Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems

By Luca Casagrande, D. VandenBerg. 2014

181 citations recorded by the source corpus.

After a pedagogical introduction to the main concepts of synthetic photometry, colours and bolometric corrections in the Johnson-Cousins, 2MASS, and HST-ACS/WFC3 photometric systems are generated from MARCS synthetic fluxes for various [Fe/H] and [alpha/Fe] combinations, and virtually any value of reddening E(B-V) < 0.7. The successes and failures of model fluxes in reproducing the observed magnitudes are highlighted. Overall, extant synthetic fluxes predict quite realistic broad-band colours and bolometric corrections, especially at optical and longer wavelengths: further improvements of the predictions for the blue and ultraviolet spectral regions await the use of hydrodynamic models where the microturbulent velocity is not treated as a free parameter. We show how the morphology of the colour-magnitude diagram (CMD) changes for different values of [Fe/H] and [alpha/Fe]; in particular, how suitable colour combinations can easily discriminate between red giant branch and lower main sequence populations with different [alpha/Fe], due to the concomitant loops and swings in the CMD. We also provide computer programs to produce tables of synthetic bolometric corrections as well as routines to interpolate in them. These colour-Teff-metallicity relations may be used to convert isochrones for different chemical compositions to various bandpasses assuming observed reddening values, thus bypassing the standard assumption of a constant colour excess for stars of different spectral type. We also show how such an assumption can lead to significant systematic errors. The MARCS transformations presented in this study promise to provide important constraints on our understanding of the multiple stellar populations found in globular clusters (e.g., the colours of lower main sequence stars are predicted to depend strongly on [alpha/Fe]) and of those located towards/in the Galactic bulge.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/948f84517ac8bee73421022a27ee075ae222287c

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

1. D. Huber
2. D. Charbonneau
3. E. Gaidos
4. Jon Fortney
5. J. Winn
6. A. Mann
7. Sara Seager
8. E. Petigura

Citations in the corpus

• PHYSICS OF ECLIPSING BINARIES. II. TOWARD THE INCREASED MODEL FIDELITY (2016, unknown): “This version is more appropriate for observations where counts are not calibrated (including instrumental and differential photometry, including Kepler data) and passbands are wide (Bessell 2005; Bessell & Murphy 2012; Casagrande & VandenBerg 2014; Brown et al. 2016).”
• The GALAH Survey: Second Data Release (2018, methodology): “For the absolute bolometric magnitude Mbol, bolometric corrections (BC) from Casagrande & VandenBerg (2014) are applied to the 2MASS K magnitude.”
• The Revised TESS Input Catalog and Candidate Target List (2019, methodology): “…in the TIC is similar to the Sun, we used a synthetic solar-like spectrum as the source (Teff = 5800 K, log g=4.5, [Fe/H]=0.0, the closest PHOENIX model spectrum to the Sun) to compute the effective wavelengths for the various passbands following Equation (18) of Casagrande & VandenBerg (2014).”
• The California-Kepler Survey. VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap (2018, methodology): “Huber et al. (2017) assessed these errors by comparing stellar radii derived from the MIST grids to those derived using the BASTA grids (Casagrande & VandenBerg 2014) and estimated 0.03mag errors.”
• An Analysis of the Shapes of Interstellar Extinction Curves. VII. Milky Way Spectrophotometric Optical-through-ultraviolet Extinction and Its R-dependence (2019, methodology): “The synthetic ugriz photometry was performed as described in Casagrande & VandenBerg (2014), with filter profiles from Doi et al. (2010).”
• Asteroseismology and Gaia: Testing Scaling Relations Using 2200 Kepler Stars with TGAS Parallaxes (2017, methodology): “…a second test by comparing distances calculated using the same seismic luminosity and reddening but bolometric corrections calculated from MARCS model atmospheres (Gustafsson et al. 2008) provided by Casagrande & VandenBerg (2014), as implemented in BASTA (see also theleft panel of Figure 2).”
• Confirming chemical clocks: asteroseismic age dissection of the Milky Way disc(s) (2017, methodology): “…method consists of using the surface gravity determined by BASTA and combining it with the reddening value from the KIC catalogue, the grizJHKS magnitudes, and the spectroscopic Teff and [Fe/H] to compute the bolometric correction using the synthetic photometry of Casagrande & Vandenberg (2014).”