Estimation of Exoplanetary Planet-to-Star Radius Ratio with Homomorphic Processing

In this paper a homomorphic filtering scheme is proposed to improve the estimation of the planet/star radius ratio in astronomical transit signals. The idea is to reduce the effect of the short-term earth atmosphere variations. A two-step method is presented to compute the parameters of the transit curve from both the unfiltered and filtered data. A Monte Carlo analysis is performed by using correlated and uncorrelated noise to determine the parameters of the proposed FFT filter. The method is tested with observations of WASP-19b and WASP-17b obtained with the FORS2 instrument at the Very Large Telescope (VLT). The multi parametric fitting and the associated errors are obtained with the JKTEBOP software. The results with the white light of the exo-planet data mentioned above suggest that the homomorphic filtering can lead to substantial relative reductions in the error bars as high as 45.5% and 76.9%, respectively. The achieved reductions in the averaged error bars per channel were 48.4% with WASP-19b and 63.6% with WASP-17b. Open source MATLAB code to run the method proposed here can be downloaded from http://www.cmrsp.cl. This code was used to obtain the results presented in this paper

Probing the atmosphere of a sub-Jovian planet orbiting a cool dwarf

We derive the 0.01 $\mu$m binned transmission spectrum, between 0.74 and 1.0 $\mu$m, of WASP-80b from low resolution spectra obtained with the FORS2 instrument attached to ESO's Very Large Telescope. The combination of the fact that WASP-80 is an active star, together with instrumental and telluric factors, introduces correlated noise in the observed transit light curves, which we treat quantitatively using Gaussian Processes. Comparison of our results together with those from previous studies, to theoretically calculated models reveals an equilibrium temperature in agreement with the previously measured value of 825K, and a sub-solar metallicity, as well as an atmosphere depleted of molecular species with absorption bands in the IR ($\gg 5\sigma$). Our transmission spectrum alone shows evidence for additional absorption from the potassium core and wing, whereby its presence is detected from analysis of narrow 0.003 $\mu$m bin light curves ($\gg 5\sigma$). Further observations with visible and near-UV filters will be required to expand this spectrum and provide more in-depth knowledge of the atmosphere. These detections are only made possible through an instrument-dependent baseline model and a careful analysis of systematics in the data.Comment: 13 pages, 11 figures, 3 tables. Accepted for publication in MNRA

Detection of Aerosols at Microbar Pressures in an Exoplanet Atmosphere

Formation of hazes at microbar pressures has been explored by theoretical models of exoplanet atmospheres to explain Rayleigh scattering and/or featureless transmission spectra, however observational evidence of aerosols in the low pressure formation environments has proved elusive. Here, we show direct evidence of aerosols existing at $\sim$1 microbar pressures in the atmosphere of the warm sub-Saturn WASP-69b using observations taken with Space Telescope Imaging Spectrograph (STIS) and Wide Field Camera 3 (WFC3) instruments on the Hubble Space Telescope. The transmission spectrum shows a wavelength-dependent slope induced by aerosol scattering that covers 11 scale heights of spectral modulation. Drawing on the extensive studies of haze in our Solar System, we model the transmission spectrum based on a scaled version of Jupiter's haze density profile to show that WASP-69b transmission spectrum can be produced by scattering from an approximately constant density of particles extending throughout the atmospheric column from 40 millibar to microbar pressures. These results are consistent with theoretical expectations based on microphysics of the aerosol particles that have suggested haze can exist at microbar pressures in exoplanet atmospheres.Comment: 15 pages, 13 figures, accepted for publication in A

Orbital alignment of the eccentric warm Jupiter TOI-677 b

Warm Jupiters lay out an excellent laboratory for testing models of planet formation and migration. Their separation from the host star makes tidal reprocessing of their orbits ineffective, which preserves the orbital architectures that result from the planet-forming process. Among the measurable properties, the orbital inclination with respect to the stellar rotational axis, stands out as a crucial diagnostic for understanding the migration mechanisms behind the origin of close-in planets. Observational limitations have made the procurement of spin-orbit measurements heavily biased toward hot Jupiter systems. In recent years, however, high-precision spectroscopy has begun to provide obliquity measurements for planets well into the warm Jupiter regime. In this study, we present Rossiter-McLaughlin (RM) measurements of the projected obliquity angle for the warm Jupiter TOI-677 b using ESPRESSO at the VLT. TOI-677 b exhibits an extreme degree of alignment ($\lambda = 0.3 \pm 1.3$ deg), which is particularly puzzling given its significant eccentricity ($e \approx 0.45$). TOI-677 b thus joins a growing class of close-in giants that exhibit large eccentricities and low spin-orbit angles, which is a configuration not predicted by existing models. We also present the detection of a candidate outer brown dwarf companion on an eccentric, wide orbit ($e \approx 0.4$ and $P \approx 13$ yr). Using simple estimates, we show that this companion is unlikely to be the cause of the unusual orbit of TOI-677 b. Therefore, it is essential that future efforts prioritize the acquisition of RM measurements for warm Jupiters.Comment: 15 pages, 6 figures, 5 tables. Accepted for publication in the Astronomical Journa

Probing the atmosphere of a sub-Jovian planet orbiting a cool dwarf

We derive the 0.01-ľm binned transmission spectrum, between 0.74 and 1.0 ľm, of WASP-80b from low-resolution spectra obtained with the Focal Reducer and low-dispersion Spectrograph 2 instrument attached to ESO's Very Large Telescope. The combination of the fact that WASP-80 is an active star, together with instrumental and telluric factors, introduces correlated noise in the observed transit light curves, which we treat quantitatively using Gaussian processes. Comparison of our results together with those from previous studies to theoretically calculated models reveals an equilibrium temperature in agreement with the previously measured value of 825 K, and a subsolar metallicity, as well as an atmosphere depleted of molecular species with absorption bands in the infrared (ť5?). Our transmission spectrum alone shows evidence for additional absorption from the potassium core and wing, whereby its presence is detected from analysis of narrow 0.003 ľm bin light curves (ť5?). Further observations with visible and near-ultraviolet filters will be required to expand this spectrum and provide more in-depth knowledge of the atmosphere. These detections are only made possible through an instrument-dependent baseline model and a careful analysis of systematics in the data

A Spectral Survey of WASP-19b with ESPRESSO

High resolution precision spectroscopy provides a multitude of robust techniques for probing exoplanetary atmospheres. We present multiple VLT/ESPRESSO transit observations of the hot-Jupiter exoplanet WASP-19b with previously published but disputed atmospheric features from low resolution studies. Through spectral synthesis and modeling of the Rossiter-McLaughlin (RM) effect we calculate stellar, orbital and physical parameters for the system. From narrow-band spectroscopy we do not detect any of H\,I, Fe\,I, Mg\,I, Ca\,I, Na\,I and K\,I neutral species, placing upper limits on their line contrasts. Through cross correlation analyses with atmospheric models, we do not detect Fe\,I and place a 3$\sigma$ upper limit of $\log\,(X_{\textrm{Fe}}/X_\odot) \approx -1.83\,\pm\,0.11$ on its mass fraction, from injection and retrieval. We show the inability to detect the presence of H$_2$O for known abundances, owing to lack of strong absorption bands, as well as relatively low S/N ratio. We detect a barely significant peak (3.02\,$\pm$\,0.15\,$\sigma$) in the cross correlation map for TiO, consistent with the sub-solar abundance previously reported. This is merely a hint for the presence of TiO and does \textit{not} constitute a confirmation. However, we do confirm the presence of previously observed enhanced scattering towards blue wavelengths, through chromatic RM measurements, pointing to a hazy atmosphere. We finally present a reanalysis of low resolution transmission spectra of this exoplanet, concluding that unocculted starspots alone cannot explain previously detected features. Our reanalysis of the FORS2 spectra of WASP-19b finds a $\sim$\,100$\times$ sub-solar TiO abundance, precisely constrained to $\log\,X_{\textrm{TiO}} \approx -7.52 \pm 0.38$, consistent with the TiO hint from ESPRESSO. We present plausible paths to reconciliation with other seemingly contradicting results.Comment: 24 pages, 16 figures, submitted to MNRA

Detection of titanium oxide in the atmosphere of a hot Jupiter.

As an exoplanet transits its host star, some of the light from the star is absorbed by the atoms and molecules in the planet's atmosphere, causing the planet to seem bigger; plotting the planet's observed size as a function of the wavelength of the light produces a transmission spectrum. Measuring the tiny variations in the transmission spectrum, together with atmospheric modelling, then gives clues to the properties of the exoplanet's atmosphere. Chemical species composed of light elements-such as hydrogen, oxygen, carbon, sodium and potassium-have in this way been detected in the atmospheres of several hot giant exoplanets, but molecules composed of heavier elements have thus far proved elusive. Nonetheless, it has been predicted that metal oxides such as titanium oxide (TiO) and vanadium oxide occur in the observable regions of the very hottest exoplanetary atmospheres, causing thermal inversions on the dayside. Here we report the detection of TiO in the atmosphere of the hot-Jupiter planet WASP-19b. Our combined spectrum, with its wide spectral coverage, reveals the presence of TiO (to a confidence level of 7.7σ), a strongly scattering haze (7.4σ) and sodium (3.4σ), and confirms the presence of water (7.9σ) in the atmosphere

Entdecken von fremden Lufträumen : Ermittlung und Charakterisierung der Atmosphären von Exoplaneten mit bodenbezogener Transmissionsspektroskopie

Characterisation of extra-solar planets is hot business. Since the first discoveries of these alien worlds merely a couple of decades ago, we have made huge progress in understanding and differentiating their physical properties. Of those aspects, the atmosphere has proved to be the most interesting characteristic. Not only does it lead to better understand the interior of a planet and its formation process and history, it also provides us with a channel through which possible signs of biological life on those worlds capable of harbouring them can be detected. This cumulative thesis highlights mainly results from three published first-author publications, as well as a further study currently under review, all of which are presented in peer-reviewed journals. The atmospheres of the three planets in the hot Jupiter regime, those the size of Jupiter and very close to their host stars, are studied with the technique of transmission spectroscopy. Sedaghati et al. (2017) utilises the FORS2 instrument, at the VLT, data from ESO's archive to perform transmission spectroscopy in the presence of systematic effects introduced by the old, degraded prisms of the atmospheric dispersion corrector. Gaussian Process methods are used to model the correlated noise in the transit light curves of the exoplanet WASP-80b and estimate the contribution from various sources of red noise. From the obtained transmission spectrum, the presence of molecular species, that lead to enhanced absorption in the infra-red domain, is rejected. Additionally neutral, atomic potassium is detected from absorption both in the line cores and the pressure-broadened wing. Both of these conclusions are made at high statistical signifi cance ( >> 5σ ). Sedaghati et al. (2015) is a letter which briefly presented the improvements made to transmission spectroscopic observations performed with FORS2 and provided the community with the impetus to once again return to this instrument for such observations. Since then, there has been an unprecedented number of publications announcing a variety of exo-atmospheric detections with this instrument. In a study currently under review, WASP-19b observations of this work are utilised together with two further observations of this target with near-UV and near-IR grisms of FOR2 to obtain a complete optical and high resolution transmission spectrum of this planet. With the aid of highly specialised observational and analysis techniques, as well as atmospheric retrieval methods, this work makes the very first signifi cant detection of a metal oxide (TiO) in the atmosphere of an exoplanet. This fi nding sheds new light on hot exo-atmosphere thermal inversion theories. Additionally, there is also signi ficant detections of H2O and strong scattering hazes. Finally, Sedaghati et al. (2016) is the study of the atmosphere of WASP-17b, the exoplanet with one of the largest expected atmospheric signals in transmission. In this work, presence of potassium in the upper atmosphere is signifi cantly detected from enhanced absorption in the pressure broadened wings of the line core. Additionally, there is very marginal evidence for the presence of sodium in the atmosphere, which had previously been claimed to have been discovered. The works presented here make valuable contributions to a very limited sample of exoplanetary atmosphere detections. Together they present a benchmark for an optimal approach to performing transmission spectroscopy from the ground and show the capabilities of the FORS2 instrument in performing such studies. The methodology provides a conservative, and subsequently realistic, approach to estimating the fi nal parameter precisions and fully accounts for the contribution of systematic noise in a non-parametric manner. Hence, any atmospheric claim made in this work constitutes a robust statistical detection.Die Charakterisierung extrasolarer Planeten ist ein viel diskutiertes Thema. Seit der ersten Entdeckung dieser fremden Welten vor nur ein paar Jahrzehnten, gab es großartige Fortschritte im Verstehen und Unterscheiden ihrer physikalischen Eigenschaften. Von all diesen ist die Atmosphäre die wahrscheinlich interessanteste. Wir erhalten nicht nur ein besseres Verständnis vom Inneren des Planeten, seiner Entstehungsprozesse und seiner Geschichte, sondern auch zusätzliche Informationen über mögliche Zeichen von biologischem Leben. Die vorliegende kumulative Arbeit beleuchtet haupts ächlich die Resultate von drei bereits publizierten Erstautor Schriften, sowie einer, sich derzeit noch im Review Prozess befindlichen, weiteren Studie. Alle hier präsentierten Arbeiten beschäftigen sich mit den Atmosphären von drei Exoplaneten im sogenannten "hot Jupiter" Regime. Für ihre Analyse wurde das Transmission-Spektroskopie Verfahren verwendet. In Sedaghati et al. (2017) wurden Transmission-Spektroskopie FORS2 Archivdaten aus der ESO Datenbank benutzt. Diese Daten beinhalten systematische Effekte die durch das Verwenden von älteren, degradierten Prismen des atmosphärischen Dispersion Korrektors entstehen. Mit der Gauss-Prozess Methode wird korreliertes Rauschen in der Transit-Lichtkurve des Exopläneten WASP-80b modelliert und der Beitrag der verschiedenen Quellen von rotem Rauschen abgeschätzt. Die Präsenz von Molekülen führt zu gesteigerter Absorption im infraroten Bereich. Aus diesem Grund werden diese aus dem Transmission Spektrum herausgerechnet. Neutrales, atomares Kalium konnte sowohl im Spektrallinienkern als auch im druckverbreiterten Flügel nachgewiesen werden. Beide Ergebnisse sind statistisch signifikant (>> 5σ ). In Sedaghati et al. (2015) werden die Fortschritte der Transmissions-Spektroskopie mit dem FORS2 Instrument am VLT vorgestellt und damit neuer Antrieb für die Nutzung dieses Instruments für solche Beobachtungen geliefert. Seitdem gibt es eine beispiellose Anzahl an Publikationen, welche eine Vielzahl an exo-atmosphärischen Entdeckungen mit diesem Instrument melden. In der Studie, welche momentan geprüft wird, werden WASP-19b Messungen aus den vorhergehenden Arbeiten benutzt und mit zwei weiteren Messungen im nahen UV und IR Bereichs mit Gitterprismen des FOR2 Instruments gekoppelt. Damit entsteht ein vollständiges optisches und hoch aufgelöstes Transmissions Spektrum dieses Planeten. Mit Hilfe von spezialisierten Beobachtungs- und Analysetechniken, sowie atmosph ärischen Wiedergewinnungsverfahren, ist dies die erste signifi kante Beobachtung von Metalloxid (TiO) in der Atmosphäre von Exoplaneten. Dieser Fund wirft neues Licht auf "hot exo-atmosphere thermal inversion" Theorien. Zusätzlich können signifikante Mengen von H2O und stark streuendem Dunst beobachtet werden. In Sedaghati et al. (2016) wird eine ausführliche Studie der Atmosphäre von WASP-17b dargestellt. Von WASP-17b wird erwartet, dass er eines der größten atmosphärischen Signale in Transmission hat. In dieser Arbeit wird die Präsenz von Kalium in der oberen Atmosph äre signifi kant nachgewiesen durch verstärkte Absorption im druckverbreiterten Linienflügel der Spektrallinie. Zusätzlich gibt es marginale Anzeichen für die Präsenz von Natrium in der Atmosphäre. Dies wurde bereits in einer anderen Studie festgestellt. Die hier präsentierten Arbeiten liefern einen wertvollen Beitrag zu sehr eingeschränkten Proben von exoplanetaren Atmosphären. Sie sind ein Maßstab für einen optimalen Einsatz des bodengebundenen Transmission-Spektroskopie Verfahrens und beweisen das Potential des FORS2 Instruments am VLT für solche Studien. Diese Methode liefert einen konservativen, durchgehend realistischen Ansatz zur Abschätzung der Parameter Genauigkeit unter Berücksichtigung von systematischem Rauschen mit einer nicht-parametrisiertem Methode. Daraus folgt, dass jegliche These die in dieser Arbeit dargestellt wird eine statistisch robuste Entdeckung darstellt

The Aligned Orbit of the Eccentric Proto Hot Jupiter TOI-3362b

High-eccentricity tidal migration predicts the existence of highly eccentric proto hot Jupiters on the “tidal circularization track,” meaning that they might eventually become hot Jupiters, but that their migratory journey remains incomplete. Having experienced moderate amounts of tidal evolution of their orbital elements, proto hot Jupiter systems can be powerful test beds for the underlying mechanisms of eccentricity growth. Notably, they may be used for discriminating between variants of high-eccentricity migration, each predicting a distinct evolution of misalignment between the star and the planet’s orbit. We constrain the spin–orbit misalignment of the proto hot Jupiter TOI-3362b with high-precision radial-velocity observations using ESPRESSO at Very Large Telescope. The observations reveal a sky-projected obliquity $\lambda ={1.2}_{-2.7}^{+2.8}$ ° and constrain the orbital eccentricity to e = 0.720 ± 0.016, making it one of the most eccentric gas giants for which the obliquity has been measured. Although the large eccentricity and the striking orbit alignment of the planet are puzzling, we suggest that ongoing coplanar high-eccentricity migration driven by a distant companion is a possible explanation for the system's architecture. This distant companion would need to reside beyond 5 au at 95% confidence to be compatible with the available radial-velocity observations