On the rotation period of Capella

Strassmeier, K. G.; Reegen, P.; Granzer, T.

doi:10.1002/1521-3994(200106)322:2<115::aid-asna115>3.0.co;2-j

Cited by 8 publications

(2 citation statements)

References 18 publications

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“…Continuous Hα and Hβ photometry for the years 1996-2000 was presented earlier by as part of a paper on the magnetically-active star Capella. From 2001 until 2008, the same filter in Hα of 31-Å full width half maximum (FWHM) was employed as before and with the same EMI-9828 photomultiplier tube (see Strassmeier et al 2001 for a filter description). During the initial observations in 1996/97 we also used Strömgren b, y filters on the sister telescope Wolfgang for a short period Table 2.…”

Section: Time-series Apt Photometry 1996-2013mentioning

confidence: 99%

Time‐series high‐resolution spectroscopy and photometry of ε Aurigae from 2006–2013: Another brick in the wall

et al. 2014

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We present continuous and time-resolved R = 55 000 opticaléchelle spectroscopy of Aurigae from [2006][2007][2008][2009][2010][2011][2012][2013] We conclude that Hα is contaminated by changes in the circumstellar environment while the Hβ and V I photometry stems predominantly from the non radial pulsations of the F0 supergiant. We isolate the disk-rotation profile from 61 absorption lines and found that low disk eccentricity generally relates to low disk rotational velocity (but not always) while high disk eccentricity always relates to high velocity. There is also the general trend that the disk-absorption in spectral lines with higher excitation potential comes from disk regions with higher eccentricity and thus also with higher rotational velocity. The dependency on transition probability is more complex and shows a bi-modal trend. The outskirts of the disk is distributed asymmetrically around the disk and appears to have been built up mostly in a tail along the orbit behind the secondary. Our data show that this tail continues to eclipse the F0 Iab primary star even two years after the end of the photometric eclipse. High-resolution spectra were also taken of the other, bona-fide, visual-binary components of Aur (ADS 3605BCDE). Only the C-component, a K3-4-giant, appears at the same distance than Aur but its radial velocity is in disagreement with a bound orbit. The other components are a nearby (≈ 7 pc) cool DA white dwarf, a G8 dwarf, and a B9 supergiant, and not related to Aur. The cool white dwarf shows strong DIB lines that suggest the existence of a debris disk around this star.

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Section: Time-series Apt Photometry 1996-2013mentioning

confidence: 99%

Time‐series high‐resolution spectroscopy and photometry of ε Aurigae from 2006–2013: Another brick in the wall

et al. 2014

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“…Values are rounded to 0.0001, except those listed in Col. 3. References: (1)Williams ( 2016), (2) Hummel et al (1994) and (3) Strassmeier et al (2001).…”

Section: Data Availabilitymentioning

confidence: 99%

Power-law relationship between the semi-major axis and the rotation period ratio in an eccentric system: Its physical meaning and applications

Dai

2024

Preprint

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This study aims to address longstanding questions about orbital motion, introduces a synchronous orbit radius ratio and investigates the relationship between the semi-major axes and synchronous orbit radius ratios of known systems with the same mass ratio orders of magnitude, the same spin–orbit angles and eccentric or circular orbits, including binaries, star–planet systems and planet–moon systems. The results of this work show that in a system with an eccentric orbit (e > 0.01) and a mass ratio order with a magnitude higher than −7.5217, the semi-major axis exhibits a power-law distribution relationship with the product of the mass ratio and square of the rotation period ratio. Furthermore, under spin–orbit alignment conditions, the power-law exponent exhibits a positive linear relationship with the mass ratio order of magnitude and is greater than zero and less than or equal to one. Moreover, the power-law exponent for a spin–orbit misaligned system correlates negatively with its spin–orbit angle. This power-law relationship was derived based on a drag force caused by the gravitational field rotation proposed by extending Einstein’s equivalence principle. This study concludes that the power-law relationship and drag force dominate the formation of various orbits.

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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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On the rotation period of Capella

Cited by 8 publications

References 18 publications

Time‐series high‐resolution spectroscopy and photometry of ε Aurigae from 2006–2013: Another brick in the wall

Time‐series high‐resolution spectroscopy and photometry of ε Aurigae from 2006–2013: Another brick in the wall

Power-law relationship between the semi-major axis and the rotation period ratio in an eccentric system: Its physical meaning and applications

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

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