16907

This program will determine the line spread functions (LSFs) and spectral resolution obtained with the G160M grating at the Cosmic Origins Spectrograph.s (COS) sixth lifetime position. Well-constrained LSFs allow users to evaluate the feasibility and S-N constraints of their observations comma as well perform line profile fitting on their data. COS periodically shifts where its targets. light lands on the detector to avoid gain sag. The sixth of these d_commalifetime positionsd_comma (LPs) will become active for G160M exposures in Cycle 30. COS. LSFs and spectral resolution change with LP and with the grating and central wavelength settings used. This program will make observations to constrain the LSFs of two G160M central wavelength settings (cenwaves) comma G160M-1533 and G160M-1623 comma which encompass the range of cenwaves moving to LP6. We will acquire G160M-1533 and G160M-1623 spectra of the SMC blue supergiant star AV75 comma whose spectrum contains both narrow ISM absorption lines and complex convolved lines. We expect a S-N of 60 per resolution element at 1600 Angstroms. We will then convolve existing STIS E140M spectra of AV75 with various versions of the optically-modelled COS LP6 LSFs comma and determine which convolutions best agree with the COS spectra gathered here. These will be selected as the COS LP6 LSFs and used to determine the spectral resolution.