OneSpec

Overview

Generally, the ultimate PypeIt spectrum output is a single spectrum per source, fully calibrated and (as desired) with a Telluric correction performed.

The standard way to generate this file is with the pypeit_coadd_1dspec script script.

The naming of this file is user-generated, i.e. it can be anything you wish.

The header of the primary extension includes the core_meta of PypeIt, e.g. RA, DEC, MJD, and configuration parameters of the instrument.

In addition, for echelle spectrograph reductions, the PypeIt output will include the coadded orders for each echelle setup used per spectrum per source, fully calibrated but not yet telluric corrected. See OrderStack for more details.

Inspection

You view the spectrum using the lt_xspec script (pypeit_show_1dspec will not work), which loads the data and launches a GUI from the linetools package. e.g.:

lt_xspec J1217p3905_coadd.fits

Current Data Model

Internally, the spectrum for a single object is held by the OneSpec class.

Here is its datamodel, which is written as an astropy.io.fits.BinTableHDU in the first HDU of the file.

Version: 1.0.2

Obj Key	Obj Type	Array Type	Description
`PYP_SPEC`	str		`PypeIt` spectrograph designation
`ext_mode`	str		Extraction mode (options: BOX, OPT)
`flux`	ndarray	floating	Flux array in units of counts/s or 10^-17 erg/s/cm^2/Ang; see `fluxed`
`fluxed`	bool		Boolean indicating if the spectrum is fluxed.
`ivar`	ndarray	floating	Inverse variance array (matches units of flux)
`mask`	ndarray	integer	Mask array (1=Good,0=Bad)
`obj_model`	ndarray	floating	Object model for tellurics
`sigma`	ndarray	floating	One sigma noise array, equivalent to 1/sqrt(ivar) (matches units of flux)
`spect_meta`	dict		header dict
`telluric`	ndarray	floating	Telluric model
`wave`	ndarray	floating	Wavelength array (angstroms in vacuum), weighted by pixel contributions
`wave_grid_mid`	ndarray	floating	Wavelength (angstroms in vacuum) evaluated at the bin centers of a grid that is uniformly spaced in either lambda or log10-lambda/velocity

All wavelengths are in vacuum and flux units depend on whether Fluxing was performed.