scholarly journals The GAPS programme at TNG

2020 ◽  
Vol 639 ◽  
pp. A49 ◽  
Author(s):  
G. Guilluy ◽  
V. Andretta ◽  
F. Borsa ◽  
P. Giacobbe ◽  
A. Sozzetti ◽  
...  
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Magnetic Activity ◽  
Stellar Activity ◽  
Absorption Signal ◽  
Metastable Helium ◽  
Transmission Spectroscopy ◽  
Width Measurements ◽  
In Transit ◽  
The Impact

Context. Exoplanets orbiting very close to their parent star are strongly irradiated. This can lead the upper atmospheric layers to expand and evaporate into space. The metastable helium (He I) triplet at 1083.3 nm has recently been shown to be a powerful diagnostic to probe extended and escaping exoplanetary atmospheres. Aims. We perform high-resolution transmission spectroscopy of the transiting hot Jupiter HD 189733 b with the GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo, taking advantage of the simultaneous optical+near infrared spectral coverage to detect He I in the planet’s extended atmosphere and to gauge the impact of stellar magnetic activity on the planetary absorption signal. Methods. Observations were performed during five transit events of HD 189733 b. By comparison of the in-transit and out-of-transit GIANO-B observations, we computed high-resolution transmission spectra. We then used them to perform equivalent width measurements and carry out light-curves analyses in order to consistently gauge the excess in-transit absorption in correspondence with the He I triplet. Results. We spectrally resolve the He I triplet and detect an absorption signal during all five transits. The mean in-transit absorption depth amounts to 0.75 ± 0.03% (25σ) in the core of the strongest helium triplet component. We detect night-to-night variations in the He I absorption signal likely due to the transit events occurring in the presence of stellar surface inhomogeneities. We evaluate the impact of stellar-activity pseudo-signals on the true planetary absorption using a comparative analysis of the He I 1083.3 nm (in the near-infrared) and the Hα (in the visible) lines. Using a 3D atmospheric code, we interpret the time series of the He I absorption lines in the three nights not affected by stellar contamination, which exhibit a mean in-transit absorption depth of 0.77 ± 0.04% (19σ) in full agreement with the one derived from the full dataset. In agreement with previous results, our simulations suggest that the helium layers only fill part of the Roche lobe. Observations can be explained with a thermosphere heated to ~12 000 K, expanding up to ~1.2 planetary radii, and losing ~1 g s−1 of metastable helium. Conclusions. Our results reinforce the importance of simultaneous optical plus near infrared monitoring when performing high-resolution transmission spectroscopy of the extended and escaping atmospheres of hot planets in the presence of stellar activity.

scholarly journals The CARMENES search for exoplanets around M dwarfs

2020 ◽  
Vol 642 ◽  
pp. A22 ◽  
Author(s):  
V. M. Passegger ◽  
A. Bello-García ◽  
J. Ordieres-Meré ◽  
J. A. Caballero ◽  
A. Schweitzer ◽  
...  
Keyword(s):  
Neural Network ◽  
High Resolution ◽  
Network Architecture ◽  
Near Infrared ◽  
Rotational Velocity ◽  
M Dwarfs ◽  
Convolutional Network ◽  
Fast Analysis ◽  
Infrared Wavelength ◽  
The Impact

Existing and upcoming instrumentation is collecting large amounts of astrophysical data, which require efficient and fast analysis techniques. We present a deep neural network architecture to analyze high-resolution stellar spectra and predict stellar parameters such as effective temperature, surface gravity, metallicity, and rotational velocity. With this study, we firstly demonstrate the capability of deep neural networks to precisely recover stellar parameters from a synthetic training set. Secondly, we analyze the application of this method to observed spectra and the impact of the synthetic gap (i.e., the difference between observed and synthetic spectra) on the estimation of stellar parameters, their errors, and their precision. Our convolutional network is trained on synthetic PHOENIX-ACES spectra in different optical and near-infrared wavelength regions. For each of the four stellar parameters, Teff, log g, [M/H], and v sin i, we constructed a neural network model to estimate each parameter independently. We then applied this method to 50 M dwarfs with high-resolution spectra taken with CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Échelle Spectrographs), which operates in the visible (520–960 nm) and near-infrared wavelength range (960–1710 nm) simultaneously. Our results are compared with literature values for these stars. They show mostly good agreement within the errors, but also exhibit large deviations in some cases, especially for [M/H], pointing out the importance of a better understanding of the synthetic gap.

scholarly journals Detection of He I λ10830 Å absorption on HD 189733 b with CARMENES high-resolution transmission spectroscopy

2018 ◽  
Vol 620 ◽  
pp. A97 ◽  
Author(s):  
M. Salz ◽  
S. Czesla ◽  
P. C. Schneider ◽  
E. Nagel ◽  
J. H. M. M. Schmitt ◽  
...  
Keyword(s):  
High Resolution ◽  
Rest Frame ◽  
Near Infrared ◽  
Radial Velocities ◽  
Helium Atmosphere ◽  
Absorption Signal ◽  
The Mean ◽  
Third Line ◽  
Calar Alto ◽  
Absorption Level

We present three transit observations of HD 189733 b obtained with the high-resolution spectrograph CARMENES at Calar Alto. A strong absorption signal is detected in the near-infrared He I triplet at 10830 Å in all three transits. During mid-transit, the mean absorption level is 0.88 ± 0.04% measured in a ±10 km s−1 range at a net blueshift of − 3.5 ± 0.4 km s−1 (10829.84–10830.57 Å). The absorption signal exhibits radial velocities of + 6.5 ± 3.1 km s−1 and − 12.6 ± 1.0 km s−1 during ingress and egress, respectively; all radial velocities are measured in the planetary rest frame. We show that stellar activity related pseudo-signals interfere with the planetary atmospheric absorption signal. They could contribute as much as 80% of the observed signal and might also affect the observed radial velocity signature, but pseudo-signals are very unlikely to explain the entire signal. The observed line ratio between the two unresolved and the third line of the He I triplet is 2.8 ± 0.2, which strongly deviates from the value expected for an optically thin atmospheres. When interpreted in terms of absorption in the planetary atmosphere, this favors a compact helium atmosphere with an extent of only 0.2 planetary radii and a substantial column density on the order of 4 × 1012 cm−2. The observed radial velocities can be understood either in terms of atmospheric circulation with equatorial superrotation or as a sign of an asymmetric atmospheric component of evaporating material. We detect no clear signature of ongoing evaporation, like pre- or post-transit absorption, which could indicate material beyond the planetary Roche lobe, or radial velocities in excess of the escape velocity. These findings do not contradict planetary evaporation, but only show that the detected helium absorption in HD 189733 b does not trace the atmospheric layers that show pronounced escape signatures.

scholarly journals Stellar atmospheric parameters of FGK-type stars from high-resolution optical and near-infrared CARMENES spectra

2020 ◽  
Vol 492 (4) ◽  
pp. 5470-5507
Author(s):  
E Marfil ◽  
H M Tabernero ◽  
D Montes ◽  
J A Caballero ◽  
M G Soto ◽  
...  
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Signal To Noise Ratio ◽  
Wavelength Region ◽  
Infrared Region ◽  
High Signal ◽  
Atmospheric Parameters ◽  
Infrared Wavelength ◽  
The Impact ◽  
Higher Sensitivity

ABSTRACT With the purpose of assessing classic spectroscopic methods on high-resolution and high signal-to-noise ratio spectra in the near-infrared wavelength region, we selected a sample of 65 F-, G-, and K-type stars observed with CARMENES, the new, ultra-stable, double-channel spectrograph at the 3.5 m Calar Alto telescope. We computed their stellar atmospheric parameters (Teff, log g, ξ, and [Fe/H]) by means of the stepar code, a python implementation of the equivalent width method that employs the 2017 version of the moog code and a grid of MARCS model atmospheres. We compiled four Fe i and Fe ii line lists suited to metal-rich dwarfs, metal-poor dwarfs, metal-rich giants, and metal-poor giants that cover the wavelength range from 5300 to 17 100 Å, thus substantially increasing the number of identified Fe i and Fe ii lines up to 653 and 23, respectively. We examined the impact of the near-infrared Fe i and Fe ii lines upon our parameter determinations after an exhaustive literature search, placing special emphasis on the 14 Gaia benchmark stars contained in our sample. Even though our parameter determinations remain in good agreement with the literature values, the increase in the number of Fe i and Fe ii lines when the near-infrared region is taken into account reveals a deeper Teff scale that might stem from a higher sensitivity of the near-infrared lines to Teff.

scholarly journals Combining visible and infrared radiometry and lidar data to test simulations in clear and ice cloud conditions

2010 ◽  
Vol 10 (15) ◽  
pp. 7369-7387 ◽  
Author(s):  
A. Bozzo ◽  
T. Maestri ◽  
R. Rizzi
Keyword(s):  
High Resolution ◽  
Optical Depth ◽  
Near Infrared ◽  
Natural Variability ◽  
Cloud Optical Depth ◽  
Cloud Parameters ◽  
Modeling Methodology ◽  
Particles Size Distribution ◽  
Spectral Data Analysis ◽  
The Impact

Abstract. Measurements taken during the 2003 Pacific THORPEX Observing System Test (P-TOST) by the MODIS Airborne Simulator (MAS), the Scanning High-resolution Interferometer Sounder (S-HIS) and the Cloud Physics Lidar (CPL) are compared to simulations performed with a line-by-line and multiple scattering modeling methodology (LBLMS). Formerly used for infrared hyper-spectral data analysis, LBLMS has been extended to the visible and near infrared with the inclusion of surface bi-directional reflectance properties. A number of scenes are evaluated: two clear scenes, one with nadir geometry and one cross-track encompassing sun glint, and three cloudy scenes, all with nadir geometry. CPL data is used to estimate the particulate optical depth at 532 nm for the clear and cloudy scenes and cloud upper and lower boundaries. Cloud optical depth is retrieved from S-HIS infrared window radiances, and it agrees with CPL values, to within natural variability. MAS data are simulated convolving high resolution radiances. The paper discusses the results of the comparisons for the clear and cloudy cases. LBLMS clear simulations agree with MAS data to within 20% in the shortwave (SW) and near infrared (NIR) spectrum and within 2 K in the infrared (IR) range. It is shown that cloudy sky simulations using cloud parameters retrieved from IR radiances systematically underestimate the measured radiance in the SW and NIR by nearly 50%, although the IR retrieved optical thickness agree with same measured by CPL. MODIS radiances measured from Terra are also compared to LBLMS simulations in cloudy conditions, using retrieved cloud optical depth and effective radius from MODIS, to understand the origin for the observed discrepancies. It is shown that the simulations agree, to within natural variability, with measurements in selected MODIS SW bands. The impact of the assumed particles size distribution and vertical profile of ice content on results is evaluated. Sensitivity is much smaller than differences between measured and simulated radiances in the SW and NIR. The paper dwells on a possible explanation of these contradictory results, involving the phase function of ice particles in the shortwave.

scholarly journals Role of the impact parameter in exoplanet transmission spectroscopy

2020 ◽  
Vol 640 ◽  
pp. A134
Author(s):  
X. Alexoudi ◽  
M. Mallonn ◽  
E. Keles ◽  
K. Poppenhäger ◽  
C. von Essen ◽  
...  
Keyword(s):  
Impact Parameter ◽  
Transmission Spectrum ◽  
Near Infrared ◽  
Transmission Spectra ◽  
Orbital Parameters ◽  
Transmission Spectroscopy ◽  
Limb Darkening ◽  
The Impact ◽  
Error Envelope

Context. Transmission spectroscopy is a promising tool for the atmospheric characterization of transiting exoplanets. Because the planetary signal is faint, discrepancies have been reported regarding individual targets. Aims. We investigate the dependence of the estimated transmission spectrum on deviations of the orbital parameters of the star-planet system that are due to the limb-darkening effects of the host star. We describe how the uncertainty on the orbital parameters translates into an uncertainty on the planetary spectral slope. Methods. We created synthetic transit light curves in seven different wavelength bands, from the near-ultraviolet to the near-infrared, and fit them with transit models parameterized by fixed deviating values of the impact parameter b. First, we performed a qualitative study to illustrate the effect by presenting the changes in the transmission spectrum slope with different deviations of b. Then, we quantified these variations by creating an error envelope (for centrally transiting, off-center, and grazing systems) based on a derived typical uncertainty on b from the literature. Finally, we compared the variations in the transmission spectra for different spectral types of host stars. Results. Our simulations show a wavelength-dependent offset that is more pronounced at the blue wavelengths where the limb-darkening effect is stronger. This offset introduces a slope in the planetary transmission spectrum that becomes steeper with increasing b values. Variations of b by positive or negative values within its uncertainty interval introduce positive or negative slopes, thus the formation of an error envelope. The amplitude from blue optical to near-infrared wavelength for a typical uncertainty on b corresponds to one atmospheric pressure scale height and more. This impact parameter degeneracy is confirmed for different host types; K stars present prominently steeper slopes, while M stars indicate features at the blue wavelengths. Conclusions. We demonstrate that transmission spectra can be hard to interpret, basically because of the limitations in defining a precise impact parameter value for a transiting exoplanet. This consequently limits a characterization of its atmosphere.

scholarly journals High-resolution confirmation of an extended helium atmosphere around WASP-107b

2019 ◽  
Vol 623 ◽  
pp. A58 ◽  
Author(s):  
R. Allart ◽  
V. Bourrier ◽  
C. Lovis ◽  
D. Ehrenreich ◽  
J. Aceituno ◽  
...  
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Neutral Hydrogen ◽  
Upper Atmosphere ◽  
Dynamical Structure ◽  
Helium Atmosphere ◽  
Metastable Helium ◽  
Exoplanetary Systems ◽  
Formation And Evolution ◽  
Excess Absorption

Context. Probing the evaporation of exoplanet atmospheres is key to understanding the formation and evolution of exoplanetary systems. The main tracer of evaporation in the UV is the Lyman-α transition, which can reveal extended exospheres of neutral hydrogen. Recently, the near-infrared (NIR) metastable helium triplet (10 833 Å) revealed extended thermospheres in several exoplanets. This opens a new window into evaporation. Aims. We aim at spectrally resolving the first helium absorption signature detected in the warm Saturn WASP-107b with the Wide Filed Camera 3 on board the Hubble Space Telescope (HST/WFC3). Methods. We obtained one transit of WASP-107b with CARMENES installed on the 3.5 m telescope at the Calar Alto observatory. Results. We detect an excess helium absorption signature of 5.54 ± 0.27% (20σ) in the planet rest frame during the transit. The detection is in agreement with the previous detection achieved with HST/WFC3. The signature shows an excess absorption in the blue part of the lines, suggesting that He I atoms are escaping from the atmosphere of WASP-107b. We interpret the time-series absorption spectra using the 3D EVE code. Our observations can be explained by combining an extended thermosphere that fills half of the Roche lobe and a large exospheric tail sustained by an escape rate of metastable helium of about 106 g s−1. In this scenario, however, the upper atmosphere needs to be subjected to a reduced photoionisation and radiation pressure from the star for the model to match the observations. Conclusions. We confirm the presence of helium in the atmosphere of WASP-107b at high confidence. The helium feature is detected from space and from the ground. The ground-based high-resolution signal brings detailed information about the spatial and dynamical structure of the upper atmosphere, and simulations suggest that the He I signature of WASP-107b probes both its thermosphere and exosphere, establishing this signature as a robust probe of exoplanetary upper atmospheres. Surveys with NIR high-resolution spectrographs (e.g. CARMENES, the Spectromètre infrarouge (SPIRou), or the Near-Infrared Planet Searcher (NIRPS)) will deliver a statistical understanding of exoplanet thermospheres and exospheres through the helium triplet.

scholarly journals HIGH-RESOLUTION, DIFFERENTIAL, NEAR-INFRARED TRANSMISSION SPECTROSCOPY OF GJ 1214b

2011 ◽  
Vol 736 (2) ◽  
pp. 132 ◽  
Author(s):  
I. J. M. Crossfield ◽  
Travis Barman ◽  
Brad M. S. Hansen
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Infrared Transmission ◽  
Transmission Spectroscopy

scholarly journals The impact of unresolved magnetic spots on high-precision radial velocity measurements

2020 ◽  
Vol 497 (3) ◽  
pp. 4009-4021
Author(s):  
M Lisogorskyi ◽  
S Boro Saikia ◽  
S V Jeffers ◽  
H R A Jones ◽  
J Morin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Radial Velocity ◽  
High Precision ◽  
Large Scale ◽  
Magnetic Activity ◽  
Velocity Measurements ◽  
Stellar Activity ◽  
Solar Type ◽  
Rotating Star ◽  
The Impact

ABSTRACT The Doppler method of exoplanet detection has been extremely successful, but suffers from contaminating noise from stellar activity. In this work, a model of a rotating star with a magnetic field based on the geometry of the K2 star ϵ Eridani is presented and used to estimate its effect on simulated radial velocity (RV) measurements. A number of different distributions of unresolved magnetic spots were simulated on top of the observed large-scale magnetic maps obtained from 8 yr of spectropolarimetric observations. The RV signals due to the magnetic spots have amplitudes of up to 10 m s−1, high enough to prevent the detection of planets under 20 Earth masses in temperate zones of solar-type stars. We show that the RV depends heavily on spot distribution. Our results emphasize that understanding stellar magnetic activity and spot distribution is crucial for the detection of Earth analogues.

scholarly journals Precision radial velocity measurements by the forward-modeling technique in the near-infrared†

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Teruyuki Hirano ◽  
Masayuki Kuzuhara ◽  
Takayuki Kotani ◽  
Masashi Omiya ◽  
Tomoyuki Kudo ◽  
...  
Keyword(s):  
Radial Velocity ◽  
Near Infrared ◽  
Frequency Comb ◽  
Signal To Noise Ratio ◽  
Forward Modeling ◽  
Laser Frequency ◽  
Magnetic Activity ◽  
Modeling Technique ◽  
Reference Spectrum ◽  
The Impact

Abstract Precision radial velocity (RV) measurements in the near-infrared are a powerful tool to detect and characterize exoplanets around low-mass stars or young stars with higher magnetic activity. However, the presence of strong telluric absorption lines and emission lines in the near-infrared that significantly vary in time can prevent extraction of RV information from these spectra by classical techniques, which ignore or mask the telluric lines. We present a methodology and pipeline to derive precision RVs from near-infrared spectra using a forward-modeling technique. We applied this to spectra with a wide wavelength coverage (Y, J, and H bands, simultaneously), taken by the InfraRed Doppler (IRD) spectrograph on the Subaru 8.2 m telescope. Our pipeline extracts the instantaneous instrumental profile of the spectrograph for each spectral segment, based on a reference spectrum of the laser-frequency comb that is injected into the spectrograph simultaneously with the stellar light. These profiles are used to derive the intrinsic stellar template spectrum, which is free from instrumental broadening and telluric features, as well as model and fit individual observed spectra in the RV analysis. Implementing a series of numerical simulations using theoretical spectra that mimic IRD data, we test the pipeline and show that IRD can achieve <2 m s−1 precision for slowly rotating mid-to-late M dwarfs with a signal-to-noise ratio ≳100 per pixel at 1000 nm. Dependences of RV precision on various stellar parameters (e.g., Teff, vsin i, [Fe/H]) and the impact of telluric-line blendings on the RV accuracy are discussed through the mock spectra analyses. We also apply the RV-analysis pipeline to the observed spectra of GJ 699 and TRAPPIST-1, demonstrating that the spectrograph and the pipeline are capable of an RV accuracy of <3 m s−1 at least on a time-scale of a few months.

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