NEW EVIDENCE SUPPORTING CLUSTER MEMBERSHIP FOR THE KEYSTONE CALIBRATOR DELTA CEPHEI

Journal Article · Sat Mar 10 04:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/747/2/145· OSTI ID:22016210

Majaess, D; Turner, D ^[1]; Gieren, W ^[2]

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1. Department of Astronomy and Physics, Saint Mary's University, Halifax, NS (Canada)
2. Departamento de Astronomia, Universidad de Concepcion, Concepcion (Chile)

New and existing UBVJHK{sub s} , spectroscopic, NOMAD, Hubble Space Telescope, and revised Hipparcos observations are employed to determine properties for {delta} Cep and its host star cluster. The multi-faceted approach ensured that uncertainties were mitigated ({sigma}/d {approx} 2%). The following fundamental parameters were inferred for {delta} Cep: E(B - V) = 0.073 {+-} 0.018({sigma}), log {tau} = 7.9 {+-} 0.1, and d=272 {+-} 3({sigma}{sub x}-bar) {+-} 5 ({sigma}) pc. The cluster exhibits a turnoff near B6 (M{sub *}/M{sub Sun} {approx} 5), and the brightest host cluster members are the supergiants {zeta} Cep (K1.5Ib) and {delta} Cep. To within the uncertainties, the two stars share common astrometric parameters ({pi}, {mu}{sub {alpha}}, {mu}{sub {delta}}, RV {approx} -17 km s{sup -1}) and are tied to bluer members via the evolutionary track implied by the cluster's UBVJHK{sub s} color-color and color-magnitude diagrams. The cluster's existence is bolstered by the absence of an early-type sequence in color-magnitude diagrams for comparison fields. NOMAD data provided a means to identify potential cluster members (n {approx} 30) and double the existing sample. That number could increase with forthcoming precise proper motions (DASCH) for fainter main-sequence stars associated with classical Cepheids (e.g., {delta} Cep), which may invariably foster efforts to strengthen the Galactic Cepheid calibration and reduce uncertainties tied to H{sub 0}.

• OSTI ID: 22016210
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 747; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CALIBRATION
CEPHEIDS
COLOR
MAIN SEQUENCE STARS
PROPER MOTION
STAR CLUSTERS
TELESCOPES