Measuring stellar inclinations is fundamental to understand planetary formation and dynamics as well as physical conditions during star formation. Oscillation spectra of red giant stars exhibit mixed modes that have both a gravity component from the radiative interior and a pressure component from the convective envelope. Gravity-dominated (g-m) mixed modes split by rotation are well separated inside frequency spectra, making possible accurate measurements of stellar inclinations. This work aims at developing an automated and general approach to measure stellar inclinations, that can be applied to any solar-type pulsator for which oscillation modes are identified, and at validating it using red giant branch stars observed by Kepler. We use the mean height-to-background ratio of dipole mixed modes with different azimuthal orders to measure stellar inclinations. The underlying statistical distribution of inclinations is recovered in an unbiased way using a probability density function for the stellar inclination angle. We derive stellar inclination measurements for 1139 stars on the red giant branch, for which Gehan et al. (2018) have identified the azimuthal order of dipole g-m mixed modes. Raw measured inclinations exhibit strong deviation with respect to isotropy which is expected for random inclinations over the sky. When taking uncertainties into account, the reconstructed distribution of inclinations actually follows the expected isotropic distribution of the rotational axis. This work highlights the biases that affect inclination measurements and provides the way to infer their underlying statistical distribution. When the star is seen either pole-on or equator-on, measurements are challenging and result in a biased distribution. Correcting biases that appear at the low- and high inclination regimes allows us to recover the underlying inclination distribution.
Modeling Multi-Wavelength Stellar Astrometry. II. Determining Absolute Inclinations, Gravity Darkening Coefficients, and Spot Parameters of Single Stars with SIM Lite
Lithium abundances in red giants of M4: evidence for asymptotic giant branch star pollution in globular clusters?
在球状星团（GC）巨人的Li和质子捕获元素丰度的测定，使我们能够限制在GC中的多个人口情景的几个关键问题，从形成和早期演化，污染和稀释机制。在这封信中，我们提出了我们的结果，对大样本的巨人在中间金属丰度GC NGC 6121（M4），其中钠和O已经确定了马里诺等人。分析的恒星都低于和高于红巨星分支凸点光度。我们发现第一代和第二代恒星具有相同的Li含量，这表明Li生产一定发生过。这是一个强有力的观测证据，支持渐近巨星分支星是GC污染者的假设。
Population II Distance Indicators: RR Lyrae Variables, Tip of the Red Giant Branch (TRGB) Stars and J-Branch Asymptotic Giant Branch (JAGB/Carbon) Stars
The Gradients in the 47 Tuc Red Giant Branch Bump and Horizontal Branch are Consistent With a Centrally-Concentrated, Helium-Enriched Second Stellar Generation
