# High-resolution Emission Spectroscopy of the Ultrahot Jupiter KELT-9b: Little Variation in Day- and Nightside Emission Line Contrasts

**Authors:** Andrew Ridden-Harper, Ernst de Mooij, Ray Jayawardhana, Neale Gibson, Raine Karjalainen, Marie Karjalainen  
**arXiv:** [2304.03248](https://arxiv.org/abs/2304.03248)  
**Date:** 2023-04-06  
**Summary page:** https://www.summarizepaper.com/en/paper/2304.03248v1/

## Key points

- Ultrahot Jupiter KELT-9b has an equilibrium temperature of approximately 4000 K and exhibits absorption by several metal species in its transmission spectrum.
- The authors used the CARMENES spectrograph to observe partial phase curves and search for atomic and molecular lines in its emission spectrum.
- Evidence was found for emission by Si I, Fe I, Mg I and Ca II in the atmosphere of KELT-9b, but not for other species such as Al I, Ca I, Cr I, FeH, Fe II, K I, Li I, Mg II, Na I , OH , Ti I , TiO , V I , V II VO or YI.
- Likelihood mapping techniques were employed on their data analysis results from cross-correlation methods used to search atmospheric species with model spectra and corrected spectra after reducing data and correcting telluric lines and systematics.
- Little variation in emission line contrast between the day- and nightsides suggests that KELT-9b may harbor iron emission on its nightside.
- High-resolution ground-based emission spectroscopy can provide valuable insights into exoplanet atmospheres such as those observed in KELT-9b's atmosphere.
- Continuum-subtracted model emission spectra were generated using petitRADTRANS software to fit a polynomial to the continuum and subtract it from the model spectra.
- Pressure-temperature profiles from Goyal et al., which are only defined for pressures greater than 10^-6 bar were used to create these model spectra.
- Detailed data processing steps used in this analysis are shown through Figure 3 while Figure 4 shows pressure-temperature profiles used to create model emission spectra of KELT-9b.
- These findings have been accepted for publication in AJ journal.

## Summary

The ultrahot Jupiter KELT-9b has an equilibrium temperature of approximately 4000 K and exhibits absorption by several metal species in its transmission spectrum. In this study, the authors used the CARMENES spectrograph to observe partial phase curves and search for atomic and molecular lines in its emission spectrum. They found evidence for emission by Si I, Fe I, Mg I and Ca II in the atmosphere of KELT-9b. However, they did not find any evidence for dayside emission from other species such as Al I, Ca I, Cr I, FeH, Fe II, K I, Li I, Mg II, Na I , OH , Ti I , TiO , V I , V II VO or YI. By employing likelihood mapping techniques on their data analysis results from cross-correlation methods used to search atmospheric species with model spectra and corrected spectra after reducing data and correcting telluric lines and systematics; they found indications of there being little variation in emission line contrast between the day- and nightsides. This suggests that KELT-9b may harbor iron emission on its nightside. The authors also generated continuum-subtracted model emission spectra using petitRADTRANS software to fit a polynomial to the continuum and subtract it from the model spectra. They used pressure-temperature profiles from Goyal et al., which are only defined for pressures greater than 10^-6 bar to create these model spectra. Their findings demonstrate that high-resolution ground-based emission spectroscopy can provide valuable insights into exoplanet atmospheres such as those observed in KELT-9b's atmosphere. The detailed data processing steps used in this analysis are shown through Figure 3 while Figure 4 shows pressure-temperature profiles used to create model emission spectra of KELT-9b. These findings have been accepted for publication in AJ journal.