Exploring galactic chemical abundance of phosphorus in the ultra-violet with HST

Ultra violet observed spectral data taken by the Hubble Space Telescope (HST) are made available to the public. These data sets have been extracted into one-dimensional and flux-calibrated spectral data, and are ready for analysis. We have normalized the extracted spectra with a Planck black body curve. The spectral range of 2400 to 2700 °A is available for all the stars that are analyzed in this study and includes nine different neutral phosphorus lines for us to analyze. With our Planck normalized spectral data, we have made the first measurements for the Galactic chemical abundance of phosphorus in metal poor stars. The nine stars analyzed in this study possess an overall chemical enrichment ranging between solar to less than 1/1000 solar. Atmospheric temperatures for these stars nicely brackets the temperature of the Sun ranging between 4910K < T.~ 5800K < 6398K. Our analysis involved comparing spectrum synthesis calculations to the Planck normalized spectral data. We are able to derive reliable phosphorus abundances from one line at 2554.911 °A except for one star which we resort to the line at 2433.989 A° . Our results from analyzing the ultra violet region predicts an overall lower chemical enrichment by a factor of ~10 than previous work in the far infrared. Despite this apparent offset from previous studies, our data clearly reveals a decrease in phosphorus abundance with increasing metallicity. Future work necessary to better understand the Galactic chemical abundance of phosphorus is also discussed.