AHELP for CIAO 4.5 Sherpa v1

xs

Context: models

Synopsis

XSpec model functions.

Description

Sherpa includes the "additive" and "multiplicative" models of XSpec version 12.7.1. The XSpec model names have the prefix "xs", e.g. XSpec phabs model is called "xsphabs."

The additive (atable) and multiplicative (mtable) XSPEC-style table models are supported by the load_table_model command.

Important Note:

XSpec models based on physical processes (e.g. line models such as raymond or absorption models such as wabs) assume that the dataspace is defined in keV. On the other hand, Sherpa models are always calculated based on the input data scale. Thus when XSpec models are combined with Sherpa models, the user should be careful to ensure that both components have the same dataspace units; otherwise, calculated model amplitudes may be incorrect.

These models also expect that the x-values will always be energy bins. When the analysis setting is using non-energy bins and an XSPEC model is defined, Sherpa converts the bins to energy before sending them to the XSPEC model. After the XSPEC model finishes, Sherpa converts back to the original units. Sherpa also scales the model values appropriately (e.g., if counts/keV came out of the XSPEC model and Sherpa is working with wavelength, then Sherpa scales the output of the XSPEC model to counts/Angstrom).

Unavailable XSPEC Models and Commands

The "etable" XSPEC components are NOT included in CIAO.

Available XSPEC Models

The available XSpec models are listed below. Refer to the ahelp page for each model (e.g. "ahelp xsabsori") or the XSpec User's Guide for more information. Note that the ahelp files describe the version of the XSpec model included in CIAO, while the XSpec User's Guide may reference a newer version with different options.

<xspecname>	Description
absori	Ionized absorber
acisabs	Decay in the ACIS quantum efficiency
apec	APEC thermal plasma model
bapec	APEC thermal plasma model with velocity broadening
bbody	Blackbody spectrum
bbodyrad	Blackbody spectrum with norm proportional to surface area
bexrav	E-folded broken power law reflected from neutral matter
bexriv	E-folded broken power law reflected from ionized matter
bkn2pow	Broken power law, two break energies
bknpower	Broken power law
bmc	Comptonization by relativistically moving matter
bremss	Thermal bremsstrahlung
bvapec	APEC thermal plasma model with variable abundances and velocity broadening as a free parameter
bvvapec	APEC thermal plasma model with variable abundances and velocity broadening as a free parameter (contains more abundance parameters than bvapec)
c6mekl	6th-order Chebyshev polynomial DEM using mekal
c6pmekl	Exponential of 6th-order Chebyshev polynomial DEM using mekal
c6pvmkl	Variable abundance version of c6pmekl
c6vmekl	Variable abundance version of c6mekl
cabs	Compton scattering (non-relativistic)
cemekl	Multi-temperature mekal
cevmkl	Multi-temperature vmeka
cflow	Cooling flow model
compbb	Comptonized blackbody spectrum after Nishimura et al. (1986)
compls	Comptonization spectrum after Lamb and Sanford (1979)
compps	Comptonization spectrum after Poutanen and Svenson
compst	Comptonization spectrum after Sunyaev and Titarchuk (1980)
compth	Component of Paolo Coppi's thermal/non-thermal hot plasma emission model
comptt	Comptonization spectrum after Titarchuk (1994)
constant	Energy-independent multiplicative factor
cplinear	Non-physical piecewise-linear model for low count background spectra
cutoffpl	Power law with high energy exponential cutoff
cyclabs	Cyclotron absorption line
disk	Disk model
diskbb	Multiple blackbody disk model
diskir	Irradiated inner and outer disk
diskline	Line emission from relativistic accretion disk
diskm	Disk model with gas pressure viscosity
disko	Modified blackbody disk model
diskpbb	Accretion disk, power law dependence for T(r)
diskpn	Accretion disk around a black hole
dust	Dust scattering out of the beam
edge	Absorption edge
eplogpar	Log-parabolic blazar model with nFn normalization
eqpair	Component of Paolo Coppi's thermal/non-thermal hot plasma emission model
eqtherm	Component of Paolo Coppi's thermal/non-thermal hot plasma emission model
equil	Equilibrium ionization collisional plasma model from Borkowski
expabs	Low-energy exponential cutoff
expdec	Exponential decay
expfac	Exponential factor
ezdiskbb	Multiple blackbody disk model with zero-torque inner boundary
gabs	Multiplicative gaussian absorption line
gadem	Plasma emission, multi-temperature with gaussian distribution of emission measure
gaussian	Simple gaussian line profile
gnei	Generalized single ionization NEI plasma model
grad	GR accretion disk around a black hole
grbm	Gamma-ray burst model
highecut	High energy cutoff
hrefl	Simple reflection model good up to 15 keV
kerrbb	Multi-temp blackbody for thin accretion disk around a Kerr black hole
kerrd	Optically thick accretion disk around a Kerr black hole
kerrdisk	Accretion disk line emission with BH spin as free parameter
laor	Line from accretion disk around a black hole
laor2	Accretion disk with broken-power law emissivity, black hole emission line
logpar	Log-parabolic blazar model
lorentz	Lorentzian line profile
meka	Mewe-Gronenschild-Kaastra thermal plasma (1992)
mekal	Mewe-Kaastra-Liedahl thermal plasma (1995)
mkcflow	Cooling flow model based on mekal
nei	Simple nonequilibrium ionization plasma model
notch	Notch line absorption
npshock	Plane-parallel shock with ion and electron temperatures
nsa	Spectra in the X-ray range (0.05-10 keV) emitted from a hydrogen atmosphere of a neutron star
nsagrav	Neutron star hydrogen atmosphere model for different g
nsatmos	Neutron star hydrogen atmosphere model with electron conduction and self-irradiation
nsmax	Neutron Star Magnetic Atmosphere
nteea	Pair plasma model
nthcomp	Thermally comptonized continuum
optxagn	Colour temperature corrected disc and energetically coupled Comptonisation model for AGN
optxagnf	Colour temperature corrected disc and energetically coupled Comptonisation model for AGN
pcfabs	Partial covering fraction absorption
pegpwrlw	Power law with pegged normalization
pexmon	Neutral Compton reflection with self-consistent Fe and Ni lines
pexrav	Exponentially cutoff power law reflected from neutral matter
pexriv	Exponentially cutoff power law reflected from ionized matter
phabs	Photo-electric absorption
plabs	Absorption model with power law dependence on energy
plcabs	Cutoff power law observed through dense, cold matter
posm	Positronium continuum
powerlaw	Simple photon power law
pshock	Constant temperature, plane-parallel shock plasma model
pwab	Extension of partial covering fraction absorption into a power-law distribution of covering fraction
raymond	Raymond-Smith thermal plasma
redden	IR/optical/UV extinction from Cardelli et al. (1989)
redge	Recombination edge
refsch	E-folded power law reflected from an ionized relativistic disk
sedov	Sedov model with electron and ion temperatures
sirf	Self-irradiated funnel
smedge	Smoothed absorption edge
spexpcut	Super-exponential cutoff absorption
spline	Spline multiplicative factor
srcut	Synchrotron radiation from cutoff electron distribution
sresc	Synchrotron radiation from escape-limited electron distribution
sss_ice	Einstein Observatory SSS ice absorption
step	Step function convolved with gaussian
swind1	Absorption by partially ionized material with large velocity shear
tbabs	Calculates the absorption of X-rays by the ISM
tbgrain	Calculates the absorption of X-rays by the ISM with variable hydrogen to H2 ratio and grain parameters
tbvarabs	Calculates the absorption of X-rays by the ISM, allowing user to vary all abundances, depletion factors, and grain properties
uvred	UV reddening
vapec	APEC thermal plasma model with variable abundances
varabs	Photoelectric absorption with variable abundances
vbremss	Thermal bremsstrahlung spectrum with variable H/He
vequil	Ionization equilibrium collisional plasma model with variable abundances
vgadem	Plasma emission, multi-temperature with gaussian distribution of emission measure
vgnei	Non-equilibrium ionization collisional plasma model with variable abundances
vmcflow	Cooling flow model based on vmekal
vmeka	M-G-K thermal plasma with variable abundances
vmekal	M-K-L thermal plasma with variable abundances
vnei	Non-equilibrium ionization collisional plasma model with variable abundances
vnpshock	Plane-parallel shock plasma model with separate ion and electron temperatures and variable abundances
vphabs	Photoelectric absorption with variable abundances
vpshock	Constant temperature, plane-parallel shock plasma model with variable abundances
vraymond	Raymond-Smith thermal plasma with variable abundances
vsedov	Sedov model with separate ion and electron temperatures and variable abundances
vvapec	APEC thermal plasma model with variable abundances (more abundance parameters than vapec)
wabs	Photoelectric absorption (Morrison and McCammon)
wndabs	Photoelectric absorption with low energy window
xion	Reflected spectra of a photo-ionized accretion disk or ring
zbbody	Redshifted blackbody
zbremss	Redshifted thermal bremsstrahlung
zdust	Extinction by dust grains
zedge	Redshifted absorption edge
zgauss	Redshifted gaussian
zhighect	Redshifted high energy cutoff
zigm	UV/Optical attenuation by the intergalactic medium
zpcfabs	Redshifted partial covering absorption
zphabs	Redshifted photoelectric absorption
zpowerlw	Redshifted power law
zredden	Redshifted version of redden
zsmdust	Extinction by dust grains in starburst galaxies
ztbabs	Calculates the absorption of X-rays by the ISM for modeling redshifted absorption. Does not include a dust component.
zvarabs	Redshifted photoelectric absorption with variable abundances
zvfeabs	Redshifted absorption with variable iron abundance
zvphabs	Redshifted photoelectric absorption with variable abundances
zwabs	Redshifted ``Wisconsin absorption''
zwndabs	Redshifted photoelectric absorption with low energy window
zxipcf	Partial covering absorption by partially ionized material

Bugs

For a list of known bugs and issues with the XSPEC models, please visit the XSPEC bugs page.

See Also

models

absorptionedge, absorptiongaussian, absorptionlorentz, absorptionvoigt, accretiondisk, atten, bbody, bbodyfreq, beta1d, beta2d, blackbody, box1d, box2d, bpl1d, bremsstrahlung, brokenpowerlaw, ccm, const1d, const2d, cos, delta1d, delta2d, dered, devaucouleurs2d, edge, emissiongaussian, emissionlorentz, emissionvoigt, erf, erfc, exp, exp10, fm, gauss1d, gauss2d, hubblereynolds, jdpileup, linebroad, list_model_components, list_models, lmc, log, log10, logabsorption, logemission, logparabola, lorentz1d, lorentz2d, models, normbeta1d, normgauss1d, normgauss2d, opticalgaussian, poisson, polynom1d, polynom2d, polynomial, powerlaw, powlaw1d, recombination, scale1d, scale2d, schechter, seaton, sersic2d, sin, sm, smc, sqrt, stephi1d, steplo1d, tablemodel, tan, xgal, xsabsori, xsacisabs, xsapec, xsbapec, xsbbody, xsbbodyrad, xsbexrav, xsbexriv, xsbkn2pow, xsbknpower, xsbmc, xsbremss, xsbvapec, xsbvvapec, xsc6mekl, xsc6pmekl, xsc6pvmkl, xsc6vmekl, xscabs, xscemekl, xscevmkl, xscflow, xscompbb, xscompls, xscompps, xscompst, xscompth, xscomptt, xsconstant, xscplinear, xscutoffpl, xscyclabs, xsdisk, xsdiskbb, xsdiskir, xsdiskline, xsdiskm, xsdisko, xsdiskpbb, xsdiskpn, xsdust, xsedge, xseplogpar, xseqpair, xseqtherm, xsequil, xsexpabs, xsexpdec, xsexpfac, xsezdiskbb, xsgabs, xsgadem, xsgaussian, xsgnei, xsgrad, xsgrbm, xshighecut, xshrefl, xskerrbb, xskerrd, xskerrdisk, xslaor, xslaor2, xslogpar, xslorentz, xsmeka, xsmekal, xsmkcflow, xsnei, xsnotch, xsnpshock, xsnsa, xsnsagrav, xsnsatmos, xsnsmax, xsnteea, xsnthcomp, xsoptxagn, xsoptxagnf, xspcfabs, xspegpwrlw, xspexmon, xspexrav, xspexriv, xsphabs, xsplabs, xsplcabs, xsposm, xspowerlaw, xspshock, xspwab, xsraymond, xsredden, xsredge, xsrefsch, xssedov, xssirf, xssmedge, xsspexpcut, xsspline, xssrcut, xssresc, xssss_ice, xsstep, xsswind1, xstbabs, xstbgrain, xstbvarabs, xsuvred, xsvapec, xsvarabs, xsvbremss, xsvequil, xsvgadem, xsvgnei, xsvmcflow, xsvmeka, xsvmekal, xsvnei, xsvnpshock, xsvphabs, xsvpshock, xsvraymond, xsvsedov, xsvvapec, xswabs, xswndabs, xsxion, xszbbody, xszbremss, xszdust, xszedge, xszgauss, xszhighect, xszigm, xszpcfabs, xszphabs, xszpowerlw, xszredden, xszsmdust, xsztbabs, xszvarabs, xszvfeabs, xszvphabs, xszwabs, xszwndabs, xszxipcf