Exoplanetology: Exoplanets & Exomoons

IGRINS Observations of WASP-127 b: H2O, CO, and Super-Solar Atmospheric Metallicity in the Inflated sub-Saturn

By Keith Cowing

Status Report

astro-ph.EP

June 21, 2024

Filed under astornomy, astro-ph.EP, astrochemistry, atmosphere, exoplanet, Gemini South, IGRINS, Photochemistry, Spectroscopy, sub-Saturn, WASP-127, WASP-127 b, WASP-127b

IGRINS Observations of WASP-127 b: H2O, CO, and Super-Solar Atmospheric Metallicity in the Inflated sub-Saturn — The detections of H2O, CO, and total atmospheric signal in the atmosphere of WASP-127 b. The CC maps shown here are generated by cross-correlating the residual data with solar composition RCTE models with opacity from H2O alone, CO alone, and all absorbers respectively. The tellurics have been masked and the out-of-transit frames have been cropped in the residual data. The white dashed lines in these maps denote the literature reported values of Vsys0 and Kp0 for the WASP-127 b system. The red cross indicates the peak value of the SNR within each map. Similar to the trail, the peak signal in these maps can be seen blue shifted. The bottom red curves under each panel shows the row/cross-section of the CC SNRs at the peak Kp. — astro-ph.EP

High resolution spectroscopy of exoplanet atmospheres provides insights into their composition and dynamics from the resolved line shape and depth of thousands of spectral lines. WASP-127 b is an extremely inflated sub-Saturn (R_p= 1.311 RJup, M_p= 0.16 M_Jup) with previously reported detections of H₂O, CO₂, and Na. However, the seeming absence of the primary carbon reservoir expected at WASP-127 b temperatures (T_eq ∼ 1400 K) from chemical equilibrium, CO, posed a mystery.

In this manuscript, we present the analysis of high resolution observations of WASP-127 b with the Immersion GRating INfrared Spectrometer (IGRINS) on Gemini South. We confirm the presence of H₂O (8.67 σ) and report the detection of CO (4.34 σ).

Additionally, we conduct a suite of Bayesian retrieval analyses covering a hierarchy of model complexity and self-consistency. When freely fitting for the molecular gas volume mixing ratios, we obtain super-solar metal enrichment for H₂O abundance of log10XH₂O = –1.23+0.29−0.49 and a lower limit on the CO abundance of log10XCO ≥ –2.20 at 2σ confidence.

We also report a tentative evidence of photochemistry in WASP-127 b based upon the indicative depletion of H₂S. This is also supported by the data preferring models with photochemistry over free-chemistry and thermochemistry.

The overall analysis implies a super-solar (∼ 39× Solar; [M/H] = 1.59+0.30−0.30) metallicity for the atmosphere of WASP-127 b and an upper limit on its atmospheric C/O ratio as < 0.68.

Krishna Kanumalla, Michael R. Line, Megan Weiner Mansfield, Luis Welbanks, Peter C. B. Smith, Jacob L. Bean, Lorenzo Pino, Matteo Brogi, Vatsal Panwar

Comments: 18 pages, 15 figures, submitted to AJ, poster at Exo5 conference area-A
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2406.14072 [astro-ph.EP] (or arXiv:2406.14072v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2406.14072
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Submission history
From: Sai Krishna Teja Kanumalla
[v1] Thu, 20 Jun 2024 07:47:42 UTC (23,753 KB)
https://arxiv.org/abs/2406.14072
Astrobiology, Astrochemistry,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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