The Spectroscopic Absolute Magnitudes and Parallaxes of 4179 Stars

Adams, W. S.; Joy, A. H.; Humason, M. L.; Brayton, Ada Margaret

doi:10.1086/143628

Cited by 78 publications

(42 citation statements)

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“…The M67 subgiant sequence also ties onto the rising brighter giant branch that resembles (although less steep) the giant sequence of the globular clusters that had already been discovered by Shapley (1915) in his second cluster paper. In addition, and nevertheless, the stars in M67 were later found 3 "Giants" in the terminology from the 1910s in Hertzsprung and Russell's original diagrams, and continuing into the 1960s, were the stars in the H-R diagrams (such as that of Adams et al 1935) near with spectral types M p 0 V from G0 to early M; they defined a "giant sequence." The four Hyades giants were the local prototypes.…”

Section: The Importance Of the Open Cluster M67mentioning

confidence: 99%

The Age of the Oldest Stars in the Local Galactic Disk fromHipparcosParallaxes of G and K Subgiants

Sandage

Lubin

VandenBerg

2003

PUBL ASTRON SOC PAC

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ABSTRACT. We review the history of the discovery of field subgiant stars, the role that they played in the development of the early understanding of stellar evolution, and their importance in the age dating of the Galactic disk. We use the cataloged data from the Hipparcos satellite in this latter capacity.Based on Hipparcos parallaxes with relative accuracies of , the absolute magnitude of the lower , as well as to the envelope of the reddest main-sequence stars at . The rededge of the densest part of the distribution of field giants is, however, most readily matched by isochrones having [Fe/H . Such high metal abundances are evidently confirmed by the spectroscopically observed high ] ≈ ϩ0.23 metallicity (between [Fe/H and ϩ0.4) of the old thick-disk Galactic cluster NGC 6791, whose color-] p ϩ0.2 magnitude diagram can be made to fit either of these red boundaries by adopting suitable values for the reddening and distance modulus (from within the observed ranges of uncertainties of these quantities).The age of the field stars in the solar neighborhood is found to be Gyr (or Gyr if the stellar 7.9 ‫ע‬ 0.7 7.4 ‫ע‬ 0.7 models allow for the effects of diffusive processes) by fitting the theoretical isochrones for [Fe/H to the ] p ϩ0.37 lower envelope of the Hipparcos subgiants. However, this age is a function of metallicity. The models show a dependence of at for metallicities between 0.00 and ϩ0.37. The same grid dt p Ϫ3.99([Fe/H] Ϫ 0.37) M ∼ ϩ4 V of isochrones yields ages, in turn, of , , and 7.5 to 10 Gyr (depending on the assumed reddening) 4.0 ‫ע‬ 0.2 6.2 ‫ע‬ 0.5 for the old Galactic clusters M67, NGC 188, and NGC 6791 using metal abundances, distance moduli, and reddenings adopted in the text. Although the distance (and hence age) of NGC 6791 is somewhat uncertain, the ages of both the Galactic disk in the solar neighborhood and of NGC 6791 are, nevertheless, likely between 3 and 5 Gyr younger than the oldest halo globular clusters, which have ages of ∼13.5 Gyr. The conclusion is the same as that reached earlier by Liu & Chaboyer, who used Hipparcos parallax stars that were mainly near the main-sequence turnoff rather than at the lower bound of the subgiant luminosity that we determine here. The most significant results are (1) the supermetallicity of the oldest local disk stars and (2) the large age difference between the most metal poor component of the halo and the thick and thin disk in the solar neighborhood, confirming Liu & Chaboyer. These facts are undoubtedly related and pose again the problem of the proper scenario for the timing of events in the formation of the halo and the Galactic disk in the solar neighborhood.1 Part review of the history of the discovery of subgiants and part new results from Hipparcos.

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Section: The Importance Of the Open Cluster M67mentioning

confidence: 99%

The Age of the Oldest Stars in the Local Galactic Disk fromHipparcosParallaxes of G and K Subgiants

Sandage

Lubin

VandenBerg

2003

PUBL ASTRON SOC PAC

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“…The modern (Harvard) classification dates from the end of the nineteenth century (Pickering 1890) and was later reordered as it was realized that it reflected surface temperature (Cannon and Pickering 1918-24). The existence of a second parameter related to luminosity was shown by Hertzsprung (1909) and Adams and Köhlschütter (1914), leading eventually to the two-dimensional Mount Wilson system (Adams et al 1935). The H-R diagram had arrived with Hertzsprung (1911) and Russell (1914).…”

Section: Epilogue: Agn Studies Compared To Stellar Studiesmentioning

confidence: 99%

Classification of active galaxies and the prospect of a unified phenomenology

Lawrence

1987

PASP

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The observational classification of active galaxies is reviewed and its likely meaning discussed. A large number of facts and ideas are examined, but a particular set of ideas is stressed as our best hope for a unified phenomenology, as follows. There is only one kind of Active Galactic Nucleus (AGN). The observed variety arises from three degrees of freedom: (1) Dust opacity, which produces the distinction between Type 1 and Type 2 AGN. (2) Viewing angle of a relativistic jet, which produces the distinction between blazars and Type 1 AGN. (3) Duty cycle of activity (i.e., fraction of time spent "on") which produces the distinction between radio-loud and radio-quiet AGN. The duty cycle may be related to the mass of the spheroidal component of the parent galaxy. A fourth degree of freedom is, of course, the overall luminosity. Also, it has recently become clear that there is considerable latitude in the physical condition of gas surrounding the nucleus.For theories of AGN to be presented with a real challenge, we need two things. First, a clear qualitative phenomenology, such as the possibility outlined above, must be decided upon. Second, we need to formulate a quantitative phenomenology.

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“…The unusual strength of the lines of SrII in the spectrum of HD 137949 has been noted by Adams et al (1935). Babcock (1958a) also noted the unusual intensity of the EuII lines and found evidence of a rather strong magnetic field (≈ 1 kgauss).…”

Section: Hd 126515 = Gc 19462 = Ff Virmentioning

confidence: 72%