Solar atlas revised

Molaro, P.; Monai, S.

doi:10.1051/0004-6361/201118675

Cited by 25 publications

(29 citation statements)

References 23 publications

(24 reference statements)

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“…Since in 2006, the year of the reference spectrum, the Sun showed six solar spots, slightly less than the 14 of the epoch of the present observations, we assume that the radial velocity differences reflect uncertainties more likely coming from the reference spectrum used as an input list, i.e. the subset of the line list provided by Molaro & Monai (2012) which was generated from HARPS spectra of CERES calibrated with a conventional Th-Ar technique. The standard deviation of the distribution of the deviations of the line position with respect to derived radial velocity returned by the DAOSPEC analysis is of ≈260 m s −1 and of ≈60 m s −1 in the blue and red, respectively.…”

Section: Measuring Solar Line Positionsmentioning

confidence: 98%

“…3. For the initial line list we have adopted the one derived by Molaro & Monai (2012) in their HARPS solar data, which contains many strong and unblended lines in the spectral region covered by the LFC. We set a threshold of 0.0025 nm for the minimum equivalent width (EW) to avoid problems with relatively weak lines and performed the analysis on the two different HARPS CCDs separately.…”

Section: Measuring Solar Line Positionsmentioning

confidence: 99%

“…Disk-integrated solar spectra were taken with the unfocused sunlight NSO FTS spectra (Gray & Livingstone 1997;Wallace et al 2011). Molaro & Centurion (2011) and Molaro & Monai (2012) used HARPS spectra of asteroids to improve the precision of the line position relative to those provided by FTS spectra.…”

Section: Introductionmentioning

confidence: 99%

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A frequency comb calibrated solar atlas

Molaro

Esposito²,

Monai

et al. 2013

A&A

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Context. The solar spectrum is a primary reference for the study of physical processes in stars and their variation during activity cycles. High resolution spectra of the Sun are easily obtained from spatially selected regions of the solar disk, while those taken over the integrated disk are more problematic. However, a proxy can be obtained by using solar light reflected by small bodies of the solar system. Aims. In November 2010 an experiment with a prototype of a laser frequency comb (LFC) calibration system was performed with the HARPS spectrograph of the 3.6m ESO telescope at La Silla during which high signal-to-noise spectra of the Moon were obtained. We exploit those Echelle spectra to study a portion of the optical integrated solar spectrum and in particular to determine the solar photospheric line positions. Methods. The DAOSPEC program is used to measure solar line positions through Gaussian fitting in an automatic way. The solar spectra are calibrated both with an LFC and a Th-Ar. Results. We first apply the LFC solar spectrum to characterize the CCDs of the HARPS spectrograph. The comparison of the LFC and Th-Ar calibrated spectra reveals S-type distortions on each order along the whole spectral range with an amplitude of ±40 m s −1 . This confirms the pattern found in the first LFC experiment on a single order and extends the detection of the distortions to the whole analyzed region revealing that the precise shape varies with wavelength. A new data reduction is implemented to deal with CCD pixel inequalities to obtain a wavelength corrected solar spectrum. By using this spectrum we provide a new LFC calibrated solar atlas with 400 line positions in the range of 476-530, and 175 lines in the 534-585 nm range corresponding to the LFC bandwidth. The new LFC atlas is consistent on average with that based on FTS solar spectra, but it improves the accuracy of individual lines by a significant factor reaching a mean value of ≈10 m s −1 . Conclusions. The LFC-based solar line wavelengths are essentially free of major instrumental effects and provide a reference for absolute solar line positions at the date of Nov. 2010, i.e. an epoch of low solar activity. We suggest that future LFC observations could be used to trace small radial velocity changes of the whole solar photospheric spectrum in connection with the solar cycle and for direct comparison with the predicted line positions of 3D radiative hydrodynamical models of the solar photosphere. The LFC calibrated solar atlas can be also used to verify the accuracy of ground or space spectrographs by means of the solar spectrum.

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Section: Measuring Solar Line Positionsmentioning

confidence: 98%

Section: Measuring Solar Line Positionsmentioning

confidence: 99%

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A frequency comb calibrated solar atlas

Molaro

Esposito²,

Monai

et al. 2013

A&A

Self Cite

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“…The solar spectra correspond to two observations of asteroids (Ceres and Vesta) and one observation of one of Jupiter's moons (Ganymede). We could obtain them directly from the public archive thanks to Molaro & Monai (2012), who presented a detailed analysis of absorption lines of the those spectra. Additionally, we co-added those spectra to have a solar spectrum with higher S/N.…”

Section: Harps Spectramentioning

confidence: 99%

TheGaiaFGK benchmark stars

Blanco-Cuaresma¹,

Soubiran²,

Jofré³

et al. 2014

A&A

145

174

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Context. An increasing number of high-resolution stellar spectra is available today thanks to many past and ongoing spectroscopic surveys. Consequently, numerous methods have been developed to perform an automatic spectral analysis on a massive amount of data. When reviewing published results, biases arise and they need to be addressed and minimized. Aims. We are providing a homogeneous library with a common set of calibration stars (known as the Gaia FGK benchmark stars) that will allow us to assess stellar analysis methods and calibrate spectroscopic surveys. Methods. High-resolution and signal-to-noise spectra were compiled from different instruments. We developed an automatic process to homogenize the observed data and assess the quality of the resulting library. Results. We built a high-quality library that will facilitate the assessment of spectral analyses and the calibration of present and future spectroscopic surveys. The automation of the process minimizes the human subjectivity and ensures reproducibility. Additionally, it allows us to quickly adapt the library to specific needs that can arise from future spectroscopic analyses.

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“…The determination of the log(g f ) and the central wavelength can change depending on the stars used for calibration (e.g. convection inside the star may have an effect on the central wavelength of a given stellar line, see Molaro & Monai 2012). Thus, small additional adjustments in both log(g f ) and the central wavelength using additional calibration stars can further improve the modeling of these lines.…”

Section: Dib Extraction Using the New Line Listmentioning

confidence: 99%

Measuring diffuse interstellar bands with cool stars

Monreal-Ibero

Lallement

2017

A&A

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Context. Diffuse Stellar Bands (DIBs) are ubiquitous in stellar spectra. Traditionally, they have been studied through their extraction from hot (early-type) stars, because of their smooth continuum. In an era where there are several going-on or planned massive Galactic surveys using multi-object spectrographs, cool (late-type) stars constitute an appealing set of targets. However, from the technical point of view, the extraction of DIBs in their spectra is more challenging due to the complexity of the continuum. Aims. In this contribution we will provide the community with an improved set of stellar lines in the spectral regions associated to the strong DIBs at λ6196.0, λ6269.8, λ6283.8, and λ6379.3. These lines will allow for the creation of better stellar synthetic spectra, reproducing the background emission and a more accurate extraction of the magnitudes associated with a given DIB (e.g. equivalent width, radial velocity). Methods. The Sun and Arcturus were used as representative examples of dwarf and giant stars, respectively. A high quality spectrum for each of them was modeled using TURBOSPECTRUM and the VALD stellar line list. The oscillator strength log(g f ) and/or wavelength of specific lines were modified to create synthetic spectra where the residuals in both the Sun and Arcturus were minimized. Results. The TURBOSPECTRUM synthetic spectra based on the improved line lists reproduce the observed spectra for the Sun and Arcturus in the mentioned spectral ranges with greater accuracy. Residuals between the synthetic and observed spectra are always ∼ < 10%, much better than with previously existing options. The new line list has been tested with some characteristic spectra, from a variety of stars, including both giant and dwarf stars, and under different degrees of extinction. As it happened with the Sun and Arcturus residuals in the fits used to extract the DIB information are smaller when using synthetic spectra made with the updated line lists. Tables with the updated parameters are provided to the community.

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Solar atlas revised

Cited by 25 publications

References 23 publications

A frequency comb calibrated solar atlas

A frequency comb calibrated solar atlas

TheGaiaFGK benchmark stars

Measuring diffuse interstellar bands with cool stars

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