Rotational broadening of exoplanet spectra in arbitrarily oriented systems: Application to reflected light

@misc{vaughan2026rotational,
  title = {{Rotational broadening of exoplanet spectra in arbitrarily oriented systems: Application to reflected light}},
  author = {Sophia R. Vaughan and Laura Kreidberg},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.05619},
  eprint = {2609.05619},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.05619},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Rotational broadening of exoplanet spectra in arbitrarily oriented systems: Application to reflected light
AU  - Sophia R. Vaughan
AU  - Laura Kreidberg
PY  - 2026
DA  - 2026/09/04
PB  - arXiv
DO  - 10.48550/arxiv.2609.05619
UR  - https://arxiv.org/abs/2609.05619
AB  - Exoplanet reflection spectra contain a wealth of information, which we are now beginning to access. At a high spectral resolution, the rotation of both the star and the planet affects the shape of the reflected spectral lines. This effect must be accounted for in high-resolution analyses and could be used to measure the orbital alignment of systems. In this work, we derive the rotational broadening kernels for arbitrarily aligned systems, both for the stellar spectrum viewed by the planet and for the reflected component of the planet's spectrum. We then determine the relation between the parameters of the kernels and the standard orbital parameters of an exoplanet system. Finally, we show examples of these kernels, compare them with previous models, and investigate the limitations imposed by our assumptions. We find that the difference in the rotational broadening of a non-aligned system relative to the broadening expected from a prograde aligned orbit can be of the order of 50 km s^−1. We also highlight how the equations and kernels presented in this work could be modified for other uses, such as thermal emission spectra.
ER  -