Carbon12C/13C isotope ratio ofαAurigae revised

Sablowski, D. P.; Järvinen, S. P.; Ilyin, I.; Strassmeier, K. G.

doi:10.1051/0004-6361/201834663

Cited by 9 publications

(4 citation statements)

References 37 publications

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“…The orbital solution of this system provides the most precise masses for giant stars at two very specific positions in the H-R diagram. Just recently, high-resolution spectroscopy revised the 12 C/ 13 C ratio of the primary and finally put it into agreement with current evolutionary tracks (Sablowski et al 2019). Capella is also an interactive binary system.…”

Section: Target Samplementioning

confidence: 64%

BRITE photometry and STELLA spectroscopy of bright stars in Auriga: Rotation, pulsation, orbits, and eclipses

Strassmeier

Granzer

Weber

et al. 2020

A&A

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Context. Knowing rotational and pulsational periods across the Hertzsprung-Russell diagram is of top priority for understanding stellar activity as a function of time. Aims. We aim to determine periods for bright stars in the Auriga field that are otherwise not easily accessible for ground-based photometry. Methods. Continuous photometry with up to three BRITE satellites was obtained for 12 targets and subjected to a period search. Contemporaneous high-resolution optical spectroscopy with STELLA was used to obtain radial velocities through cross correlation with template spectra as well as to determine astrophysical parameters through a comparison with model spectra. Results. The Capella red light curve was found to be constant over 176 days with a root mean square of 1 mmag, but the blue light curve showed a period of 10.1 ± 0.6 d, which we interpret to be the rotation period of the G0 component. From STELLA we obtained an improved orbital solution based on 9600 spectra from the previous 12.9 yr. We derive masses precise to ≈0.3% but 1% smaller than previously published. The BRITE light curve of the F0 supergiant ε Aur suggests 152 d as its main pulsation period, while the STELLA radial velocities reveal a clear 68 d period. An ingress of an eclipse of the ζ Aur binary system was covered with BRITE and a precise timing for its eclipse onset derived. A possible 70 d period fits the proposed tidal-induced, nonradial pulsations of this ellipsoidal K4 supergiant. η Aur is identified as a slowly pulsating B (SPB) star with a main period of 1.29 d and is among the brightest SPB stars discovered so far. The rotation period of the magnetic Ap star θ Aur is detected from photometry and spectroscopy with a period of 3.6189 d and 3.6177 d, respectively, likely the same within the errors. The radial velocities of this star show a striking non-sinusoidal shape with a large amplitude of 7 km s−1. Photometric rotation periods are also confirmed for the magnetic Ap star IQ Aur of 2.463 d and for the solar-type star κ1 Cet of 9.065 d, and also for the B7 HgMn giant β Tau of 2.74 d. Revised orbital solutions are derived for the eclipsing SB2 binary β Aur, which replaces the initial orbit dating from 1948 for the 27-year eclipsing SB1 ε Aur, and for the RS CVn binary V711 Tau, for which a spot-corrected orbital solution was achieved. The two stars ν Aur and ι Aur are found to be long-term, low-amplitude RV and brightness variables, but provisional orbital elements based on a period of 20 yr and an eccentricity of 0.7 could only be extracted for ν Aur. The variations of ι Aur are due to oscillations with a period of ≈4 yr.

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Section: Target Samplementioning

confidence: 64%

BRITE photometry and STELLA spectroscopy of bright stars in Auriga: Rotation, pulsation, orbits, and eclipses

Strassmeier

Granzer

Weber

et al. 2020

A&A

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“…Eight different fits are obtained for each target. Two for a fitting range over which χ 2 is evaluated of 8001.6-8005.9 Å and 8003.5-8005.9 Å, with the latter being similar to what was used by Sablowski et al (2019). For each of these two runs, the continuum was either fixed or free, and the line list is either that taken from Carlberg et al (2012) or from Plez (priv.…”

Section: Carbon Isotope Ratiomentioning

confidence: 99%

VPNEP: Detailed characterization of TESS targets around the Northern Ecliptic Pole

Strassméier¹,

Weber²,

Gruner³

2023

A&A

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Context. We embarked on a high-resolution optical spectroscopic survey of bright Transiting Exoplanet Survey Satellite (TESS) stars around the Northern Ecliptic Pole (NEP), dubbed the Vatican-Potsdam-NEP (VPNEP) survey. Aims. Our NEP coverage comprises ≈770 square degrees with 1067 stars, of which 352 are bona fide dwarf stars and 715 are giant stars, all cooler than spectral type F0 and brighter than V=8. m 5. Our aim is to characterize these stars for the benefit of future studies in the community. Methods. We analyzed the spectra via comparisons with synthetic spectra. Particular line profiles were analyzed by means of eigenprofiles, equivalent widths, and relative emission-line fluxes (when applicable). Results. Two R=200 000 spectra were obtained for each of the dwarf stars with the Vatican Advanced Technology Telescope (VATT) and the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI), with typically three R=55 000 spectra obtained for the giant stars with STELLA and the STELLA Echelle Spectrograph (SES). Combined with V-band magnitudes, Gaia eDR3 parallaxes, and isochrones from the Padova and Trieste Stellar Evolutionary Code, the spectra can be used to obtain radial velocities, effective temperatures, gravities, rotational and turbulence broadenings, stellar masses and ages, and abundances for 27 chemical elements, as well as isotope ratios for lithium and carbon, line bisector spans, convective blue-shifts (when feasible), and levels of magnetic activity from Hα, Hβ, and the Ca ii infrared triplet. In this initial paper, we discuss our analysis tools and biases, presenting our first results from a pilot sub-sample of 54 stars (27 bona-fide dwarf stars observed with VATT+PEPSI and 27 bona-fide giant stars observed with STELLA+SES) and making all reduced spectra available to the community. We carried out a follow-up error analysis was carried out, including systematic biases and standard deviations based on a joint target sample for both facilities, as well as a comparison with external data sources.

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“…The data of CN lines as well as atomic lines comprised in this region were taken from the list of Carlberg et al (2012). Although we formally included the Fe i line at 8005.049 Å according to Sablowski et al (2019), its contribution turned out to be negligible. These spectral line data we adopted are summarized in table 1.…”

Section: Synthetic Spectrum Fittingmentioning

confidence: 99%

“…This situation motivated us to evaluate these two quantities based on the same observational material used in Paper II, in order to complement our previous studies. For this purpose, we decided to employ a group of 12 CN and 13 CN lines in the ∼ 8002-8005 Å region, which are known to be suitable and commonly used (e.g., Carberg et al 2012;Sablowski et al 2019). That is,, N abundances can be obtained with the help of the already known C abundances because absolute strengths of CN lines depend upon the product of C and N abundances, while 12 C/ 13 C ratios are evaluated from the relative strengths of 12 CN and 13 CN lines.…”

mentioning

confidence: 99%

Photospheric nitrogen abundances and carbon 12C/13C ratios of red giant stars

Takeda,

Omiya,

Harakawa

et al. 2019

Preprint

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Nitrogen abundances and carbon isotope ratios ( 12 C/ 13 C) in the atmospheres of red giants are known to be influenced by dredge-up of H-burning products and serve as useful probes to study the nature of evolution-induced envelope mixing. We determined the [N/Fe] and 12 C/ 13 C ratios for 239 late-G/early-K giant stars by applying the spectrum-fitting technique to the 12 CN and 13 CN lines in the ∼ 8002-8005 Å region, with an aim to investigate how these quantities are related to other similar mixing-affected indicators which were already reported in our previous work. It was confirmed that [N/Fe] values are generally supersolar (typically by several tenths dex though widely differ from star to star), anti-correlated with [C/Fe], and correlated with [Na/Fe], as expected from theory. As seen from their dependence upon stellar parameters, it appears that mixing tends to be enhanced with an increase of stellar luminosity (or mass) and rotational velocity, which is also reasonable from the theoretical viewpoint. In contrast, the resulting 12 C/ 13 C ratios turned out to be considerably diversified in the range of ∼ 5-50 (with a peak around ∼ 20), without showing any systematic dependence upon C or N abundance anomalies caused by the mixing of CN-cycled material. It thus appears that our understanding on the photospheric 12 C/ 13 C ratios in red giants is still incomplete, for which more observational studies would be required.

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Carbon¹²C/¹³C isotope ratio ofαAurigae revised

Cited by 9 publications

References 37 publications

BRITE photometry and STELLA spectroscopy of bright stars in Auriga: Rotation, pulsation, orbits, and eclipses

BRITE photometry and STELLA spectroscopy of bright stars in Auriga: Rotation, pulsation, orbits, and eclipses

VPNEP: Detailed characterization of TESS targets around the Northern Ecliptic Pole

Photospheric nitrogen abundances and carbon 12C/13C ratios of red giant stars

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