The metallicity and carbon-to-oxygen ratio of the ultra-hot Jupiter WASP-76b from Gemini-S/IGRINS
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| Main Authors: | , , , , , , , , , , , , , |
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| Format: | Preprint |
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2024
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| author | Mansfield, Megan Weiner Line, Michael R. Wardenier, Joost P. Brogi, Matteo Bean, Jacob L. Beltz, Hayley Smith, Peter Zalesky, Joseph A. Batalha, Natasha Kempton, Eliza M. -R. Montet, Benjamin T. Owen, James E. Plavchan, Peter Rauscher, Emily |
| author_facet | Mansfield, Megan Weiner Line, Michael R. Wardenier, Joost P. Brogi, Matteo Bean, Jacob L. Beltz, Hayley Smith, Peter Zalesky, Joseph A. Batalha, Natasha Kempton, Eliza M. -R. Montet, Benjamin T. Owen, James E. Plavchan, Peter Rauscher, Emily |
| contents | Measurements of the carbon-to-oxygen (C/O) ratios of exoplanet atmospheres can reveal details about their formation and evolution. Recently, high-resolution cross-correlation analysis has emerged as a method of precisely constraining the C/O ratios of hot Jupiter atmospheres. We present two transits of the ultra-hot Jupiter WASP-76b observed between 1.4-2.4 $μ$m with Gemini-S/IGRINS. We detected the presence of H$_{2}$O, CO, and OH at signal-to-noise ratios of 6.93, 6.47, and 3.90, respectively. We performed two retrievals on this data set. A free retrieval for abundances of these three species retrieved a volatile metallicity of $\left[\frac{\mathrm{C}+\mathrm{O}} {\mathrm{H}}\right]=-0.70^{+1.27}_{-0.93}$, consistent with the stellar value, and a super-solar carbon-to-oxygen ratio of C/O$=0.80^{+0.07}_{-0.11}$. We also ran a chemically self-consistent grid retrieval, which agreed with the free retrieval within $1σ$ but favored a slightly more sub-stellar metallicity and solar C/O ratio ($\left[\frac{\mathrm{C}+\mathrm{O}} {\mathrm{H}}\right]=-0.74^{+0.23}_{-0.17}$ and C/O$=0.59^{+0.13}_{-0.14}$). A variety of formation pathways may explain the composition of WASP-76b. Additionally, we found systemic ($V_{sys}$) and Keplerian ($K_{p}$) velocity offsets which were broadly consistent with expectations from 3D general circulation models of WASP-76b, with the exception of a redshifted $V_{sys}$ for H$_{2}$O. Future observations to measure the phase-dependent velocity offsets and limb differences at high resolution on WASP-76b will be necessary to understand the H$_{2}$O velocity shift. Finally, we find that the population of exoplanets with precisely constrained C/O ratios generally trends toward super-solar C/O ratios. More results from high-resolution observations or JWST will serve to further elucidate any population-level trends. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2405_09769 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The metallicity and carbon-to-oxygen ratio of the ultra-hot Jupiter WASP-76b from Gemini-S/IGRINS Mansfield, Megan Weiner Line, Michael R. Wardenier, Joost P. Brogi, Matteo Bean, Jacob L. Beltz, Hayley Smith, Peter Zalesky, Joseph A. Batalha, Natasha Kempton, Eliza M. -R. Montet, Benjamin T. Owen, James E. Plavchan, Peter Rauscher, Emily Earth and Planetary Astrophysics Measurements of the carbon-to-oxygen (C/O) ratios of exoplanet atmospheres can reveal details about their formation and evolution. Recently, high-resolution cross-correlation analysis has emerged as a method of precisely constraining the C/O ratios of hot Jupiter atmospheres. We present two transits of the ultra-hot Jupiter WASP-76b observed between 1.4-2.4 $μ$m with Gemini-S/IGRINS. We detected the presence of H$_{2}$O, CO, and OH at signal-to-noise ratios of 6.93, 6.47, and 3.90, respectively. We performed two retrievals on this data set. A free retrieval for abundances of these three species retrieved a volatile metallicity of $\left[\frac{\mathrm{C}+\mathrm{O}} {\mathrm{H}}\right]=-0.70^{+1.27}_{-0.93}$, consistent with the stellar value, and a super-solar carbon-to-oxygen ratio of C/O$=0.80^{+0.07}_{-0.11}$. We also ran a chemically self-consistent grid retrieval, which agreed with the free retrieval within $1σ$ but favored a slightly more sub-stellar metallicity and solar C/O ratio ($\left[\frac{\mathrm{C}+\mathrm{O}} {\mathrm{H}}\right]=-0.74^{+0.23}_{-0.17}$ and C/O$=0.59^{+0.13}_{-0.14}$). A variety of formation pathways may explain the composition of WASP-76b. Additionally, we found systemic ($V_{sys}$) and Keplerian ($K_{p}$) velocity offsets which were broadly consistent with expectations from 3D general circulation models of WASP-76b, with the exception of a redshifted $V_{sys}$ for H$_{2}$O. Future observations to measure the phase-dependent velocity offsets and limb differences at high resolution on WASP-76b will be necessary to understand the H$_{2}$O velocity shift. Finally, we find that the population of exoplanets with precisely constrained C/O ratios generally trends toward super-solar C/O ratios. More results from high-resolution observations or JWST will serve to further elucidate any population-level trends. |
| title | The metallicity and carbon-to-oxygen ratio of the ultra-hot Jupiter WASP-76b from Gemini-S/IGRINS |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2405.09769 |