tokens: with the power-law function. The fits included wavelength intervals that were free of BALs and ranged from approximately 1260–1350, 1370–1480, 1530–1800, and 1870–2500 Å. We integrated the P v BAL apparent optical depth profiles using the following equation, in Gaussian units: where f is the oscillator strength, λ is the rest wavelength, and τ( v ) is the apparent optical depth at a given velocity (Savage Sembach 1991 ). Rest wavelengths and oscillator strength values were taken from Morton ( 2003 ), and we treat the P v λλ1117,1128 doublet as a single line at λ = 1121 Å with an average oscillator strength of f = 0.705. For sources that showed non-variable P v BALs, we integrated τ( v ) in accordance with equation ( 1 ). For sources that showed variable P v BALs, we integrated the optical depth difference to generate lower limits for the change in P v column density. 4 RESULTS AND DISCUSSION 4.1 Absorption line variability We detect definite (category Y, see Section 3.1 ) variability from any BAL (i.e. from C iv , Si iv , or P v ) in 10 out of 71 BAL quasars in our sample (see Appendix A for notes on individual objects). Spectroscopic comparisons in our sample probe rest-frame time-scales between 0.5 d and 3.8 yr, and we measure BAL variability time-scales over ≤ 0.2–3.8 yr for our Y sources. Tentative (T) variations from any BAL are detected in 44 sources, and 17 objects exhibit no (N) BAL changes. Table 3 lists the associated ion, measured variability time-scale, LOS velocity of the variable region, and variability direction for each variable (Y) BAL in our sample. BALs not presented in Table 3 show no significant absorption line changes over the listed time-scales. For example, there are four cases of P v and/or Si iv BAL variations with no associated C iv BAL changes in the same time-scale comparison (see 013652 + 122501, 104059 + 055524, 104247 + 061521, and 0.5 yr for 122654−005430 in Table 3 ). We detect four cases of C iv BAL variability with non-variable P v absorption at similar velocities (see 2.4 yr for 122654−005430, 0.8 yr for 140532 + 022947, along with 2.0 and 0.8 yr for 221326 + 003846 in Table 3 ). There are five cases of C iv BAL changes with likely no associated P v absorption at similar velocities (see 102154 + 051646, 114548 + 393746, 2.4 and 0.8 yr for 122654−005430, and 2.4 yr for 140532 + 022947 in Table 3 ). In two cases (025042 + 003536 and 230721 + 011118; see Table 3 ), it is unclear if the C iv BAL variations are associated with P v absorption at the same velocity. Table 3. Variable BAL properties. Information listed for each BAL quasar includes (from left to right): ions associated with variable BALs, measured time-scales of BAL variability (upper limits that are limited by temporal sampling), LOS velocities corresponding to maximum flux changes within the BALs, and whether the BAL depths increased (+) or decreased (−). Multiple, distinct time-scales listed for the same ion are in chronological order.
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