Solar rotation inferred from radial velocities of the Sun-as-a-star during the 2012 May 21 eclipse

Takeda, Yoichi; Ohshima, Osamu; Kambe, Eiji; Toda, H.; Koyano, Hisashi; Sato, Bun’ei; Nakamura, Yasuhisa; Narita, Norio; Sekii, T.

doi:10.1093/pasj/psu139

Cited by 5 publications

(8 citation statements)

References 15 publications

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“…The oxygen NLTE abundance was first determined by Kodaira and Tanaka (1972) and Johnson (1974) for stars and by Shchukina (1987) for the Sun. Subsequently, more comprehensive oxygen model atoms were constructed by Kiselman (1991), Carlsson and Judge (1993), Takeda (1992), Paunzen et al (1999), Reetz (1999), Mishenina et al (2000), and Przybilla et al (2000). Non-LTE leads to a strengthening of O I IR lines and, consequently, to a decrease in the abundance derived from these lines.…”

Section: Introductionmentioning

confidence: 99%

Influence of Inelastic Collisions with Hydrogen Atoms on Non-LTE Oxygen Abundance Determinations

Sitnova¹,

Mashonkina²

2018

Astron. Lett.

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We present the non-local thermodynamic equilibrium (non-LTE) calculations for O I with the updated model atom that includes quantum-mechanical rate coefficients for O I + H I inelastic collisions from the recent study of Barklem (2018). The non-LTE abundances from the O I lines were determined for the Sun and 46 FG stars in a wide metallicity range, −2.6 < [Fe/H] < 0.2. An application of accurate atomic data leads to larger departures from LTE and lower oxygen abundances compared to that for the Drawin's theoretical approximation. For the infrared O I 7771-5Å triplet lines, the change in the non-LTE abundance is −0.11 dex for the solar atmospheric parameters and decreases in absolute value towards lower metallicity. We revised the [O/Fe]-[Fe/H] trend derived in our earlier study. The change in [O/Fe] is small in the [Fe/H] range from -1.5 to 0.2. For stars with [Fe/H] < -1, the [O/Fe] ratio has increased such that [O/Fe] = 0.60 at [Fe/H] = -0.8 and increases up to [O/Fe] = 0.75 at [Fe/H] = -2.6. * sitnova@inasan.ru

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Section: Introductionmentioning

confidence: 99%

Influence of Inelastic Collisions with Hydrogen Atoms on Non-LTE Oxygen Abundance Determinations

Sitnova¹,

Mashonkina²

2018

Astron. Lett.

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“…To check our non-LTE method for supergiants, we determine the oxygen abundance for Deneb (Table 12). We do not use the IR lines, because they are very strong; the observed equivalent width for the 7771Å line is 550 mÅ (Takeda 1992). The mean LTE and non-LTE abundances from three O I lines are log ε = 8.76 ± 0.03 and log ε = 8.57 ± 0.01, respectively.…”

Section: The Non-lte Correction For Model Atmospheres With Different mentioning

confidence: 99%

Influence of Departures from LTE on Oxygen Abundance Determination in the Atmospheres of A – K stars

et al. 2013

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Abstract. Solar oxygen abundance is a key parameter for the studies of solar physics. Oxygen abundances of cool stars with different metallicities are important for understanding the galactic chemical evolution. We present non-LTE calculations for O I with the classical plane-parallel (1D) model atmospheres for a set of stellar parameters corresponding to stars of spectral types from A to K. Non-LTE leads to strengthening the O I lines, and the difference between the non-LTE and LTE abundances (non-LTE correction) is negative. The departures from LTE grow toward higher effective temperature and lower surface gravity. In the entire temperature range and log g = 4, the non-LTE correction does not exceed 0.05 dex in absolute value for lines of O I in the visible spectral range. The non-LTE corrections are significantly larger for the infrared O I 7771-5, 8446Å lines and reach an order of magnitude for A-type stars. To differentiate the effects of inelastic collisions with electrons and neutral hydrogen atoms on the statistical equilibrium (SE) of O I, we derived the oxygen abundance for the five well studied A-type stars. For each star, non-LTE largely removes the difference between the infrared and visible lines found in LTE. In the case of cool stars (Sun and Procyon), inelastic collisions with H I affect the SE of O I, and agreement between the abundances from different lines is achieved when using the Drawin's formalism for collisional rates calculations. The solar mean oxygen abundance from the six lines is log ε = 8.74 ± 0.05, when using the MAFAGS-OS solar model atmosphere and log ε = 8.78 ± 0.03, when applying the 3D corrections taken from the literature. The non-LTE abundances of oxygen are derived for the sample of cool dwarfs with various metallicities on high-resolution spectra observed in the Lick observatory.

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“…Major parts of eclipse research concern the corona (e.g., Saito & Tandberg-Hanssen 1973;Habbal et al 2011;Koutchmy et al 2019). However, observations in the visible spectrum, as well as in the adjacent infrared (IR), ultraviolet (UV), and extreme ultraviolet (EUV) bands, are popular in solar physics (e.g., Dunn et al 1968;Bazin & Koutchmy 2013), solar-stellar connection studies (Schleicher et al 2004), and exoplanet research (e.g., Takeda et al 2015;Reiners et al 2016). Albeit rarely in the focus of eclipse observations, manifestations of magnetic activity are interesting because they affect the radial velocity measurements of active stars (Haywood et al 2016;Cauley et al 2018, e.g.,).…”

Section: Introductionmentioning

confidence: 99%

Sun-as-a-star observations of the 2017 August 21 solar eclipse

et al. 2019

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The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) is a state-of-the-art, thermally stabilized, fiber-fed, high-resolution spectrograph for the Large Binocular Telescope (LBT) at Mt. Graham, Arizona. During daytime the instrument is fed with sunlight from the 10-millimeter aperture, fully automated, binocular Solar Disk-Integrated (SDI) telescope. The observed Sun-as-a-star spectra contain a multitude of photospheric and chromospheric spectral lines in the wavelength ranges 4200–4800 Å and 5300–6300 Å. One of the advantages of PEPSI is that solar spectra are recorded in the exactly same manner as nighttime targets. Thus, solar and stellar spectra can be directly compared. PEPSI/SDI recorded 116 Sun-as-a-star spectra during the 2017 August 21 solar eclipse. The observed maximum obscuration was 61.6%. The spectra were taken with a spectral resolution of ≈ 250000 and an exposure time of 0.3 s. The high-spectral resolution facilitates detecting subtle changes in the spectra while the Moon passes the solar disk. Sun-as-a-star spectra are affected by changing contributions due to limb darkening and solar differential rotation, and to a lesser extend by supergranular velocity pattern and the presence of active regions on the solar surface. The goal of this study is to investigate the temporal evolution of the chromospheric Na D doublet during the eclipse and to compare observations with synthetic line profiles computed with the state-of-the-art Bifrost code.

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Solar rotation inferred from radial velocities of the Sun-as-a-star during the 2012 May 21 eclipse

Cited by 5 publications

References 15 publications

Influence of Inelastic Collisions with Hydrogen Atoms on Non-LTE Oxygen Abundance Determinations

Influence of Inelastic Collisions with Hydrogen Atoms on Non-LTE Oxygen Abundance Determinations

Influence of Departures from LTE on Oxygen Abundance Determination in the Atmospheres of A – K stars

Sun-as-a-star observations of the 2017 August 21 solar eclipse

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