Carbon monoxide and water vapor in the atmosphere of the non-transiting exoplanet HD 179949 b

(Abridged) In recent years, ground-based high-resolution spectroscopy has become a powerful tool for investigating exoplanet atmospheres. It allows the robust identification of molecular species, and it can be applied to both transiting and non-transiting planets. Radial-velocity measurements of the star HD 179949 indicate the presence of a giant planet companion in a close-in orbit. Here we present the analysis of spectra of the system at 2.3 micron, obtained at a resolution of R~100,000, during three nights of observations with CRIRES at the VLT. We targeted the system while the exoplanet was near superior conjunction, aiming to detect the planet's thermal spectrum and the radial component of its orbital velocity. We detect molecular absorption from carbon monoxide and water vapor with a combined S/N of 6.3, at a projected planet orbital velocity of K_P = (142.8 +- 3.4) km/s, which translates into a planet mass of M_P = (0.98 +- 0.04) Jupiter masses, and an orbital inclination of i = (67.7 +- 4.3) degrees, using the known stellar radial velocity and stellar mass. The detection of absorption features rather than emission means that, despite being highly irradiated, HD 179949 b does not have an atmospheric temperature inversion in the probed range of pressures and temperatures. Since the host star is active (R_HK > -4.9), this is in line with the hypothesis that stellar activity damps the onset of thermal inversion layers owing to UV flux photo-dissociating high-altitude, optical absorbers. Finally, our analysis favors an oxygen-rich atmosphere for HD 179949 b, although a carbon-rich planet cannot be statistically ruled out based on these data alone.Comment: 10 pages, 9 figures. Accepted for publication in Astronomy and Astrophysic

Detection of water absorption in the day side atmosphere of HD 189733 b using ground-based high-resolution spectroscopy at 3.2 microns

We report a 4.8 sigma detection of water absorption features in the day side spectrum of the hot Jupiter HD 189733 b. We used high-resolution (R~100,000) spectra taken at 3.2 microns with CRIRES on the VLT to trace the radial-velocity shift of the water features in the planet's day side atmosphere during 5 h of its 2.2 d orbit as it approached secondary eclipse. Despite considerable telluric contamination in this wavelength regime, we detect the signal within our uncertainties at the expected combination of systemic velocity (Vsys=-3 +5-6 km/s) and planet orbital velocity (Kp=154 +14-10 km/s), and determine a H2O line contrast ratio of (1.3+/-0.2)x10^-3 with respect to the stellar continuum. We find no evidence of significant absorption or emission from other carbon-bearing molecules, such as methane, although we do note a marginal increase in the significance of our detection to 5.1 sigma with the inclusion of carbon dioxide in our template spectrum. This result demonstrates that ground-based, high-resolution spectroscopy is suited to finding not just simple molecules like CO, but also to more complex molecules like H2O even in highly telluric contaminated regions of the Earth's transmission spectrum. It is a powerful tool that can be used for conducting an immediate census of the carbon- and oxygen-bearing molecules in the atmospheres of giant planets, and will potentially allow the formation and migration history of these planets to be constrained by the measurement of their atmospheric C/O ratios.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter

J-band variability of M dwarfs in the WFCAM Transit Survey

We present an analysis of the photometric variability of M dwarfs in the Wide Field Camera (WFCAM) Transit Survey. Although periodic light-curve variability in low mass stars is generally dominated by photospheric star spot activity, M dwarf variability in the J band has not been as thoroughly investigated as at visible wavelengths. Spectral type estimates for a sample of over 200 000 objects are made using spectral type-colour relations, and over 9600 dwarfs (J 0.2 mag flaring event from an M4V star in our sample.Peer reviewe

A weak spectral signature of water vapour in the atmosphere of HD 179949 b at high spectral resolution in the L band

High-resolution spectroscopy (R≤20,000) is currently the only known method to constrain the orbital solution and atmospheric properties of non-transiting hot Jupiters. It does so by resolving the spectral features of the planet into a forest of spectral lines and directly observing its Doppler shift while orbiting the host star. In this study, we analyse VLT/CRIRES (R=100,000) L-band observations of the non-transiting giant planet HD 179949 b centred around 3.5μm. We observe a weak (3.0σ, or S/N=4.8) spectral signature of H2O in absorption contained within the radial velocity of the planet at superior-conjunction, with a mild dependence on the choice of line list used for the modelling. Combining this data with previous observations in the K band, we measure a detection significance of 8.4σ for an atmosphere that is most consistent with a shallow lapse-rate, solar C/O ratio, and with CO and H2O being the only major sources of opacity in this wavelength range. As the two sets of data were taken 3 yr apart, this points to the absence of strong radial-velocity anomalies due, e.g. to variability in atmospheric circulation. We measure a projected orbital velocity for the planet of K_P=(145.2±2.0) km/s (1σ ) and improve the error bars on this parameter by ∼70 per cent. However, we only marginally tighten constraints on orbital inclination (66.2+3.7−3.1 deg) and planet mass (0.963+0.036−0.031 Jupiter masses), due to the dominant uncertainties of stellar mass and semi-major axis. Follow ups of radial-velocity planets are thus crucial to fully enable their accurate characterization via high-resolution spectroscopy

Searching for transits in the Wide Field Camera Transit Survey with difference-imaging light curves

The Wide Field Camera Transit Survey is a pioneer program aiming at for searching extra-solar planets in the near-infrared. The images from the survey are processed by a data reduction pipeline, which uses aperture photometry to construct the light curves. We produce an alternative set of light curves using the difference-imaging method for the most complete field in the survey and carry out a quantitative comparison between the photometric precision achieved with both methods. The results show that differencephotometry light curves present an important improvement for stars with J > 16. We report an implementation on the box-fitting transit detection algorithm, which performs a trapezoid-fit to the folded light curve, providing more accurate results than the boxfitting model. We describe and optimize a set of selection criteria to search for transit candidates, including the V-shape parameter calculated by our detection algorithm. The optimized selection criteria are applied to the aperture photometry and difference-imaging light curves, resulting in the automatic detection of the best 200 transit candidates from a sample of ~475 000 sources. We carry out a detailed analysis in the 18 best detections and classify them as transiting planet and eclipsing binary candidates. We present one planet candidate orbiting a late G-type star. No planet candidate around M-stars has been found, confirming the null detection hypothesis and upper limits on the occurrence rate of short-period giant planets around M-dwarfs presented in a prior study. We extend the search for transiting planets to stars with J ≤ 18, which enables us to set a stricter upper limit of 1.1%. Furthermore, we present the detection of five faint extremely-short period eclipsing binaries and three M-dwarf/M-dwarf binary candidates. The detections demonstrate the benefits of using the difference-imaging light curves, especially when going to fainter magnitudes.Peer reviewe

The Mantis Network IV: A titanium cold-trap on the ultra-hot Jupiter WASP-121 b

Observations of WASP-121 b have suggested an under-abundance of titanium and titanium-oxide from its terminator region. In this study, we aim to determine whether this depletion is global by investigating the day-side emission spectrum. We analyse 8 epochs of high-resolution spectra obtained with ESPRESSO, targeting orbital phases when the day-side is in view. We use a cross-correlation method to search for various atoms, TiO and VO and compare to models. We constrain the velocities and phase-function of the emission signal using a Bayesian framework. We report significant detections of Ca I, V I, Cr I, Mn I, Fe I, Co I and Ni I, but not T i or TiO. Models containing Ti are unable to reproduce the data. The detected signals are consistent with the known orbital and systemic velocities and with peak emission originating from the sub-stellar point. We find that Ti is depleted from regions of the atmosphere where transmission and emission spectroscopy are sensitive. We interpret this as evidence for the night-side condensation of titanium, preventing it from being mixed back into the upper layers of the atmosphere elsewhere on the planet. Species with lower condensation temperatures are unaffected, implying sharp chemical transitions exist between ultra-hot Jupiters that have slight differences in temperature or dynamical properties. As TiO can act as a strong source of stratospheric heating, cold-trapping creates a coupling between the thermal structures on the day-side and night-side, and thus condensation chemistry needs to be included in global circulation models. Observed elemental abundances in hot Jupiters are not reliably representative of bulk abundances unless night-side condensation is accounted for or the planet is hot enough to avoid night-side cold-traps entirely. Planetary rotation may significantly lower the apparent orbital velocity of emission signals.Comment: 23 pages, submitted to A\&A on September 13, 2022, resubmission under revie

Prospects for Characterizing the Haziest Sub-Neptune Exoplanets with High Resolution Spectroscopy

Observations to characterize planets larger than Earth but smaller than Neptune have led to largely inconclusive interpretations at low spectral resolution due to hazes or clouds that obscure molecular features in their spectra. However, here we show that high-resolution spectroscopy (R $\sim$ 25,000 to 100,000) enables one to probe the regions in these atmospheres above the clouds where the cores of the strongest spectral lines are formed. We present models of transmission spectra for a suite of GJ1214b-like planets with thick photochemical hazes covering 1 - 5 $\mu$m at a range of resolutions relevant to current and future ground-based spectrographs. Furthermore, we compare the utility of the cross-correlation function that is typically used with a more formal likelihood-based approach, finding that only the likelihood based method is sensitive to the presence of haze opacity. We calculate the signal-to-noise of these spectra, including telluric contamination, required to robustly detect a host of molecules such as CO, CO$_{2}$, H$_{2}$O, and CH$_{4}$, and photochemical products like HCN, as a function of wavelength range and spectral resolution. Spectra in M band require the lowest S/N$_{res}$ to detect multiple molecules simultaneously. CH$_{4}$ is only observable for the coolest models ($T_{\rm{eff}} =$ 412 K) and only in the L band. We quantitatively assess how these requirements compare to what is achievable with current and future instruments, demonstrating that characterization of small cool worlds with ground-based high resolution spectroscopy is well within reach.Comment: Submitted to AAS Journals, revised to reflect referee comments. Posting of this manuscript on the arXiv was coordinated with S. Ghandi et a