Multiplicity of Galactic Cepheids and RR Lyrae stars from <i>Gaia</i> DR2

Kervella, P.; Gallenne, A.; Evans, Nancy Remage; Szabados, László; Arenou, Frédéric; Mérand, A.; Nardetto, N.; Gieren, W.; Pietrzyński, G.

doi:10.1051/0004-6361/201834211

Cited by 48 publications

(55 citation statements)

References 226 publications

(322 reference statements)

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“…According to the orbital elements and the estimate of the orbital inclination by Welch et al (1987, i = 74 • , using the mass function and the assumed masses 7 M for U Aql and 2 M for its companion), the projected semi-major axis is expected to be ∼9 mas. This value is consistent with the 9.5 mas estimate of Kervella et al (2019) using the values of the spectroscopic orbit and the PM vectors (and assuming a mass of 5.2 M for the Cepheid). The available baselines at CHARA allow us to spatially resolve such separation.…”

Section: U Aqlsupporting

confidence: 87%

“…4. Analysis of the PM vectors (Kervella et al 2019) provides an approximate mass of 1.9 ± 0.3 M , which is consistent with the expected range of spectral types.…”

Section: Yz Carsupporting

confidence: 77%

“…This would correspond to a very high contrast of ∆H 8.7 mag. We also note that Kervella et al (2019) did not detect a significant anomaly in the PM vectors, suggesting a very long period or a very low mass companion.…”

Section: U Carmentioning

confidence: 61%

“…From HST/GHRS measurements, Bohm-Vitense et al (1997) measured its orbital velocity amplitude to estimate its mass to be 3.8 ± 1.2 M . Kervella et al (2019) derived a similar mass from the analysis of the PM vectors. However, Evans et al (2005) later obtained HST/STIS spectra of this hot companion and found a large variation in the RV in a short timescale, that is a 7 km s −1 change in 4 days.…”

Section: Y Carmentioning

confidence: 99%

“…Recently, Kervella et al (2019) searched for close-in companions from the signature of their orbital motion on the proper motion vector, i.e. by comparing the HIPPARCOS and Gaia proper motions (PMs) to the mean PM.…”

Section: Introductionmentioning

confidence: 99%

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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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Section: U Aqlsupporting

confidence: 87%

“…4. Analysis of the PM vectors (Kervella et al 2019) provides an approximate mass of 1.9 ± 0.3 M , which is consistent with the expected range of spectral types.…”

Section: Yz Carsupporting

confidence: 77%

Section: U Carmentioning

confidence: 61%

Section: Y Carmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multiplicity of Galactic Cepheids from long-baseline interferometry

Gallenne

Kervella

Borgniet

et al. 2019

A&A

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On Cepheid Distances in the $${H}_{0}$$ Measurement

Anderson

2024

Springer Series in Astrophysics and Cosmology

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Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2

Kervella

Gallenne

Evans

et al. 2019

A&A

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Context. Classical Cepheids (CCs) and RR Lyrae stars (RRLs) are important classes of variable stars used as standard candles to estimate galactic and extragalactic distances. Their multiplicity is imperfectly known, particularly for RRLs. Astoundingly, to date only one RRL has convincingly been demonstrated to be a binary, TU UMa, out of tens of thousands of known RRLs. Aims. Our aim is to detect the binary and multiple stars present in a sample of Milky Way CCs and RRLs. Methods. In the present article, we combine the HIPPARCOS and Gaia DR2 positions to determine the mean proper motion of the targets, and we search for proper motion anomalies (PMa) caused by close-in orbiting companions. Results. We identify 57 CC binaries from PMa out of 254 tested stars and 75 additional candidates, confirming the high binary fraction of these massive stars. For 28 binary CCs, we determine the companion mass by combining their spectroscopic orbital parameters and astrometric PMa. We detect 13 RRLs showing a significant PMa out of 198 tested stars, and 61 additional candidates. Conclusions. We determine that the binary fraction of CCs is likely above 80%, while that of RRLs is at least 7%. The newly detected systems will be useful to improve our understanding of their evolutionary states. The discovery of a significant number of RRLs in binary systems also resolves the long-standing mystery of their extremely low apparent binary fraction.

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Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2

Cited by 48 publications

References 226 publications

Multiplicity of Galactic Cepheids from long-baseline interferometry

Multiplicity of Galactic Cepheids from long-baseline interferometry

On Cepheid Distances in the $${H}_{0}$$ Measurement

Multiplicity of Galactic Cepheids and RR Lyrae stars from Gaia DR2

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