The ReferenceSpectra class represents the spectra of the star being observed. Here is an overview of the class, as well as some of its important attributes and methods:
chemicalc.reference_spectra.ReferenceSpectra
ReferenceSpectra.spectra is a Python dictionary, each entry of which consists of a grid of spectra generated around the stellar labels of the reference star Each spectral grid is a nspectra × npixel numpy.ndarray. The order of spectra in the pre-computed spectral grids is described below <pre-computed_refstars_org>.
Upon initialization, the dictionary consists of only one entry with the key "init" that corresponds to the initial grid of high-resolution (R ∼ 300000) normalized spectra. It is read in from reference_spectra_300000.h5 by default or from ref_spec_file if provided.
With each call to :pyReferenceSpectra.convolve() <chemicalc.reference_spectra.ReferenceSpectra.convolve>, the dictionary is populated with a new grid of spectra that have been convolved and subsampled to match the resolution and wavelength array of the passed :pyInstConfig <chemicalc.instruments.InstConfif> object. The key for the new spectral grid is the name of the instrument configuration, InstConfig.name.
ReferenceSpectra.wavelength is a Python dictionary containing the wavelength array (as a size times n_{text{pixel}} numpy.ndarray) corresponding to spectral grids.
Upon initialization, the dictionary consists of only one entry with the key "init" that corresponds to the wavelength array for the initial high-resolution spectral grid. It is read in from reference_spectra_300000.h5 by default or from ref_spec_file if provided.
With each call to :pyReferenceSpectra.convolve() <chemicalc.reference_spectra.ReferenceSpectra.convolve>, the dictionary is populated with a new entry corresponding to the wavelength array of the passed :pyInstConfig <chemicalc.instruments.InstConfif> object. The key for the new wavelength array is the name of the instrument configuration, InstConfig.name.
ReferenceSpectra.labels is a pandas.DataFrame of shape nlabels × nspectra, containing the stellar labels1 corresponding to each spectrum in the grid. The DataFrame's row names (indices) consist of the stellar labels included. The DataFrame's column names consist of (arbitrary) ID's for the individual spectra in the grid. It is read in from reference_labels.h5 by default or from ref_label_file if provided.
ReferenceSpectra.gradients is initially an empty Python dictionary.
With each call to :pyReferenceSpectra.calc_gradient() <chemicalc.reference_spectra.ReferenceSpectra.calc_gradient>, partial derivatives of the spectrum with respect to each stellar label is calculated for one of the sets of spectral grids. They are added as a new entry in the form of an nlabel × npixel pandas.DataFrame. The key for the new spectral gradient DataFrame is the name of the instrument configuration, InstConfig.name. The DataFrame's row names (indices) consist of the stellar labels included. The DataFrame's column names consist of the wavelength of each pixel.
chemicalc.reference_spectra.ReferenceSpectra.convolve
chemicalc.reference_spectra.ReferenceSpectra.calc_gradient
chemicalc.reference_spectra.ReferenceSpectra.zero_gradients
chemicalc.reference_spectra.ReferenceSpectra.mask_wavelength
chemicalc.reference_spectra.ReferenceSpectra.get_names
chemicalc.reference_spectra.ReferenceSpectra.duplicate
chemicalc.reference_spectra.ReferenceSpectra.reset
The spectral grids for the following Reference Stars have been pre-computed using atlas12 1D-LTE model atmospheres and the synthe radiative transfer code.
Note
See Section 3.2 of Sandford et al. (In Press) for a detailed description of the spectral generation
| Name | MV (Vega) | Teff | vturb (km/s) | log (Z) | [X/H] | α included? | |
|---|---|---|---|---|---|---|---|
| RGB_m0.5 | -0.5 | 4200 | 1.5 | 2.0 | -0.5 | Solar | No |
| RGB_m1.0 | -0.5 | 4530 | 1.7 | 1.9 | -1.0 | Solar | Yes |
| RGB_m1.5 | -0.5 | 4750 | 1.8 | 1.9 | -1.5 | Solar | Yes |
| RGB_m2.0 | -0.5 | 4920 | 1.9 | 1.9 | -2.0 | Solar | Yes |
| RGB_m2.5 | -0.5 | 5050 | 1.9 | 1.9 | -2.5 | Solar | Yes |
| MSTO_m1.5 | +3.5 | 6650 | 4.1 | 1.2 | -1.5 | Solar | Yes |
| TRGB_m1.5 | -2.5 | 4070 | 0.5 | 2.3 | -1.5 | Solar | Yes |
| KGiant | --- | 4800 | 2.5 | 1.7 |
|
Solar | No |
| Ph_k0i_m0.0 | --- | 4500 | 1.0 | 2.2 |
|
Solar | Yes |
| Ph_k0i_m1.0 | --- | 4500 | 1.0 | 2.2 | -1.0 | Solar | Yes |
| Ph_k5iii_m0.0 | --- | 4800 | 1.5 | 2.0 |
|
Solar | Yes |
| Ph_k5iii_m1.0 | --- | 4800 | 1.5 | 2.0 | -1.0 | Solar | Yes |
- The first spectrum in each grid is generated with the stellar labels in the above table.
- The next 2 spectra are generated with Teff offset by ± 50 K.
- The next 2 spectra are generated with
$\\log(g)$ offset by ± 0.1 dex. - The next 2 spectra are generated with vturb offset by ± 0.1 km/s.
- The next 2 spectra are generated with [α/H] offset by ± 0.05 dex (if "Yes" in the "α included?" column above).
- The next 97x2 spectra are generated with [X/H] offset by ± 0.05 dex, where X refers to elements with atomic numbers between 3 (Li) and 99 (Es).
In total, these spectral grids will consist of 203 (201) spectra if the offsets to [α/H] are (not) included.
Some Chem-I-Calc users may wish to use their own spectral grids to calculate the CRLBs for additional reference stars or with alternative spectral models (e.g., with 3D, non-LTE atmospheres). This can be done by calling ReferenceSpectra with the keyword arguments: ref_spec_file and ref_label_file. At present, these files must be in the same format as the default Chem-I-Calc files (reference_spectra_300000.h5 and reference_labels.h5).
Warning
Use of custom spectral grids has not been thoroughly tested. We welcome feedback and code contributions to improve this functionality (see Contributing to Chem-I-Calc <contributing>.)
Footnotes
"Stellar Labels" broadly encompasses both atmospheric parameters (e.g., effective temperature, surface gravity, and microturbulent velocity) and elemental abundances.↩