HST/FOS Observations of the Bright BALQSO PG 0946+301

UV spectra of the bright, relatively low redshift (z_em=1.223) BALQSO PG 0946+301 have been obtained with the FOS on HST. Observations made with FOS gratings G160L, G190H, and G270H provide wavelength coverage from 1200 Angstroms to 3270 Angstroms (540 Angstroms to 1470 Angstroms in the QSO rest frame). Optical spectra obtained using the Lick 3m telescope and CCD spectrograph extend spectral coverage to 9000 Angstroms . The UV spectrum of PG 0946+301 shows deep absorption troughs from a large number of ion species. The strongest troughs are CIV lambda 1549, NV lambda 1240, and OVI lambda 1034, and a blend which includes OIV lambda lambda 790.2,787.7, SV lambda 786.5 and possibly ArVI lambda lambda 767.1, 754.9, NeVIII lambda lambda 770.4, 780.3 and NIV lambda 765.1. Weaker absorption features can be assigned to SiIV lambda 1397, HI Lyalpha , possibly PV lambda lambda 1118,1128, NIII lambda lambda 991.6,989.8, CIII lambda 977, SVI lambda lambda 933.4,944.5, OIII blends near lambda 833 and lambda 702, and OV lambda 629.7. HeI lambda 584.1 absorption is not detected in the trough system but the S/N ratio in the spectrum is not sufficient to rule out weak HeI lines. Strong HeI lines could be expected if regions of lower ionization were mixed with the high ionization gas in the BAL region. Korista et al. (1992, Ap. J. in press) discuss the possible detection of absorption from excited metastable OV*, NIV*, and CIII* in the spectrum of the BALQSO Q0226-1024. If these levels are collisionally populated, the BAL gas would be very dense (~ 10(11) cm(-3) ) and hot. In the PG 0946+301 spectrum, the OV* lambda 760.4 line, if present, is blended with other strong lines. The CIII* lambda 1175 line is not present to a small equivalent width limit. This work has been supported by NASA NAS 5-29293 and NAG 5-1630.