ExoMol molecular line lists – XXXIII. The spectrum of Titanium Oxide

Abstract

Accurate line lists are crucial for correctly modelling a variety of astrophysical phenomena, including stellar photospheres and the atmospheres of extra-solar planets. This paper presents a new line database Toto for the main isotopologues of titanium oxide (TiO): 46 Ti 16 O, 47 Ti 16 O, 48 Ti 16 O, 49 Ti 16 O and 50 Ti 16 O. The 48 Ti 16 O line list contains transitions with wave-numbers up to 30,000 cm −1 ie long-wards of 0.33 µm.The Toto line list includes all dipole-allowed transitions between 13 low-lying electronic states (X Σ + ). Ab initio potential energy curves (PECs) are computed at the icMRCI level and combined with spin-orbit and other coupling curves. These PECs and couplings are iteratively refined to match known empirical energy levels. Accurate line intensities are generated using ab initio dipole moment curves. The Toto line lists are appropriate for temperatures below 5000 K and contain 30 million transitions for 48 Ti 16 O; it is made available in electronic form via the CDS data centre and via www.exomol.com. Tests of the line lists show greatly improved agreement with observed spectra for objects such as M-dwarfs GJ876 and GL581.

Non-detection of TiO and VO in the atmosphere of WASP-121b using high-resolution spectroscopy

“…Their MARVEL codebase uses laboratory measurements to correct and refine the quantum chem- istry calculations used to generate the line-lists, theoretically resulting in more accurate results (McKemmish et al 2017). The "MARVEL-ised" ToTo line list has been found to perform slightly better than other line lists in cross-correlation with Mdwarf stars (McKemmish et al 2019). However, the VO line list has not yet been similarly corrected.…”

“…in both its original 1998 incarnation and the updated, corrected 2012 version, and the new ToTo line list from ExoMol(McKemmish et al 2019). This was done to allow us to benchmark the performance of the different TiO line lists against each other, both in the event of a detection and in our injection tests, as line lists are known to vary considerably.…”

Exploring the Atmospheric Dynamics of the Extreme Ultrahot Jupiter KELT-9b Using TESS Photometry

“…We fixed the stellar effective temperature and the planet-to-star radius ratio to the previously published values from Gaudi et al (2017) and Mansfield et al (2020) that we used when fitting for the blackbody brightness temperatures in Section 4.1: T eff =10,170 K and R p /R * =0.08004. For spectral line lists, we used the ExoMol spectroscopic databases for H 2 O (Barber et al 2006;Polyansky et al 2018) McKemmish et al 2019); for CO, we used Li et al (2015); for CO 2 , we used the HITEMP database (Rothman et al 2010); and spectral lines for Fe, Fe + , Ti, Ti + , Ca, Ca + , Na, K, Y, Y + , AlO, and SH were taken from Kurucz & Bell (1995). In addition, we included the continuum opacities from H − (John 1988) and collision-induced absorption (H 2 -H 2 , H 2 -He, H-He; Abel et al 2011;Karman et al 2019), as calculated using the open-source HELIOS-K opacity calculator (Grimm & Heng 2015).…”

Searching for thermal inversion agents in the transmission spectrum of KELT-20b/MASCARA-2b: detection of neutral iron and ionised calcium H&K lines

“…High-resolution analysis using cross-correlation is highly dependent on the accuracy of the line list. Among the considered molecular species the only line list that has been proven to be accurate enough for high-resolution analysis is the TiO line list (Hoeijmakers et al 2015;Nugroho et al 2017;McKemmish et al 2019). In the combined HARPSN data sets, the S/N median of TiO recovered using TiO (Plez '12) and TiO-Toto line list is higher than using TiO (Plez '98), while in the CARMENES data set the S/N median of the recovered signals are comparable.…”