Caveat: ACIS Event Thresholds
A number of Chandra ACIS observations which have been processed with the Level 3 pipeline and are contained in the Chandra Source Catalog have zero sensitivity in parts of the event energy range encompassed by the CSC science energy bands (0.2 keV - 7 keV). This is on account of the observer's ability to alter the default on-board energy filters for ACIS, which is appropriate when sources are expected to have spectra in a restricted energy range or count rate saturation is a concern (see the CIAO caveats page for more details). In other words, the low energy threshold of events in some ObsIDs lies above the lowest energy considered by the CSC (0.2 keV), and/or the high event energy threshold lies below the highest energy considered (7 keV). In the CSC 2.0 release there are no sources in the catalog that have a lower high event energy threshold. Catalog source properties which are affected by these energy gaps are assigned a value of INDEF in processing, and are reported with a null value in the catalog, where appropriate. For example, a source with a low event energy threshold of 1.0 keV would have a value of 0.0 for certain ultrasoft (u), soft (s), and broad (b) band flux properties in the catalog (the source has zero flux in the u band and only partial coverage in the s and b bands).
The effective energy thresholds vary by chip, node, time, and grade, and the ARFs and RMFs created for the affected observations may not correctly represent the instrument settings. For the CSC, this means that certain aperture model energy fluxes, spectral model fit parameters, and hardness ratios may be affected, since the spectral instrumental signature is removed from these values (but not from the counts values). Specifically, the following per-observation source properties for the u-, b-, and s-bands must be considered:
Aperture Model Energy Fluxes- o.flux_powlaw_aper_〈band〉 + limits
- o.flux_powlaw_aper90_〈band〉 + limits
- o.flux_bb_aper_〈band〉 + limits
- o.flux_bb_aper90_〈band〉 + limits
- o.flux_brems_aper_〈band〉 + limits
- o.flux_brems90_〈band〉 + limits
- o.flux_apec_aper_〈band〉 + limits
- o.flux_apec_aper90_〈band〉 + limits
- o.powlaw_gamma + limits
- o.flux_powlaw + limits
- o.powlaw_nh + limits
- o.powlaw_ampl + limits
- o.powlaw_stat
- o.bb_kt + limits
- o.flux_bb + limits
- o.bb_nh + limits
- o.bb_ampl + limits
- o.bb_stat
- o.brems_kt + limits
- o.flux_brems + limits
- o.brems_nh + limits
- o.brems_norm + limits
- o.brems_stat
- o.hard_hm + limits
- o.hard_hs + limits
- o.hard_ms + limits
The ObsIds with partial coverage of the CSC science energy bands are listed below. The ones with high lower thresholds (0.24-0.4, 0.5, and 1.0 keV) will have null values for the u-, s-, and b-band per-observation source properties listed above.
ObsIDs with Lower Energy Threshold: |
U Band Source Fluxes |
S Band Source Fluxes |
B Band Source Fluxes |
Hardness Ratios |
Spectral Model Fit Parameters and Fluxes |
|---|---|---|---|---|---|
(flux_powlaw_*_u, flux_bb_*_u) |
(flux_powlaw_*_s, flux_bb_*_s) |
(flux_powlaw_*_b, flux_bb_*_b) |
|||
| 0.24-0.4 | null | ||||
| 0.5 | null | null | null | ||
| 1.0 | null | null | null | null | null |
The corresponding master source properties and stacked observation detections properties will have null values as well if all observations contributing to a master source or stacked observation entry have null values; otherwise, the master source properties and stacked observation properties will be computed from the non-null observations. Be aware that the inter-observation variability of these master sources and stacked observations may not be reliable. Finally, bear in mind that certain aperture source energy fluxes (photflux_* values) are not set to null values because the flux_significance is derived from them.
| ObsID | status | grating | exp_mode | eventfilter_lower | eventfilter_higher | |
|---|---|---|---|---|---|---|
| 13811 | archived | IC 3418 | NONE | TE | 0.240000 | 12.000000 |
| 13907 | archived | IRAS F15307+3252 | NONE | TE | 0.240000 | 12.000000 |
| 14009 | archived | RXJ1532.9+3021 | NONE | TE | 0.240000 | 12.000000 |
| 13293 | archived | Puppis A -micro-X field | NONE | TE | 0.250000 | 8.250000 |
| 13612 | archived | KIC11560431 | NONE | TE | 0.250000 | 11.750000 |
| 1994 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 1995 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 1997 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 1998 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 1999 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 2001 | archived | Crab Nebula | NONE | TE | 0.300000 | 12.000000 |
| 3499 | archived | RCrADarkCloud | NONE | TE | 0.300000 | 12.000000 |
| 3507 | archived | XTE J1709-267 | NONE | TE | 0.300000 | 13.000000 |
| 3508 | archived | 2S1711-339 | NONE | TE | 0.300000 | 13.000000 |
| 3509 | archived | A1744-361 | NONE | TE | 0.300000 | 13.000000 |
| 3510 | archived | 4U1755-33 | NONE | TE | 0.300000 | 13.000000 |
| 3838 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 3877 | archived | SGR 1627-41 | NONE | TE | 0.300000 | 12.000000 |
| 4385 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4386 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4387 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4388 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4389 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4390 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4391 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4392 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4393 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4394 | archived | SN1006 | NONE | TE | 0.300000 | 12.000000 |
| 4475 | archived | RCrADarkCloud | NONE | TE | 0.300000 | 12.000000 |
| 4626 | archived | CTB-109 Lobe | NONE | TE | 0.300000 | 12.000000 |
| 4674 | archived | Geminga | NONE | TE | 0.300000 | 10.000000 |
| 5547 | archived | G21.6-0.0 | NONE | TE | 0.300000 | 12.000000 |
| 5563 | archived | G20.0-0.2 | NONE | TE | 0.300000 | 12.000000 |
| 7031 | archived | GX9+1 | NONE | TE | 0.300000 | 8.000000 |
| 7576 | archived | PSR J0108-1431 | NONE | TE | 0.300000 | 12.700000 |
| 7577 | archived | PSR B1257+12 | NONE | TE | 0.300000 | 12.700000 |
| 8224 | archived | Cyg X-2 | NONE | TE | 0.300000 | 9.700000 |
| 8444 | archived | Cyg X-2 | NONE | TE | 0.300000 | 9.700000 |
| 8445 | archived | Cyg X-2 | NONE | TE | 0.300000 | 9.700000 |
| 8446 | archived | Cyg X-2 | NONE | TE | 0.300000 | 9.700000 |
| 10711 | archived | G289.7-0.3 | NONE | TE | 0.300000 | 12.000000 |
| 10712 | archived | G46.8-0.3 | NONE | TE | 0.300000 | 12.000000 |
| 10713 | archived | G9.95-0.81 | NONE | TE | 0.300000 | 12.000000 |
| 10880 | archived | PSR J1357-6429 | NONE | TE | 0.300000 | 10.000000 |
| 11250 | archived | PSR J1740+1000 | NONE | TE | 0.300000 | 12.000000 |
| 11831 | archived | 0FGL J1018.2-5858 | NONE | TE | 0.300000 | 12.000000 |
| 11832 | archived | 0FGL 1844.1-0335 | NONE | TE | 0.300000 | 12.000000 |
| 11833 | archived | 0FGL J1430.5-5918 | NONE | TE | 0.300000 | 12.000000 |
| 11834 | archived | 0FGL J1413.1-6203 | NONE | TE | 0.300000 | 12.000000 |
| 11835 | archived | 0FGL J1821.4-1444 | NONE | TE | 0.300000 | 12.000000 |
| 11836 | archived | 0FGL J1648.1-4606 | NONE | TE | 0.300000 | 12.000000 |
| 11837 | archived | 0FGL J1741.4-3046 | NONE | TE | 0.300000 | 12.000000 |
| 12148 | archived | 1FGL J1954.3+2836 | NONE | TE | 0.300000 | 12.000000 |
| 12149 | archived | PSR J1958+2846 | NONE | TE | 0.300000 | 12.000000 |
| 12150 | archived | PSR J1028-5819 | NONE | TE | 0.300000 | 12.000000 |
| 12151 | archived | PSR J1022-5746 | NONE | TE | 0.300000 | 12.000000 |
| 12152 | archived | HESS J1848-018 | NONE | TE | 0.300000 | 12.000000 |
| 13139 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 13146 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13147 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13150 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 13151 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 13152 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 13153 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 13154 | archived | Crab Nebula | NONE | TE | 0.300000 | 11.000000 |
| 13204 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13205 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13206 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13207 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13208 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13209 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13210 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13285 | archived | 1FGL J1311.7-3429 | NONE | TE | 0.300000 | 12.000000 |
| 13286 | archived | PSR J2238+59 | NONE | TE | 0.300000 | 12.000000 |
| 13287 | archived | HESS J1626-490 | NONE | TE | 0.300000 | 12.000000 |
| 13288 | archived | PSR J1459-60 | NONE | TE | 0.300000 | 12.000000 |
| 13289 | archived | PSR J0248+6021 | NONE | TE | 0.300000 | 12.000000 |
| 13290 | archived | PSR J1731-1847 | NONE | TE | 0.300000 | 12.000000 |
| 13750 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13751 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13752 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13754 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13755 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13756 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13757 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 13790 | archived | HESS J1741-302A | NONE | TE | 0.300000 | 12.000000 |
| 14028 | archived | RX J0334.2-0111 | NONE | TE | 0.300000 | 12.000000 |
| 14207 | archived | PSR J0357+3205 | NONE | TE | 0.300000 | 10.000000 |
| 14208 | archived | PSR J0357+3205 | NONE | TE | 0.300000 | 10.000000 |
| 14379 | archived | RX J0334.2-0111 | NONE | TE | 0.300000 | 12.000000 |
| 14416 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 14458 | archived | Crab pulsar | NONE | TE | 0.300000 | 11.000000 |
| 14519 | archived | The Mouse | NONE | TE | 0.300000 | 10.000000 |
| 14520 | archived | The Mouse | NONE | TE | 0.300000 | 10.000000 |
| 14523 | archived | PSR J1509-5850 nebula | NONE | TE | 0.300000 | 10.000000 |
| 14524 | archived | PSR J1509-5850 nebular | NONE | TE | 0.300000 | 10.000000 |
| 14657 | archived | 1FLG J1018.6-5856 | NONE | TE | 0.300000 | 10.000000 |
| 14678 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 14679 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 14680 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 14681 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 14682 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 14685 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 14821 | archived | J1906+0746 | NONE | TE | 0.300000 | 12.000000 |
| 15360 | archived | HESS J1843-033A | NONE | TE | 0.300000 | 12.000000 |
| 15361 | archived | PSR J1044-5737 | NONE | TE | 0.300000 | 12.000000 |
| 15362 | archived | PSR J1231-1411 | NONE | TE | 0.300000 | 12.000000 |
| 15363 | archived | PSR J0101-6422 | NONE | TE | 0.300000 | 12.000000 |
| 15364 | archived | PSR B1919+21 | NONE | TE | 0.300000 | 12.000000 |
| 15365 | archived | HESS J1843-033B | NONE | TE | 0.300000 | 12.000000 |
| 15366 | archived | PSR J2043+1711 | NONE | TE | 0.300000 | 12.000000 |
| 16245 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 16257 | archived | Crab | NONE | TE | 0.300000 | 11.000000 |
| 16560 | archived | 1FLG J1018.6-5856 | NONE | TE | 0.300000 | 10.000000 |
| 6690 | archived | Cas A CCO | NONE | TE | 0.350000 | 11.000000 |
| 13783 | archived | Cas A CCO | NONE | TE | 0.350000 | 11.000000 |
| 2754 | archived | MSH 11-61A | NONE | TE | 0.400000 | 13.000000 |
| 3720 | archived | MSH 11-61A | NONE | TE | 0.400000 | 13.000000 |
| 4596 | archived | RCW103 | NONE | TE | 0.400000 | 10.000000 |
| 4597 | archived | RCW103 | NONE | TE | 0.400000 | 10.000000 |
| 4598 | archived | RCW103 | NONE | TE | 0.400000 | 10.000000 |
| 4599 | archived | RCW103 | NONE | TE | 0.400000 | 10.000000 |
| 5592 | archived | RCW103 | NONE | TE | 0.400000 | 10.000000 |
| 5593 | archived | RCW103 | NONE | TE | 0.400000 | 10.000000 |
| 5594 | archived | RCW103 | NONE | TE | 0.400000 | 10.000000 |
| 5595 | archived | RCW103 | NONE | TE | 0.400000 | 10.000000 |
| 7639 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 8551 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 10093 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 10094 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 10095 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 10096 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 10097 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 10902 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 10903 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 10904 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| 10906 | archived | Tycho's SNR | NONE | TE | 0.400000 | 12.000000 |
| ObsID | status | grating | exp_mode | eventfilter_lower | eventfilter_higher | |
|---|---|---|---|---|---|---|
| 2785 | archived | G349.7+0.2 | NONE | TE | 0.500000 | 12.000000 |
| 5530 | archived | G15.9+0.2 | NONE | TE | 0.500000 | 12.000000 |
| 6288 | archived | G15.9+0.2 | NONE | TE | 0.500000 | 12.000000 |
| 6289 | archived | G15.9+0.2 | NONE | TE | 0.500000 | 12.000000 |
| ObsID | status | grating | exp_mode | eventfilter_lower | eventfilter_higher | |
|---|---|---|---|---|---|---|
| 2267 | archived | GCS 20 | NONE | TE | 1.000000 | 10.000000 |
| 2268 | archived | GCS 21 | NONE | TE | 1.000000 | 10.000000 |
| 2269 | archived | GCS 1 | NONE | TE | 1.000000 | 10.000000 |
| 2270 | archived | GCS 22 | NONE | TE | 1.000000 | 10.000000 |
| 2271 | archived | GCS 2 | NONE | TE | 1.000000 | 10.000000 |
| 2272 | archived | GCS 23 | NONE | TE | 1.000000 | 10.000000 |
| 2273 | archived | GCS 10 | NONE | TE | 1.000000 | 10.000000 |
| 2274 | archived | GCS 3 | NONE | TE | 1.000000 | 10.000000 |
| 2275 | archived | GCS 24 | NONE | TE | 1.000000 | 10.000000 |
| 2276 | archived | GCS 11 | NONE | TE | 1.000000 | 10.000000 |
| 2277 | archived | GCS 4 | NONE | TE | 1.000000 | 10.000000 |
| 2278 | archived | GCS 25 | NONE | TE | 1.000000 | 10.000000 |
| 2279 | archived | GCS 12 | NONE | TE | 1.000000 | 10.000000 |
| 2280 | archived | GCS 5 | NONE | TE | 1.000000 | 10.000000 |
| 2281 | archived | GCS 26 | NONE | TE | 1.000000 | 10.000000 |
| 2282 | archived | GCS 13 | NONE | TE | 1.000000 | 10.000000 |
| 2283 | archived | GCS 27 | NONE | TE | 1.000000 | 10.000000 |
| 2284 | archived | GCS 14 | NONE | TE | 1.000000 | 10.000000 |
| 2285 | archived | GCS 6 | NONE | TE | 1.000000 | 10.000000 |
| 2286 | archived | GCS 28 | NONE | TE | 1.000000 | 10.000000 |
| 2287 | archived | GCS 15 | NONE | TE | 1.000000 | 10.000000 |
| 2288 | archived | GCS 7 | NONE | TE | 1.000000 | 10.000000 |
| 2289 | archived | GCS 29 | NONE | TE | 1.000000 | 10.000000 |
| 2290 | archived | GCS 30 | NONE | TE | 1.000000 | 10.000000 |
| 2291 | archived | GCS 16 | NONE | TE | 1.000000 | 10.000000 |
| 2292 | archived | GCS 8 | NONE | TE | 1.000000 | 10.000000 |
| 2293 | archived | GCS 17 | NONE | TE | 1.000000 | 10.000000 |
| 2294 | archived | GCS 9 | NONE | TE | 1.000000 | 10.000000 |
| 2295 | archived | GCS 18 | NONE | TE | 1.000000 | 10.000000 |
| 2296 | archived | GCS 19 | NONE | TE | 1.000000 | 10.000000 |