ROSAT Status Report #78:
Dec 22, 1993
We have received several questions about the PSPC "PI" or "energy" bands and channels. Below we summarize pertinent information on this subject.
PSPC PI bands
The PSPC detector has 256 channels of pulse height information which are corrected to Pulse-height Invariant (PI) channels and "down-binned" into 34 channels for SASS spectral analysis (cf. Table 2). SASS refers to its various "energy" bands by letter (for hardness ratios), name (common X-ray astronomy term), and number (for images), as indicated in Table 1:
TABLE 1: SASS PI Bands
band 256-bin 34-bin name image
---- ------- ------ ------- -----
A 11- 41 3-10 "soft" 3
B 52-201 13-30 "hard" 2
A+B 11-235 3-33 "total" 1
C 52- 90 13-18 - -
D 91-201 19-30 - -
- 42- 51 11-12 "carbon edge" -
These bands and binning schemes were adjusted slightly (both within SASS and in off-line usage) following the PSPC gain change that was introduced in October 1992 to correct the "low pulses" problem. The December 1992 version of the "ROSAT Data Products Guide" reflects these changes (cf. pp. PSPC 3-1 and PSPC 5c-1), which removed the bottom three PI bins (of the 256-channel scheme, i.e., 8-10) from the soft band and also moved the boundaries of the "compressed" 34-bin scheme slightly to accommodate this adjustment.
PSPC PI channels
The PI-channel binning scheme now in use is given in Table 2. For spectral analysis, it is recommended that 34-bin numbers 1, 2, 33, and 34 (#) be excluded from the fits.
TABLE 2: SASS PI bins
34-bin Energy 256-channels 34-bin Energy 256-channels
number Low - High included number Low - High included
------ ----- ----- ---------- ------ ----- ----- -----------
# 1 # 0.07 - 0.09 # 7 - 8 # 18 0.84 - 0.91 84 - 90
# 2 # 0.09 - 0.11 # 9 - 10# 19 0.91 - 0.99 91 - 98
3 0.11 - 0.14 11 - 13 20 0.99 - 1.07 99 - 106
4 0.14 - 0.17 14 - 16 21 1.07 - 1.15 107 - 114
5 0.17 - 0.20 17 - 19 22 1.15 - 1.23 115 - 122
6 0.20 - 0.24 20 - 23 23 1.23 - 1.32 123 - 131
7 0.24 - 0.28 24 - 27 24 1.32 - 1.41 132 - 140
8 0.28 - 0.32 28 - 31 25 1.41 - 1.50 141 - 149
9 0.32 - 0.37 32 - 36 26 1.50 - 1.60 150 - 159
10 0.37 - 0.42 37 - 41 27 1.60 - 1.70 160 - 169
11 0.42 - 0.47 42 - 46 28 1.70 - 1.80 170 - 179
12 0.47 - 0.52 47 - 51 29 1.80 - 1.91 180 - 190
13 0.52 - 0.58 52 - 57 30 1.91 - 2.02 191 - 201
14 0.58 - 0.64 58 - 63 31 2.02 - 2.13 202 - 212
15 0.64 - 0.70 64 - 69 32 2.13 - 2.24 213 - 223
16 0.70 - 0.77 70 - 76 # 33 # 2.24 - 2.36 # 224 - 235 #
17 0.77 - 0.84 77 - 83 # 34 # 2.36 - 2.48 # 236 - 247 #
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