M104 R0–15 EPIC camera comparison

Previous mixed contract vs. traditional 3B masked full region · ObsID 0900170101

发布于

2026年7月13日

核心结论 / Executive conclusion

Traditional 3B full-region结果确认：pn0仍提供最强的单相机Fe-L统计，但previous comparison中“PN压倒MOS”的程度被4B MOS较短GTI和较小BACKSCAL extraction area放大了。

在0.7–1.05 keV：

  • Previous mixed contract（4B MOS + 3B pn0）：MOS1+MOS2净计数为3,516，pn0为8,592，pn/MOS净计数比为2.44；
  • Traditional 3B masked full region（3B MOS1+MOS2+pn0）：MOS1+MOS2净计数提高到5,534，pn0仍为8,592，pn/MOS净计数比降到1.55；
  • MOS-only naive independent-counts S/N由44.7提高到56.4；加入pn0后的naive S/N由85.5提高到92.2；
  • 3B MOS1/MOS2/pn0的Fe-L high/low分别为0.559 / 0.597 / 0.585。MOS1–PN0和MOS2–PN0只相差−0.71σ与+0.37σ；
  • 因此pn0仍值得进入controlled MOS+PN forward-folded validation fit，但1.63或1.91的counts-space S/N比值都不是kT precision forecast。

English summary. The all-3B comparison recovers substantially more MOS counts because the traditional MOS products have longer exposures and larger extraction footprints/BACKSCAL sky areas. PN0 remains the strongest single-camera Fe-L dataset, but its net-count advantage over MOS1+MOS2 decreases from 2.44 to 1.55. The response/area-normalized Fe-L colors remain statistically compatible. These are QPB-subtracted quick-look spectra, not fitted source-component significances; the counts-space gain is not a kT precision forecast.

两套数据合同 / Two data contracts

Detector Previous mixed Exposure / PHA area Traditional 3B Exposure / PHA area
MOS1 4.background masked full-FOV alias 65.76 ks / 120.3 arcmin² 3B.background_20250124/...exclude_extent_source_mask 78.81 ks / 162.6 arcmin²
MOS2 4.background masked full-FOV alias 65.23 ks / 335.0 arcmin² 3B.background_20250124/...exclude_extent_source_mask 80.03 ks / 396.9 arcmin²
pn0 3B.background_20250124/...pn0...mask 55.37 ks / 369.8 arcmin² 同一个pn0 PHA/QPB/ARF/RMF 55.37 ks / 369.8 arcmin²

PN0在两套合同中的PHA、QPB、ARF和RMF SHA256全部相同，因此是严格control；新旧曲线差异只来自MOS产品。MOS和PN的camera footprints仍不是pixel-identical common aperture。

新旧谱直接对照 / Direct old–new comparison

0.4–3.2 keV ARF-unfolded surface brightness

Stacked previous mixed and traditional 3B R0-15 EPIC ARF-unfolded spectra

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两panel显式使用相同x/y尺度（sb_flux y-limit=9×10⁻⁸–3×10⁻⁵）。0.4–1.2 keV总体shape稳定；1.49和1.74 keV附近的强结构属于instrumental-line-sensitive区。2–3.2 keV中3B MOS的sb_flux可高约12–25%，更可能反映GTI、residual particle/SP和response-weighting差异，不能直接解释为hotter source plasma。

0.6–1.2 keV Fe-L zoom

Stacked previous mixed and traditional 3B Fe-L zoom spectra

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Traditional 3B中MOS曲线的误差更小、grouped bins更多；三台仪器的Fe-L continuum slope仍相容。该图没有模型或fit，不能区分M104、foreground、CXB、soft proton与OoT成分。

0.7–1.05 keV定量比较

Previous mixed contract

Detector Source Scaled QPB Net S/N QPB fraction Mean ARF
MOS1 1,750 582 1,168 27.5 33.3% 172 cm²
MOS2 4,129 1,781 2,348 35.5 43.1% 164 cm²
pn0 12,447 3,855 8,592 72.9 31.0% 495 cm²

Traditional 3B masked full region

Detector Source Scaled QPB Net S/N QPB fraction Mean ARF
MOS1 2,987 1,029 1,958 35.2 34.4% 173 cm²
MOS2 6,088 2,513 3,575 44.3 41.3% 160 cm²
pn0 12,447 3,855 8,592 72.9 31.0% 495 cm²

3B相对previous的MOS变化

Detector Exposure PHA area Net counts S/N Net rate per area Approx. sb_flux
MOS1 +19.8% +35.2% +67.7% +28.0% +3.5% +2.9%
MOS2 +22.7% +18.5% +52.3% +24.9% +4.8% +7.1%
pn0 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%

结论是：增加的大部分是MOS BACKSCAL extraction area×exposure带来的counts与S/N，不是instrumental effective area（ARF）或面亮度突然上升。 Fe-L mean ARF只变化+0.6%/−2.2%，sb_flux只变化约3–7%。

Fe-L color一致性

Physical half-open bands：low [0.700,0.875) keV，high [0.875,1.050) keV。统计使用RMF-channel midpoint lo <= E_mid < hi，避免pn非线性EBOUNDS边界channel双计数。

下表误差和z-score为count/QPB-statistical only：只传播source Poisson与QPB STAT_ERR，假设两个band独立；不含ARF/RMF calibration、soft-proton、sky/OoT或共同系统误差。

Contract MOS1 high/low MOS2 high/low pn0 high/low MOS1–PN0 MOS2–PN0
Previous mixed 0.517 ± 0.039 0.589 ± 0.033 0.585 ± 0.017 −1.61σ +0.11σ
Traditional 3B 0.559 ± 0.032 0.597 ± 0.027 0.585 ± 0.017 −0.71σ +0.37σ

3B处理后MOS1与pn0的差异缩小；MOS2在两套合同中均与pn0一致。该变化consistent with sensitivity to the compound processing/footprint contract，但PHA、QPB、ARF和RMF同时改变，不能隔离具体因果，也不构成精密cross-calibration测量。

Traditional 3B-only inspect

Broad sb_flux

Traditional 3B-only MOS1 MOS2 pn0 broad ARF-unfolded spectrum

PDF

Fe-L zoom sb_flux

Traditional 3B-only MOS1 MOS2 pn0 Fe-L zoom

PDF

所有inspection使用xsherpa.inspect.SpectrumInspector；energy=0.4–3.2 keV；group_subtracted_oversampling_SNR(sampling_rate=5, SNR=6)；QPB subtraction；y-log；no model；no fit。Mandatory rate、sb、sb_flux和1col/2col PNG/PDF均保存在本地science output中。

Scientific limits / 科学边界

  1. QPB-subtracted不等于pure M104。 谱中仍含sky foreground/background、CXB、residual soft proton、instrumental residuals和可能的pn OoT。
  2. PATTERN==0 is not an OoT correction。 pn0是single-pixel/high-resolution选择；Extended Full Frame的OoT必须由matched OoT product单独处理。
  3. Mask不是common aperture。 MOS1/MOS2/pn的chip gaps、bad pixels和camera coverage不同；PHA BACKSCAL只记录各自的extraction area，不是ARF instrumental effective area。
  4. ARF-unfold只用于quick-look。 Extended-source定量推断必须使用forward-folded detector-specific models。
  5. 3B并非因此自动成为production baseline。 它提供更多MOS统计，但previous项目采用4B有其GTI/QPB筛选理由。需要在同一source/background/GTI/OoT合同下做MOS-only和MOS+pn forward-folded validation fit才能决定。

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