2.10. SPEX evaluation of APEC model

By: Liyi Gu

It is possible to calculate APEC without calling XSPEC. This could be done with the through atbl (Atbl: Additive table model). This would allow user to compare APEC and CIE (Cie: collisional ionisation equilibrium model) without switching softwares.

2.10.1. Download APEC files

The APEC package containing the continuum coco file and the line file are available at AtomDB.

2.10.2. Atbl for APEC

The APEC files can be evaluated through:

SPEX> com atbl
SPEX> par 1 1 file av /directory/to/apec/apec_v3.1.3_coco.fits
SPEX> calc
SPEX> com atbl
SPEX> par 1 2 file av /directory/to/apec/apec_v3.1.3_line.fits
SPEX> calc
SPEX> par 1 2 norm:vrms cou 1 1 norm:vrms

Essentially, two atbl components are defined: one for the APEC continuum and one for the emission lines. In this example, all parameters of the continuum and line components are coupled; however, they can also be calculated separately if needed.

The SPEX evaluation of APEC may differ slightly from the XSPEC implementation due to differences in the interpolation algorithms. In addition, the normalization follows the SPEX convention. This means that a SPEX/APEC model, at its default distance and with a normalization of 4\pi, corresponds to an XSPEC/APEC model evaluated at zero redshift.

It is possible to set the abundance standard using the abund (Abundance: standard abundances) command.

Note

The current atbl cannot be used to read the APEC-NEI fits table.

Recommended citation: Smith et al. (2001) and Foster et al. (2012)