Star And Planet’s Characterisation Through High Spectral Resolution

2020 ◽  
Author(s):  
Maria Chiara Maimone ◽  
Andrea Chiavassa ◽  
Jeremy Leconte ◽  
Matteo Brogi
Keyword(s):  
High Resolution ◽  
Spectral Resolution ◽  
Molecular Species ◽  
Climate Model ◽  
Global Climate Model ◽  
Spectral Lines ◽  
High Spectral Resolution ◽  
High Resolution Spectroscopy ◽  
Stellar Disk ◽  
Precise Knowledge

<p>The study of exoplanets atmospheres is one of the most intriguing challenges in exoplanet field nowadays and the High Resolution Spectroscopy (HRS) has recently emerged as one of the leading methods for detecting atomic and molecular species in their atmospheres. In terms of numbers, if we define the resolution power R,<span class="Apple-converted-space">  </span>where λ is the wavelength and Δλ is the spectral resolution:</p> <p><span class="Apple-converted-space">     R= λ/Δλ</span></p> <p>then, “High Resolution Spectroscopy” means R > 50 000.</p> <p>Nevertheless extraordinary results have been achieved (Birkby, 2018), High Resolution Spectroscopy alone is not enough. 1D models of the host star have been coupled to HRS observations, but they do not reproduce the complexity of stellar convection mechanism (Chiavassa & Brogi, 2019). On the contrary,<span class="Apple-converted-space">  </span>3D Radiative Hydrodynamical simulations (3D RHS) take it into account intrinsically, allowing us to correctly reproduce asymmetric and blue-shifted spectral lines due to the granulation pattern of the stellar disk, which is a very important source of uncertainties at this resolution level (Chiavassa et al. 2017).</p> <p>However, numerical simulations have been computed independently for star and planet so far, while the acquired spectra are an entanglement of both the signals. In particular, some molecular species (e.g, CO) form in the same region of the spectrum, thus planetary and stellar spectral lines are completely mixed and overlapped.<span class="Apple-converted-space"> </span></p> <p>Therefore, a next step forward is needed: computing stellar and planetary models <em>together.</em></p> <p>With our work, we aim at upgrading the already-in-place 3D radiative transfer code Optim3D (Chiavassa et al. 2009) —largely used for stellar purposes so far — to taking into account also the exoplanetary contribution.<span class="Apple-converted-space"> </span>We propose to use simultaneously 3D RHS, performed for stars, and the innovative Global Climate Model (GCM), drawn up for exoplanets, in order to generate unprecedented precise synthetic spectra. As a springboard to test the code, we are carrying out the analysis of CO and H2O molecules on the well-know benchmark HD189733. Indeed, to disentangle those star’s and its companion’s signals due to the same molecules is one of the most challenging problems. In the end, we will be able to compute a complete dynamic characterisation: on one side, a precise knowledge of the stellar dynamic (i.e. convection-related surface structures) would allow to extract unequivocally the planetary signal; on the other one, a well-modelled dynamic of the planet (i.e. depth, shape, and position of spectral lines) would provide us with considerable information about the planetary atmospheric circulation.</p>

A Full Characterisation of Stars and Planets through High Resolution Spectroscopy and 3D Simulations.

2021 ◽  
Author(s):  
Maria Chiara Maimone ◽  
Andrea Chiavassa ◽  
Jeremy Leconte ◽  
Matteo Brogi
Keyword(s):  
High Resolution ◽  
Molecular Species ◽  
Climate Models ◽  
3D Models ◽  
Global Climate Models ◽  
Spectral Lines ◽  
High Resolution Spectroscopy ◽  
Stellar Disk ◽  
Stellar Spectrum ◽  
The Impact

<p>The study of exoplanets atmospheres is one of the most intriguing challenges in the exoplanet field nowadays and the High Resolution Spectroscopy (HRS) has recently emerged as one of the leading methods for detecting atomic and molecular species in their atmospheres (e.g., Birkby, 2018). While this technique is particularly robust against contaminant absorption in the Earth’s atmosphere, the non-stationary stellar spectrum, in the form of either Doppler shift or distortion of the line profile during planetary transits, creates a non-negligible source of noise that can alter or even prevent detection. In the last years, it has become computationally possible to simulate the stellar surface convection that, in the end, allows to correctly reproduce asymmetric and blue-shifted spectral lines due to the granulation pattern of the stellar disk, which is a very important source of uncertainties (Chiavassa & Brogi, 2019). In the context of HRS and on the planet hand side, only recently multidimensional models have been used to detect the weak planet signal in the spectrum (e.g., Flowers et al. 2019).</p> <p>However, these numerical simulations have been computed independently for star and planet so far, while acquired spectra are the result of the natural coupling at each phase along the planet orbit. A next step forward is needed: coupling stellar and planetary 3D models dynamics during the transit.</p> <p>I will present the unprecedented precise synthetic spectra obtained with the upgraded 3D radiative transfer code Optim3D (Chiavassa et al. 2009). Optim3D takes as inputs the state-of-art 3D RHD stellar simulations (Stagger code, Nordlund et al. 2009, Magic et al. 2013) and the 3D Global Climate Models (SPARC/MITgcms, Showman et al. 2009, Parmentier et al. 2021) for stars and planets respectively, coupling them at any phase along the planet orbit. I will show the impact of this new approach on the detection of molecules by cross-correlating our spectra with HRS observations (e.g., Snellen et al 2010 and Brogi et al. 2016). This approach is particularly advantageous for those molecular species that are present in both the atmospheres and form in the same region of the spectrum, resulting in mixed and overlapped spectral lines (e.g. CO and H2O, crucial to constrain the C/O ratio). Moreover, the use of 3D models provides us with information about the dynamics processes at play, such as stellar convection and planetary winds.</p> <p> </p>

scholarly journals A weak spectral signature of water vapour in the atmosphere of HD 179949 b at high spectral resolution in the L band

2020 ◽  
Vol 494 (1) ◽  
pp. 108-119 ◽  
Author(s):  
Rebecca K Webb ◽  
Matteo Brogi ◽  
Siddharth Gandhi ◽  
Michael R Line ◽  
Jayne L Birkby ◽  
...  
Keyword(s):  
High Resolution ◽  
Radial Velocity ◽  
Semimajor Axis ◽  
Spectral Lines ◽  
Lapse Rate ◽  
High Spectral Resolution ◽  
High Resolution Spectroscopy ◽  
Spectral Signature ◽  
Orbital Inclination ◽  
L Band

ABSTRACT High-resolution spectroscopy ($R\, \geqslant \, 20\, 000$) is currently the only known method to constrain the orbital solution and atmospheric properties of non-transiting hot Jupiters. It does so by resolving the spectral features of the planet into a forest of spectral lines and directly observing its Doppler shift while orbiting the host star. In this study, we analyse VLT/CRIRES ($R=100\, 000$) L-band observations of the non-transiting giant planet HD 179949 b centred around 3.5 ${\mu {m}}$. We observe a weak (3.0σ, or S/N = 4.8) spectral signature of H2O in absorption contained within the radial velocity of the planet at superior-conjunction, with a mild dependence on the choice of line list used for the modelling. Combining this data with previous observations in the K band, we measure a detection significance of 8.4 σ for an atmosphere that is most consistent with a shallow lapse-rate, solar C/O ratio, and with CO and H2O being the only major sources of opacity in this wavelength range. As the two sets of data were taken 3 yr apart, this points to the absence of strong radial-velocity anomalies due, e.g. to variability in atmospheric circulation. We measure a projected orbital velocity for the planet of KP = (145.2 ± 2.0) km s−1 (1σ) and improve the error bars on this parameter by ∼70 per cent. However, we only marginally tighten constraints on orbital inclination ($66.2^{+3.7}_{-3.1}$ deg) and planet mass ($0.963^{+0.036}_{-0.031}$ Jupiter masses), due to the dominant uncertainties of stellar mass and semimajor axis. Follow ups of radial-velocity planets are thus crucial to fully enable their accurate characterization via high-resolution spectroscopy.

scholarly journals High-resolution X-ray spectroscopy of astrophysical plasmas with X-ray microcalorimeters

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Yuichiro Ezoe ◽  
Takaya Ohashi ◽  
Kazuhisa Mitsuda
Keyword(s):  
High Resolution ◽  
Spectral Resolution ◽  
High Sensitivity ◽  
Resolving Power ◽  
High Spectral Resolution ◽  
High Resolution Spectroscopy ◽  
Astrophysical Plasmas ◽  
X Ray ◽  
New Findings ◽  
Perseus Cluster

AbstractHigh spectral resolution with a resolving power, $$E/\Delta E \gtrsim 1000$$ E / Δ E ≳ 1000 at 6 keV, is now available in X-ray astronomy. X-ray observations are particularly effective for plasma studies since major atomic transitions appear as spectral features in the X-ray band. High-resolution spectroscopy enables us to probe a wide variety of astrophysical plasmas, which are not obtainable from ground experiments, regarding their temperature, density, magnetic field, gravity, and velocity. In this review, we describe what are the X-ray emitting plasmas in the Universe, along with basic plasma diagnostics, and depict historical development of the techniques used for the X-ray spectroscopy. We outline the X-ray microcalorimeter instrument, soft X-ray spectrometer (SXS), onboard the ASTRO-H satellite. Despite the short lifetime of the satellite in orbit for about a month, observations with the SXS have shown the remarkable power of high-resolution spectroscopy in X-ray astronomy. Observed spectrum of the hot plasma in the core region of the Perseus cluster showed He-like Fe K-line to be clearly resolved into resonance, forbidden and intercombination lines for the first time. The line width indicates that the turbulent pressure amounts to only 4% of the thermal pressure of the plasma. We also describe new findings and constraints obtained from the superb spectrum of the Perseus cluster, which all indicate a great potential of X-ray spectroscopy. The recovery of the spectroscopy science of ASTRO-H is aimed at with XRISM, a Japanese mission planned for launch in early 2020s. In further future, Athena will expand the rich science with its high sensitivity and spectral resolution in early 2030s.

scholarly journals Multilayer Mirror Based High-Resolution Solar Soft X-Ray Spectrometer

2021 ◽  
Vol 8 ◽  
Author(s):  
S. S. Panini ◽  
S. Narendranath ◽  
P. Sreekumar ◽  
K. Sankarasubramanian
Keyword(s):  
High Resolution ◽  
Spectral Range ◽  
Spectral Resolution ◽  
High Spectral Resolution ◽  
High Resolution Spectroscopy ◽  
Time Variability ◽  
Type I ◽  
The Sun ◽  
X Rays ◽  
X Ray

Soft X-ray spectroscopy of the Sun is an important tool to understand the coronal dynamics and composition. The solar coronal X-ray spectrum below 1 keV is the least explored with high-resolution spectroscopy. Recent observations with Hinode XRT using coarse spectroscopy along with high-resolution imaging have shown that abundances in the coronae have variability associated with structures on the Sun. Disk averaged abundances with better spectral resolution spectrometers show time variability associated with flares. Both spatial and temporal variabilities seem to be related to changes in the magnetic field topology. Understanding such short term variabilities is necessary to model the underlying dynamics and mixing of material between different layers of the Sun. A Sensitive high-resolution spectrometer that covers the range in plasma temperatures and emission line complexes would uniquely reveal the entire evolution of flares. We are investigating a design of a multi-layer mirror-based X-ray spectrograph in the spectral range from 0.5 to 7 keV. The instrument operates in four asynchronous spectral channels operating one at a time. The multi-layer mirror placed at the focus of a Wolter type I telescope reflects a narrow band X-rays to the CCD which is placed at Nasmyth defocus. Converging X-rays from the front end optics helps to increase the spectral range of each channel while preserving the spectral resolution. This design is estimated to achieve a spectral resolution of 20 eV in the spectral range of 0.5–7 keV. With such high spectral resolution, we can resolve individual spectral features e.g., 6.7 keV Fe complex which can be used to diagnose high-temperature transient plasma during flares. The instrument design estimated performance and the science capabilities of this instrument will be discussed in detail in the paper.

scholarly journals A coma-free super-high resolution optical spectrometer using 44 high dispersion sub-gratings

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Hua-Tian Tu ◽  
An-Qing Jiang ◽  
Jian-Ke Chen ◽  
Wei-Jie Lu ◽  
Kai-Yan Zang ◽  
...  
Keyword(s):  
High Resolution ◽  
Spectral Resolution ◽  
Wavelength Region ◽  
Ultra Violet ◽  
High Spectral Resolution ◽  
Visible Range ◽  
High Dispersion ◽  
Charge Coupled Device ◽  
Wide Range ◽  
High Resolution Spectrometer

AbstractUnlike the single grating Czerny–Turner configuration spectrometers, a super-high spectral resolution optical spectrometer with zero coma aberration is first experimentally demonstrated by using a compound integrated diffraction grating module consisting of 44 high dispersion sub-gratings and a two-dimensional backside-illuminated charge-coupled device array photodetector. The demonstrated super-high resolution spectrometer gives 0.005 nm (5 pm) spectral resolution in ultra-violet range and 0.01 nm spectral resolution in the visible range, as well as a uniform efficiency of diffraction in a broad 200 nm to 1000 nm wavelength region. Our new zero-off-axis spectrometer configuration has the unique merit that enables it to be used for a wide range of spectral sensing and measurement applications.

High-Resolution Climate Change Impact Analysis on Expected Future Water Availability in the Upper Jordan Catchment and the Middle East

2014 ◽  
Vol 15 (4) ◽  
pp. 1517-1531 ◽  
Author(s):  
Gerhard Smiatek ◽  
Harald Kunstmann ◽  
Andreas Heckl
Keyword(s):  
Climate Change ◽  
High Resolution ◽  
Water Availability ◽  
Impact Analysis ◽  
River Flow ◽  
Climate Model ◽  
Mesoscale Model ◽  
Global Climate Model ◽  
Full Range ◽  
The Impact

Abstract The impact of climate change on the future water availability of the upper Jordan River (UJR) and its tributaries Dan, Snir, and Hermon located in the eastern Mediterranean is evaluated by a highly resolved distributed approach with the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5) run at 18.6- and 6.2-km resolution offline coupled with the Water Flow and Balance Simulation Model (WaSiM). The MM5 was driven with NCEP reanalysis for 1971–2000 and with Hadley Centre Coupled Model, version 3 (HadCM3), GCM forcings for 1971–2099. Because only one regional–global climate model combination was applied, the results may not give the full range of possible future projections. To describe the Dan spring behavior, the hydrological model was extended by a bypass approach to allow the fast discharge components of the Snir to enter the Dan catchment. Simulation results for the period 1976–2000 reveal that the coupled system was able to reproduce the observed discharge rates in the partially karstic complex terrain to a reasonable extent with the high-resolution 6.2-km meteorological input only. The performed future climate simulations show steadily rising temperatures with 2.2 K above the 1976–2000 mean for the period 2031–60 and 3.5 K for the period 2070–99. Precipitation trends are insignificant until the middle of the century, although a decrease of approximately 12% is simulated. For the end of the century, a reduction in rainfall ranging between 10% and 35% can be expected. Discharge in the UJR is simulated to decrease by 12% until 2060 and by 26% until 2099, both related to the 1976–2000 mean. The discharge decrease is associated with a lower number of high river flow years.

scholarly journals Climate SPHINX: evaluating the impact of resolution and stochastic physics parameterisations in the EC-Earth global climate model

2017 ◽  
Vol 10 (3) ◽  
pp. 1383-1402 ◽  
Author(s):  
Paolo Davini ◽  
Jost von Hardenberg ◽  
Susanna Corti ◽  
Hannah M. Christensen ◽  
Stephan Juricke ◽  
...  
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Climate Model ◽  
Global Climate ◽  
Rainfall Variability ◽  
Global Climate Model ◽  
Small Scale ◽  
Low Resolution ◽  
The Impact ◽  
Stochastic Physics

Abstract. The Climate SPHINX (Stochastic Physics HIgh resolutioN eXperiments) project is a comprehensive set of ensemble simulations aimed at evaluating the sensitivity of present and future climate to model resolution and stochastic parameterisation. The EC-Earth Earth system model is used to explore the impact of stochastic physics in a large ensemble of 30-year climate integrations at five different atmospheric horizontal resolutions (from 125 up to 16 km). The project includes more than 120 simulations in both a historical scenario (1979–2008) and a climate change projection (2039–2068), together with coupled transient runs (1850–2100). A total of 20.4 million core hours have been used, made available from a single year grant from PRACE (the Partnership for Advanced Computing in Europe), and close to 1.5 PB of output data have been produced on SuperMUC IBM Petascale System at the Leibniz Supercomputing Centre (LRZ) in Garching, Germany. About 140 TB of post-processed data are stored on the CINECA supercomputing centre archives and are freely accessible to the community thanks to an EUDAT data pilot project. This paper presents the technical and scientific set-up of the experiments, including the details on the forcing used for the simulations performed, defining the SPHINX v1.0 protocol. In addition, an overview of preliminary results is given. An improvement in the simulation of Euro-Atlantic atmospheric blocking following resolution increase is observed. It is also shown that including stochastic parameterisation in the low-resolution runs helps to improve some aspects of the tropical climate – specifically the Madden–Julian Oscillation and the tropical rainfall variability. These findings show the importance of representing the impact of small-scale processes on the large-scale climate variability either explicitly (with high-resolution simulations) or stochastically (in low-resolution simulations).

scholarly journals The role of serial European windstorm clustering for extreme seasonal losses as determined from multi-centennial simulations of high-resolution global climate model data

2018 ◽  
Vol 18 (11) ◽  
pp. 2991-3006 ◽  
Author(s):  
Matthew D. K. Priestley ◽  
Helen F. Dacre ◽  
Len C. Shaffrey ◽  
Kevin I. Hodges ◽  
Joaquim G. Pinto
Keyword(s):  
High Resolution ◽  
Return Period ◽  
Large Scale ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Geographic Region ◽  
Near Surface ◽  
Short Period

Abstract. Extratropical cyclones are the most damaging natural hazard to affect western Europe. Serial clustering occurs when many intense cyclones affect one specific geographic region in a short period of time which can potentially lead to very large seasonal losses. Previous studies have shown that intense cyclones may be more likely to cluster than less intense cyclones. We revisit this topic using a high-resolution climate model with the aim to determine how important clustering is for windstorm-related losses. The role of windstorm clustering is investigated using a quantifiable metric (storm severity index, SSI) that is based on near-surface meteorological variables (10 m wind speed) and is a good proxy for losses. The SSI is used to convert a wind footprint into losses for individual windstorms or seasons. 918 years of a present-day ensemble of coupled climate model simulations from the High-Resolution Global Environment Model (HiGEM) are compared to ERA-Interim reanalysis. HiGEM is able to successfully reproduce the wintertime North Atlantic/European circulation, and represent the large-scale circulation associated with the serial clustering of European windstorms. We use two measures to identify any changes in the contribution of clustering to the seasonal windstorm loss as a function of return period. Above a return period of 3 years, the accumulated seasonal loss from HiGEM is up to 20 % larger than the accumulated seasonal loss from a set of random resamples of the HiGEM data. Seasonal losses are increased by 10 %–20 % relative to randomized seasonal losses at a return period of 200 years. The contribution of the single largest event in a season to the accumulated seasonal loss does not change with return period, generally ranging between 25 % and 50 %. Given the realistic dynamical representation of cyclone clustering in HiGEM, and comparable statistics to ERA-Interim, we conclude that our estimation of clustering and its dependence on the return period will be useful for informing the development of risk models for European windstorms, particularly for longer return periods.

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