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Subsections

Additive Model Components N-Z

  
nei

Non-equilibrium ionization collisional plasma model. This assumes a constant temperature and single ionization parameter. It provides a characterisation of the spectrum but is not a physical model. The references for this model can be found under the description of the equil model. The references for this model can be found under the description of the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  plasma temperature (keV)
par2     =  Metal abundances (He fixed at cosmic). The elements included are C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni. Abundances are given by the Anders & Grevesse mixture.
par3     =  Ionization timescale in units of s/cm3.
par4     =  redshift z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
npshock

Plane-parallel shock plasma model with separate ion and electron temperatures. This model is slow. par1 provides a measure of the average energy per particle (ions+electrons) and is constant throughout the postshock flow in plane shock models (Borkowski et al., 2001, ApJ, 548, 820). par2 should always be less than par1. If par2 exceeds par1 then their interpretations are switched (ie the larger of par1 and par2 is always the mean temperature). Additional references can be found under the help for the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  mean shock temperature (keV)
par2     =  electron temperature immediately behind the shock front (keV).
par3     =  Metal abundances (He fixed at cosmic). The elements included are C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni. Abundances are given by the Anders & Grevesse mixture.
par4     =  Lower limit on ionization timescale (s/cm3) to include.
par5     =  Upper limit on ionization timescale (s/cm3) to include.
par6     =  redshift z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
nsa

This model provides the spectra in the X-ray range (0.05-10 keV) emitted from a hydrogen atmosphere of a neutron star. There are three options : nonmagnetized (B < 108 - 109 G) with a uniform surface (effective) temperature in the range of $\log T_{eff}(K) = 5.0-7.0$; a field B = 1012 G with a uniform surface (effective) temperature in the range of $\log T_{eff}(K) = 5.5-6.8$; a field B = 1013 G with a uniform surface (effective) temperature in the range of $\log T_{eff}(K) = 5.5-6.8$. The atmosphere is in radiative and hydrostatic equilibrium; sources of heat are well below the atmosphere. The Comptonization effects (significant at $T_{eff} >
3\times10^6$ K) are taken into account. The model spectra are provided as seen by a distant observer, with allowance for the GR effects. The user is advised to keep Mns and Rns fixed and fit the temperature and the normalization. MagField must be fixed at one of 0, 1012, or 1013.

The values of the effective temperature and radius as measured by a distant observer (``values at infinity'') are :


\begin{displaymath}T_{eff}^\infty = g_r*T_{eff} \end{displaymath}


\begin{displaymath}R_{ns}^\infty = R_{ns}/g_r \end{displaymath}

where gr=(1-2.952*Mns/Rns)0.5 is the gravitational redshift parameter.

Please send your comments/questions (if any) to Slava Zavlin (zavlin@mpe.mpg.de) and/or George Pavlov (pavlov@astro.psu.edu). If you publish results obtained using this model please reference Pavlov et al. (1992, MNRAS 253, 193) and Zavlin et al. (1996, A&A 315, 141).

par1     =  logT_eff, (unredshifted) effective temperature
par2     =  M_ns, neutron star gravitational mass (in units of solar mass)
par3     =  R_ns, neutron star radius (in km)
par4     =  MagField, neutron star magnetic field (0, 1e12, or 1e13 G)
K     =  1/D2, where D is the distance of the object in pc.

  
nteea

A nonthermal pair plasma model based on that of Lightman & Zdziarski (1987, ApJ 319, 643) from Magdziarz and Zdziarski. It includes angle-dependent reflection from Magdziarz & Zdziarski (1995, MNRAS 273, 837). The abundances are set up by the command abund. Send questions or comments to aaz@camk.edu.pl.

par1     =  nonthermal electron compactness
par2     =  blackbody compactness
par3     =  scaling factor for reflection (1 for isotropic source above disk)
par4     =  blackbody temperature in eV
par5     =  the maximum Lorentz factor
par6     =  thermal compactness (0 for pure nonthermal plasma)
par7     =  Thomson optical depth of ionization electrons (e.g., 0)
par8     =  electron injection index (0 for monoenergetic injection)
par9     =  minimum Lorentz factor of the power law injection (not used for monoenergetic injection)
par10     =  minimum Lorentz factor for nonthermal reprocessing (>1; $ <= {\tt par9}$)
par11     =  radius in cm (for Coulomb/bremsstrahlung only)
par12     =  pair escape rate in c (0-1, see Zdziarski 1985, ApJ, 289, 514))
par13     =  cosine of inclination angle
par14     =  iron abundance relative to that defined by abund
par15     =  redshift
K     =  photon flux of the direct component (w/o reflection) at 1 keV in the observer's frame.

  
pegpwrlw

A power law with pegged normalization.


\begin{displaymath}A(E) = {\tt K}(E/1 {\rm keV})^{-{\tt par1}} \end{displaymath}

where :

par1     =  photon index of power law (dimensionless)
par2     =  lower peg energy range
par3     =  upper peg energy range
K     =  flux (in units of 10-12 erg/cm2/s) over the energy par2- par3 unless par2 = par3, in which case it is the flux (in micro-Jy) at par2

  
pexrav

Exponentially cut off power law spectrum reflected from neutral material (Magdziarz & Zdziarski 1995, MNRAS, 273, 837). The output spectrum is the sum of the cut-off power law and the reflection component. The reflection component alone can be obtained for rel_refl < 0. Then the actual reflection normalization is |rel_refl|. Note that you need to change then the limits of rel_refl excluding zero (as then the direct component appears). If Ec = 0there is no cutoff in the power law. The metal and iron abundance are variable with respect to those defined by the command abund. The opacities are from Balucinska & McCammon (ApJ 400, 699 and 1994, private communication). H and He are assumed to be fully ionized. Send questions or comments to aaz@camk.edu.pl.

par1     =  $\gamma$, power law photon index, NE prop. to $E^{-\gamma}$
par2     =  Ec, the cutoff energy in keV (if Ec = 0 there is no cutoff; one needs to change the lower limit for that)
par3     =  rel_refl, scaling factor for reflection; if <0, no direct component (rel_refl=1 for isotropic source above disk)
par4     =  redshift
par5     =  abundance of elements heavier than He relative to that defined by abund
par6     =  iron abundance relative to that defined by abund
par7     =  cosine of inclination angle
K     =  photon flux at 1 keV (photons/keV/cm2/s) of the power-law only in the observed frame.

  
pexriv

Exponentially cut off power law spectrum reflected from ionized material (Magdziarz & Zdziarski MNRAS, 273, 837; 1995). Ionization and opacities of the reflecting medium is computed as in the procedure absori. The output spectrum is the sum of the cutoff power law and the reflection component. The reflection component alone can be obtained for rel_refl < 0. Then the actual reflection normalization is |rel_refl|. Note that you need to change then the limits of rel_refl excluding zero (as then the direct component appears). If Ec = 0 there is no cutoff in the power law. The metal and iron abundances are variable with respect to those defined by the command abund. Send questions or comments to aaz@camk.edu.pl.

par1     =  $\gamma$, power law photon index, NE prop. to $E^{-\gamma}$
par2     =  Ec, the cutoff energy in keV (if Ec = 0 there is no cutoff; one needs to change the lower limit for that)
par3     =  rel_refl, scaling factor for reflection; if <0, no direct component (rel_refl=1 for isotropic source above disk)
par4     =  redshift, z
par5     =  abundance of elements heavier than He relative to that defined by abund
par6     =  iron abundance relative to that defined by abund
par7     =  cosine of inclination angle
par8     =  disk temperature in K
par9     =  disk ionization parameter, $xi = 4 \pi F_{ion}/n$, where Fion is the 5eV - 20keV irradiating flux, n is the density of the reflector; see Done et al., 1992, ApJ, 395, 275
K     =  photon flux at 1 keV (photons/keV/cm2/s) of the power-law only in the observed frame.

  
plcabs

This model describes X-ray transmission of an isotropic source of photons located at the center of a uniform, spherical distribution of matter, correctly taking into account Compton scattering. The model can be used for radial column densities up to $5 \times 10^{24}$ cm-2. The valid energy range for which data can be mod!laeled is between 10 and 18.5 keV, depending on the column density. Details of the physics of the model, the approximations used and further details on the regimes of validity can be found in Yaqoob (1997; ApJ, 479, 184). In this particular incarnation, the initial spectrum is a power law modified by a high-energy exponential cut-off above a certain threshold energy.

Also, to improve the speed, a FAST option is available in which a full integration over the input spectrum is replaced by a simple mean energy shift for each bin. This option is obtained by setting parameter 9 to a value of 1 or greater and MUST BE FIXED. Further, for single-scattering albedos less than ACRIT (i.e. parameter 8) energy shifts are neglected altogether. The recommended value is ACRIT=0.1 which corresponds to about 4 keV for cosmic abundances and is more than adequate for ASCA data.

Note that for column densities in the range 1023 - 1024 cm-2, the maximum number of scatterings which need be considered for convergence of the spectrum of better than 1% is between 1 and 5. For columns as high as $5 \times 10^{24}$, the maximum number of scatterings which need be considered for the same level of convergence is 12. **NOTE THAT NMAX MUST BE FROZEN **

par1     =  Column density in units 1022 cm-2.
par2     =  Maximum number of scatterings to consider.
par3     =  Iron abundance.
par4     =  Iron K edge energy.
par5     =  Power-law photon index.
par6     =  High-energy cut-off threshold energy.
par7     =  High-energy cut-off e-folding energy.
par8     =  Critical albedo for switching to elastic scattering.
par9     =  If ${\tt par9} > 1$ function uses mean energy shift, not integration.
par10     =  Source redshift.

  
posm

Positronium continuum (Brown & Leventhal 1987 ApJ 319, 637).


\begin{displaymath}\begin{array}{lcl}
A(E) & = & K (2.0/((3.14159^2 - 9.0)511)) ...
...E)^2/(1022-E)^3) \log((511-E)/511) + (1022-E)/E)\\
\end{array}\end{displaymath}

for E < 511 keV, where :

K     =  normalization.

  
powerlaw

Simple photon power law.


\begin{displaymath}A(E) = {\tt K}(E/1 {\rm keV})^{-{\tt par1}} \end{displaymath}

where :

par1     =  photon index of power law (dimensionless)
K     =  photons/keV/cm2/s at 1 keV.

  
pshock

Constant temperature, plane-parallel shock plasma model. The references for this model can be found under the description of the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  plasma temperature (keV)
par2     =  Metal abundances (He fixed at cosmic). The elements included are C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni. Abundances are given by the Anders & Grevesse mixture.
par3     =  Lower limit on ionization timescale (s/cm3) to include.
par4     =  Upper limit on ionization timescale (s/cm3) to include.
par5     =  redshift z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
raymond

An emission spectrum from hot, diffuse gas based on the model calculations of Raymond and Smith (ApJSuppl 35, 419 and additions) including line emissions from several elements. This model interpolates on a grid of spectra for different temperatures. The grid is logarithmically spaced with 80 temperatures ranging from 0.008 to 80 keV.

par1     =  plasma temperature in keV
par2     =  Metal abundances (He fixed at cosmic) The elements included are C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni and their relative abundances are set by the abund command.
par3     =  redshift
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_h dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
redge

Recombination edge emission.


\begin{displaymath}\begin{array}{lcll}
A(E) & = & 0. & {\rm for\ } E < {\tt par1...
...tt par1})/{\tt par2})
& {\rm for\ } E >{\tt par1}
\end{array}\end{displaymath}

par1     =  threshold energy
par2     =  plasma temperature (keV)
K     =  total photons/cm2/s in the line

  
refsch

Exponentially cut-off power-law spectrum reflected from an ionized relativistic accretion disk. In this model, spectrum of pexriv is convolved with a relativistic disk line profile diskline. See Magdziarz & Zdziarski 1995 MNRAS, 273, 837 for details of Compton reflection. See Fabian et al. 1989, MNRAS, 238, 729 for details of the disk line profile.

par1     =  $\Gamma,$ power law photon index, NE prop. to $E^{-\Gamma}$
par2     =  Ec, the cutoff energy in keV (if Ec=0 there is no cutoff)
par3     =  relrefl, reflection scaling factor (1 for isotropic source above disk)
par4     =  redshift, z
par5     =  abundance of elements heavier than He relative to the solar abundances
par6     =  iron abundance relative to the above
par7     =  inclination angle (degrees)
par8     =  disk temperature in K
par9     =  disk ionization parameter, $\xi = 4\pi F_{ion}/n,$ where Fion is the 5 eV - 20 keV irradiating flux, n is the density of the reflector; see Done et al., 1992, ApJ, 395, 275
par10     =  power law index for reflection emissivity; emissivity is $\propto r^{\tt par10}$
par11     =  inner disk radius in units of GM/c2
par12     =  outer disk radius in units of GM/c2
par13     =  internal model accurancy - points of spectrum per energy decade
K     =  photon flux at 1 keV of the cutoff broken power-law only (no reflection) in the observed frame.

  
sedov

Sedov model with separate ion and electron temperatures. This model is slow. par1 provides a measure of the average energy per particle (ions+electrons) and is constant throughout the postshock flow in plane shock models (Borkowski et al., 2001, ApJ, 548, 820). par2 should always be less than par1. If par2 exceeds par1 then their interpretations are switched (ie the larger of par1 and par2 is always the mean temperature). Additional references can be found under the help for the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  mean shock temperature (keV)
par2     =  electron temperature immediately behind the shock front (keV).
par3     =  Metal abundances (He fixed at cosmic). The elements included are C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni. Abundances are given by the Anders & Grevesse mixture.
par4     =  ionization age (s/cm3) of the remnant (== electron density immediately behind the shock front times age of remnant)
par5     =  redshift z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
smaug

This model performs an analytical deprojection of an extended, optically-thin and spherically-symmetric source. A thorough description of the model is given in Pizzolato et al. (ApJ 592, 62, 2003). In this model the 3D distributions of hydrogen, metals and temperature throughout the source are given specific functional forms dependent on a number of parameters, whose values are determined by the fitting procedure. The user has to extract the spectra in annular sectors, concentric about the emission peak. The inner boundary (in arcmin), the outer by the fitting procedure. The user has to extract the spectra in annular sectors, concentric about the emission peak. The inner boundary (in arcmin), the outer boundary (also in arcmin), and the width (in degrees) of each annular sector are specified (respectively) by the three additional keywords XFLT0001, XFLT0002, and XFLT0003, to be added to the spectrum extension in each input file (e.g. with the ftool FKEYPAR). Some parameters of smaug define the redshift and other options (see below). The other, 'relevant' ones define the 3D distributions of hydrogen density, temperature and metal abundance, determined by a simultaneous fit of the spectra. Before running smaug it is important to give the command xset forcecalc on. The cosmological parameters can be set using the cosmo command.

par1     =  central temperature [keV]
par2     =  max difference of temperature [keV]
par3     =  exponent of the inner temperature
par4     =  radius of the inner temperature [Mpc]
par5     =  exponent of the middle temperature
par6     =  radius of the middle temperature [Mpc]
par7     =  exponent of the outer temperature
par8     =  radius of the outer temperature [Mpc]
par9     =  central hydrogen density [cm**-3]
par10     =  fraction of nH.cc relative to the 1st beta component
par11     =  exponent of the first beta component
par12     =  radius of the 1st beta component [Mpc]
par13     =  exponent of the 2nd beta component
par14     =  radius of the 2nd beta component [Mpc]
par15     =  central metallicity [solar units]
par16     =  exponent of the metal distribution
par17     =  radius of the metal distribution [Mpc]
par18     =  redshift of the source
par19     =  number of mesh-points of the dem summation grid
par20     =  cutoff radius for the calculation [Mpc]
par21     =  mode of spectral evaluation: 0 = calculate, 1 = interpolate, 2 = APEC interpolate
par22     =  type of plasma emission code, 1 = Raymond-Smith, 2 = Mekal, 3 = Meka, 4 = APEC
K     =  model normalisation (nH.cc squared [cm**-6] )

Note that if the interactive chattiness level in XSPEC is set to a value > 10, smaug also prints on screen the following quantities:

H0     =  Hubble constant [km/s/Mpc]
q0     =  deceleration parameter
L0     =  cosmological constant
DA     =  source angular distance [Mpc]
DSET     =  dataset no. to which the quantities listed below are
IN     =  inner rim of the projected annular sector [Mpc]
OUT     =  outer rim of the projected annular sector [Mpc]
WID     =  width of the projected annular sector [deg]
EVOL     =  emitting volume within the integration radius cutoff [Mpc3]
EINT     =  emission integral within the integration radius cutoff [ Mpc3 cm-6]. If nH.cc is frozen to 1, the actual EI is obtaned by multiplying this figure by the square root of the model normalisation

  
srcut

The synchrotron spectrum from an exponentially cut off power-law distribution of electrons in a homogeneous magnetic field. This spectrum is itself a power-law at lower energies, with a slow rolloff (slower than exponential) above some rolloff frequency. Though more realistic than a power-law, it is highly oversimplified, but does give the maximally curved physically plausible spectrum and can be used to set limits on maximum accelerated-electron energies even in supernova remnants whose X-rays are thermal. See Reynolds, S.P. & Keohane, J.W. 1999, ApJ, 525, 368 (but note that the numerical coefficient of equation (2) in that paper is incorrect: it should be 1.6e16) and Reynolds, S.P., 1998 ApJ 493, 357. The radio spectral index and flux can be obtained from Green's Catalogue at http://www.mrao.cam.ac.uk/surveys/snrs/ for galactic SNRs.

par1     =  alpha: radio spectral index
par2     =  break Hz: the characteristic (not peak) frequency radiated by electrons with the e-folding energy Em of the exponential cutoff. In cgs units, break = $6.28\times10^{18} E_m^2 B$. It is also approximately the frequency at which the flux has dropped by a factor of about 4 below the straight It is also approximately the frequency at which the flux has dropped by a factor of about 4 below the straight power-law extrapolation from radio frequencies.
K     =  1 GHz flux (Jy)

  
sresc

The synchrotron spectrum from an electron distribution limited by particle escape above some energy. The electrons are shock-accelerated in a Sedov blast wave encountering a constant-density medium containing a uniform magnetic field. The model includes variations in electron acceleration efficiency with shock obliquity, and post-shock radiative and adiabatic losses, as described in Reynolds, S.P., ApJ 493, 357 1998. This is a highly specific, detailed model for a fairly narrow set of conditions. See also Reynolds, S.P., ApJL 459, L13 1996. Note that the radio spectral index and flux can be obtained from Green's Catalogue at http://www.mrao.cam.ac.uk/surveys/snrs/ for galactic SNRs.

par1     =  alpha: radio spectral index (flux proportional to frequency $f^{-\alpha}$)
par2     =  break Hz: approximately the frequency at which the flux has dropped by a factor of 6 below a straight powerlaw extrapolation from radio frequencies. This frequency is 5.3 times the peak frequency radiated by electrons with energy Em3 in a magnetic field of 4 B1, in the notation of Reynolds (1998), Eq. (19).
K     =  1 GHz flux (Jy)

  
step

A step function convolved with a gaussian.


\begin{displaymath}N(E) = {\tt K}(1 - {\rm erf}((E-{\tt par1})/\sqrt(2)/{\tt par2}))/ 2
\end{displaymath}

par1     =  start energy (keV)
par2     =  gaussian sigma (keV)
K     =  step amplitude

  
vapec

An emission spectrum from collisionally-ionized diffuse gas calculated using the APEC code v1.3.1. More information can be found at http://hea-www.harvard.edu/APEC/ which should be consulted by anyone running this model. By default this model reads atomic physics data from the files apec_v1.3.1_coco.fits and apec_v1.3.1_line.fits in the spectral/xspec/manager file. Different files can be specified by using the command xset set APECROOT. There are three options. APECROOT can be set to a version number (eg 1.2.0). In this case the value of APECROOT will be used to replace 1.3.1 in the name of the standard files and the resulting files will be assumed to be in the spectral/xspec/manager directory. Alternatively, a filename root (eg apec_v1.2.0) can be given. This root will be used as a prefix for the _coco.fits and _line.fits in the manager directory. Finally, if neither of these work then the model will assume that the APECROOT value gives the complete directory path e.g. XSPEC> xset APECROOT /foo/bar/apec_v1.2.0 will use /foo/bar/apec_v1.2.0_coco.fits and /foo/bar/apec_v1.2.0_line.fits as input files.

par1     =  plasma temperature in keV
par2-- par14     =  Abundances for He, C, N, O, Ne, Mg, Al, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command)
par15     =  redshift, z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
vbremss

A thermal bremsstrahlung spectrum with variable He/H. Based on the Kellogg, Baldwin & Koch polynomial (ApJ 199, 299) fits to the Karzas & Latter (ApJSuppl 6, 167) numerical values. A routine from Kurucz (priv.comm.) is used for low temperatures.

par1     =  plasma temperature (keV)
par2     =  n(He)/n(H) (note that the Solar ratio is 0.085)
K     =  $(3.02\times 10^{-15} / (4 \pi D^2)) \int n_e n_I dV$, where D is the distance to the source (cm) and ne, nI are the electron and ion densities (cm-3)

  
vequil

Ionization equilibrium collisional plasma model. This is the equilibrium version of Kazik Borkowski's NEI models. The references for this model can be found under the description of the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  plasma temperature in keV
par2-- par13     =  Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (given by the Anders & Grevesse mixture)
par14     =  redshift, z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
vgnei

Non-equilibrium ionization collisional plasma model. This is a generalization of the nei model where the temperature is allowed to have been different in the past ie the ionization timescale averaged temperature is not necessarily equal to the current temperature. For example, in a standard Sedov model with equal electron and ion temperatures, the ionization timescale averaged temperature is always higher than the current temperature for each fluid element. The references for this model can be found under the description of the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  plasma temperature in keV
par2     =  H density in cm-3
par3-- par14     =  Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (given by the Anders & Grevesse mixture)
par15     =  Ionization timescale in units of s/cm-3
par16     =  Ionization timescale averaged plasma temperature in keV.
par17     =  redshift, z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
vmeka

An emission spectrum from hot diffuse gas based on the model calculations of Mewe and Gronenschild (as amended by Kaastra - for references see the section on the meka model). The model includes line emissions from several elements. Abundances are the number of nuclei per Hydrogen nucleus relative to the Solar abundances set by the abund command.

par1     =  plasma temperature in keV
par2     =  hydrogen density in cm-3
par3-- par16     =  Abundances for He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command)
par17     =  redshift
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_h dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
vmekal

An emission spectrum from hot diffuse gas based on the model calculations of Mewe and Kaastra with Fe L calculations by Liedahl (for references see the section on the mekal model). The model includes line emissions from several elements. Abundances are the number of nuclei per Hydrogen nucleus relative to the Solar abundances set by the abund command. The switch parameter determines whether the mekal code will be run to calculate the model spectrum for each temperature or whether the model spectrum will be interpolated from a pre-calculated table. The former is slower but more accurate.

par1     =  plasma temperature in keV
par2     =  hydrogen density in cm-3
par3-- par16     =  Abundances for He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command)
par17     =  redshift
par18     =  0 $\Rightarrow$ calculate, 1 $\Rightarrow$ interpolate
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_h dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
vmcflow

A cooling flow model after Mushotzky & Szymkowiak (``Cooling Flows in Clusters and Galaxies'' ed. Fabian, 1988). This one uses the vmekal model for the individual temperature components, but is otherwise identical to mkcflow. Abundances are relative to Solar as set by the abund command. The switch parameter determines whether the mekal code will be run to calculate the model spectrum for each temperature or whether the model spectrum will be interpolated from a pre-calculated table. The former is slower but more accurate. There are two versions of this model available. xset cflow_version 1 gives the original (11.2.0 and earlier) version which has an error in the calculation of the emission measure distribution at the ends of the temperature range. The default is xset cflow_version 2 which uses a number of emission measure steps that can be set by xset cflow_ntemps <number>

par1     =  low temperature (keV)
par2     =  high temperature (keV)
par3- par16     =  Abundances for He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command)
par17     =  redshift
par18     =  0 $\Rightarrow$ calculate, 1 $\Rightarrow$ interpolate
K     =  Mass accretion rate (solar mass/yr)

  
vnei

Non-equilibrium ionization collisional plasma model. This assumes a constant temperature and single ionization parameter. It provides a characterisation of the spectrum but is not a physical model. The references for this model can be found under the description of the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  plasma temperature in keV
par2     =  H density in cm-3
par3-- par14     =  Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (given by the Anders & Grevesse mixture)
par15     =  Ionization timescale in units of s/cm-3
par16     =  redshift, z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
vnpshock

Plane-parallel shock plasma model with separate ion and electron temperatures. This model is slow. par1 provides a measure of the average energy per particle (ions+electrons) and is constant throughout the postshock flow in plane shock models (Borkowski et al., 2001, ApJ, 548, 820). par2 should always be less than par1. If par2 exceeds par1 then their interpretations are switched (ie the larger of par1 and par2 is always the mean temperature). Additional references can be found under the help for the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  mean shock temperature in keV
par2     =  electron temperature immediately behind the shock front (keV)
par3     =  H density in cm-3
par4-- par15     =  Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (given by the Anders & Grevesse mixture)
par16     =  Lower limit on ionization timescales (s/cm3) to include
par17     =  Upper limit on ionization timescales (s/cm3) to include
par18     =  redshift, z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
vpshock

Constant temperature, plane-parallel shock plasma model. The references for this model can be found under the description of the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  plasma temperature in keV
par2     =  H density in cm-3
par3-- par14     =  Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (given by the Anders & Grevesse mixture)
par15     =  Lower limit on ionization timescales (s/cm3) to include
par16     =  Upper limit on ionization timescales (s/cm3) to include
par17     =  redshift, z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
vraymond

A version of the XSPEC model raymond, with independent variables for all abundances and for the continuum. This model interpolates on a grid of spectra for different temperatures. The grid is logarithmically spaced with 80 temperatures ranging from 0.008 to 80 keV. Abundances are the number of nuclei per Hydrogen nucleus relative to the Solar abundances as set by the abund command.

par1     =  plasma temperature (keV)
par2-- par13     =  Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (defined by the abund command)
par14     =  redshift
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_h dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
vsedov

Sedov model with separate ion and electron temperatures. This model is slow. par1 provides a measure of the average energy per particle (ions+electrons) and is constant throughout the postshock flow in plane shock models (Borkowski et al., 2001, ApJ, 548, 820). par2 should always be less than par1. If par2 exceeds par1 then their interpretations are switched (ie the larger of par1 and par2 is always the mean temperature). Additional references can be found under the help for the equil model. Several versions are available. To switch between them use the xset neivers command. xset neivers 1.0 gives the version from xspec v11.1, xset neivers 1.1 uses updated calculations of ionization fractions using dielectronic recombination rates from Mazzotta et al (1988), and xset neivers 2.0 uses the same ionization fractions as 1.1 but uses APED to calculate the resulting spectrum. Note that versions 1.x have no emission from Ar. The default is version 1.1.

par1     =  mean shock temperature in keV
par2     =  electron temperature immediately behind the shock front (keV)
par3     =  H density in cm-3
par4-- par15     =  Abundances for He, C, N, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni wrt Solar (given by the Anders & Grevesse mixture)
par16     =  ionization age (s/cm3) of the remnant (== electron density immediately behind the shock front times age of remnant)
par17     =  redshift, z
K     =  $(10^{-14} / (4 \pi (D_A (1+z))^2)) \int n_e n_H dV$, where DA is the angular size distance to the source (cm), ne and nH are the electron and H densities (cm-3)

  
zbbody

A redshifted blackbody spectrum.


\begin{displaymath}A(E) = {\tt K}\ 8.0525 (E(1+{\tt par2}))^2 / \\
(({\tt par1})^4 (\exp (E(1+{\tt par2})/{\tt par1})-1)) \\
\end{displaymath}

where :

par1     =  temperature kT in keV
par2     =  redshift
K     =  L39/D102, where L39 is the source luminosity in units of 1039 ergs/sec and D10 is the angular size distance to the source in units of 10 kpc

  
zbremss

A redshifted thermal bremsstrahlung spectrum based on the Kellogg, Baldwin & Koch (ApJ 199, 299) polynomial fits to the Karzas & Latter (ApJSuppl 6, 167) numerical values. A routine from Kurucz (priv.comm.) is used for low temperatures.

par1     =  plasma temperature in keV
par2     =  redshift
K     =  $(3.02\times 10^{-15} / (4 \pi D^2)) \int n_e n_I dV$, where D is the distance to the source (cm) and ne, nI are the electron and ion densities (cm-3)

  
zedge

A redshifted absorption edge.


\begin{displaymath}\begin{array}{lcll}
M(E) & = & 1 & {\rm for\ } E < {\tt par1}...
...3})/{\tt par1})^3)) & {\rm for\ } E > {\tt par1}\\
\end{array}\end{displaymath}

where :

par1     =  threshold energy
par2     =  absorption depth at threshold
par3     =  redshift

  
zgauss

A redshifted simple gaussian line profile. If the width is $\leq 0$, then it is treated as a delta function.


\begin{displaymath}A(E) = {\tt K}(1./(\sqrt (2\pi {\tt par2}^2))
\exp(-.5 ((E (1+{\tt par3})-{\tt par1})/{\tt par2})^2))
\end{displaymath}

where :

par1     =  line energy in keV
par2     =  line width (sigma) in keV
par3     =  redshift
K     =  total photons/cm2/s in the line

  
zpowerlw

A simple photon power law.


\begin{displaymath}A(E) = {\tt K}(E (1+{\tt par2})/(1 {\rm keV}))^{(-{\tt par1})}
\end{displaymath}

where :

par1     =  photon index of power law (dimensionless)
par2     =  redshift
K     =  photons/keV/cm2/s at 1 keV


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Next: Multiplicative Model Components A-M Up: XSPEC V11.3 Models Previous: Additive Model Components A-M
Ben Dorman
2003-11-28