Spectra and Colors of Early-Type Stars Near the North Galactic Pole.

Slettebak, Arne; Bahner, K.; Stock, J.

doi:10.1086/147139

Cited by 23 publications

(10 citation statements)

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“…Only 1 of the 4 (HD209961, HIP109082, B2V) spectroscopic binaries discussed by van Albada & Klomp (1969) is selected. Several other studies have put forward 'special' candidate members (e.g., Crawford 1961;Slettebak, Bahner & Stock 1961;Kodaira, Greenstein & Oke 1970;Levato & Abt 1976;Guetter 1976;Malaroda 1981;Garmany & Stencel 1992): we confirm membership of the emission-line star HD216851 (HIP113226, B3V:n), the shell star HD213801 (HIP111337, B9V), and the red supergiants HD213310 and HD216946 (HIP111022, M0II, and HIP113288, K5Ibvar, respectively). We do not confirm most candidate members with peculiar and/or magnetic spectra.…”

Section: Lacerta Ob1supporting

confidence: 69%

A [ITAL]Hipparcos[/ITAL] Census of the Nearby OB Associations

Zeeuw¹,

Hoogerwerf²,

Bruijne³

et al. 1999

The Astronomical Journal

1,205

118

1,616

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A comprehensive census of the stellar content of the OB associations within 1 kpc from the Sun is presented, based on Hipparcos positions, proper motions, and parallaxes. It is a key part of a long-term project to study the formation, structure, and evolution of nearby young stellar groups and related star-forming regions.OB associations are unbound 'moving groups', which can be detected kinematically because of their small internal velocity dispersion. The nearby associations have a large extent on the sky, which traditionally has limited astrometric membership determination to bright stars (V ∼ < 6 m ), with spectral types earlier than ∼B5. The Hipparcos measurements allow a major improvement in this situation. Moving groups are identified in the Hipparcos Catalogue by combining de Bruijne's refurbished convergent point method with the 'Spaghetti method' of Hoogerwerf & Aguilar. Astrometric members are listed for 12 young stellar groups, out to a distance of ∼650 pc. These are the 3 subgroups Upper Scorpius, Upper Centaurus Lupus and Lower Centaurus Crux of Sco OB2, as well as Vel OB2, Tr 10, Col 121, Per OB2, α Persei (Per OB3), Cas-Tau, Lac OB1, Cep OB2, and a new group in Cepheus, designated as Cep OB6. The selection procedure corrects the list of previously known astrometric and photometric B-and A-type members in these groups, and identifies many new members, including a significant number of F stars, as well as evolved stars, e.g., the Wolf-Rayet stars γ 2 Vel (WR11) in Vel OB2 and EZ CMa (WR6) in Col 121, and the classical Cepheid δ Cep in Cep OB6. Membership probabilities are given for all selected stars. Monte Carlo simulations are used to estimate the expected number of interloper field stars. In the nearest associations, notably in Sco OB2, the later-type members include T Tauri objects and other stars in the final pre-main sequence phase. This provides a firm link between the classical high-mass stellar content and ongoing low-mass star formation. Detailed studies of these 12 groups, and their relation to the surrounding interstellar medium, will be presented elsewhere.Astrometric evidence for moving groups in the fields of R CrA, CMa OB1, Mon OB1, Ori OB1, Cam OB1, Cep OB3, Cep OB4, Cyg OB4, Cyg OB7, and Sct OB2, is inconclusive. OB associations do exist in many of these regions, but they are either at distances beyond ∼500 pc where the Hipparcos parallaxes are of limited use, or they have unfavorable kinematics, so that the group proper motion does not distinguish it from the field stars in the Galactic disk.The mean distances of the well-established groups are systematically smaller than the pre-Hipparcos photometric estimates. While part of this may be caused by the improved membership lists, a recalibration of the upper main sequence in the Hertzsprung-Russell diagram may be called for. The mean motions display a systematic pattern, which is discussed in relation to the Gould Belt.Six of the 12 detected moving groups do not appear in the classical list of nearby OB associations. This is sometim...

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Section: Lacerta Ob1supporting

confidence: 69%

A [ITAL]Hipparcos[/ITAL] Census of the Nearby OB Associations

Zeeuw¹,

Hoogerwerf²,

Bruijne³

et al. 1999

The Astronomical Journal

1,205

118

1,616

View full text Add to dashboard Cite

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“…Künzli & North (1998) found it to be an evolved metallic‐line star and detected some light variations. HD 109762 . Two references for its Am nature are quoted in Hauck's (1986) catalogue: Slettebak, Bahner & Stock (1961) and Slettebak, Wright & Graham (1968). Hill et al (1976) confirmed its classification as Am and first noted the variability in its RV.…”

Section: Notes On Individual Systemsmentioning

confidence: 99%

Contribution to the search for binaries among Am stars – VIII. New spectroscopic orbits of eight systems and statistical study of a sample of 91 Am stars

Carquillat

Prieur

2007

Monthly Notices of the Royal Astronomical Society

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International audienceThis paper is the last of a series devoted to the study of Am stars, with the monitoring of radial velocities of a sample of 91 objects during more than 20 yr. The purpose was to determine which stars were members of spectroscopic binaries (SBs) and study in detail those systems in order to obtain observational constraints on the origin of the Am phenomenon. In the first part, we present the results of a detailed study of eight Am stars (HD 32893, 60489, 109762, 111057, 113697, 204918, 219675 and BD+44° 4512) observed at the Haute-Provence and Cambridge observatories with CORAVEL instruments. We find that these objects are single-lined SBs whose orbital elements are determined for the first time. HD 32893 is found to be a triple spectroscopic system whose third body might be detected by speckle interferometry. Physical parameters are inferred for the primaries of those SBs. We then investigate the influence of tidal interaction and find that it has already led to the synchronism of the primaries and to the circularization of the orbits of four of those systems. In the second part of this paper, we present the main results of our whole programme and derive some statistical properties of Am stars. We give the recapitulating table of the orbital parameters found for the SBs of our whole sample and the list of those for which no evidence for radial velocity variations could be found during our monitoring. Our study shows that at least 64 per cent of Am stars are members of SBs. This rate is significantly greater than that of normal stars. Although some SBs may have been not detected, this study shows that a substantial fraction of Am stars do not belong to SBs: they are either isolated stars or members of wide binary systems. We then present some statistical properties of the orbital parameters of the SBs whose primary is an Am star, on an extended sample obtained by adding 29 Am SB orbits published by other authors. The corresponding e versus logP diagram shows a cut-off between the circular and the eccentric systems at P ~ 5.6 +/- 0.5 d, which indicates a typical age of 0.5 - 1 × 109 yr for the Am stars, which is in agreement with the values found in our previous detailed studies. A Monte Carlo analysis shows that the distribution of the mass function values f(m) is compatible with a power-law distribution N(m) ~ m-? of the masses m of the companions with ? = 0.3 +/- 0.2 or with a Gaussian distribution centred on 0.8 +/- 0.5Msolar, which indicates that the companions of Am SBs are mostly dwarf stars of type G-K-M

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“…Two examples are BD+39°4926 (Slettebak et al 1961) and HD46703 (Bond 1970;Luck & Bond 1984). Both are longperiod spectroscopic binaries, with orbital periods of 775days for BD+39°4926 (Kodaira et al 1970) and 600days for HD46703 (Hrivnak et al 2008).…”

Section: Introductionmentioning

confidence: 99%

A Luminous Yellow Post-Agb Star in the Galactic Globular Cluster M79*

Bond

Ciardullo

Siegel

2016

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We report the discovery of a luminous F-type post-asymptotic-giant-branch (PAGB) star in the Galactic globular cluster (GC) M79 (NGC1904). At visual apparent and absolute magnitudes of V 12.20 = and M 3.46 V = -, this "yellow" PAGB star is by a small margin the visually brightest star known in any GC. It was identified using CCD observations in the uBVI photometric system, which is optimized to detect stars with large Balmer discontinuities, indicative of very low surface gravities. Follow-up observations with the SMARTS 1.3 and 1.5 m telescopes show that the star is not variable in light or radial velocity, and that its velocity is consistent with cluster membership. Near-and mid-infrared observations with 2MASS and WISE show no evidence for circumstellar dust. We argue that a sharp upper limit to the luminosity function exists for yellow PAGB stars in old populations, making them excellent candidates for PopulationII standard candles, which are four magnitudes brighter than RRLyrae variables. Their luminosities are consistent with the stars being in a PAGB evolutionary phase, with core masses of M 0.53  . We also detected four very hot stars lying above the horizontal branch ("AGB-manqué" stars); along with the PAGB star, they are the brightest objects in M79 in the near-ultraviolet. In the Appendix, we give periods and light curves for five variables in M79: three RRLyrae stars, a TypeII Cepheid, and a semiregular variable.

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Spectra and Colors of Early-Type Stars Near the North Galactic Pole.

Cited by 23 publications

References 0 publications

A [ITAL]Hipparcos[/ITAL] Census of the Nearby OB Associations

A [ITAL]Hipparcos[/ITAL] Census of the Nearby OB Associations

Contribution to the search for binaries among Am stars – VIII. New spectroscopic orbits of eight systems and statistical study of a sample of 91 Am stars

A Luminous Yellow Post-Agb Star in the Galactic Globular Cluster M79*

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