We present a new iron abundance analysis of the hyper metal-poor star HE 1327 - 2326 , based on Fe ii lines detected in its UV spectral range for the first time .
In a Cosmic Origins Spectrograph ( COS ) spectrum , five new Fe ii lines could be measured .
A Si i line was also detected for the first time .
We determine a 1D Local Thermodynamic Equilibrium ( LTE ) Fe ii abundance of \mbox { [ { Fe { ii } } / H ] } = -5.99 \pm 0.25 .
We also investigate departures from LTE for both Fe i and Fe ii lines .
Guided by 3D Non-LTE ( NLTE ) analyses of other well-studied metal-poor stars , we identify potential “ residual ” 3D effects in HE 1327 - 2326 arising from the absence of full 3D NLTE Fe calculations .
Accordingly , we employ measurements of 10 weak Fe i lines previously detected in an optical spectrum of HE 1327 - 2326 , as no Fe i lines are detectable in our UV spectrum .
Following our previous work , we adopt the 1D NLTE Fe i abundance of \mbox { [ Fe / H ] } = -5.20 \pm 0.12 for HE 1327 - 2326 .
Adopting a value based on the optical Fe i rather than UV lines was heavily informed by our extensive investigation of model atmosphere and radiative transfer effects on different lines across the entire UV-optical wavelength range .
An iron abundance of \mbox { [ Fe / H ] } = -5.20 \pm 0.12 is only 0.2 dex higher than what was used in previous studies .
Accordingly , no previous conclusions regarding the nature of the star are affected .