Constraints on atmospheric water abundance and cloud deck pressure in the warm Neptune GJ 3470 b via CARMENES transmission spectroscopy

Observations of cooler atmospheres of super-Earths and Neptune sized objects often show flat transmission spectra. The most likely cause of this trend is the presence of aerosols (i.e. clouds and hazes) in the atmospheres of such objects. High-resolution spectroscopy provides an opportunity to test this hypothesis by targeting molecular species whose spectral line cores extend above the level of such opaque decks. In this work, we analyse high-resolution infrared observations of the warm Neptune GJ 3470 b taken over two transits using CARMENES (R ∼ 80,000) and look for signatures of H2O (previously detected using HST WFC3+Spitzer observations) in these transits with a custom pipeline fully accounting for the effects of data cleaning on any potential exoplanet signal. We find that our data are potentially able to weakly detect (∼

Transmission spectroscopy of the lowest-density gas giant: metals and a potential extended outflow in HAT-P-67b

Extremely low-density exoplanets are tantalizing targets for atmospheric characterization because of their promisingly large signals in transmission spectroscopy. We present the first analysis of the atmosphere of the lowest-density gas giant currently known, HAT-P-67 b. This inflated Saturn-mass exoplanet sits at the boundary between hot and ultrahot gas giants, where thermal dissociation of molecules begins to dominate atmospheric composition. We observed a transit of HAT-P-67 b at high spectral resolution with CARMENES and searched for atomic and molecular species using cross-correlation and likelihood mapping. Furthermore, we explored potential atmospheric escape by targeting H$\alpha$ and the metastable helium line. We detect Ca II and Na I with significances of 13.2$\sigma$ and 4.6$\sigma$, respectively. Unlike in several ultrahot Jupiters, we do not measure a day-to-night wind. The large line depths of Ca II suggest that the upper atmosphere may be more ionized than models predict. We detect strong variability in H$\alpha$ and the helium triplet during the observations. These signals suggest the possible presence of an extended planetary outflow that causes an early ingress and late egress. In the averaged transmission spectrum, we measure redshifted absorption at the $\sim 3.8\%$ and $\sim 4.5\%$ level in the H$\alpha$ and He I triplet lines, respectively. From an isothermal Parker wind model, we derive a mass loss rate of $\dot{M} \sim 10^{13}~\rm{g/s}$ and an outflow temperature of $T \sim 9900~\rm{K}$. However, due to the lack of a longer out-of-transit baseline in our data, additional observations are needed to rule out stellar variability as the source of the H$\alpha$ and He signals.Comment: The Astronomical Journal, in press. 17 pages, 9 figure

A roadmap to the efficient and robust characterization of temperate terrestrial planet atmospheres with JWST

Ultra-cool dwarf stars are abundant, long-lived, and uniquely suited to enable the atmospheric study of transiting terrestrial companions with JWST. Amongst them, the most prominent is the M8.5V star TRAPPIST-1 and its seven planets, which have been the favored targets of eight JWST Cycle 1 programs. While Cycle 1 observations have started to yield preliminary insights into the planets, they have also revealed that their atmospheric exploration requires a better understanding of their host star. Here, we propose a roadmap to characterize the TRAPPIST-1 system -- and others like it -- in an efficient and robust manner. We notably recommend that -- although more challenging to schedule -- multi-transit windows be prioritized to constrain stellar heterogeneities and gather up to 2$\times$ more transits per JWST hour spent. We conclude that in such systems planets cannot be studied in isolation by small programs, thus large-scale community-supported programs should be supported to enable the efficient and robust exploration of terrestrial exoplanets in the JWST era

Gravitational Waves in General Relativity

In this paper, we write a summary about general relativity and, in particular,gravitational waves. We start by discussing the mathematics that generalrelativity uses, as well as the geometry in general relativity's spacetime. Afterwards,we explain linearized general relativity and derive the linearizedversions of Einstein's equations. From here, we construct wave solutionsand explain the polarization of gravitational waves. The quadrupole formulais derived, and generation and detection of gravitational waves is brie ydiscussed. Finally, LIGO and its latest discovery of gravitational waves isreviewed

Dry or water world? How the water contents of inner sub-Neptunes constrain giant planet formation and the location of the water ice line

In the pebble accretion scenario, the pebbles that form planets drift inward from the outer disk regions, carrying water ice with them. At the water ice line, the water ice on the inward drifting pebbles evaporates and is released into the gas phase, resulting in water-rich gas and dry pebbles that move into the inner disk regions. Large planetary cores can block the inward drifting pebbles by forming a pressure bump outside their orbit in the protoplanetary disk. Depending on the relative position of a growing planetary core relative to the water ice line, water-rich pebbles might be blocked outside or inside the water ice line. Pebbles blocked outside the water ice line do not evaporate and thus do not release their water vapor into the gas phase, resulting in a dry inner disk, while pebbles blocked inside the water ice line release their water vapor into the gas phase, resulting in water vapor diffusing into the inner disk. As a consequence, close-in sub-Neptunes that accrete some gas from the disk should be dry or wet, respectively, if outer gas giants are outside or inside the water ice line, assuming that giant planets form fast, as has been suggested for Jupiter in our Solar System. Alternatively, a sub-Neptune could form outside the water ice line, accreting a large amount of icy pebbles and then migrating inward as a very wet sub-Neptune. We suggest that the water content of inner sub-Neptunes in systems with giant planets that can efficiently block the inward drifting pebbles could constrain the formation conditions of these systems, thus making these sub-Neptunes exciting targets for detailed characterization (e.g., with JWST, ELT, or ARIEL). In addition, the search for giant planets in systems with already characterized sub-Neptunes can be used to constrain the formation conditions of giant planets as well

Mining the Ultrahot Skies of HAT-P-70b: Detection of a Profusion of Neutral and Ionized Species

With an equilibrium temperature above 2500 K, the recently discovered HAT-P-70 b belongs to a new class of exoplanets known as ultra-hot Jupiters: extremely irradiated gas giants with day-side temperatures that resemble those found in stars. These ultra-hot Jupiters are among the most amenable targets for follow-up atmospheric characterization through transmission spectroscopy. Here, we present the first analysis of the transmission spectrum of HAT-P-70 b using high-resolution data from the HARPS-N spectrograph of a single transit event. We use a cross-correlation analysis and transmission spectroscopy to look for atomic and molecular species in the planetary atmosphere. We detect absorption by Ca II, Cr I, Cr II, Fe I, Fe II, H I, Mg I, Na I and V I, and we find tentative evidence of Ca I and Ti II. Overall, these signals appear blue-shifted by a few km s$^{-1}$, suggestive of winds flowing at high velocity from the day-side to the night-side. We individually resolve the Ca II H & K lines, the Na I doublet, and the H$\alpha$, H$\beta$ and H$\gamma$ Balmer lines. The cores of the Ca II and H I lines form well above the continuum, indicating the existence of an extended envelope. We refine the obliquity of this highly misaligned planet to $107.9^{+2.0}_{-1.7}$ degrees by examining the Doppler shadow that the planet casts on its A-type host star. These results place HAT-P-70 b as one of the exoplanets with the highest number of species detected in its atmosphere.Comment: 17 pages, 10 figures, accepted to A

Unsupervised Spectral Unmixing For Telluric Correction Using A Neural Network Autoencoder

The absorption of light by molecules in the atmosphere of Earth is a complication for ground-based observations of astrophysical objects. Comprehensive information on various molecular species is required to correct for this so called telluric absorption. We present a neural network autoencoder approach for extracting a telluric transmission spectrum from a large set of high-precision observed solar spectra from the HARPS-N radial velocity spectrograph. We accomplish this by reducing the data into a compressed representation, which allows us to unveil the underlying solar spectrum and simultaneously uncover the different modes of variation in the observed spectra relating to the absorption of $\mathrm{H_2O}$ and $\mathrm{O_2}$ in the atmosphere of Earth. We demonstrate how the extracted components can be used to remove $\mathrm{H_2O}$ and $\mathrm{O_2}$ tellurics in a validation observation with similar accuracy and at less computational expense than a synthetic approach with molecfit.Comment: Presented at Workshop on Machine Learning and the Physical Sciences (NeurIPS 2021

Exoplanet atmospheres at high resolution through a modest-size telescope : FeII in MASCARA-2b and KELT-9b with FIES on the Nordic Optical Telescope

Ground-based, high-resolution spectrographs are providing us with an unprecedented view of the dynamics and chemistry of the atmospheres of planets outside the Solar System. While there are a large number of stable and precise high-resolution spectrographs on modest-size telescopes, it is the spectrographs at observatories with apertures larger than 3.5 m that dominate the atmospheric follow-up of exoplanets. In this work we explore the potential of characterising exoplanetary atmospheres with FIES, a high-resolution spectrograph at the 2.56 m Nordic Optical Telescope. We observed two transits of MASCARA-2 b (also known as KELT-20 b) and one transit of KELT-9 b to search for atomic iron, a species that has recently been discovered in both neutral and ionised forms in the atmospheres of these ultra-hot Jupiters using large telescopes. Using a cross-correlation method, we detect a signal of FeII at the 4.5and 4.0level in the transits of MaSCARA-2 b. We also detect FeII in the transit of KELT-9 b at the 8.5level. Although we do not find any significant Doppler shift in the signal of MASCARA-2 b, we do measure a moderate blueshift (3a-6 km s1) of the feature in KELT-9 b, which might be a manifestation of high-velocity winds transporting FeII from the planetary dayside to the nightside. Our work demonstrates the feasibility of investigating exoplanet atmospheres with FIES, and it potentially unlocks a wealth of additional atmosphere detections with this and other high-resolution spectrographs mounted on similar-size telescopes

TOI-1518b: A Misaligned Ultra-hot Jupiter with Iron in Its Atmosphere

We present the discovery of TOI-1518b-an ultra-hot Jupiter orbiting a bright star (V=8.95). The transiting planet is confirmed using high-resolution optical transmission spectra from EXPRES. It is inflated, with Rp=1.875±0.053 RJ, and exhibits several interesting properties, including a misaligned orbit ( - 240.34+0.98 0.93 degrees) and nearly grazing transit ( = - b 0.9036+0.0053 0.0061). The planet orbits a fast-rotating F0 host star (Teff;7300 K) in 1.9 days and experiences intense irradiation. Notably, the TESS data show a clear secondary eclipse with a depth of 364±28 ppm and a significant phase-curve signal, from which we obtain a relative day-night planetary flux difference of roughly 320 ppm and a 5.2s detection of ellipsoidal distortion on the host star. Prompted by recent detections of atomic and ionized species in ultrahot Jupiter atmospheres, we conduct an atmospheric cross-correlation analysis. We detect neutral iron (5.2s), at = - K 157+ p 44 68 km s-1 and = - - V 16+ sys 4 2, adding another object to the small sample of highly irradiated gas-giant planets with Fe detections in transmission. Detections so far favor particularly inflated gas giants with radii 1.78 RJ, which may be due to observational bias. With an equilibrium temperature of Teq=2492±38 K and a measured dayside brightness temperature of 3237±59 K (assuming zero geometric albedo), TOI-1518b is a promising candidate for future emission spectroscopy to probe for a thermal inversion