View X-Atlas Observation

Observation ID	Observation Date	Target	Star Name	Object Class	Spectral Type	B-V Magnitude	RA (deg)	DEC (deg)	Exposure (s)
1926	2001-02-11 21:20:17	VELA X-1	GP Vel	High Mass X-ray Binary	B0Ia	0.3750	135.528520	-40.554690	83149.00

Chandra Configuration for the Observation

Zeroth-Order Image

Zeroth-Order Events	Zeroth-Order Count Rate (cts/s)	Pileup
11623	0.1398	severe

The zeroth-order image for VELA X-1

Hardness Ratios and Quantiles

Hardness ratios and quantiles are calculated from the predicted ACIS-S or ACIS-I aimpoint spectra, as indicated.

Hardness Ratios
Aimpoint	HR₁ = (H-M)/(H+M)	HR₂ = (M-S)/(M+S)	HR₃ = (H-S)/(H+S)
ACIS-S	0.501	0.578	0.836
ACIS-I	0.561	0.692	0.903

S, M, and H represent the predicted total counts in the following passbands:

S: 0.3-0.9 keV

M: 0.9-1.5 keV

H: 1.5-8.0 keV

Quantiles
Aimpoint	Quantiles	25 %	25 % Error	50 %	50 % Error	75 %	75 % Error
ACIS-S	keV	1.380	0.006	2.373	0.014	4.636	0.020
ACIS-S	Q-norm	0.140	0.001	0.269	0.002	0.563	0.003
ACIS-I	keV	1.511	0.009	2.840	0.027	5.117	0.020
ACIS-I	Q-norm	0.157	0.001	0.330	0.004	0.626	0.003

Normalized quantiles (Q-norm) are defined as:

Q_x = (E_x - E_lo)/(E_hi - E_lo)

Where E_lo = 0.3 keV and E_hi = 8.0 keV.

Hardness Ratio plots and Quantile-based Color-Color Diagrams

X-Atlas Hardness Ratios and Quantiles Listing

Spectral Metrics

A series of line-line, line-continuum, and continuum-continuum ratios calculated from the high-resolution 1^st order MEG or LEG spectrum.

Line-Line Ratios
Ne X / O VIII	Ne2O Error	O VII(i) / O VII(f)	Oif Error	O VII(r) / O VIII	O78 Error	O VIII / Fe XVII	O8Fe Error	Mg XII / Fe XVII	Mg2Fe Error	Si XIV / Fe XVII	Si2Fe Error	S XV / Fe XVII	S2Fe Error
0.0000	0.0000	0.0000	0.0000	0.0000	0.0000	0.0000	0.0000	20.3252	0.0000	48.4388	0.0000	4.4322	0.0000

short line / cont

Line-Continuum & Continuum-Continuum Ratios
sl2c Error	long line / cont	ll2c Error	line / cont	l2c Error	cont long / cont short	cl2cs Error	cont long / cont med	cl2cm Error	cont med / cont short	cm2cs Error
0.0949	0.0086	0.0021	0.0022	0.0990	0.0090	0.0364	0.0003	0.0457	0.0004	3.9467	0.0172

X-Atlas Spectral Metrics Listing

Spectral Fits

Image File Missing: 2T xsmekal zeroth-order fit
Mewe-Kaastra-Liedahl 2-temperature fit of the low-resolution zeroth-order spectrum of VELA X-1.
Warning: The zeroth-order spectrum may be subject to distortions from pileup.

Image File Missing: 2T xsmekal ACIS-S fit
Mewe-Kaastra-Liedahl 2-temperature fit of the predicted low-resolution ACIS-S Aimpoint spectrum of VELA X-1. The predicted spectrum was scaled to 1500 counts.

Image File Missing: 2T xsmekal ACIS-I fit
Mewe-Kaastra-Liedahl 2-temperature fit of the predicted low-resolution ACIS-I Aimpoint spectrum of VELA X-1. The predicted spectrum was scaled to 1500 counts.

Aimpoint	Model	nH (10²²/cm³)	nH error	kT (keV)	kT error	kT2 (keV)	kT2 error	Abundance (solar)	Abundance error	Flux (ergs/cm²/s)	Flux Emission Ratio (kT2/kT1)	Reduced Chi²	DoF
zeroth-order	xswabs*(xsmekal1+xsmekal2)	2.962		30.000		0.068		3.04		6.04556e-12	0	6.30	406
ACIS-S	xswabs*(xsmekal1+xsmekal2)	0.010		30.000		1.000		0.16		1.06772e-13	0	7.24	79
ACIS-I	xswabs*(xsmekal1+xsmekal2)	0.010		30.000		1.000		1.50		1.70409e-13	0	5.33	80

X-Atlas Spectral Fits Listing

HETG Light Curve

GLvary
Odds	293.787
Prob.	1.000
Var. Index	10

HETG light curve for VELA X-1, constructed from all ±1^st, ±2^nd, and ±3^rd order HETG events.

HETG HEG Spectrum

Image File Missing: High-Resolution 1st Order HEG spectrum of obsid 1926

High-Resolution 1st Order HEG Spectrum for VELA X-1

HETG MEG Spectrum

Image File Missing: High-Resolution 1st Order MEG Spectrum of obsid 1926

High-Resolution 1st Order MEG Spectrum for VELA X-1

X-Atlas Data Products

Spectral Data
PHA II	HEG ±1^st Order PHA	HEG ±1^st Order gARF	MEG ±1^st Order PHA	MEG ±1^st Order gARF	[Counts/s/Å] FITS	[Counts/s/Å] text	[ph/s/Å/cm²] FITS	[ph/s/Å/cm²] text

Standard Data Products (Cycle 06)
Aimpoint ARF		Aimpoint RMF
ACIS-S	ACIS-I	ACIS-S	ACIS-I

Retrieve observation data from the Chandra Data Archive: WebChaSeR

Target Preview