X-ray Hardness and Quantiles

Hardness ratios calculated from the predicted ACIS-S Aimpoint spectra of selected X-Atlas targets (× = hot star; ◊ = cool star). S, M, and H are the total predicted counts in the passbands listed on the plot. Theta-2 Ori A in Obsid 4474 is circled in red on the plot.

Hardness ratios calculated from the predicted ACIS-I Aimpoint spectra of selected X-Atlas targets (× = hot star; ◊ = cool star). S, M, and H are the total predicted counts in the passbands listed on the plot. Theta-2 Ori A in Obsid 4474 is circled in red on the plot.

Hardness Ratios for Theta-2 Ori A, Obsid 4474
Aimpoint	HR₁ = (H-M)/(H+M)	HR₂ = (M-S)/(M+S)	HR₃ = (H-S)/(H+S)
ACIS-S	0.071	0.400	0.458
ACIS-I	0.115	0.577	0.649

X-ray Quantiles

Quantile-based color-color diagram: (m = Q₅₀ = (E₅₀ - E_lo)/(E_hi - E_lo)). E_lo = 0.3 keV; E_hi = 8.0 keV

View complete listing of X-Atlas Spectral Metrics (Hardness, Quantiles).

Quantiles for Theta-2 Ori A, Obsid 4474

Aimpoint Quantiles 25 % 25 % Error 50 % 50 % Error 75 % 75 % Error
ACIS-S keV 1.029 0.002 1.409 0.004 2.008 0.008

Q-norm 0.095 0.000 0.144 0.001 0.222 0.001
ACIS-I keV 1.132 0.003 1.497 0.007 2.154 0.018

Q-norm 0.108 0.000 0.155 0.001 0.241 0.002

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ACIS-S hot stars JPG Postscript	ACIS-S cool stars JPG Postscript
ACIS-I hot stars JPG Postscript	ACIS-I cool stars JPG Postscript

Quantiles for Theta-2 Ori A, Obsid 4474
Aimpoint	Quantiles	25 %	25 % Error	50 %	50 % Error	75 %	75 % Error
ACIS-S	keV	1.029	0.002	1.409	0.004	2.008	0.008
ACIS-S	Q-norm	0.095	0.000	0.144	0.001	0.222	0.001
ACIS-I	keV	1.132	0.003	1.497	0.007	2.154	0.018
ACIS-I	Q-norm	0.108	0.000	0.155	0.001	0.241	0.002