STORM

The Space Telescope and Optical Reverberation Mapping (STORM) Campaign used HST/COS, Swift, Chandra and ground-based facilities in a six-month long reverberation mapping experiment during 2014 to observe the active galactic nucleus (AGN) in the Seyfert 1 galaxy NGC 5548. The goal of the campaign was to resolve the structure of the broad-line region (BLR) and the continuum emission region in this AGN. This site provides calibrated spectra and models for NGC 5548 from the HST/COS observations obtained for the STORM campaign.  HST observations were made in single-orbit COS visits approximately daily from 2014 February 1 through July 27. Of the 179 scheduled visits, 171 observations were executed successfully. In each visit, the team used the G130M and G160M gratings to observe the UV spectrum over the range 1153—1796 Angstroms in four separate exposures. Exposure times were selected to provide S/N > 100 when measured over velocity bins of ~500 km/s. During each visit, the team obtained two 200-second exposures with G130M centered at 1291 Angstroms and 1327 Angstroms, and two 590-second exposures with G160M centered at 1600 Angstroms and 1623 Angstroms. As described by De Rosa et al. (2015) the team customized the calibrations of these spectra to improve the wavelength calibration, the S/N with better flat fields, and more accurate and repeatable flux calibrations. These reprocessed spectra obtained with the various central wavelength and FPPOS settings were then combined into single spectra for G130M and G160M for each individual observation.

The team has also modeled these UV spectra of NGC 5548 to correct for intervening absorption and to deblend the individual emission lines. These spectral models, described by Kriss et al. (2019), are based on merged G130M and G160M spectra for each observation that have been binned by 4 pixels (half a resolution element). Using the modeled spectra, the team produce spectra where absorption intrinsic to NGC 5548 and in the intervening interstellar medium of the Milky Way has been replaced by their emission model to remove the absorption features.  The models themselves consist of 91 components.  Finally, modeled continuum fluxes, deblended emission line fluxes, and the strengths of absorption lines intrinsic to NGC 5548, as tabulated by Kriss et al. (2019) are collected here as well.

Download All Visit Spectra: hlsp_storm_hst_cos_ngc-5548_g130m-g160m_v1_all-visit-spec.tar.gz