Output data

When completed there should be the following directories inside the DATA_DIR given.

calib // contains input calibration files required by lbl

(i.e. blaze and wave files depending on instrument
lblreftable // LBL reference tables are added here

log // Log files are stored here

models // Any models downloaded are placed here

plots // Any plots saved to disk are put here

science // input spectra are put here (each in `{OBJECT_SCIENCE}` sub-directories)

lblrdb // LBL RDB files are added here

lblrv // LBL RV files (in `{OBJECT_SCIENCE}_{OBJECT_TEMPLATE}` sub-directories)

are stored here

masks // mask files for each object are placed here

other // Other downloaded files are added here

templates // templates are put here

Radial velocity outputs:

There are two main outputs a .fits file and a .rdb file.

The rdb file is compatible with dace (https://dace.unige.ch/radialVelocities/?)

The fits file contains several extensions:

Primary extension: Empty
Wave, DV, SDV, D2V, SD2V, D3V, SD3V Extension: Images (each 2D with shape number of lines by the number of files)
RDB0 is the reference table (fits bin table format)
RDB is the fits bin table equivalent of the .rdb file
PTABLE is the parameters used in this LBL run (fits bin table format)

Note the .rdb file and RDB extension in the fits file consist of the following columns:

Column

Description

rjd

Reduced Julian date at the time of observation. This corresponds to the Julian date - 2 400 000. Do not confuse with MJD, which is Julian date - 2 400 000.5

vrad, svrad

Radial velocity and corresponding error in m/s. This accounts for the systemic velocity of the object (e.g., Barnard’s star has values aroudn -110 000 m/s). The uncertainty on the systemic velocity is - at best about 30-50 m/s (see discussion in Artigau et al. 2022) but the uncertainties relative to this systemic velocity, which truly matter for pRV work, can be much smaller. This value can be accessed and plotted in DACE.

d2v, sd2v

Projection onto the 2nd derivative of the spectrum in units of m^2/s^2 with corresponding uncertainties. For a Gaussian profile, this can be converted into a change in FWHM.

d3v and sd3v

Projection onto the 3rd derivative of the spectrum in units of m^3/s^3 with corresponding uncertaintines. This is still experimental and shows a strong covariance with vrad. Use with care.

DTEMPXXXX and sDTEMPXXXX

If you provided temperature derivative spectra, this is the temperature change in K with corresponding uncertainties. See Artigau et al. 2024 for details.

local_file_name

Local file name for referencing

dW and sdW

Differential width assuming a FWHM that has been measured with a CCF and corresponding uncertainties. See

Artigau et al. 2022 for the transform between d2v and dW. In units of m/s.

fwhm and sig_fwhm

FWHM (from CCF) plus the change in fwhm as derived from d2v and corresponding uncertainties. In units of m/s. This value can be accessed by DACE.

contrast and sig_contrast

Contrast changes in the spectrum as derived by projecting the zero-th order term on each line. This is analoguous

to a congrast change in a CCF. For each line, as defined in Artigau et al. 2022, we subtract the mean and adjust the

amplitude when doing a dot product against residuals.

vrad_achromatic, vrad_chromatic_slope, svrad_chromatic_slope and svrad_achromatic

Using all lines in the ‘trumpet plot’ (see Figure 3), we perform a linear fit against wavelength. The ‘chromatic_slope’ is the slope in m/s/µm of the fit and provides an activity indicator. We also determine the intercept, but as there is no point at 0 µm, we set the intercept at 0.5 µm (optical default) or 1.6µm (ir default) and provide the value of the fit as well as the corresponding uncertainties as ‘vrad_achromatic’ (units m/s).

CRX and sCRX

Analoguous to vrad_achromatic but following the Zechmeister et al. 2018 definition. Provides a slope of velocity as a function of ln(wavelength) in units of m/s/nepper. The intercept is not returned for this fit.

FILENAME

Input file name

MJD-OBS

Instrument dependent (may not be present for all), keyword used for computing the mjd (used in all)

MJDMID

Instrument dependent (may not be present for all), keyword used for computing the mjd (used in all)

EXPTIME HIERARCH ESO TEL AIRM START

Instrument dependent (may not be present for all), keyword used for testing depencies of vrad with airmass in NIRPS

DATE-OBS

Instrument dependent (may not be present for all), keyword used for computing the mjd (used in all)

BERV

Exact keyword instrument dependent. Used for subtraction of barycentric velocity.

TLPEH2O

Instrument dependent (may not be present for all). Exponent of the water absorption term of the telluric correction in APERO.

TLPEOTR

Instrument dependent (may not be present for all). Exponent of the ‘dry’ absorption term of the telluric correction in APERO.

DPRTYPE

Type of data product in APERO. In pretty much all cases, this would be ‘SCIENCE’, unless you want to document instrument drifts rather than obtain pRV of a science target.

ITE_RV

Number of iterations required for LBL convergence. Large numbers (>10) are not expected for targets with little RV drifts between epochs.

RESET_RV

True/False flag to determine if we had a convergence at all.

SYSTVELO

Systemic velocity used for this star.

WAVETIME

Time of the wavelength solution in APERO. Instrument-dependent.

WAVEFILE

File used for wavelength solution in APERO. Instrument-dependent.

TLPDVH2O

Velocity of the water component of the telluric correction (m/s). This is set to zero (for now) as we had unrealistic velocities that worsened RV solutions.

TLPDVOTR

Velocity of the ‘dry’ component of the telluric correction (m/s). This is set to zero (for now) as we had unrealistic velocities that worsened RV solutions.

CDBWAVE

APERO-internal. Calibration data base wave file. Not present for all instrument

OBJECT

Object name. For APERO reductions, should match the APERO astrometic database.

EXTSNXXX

Extracted signal-to-noise of a given order.

BJD

Barycentric julian date

SHAPE_DX,SHAPE_DY,SHAPE_A,SHAPE_B,SHAPE_C,SHAPE_D

APERO-internals, only present for APERO data reductions. These terms map the affine transform of the frame of interest onto the ‘master’ reference frame. Each image is transform through the transfrom [x,y] = [x_i,y_i]*[[shape_A,shape_B],[shape_C,shape_D]]+[shape_DX, shape_DY]

You do not expect the RV to be impacted by any of these terms, and these are used for error tracking.

CCF_EW

e-width of the CCF of the template spectrum

LBL_VERSION, LBL_VDATE, LBL_PDATE, LBL_SCI_DIR

LBL version, date and science directory. It is better to avoid comparing data analyzed with different LBL version.

vrad_XXX and svrad_XXX

For a number of bands, typically the standard SDSS+MKO bandpasses in the instrument domain, we provide a band-averaged velocity and uncertainy

vrad_XXX_0-2044, vrad_XXX_1532-2556, vrad_XXX_2044-4088

For each bandpass, we provide the band-averaged velocity on the left/center/right of the array. These should be consistent within uncertainties and if they are not, they trace instrumental effects.

vrad_XXXnm and svrad_XXXnm

We slice the domain in bins that are 5% fractional wavelength and provide bin-averaged velocities and corresponding uncertaintines in units of m/s. Some bins may have ‘0’ or ‘nan’ if very few or no valid line is present in the domain.

Opening files

The .rdb files are designed to be opened in DACE Radial velocity interface: https://dace.unige.ch/radialVelocities/

The .fits files can be opened in topcat: https://www.star.bris.ac.uk/~mbt/topcat/ (For the table extensions)

Or in python using astropy

Image extensions

from astropy.io import fits

wave = fits.getdata('lbl_{objname}_{template}.fits', 'WAVE')

dv = fits.getdata('lbl_{objname}_{template}.fits', 'DV')

sdv = fits.getdata('lbl_{objname}_{template}.fits', 'SDV')

print(wave.shape)

>> (N, M) # Where N is the number of input files and M is the number of lines

Table extensions

from astropy.table import Table

rdb = Table.read('lbl_{objname}_{template}.fits', 'RDB')

print(rdb.colnames)

>> ['rjd',

'vrad',

'svrad',

'd2v',

'sd2v',

'd3v',

'sd3v',

'DTEMP3000',

'sDTEMP3000',

'DTEMP3500',

'sDTEMP3500',

'DTEMP4000',

'sDTEMP4000',

'DTEMP4500',

'sDTEMP4500',

'DTEMP5000',

'sDTEMP5000',

'DTEMP5500',

'sDTEMP5500',

'DTEMP6000',

'sDTEMP6000',

'local_file_name',

'plot_date',

'dW',

'sdW',

'fwhm',

'sig_fwhm',

'contrast',

'sig_contrast',

'vrad_achromatic',

'svrad_achromatic',

'vrad_chromatic_slope',

'svrad_chromatic_slope',

'FILENAME',

'MJSTART',

'MJDFWFRD',

'EXPTIME',

'AIRMASS',

'DATE-OBS',

'BERV',

'DPRTYPE',

'TLPEH2O',

'TLPEOTR',

'ITE_RV',

'RESET_RV',

'SYSTVELO',

'INSDRIFT',

'OBJNAME',

'SNR_74',

'CCF_EW',

'LBL_VERSION',

'LBL_VDATE',

'LBL_PDATE',

'LBL_SCI_DIR',

'vrad_i',

'svrad_i',

'vrad_i_0-2018',

'svrad_i_0-2018',

'vrad_i_2018-4036',

'svrad_i_2018-4036',

'vrad_654nm',

'svrad_654nm',

'vrad_669nm',

'svrad_669nm',

'vrad_684nm',

'svrad_684nm',

'vrad_700nm',

'svrad_700nm',

'vrad_716nm',

'svrad_716nm',

'vrad_732nm',

'svrad_732nm',

'vrad_749nm',

'svrad_749nm',

'vrad_766nm',

'svrad_766nm',

'vrad_783nm',

'svrad_783nm',

'vrad_801nm',

'svrad_801nm',

'vrad_819nm',

'svrad_819nm',

'vrad_838nm',

'svrad_838nm',

'vrad_857nm',

'svrad_857nm',

'vrad_876nm',

'svrad_876nm',

'vrad_896nm',

'svrad_896nm']