Reeves, J. N.J. N.ReevesBRAITO, ValentinaValentinaBRAITONARDINI, EMANUELEEMANUELENARDINIBehar, E.E.BeharO'Brien, P. T.P. T.O'BrienTombesi, FrancescoFrancescoTombesiTurner, T. J.T. J.TurnerCosta, M. T.M. T.Costa2020-05-262020-05-2620160004-637Xhttp://hdl.handle.net/20.500.12386/25168High-resolution soft X-ray spectroscopy of the prototype accretion disk wind quasar, PDS 456, is presented. Here, the XMM-Newton reflection grating spectrometer spectra are analyzed from the large 2013-2014 XMM-Newton campaign, consisting of five observations of approximately 100 ks in length. During the last observation (OBS. E), the quasar is at a minimum flux level, and broad absorption line (BAL) profiles are revealed in the soft X-ray band, with typical velocity widths of {σ }<SUB>{{v</SUB>}}̃ {{10,000}} km s<SUP>-1</SUP>. During a period of higher flux in the third and fourth observations (OBS. C and D, respectively), a very broad absorption trough is also present above 1 keV. From fitting the absorption lines with models of photoionized absorption spectra, the inferred outflow velocities lie in the range ̃ 0.1{--}0.2c. The absorption lines likely originate from He and H-like neon and L-shell iron at these energies. A comparison with earlier archival data of PDS 456 also reveals a similar absorption structure near 1 keV in a 40 ks observation in 2001, and generally the absorption lines appear most apparent when the spectrum is more absorbed overall. The presence of the soft X-ray BALs is also independently confirmed by an analysis of the XMM-Newton EPIC spectra below 2 keV. We suggest that the soft X-ray absorption profiles could be associated with a lower ionization and possibly clumpy phase of the accretion disk wind, where the latter is known to be present in this quasar from its well-studied iron K absorption profile and where the wind velocity reaches a typical value of 0.3c....ELETTRONICOenArticle10.3847/0004-637X/824/1/202-s2.0-84976412166000377937300020https://iopscience.iop.org/article/10.3847/0004-637X/824/1/20https://iopscience.iop.org/article/10.3847/0004-637X/824/1/20/pdfFIS/05 - ASTRONOMIA E ASTROFISICA