The companion of the 18-day classical Cepheid YZ Carinae

Evans, Nancy Remage; Butler, John C.

doi:10.1086/133254

Cited by 4 publications

(5 citation statements)

References 8 publications

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“…The combination of the spectroscopic orbital elements of Gallenne et al (2018b) (which are in agreement with those determined by Anderson et al 2016) and the PMa vectors results in a companion mass of m 2 ≈ 1.9 ± 0.3 M (Paper I) for the companion of the long-period pulsator YZ Car (P = 18.2 d). The interferometric companion search by Gallenne et al (2018b) did not reveal the faint secondary, but established an upper limit of B3V on its spectral type, in agreement with the estimate of B8V-A0V from Evans & Butler (1993) and the mass derived in Paper I, which corresponds to an A-type dwarf.…”

Section: Yz Carsupporting

confidence: 81%

Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2

Kervella

Gallenne

Evans

et al. 2019

A&A

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Context. The multiplicity of classical Cepheids (CCs) and RR Lyrae stars (RRLs) is still imperfectly known, particularly for RRLs. Aims. In order to complement the close-in short orbital period systems presented in Paper I, our aim is to detect the wide, spatially resolved companions of the targets of our reference samples of Galactic CCs and RRLs. Methods. Angularly resolved common proper motion pairs were detected using a simple progressive selection algorithm to separate the most probable candidate companions from the unrelated field stars. Results. We found 27 resolved, high probability gravitationally bound systems with CCs out of 456 examined stars, and one unbound star embedded in the circumstellar dusty nebula of the long-period Cepheid RS Pup. We found seven spatially resolved, probably bound systems with RRL primaries out of 789 investigated stars, and 22 additional candidate pairs. We report in particular new companions of three bright RRLs: OV And (companion of F4V spectral type), RR Leo (M0V), and SS Oct (K2V). In addition, we discovered resolved companions of 14 stars that were likely misclassified as RRLs.Conclusions. The detection of resolved non-variable companions around CCs and RRLs facilitates the validation of their GDR2 parallaxes. The possibility to conduct a detailed analysis of the resolved coeval companions of CCs and old population RRLs will also be valuable to progress on our understanding of their evolutionary path.

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Section: Yz Carsupporting

confidence: 81%

Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2

Kervella

Gallenne

Evans

et al. 2019

A&A

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“…He derived the preliminary spectroscopic orbital parameters, giving A164, page 7 of 21 A&A 622, A164 (2019) an orbital period of 850 d, and suggested a spectral type between B5V and A5V for this companion. Evans & Butler (1993) later tightened the range of spectral type to B8V-A0V from ultraviolet spectra of the companion. Additional RVs were obtained by Bersier (2002), but he did not revise the orbital elements.…”

Section: Yz Carmentioning

confidence: 99%

Multiplicity of Galactic Cepheids from long-baseline interferometry

Gallenne

Kervella

Borgniet

et al. 2019

A&A

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Aims. We aim at detecting and characterizing the main-sequence companions of a sample of known and suspected Galactic binary Cepheids. The long-term objective is to accurately and independently measure the Cepheid masses and distances. Methods. We used the multi-telescope interferometric combiners CHARA/MIRC and VLTI/PIONIER to detect and measure the astrometric positions of the high-contrast companions orbiting 16 bright Galactic Cepheids. We made use of the CANDID algorithm to search for the companions and set detection limits from interferometric observations. We also present new high-precision radial velocity measurements which were used to fit radial pulsation and orbital velocities. Results. We report the detection of the companions orbiting the Cepheids U Aql, BP Cir, and S Mus, possible detections for FF Aql, Y Car, BG Cru, X Sgr, V350 Sgr, and V636 Sco, while no component is detected around U Car, YZ Car, T Mon, R Mus, S Nor, W Sgr, and AH Vel. For U Aql and S Mus, we performed a preliminary orbital fit combining their astrometric measurements with newly obtained high-precision single-line radial velocities, providing the full set of orbital elements and pulsation parameters. Assuming the distance from a period-luminosity (P-L) relation for both Cepheids, we estimated preliminary masses of M U Aql = 4.97 ± 0.62 M and M S Mus = 4.63 ± 0.99 M . For YZ Car, W Sgr, V350 Sgr, and V636 Sco, we revised the spectroscopic orbits using new high-precision radial velocities, while we updated the pulsation parameters for BP Cir, BG Cru, S Nor, and AH Vel. Our interferometric observations also provide measurements of the angular diameters, which can be used in a Baade-Wesselink type analysis. Conclusions. We now have several astrometric detections of Cepheid companions. When radial velocities of the companions are available, such systems will provide accurate and independent masses and distances. Orbital parallaxes with an accuracy better than 5% will be particularly useful for a better calibration of the P-L relation. The final Gaia parallaxes will also be particularly helpful for single-line spectroscopic systems, where mass and distance are degenerate. Mass measurements are necessary for a better understanding of the age and evolution of Cepheids.Article published by EDP Sciences A164, page 1 of 21 A&A 622, A164 (2019)

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“…YZ Car was examined by Evans & Butler (1993) with IUE and using the very weak spectrum obtained they determined that the best fit to the data indicated that the companion was similar to a main‐sequence star between B8V and A0V subtypes, giving a mass range from 2.2–2.9 M ⊙ .…”

Section: Orbital Parametersmentioning

confidence: 99%

“…Because YZ Car is one of the more luminous and larger Cepheids in the sample, and the short orbital period indicates that the stars orbit quite close together, the question of mass exchange should be addressed. Coulson (1983b) and Evans & Butler (1993) concluded that with the likely companion types and the size estimated for the Cepheid, Roche lobe overflow was unlikely.…”

Section: Orbital Parametersmentioning

confidence: 99%

The orbits of southern binary Cepheids

Petterson

Cottrell

Albrow

2004

Monthly Notices of the Royal Astronomical Society

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High‐resolution spectroscopic observations have been made of a number of southern Cepheids. The stars studied were part of a long‐term programme to observe southern variable stars and to complete a data base of radial velocities over a long time interval. The radial velocities have a precision of ∼300 m s−1, allowing the detection of velocity differences of ∼1 km s−1 with confidence. Our new data provide a consistent set of data against which other sources of data can be compared. Masses were determined for two systems, the 9‐d Cepheid S Mus (6.2 ± 0.2 M⊙) and the 5‐d Cepheid V350 Sgr (6.0 ± 0.9 M⊙). For another seven Cepheids (Y Car, YZ Car, AX Cir, BP Cir, V636 Sco, W Sgr and T Mon), new or improved orbital solutions were found. New results presented here include the first orbital solution for AX Cir, a completely revised orbital solution for YZ Car, which established its eccentricity and orbital motion, and a new pulsation period (2.398 19 d) for BP Cir. The pulsational mass determinations provide further confirmation of the convergence of mass determinations between dynamical and evolutionary methods.

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The companion of the 18-day classical Cepheid YZ Carinae

Cited by 4 publications

References 8 publications

Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2

Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2

Multiplicity of Galactic Cepheids from long-baseline interferometry

The orbits of southern binary Cepheids

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