scholarly journals The CARMENES search for exoplanets around M dwarfs

2019 ◽  
Vol 623 ◽  
pp. A136 ◽  
Author(s):  
D. Hintz ◽  
B. Fuhrmeister ◽  
S. Czesla ◽  
J. H. M. M. Schmitt ◽  
E. N. Johnson ◽  
...  
Keyword(s):  
Near Infrared ◽  
Active Regions ◽  
Variable Stars ◽  
Temperature Structure ◽  
M Dwarfs ◽  
Linear Combinations ◽  
One Dimensional ◽  
Best Fit ◽  
Calar Alto ◽  
Infrared Triplet

Chromospheric modeling of observed differences in stellar activity lines is imperative to fully understand the upper atmospheres of late-type stars. We present one-dimensional parametrized chromosphere models computed with the atmosphere code PHOENIX using an underlying photosphere of 3500 K. The aim of this work is to model chromospheric lines of a sample of 50 M2–3 dwarfs observed in the framework of the CARMENES, the Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs, exoplanet survey. The spectral comparison between observed data and models is performed in the chromospheric lines of Na I D2, Hα, and the bluest Ca II infrared triplet line to obtain best-fit models for each star in the sample. We find that for inactive stars a single model with a VAL C-like temperature structure is sufficient to describe simultaneously all three lines adequately. Active stars are rather modeled by a combination of an inactive and an active model, also giving the filling factors of inactive and active regions. Moreover, the fitting of linear combinations on variable stars yields relationships between filling factors and activity states, indicating that more active phases are coupled to a larger portion of active regions on the surface of the star.

scholarly journals Kinematics of M dwarfs in the CARMENES Input Catalogue: Membership in Young Moving Groups

2015 ◽  
Vol 10 (S314) ◽  
pp. 71-72
Author(s):  
D. Montes ◽  
J. A. Caballero ◽  
I. Gallardo ◽  
M. Cortés-Contreras ◽  
F. J. Alonso-Floriano
Keyword(s):  
Near Infrared ◽  
Distance Estimation ◽  
Age Dating ◽  
Velocity Measurements ◽  
M Dwarfs ◽  
Dating Methods ◽  
Moving Groups ◽  
Input Catalogue ◽  
Photometric Distance ◽  
Calar Alto

AbstractWe present a detailed study of the kinematics of M dwarfs in the CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs) input catalog. We have selected all M dwarfs with known parallactic distance or a good photometric distance estimation, precise proper motion in the literature or as determined by us, and radial velocity measurements. Using these parameters, we computed the M dwarfs galactic space motions (U, V, W). For the stars with U and V velocity components inside or near the boundaries that determine the young disk population, we have analyzed the possible membership in the classical moving groups and nearby loose associations with ages between 10 and 600 Myr. For the candidate members, we have compiled information available in the literature in order to constrain their membership by applying other age-dating methods.

scholarly journals The CARMENES search for exoplanets around M dwarfs

2019 ◽  
Vol 632 ◽  
pp. A24
Author(s):  
B. Fuhrmeister ◽  
S. Czesla ◽  
L. Hildebrandt ◽  
E. Nagel ◽  
J. H. M. M. Schmitt ◽  
...  
Keyword(s):  
Near Infrared ◽  
Activity Levels ◽  
Line Formation ◽  
M Dwarfs ◽  
Complex Behaviour ◽  
X Ray ◽  
Solar Type ◽  
M Dwarf ◽  
Calar Alto ◽  
Important Activity

The He I infrared (IR) triplet at 10 830 Å is an important activity indicator for the Sun and in solar-type stars, however, it has rarely been studied in relation to M dwarfs to date. In this study, we use the time-averaged spectra of 319 single stars with spectral types ranging from M0.0 V to M9.0 V obtained with the CARMENES high resolution optical and near-infrared spectrograph at Calar Alto to study the properties of the He I IR triplet lines. In quiescence, we find the triplet in absorption with a decrease of the measured pseudo equivalent width (pEW) towards later sub-types. For stars later than M5.0 V, the He I triplet becomes undetectable in our study. This dependence on effective temperature may be related to a change in chromospheric conditions along the M dwarf sequence. When an emission in the triplet is observed, we attribute it to flaring. The absence of emission during quiescence is consistent with line formation by photo-ionisation and recombination, while flare emission may be caused by collisions within dense material. The He I triplet tends to increase in depth according to increasing activity levels, ultimately becoming filled in; however, we do not find a correlation between the pEW(He IR) and X-ray properties. This behaviour may be attributed to the absence of very inactive stars (LX∕Lbol < −5.5) in our sample or to the complex behaviour with regard to increasing depth and filling in.

scholarly journals CARMENES: Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs

2010 ◽  
Vol 6 (S276) ◽  
pp. 545-546 ◽  
Author(s):  
Andreas Quirrenbach ◽  
Pedro J. Amado ◽  
José A. Caballero ◽  
Holger Mandel ◽  
Reinhard Mundt ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Emission Line ◽  
Wavelength Range ◽  
Spectral Resolution ◽  
Near Infrared ◽  
M Dwarfs ◽  
Simultaneous Emission ◽  
M Stars ◽  
Calar Alto

AbstractCARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs) is a next-generation instrument for the 3.5 m telescope at the Calar Alto Observatory. CARMENES will conduct a five-year exoplanet survey targeting ~300 M stars. The CARMENES instrument consists of two separate fiber-fed spectrographs covering the wavelength range from 0.52 to 1.7 μm at a spectral resolution of R = 85,000. The spectrographs are housed in a temperature-stabilized environment in vacuum tanks, to enable a 1 m/s radial velocity precision employing a simultaneous emission-line calibration.

scholarly journals The CARMENES search for exoplanets around M dwarfs

2018 ◽  
Vol 615 ◽  
pp. A14 ◽  
Author(s):  
B. Fuhrmeister ◽  
S. Czesla ◽  
J. H. M. M. Schmitt ◽  
S. V. Jeffers ◽  
J. A. Caballero ◽  
...  
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Common Phenomenon ◽  
Complex Line ◽  
Line Profiles ◽  
Stark Broadening ◽  
M Dwarfs ◽  
Additional Line ◽  
Coronal Rain ◽  
Calar Alto

Stellar activity is ubiquitously encountered in M dwarfs and often characterised by the Hα line. In the most active M dwarfs, Hα is found in emission, sometimes with a complex line profile. Previous studies have reported extended wings and asymmetries in the Hα line during flares. We used a total of 473 high-resolution spectra of 28 active M dwarfs obtained by the CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-Earths with Near-infrared and optical Echelle Spectrographs) spectrograph to study the occurrence of broadened and asymmetric Hα line profiles and their association with flares, and examine possible physical explanations. We detected a total of 41 flares and 67 broad, potentially asymmetric, wings in Hα. The broadened Hα lines display a variety of profiles with symmetric cases and both red and blue asymmetries. Although some of these line profiles are found during flares, the majority are at least not obviously associated with flaring. We propose a mechanism similar to coronal rain or chromospheric downward condensations as a cause for the observed red asymmetries; the symmetric cases may also be caused by Stark broadening. We suggest that blue asymmetries are associated with rising material, and our results are consistent with a prevalence of blue asymmetries during the flare onset. Besides the Hα asymmetries, we find some cases of additional line asymmetries in He I D3, Na I D lines, and the He I line at 10 830 Å taken all simultaneously thanks to the large wavelength coverage of CARMENES. Our study shows that asymmetric Hα lines are a rather common phenomenon in M dwarfs and need to be studied in more detail to obtain a better understanding of the atmospheric dynamics in these objects.

scholarly journals CARMENES: Calar Alto high-resolution search for M dwarfs with exo-earths with a near-infrared Echelle spectrograph

2010 ◽  
Author(s):  
A. Quirrenbach ◽  
P. J. Amado ◽  
H. Mandel ◽  
J. A. Caballero ◽  
R. Mundt ◽  
...  
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
M Dwarfs ◽  
Echelle Spectrograph ◽  
Calar Alto

scholarly journals The CARMENES search for exoplanets around M dwarfs

2019 ◽  
Vol 623 ◽  
pp. A44 ◽  
Author(s):  
P. Schöfer ◽  
S. V. Jeffers ◽  
A. Reiners ◽  
D. Shulyak ◽  
B. Fuhrmeister ◽  
...  
Keyword(s):  
Near Infrared ◽  
Rotation Period ◽  
Periodic Variation ◽  
Activity Levels ◽  
Rotating Stars ◽  
M Dwarfs ◽  
Activity Effect ◽  
Earth Like Planets ◽  
Infrared Wavelengths ◽  
Infrared Triplet

Context. The Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs (CARMENES) survey is searching for Earth-like planets orbiting M dwarfs using the radial velocity method. Studying the stellar activity of the target stars is important to avoid false planet detections and to improve our understanding of the atmospheres of late-type stars. Aims. In this work we present measurements of activity indicators at visible and near-infrared wavelengths for 331 M dwarfs observed with CARMENES. Our aim is to identify the activity indicators that are most sensitive and easiest to measure, and the correlations among these indicators. We also wish to characterise their variability. Methods. Using a spectral subtraction technique, we measured pseudo-equivalent widths of the He I D3, Hα, He I λ10833 Å, and Pa β lines, the Na I D doublet, and the Ca II infrared triplet, which have a chromospheric component in active M dwarfs. In addition, we measured an index of the strength of two TiO and two VO bands, which are formed in the photosphere. We also searched for periodicities in these activity indicators for all sample stars using generalised Lomb-Scargle periodograms. Results. We find that the most slowly rotating stars of each spectral subtype have the strongest Hα absorption. Hα is correlated most strongly with He I D3, whereas Na I D and the Ca II infrared triplet are also correlated with Hα. He I λ10833 Å and Paβ show no clear correlations with the other indicators. The TiO bands show an activity effect that does not appear in the VO bands. We find that the relative variations of Hα and He I D3 are smaller for stars with higher activity levels, while this anti-correlation is weaker for Na I D and the Ca II infrared triplet, and is absent for He I λ10833 Å and Paβ. Periodic variation with the rotation period most commonly appears in the TiO bands, Hα, and in the Ca II infrared triplet.

The length controllable synthesis and near-infrared photoluminescence of one-dimensional ternary Cu4Bi4S9 semiconductor nanobelts

2014 ◽  
Vol 49 ◽  
pp. 180-186 ◽  
Author(s):  
Jing Li ◽  
Xiaoxu wang ◽  
Ruibin Liu ◽  
Lijie shi ◽  
Muhammad Arshad Kamran ◽  
...  
Keyword(s):  
Near Infrared ◽  
Controllable Synthesis ◽  
One Dimensional

scholarly journals Using a One-Dimensional Convolutional Neural Network on Visible and Near-Infrared Spectroscopy to Improve Soil Phosphorus Prediction in Madagascar

2021 ◽  
Vol 13 (8) ◽  
pp. 1519
Author(s):  
Kensuke Kawamura ◽  
Tomohiro Nishigaki ◽  
Andry Andriamananjara ◽  
Hobimiarantsoa Rakotonindrina ◽  
Yasuhiro Tsujimoto ◽  
...  
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
Near Infrared ◽  
Soil Phosphorus ◽  
Predictive Ability ◽  
Available P ◽  
Accurate Estimation ◽  
One Dimensional ◽  
P Content ◽  
Soil Available P

As a proximal soil sensing technique, laboratory visible and near-infrared (Vis-NIR) spectroscopy is a promising tool for the quantitative estimation of soil properties. However, there remain challenges for predicting soil phosphorus (P) content and availability, which requires a reliable model applicable for different land-use systems to upscale. Recently, a one-dimensional convolutional neural network (1D-CNN) corresponding to the spectral information of soil was developed to considerably improve the accuracy of soil property predictions. The present study investigated the predictive ability of a 1D-CNN model to estimate soil available P (oxalate-extractable P; Pox) content in soils by comparing it with partial least squares (PLS) and random forest (RF) regressions using soil samples (n = 318) collected from natural (forest and non-forest) and cultivated (upland and flooded rice fields) systems in Madagascar. Overall, the 1D-CNN model showed the best predictive accuracy (R2 = 0.878) with a highly accurate prediction ability (ratio of performance to the interquartile range = 2.492). Compared to the PLS model, the RF and 1D-CNN models indicated 4.37% and 23.77% relative improvement in root mean squared error values, respectively. Based on a sensitivity analysis, the important wavebands for predicting soil Pox were associated with iron (Fe) oxide, organic matter (OM), and water absorption, which were previously known wavelength regions for estimating P in soil. These results suggest that 1D-CNN corresponding spectral signatures can be expected to significantly improve the predictive ability for estimating soil available P (Pox) from Vis-NIR spectral data. Rapid and accurate estimation of available P content in soils using our results can be expected to contribute to effective fertilizer management in agriculture and the sustainable management of ecosystems. However, the 1D-CNN model will require a large dataset to extend its applicability to other regions of Madagascar. Thus, further updates should be tested in future studies using larger datasets from a wide range of ecosystems in the tropics.

Examining the emission and transmission spectra of WASP-79b with retrieval 

2021 ◽  
Author(s):  
Michelle Bieger ◽  
Quentin Changeat
Keyword(s):  
Hubble Space Telescope ◽  
Emission Spectra ◽  
Temperature Structure ◽  
Wide Field ◽  
Transmission Spectra ◽  
Analysis Pipeline ◽  
Confidence Levels ◽  
Iron Hydride ◽  
Best Fit ◽  
Data Analysis Pipeline

&lt;p&gt;Retrieval tools provide a way of determining an exoplanet atmosphere's temperature structure and composition with an observed planetary spectrum, working backwards to determine the chemistry and temperature by iteratively comparing synthetic spectra that have been constructed via a forward model to the observed spectra and determining a best-fit result (Barstow and Heng, 2020). This talk will be presenting the emission and reanalysed transmission spectrum and retrieval analysis of WASP-79b, an inflated hot Jupiter first detected by Smalley et al. (2012). Previous transmission spectra of WASP-79b has been analysed in Sozten et al. (2020), Skaf et al. (2020), and Rathcke et al. (2021); all studies agreeing on detections of H2O with various confidence levels, with the latter finding moderate evidence of an H- bound-free opacity compared to iron hydride abundance found by the other studies. Using the publicly available \verb+Iraclis+ data analysis pipeline and the Bayesian atmospheric retrieval framework TauREx 3, we will be adding to the global picture of this planet by examining the Hubble Space Telescope emission spectra as captured by the Wide Field Camera 3 G141 grism (PI: David Sing, proposal ID: 14767).&amp;#160;&lt;/p&gt;

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