Obliquity measurement and atmospheric characterisation of the WASP-74 planetary system

We present new transit observations of the hot Jupiter WASP-74 b (Teq ~ 1860 K) using the high-resolution spectrograph HARPS-N and the multi-colour simultaneous imager MuSCAT2. We refined the orbital properties of the planet and its host star and measured its obliquity for the first time. The measured sky-projected angle between the stellar spin-axis and the orbital axis of the planet is compatible with an orbit that is well-aligned with the equator of the host star (λ = 0.77 ± 0.99 deg). We are not able to detect any absorption feature of Hα or any other atomic spectral features in the high-resolution transmission spectra of this source owing to low S/N at the line cores. Despite previous claims regarding the presence of strong optical absorbers such as TiO and VO gases in the atmosphere of WASP-74 b, new ground-based photometry combined with a reanalysis of previously reported observations from the literature show a slope in the low-resolution transmission spectrum that is steeper than expected from Rayleigh scattering alone.

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A comprehensive study of the WASP-74 planetary system

10.5194/epsc2020-399 ◽

2020 ◽

Author(s):

Rafael Luque ◽

Keyword(s):

High Resolution ◽

Transmission Spectrum ◽

Rayleigh Scattering ◽

Near Infrared ◽

Planetary System ◽

Spin Axis ◽

Physical Parameters ◽

First Time ◽

Orbital Axis ◽

Comprehensive Study

<p>In this work, we present new transit observations of the hot Jupiter WASP-74 b using the high-resolution spectrograph HARPS-N and the multi-color simultaneous imager MuSCAT2. The new data allow us to refine the orbital properties of the planet, the physical parameters of the host star, and reveal some properties about the planet's atmosphere using different techniques. We measure, for the first time, the sky-projected angle between the stellar spin-axis and the planet&#8217;s orbital axis, which is compatible with an orbit well-aligned with the equator of the host star. We build up an observational low-resolution transmission spectrum from the optical to the near-infrared of the planet using all the available transit photometry for this planet. Our joint reanalysis shows a slope in the transmission spectrum steeper than expected from Rayleigh scattering alone and no signs of strong optical absorbers such as TiO and/or VO, in disagreement with previous claims of the presence of these gases in the atmosphere of WASP-74 b.</p>

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The GTC exoplanet transit spectroscopy survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834063 ◽

2019 ◽

Vol 622 ◽

pp. A172 ◽

Cited By ~ 7

Author(s):

F. Murgas ◽

G. Chen ◽

E. Pallé ◽

L. Nortmann ◽

G. Nowak

Keyword(s):

Transmission Spectrum ◽

Rayleigh Scattering ◽

Extrasolar Planets ◽

Light Curves ◽

Data Sets ◽

Transmission Spectra ◽

Data Set ◽

Systematic Effects ◽

The Individual ◽

Spectrum Slope

Context. Rayleigh scattering in a hydrogen-dominated exoplanet atmosphere can be detected using ground- or space-based telescopes. However, stellar activity in the form of spots can mimic Rayleigh scattering in the observed transmission spectrum. Quantifying this phenomena is key to our correct interpretation of exoplanet atmospheric properties. Aims. We use the ten-meter Gran Telescopio Canarias (GTC) telescope to carry out a ground-based transmission spectra survey of extrasolar planets to characterize their atmospheres. In this paper we investigate the exoplanet HAT-P-11b, a Neptune-sized planet orbiting an active K-type star. Methods. We obtained long-slit optical spectroscopy of two transits of HAT-P-11b with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) on August 30, 2016 and September 25, 2017. We integrated the spectrum of HAT-P-11 and one reference star in several spectroscopic channels across the λ ~ 400–785 nm region, creating numerous light curves of the transits. We fit analytic transit curves to the data taking into account the systematic effects and red noise present in the time series in an effort to measure the change of the planet-to-star radius ratio (Rp∕Rs) across wavelength. Results. By fitting both transits together, we find a slope in the transmission spectrum showing an increase of the planetary radius towards blue wavelengths. Closer inspection of the transmission spectrum of the individual data sets reveals that the first transit presents this slope while the transmission spectrum of the second data set is flat. Additionally, we detect hints of Na absorption on the first night, but not on the second. We conclude that the transmission spectrum slope and Na absorption excess found in the first transit observation are caused by unocculted stellar spots. Modeling the contribution of unocculted spots to reproduce the results of the first night we find a spot filling factor of δ = 0.62−0.17+0.20 and a spot-to-photosphere temperature difference of ΔT = 429−299+184 K.

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A Discussion on solar studies with special reference to space observations - A high resolution solar ultraviolet spectrum between 200 and 220 nm

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1971.0057 ◽

1971 ◽

Vol 270 (1202) ◽

pp. 29-46 ◽

Cited By ~ 8

Keyword(s):

High Resolution ◽

Solar Spectrum ◽

Ultraviolet Spectrum ◽

Absorption Feature ◽

Intensity Analysis ◽

Echelle Spectrograph ◽

Broad Absorption ◽

First Time ◽

Solar Ultraviolet ◽

The Continuum

A high resolution solar spectrum in the range 200 to 220 nm has been recorded with an echelle spectrograph launched in, a sun-pointing Skylark rocket. The data have been reduced and are presented as intensity-wavelength plots together with a wavelength list and proposed identifications. A broad absorption feature at 212.4 nm is assigned to a single source and an intensity analysis confirms this to be the non-resonance Sii line at 212.412 nm. The discontinuity in the continuum intensity near 208.7 nm is revealed with high resolution for the first time and is assigned to the photoionization edge of A11. An analysis shows that its intensity drop and wavelength position can only be explained by adjustments to the solar model in the region 0.001 < T 5000 < 0.2.

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Widest broadband transmission spectra (0.38-1.71 micrometer) obtained through ground based chromatic Rossiter-McLaughlin observations

10.5194/epsc2020-352 ◽

2020 ◽

Author(s):

Mahmoudreza Oshagh

Keyword(s):

Rayleigh Scattering ◽

Active Regions ◽

Spectroscopic Observation ◽

Visible Range ◽

Transmission Spectra ◽

Activity Effect ◽

Crucial Information ◽

Temperature Contrast ◽

The One ◽

First Time

<pre class="moz-quote-pre">Transmission spectroscopy has been proven to be the most powerful technique in detecting and characterizing atmospheres of exoplanets. So far, mostly ground and space-based multi-band transit photometry have been used to retrieve the exoplanets&#039; broadband transmission spectra. An alternative technique has been proposed for retrieving the broadband transmission spectra using chromatic Rossiter-McLaughlin observation. This technique has been used only once for exoplanet HD189733b using HARPS observation in the visible range. I will present the result we obtained from our new CARMENES spectroscopic observation (both VIS and NIR arms) during one transit of HD189733b. We found a strong agreement between the retrieved transmission spectra from CARMENES and HARPS in the overlapping wavelength range. By combining HARPS and CARMENES VIS and NIR observations, for the first time, we obtained the widest broadband transmission spectra from ground-based observations which is comparable to the one obtained from HST and Spitzer observations. We found a clear signature of haze in the atmosphere of HD189733b as indicated by the presence of Rayleigh scattering slope in transmission spectra, however our result suggested much hazier atmosphere in comparison to the previous studies. Moreover, we demonstrated how a single transit CARMENES observation could provide important information about the stellar active regions&#8217; properties (such as their temperature contrast), which are crucial information in order to mitigate the stellar activity effect on the retrieved transmission spectra.</pre>

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High-resolution transmission spectrum of the Earth's atmosphere-seeing Earth as an exoplanet using a lunar eclipse

International Journal of Astrobiology ◽

10.1017/s1473550414000172 ◽

2014 ◽

Vol 14 (2) ◽

pp. 255-266 ◽

Cited By ~ 20

Author(s):

F. Yan ◽

R. A. E. Fosbury ◽

M. G. Petr-Gotzens ◽

G. Zhao ◽

W. Wang ◽

...

Keyword(s):

High Resolution ◽

Water Vapour ◽

Transmission Spectrum ◽

Atmospheric Model ◽

High Signal ◽

Absorption Feature ◽

Lunar Eclipse ◽

Atmospheric Transmission ◽

Earth’S Atmosphere ◽

Earth's Atmosphere

AbstractWith the rapid developments in the exoplanet field, more and more terrestrial exoplanets are being detected. Characterizing their atmospheres using transit observations will become a key datum in the quest for detecting an Earth-like exoplanet. The atmospheric transmission spectrum of our Earth will be an ideal template for comparison with future exo-Earth candidates. By observing a lunar eclipse, which offers a similar configuration to that of an exoplanet transit, we have obtained a high-resolution and high signal-to-noise ratio (SNR) transmission spectrum of the Earth's atmosphere. This observation was performed with the High Resolution Spectrograph at Xinglong Station, China during the total lunar eclipse in December 2011. We compare the observed transmission spectrum with our atmospheric model, and determine the characteristics of the various atmospheric species in detail. In the transmission spectrum, O2, O3, O2 · O2, NO2 and H2O are detected, and their column densities are measured and compared with the satellites data. The visible Chappuis band of ozone produces the most prominent absorption feature, which suggests that ozone is a promising molecule for the future exo-Earth characterization. Due to the high resolution and high SNR of our spectrum, several novel details of the Earth atmosphere's transmission spectrum are presented. The individual O2 lines are resolved and O2 isotopes are clearly detected. Our new observations do not confirm the absorption features of Ca II or Na I which have been reported in previous lunar eclipse observations. However, features in these and some other strong Fraunhofer line positions do occur in the observed spectrum. We propose that these are due to a Raman-scattered component in the forward-scattered sunlight appearing in the lunar umbral spectrum. Water vapour absorption is found to be rather weak in our spectrum because the atmosphere we probed is relatively dry, which prompts us to discuss the detectability of water vapour in Earth-like exoplanet atmospheres.

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Absorption Spectra of the Prototype Hot-Jupiters: determination of atmospheric constituents and structure

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308027130 ◽

2008 ◽

Vol 4 (S253) ◽

pp. 532-535 ◽

Cited By ~ 1

Author(s):

David K. Sing ◽

A. Lecavelier ◽

J.-M. Désert ◽

A. Vidal-Madjar ◽

G. Ballester

Keyword(s):

High Temperature ◽

Molecular Species ◽

Transmission Spectrum ◽

Optical Transmission ◽

Rayleigh Scattering ◽

Transmission Spectra ◽

Hot Jupiters ◽

Transmission Spectrum Analysis ◽

Pressure Altitude

AbstractThe two prototype hot-Jupiter exoplanets HD209458b and HD189733b are currently offering an unprecedented view of their atmospheres. As discussed here, primary transit transmission spectra provide the opportunity to identify specific atomic and molecular species, determine their abundances, and recover temperature-pressure-altitude information. We present a reanalysis of existing HST/STIS data on HD209458b, providing a complete optical transmission spectrum. Analysis of this spectrum have revealed: (1) the planetary abundance of sodium which is ~2X solar (2) a depletion of sodium at high altitudes due to condensation or ionization (3) Rayleigh scattering by H2 (3) a high temperature at pressures of 10's mbar consistent with the dayside inversion (4) a separate high-altitude hot temperature from the planet's thermosphere and (5) likely absorption by TiO/VO. While HD209458b and HD189733b are currently the best candidates for these studies, another ~10 exoplanets are good targets with today's instruments for future transmission-based atmospheric detections.

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Stellar contributions to the line profiles of high-resolution transmission spectra of exoplanets

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833415 ◽

2018 ◽

Vol 617 ◽

pp. A134 ◽

Cited By ~ 4

Author(s):

F. Borsa ◽

A. Zannoni

Keyword(s):

High Resolution ◽

Line Profile ◽

Transmission Spectrum ◽

Signal To Noise Ratio ◽

Transmission Spectra ◽

Line Profiles ◽

Stellar Rotation ◽

Stellar Spectra ◽

Exoplanetary Atmospheres ◽

Sophisticated Analysis

Context. In-depth studies of exoplanetary atmospheres are starting to become reality. In order to unveil their properties in detail, we need spectra with a higher signal-to-noise ratio (S/N) and also more sophisticated analysis methods. Aims. With high-resolution spectrographs, we can not only detect the sodium feature in the atmosphere of exoplanets, but also characterize it by studying its line profile. After finding a clearly w-shaped sodium line profile in the transmission spectrum of HD 189733b, we investigated the possible sources of contamination given by the star and tried to correct for these spurious deformations. Methods. By analyzing the single transmission spectra of HD 189733b in the wavelength space, we show that the main sodium signal that causes the absorption in the transmission spectrum is centered on the stellar rest frame. We concentrate on two main stellar effects that contaminate the exoplanetary transmission spectrum: center-to-limb variations (CLVs) and stellar rotation. We show the effects on the line profile: while we correct for the CLV using simulated theoretical stellar spectra, we provide a new method, based directly on observational data, to correct for the Rossiter–McLaughlin contribution to the line profile of the retrieved transmission spectrum. Results. We apply the corrections to the spectra of HD 189733b. Our analysis shows line profiles of the Na D lines in the transmission spectrum that are narrower than reported previously. The correction of the sodium D2 line, which is deeper than the D1 line, is probably still incomplete since the planetary radius is larger at this wavelength. A careful detrending from spurious stellar effects followed by an inspection in the velocity space is mandatory when studying the line profile of atmospheric features in the high-resolution transmission spectrum of exoplanets. Since the line profile is used to retrieve atmospheric properties, the resulting atmospheric parameters could be incorrectly estimated when the stellar contamination is not corrected for. Data with higher S/N coupled with improved atmospheric models will allow us to adapt the magnitude of the corrections of stellar effects in an iterative way.

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Revisiting the atmosphere of HD 209458b with HARPS-N, CARMENES and ESPRESSO

10.5194/epsc2020-811 ◽

2020 ◽

Author(s):

Núria Casasayas-Barris ◽

Enric Palle ◽

Monika Stangret ◽

Guo Chen ◽

Fei Yan ◽

...

Keyword(s):

High Resolution ◽

Time Evolution ◽

Transmission Spectrum ◽

State Of The Art ◽

Signal To Noise Ratio ◽

Light Curves ◽

High Resolution Spectroscopy ◽

Transmission Spectra ◽

Signal To Noise ◽

Transmission Spectroscopy

<p>HD 209458b was the first transiting planet discovered, and the first for which its atmosphere, in particular Na I, was detected. With time, it has become one of the most studied planets, with a large diversity of atmospheric studies using low- and high-resolution spectroscopy. Here, we present the analysis of high-resolution transmission spectroscopy of HD 209458b using a total of five transit observations with HARPS-N and CARMENES spectrographs. In contrast to previous studies where atmospheric Na I absorption is detected, we find that, for all of the nights, either individually or combined, the transmission spectra can be explained by the combination of the centre-to-limb variation and the Rossiter-McLaughlin effect. Thus, the transmission spectrum reveals no detectable Na I absorption in HD 209458b. This is also observed in the time-evolution maps and transmission light curves, but at lower signal-to-noise ratio. Other strong lines such as H&#945;, Ca II IRT, the Mg I triplet region, and K I D1 are analysed, and are also consistent with the modelled effects, without considering any contribution from the exoplanet atmosphere. New ESPRESSO observations, with state-of-the-art stability and considerably larger signal-to-noise, confirm the results of our study and will also be shown.</p>

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Broadband transmission spectroscopy of HD 209458b with ESPRESSO: evidence for Na, TiO, or both

Astronomy and Astrophysics ◽

10.1051/0004-6361/202039454 ◽

2020 ◽

Vol 644 ◽

pp. A51

Author(s):

N. C. Santos ◽

E. Cristo ◽

O. Demangeon ◽

M. Oshagh ◽

R. Allart ◽

...

Keyword(s):

High Resolution ◽

Transmission Spectrum ◽

Optical Spectrum ◽

High Resolution Spectroscopy ◽

Transmission Spectra ◽

Full Dataset ◽

Synthetic Spectra ◽

Observational Errors ◽

The One

Context. The detection and characterization of exoplanet atmospheres is currently one of the main drivers pushing the development of new observing facilities. In this context, high-resolution spectrographs are proving their potential and showing that high-resolution spectroscopy will be paramount in this field. Aims. We aim to make use of ESPRESSO high-resolution spectra, which cover two transits of HD 209458b, to probe the broadband transmission optical spectrum of the planet. Methods. We applied the chromatic Rossiter–McLaughin method to derive the transmission spectrum of HD 209458b. We compared the results with previous HST observations and with synthetic spectra. Results. We recover a transmission spectrum of HD 209458b similar to the one obtained with HST data. The models suggest that the observed signal can be explained by only Na, only TiO, or both Na and TiO, even though none is fully capable of explaining our observed transmission spectrum. Extra absorbers may be needed to explain the full dataset, though modeling approximations and observational errors can also be responsible for the observed mismatch. Conclusions. Using the chromatic Rossiter–McLaughlin technique, ESPRESSO is able to provide broadband transmission spectra of exoplanets from the ground, in conjunction with space-based facilities, opening good perspectives for similar studies of other planets.

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The GTC exoplanet transit spectroscopy survey

Astronomy and Astrophysics ◽

10.1051/0004-6361/201731113 ◽

2018 ◽

Vol 609 ◽

pp. A33 ◽

Cited By ~ 5

Author(s):

H. Parviainen ◽

E. Pallé ◽

G. Chen ◽

L. Nortmann ◽

F. Murgas ◽

...

Keyword(s):

High Altitude ◽

Transmission Spectrum ◽

Rayleigh Scattering ◽

Equilibrium Temperature ◽

Transmission Spectra ◽

Spectroscopy Analysis ◽

Orbital Parameters ◽

Transmission Spectroscopy ◽

The Common ◽

20 Nm

Aims. We set out to study the atmosphere of WASP-80b, a warm inflated gas giant with an equilibrium temperature of ~800 K, using ground-based transmission spectroscopy covering the spectral range from 520 to 910 nm. The observations allow us to probe the existence and abundance of K and Na in WASP-80b’s atmosphere, existence of high-altitude clouds, and Rayleigh-scattering in the blue end of the spectrum. Methods. We observed two spectroscopic time series of WASP-80b transits with the OSIRIS spectrograph installed in the Gran Telescopio Canarias (GTC), and use the observations to estimate the planet’s transmission spectrum between 520 nm and 910 nm in 20 nm-wide passbands, and around the K I and Na I resonance doublets in 6 nm-wide passbands. We jointly model three previously published broadband datasets consisting of 27 light curves, prior to a transmission spectroscopy analysis in order to obtain improved estimates of the planet’s orbital parameters, average radius ratio, and stellar density. The parameter posteriors from the broadband analysis are used to set informative priors on the transmission spectroscopy analysis. The final transmission spectroscopy analyses are carried out jointly for the two nights using a divide-by-white approach to remove the common-mode systematics, and Gaussian processes to model the residual wavelength-dependent systematics. Results. We recover a flat transmission spectrum with no evidence of Rayleigh scattering or K I or Na I absorption, and obtain an improved system characterisation as a by-product of the broadband- and GTC-dataset modelling. The transmission spectra estimated separately from the two observing runs are consistent with each other, as are the transmission spectra estimated using either a parametric or nonparametric systematics model. The flat transmission spectrum favours an atmosphere model with high-altitude clouds over cloud-free models with stellar or sub-stellar metallicities. Conclusions. Our results disagree with the recently published discovery of strong K I absorption in WASP-80b’s atmosphere based on ground-based transmission spectroscopy with FORS2 at VLT.

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