13 research outputs found
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 m binned transmission spectrum, between 0.74 and 1.0
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 ().
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 m bin light curves (). 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
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 (
deg), which is particularly puzzling given its significant eccentricity (). 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 ( and 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
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 7.7Ï), a strongly scattering haze (7.4Ï) and sodium (3.4Ï), and confirms the presence of water (7.9Ï) in the atmosphere
Entdecken von fremden LuftrÀumen : Ermittlung und Charakterisierung der AtmosphÀren 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 ( >> 5Ï ).
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 groĂartige Fortschritte im Verstehen und Unterscheiden ihrer physikalischen Eigenschaften. Von all diesen ist die AtmosphĂ€re die wahrscheinlich interessanteste. Wir erhalten nicht nur ein besseres VerstĂ€ndnis vom Inneren des Planeten, seiner Entstehungsprozesse und seiner Geschichte, sondern auch zusĂ€tzliche Informationen ĂŒber mögliche Zeichen von biologischem Leben.
Die vorliegende kumulative Arbeit beleuchtet haupts Ă€chlich die Resultate von drei bereits publizierten Erstautor Schriften, sowie einer, sich derzeit noch im Review Prozess befindlichen, weiteren Studie. Alle hier prĂ€sentierten Arbeiten beschĂ€ftigen sich mit den AtmosphĂ€ren von drei Exoplaneten im sogenannten "hot Jupiter" Regime. FĂŒr 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 Àlteren, degradierten Prismen des atmosphÀrischen Dispersion Korrektors entstehen. Mit der Gauss-Prozess Methode wird korreliertes Rauschen in der Transit-Lichtkurve des ExoplÀneten WASP-80b modelliert und der Beitrag der verschiedenen Quellen von rotem Rauschen abgeschÀtzt.
Die PrĂ€senz von MolekĂŒlen fĂŒhrt 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 FlĂŒgel nachgewiesen werden. Beide Ergebnisse sind statistisch signifikant (>> 5Ï ).
In Sedaghati et al. (2015) werden die Fortschritte der Transmissions-Spektroskopie mit dem FORS2 Instrument am VLT vorgestellt und damit neuer Antrieb fĂŒr die Nutzung dieses Instruments fĂŒr solche Beobachtungen geliefert. Seitdem gibt es eine beispiellose Anzahl an Publikationen, welche eine Vielzahl an exo-atmosphĂ€rischen Entdeckungen mit diesem Instrument melden. In der Studie, welche momentan geprĂŒft 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 vollstĂ€ndiges optisches und hoch aufgelöstes Transmissions Spektrum dieses Planeten. Mit Hilfe von spezialisierten Beobachtungs- und Analysetechniken, sowie atmosph Ă€rischen Wiedergewinnungsverfahren, ist dies die erste signifi kante Beobachtung von Metalloxid (TiO) in der AtmosphĂ€re von Exoplaneten. Dieser Fund wirft neues Licht auf "hot exo-atmosphere thermal inversion" Theorien. ZusĂ€tzlich können signifikante Mengen von H2O und stark streuendem Dunst beobachtet werden.
In Sedaghati et al. (2016) wird eine ausfĂŒhrliche Studie der AtmosphĂ€re von WASP-17b dargestellt. Von WASP-17b wird erwartet, dass er eines der gröĂten atmosphĂ€rischen Signale in Transmission hat. In dieser Arbeit wird die PrĂ€senz von Kalium in der oberen Atmosph Ă€re signifi kant nachgewiesen durch verstĂ€rkte Absorption im druckverbreiterten LinienflĂŒgel der Spektrallinie. ZusĂ€tzlich gibt es marginale Anzeichen fĂŒr die PrĂ€senz von Natrium in der AtmosphĂ€re. Dies wurde bereits in einer anderen Studie festgestellt.
Die hier prĂ€sentierten Arbeiten liefern einen wertvollen Beitrag zu sehr eingeschrĂ€nkten Proben von exoplanetaren AtmosphĂ€ren. Sie sind ein MaĂstab fĂŒr einen optimalen Einsatz des bodengebundenen Transmission-Spektroskopie Verfahrens und beweisen das Potential des FORS2 Instruments am VLT fĂŒr solche Studien. Diese Methode liefert einen konservativen, durchgehend realistischen Ansatz zur AbschĂ€tzung der Parameter Genauigkeit unter BerĂŒcksichtigung von systematischem Rauschen mit einer nicht-parametrisiertem Methode. Daraus folgt, dass jegliche These die in dieser Arbeit dargestellt wird eine statistisch robuste Entdeckung darstellt
Personalbestand an Hochschulen der ehemaligen DDR 1989 und 1990
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