HI Ly{alpha} (1215.67{AA}) and the OI triplet (1302.17, 1304.86, and 1306.03{AA}) are bright far-ultraviolet (FUV) emission lines that trace the stellar chromosphere. Observations of stellar Ly{alpha} and OI using the Hubble Space Telescope's (HST) most sensitive FUV spectrograph, the Cosmic Origins Spectrograph (COS), are contaminated with geocoronal emission, or airglow. This study demonstrates that airglow emission profiles as observed by COS are sufficiently stable to create airglow templates that can be reliably subtracted from the data, recovering the underlying stellar flux. We developed a graphical user interface to implement the airglow subtraction on a sample of 171 main-sequence F-, G-, K-, and M-type dwarfs from the COS data archive. Correlations between recovered stellar emission and measures of stellar activity were investigated. Several power-law relationships are presented for predicting the stellar Ly{alpha} and OI emission. The apparent brightness of the stellar emission relative to the airglow is a critical factor in the success or failure of an airglow subtraction. We developed a predictor for the success of an airglow subtraction using the signal-to-noise ratio of the nearby chromospheric emission line SiIII (1206.51{AA}). The minimum attenuated Ly{alpha} flux that was successfully recovered is 1.39x10^-14^erg/cm^2^/s, and we recommend this as a minimum flux for COS Ly{alpha} recoveries.

Cone search capability for table J/ApJ/946/98/tableb2 (Observing programs of the stellar COS and literature values)