Salmon and trout

Harris, William C.; Sage, Dean; Smith, Hugh M.; Townsend, C. H. T.

doi:10.5962/bhl.title.11808

Cited by 3 publications

(4 citation statements)

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“…This suggests that the age of the globular cluster derived in Hansen et al (2007) can be ∼0.5 Gyr too low because of the white dwarf atmosphere models that do not account for Ly-α red wing opacity. We also conducted the same simple analysis for the white dwarf cooling sequence observed in the Milky Way obtained from three samples of white dwarfs Kilic et al 2006;Harris et al 2006). To do this we used published color sequences of Kowalski & Saumon (2006).…”

Section: T Eff At the Edge Of The White Dwarf Cooling Sequence And Thmentioning

confidence: 99%

White dwarf atmosphere models with Ly-alpha opacity in the analysis of the white dwarf cooling sequence of NGC 6397

Kowalski

2007

A&A

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Aims. We discuss the importance of pure hydrogen white dwarf atmosphere models with Ly-α far red wing opacity in the analysis of the white dwarf cooling sequence of the globular cluster NGC 6397. Methods. Our recently improved atmosphere models account for the previously missing opacity from the Ly-α hydrogen line broadened by collisions of the absorbing hydrogen atoms with molecular and atomic hydrogen. These models are the first that well reproduce the UV colors and spectral energy distributions of cool white dwarfs with T eff < 6000 K observed in the Galactic Disk. Results. Fitting the observed F814W magnitude and F606W − F814W color we obtained a value for the true distance modulus, µ = 12.00 ± 0.02, that is in agreement with recent analyses. We show that the stars at the end of the cooling sequence appear to be ∼160 K cooler when models that account for Ly-α opacity are used. This indicates that the age of NGC 6397 derived from the white dwarf cooling sequence using atmosphere models that do not include the correct Ly-α opacity is underestimated by ∼0.5 Gyr. Conclusions. Our analysis shows that it is essential to use white dwarf atmosphere models with Ly-α opacity for precise dating of old stellar populations from white dwarf cooling sequences.

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Section: T Eff At the Edge Of The White Dwarf Cooling Sequence And Thmentioning

confidence: 99%

White dwarf atmosphere models with Ly-alpha opacity in the analysis of the white dwarf cooling sequence of NGC 6397

Kowalski

2007

A&A

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“…Existing evidence based upon the inferred metallicity of T Ant (Harris 1981), a Baade-Wesselink radius typical of a Population I star (Laney 1995), the regular nature of its light curve (Figs. 1 and 2), and its observed rate of period change are all consistent with a classical Cepheid belonging to Population I rather than a type II Cepheid.…”

Section: Contains Photoelectric Observations Sufficiently Distributedmentioning

confidence: 99%

“…It lies just above the Galactic plane along the Puppis-Vela-Carina portion of the southern Milky Way, outside of the region normally included in surveys of disk stars. The relative isolation of T Ant from major groups of early-type stars in nearby Vela and the Cepheid's uncertain catalogue designation as a classical, but possible type II, Cepheid (Harris 1981;Kholopov et al 1985) help to explain its relative neglect. As we demonstrate here, T Ant and a number of B-type stars in its immediate vicinity are important objects for future study because there is evidence to indicate that they form a sparse, previously undetected, open cluster in which T Ant is a likely member.…”

Section: Introductionmentioning

confidence: 99%

The nature of the Cepheid T Antliae

Turner

Бердников

2003

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Abstract. The variable star T Antliae, sometimes suspected to be a type II pulsator, is demonstrated to be a classical Cepheid in the third crossing of the instability strip. It exhibits a positive period change of +0.514 ± 0.016 s yr −1 , consistent with a star on the blue side of the instability strip and evolving through it for the third time. The Cepheid exhibits no random fluctuations in pulsation period, although superimposed upon its evolutionary O-C trend are very subtle variations that may be indicative of orbital motion about an unseen companion. Archival spectroscopic data also indicate that the star sits on the edge of a putative cluster of B-type stars that may be physically associated with the Cepheid. Additional photometric and spectroscopic data for the Cepheid and cluster are needed to strengthen the case. The field reddening of T Ant established from nearby early-type stars is E B−V = 0.30 ± 0.01 (E B−V (B0) = 0.316 ± 0.014).

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“…The latter stars in the short-period range are a heterogeneous group with metallicities ranging from very low to at least solar (Harris 1981), kinematics appropriate to a range of populations (Harris & Wallerstein 1984) and a variety of light curve shapes. Diethelm (1983) sorted the light curves into several categories and subsequently (Diethelm 1986) used photometric abundances to show that at least one of the groups, his RRd stars, was physically distinct.…”

Section: Introductionmentioning

confidence: 99%