On the coronae of rapidly rotating star. V - The other stars

Walter, Frederick M.

doi:10.1086/131579

Cited by 4 publications

(4 citation statements)

References 8 publications

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“…Some basic properties of the targets and further details on the observing campaign (mean heliocentric Julian date of the observations, typical signal-to-noise ratio) can be found in Tables 1a and b. As will be apparent in the following, one star originally classified as an active binary (HD 28, 33 Psc) actually displays an extremely low level of activity (see also Walter 1985). Tasks implemented in the IRAF 1 package were used to carry out the standard reduction procedures for echelle spectra (i.e.…”

Section: Observational Materialsmentioning

confidence: 99%

The photospheric abundances of active binaries

Morel¹,

Micela²,

Favata

et al. 2004

A&A

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Abstract. We report the determination from high-resolution spectra of the atmospheric parameters and abundances of 13 chemical species (among which lithium) in 8 single-lined active binaries. These data are combined with our previous results for 6 other RS CVn systems to examine a possible relationship between the photospheric abundance patterns and the stellar activity level. The stars analyzed are generally found to exhibit peculiar abundance ratios compared to inactive, Galactic disk stars of similar metallicities. We argue that this behaviour is unlikely to be an artefact of errors in the determination of the atmospheric parameters or non-standard mixing processes along the red giant branch, but diagnoses instead the combined action of various physical processes related to activity. The most promising candidates are cool spot groups covering a very substantial fraction of the stellar photosphere or NLTE effects arising from nonthermal excitation. However, we cannot exclude the possibility that more general shortcomings in our understanding of K-type stars (e.g. inadequacies in the atmospheric models) also play a significant role. Lastly, we call attention to the unreliability of the (V − R) and (V − I) colour indices as temperature indicators in chromospherically active stars.

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Section: Observational Materialsmentioning

confidence: 99%

The photospheric abundances of active binaries

Morel¹,

Micela²,

Favata

et al. 2004

A&A

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“…33 Psc by now has the lowest known magnetic activity among RS CVn stars (Strassmeier et al 1988). Results of Einstein X-ray observations of 33 Psc were presented by Walter (1985). Its surface flux is < 5 • 10 3 erg cm −2 s −1 , which is about a factor of three lover than the flux from the quiet solar corona, and is two orders of magnitude below the surface fluxes observed in the least-active long-period RS CVn systems.…”

Section: Introductionmentioning

confidence: 93%

Chemical Composition of the RS CNn-Type Star 33 Piscium

et al. 2011

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Abundances of 22 chemical elements, including the key elements and isotopes such as 12 C, 13 C, N and O, are investigated in the spectrum of 33 Psc, a single-lined RS CVn-type binary of low magnetic activity. The high resolution spectra were observed on the Nordic Optical Telescope and analyzed with the MARCS model atmospheres. The following main parameters have been determined: T eff = 4750 K, log g = 2.8, [Fe/H] = -0.09, [C/Fe] = -0.04, [N/Fe] = 0.23, [O/Fe] = 0.05, C/N = 2.14, 12 C/ 13 C = 30, which show the first-dredge-up mixing signatures and no extra-mixing.

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“…93 Leo meets several of the established criteria of the RS CVn group: its period is less than 100 d, the primary is an evolved star and rotates more rapidly than normal for its type, and the system exhibits small‐scale photometric variability. It is an X‐ray source, and the measured X‐ray intensity is appropriate to its 72‐d period (Walter 1985). On the other hand, the mass and the radius of the primary exceed those of the group studied by Popper & Ulrich (1977), and furthermore the component stars are well detached, so the mild mass exchange which proved central to their explanation of the emission properties seems unlikely.…”

Section: Chromospheric Emission In 93 Leomentioning

confidence: 99%

Composite spectra Paper 13: 93 Leonis, a chromospherically-active binary

Griffin

2004

Monthly Notices of the Royal Astronomical Society

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We isolate the spectrum of the secondary component of the composite‐binary system 93 Leonis by spectrum subtraction, classify it, and measure the mass ratio of the system. An accurate visual orbit and a well‐determined parallax provide reliable measurements of orbital inclination and distance, enabling us to determine precisely the individual masses and other stellar parameters. The primary star is of type ∼G7 III, and the secondary is a rapidly rotating star of type A7 IV. Our photographic spectra at 10 Å mm−1 are invaluable for accurate spectral classification in such cases. By combining 23 measurements of the secondary's velocity with 102 of the primary's and deriving a double‐lined orbit, we determine the mass ratio (q=M1/M2) of 93 Leo to be 1.09 ± 0.04. The same value is derived by cross‐correlating high‐dispersion spectra of 93 Leo B extracted from opposite nodal phases. That value of q is consonant with previous research, but its precision is considerably improved. We show that random errors arising from the cross‐correlation of broad, weak features constitute a natural limit to that precision. The derived masses of M1= 2.2 M⊙, M2= 2.0 M⊙ for the giant and dwarf, respectively, constrain the choice of models for fitting evolutionary tracks in the (log Teff, log L) plane. The giant is almost certainly on its first ascent of the red giant branch, and the dwarf has evolved significantly from the main sequence. The stars fit an isochrone for log(age) = 8.95, about 0.9 Gyr. Metallicity near to solar is suggested by the close correspondence between the component spectra and those of the respective solar‐abundance standards. The primary in 93 Leo displays a marked level of chromospheric activity. By combining our high‐dispersion spectra we are able to isolate emission in the Ca ii K line. The chromospheric material has a small infall velocity, giving rise to a disc‐averaged redshift of about 4 km s−1, and an unchanging velocity profile which can be attributed to a large number of small, active events like prominences across the surface. While we can say that there was no perceptible change in the emission strength over an interval of 4 months, we have not made systematic observations to monitor its long‐term stability. We contrast the components of 93 Leo with those of α Equ, whose analysis was the subject of Paper 11 in this series. The primary components are very similar, but the two secondary components are extremely different in nature: whereas 93 Leo B is a broad‐lined, apparently normal A star, the secondary of α Equ is a sharp‐lined Am star of type ∼kA3hA4mA9. We question why that should be, and recommend that a greater emphasis be placed on extracting accurate stellar parameters from the components of spectroscopic binaries as a means towards a better understanding of the vagaries of stellar evolution. 93 Leo has a 9‐mag visual companion which appears to be a physical member of the system and to be a single‐lined spectroscopic binary with a period of the order of a century.

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On the coronae of rapidly rotating star. V - The other stars

Cited by 4 publications

References 8 publications

The photospheric abundances of active binaries

The photospheric abundances of active binaries

Chemical Composition of the RS CNn-Type Star 33 Piscium

Composite spectra Paper 13: 93 Leonis, a chromospherically-active binary

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