19 research outputs found
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 and the metastable helium line. We detect Ca II and Na I
with significances of 13.2 and 4.6, 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 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
and level in the H and He I triplet lines,
respectively. From an isothermal Parker wind model, we derive a mass loss rate
of and an outflow temperature of . 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 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 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
The Atmospheres of the Hottest Exoplanets at High Spectral Resolution
What would happen to Jupiter if we moved it two hundred times closer to the Sun? While we cannot conduct such experiment, exoplanets, or planets around other stars, allow us to explore a range of conditions unthinkable to achieve in the Solar System. The first exoplanets were only found three decades ago, but today we know of over 5000 of them, including some rather bizarre “ultrahot Jupiters”: gas giants orbiting so close to their stars that most of their molecules are ripped apart by the extreme heat. In this thesis, we take a tour through our stellar neighborhood to study the atmospheres of some of these exotic worlds and understand their compositions and climates. Our tool in this journey is high resolution spectroscopy, a technique that splits the light from an exoplanet into a myriad of colors to search for the unique fingerprints of the different atmospheric constituents. We start by exploring HAT-P-70b, one of the hottest exoplanets in the Northern Sky. Our analysis of this oddball reveals a remarkably rich atmosphere, full of vaporized metals like calcium, chromium, and iron, blowing around the planets with velocities of several kilometers per second. Our journey also takes us to the puffiest known exoplanet, HAT-P-67b. Here, we find an atmosphere potentially eroding away due to the high stellar irradiation. Our work also demonstrates that high resolution spectroscopy is not exclusive to large ground-based telescopes, and that modest facilities, like the Nordic Optical Telescope, can join the efforts to study the atmospheres of other exoplanets. Eventually, with the next generation of extremely large telescopes, the tools currently developed to study ultrahot Jupiters will be applied to potentially habitable Earth-like planets in an attempt to find out if life has developed on other worlds
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, 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, H and H 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 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 and in the
atmosphere of Earth. We demonstrate how the extracted components can be used to
remove and 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
Unsupervised Spectral Unmixing For Telluric Correction Using A Neural Network Autoencoder
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