The Open Cluster Ruprecht 91 and Its Cepheids

Turner, D. G.; Forbes, Douglas; Bergh, Sidney van den; Younger, P. F.; Бердников, Л. Н.

doi:10.1086/432574

Cited by 14 publications

(24 citation statements)

References 37 publications

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“…Fernie et al (1966) reported a chance alignment with an OB association (see also Turner et al 2012), which the HST spatial scans will further illuminate. Madore & Fernie (1980) presented evidence of a photometric companion based on both a phase-shift and color-loop methodology.…”

Section: Wz Sgrmentioning

confidence: 80%

“…AQ Puppis exhibits very significant non-linear changes of P puls (Vinko 1991) in addition to exceptionally fast (300 s yr −1 ) secular changes of P puls that approach values predicted for Cepheids on a first crossing of the instability strip (Turner et al 2012;Anderson et al 2016a). Fernie et al (1966) reported a chance alignment with an OB association (see also Turner et al 2012), which the HST spatial scans will further illuminate.…”

Section: Wz Sgrmentioning

confidence: 85%

“…Rather, it appears more likely that non-linear changes of P puls (see e.g. Turner et al 2012, Fig. 10) lead to problems in phase-folding the data, which is required to determine v γ .…”

Section: Wz Sgrmentioning

confidence: 99%

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Vetting Galactic Leavitt Law Calibrators Using Radial Velocities: On the Variability, Binarity, and Possible Parallax Error of 19 Long-Period Cepheids

Anderson

Casertano

Riess

et al. 2016

ApJS

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We investigate the radial velocity (RV) variability and spectroscopic binarity of 19 Galactic long-period (P puls 10 d) classical Cepheid variable stars whose trigonometric parallaxes are being measured using the Hubble Space Telescope and Gaia. Our primary objective is to constrain possible parallax error due to undetected orbital motion. Using > 1600 high-precision RVs measured between 2011 and 2016, we find no indication of orbital motion on 5 yr timescales for 18 Cepheids and determine upper limits on allowed configurations for a range of input orbital periods. The results constrain the unsigned parallax error due to orbital motion to < 2 % for 16 stars, and < 4 % for 18. We improve the orbital solution of the known binary YZ Carinae and show that the astrometric model must take into account orbital motion to avoid significant error (∼ ±100 µarcsec). We further investigate longtimescale (P orb > 10 yr) variations in pulsation-averaged velocity v γ via a template fitting approach using both new and literature RVs. We discover the spectroscopic binarity of XZ Car and CD Cyg, find first tentative evidence for AQ Car, and reveal KN Cen's orbital signature. Further (mostly tentative) evidence of time-variable v γ is found for SS CMa, VY Car, SZ Cyg, and X Pup. We briefly discuss considerations regarding a vetting process of Galactic Leavitt law calibrators and show that light contributions by companions are insignificant for most distance scale applications.

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Section: Wz Sgrmentioning

confidence: 80%

Section: Wz Sgrmentioning

confidence: 85%

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Vetting Galactic Leavitt Law Calibrators Using Radial Velocities: On the Variability, Binarity, and Possible Parallax Error of 19 Long-Period Cepheids

Anderson

Casertano

Riess

et al. 2016

ApJS

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“…5, a situation typical of stars in crowded fields or stars near the limits of reliable photometry with the detector. Yet it is noteworthy that there are also many stars that closely match the intrinsic relation for unreddened dwarfs, which is often a good test of how closely the observations match the Johnson UBV system (see Turner et al 2012b). …”

Section: Photometric Analysismentioning

confidence: 94%

“…9) dereddened individually to the intrinsic color-color relation (see Turner 1996;Turner et al 2012b) is that of an extremely young cluster. Very few hot O-type members are evolved by more than 1 m from the ZAMS, except for the two Wolf-Rayet stars WR 20a and WR 20b, which are akin to O-type supergiants, WR 20a having a suspected O-supergiant companion (RomanLopes et al 2011).…”

Section: Westerlundmentioning

confidence: 99%

The distance to the young open cluster Westerlund 2

Carraro

Turner

Majaess

et al. 2013

A&A

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A new X-ray, UBVRI c , and JHKs study of the young cluster Westerlund 2 was undertaken to resolve discrepancies tied to the cluster's distance. Existing spectroscopic observations for bright cluster members and new multi-band photometry imply a reddening relation toward Westerlund 2 described by E U−B /E B−V = 0.63 + 0.02 E B−V . Variable-extinction analyses for Westerlund 2 and nearby IC 2581 based upon spectroscopic distance moduli and ZAMS fitting yield values of R V = A V /E B−V = 3.88±0.18 and 3.77±0.19, respectively, and confirm prior assertions that anomalous interstellar extinction is widespread throughout Carina. The results were confirmed by applying the color-difference method to UBVRI c JHK s data for 19 spectroscopically observed cluster members, yielding R V = 3.85 ± 0.07. The derived distance to Westerlund 2 of d = 2.85 ± 0.43 kpc places the cluster on the far side of the Carina spiral arm. The cluster's age is no more than τ ∼ 2 × 10 6 yr as inferred from the cluster's brightest stars and an X-ray (Chandra) cleaned analysis of its pre-main-sequence demographic. Four Wolf-Rayet stars in the cluster core and surrounding corona (WR20a, WR20b, WR20c, and WR20aa) are very likely cluster members, and their inferred luminosities are consistent with those of other late-WN stars in open clusters. The color-magnitude diagram for Westerlund 2 also displays a gap at spectral type B0.5 V with associated color spread at higher and lower absolute magnitudes that might be linked to close binary mergers. These features, in conjunction with the evidence for mass loss from the WR stars, may help to explain the high flux of γ-rays, cosmic rays, and X-rays from the direction toward Westerlund 2.

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WR 38/38a and the ratio of total-to-selective extinction in Carina

Turner

2011

Astrophys Space Sci

Self Cite

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A reanalysis of the (seemingly very distant) open cluster Shorlin 1, the group of stars associated with WR 38 and WR 38a, is made on the basis of existing UBV and JHK s observations for cluster members. The 2MASS observations, in particular, imply a mean cluster reddening of E B−V = 1.45 ± 0.07 and a distance of 2.94 ± 0.12 kpc. The reddening agrees with the UBV results provided that the local reddening slope is described by E U−B /E B−V = 0.64 ± 0.01, but the distance estimates in the 2MASS and UBV systems agree only if the ratio of total-to-selective extinction for the associated dust is R = A V /E B−V = 4.0 ± 0.1. Both results are similar to what has been obtained for adjacent clusters in the Eta Carinae region by similar analyses, which suggests that"anomalous" dust extinction is widespread through the region, particularly for groups reddened by relatively nearby dust. Dust associated with the Eta Carinae complex itself appears to exhibit more "normal" qualities. The results have direct implications for the interpretation of distances to optical spiral arm indicators for the Galaxy at ℓ = 287 • − 291 • , in particular the Carina arm here is probably little more than ∼ 2 kpc distant, rather than 2.5 − 3 kpc distant as implied in previous studies. Newly-derived intrinsic parameters for the two cluster Wolf-Rayet stars WR 38 (WC4) and WR 38a (WN5) are in good agreement with what is found for other WR stars in Galactic open clusters, which was not the case previously.

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The Open Cluster Ruprecht 91 and Its Cepheids

Cited by 14 publications

References 37 publications

Vetting Galactic Leavitt Law Calibrators Using Radial Velocities: On the Variability, Binarity, and Possible Parallax Error of 19 Long-Period Cepheids

Vetting Galactic Leavitt Law Calibrators Using Radial Velocities: On the Variability, Binarity, and Possible Parallax Error of 19 Long-Period Cepheids

The distance to the young open cluster Westerlund 2

WR 38/38a and the ratio of total-to-selective extinction in Carina

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