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The Gothard Observatory Synthetic Stellar Photometry Database

József Kovács, Szabolcs Mészáros, Beáta Harmati, Borbála Cseh, Viola Hegedűs, Gyula M. Szabó, László Szigeti, Blanka Világos, Aliz Derekas

TL;DR

This work introduces the Gothard Observatory Synthetic Stellar Photometry Database, a BOSZ-based resource providing synthetic magnitudes for 752 filters and bolometric corrections across a wide stellar-parameter grid ($T_ ext{eff}=2800$–$16000$ K, $ ext{log} ext{g}=-0.5$ to 5.5, [M/H] = −2.5 to 0.75, [$ ext{α}$/M] = −0.25 to 0.5, [C/M] = −0.75 to 0.5, $A_V$ up to 3.1). Magnitudes are computed in the Vega system via the species package, using high-resolution ($R=50{,}000$) BOSZ spectra and reddening applied directly to spectra with the CCM89 law. The grid comprises 628{,}620 spectra across 50 nm to 32 μm, with 0.0–3.1 mag extinction and 50 K Teff steps, enabling precise tracking of abundance effects (notably [C/M]) on BCs and luminosities. Validation against nearly two million Gaia–2MASS color combinations shows good agreement, while comparisons with Gaia DR3 BCs reveal improvements from updated molecular opacities and carbon treatment. Applying the new BCs to about 177{,}728 APOGEE targets yields refined luminosities and demonstrates that neglecting carbon or α-enhancements can introduce up to about 1% errors in luminosities. Overall, the database provides a powerful tool for improving fundamental stellar parameter determinations in current and upcoming surveys such as Gaia, LSST, and the Roman Space Telescope.

Abstract

Context. In order to determine stellar luminosities and radii, it is necessary to know the total bolometric fluxes emitted by the stars, or equivalently the bolometric corrections (BCs) as accurately as possible. Aims. The aim of this paper is to present and describe a new database of synthetic stellar magnitudes and bolometric corrections for 752 filters from 78 ground- and space-based instruments calculated using the most recent version of the BOSZ synthetic stellar spectral library. Methods. From the entire grid of the BOSZ theoretical spectra, our synthetic magnitudes in the Vega magnitude system were determined using the corresponding routines of the Python package species. Results. The database spans effective temperatures from 2800 to 16000~K, log g from $-0.5$ to 5.5, metallicities from $-2.5$ to 0.75, [$α$/M] from $-0.25$ to 0.5, [C/M] from $-0.75$ to 0.5, and reddening up to $A_V$ = 3.1 mag. Using high-resolution (R = 50000) synthetic spectra allowed us to precisely track the effect of abundances on the bolometric corrections and luminosity of stars. Conclusions. By applying the new bolometric corrections (BCs) to 192\,000 APOGEE stars we calculated luminosities, and also demonstrated that neglecting carbon can introduce up to $\pm$0.2\% errors in luminosity. The new Gothard Observatory Synthetic Stellar Photometry Database may enable more accurate fundamental parameter determinations for large stellar samples using a vast amount of past, present, and upcoming surveys, such as Gaia, LSST, and the Roman Space Telescope.

The Gothard Observatory Synthetic Stellar Photometry Database

TL;DR

This work introduces the Gothard Observatory Synthetic Stellar Photometry Database, a BOSZ-based resource providing synthetic magnitudes for 752 filters and bolometric corrections across a wide stellar-parameter grid (– K, to 5.5, [M/H] = −2.5 to 0.75, [/M] = −0.25 to 0.5, [C/M] = −0.75 to 0.5, up to 3.1). Magnitudes are computed in the Vega system via the species package, using high-resolution () BOSZ spectra and reddening applied directly to spectra with the CCM89 law. The grid comprises 628{,}620 spectra across 50 nm to 32 μm, with 0.0–3.1 mag extinction and 50 K Teff steps, enabling precise tracking of abundance effects (notably [C/M]) on BCs and luminosities. Validation against nearly two million Gaia–2MASS color combinations shows good agreement, while comparisons with Gaia DR3 BCs reveal improvements from updated molecular opacities and carbon treatment. Applying the new BCs to about 177{,}728 APOGEE targets yields refined luminosities and demonstrates that neglecting carbon or α-enhancements can introduce up to about 1% errors in luminosities. Overall, the database provides a powerful tool for improving fundamental stellar parameter determinations in current and upcoming surveys such as Gaia, LSST, and the Roman Space Telescope.

Abstract

Context. In order to determine stellar luminosities and radii, it is necessary to know the total bolometric fluxes emitted by the stars, or equivalently the bolometric corrections (BCs) as accurately as possible. Aims. The aim of this paper is to present and describe a new database of synthetic stellar magnitudes and bolometric corrections for 752 filters from 78 ground- and space-based instruments calculated using the most recent version of the BOSZ synthetic stellar spectral library. Methods. From the entire grid of the BOSZ theoretical spectra, our synthetic magnitudes in the Vega magnitude system were determined using the corresponding routines of the Python package species. Results. The database spans effective temperatures from 2800 to 16000~K, log g from to 5.5, metallicities from to 0.75, [/M] from to 0.5, [C/M] from to 0.5, and reddening up to = 3.1 mag. Using high-resolution (R = 50000) synthetic spectra allowed us to precisely track the effect of abundances on the bolometric corrections and luminosity of stars. Conclusions. By applying the new bolometric corrections (BCs) to 192\,000 APOGEE stars we calculated luminosities, and also demonstrated that neglecting carbon can introduce up to 0.2\% errors in luminosity. The new Gothard Observatory Synthetic Stellar Photometry Database may enable more accurate fundamental parameter determinations for large stellar samples using a vast amount of past, present, and upcoming surveys, such as Gaia, LSST, and the Roman Space Telescope.

Paper Structure

This paper contains 16 sections, 14 equations, 6 figures, 3 tables.

Table of Contents

  1. Introduction
  2. Calculation methods
  3. From fluxes to magnitudes
  4. Bolometric corrections
  5. Parameters of the new BC database
  6. Fixes made in the 2024 version of the BOSZ grid
  7. Interstellar reddening
  8. Program package species
  9. The Scope of the Database
  10. Validation of color-color relationships
  11. Effect of grid parameters on the bolometric correction
  12. Comparing Gaia DR3 G bolometric corrections with literature
  13. APOGEE luminosities
  14. Our APOGEE sample
  15. The effect of carbon on bolometric correction and luminosity
  16. ...and 1 more sections

Figures (6)

  • Figure 1: Examples of how bolometric corrections in selected HST, LSST, Gaia, Roman, 2MASS and JWST filters depend on effective temperature. Filters are shown in the order of increasing central wavelength. The bolometric corrections are color coded by reddening.
  • Figure 2: The J$-$K$_{\rm s}$ vs. G$_{\rm BP}-$G$_{\rm RP}$ color-color diagram. The contoured area is stars observed by both Gaia and 2MASS, see Section \ref{['validate']} for more detail. Each panel is color-coded by a different parameter indicated in the panels themselves.
  • Figure 3: Effect of various parameters on Gaia DR3 $\mathrm{BC}_G$. The fixed parameters are listed in the panels.
  • Figure 4: Difference between the $\mathrm{BC}_G$ from this paper and from Gaia DR3 as a function of $T_\mathrm{eff}$. The left panel shows all commom $T_\mathrm{eff}$, $\log g$, and [M/H] combinations, while in the right panel the $\log g$ was set to 4.5 to reveal the metallicity dependent differences on the main sequence. [$\alpha$/M] = [C/M] = 0.0 in both cases.
  • Figure 5: The HRD of our selected APOGEE targets using the new Gaia DR3 $\mathrm{BC}_G$ values presented in this paper.
  • ...and 1 more figures