Introduction

TESS-Gaia Light Curve (TGLC) is a dataset of TESS full-frame image light curves publicly available via the MAST portal. It is fitted with effective PSF and decontaminated with Gaia DR3 and achieved percent-level photometric precision down to 16th TESS magnitude! It unlocks astrophysics to a vast number of dim stars below 12th TESS magnitude. A package called tglc is pip-installable for customized light curve fits.

Usage

Historical products contain four main flux columns. TGLC 0.8.0 also writes aperture_flux_raw and psf_flux_raw, giving six flux columns. Check the product’s processing version and available columns before choosing:

• aperture_flux_raw is the decontaminated 3 by 3 pixel sum; psf_flux_raw is the fitted target amplitude. Both retain signed values in electrons/second before catalog-based additive offsets and detrending. They are extracted photometry, not unprocessed detector measurements.

• aperture_flux and psf_flux are not detrended, but do include catalog-based additive offsets. Aperture flux also includes the modeled aperture-fraction correction. The headers record the exact relationships: aperture_flux = (aperture_flux_raw - LOC_BG) / PORTION and psf_flux = psf_flux_raw - PSF_BG.

• cal_aper_flux and cal_psf_flux are normalized and detrended. They are useful for an initial inspection of short-period signals; the default one-day detrending can alter longer stellar variations.

• Compare aperture and PSF results for your target. Transit depths and stellar amplitudes depend on contamination, catalog flux estimates and the modeled aperture fraction; neither flux choice guarantees the correct amplitude. For custom calibration or detrending, start from the raw columns, inspect the offsets and quality flags, and account for remaining contamination. tglc_lc(save_aper=True) also saves the decontaminated 5 by 5 pixel cube for inspecting other apertures, whose flux fractions need their own calibration.

The tutorial shows the syntaxes and differences among these light curves in several examples.

Data Access

There are three data access methods:

• MAST Portal: Easiest for acquiring light curves for a few stars. However, new sectors are updated relatively slowly.

• MAST bulk download: Best for downloading light curves for all stars (<16 TESS magnitude) in a sectors.

• tglc package: Generate customized light curves from available SPOC cutouts; see the workflow and limitations below.

pip install tglc

from pathlib import Path
from tglc.quick_lc import tglc_lc, plot_lc

output = Path("tglc-output")
paths = tglc_lc(
    target=16005254,                 # equivalent to "TIC 16005254"
    local_directory=output,
    first_sector_only=True,          # choose one sector for a first run
    ffi="SPOC",
    saturation_limit=80000.0,         # conservative cutoff in electrons/second
    saturation_dilation=1,
)
print(paths)                         # FITS paths generated during this call
plot_lc(local_directory=output, ffi="SPOC")

python -m pip install -e '.[dev]'
python -m pytest
python -m build
python -m twine check dist/*

Known Problems

• Catalog-based offsets and aperture fractions can change fractional amplitudes. The raw columns and reconstruction headers let users inspect these adjustments; catalog-normalized flux is not independently calibrated absolute photometry.

• The configurable saturation mask protects PSF fits. Its default 80000 e-/s cutoff and one-pixel dilation are approximate, and long bleed trails can extend beyond the mask. Accurate photometry of saturated targets is not established.

• TICA remains experimental. The recommended public workflow uses SPOC inputs. For precise timing, verify the target-versus-cutout reference correction; SPOC timestamps are retained without a second full barycentric correction.

• Installing 0.8.0 does not regenerate existing MAST products. Check their version, flags and flux definitions separately from newly extracted files.

Reference

If you find the TGLC light curves or the tglc package useful in your research, please cite our paper published on the Astronomical Journal.