The Roasting Marshmallows Program with IGRINS on Gemini South V: Atmosphere of MASCARA-1b is Enriched in Refractory Elements

arXiv:2606.07497 · astro-ph.EP · Submitted 2026-06-05 · Read on arXiv

Krishna Kanumalla, Michael R. Line, Martina Chiarella, Matteo Brogi, Peter C. B. Smith, Jorge A. Sanchez, Yayaati Chachan, Joshua Lothringer, Joost P. Wardenier, Hayley Beltz, Carlos Saffe, Emily K. Deibert, Megan Weiner Mansfield, Stefan Pelletier, Vivien Parmentier, Yeon-ho Choi, Swaetha Ramkumar, Arjun B. Savel, Luis Welbanks, Jacob L. Bean, Vatsal Panwar, Tomás Azevedo Silva, Lorenzo Pino, Yuya Hayashi, Dongwook Lim, Cicero X. Lu, Venu M. Kalari, Teo Močnik, Mark G. Rawlings, Heeyoung Oh, Ruben J. Diaz, Chan Park, Jae-Joon Lee, Sanghyuk Kim, Ueejeong Jeong, Hye-In Lee, Woojin Park, Youngsam Yu, Yunjong Kim, Moo-Young Chun, Jae Sok Oh, Sungho Lee, Jeong-Gyun Jang, Bi-Ho Jang, Hyeon Cheol Seong, Hyun-Jeong Kim, Cynthia B. Brooks, Gregory N. Mace, Hanshin Lee, John M. Good, Daniel T. Jaffe, Kang-Min Kim, In-Soo Yuk, Narae Hwang, Byeong-Gon Park, Hwihyun Kim, Brian Chinn, Francisco Ramos, Pablo Prado, John White, Andres Olivares, Valentina Oyarzun, Emma Kurz, Hawi Stecher, Carlos Quiroz, Ignacio Arriagada, Thomas L. Hayward, Hyewon Suh, Jen Miller, Siyi Xu, Emanuele Paolo Farina, Charlie Figura, Andrew Stephens, Bryan Miller, Kathleen Labrie, Paul Hirst, Edo Tapia, Zachary Hartmann

astro-ph.EP

Submitted: 2026-06-05

Comments: 20 pages, 12 figures, accepted for publication in AJ

DOI: 10.3847/1538-3881/ae77f1

License: http://creativecommons.org/licenses/by/4.0/

The gist: Ultra-hot Jupiters (UHJs; T eq 2000 K) enable simultaneous detection of volatile (ice-forming) and refractory (rock-forming) species in planetary atmospheres, providing a powerful diagnostic of

Terminology

Abstract

Ultra-hot Jupiters (UHJs; T eq 2000 K) enable simultaneous detection of volatile (ice-forming) and refractory (rock-forming) species in planetary atmospheres, providing a powerful diagnostic of planet formation and atmospheric processing. We present a comprehensive high-resolution cross-correlation spectroscopy (HRCCS) analysis of the UHJ MASCARA-1b (T eq about 2600 K) using the IGRINS and IGRINS-2 spectrographs. We detect robust (SNR > 4) signals from H 2 O, CO, OH, Fe I, Mg I, Ca I, and Ti I, marking the most complete atmospheric inventory of MASCARA-1b to date. Using a chemically consistent atmospheric inference framework, we constrain elemental abundances to a typical precision of about 0.2 dex, retrieving a solar atmospheric metallicity ([M/H] = 0.07+0.17-0.13 about 1.2 times solar), a C/O ratio (C/O = 0.65+0.08-0.08) consistent with solar value (C/O = 0.59), an enhanced refractory abundance ([R/H] = 0.40+0.23-0.17 about 2.5 times solar; about 3.8 times stellar), and a moderately super-solar refractory-to-volatile ratio ([R/V] = 0.36+0.11-0.09 about 2.3 times solar). Comparison with formation models suggests that MASCARA-1b most likely accreted material between the soot-H 2 O or H 2 O-CO snowlines (at 68 % confidence). We additionally find stellar values for atmospheric Ti/Mg and Ca/Mg ratios (at 68 % confidence). The Mg/Fe is also found to be consistent with stellar value at 95 % confidence. Therefore, we do not find strong indication of nightside cold trapping in MASCARA-1b. As homogeneous refractory-to-volatile measurements expand across the UHJ population, particularly with upcoming Extremely Large Telescopes, these diagnostics will enable statistically robust tests of emerging trends in giant planet formation and atmospheric evolution.

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