scholarly journals Stellar population astrophysics (SPA) with the TNG

2020 ◽  
Vol 645 ◽  
pp. A19
Author(s):  
C. Fanelli ◽  
L. Origlia ◽  
E. Oliva ◽  
A. Mucciarelli ◽  
N. Sanna ◽  
...  
Keyword(s):  
High Resolution ◽  
Stellar Population ◽  
Near Infrared ◽  
Chemical Species ◽  
Chemical Properties ◽  
High Resolution Spectroscopy ◽  
Diagnostic Tools ◽  
Echelle Spectrograph ◽  
Chemical Abundances ◽  
Molecular Lines

Context. High-resolution spectroscopy in the near-infrared (NIR) is a powerful tool for characterising the physical and chemical properties of cool-star atmospheres. The current generation of NIR echelle spectrographs enables the sampling of many spectral features over the full 0.9–2.4 μm range for a detailed chemical tagging. Aims. Within the Stellar Population Astrophysics Large Program at the TNG, we used a high-resolution (R = 50 000) NIR spectrum of Arcturus acquired with the GIANO-B echelle spectrograph as a laboratory to define and calibrate an optimal line list and new diagnostic tools to derive accurate stellar parameters and chemical abundances. Methods. We inspected several hundred NIR atomic and molecular lines to derive abundances of 26 different chemical species, including CNO, iron-group, alpha, Z-odd, and neutron-capture elements. We then performed a similar analysis in the optical using Arcturus VLT-UVES spectra. Results. Through the combined NIR and optical analysis we defined a new thermometer and a new gravitometer for giant stars, based on the comparison of carbon (for the thermometer) and oxygen (for the gravitometer) abundances, as derived from atomic and molecular lines. We then derived self-consistent stellar parameters and chemical abundances of Arcturus over the full 4800–24 500 Å spectral range and compared them with previous studies in the literature. We finally discuss a number of problematic lines that may be affected by deviations from thermal equilibrium and/or chromospheric activity, as traced by the observed variability of He I at 10 830 Å.

scholarly journals Seeing above the clouds with high-resolution spectroscopy

2020 ◽  
Vol 498 (1) ◽  
pp. 194-204
Author(s):  
Siddharth Gandhi ◽  
Matteo Brogi ◽  
Rebecca K Webb
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Chemical Species ◽  
Compositional Analysis ◽  
Chemical Diversity ◽  
High Resolution Spectroscopy ◽  
Infrared Observations ◽  
Hot Jupiters ◽  
Doppler Spectroscopy ◽  
Cloud Top Pressure

ABSTRACT In the last decade, ground-based high-resolution Doppler spectroscopy (HRS) has detected numerous species in transiting and non-transiting hot Jupiters, and is ideally placed for atmospheric characterization of warm Neptunes and super Earths. Many of these cooler and smaller exoplanets have shown cloudy atmospheres from low-resolution near-infrared observations, making constraints on chemical species difficult. We investigate how HRS can improve on these given its sensitivity to spectral line cores which probe higher altitudes above the clouds. We model transmission spectra for the warm Neptune GJ 3470b and determine the detectability of H2O with the CARMENES, GIANO, and SPIRou spectrographs. We also model a grid of spectra for another warm Neptune, GJ 436b, over a range of cloud-top pressure and H2O abundance. We show H2O is detectable for both planets with modest observational time and that the high H2O abundance-high cloud deck degeneracy is broken with HRS. However, meaningful constraints on abundance and cloud-top pressure are only possible in the high-metallicity scenario. We also show that detections of CH4 and NH3 are possible from cloudy models of GJ 436b. Lastly, we show how the presence of the Earth’s transmission spectrum hinders the detection of H2O for the most cloudy scenarios given that telluric absorption overlaps with the strongest H2O features. The constraints possible with HRS on the molecular species can be used for compositional analysis and to study the chemical diversity of such planets in the future.

scholarly journals How well can we determine ages and chemical abundances from spectral fitting of integrated light spectra?

2020 ◽  
Vol 499 (2) ◽  
pp. 2327-2339
Author(s):  
Geraldo Gonçalves ◽  
Paula Coelho ◽  
Ricardo Schiavon ◽  
Christopher Usher
Keyword(s):  
High Resolution ◽  
Wavelength Range ◽  
Globular Clusters ◽  
Stellar Population ◽  
High Resolution Spectroscopy ◽  
Chemical Abundances ◽  
Spectral Fitting ◽  
Light Spectra ◽  
The Ideal

ABSTRACT The pixel-to-pixel spectral fitting technique is often used in studies of stellar populations. It enables the user to infer several parameters from integrated light spectra such as ages and chemical abundances. In this paper, we examine the question of how the inferred parameters change with the choice of wavelength range used. We have employed two different libraries of integrated light spectra of globular clusters (GCs) from the literature and fitted them to stellar population models using the code Starlight. We performed tests using different regions of the spectra to infer reddening, ages, [Fe/H], and [α/Fe]. Comparing our results to age values obtained from isochrone fitting and chemical abundances from high-resolution spectroscopy, we find that: (1) the inferred parameters change with the wavelength range used; (2) the method in general retrieves good reddening estimates, specially when a wider wavelength range is fitted; (3) the ideal spectral regions for determination of age, [Fe/H], and [α/Fe] are 4170–5540, 5280–7020, and 4828–5364 Å, respectively; (4) the retrieved age values for old metal-poor objects can be several Gyr younger than those resulting from isochrone fitting. We conclude that, depending on the parameter of interest and the accuracy requirements, fitting the largest possible wavelength range may not necessarily be the best strategy.

scholarly journals The Massive M31 Cluster G1: Detailed Chemical Abundances from Integrated Light Spectroscopy*

2021 ◽  
Author(s):  
Charli M Sakari ◽  
Matthew D Shetrone ◽  
Andrew McWilliam ◽  
George Wallerstein
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Chemical Properties ◽  
Star Clusters ◽  
High Resolution Spectrum ◽  
Subsequent Paper ◽  
Chemical Abundances ◽  
Moderate Resolution ◽  
Astrophysical Research ◽  
Detailed Chemical

Abstract G1, also known as Mayall II, is one of the most massive star clusters in M31. Its mass, ellipticity, and location in the outer halo make it a compelling candidate for a former nuclear star cluster. This paper presents an integrated light abundance analysis of G1, based on a moderately high-resolution (R = 15, 000) spectrum obtained with the High Resolution Spectrograph on the Hobby-Eberly Telescope in 2007 and 2008. To independently determine the metallicity, a moderate resolution (R ∼ 4, 000) spectrum of the calcium-II triplet lines in the near-infrared was also obtained with the Astrophysical Research Consortium’s 3.5-m telescope at Apache Point Observatory. From the high-resolution spectrum, G1 is found to be a moderately metal-poor cluster, with $[\rm {Fe/H}]~=~-0.98\pm 0.05$. G1 also shows signs of α-enhancement (based on Mg, Ca, and Ti) and lacks the s-process enhancements seen in dwarf galaxies (based on comparisons of Y, Ba, and Eu), indicating that it originated in a fairly massive galaxy. Intriguingly, G1 also exhibits signs of Na and Al enhancement, a unique signature of GCs—this suggests that G1’s formation is intimately connected with GC formation. G1’s high [Na/Fe] also extends previous trends with cluster velocity dispersion to an even higher mass regime, implying that higher mass clusters are more able to retain Na-enhanced ejecta. The effects of intracluster abundance spreads are discussed in a subsequent paper. Ultimately, G1’s chemical properties are found to resemble other M31 GCs, though it also shares some similarities with extragalactic nuclear star clusters.

scholarly journals Masses and ages for metal-poor stars

2019 ◽  
Vol 627 ◽  
pp. A173 ◽  
Author(s):  
M. Valentini ◽  
C. Chiappini ◽  
D. Bossini ◽  
A. Miglio ◽  
G. R. Davies ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Age Determination ◽  
High Resolution Spectroscopy ◽  
Chemical Abundances ◽  
Abundance Pattern ◽  
Halo Stars ◽  
Stellar Ages ◽  
First Results ◽  
Detailed Chemical

Context. Very metal-poor halo stars are the best candidates for being among the oldest objects in our Galaxy. Samples of halo stars with age determination and detailed chemical composition measurements provide key information for constraining the nature of the first stellar generations and the nucleosynthesis in the metal-poor regime. Aims. Age estimates are very uncertain and are available for only a small number of metal-poor stars. We present the first results of a pilot programme aimed at deriving precise masses, ages, and chemical abundances for metal-poor halo giants using asteroseismology and high-resolution spectroscopy. Methods. We obtained high-resolution UVES spectra for four metal-poor RAVE stars observed by the K2 satellite. Seismic data obtained from K2 light curves helped improve spectroscopic temperatures, metallicities, and individual chemical abundances. Mass and ages were derived using the code PARAM, investigating the effects of different assumptions (e.g. mass loss and [α/Fe]-enhancement). Orbits were computed using Gaia DR2 data. Results. The stars are found to be normal metal-poor halo stars (i.e. non C-enhanced), and an abundance pattern typical of old stars (i.e. α and Eu-enhanced), and have masses in the 0.80−1.0 M⊙ range. The inferred model-dependent stellar ages are found to range from 7.4 Gyr to 13.0 Gyr with uncertainties of ∼30%−35%. We also provide revised masses and ages for metal-poor stars with Kepler seismic data from the APOGEE survey and a set of M4 stars. Conclusions. The present work shows that the combination of asteroseismology and high-resolution spectroscopy provides precise ages in the metal-poor regime. Most of the stars analysed in the present work (covering the metallicity range of [Fe/H] ∼ −0.8 to −2 dex) are very old >9 Gyr (14 out of 19 stars), and all of the stars are older than >5 Gyr (within the 68 percentile confidence level).

scholarly journals Multi-Wavelength High-Resolution Spectroscopy for Exoplanet Detection: Motivation, Instrumentation and First Results

Geosciences ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 289 ◽  
Author(s):  
Serena Benatti
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Giant Planet ◽  
High Resolution Spectroscopy ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
First Results ◽  
Multi Wavelength ◽  
Low Mass ◽  
Rocky Planets

Exoplanet research has shown an incessant growth since the first claim of a hot giant planet around a solar-like star in the mid-1990s. Today, the new facilities are working to spot the first habitable rocky planets around low-mass stars as a forerunner for the detection of the long-awaited Sun-Earth analog system. All the achievements in this field would not have been possible without the constant development of the technology and of new methods to detect more and more challenging planets. After the consolidation of a top-level instrumentation for high-resolution spectroscopy in the visible wavelength range, a huge effort is now dedicated to reaching the same precision and accuracy in the near-infrared. Actually, observations in this range present several advantages in the search for exoplanets around M dwarfs, known to be the most favorable targets to detect possible habitable planets. They are also characterized by intense stellar activity, which hampers planet detection, but its impact on the radial velocity modulation is mitigated in the infrared. Simultaneous observations in the visible and near-infrared ranges appear to be an even more powerful technique since they provide combined and complementary information, also useful for many other exoplanetary science cases.

scholarly journals On the synergy between Ariel and ground-based high-resolution spectroscopy

2022 ◽  
Author(s):  
Gloria Guilluy ◽  
Alessandro Sozzetti ◽  
Paolo Giacobbe ◽  
Aldo S. Bonomo ◽  
Giuseppina Micela
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Major Axis ◽  
High Resolution Spectroscopy ◽  
Correlation Technique ◽  
Temperature Structure ◽  
Low Resolution ◽  
Semi Major Axis ◽  
Species Discovery ◽  
Orbital Parameters

AbstractSince the first discovery of an extra-solar planet around a main-sequence star, in 1995, the number of detected exoplanets has increased enormously. Over the past two decades, observational instruments (both onboard and on ground-based facilities) have revealed an astonishing diversity in planetary physical features (i. e. mass and radius), and orbital parameters (e.g. period, semi-major axis, inclination). Exoplanetary atmospheres provide direct clues to understand the origin of these differences through their observable spectral imprints. In the near future, upcoming ground and space-based telescopes will shift the focus of exoplanetary science from an era of “species discovery” to one of “atmospheric characterization”. In this context, the Atmospheric Remote-sensing Infrared Exoplanet Large (Ariel) survey, will play a key role. As it is designed to observe and characterize a large and diverse sample of exoplanets, Ariel will provide constraints on a wide gamut of atmospheric properties allowing us to extract much more information than has been possible so far (e.g. insights into the planetary formation and evolution processes). The low resolution spectra obtained with Ariel will probe layers different from those observed by ground-based high resolution spectroscopy, therefore the synergy between these two techniques offers a unique opportunity to understanding the physics of planetary atmospheres. In this paper, we set the basis for building up a framework to effectively utilise, at near-infrared wavelengths, high-resolution datasets (analyzed via the cross-correlation technique) with spectral retrieval analyses based on Ariel low-resolution spectroscopy. We show preliminary results, using a benchmark object, namely HD 209458 b, addressing the possibility of providing improved constraints on the temperature structure and molecular/atomic abundances.

scholarly journals High Resolution Spectroscopy of Symbiotic Stars

1990 ◽  
Vol 122 ◽  
pp. 444-445
Author(s):  
Hugo E. Schwarz ◽  
Hilmar W. Duerbeck ◽  
Waltraut C. Seitter
Keyword(s):  
High Resolution ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
High Resolution Spectroscopy ◽  
Symbiotic Stars ◽  
Current Interest ◽  
Echelle Spectrograph ◽  
La Palma ◽  
Recurrent Nova ◽  
The Uk

A high resolution spectroscopy survey of symbiotic stars is conducted in the southern hemisphere by the authors, using the Coudé Echelle Spectrograph (CES), equipped with a CCD at the ESO Coudé Auxiliary Telescope (CAT), and concurrently in the northern hemisphere by Bode, Evans, Meaburn and collaborators, using the UK facilities at La Palma. So far, more than 400 spectra of about 70 stars have been obtained, mostly during 1988 and 1989. The southern part of the work will be described below.The discussion of symbiotic stars in the context of novae is not far-fetched. A number of symbiotics are known to have nova-like outbursts, and several novae are not easily distinguished from symbiotic stars. A noteworthy example is the most recently recognized recurrent nova, V745 Sco, first observed by Liller on July 24, 1989. It is described here, both because in late decline it represents a link between novae and symbiotic stars, and because of its current interest.

scholarly journals Searching for H2 emission from protoplanetary disks using near- and mid-infrared high-resolution spectroscopy

2007 ◽  
Vol 3 (S249) ◽  
pp. 359-368
Author(s):  
A. Carmona ◽  
M. E. van den Ancker ◽  
Th. Henning ◽  
Ya. Pavlyuchenkov ◽  
C. P. Dullemond ◽  
...  
Keyword(s):  
Surface Layer ◽  
High Resolution ◽  
Near Infrared ◽  
Protoplanetary Disks ◽  
High Resolution Spectroscopy ◽  
Disk Model ◽  
Mid Infrared ◽  
T Tauri ◽  
Hα Emission ◽  
Ir Emission

AbstractThe mass and dynamics of protoplanetary disks are dominated by molecular hydrogen (H2). However, observationally very little is known about the H2. In this paper, we discuss two projects aimed to constrain the properties of H2 in the disk's planet forming region (R<50AU). First, we present a sensitive survey for pure-rotational H2 emission at 12.278 and 17.035 μm in a sample of nearby Herbig Ae/Be and T Tauri stars using VISIR, ESO's VLT high-resolution mid-infrared spectrograph. Second, we report on a search for H2 ro-vibrational emission at 2.1228, 2.2233 and 2.2477 μm in the classical T Tauri star LkHα 264 and the debris disk 49 Cet employing CRIRES, ESO's VLT high-resolution near-infrared spectrograph.VISIR project: none of the sources show H2 mid-IR emission. The observed disks contain less than a few tenths of MJupiter of optically thin H2 at 150 K, and less than a few MEarth at T>300 K. % and higher T. Our non-detections are consistent with the low flux levels expected from the small amount of H2 gas in the surface layer of a Chiang and Goldreich (1997) Herbig Ae two-layer disk model. In our sources the H2 and dust in the surface layer have not significantly departed from thermal coupling (Tgas/Tdust<2) and the gas-to-dust ratio in the surface layer is very likely <1000.CRIRES project: The H2 lines at 2.1218 μm and 2.2233 μm are detected in LkHα 264. An upper limit on the 2.2477 μm H2 line flux in LkHα 264 is derived. 49 Cet does not exhibit H2 emission in any of observed lines. There are a few MMoon of optically thin hot H2 in the inner disk (∼0.1 AU) of LkHα 264, and less than a tenth of a MMoon of hot H2 in the inner disk of 49 Cet. The shape of the 1–0 S(0) line indicates that LkHα disk is close to face-on (i<35o). The measured 1–0 S(0)/1–0 S(1) and 2–1 S(1)/1–0 S(1) line ratios in LkHα 264 indicate that the H2 is thermally excited at T<1500 K. The lack of H2 emission in the NIR spectra of 49 Cet and the absence of Hα emission suggest that the gas in the inner disk of 49 Cet has dissipated.

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