.93770e-08 1567.00 2335.00 2 BLUE H19 B-2 1.83798e-02 2.45943e-04 -5.92163e-08 1567.00 2335.00 2 BLUE H19 B-3 2.03007e-01 4.18252e-04 -1.13894e-07 1567.00 2336.00 4 BLUE H19 C-1 3.88068e-01 2.59574e-04 -7.89838e-08 1567.00 2336.00 2 BLUE H19 C-2 4.91935e-02 3.46746e-04 -8.70985e-08 1567.00 2336.00 4 BLUE H27 B-1 3.05223e-01 8.90864e-05 -1.82856e-08 2213.00 3308.00 1 BLUE H27 B-2 1.97932e-01 5.99049e-05 -1.20871e-08 2214.00 3308.00 1 BLUE H27 B-3 6.38760e-01 -2.25195e-06 -6.79883e-09 2213.00 3308.00 2 BLUE H27 C-1 5.55440e-01 7.17201e-05 -2.11646e-08 2213.00 3308.00 2 BLUE H27 C-2 4.08958e-01 7.34132e-06 -5.07745e-09 2213.00 3308.00 3 BLUE H40 B-1 3.27705e-01 5.71995e-05 -9.00812e-09 3229.00 4830.00 1 BLUE H40 B-2 2.41780e-01 2.16797e-05 -3.59468e-09 3229.00 4830.00 1 BLUE H40 B-3 7.12372e-01 -4.36912e-05 2.65989e-09 3229.00 4830.00 1 BLUE H40 C-1 5.94378e-01 1.76763e-05 -4.59332e-09 3229.00 4831.00 2 BLUE H40 C-2 2.98353e-01 5.96429e-05 -9.03819e-09 3229.00 4831.00 2 BLUE L15 B-1 4.32666e-01 1.45117e-05 2.19650e-10 1151.00 2523.00 2 BLUE L15 B-2 1.49524e-01 1.51922e-04 -3.35666e-08 1151.00 2523.00 2 BLUE L15 B-3 6.58452e-01 -1.06383e-06 -4.70729e-09 1151.00 2526.00 3 BLUE L15 C-1 5.50613e-01 1.12978e-04 -3.20777e-08 1151.00 2526.00 2 BLUE L15 C-2 3.01223e-01 1.21510e-04 -2.81524e-08 1151.00 2526.00 4 BLUE PRI B-1 3.22353e-01 3.44178e-05 -5.03978e-09 1498.00 4995.00 1 BLUE PRI B-1 -1.21560e+00 8.38476e-04 -1.04393e-07 4993.00 5961.00 1 BLUE PRI B-2 2.15567e-01 3.03832e-05 -3.96765e-09 1498.00 4995.00 1 BLUE PRI B-2 -4.04202e-01 4.26773e-04 -5.85007e-08 4993.00 5961.00 1 BLUE PRI B-3 5.07045e-01 1.48724e-05 -2.71238e-09 1498.00 4995.00 2 BLUE PRI B-3 -3.07691e-01 6.50918e-04 -9.74300e-08 4993.00 5961.00 2 BLUE PRI C-2 3.25306e-01 3.39170e-05 -5.42515e-09 1498.00 4995.00 3 BLUE PRI C-2 1.54610e+00 -1.98827e-04 -7.78873e-09 4993.00 5961.00 3 AMBER H19 A-2 2.56369e-01 1.52290e-04 -2.29875e-08 1588.00 2317.00 2 AMBER H19 A-3 5.69644e-02 1.98838e-04 -3.76404e-08 1588.00 2317.00 2 AMBER H19 B-1 9.71168e-02 3.27939e-04 -7.71301e-08 1588.00 2316.00 2 AMBER H19 B-2 7.38173e-03 2.89346e-04 -6.80307e-08 1588.00 2317.00 1 AMBER H19 B-3 3.05056e-01 2.93554e-04 -7.37150e-08 1588.00 2318.00 3 AMBER H19 C-1 6.87139e-01 -8.78466e-05 2.96762e-08 1588.00 2317.00 2 AMBER H19 C-2 6.14032e-02 3.43563e-04 -8.35636e-08 1588.00 2318.00 3 AMBER H27 A-2 3.54858e-01 8.10490e-05 -1.47280e-08 2216.00 3283.00 2 AMBER H27 A-3 3.06067e-01 7.30640e-06 -3.41775e-09 2215.00 3283.00 2 AMBER H27 B-1 2.89623e-01 1.24265e-04 -2.49962e-08 2217.00 3284.00 1 AMBER H27 B-2 1.55147e-01 1.29845e-04 -2.64168e-08 2217.00 3283.00 1 AMBER H27 B-3 4.63997e-01 1.24362e-04 -2.76913e-08 2217.00 3284.00 1 AMBER H27 C-1 1.13753e+00 -3.66820e-04 6.54760e-08 2215.00 3282.00 2 AMBER H27 C-2 2.76376e-01 1.09996e-04 -2.20588e-08 2217.00 3284.00 1 AMBER H40 A-2 4.25215e-01 2.89289e-05 -4.68249e-09 3229.00 4788.00 2 AMBER H40 A-3 4.28241e-01 -6.30335e-05 7.64942e-09 3229.00 4790.00 2 AMBER H40 B-1 3.68828e-01 5.34220e-05 -8.78792e-09 3226.00 4791.00 1 AMBER H40 B-2 3.35431e-01 -6.26521e-06 -1.91675e-11 3226.00 4791.00 1 AMBER H40 B-3 4.41792e-01 8.93434e-05 -1.26584e-08 3229.00 4790.00 1 AMBER H40 C-1 6.46468e-01 -2.70540e-06 -3.45380e-10 3229.00 4788.00 2 AMBER H40 C-2 3.31970e-01 4.88348e-05 -7.23698e-09 3226.00 4788.00 1 AMBER H57 A-2 4.05738e-01 1.63947e-05 -1.03815e-09 4561.00 6831.00 2 AMBER H57 A-3 1.64198e-01 5.51862e-05 -5.43266e-09 4561.00 6829.00 2 AMBER H57 B-1 9.42854e-02 1.18346e-04 -9.99186e-09 4559.00 6829.00 1 AMBER H57 B-2 7.82160e-03 1.17688e-04 -1.12031e-08 4559.00 6829.00 1 AMBER H57 B-3 3.82182e-01 7.18638e-05 -6.01001e-09 4561.00 6831.00 1 AMBER H57 C-1 6.37723e-01 -6.30680e-06 8.58182e-10 4561.00 6829.00 2 AMBER H57 C-2 2.98603e-01 4.89152e-05 -5.08857e-09 4561.00 6829.00 1 AMBER H78 B-1 6.35974e-01 -5.54944e-05 3.89157e-09 6260.00 8501.00 1 AMBER H78 B-2 5.66594e-01 -5.13968e-05 2.23867e-09 6263.00 8501.00 1 AMBER H78 B-3 6.07382e-01 6.96702e-06 -1.17948e-09 6260.00 8501.00 1 AMBER H78 C-2 5.68258e-01 -3.24092e-05 1.47605e-09 6263.00 8501.00 1 AMBER L15 B-1 4.61080e-01 6.36551e-05 -2.16757e-08 1619.00 2444.00 2 AMBER L15 B-1 -1.16501e+02 1.38912e-01 -4.11667e-05 1568.00 1622.00 2 AMBER L15 B-2 2.80945e-01 9.48045e-05 -2.96085e-08 1619.00 2441.00 1 AMBER L15 B-2 -1.86656e+02 2.29110e-01 -7.01678e-05 1568.00 1622.00 1 AMBER L15 B-3 8.16973e-01 -9.71303e-05 9.52600e-09 1619.00 2444.00 3 AMBER L15 B-3 -4.57722e+02 5.64036e-01 -1.73500e-04 1568.00 1622.00 3 AMBER L15 C-2 4.47359e-01 3.01858e-05 -1.52994e-08 1619.00 2444.00 3 AMBER L15 C-2 -2.32669e+02 2.84751e-01 -8.69442e-05 1568.00 1622.00 3 AMBER L65 B-1 3.42255e-01 6.08407e-05 -5.67747e-09 3752.00 7077.00 1 AMBER L65 B-1 -8.79137e+01 4.65463e-02 -6.12597e-06 3538.00 3755.00 1 AMBER L65 B-2 2.08488e-01 5.94196e-05 -5.96003e-09 3752.00 7077.00 1 AMBER L65 B-2 -8.24104e+01 4.42530e-02 -5.91574e-06 3538.00 3755.00 1 AMBER L65 B-3 4.72254e-01 7.66937e-05 -7.52411e-09 3752.00 7077.00 1 AMBER L65 B-3 -1.13785e+02 6.01869e-02 -7.91221e-06 3538.00 3755.00 1 AMBER L65 C-2 3.16847e-01 5.62395e-05 -5.83242e-09 3752.00 7077.00 1 AMBER L65 C-2 -8.21750e+01 4.38217e-02 -5.81062e-06 3538.00 3755.00 1 AMBER PRI B-1 3.77070e-01 6.32113e-06 -3.38474e-10 1618.00 7480.00 1 AMBER PRI B-1 -1.52755e+00 6.96870e-04 -5.86245e-08 7478.00 8890.00 1 AMBER PRI B-2 2.31237e-01 4.06172e-05 -4.24250e-09 1618.00 7480.00 1 AMBER PRI B-2 -7.26827e+00 2.04362e-03 -1.37986e-07 7478.00 8890.00 1 AMBER PRI B-3 5.45792e-01 -1.21257e-05 2.67205e-09 1618.00 7480.00 2 AMBER PRI B-3 -4.57158e+00 1.53915e-03 -1.13263e-07 7478.00 8890.00 2 AMBER PRI C-2 3.75982e-01 1.69350e-06 -1.08250e-11 1618.00 7480.00 2 AMBER PRI C-2 -1.71501e+00 7.14721e-04 -5.79700e-08 7478.00 8890.00 2 A(ap)=C0+C1*W+C2*W**2, where W is the wavelength in Angstroms. FIG. 1 - The individual quadratic fits to the data are solid lines, and these coefficients are written on the plots. The dashed lines are the final adopted average aperture corrections from Table 3, where these fits are normalized to the average corrections of Table 2. The small aperture A3(.25") ratios show less fixed pattern than the C1(1") or A2(.5") measurements, which suggests that the flat field blemishes are typically larger than 0.25" on the red side.