Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump

The Red Clump is an overdensity in luminosity on the HR diagram, caused by certain Core-Helium Burning stars with similar core masses, a product of their evolutionary physics. We identify the exact luminosity of the Red Clump using asteroseismology, and then separately using Gaia data, to see how our assumptions about one method lead to us drawing different inferences in the other.

We find that changing asteroseismic temperature scale and/or corrections to scaling relations change the position of the Red Clump significantly, and that the corresponding parallax zero-point offset required to find that same Red Clump luminosity similarly varies significantly. It should be noted that if we assume asteroseismology to be absolute, we do not recover a parallax zero-point offset that agrees with similar work done by Zinn et al. 2018.

Clearly, there is still much to be done!

Transcript

1. @asteronomer ojhall94 Oliver J. Hall Guy Davies, Yvonne Elsworth, Thomas North, Rafael García, Saniya Khan TASC4/KASC11 Aarhus University 12/07/2018 Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump !1
2. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94
3. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 » Disagreement between asteroseismic & Gaia distances in DR1 » Investigated using the Red Clump » ‘seismic parallax’: distance from luminosity from seismic radius Seismic parallax (mas) Apparent K-band mag Davies+17
4. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 » Lindegren+ (Quasars): » Quasars in Kepler field: » Riess+ (Cepheids): » Zinn+ (seismo): ϖzp = − 29μas ϖzp = − 46μas ϖzp = − 53μas ϖzp = − 30μas Arenou +18
5. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 » We aim to investigate the RC magnitude in: » Seismic absolute magnitude » Absolute magnitude from photometry + Gaia » We vary: » Temperature scale » Scaling corrections » Parallax zero-point Arenou +18
6. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 » Data from Yu+ 2018 » Reclassify with Elsworth+ 2017 » K-band photometry from 2MASS » Extinction from Green+ 2018 » BCs from Casagrande & Vandenberg 2014 (& 2018, BCcodes) » And Gaia data via Megan Bedell @ gaia-kepler.fun!
7. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 μ σ Q σo ̂ Mi σ ̂ Mi
8. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 μ σ Q σo Mi ̂ Mi σ ̂ Mi
9. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 » Little more complicated for Gaia… » Two new parameters: » , length scale of distance prior » , parallax zero point » Input photometry, parallax, extinction Adapted from Hawkins+ 17 μ σ Q σo ϖzp L ϖzp
10. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 » Seismic luminosity of the RC is correlated with Teff scale » Choice of scaling-relation correction has non-negligible impact on RC luminosity
11. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 » Used seismic RC magnitude to inform our Gaia model » For different RC magnitudes, the model requires a different zeropoint! μ = − 0.0068ϖzp − 1.952
12. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 » If we trust a parallax zero-point, we can use the RC to calibrate asteroseismology OR » If we trust asteroseismic assumptions completely, we can use the RC to calibrate Gaia
13. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 » If we trust a parallax zero-point, we can use the RC to calibrate asteroseismology OR » If we trust asteroseismic assumptions completely, we can use the RC to calibrate Gaia Slumstrup, P14
14. Testing asteroseismology with Gaia DR2: Luminosity of the Red Clump @asteronomer ojhall94 In summary… » Used hierarchical models to locate the RC in seismic & Gaia data » Choice of seismic temperature scale & scaling relations have strong impact on position of RC » Position of RC has strong correlation with parallax zero-point » To calibrate one, we’ll need a strong constraint on the other!