Classical Cepheid Masses: U Aquilae

Evans, Nancy Remage; Böhm‐Vitense, Erika; Carpenter, Kenneth G.; Beck-Winchatz, Bernhard; Robinson, Richard D.

doi:10.1086/305242

Cited by 23 publications

(15 citation statements)

References 20 publications

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“…Figure 6 summarizes the information currently available for Cepheid masses. (Luminosities are taken from Evans et al [1998].) For comparison, the luminosity predicted for the tips of the blue loops of the evolutionary tracks from several groups is shown.…”

Section: Discussionmentioning

confidence: 99%

Cepheid Masses:FUSEObservations of S Muscae

Evans

Massa

Fullerton

et al. 2006

ApJ

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S Mus is the Cepheid with the hottest known companion. The large ultraviolet flux means that it is the only Cepheid companion for which the velocity amplitude could be measured with the echelle mode of the HST GHRS. Unfortunately, the high temperature is difficult to constrain at wavelengths longer than 1200 8 because of the degeneracy between temperature and reddening. We have obtained a FUSE spectrum in order to improve the determination of the temperature of the companion. Two regions that are temperature sensitive near 16,000 K but relatively unaffected by H 2 absorption (940 8 and the Ly wings) have been identified. By comparing FUSE spectra of S Mus B with spectra of standard stars, we have determined a temperature of 17;000 AE 500 K. The resulting Cepheid mass is 6:0AE 0:4 M . This mass is consistent with main-sequence evolutionary tracks with a moderate amount of convective overshoot.

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Section: Discussionmentioning

confidence: 99%

Cepheid Masses:FUSEObservations of S Muscae

Evans

Massa

Fullerton

et al. 2006

ApJ

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“…Since the evolu-0.2H p tionary timescale decreases only gradually toward TAMS, the observational fact may indicate that the actual extent of the core overshooting is smaller than 0.2H p . The mass-luminosity relation of Cepheids appears to be consistent with a moderate core overshooting (e.g., Evans et al 1998). It is known, however, that theoretical Cepheid loops of for Population I abundance become M [ 6 M _ too short to enter the instability strip if a moderate core overshooting is included under the OPAL opacities (e.g., Schaller et al 1992).…”

Section: Introduction : Calibration For Extent Of Overshootingmentioning

confidence: 88%

A Comparison of Stellar Evolution with Binary Systems

Iwamoto

Saio

1999

ApJ

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We have compared stellar evolution models with the three intermediate-mass binary systems V2291 Oph, a Aur, and g And, whose masses are determined accurately within 7%. These systems were recently regarded by and coworkers as systems that favor evolution with moderate overshoot mixing Schro der from the convective cores. While they assumed a standard Population I metallicity for these binaries, we have taken into account the available heavy-element abundance data in the literature. We have taken two approaches for each system. First, assuming no core overshooting, we have adjusted helium abundance for each binary to obtain the best Ðt. Second, adopting a helium abundance from a standard metallicity-helium relation, we have estimated a required extent of core overshooting Our results l ov . indicate that the required extent of core overshooting is less than which is smaller than the D0.15H p , extent estimated by and his collaborators. The main reason for the di †erence is attributed to Schro der the fact that we have taken into account published estimates of metallicity for each system. We have found that to obtain a good Ðt with red components we have to modify the ratio of mixing length to pressure scale height for each system. The required ratio is found to be smaller for a metal-poor system and vice versa.

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“…The mass of the Cepheid can then be obtained by combining this amplitude with the orbital velocity amplitude of the Cepheid from groundbased observations and a mass inferred from the spectral type of the companion. A summary of these measured Cepheid masses provided by IUE and Hubble Space Telescope (HST ) spectroscopy is given in Evans et al (1998). Double-mode Cepheids have been particularly important in discussions of observed and theoretical masses.…”

Section: Introductionmentioning

confidence: 99%

High-Mass Triple Systems: The Classical Cepheid Y Carinae

et al. 2005

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We have obtained a Hubble Space Telescope STIS ultraviolet high-dispersion echelle-mode spectrum of the binary companion of the double-mode classical Cepheid Y Car. The velocity measured for the hot companion from this spectrum is very different from reasonable predictions for binary motion, implying that the companion is itself a short-period binary. The measured velocity changed by 7 km s À1 during the 4 days between two segments of the observation, confirming this interpretation. We summarize ''binary'' Cepheids that are in fact members of a triple system and find that at least 44% are triples. The summary of information on Cepheids with orbits makes it likely that the fraction is underestimated.

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Classical Cepheid Masses: U Aquilae

Cited by 23 publications

References 20 publications

Cepheid Masses:FUSEObservations of S Muscae

Cepheid Masses:FUSEObservations of S Muscae

A Comparison of Stellar Evolution with Binary Systems

High-Mass Triple Systems: The Classical Cepheid Y Carinae

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