The Sirius Supercluster and Missing Mass near the Sun

Eggen, O. J.

doi:10.1086/300465

Cited by 14 publications

(13 citation statements)

References 32 publications

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“…Chereul, Crézé, & Bienaymé 1999). While this may be evidence for a diversity of formation epochs with an age spread of ∼ 8 × 10 8 yr as advocated by Eggen & Iben (1988), it is also with reference to Hipparcos that Eggen (1998) revises this to a single 4 × 10 8 yr isochrone, rejecting rather spurious objects such as α Oph (τ ∼ 1 Gyr? ).…”

Section: Young Stars Of the Ursa Major Associationmentioning

confidence: 81%

“…Eggen 1992Eggen , 1998). For our sample it is also important to know that a good deal of the early-type stars are actually members of the Ursa Major Association.…”

Section: Young Stars Of the Ursa Major Associationmentioning

confidence: 99%

“…This is particularly true, since there appears to be a spurious entry in the Hipparcos catalog for HR 4867's proper motion in declination, as pointed out by Eggen (1998) and Chupina, Reva, & Vereshchagin (2001).…”

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confidence: 99%

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Nearby stars of the Galactic disk and halo. III.

2003

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Abstract. High-resolution spectroscopic observations of about 150 nearby stars or star systems are presented and discussed. The study of these and another 100 objects of the previous papers of this series implies that the Galaxy became reality 13 or 14 Gyr ago with the implementation of a massive, rotationally-supported population of thick-disk stars. The very high star formation rate in that phase gave rise to a rapid metal enrichment and an expulsion of gas in supernovae-driven Galactic winds, but was followed by a star formation gap for no less than three billion years at the Sun's galactocentric distance. In a second phase, then, the thin disk -our "familiar Milky Way" -came on stage. Nowadays it traces the bright side of the Galaxy, but it is also embedded in a huge coffin of dead thick-disk stars that account for a large amount of baryonic dark matter. As opposed to this, cold-dark-matter-dominated cosmologies that suggest a more gradual hierarchical buildup through mergers of minor structures, though popular, are a poor description for the Milky Way Galaxy -and by inference many other spirals as well -if, as the sample implies, the fossil records of its long-lived stars do not stick to this paradigm. Apart from this general picture that emerges with reference to the entire sample stars, a good deal of the present work is however also concerned with detailed discussions of many individual objects. Among the most interesting we mention the blue straggler or merger candidates HD 165401 and HD 137763/HD 137778, the likely accretion of a giant planet or brown dwarf on 59 Vir in its recent history, and HD 63433 that proves to be a young solar analog at τ ∼ 200 Myr. Likewise, the secondary to HR 4867, formerly suspected non-single from the Hipparcos astrometry, is directly detectable in the highresolution spectroscopic tracings, whereas the visual binary χ Cet is instead at least triple, and presumably even quadruple. With respect to the nearby young stars a complete account of the Ursa Major Association is presented, and we provide as well plain evidence for another, the "Hercules-Lyra Association", the likely existence of which was only realized in recent years. On account of its rotation, chemistry, and age we do confirm that the Sun is very typical among its G-type neighbors; as to its kinematics, it appears however not unlikely that the Sun's known low peculiar space velocity could indeed be the cause for the weak paleontological record of mass extinctions and major impact events on our parent planet during the most recent Galactic plane passage of the solar system. Although the significance of this correlation certainly remains a matter of debate for years to come, we point in this context to the principal importance of the thick disk for a complete census with respect to the local surface and volume densities. Other important effects that can be ascribed to this dark stellar population comprise (i) the observed plateau in the shape of the luminosity function of the local FGK stars, (ii) a small though syst...

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Section: Young Stars Of the Ursa Major Associationmentioning

confidence: 81%

“…Eggen 1992Eggen , 1998). For our sample it is also important to know that a good deal of the early-type stars are actually members of the Ursa Major Association.…”

Section: Young Stars Of the Ursa Major Associationmentioning

confidence: 99%

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Nearby stars of the Galactic disk and halo. III.

2003

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“…In fact, the APOGEE instrument and the existing radial velocity software routinely deliver radial velocities at a precision of ∼0.07 km s −1 for S/N>20, while the survey provides external calibration sufficient to ensure accuracies at the level of ∼0.35 km s −1 (Nidever et al 2015; Section 7.3)-a level of performance that allows more subtle dynamical effects to be measured. For example, the detection of pattern speeds of-or kinematical substructure in the disk due to perturbations and resonances from-spiral arms, the bar, or other (e.g., dark matter) substructure (e.g., Dehnen 1998;Famaey et al 2005;Junqueira et al 2015), the detection of stellar binary companions (e.g., Terrien et al 2014), the assessment of stellar membership in star clusters (e.g., Terrien et al 2014;Carlberg et al 2015) or extended stellar kinematic groups (i.e., "moving groups" or "superclusters") in the disk (e.g., Eggen 1958Eggen , 1998Montes et al 2001;Malo et al 2013), and the accurate measurement of stellar velocity dispersions in star clusters or satellite galaxies (Majewski et al 2013) are all made possible with radial velocity measurements of the rms precision and external accuracies routinely achieved by APOGEE for main survey program stars. Nevertheless, it has been shown that even greater precision and accuracy may be obtained from APOGEE spectra, which increases the sensitivity to even lower mass stellar companions (Deshpande et al 2013) and greatly benefits the exploration of the intricate dynamics of young star clusters (Cottaar et al 2014;Foster et al 2015).…”

Section: Kinematical Precisionmentioning

confidence: 99%

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

et al. 2017

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The Apache Point Observatory Galactic Evolution Experiment (APOGEE), one of the programs in the Sloan Digital Sky Survey III (SDSS-III), has now completed its systematic, homogeneous spectroscopic survey sampling all major populations of the Milky Way. After a three-year observing campaign on the Sloan 2.5 m Telescope, APOGEE has collected a half million high-resolution (R ∼ 22,500), high signal-to-noise ratio (>100), infrared (1.51–1.70 μm) spectra for 146,000 stars, with time series information via repeat visits to most of these stars. This paper describes the motivations for the survey and its overall design—hardware, field placement, target selection, operations—and gives an overview of these aspects as well as the data reduction, analysis, and products. An index is also given to the complement of technical papers that describe various critical survey components in detail. Finally, we discuss the achieved survey performance and illustrate the variety of potential uses of the data products by way of a number of science demonstrations, which span from time series analysis of stellar spectral variations and radial velocity variations from stellar companions, to spatial maps of kinematics, metallicity, and abundance patterns across the Galaxy and as a function of age, to new views of the interstellar medium, the chemistry of star clusters, and the discovery of rare stellar species. As part of SDSS-III Data Release 12 and later releases, all of the APOGEE data products are publicly available.

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“…It contains socalled probable members (the nucleus stars and some others selected both by spectral index and by kinematics) and possible members for which the kinematic data is located within a 3σ error ellipsoid. - Eggen (1998 , Table 1), n = 17. Montes et al (2001).…”

Section: Observational Datamentioning

confidence: 99%

Kinematic structure of the corona of the Ursa Major flow found using proper motions and radial velocities of single stars

Чупина¹,

Reva²,

Верещагин³

2006

A&A

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Aims. We study the kinematic structure of peripheral areas of the Ursa Majoris stream (Sirius supercluster). Methods. We use diagrams of individual stellar apexes developed by us and the classical technique of proper motion diagrams generalized to a star sample distributed over the sky. Results. Out of 128 cluster members we have identified three corona (sub)structures comprised of 13, 13 and 8 stars. The substructures have a spatial extension comparable to the size of the corona. Kinematically, these groups are distinguished by their proper motions, radial velocities and by the directions of their spatial motion. Coordinates of their apexes significantly differ from those of the apexes of the stream and its nucleus. Our analysis shows that these substructures do not belong to known kinematic groups, such as Hyades or Castor. We find kinematic inhomogeneity of the corona of the UMa stream.

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The Sirius Supercluster and Missing Mass near the Sun

Cited by 14 publications

References 32 publications

Nearby stars of the Galactic disk and halo. III.

Nearby stars of the Galactic disk and halo. III.

The Apache Point Observatory Galactic Evolution Experiment (APOGEE)

Kinematic structure of the corona of the Ursa Major flow found using proper motions and radial velocities of single stars

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