16467

Knowledge of the COS Line Spread Function (LSF) is critical for users who wish to perform detailed line fitting studies as well as estimate signal-to-noise requirements. The exact shape of the LSF comma and therefore the achievable overall spectral resolution comma is a function of the overall optical path to a given lifetime position (LP). Here we determine the LSF and spectral resolution at LP5 for settings G130M-1291 and G130M-1327 comma which encompass the range of cenwaves moving to LP5. We observe the SMC blue super giant AV 75 comma whose spectra has both narrow interstellar absorption lines and complex broader convolved lines. We will test whether previous STIS E140M spectra of AV 75 convolved with model LP5 COS LSFs can reproduce the observed COS FUV spectra of numerous lines comma thus validating the model spectra LSFs. We expect achieving a SN of about 60 for cenwave 1327 but possibly lower for 1291 comma where the COS2025 policy prevents use of all four FP-POS comma thus preventing mitigation of fixed pattern noise. We also take one exposure with cenwave G140L-800 at LP3 to 1) check the LP4 wavelength calibration accuracy at this mode and 2) use for a new derivation of the wavelength solution if needed. The 1291-FUVB data will also be used for the wavelength calibration derivation at LP5.