Bolometric corrections of stellar oscillation mode amplitudes as observed by the PLATO mission. I. Planck-spectrum estimates

Abstract

We derive bolometric correction functions for oscillation mode amplitudes observed by the different cameras of the ESA PLATO mission. Such corrections between bolometric (full light) and mission instrument-specific amplitudes enable comparisons to theoretical expectations and amplitude conversion between different photometric missions, which is essential for proper detectability yields and target selection. Bolometric correction functions were calculated assuming a Planck function approximation for the stellar spectral flux distribution. The calculations follow the procedures applied in earlier analyses for the NASA Kepler and TESS missions. We derived power-law and polynomial parametrisations of the bolometric corrections with $T_{\rm eff}$. We find that on average, oscillation mode amplitudes from PLATO's normal cameras (N-CAMs) are expected to be ~6.7% lower compared to Kepler, and ~12.5% higher compared to TESS. A significant average amplitude ratio of ~25% is expected for amplitudes measured using the blue PLATO fast camera (F-CAM) compared to TESS. We find that observations of bright solar-like oscillators, especially with PLATO's F-CAMs, would provide an important test of the predicted corrections.

Figures (4)

• Figure 1: Left: Spectral response functions, $\mathcal{S}_{\lambda}$, for the PLATO (Sect. \ref{['sec:bp']}), KeplerVCleve, TESS 2014SPIE.9143E..20R (normalised to a maximum of Kepler), and CoRoT 2009AA...506..411A missions as a function of wavelength $\lambda$. The shaded regions show blackbody spectra with temperatures of $7000, 6000, 5000$, and $4000$ K (normalised to a maximum of $0.8$ for the hottest, or bluest, curve). Right: Spectral response functions for the PLATO N- and F-CAMs. The vertical dashed lines show the nominal passband limits of the blue and red F-CAMs, with the shaded $\pm10$ nm regions indicating the potential variation in these from the incident angle.
• Figure 2: Left: QE as a function of wavelength used for computing $\mathcal{S}_{\lambda}$ (given by the product of QE and the OT in the right panel). The markers indicate the available averages from tests of N-CAM flight model CCDs, while the shaded region indicates the associated standard deviation. The full or dashed black line shows the adopted interpolation, where the dashed part indicates the wavelength range outside the PLATO passbands. The vertical dashed lines show the nominal passband limits of the blue and red F-CAMs, with the shaded $\pm10$ nm regions indicating the potential variation in these from the incident angle, with the upper red filter limit fixed at $1000$ nm by the detector response. Right: OT for the N-CAM (black) and F-CAMs (blue and red) as a function of wavelength. The markers indicate available measurement points. The F-CAM passband boundaries are marked as in the left panel. The full lines show a simple linear interpolation of the measurement points.
• Figure 3: Values for the bolometric correction $c_{\rm BP-bol}$ (Eq. \ref{['eq1']}) based on Planck spectra, as a function of $T_{\rm eff}$. Different lines and markers refer to different photometric missions or filters for the PLATO mission (see legend).
• Figure 4: Amplitude ratios between different missions, and/or the different filters of the PLATO mission, as a function of $T_{\rm eff}$ (see legend). The amplitude change is shown as both a percentage deviation (left axis) and as a fractional ratio (right axis). The horizontal dashed line indicates equal amplitudes, while the vertical dotted lines indicate the solar $T_{\rm eff}$.