It looks to me as though, due to the difference in fluxes and pretty high positional offsets, that for both 0931 and 1532, the RASS source was not detected with chandra, even when recalculating the expected counts accounting for RASS errors in counts.


For 0931+3622 and 1532+4724

Compiled a visual of the chandra sources relative to the WD, with offset, u-g values, log(f_x/f_opt) [log(f_x/f_opt)=f_x+m_v/2.5+5.47, cts, and expected count range.

Got estimates for counts from Webpimms again, this time accounting for the uncertainty in ROSAT counts. Results were as follows:

0931: n_H=1.42E+20 (.009-.025cps)
0.9e-2cps:
.06KeV: I-2.106e-3
S-3.678e-2
.1KeV: I-1.151e-2
S-5.611e-2

2.5e-2cps:
.06KeV: I-5.850e-3
S-1.022e-1
.1KeV: I-3.198e-2
S-1.559e-1

So counts should be in a range for the I array of (2.106e-3 - 3.198e-2) and for S array of (3.678e-2 - 1.559e-1)

1532: n_H=1.7 (.007-.017cps)

0.7e-2:
.06KeV: I-1.831e-3
S-2.956e-3
.1KeV: I-9.543e-3
S-4.496e-2
1.7e-2cps:
.06KeV: I-4.447e-3
S-7.179e-2
.1KeV: I-2.318e-3
S-1.092e-1

So for the I array the cps should be within (1.831e-3 - 2.318e-3) and for the S array within (2.956e-3 - 1.092e-1)