Classification of Population II Stars in the Vilnius Photometric System. II. Results

Bartkevicius, A.; Lazauskaite, R.

doi:10.1515/astro-1997-0402

Cited by 5 publications

(9 citation statements)

References 10 publications

(32 reference statements)

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“…• 2079 the (Y − V ) 0 was taken from Bartkevičius & Lazauskaitė (1997) and the same procedure applied. In the work by Tautvaišienė (1996b) as well as in the work by Norris (1987) the interstellar reddening for these stars was accepted to be zero.…”

Section: Methods Of Analysismentioning

confidence: 99%

“…The effective temperatures for the programme stars were initially taken from Tautvaišienė (1996b), where they were derived using the intrinsic colour index (Y − V ) 0 of the Vilnius photometric system. For the star BD +28 • 2079 the (Y − V ) 0 was taken from Bartkevičius & Lazauskaitė (1997) and the same procedure applied. In the work by Tautvaišienė (1996b) as well as in the work by Norris (1987) the interstellar reddening for these stars was accepted to be zero.…”

Section: Methods Of Analysismentioning

confidence: 99%

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Chemical composition of red horizontal branch stars in the thick disk of the Galaxy

Tautvaišienė¹,

Edvardsson²,

Tuominen

et al. 2001

A&A

128

223

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Abstract. High-resolution spectra of 13 core helium-burning stars in the thick disk of the Galaxy have been obtained with the SOFIN spectrograph on the Nordic Optical Telescope to investigate abundances of up to 22 chemical elements. Abundances of carbon were studied using the C2 Swan (0, 1) band head at 5635.5Å. The wavelength interval 7980-8130Å with strong CN features was analysed in order to determine nitrogen abundances and 12 C/ 13 C isotope ratios. The oxygen abundances were determined from the [O i] line at 6300Å. Abundances in the investigated stars suggest that carbon is depleted by about 0.3 dex, nitrogen is enhanced by more than 0.4 dex and oxygen is unaltered. The 12 C/ 13 C ratios are lowered and lie between values 3 and 7 which is in agreement with "cool bottom processing" predictions (Boothroyd & Sackmann 1999). The C/N ratios in the investigated stars are lowered to values between 0.7 and 1.2 which is less than present day theoretical predictions and call for further studies of stellar mixing processes. Abundance ratios of O, Mg, Eu and other heavy chemical elements to iron in the investigated stars show a pattern characteristic of thick disk stars. The results provide evidence that the thick disk population has a distinct chemical history from the thin disk. The onset of the bulk of SN Ia is suggested to appear at [Fe/H] ≈ −0.6 dex.

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Section: Methods Of Analysismentioning

confidence: 99%

Section: Methods Of Analysismentioning

confidence: 99%

Chemical composition of red horizontal branch stars in the thick disk of the Galaxy

Tautvaišienė¹,

Edvardsson²,

Tuominen

et al. 2001

A&A

128

223

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“…It was noted by Bartkevicius & Lazauskaite (1997) that HX UMa is not physically related to the nearby variable star DP UMa (HD 104513).…”

Section: Hx Umamentioning

confidence: 99%

Radial Velocity Studies of Close Binary Stars. VIII.

Ruciński

Capobianco

et al. 2003

Astron J

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Radial-velocity measurements and sine-curve fits to the orbital velocity variations are presented for the seventh set of ten close binary systems: V410 Aur, V523 Cas, QW Gem, V921 Her, V2357 Oph, V1130 Tau, HN UMa, HX UMa, HD 93917, NSV 223. All systems, but three (V523 Cas, HD 93917, NSV 223), were discovered photometrically by the Hipparcos mission. All systems are double-lined (SB2) binaries and all, but the detached, very close system V1130 Tau, are contact binaries. The broadeningfunction permitted improvement of the orbital elements for V523 Cas, which was the only system observed before for radial velocity variations. Spectroscopic/visual companions were detected for V410 Aur and HX UMa. Several of the studied systems are prime candidates for combined light and radial-velocity synthesis solutions.

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“…The shell features in the spectrum may arise from mass transfer in this possible Algol system. BD-13 6465: This star has been variously classified in the literature as a high-latitude spectroscopically peculiar star (A2pec, Graham & Slettebak 1973), a subdwarf sdB5 (deduced from Vilnius photometry, Bartkevicius & Lazauskaite 1997), and a young runaway star (Tetzlaff et al 2011 . This, combined with B V 0.29 -= , is consistent with an F-type dwarf.…”

Section: Notes On Individual Stars In the Miscellaneous Samplementioning

confidence: 99%

The Discovery of λ Bootis Stars: The Southern Survey I

Gray¹,

Riggs²,

Koen³

et al. 2017

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The λ Boo stars are a class of chemically peculiar Population I A-type stars characterized by under-abundances of the refractory elements, but near-solar abundances of carbon, nitrogen, oxygen, and sulfur. There is some evidence that λ Boo stars have higher frequencies of “bright” debris disks than normal A-type stars. The discovery of four exoplanets orbiting HR 8799, a λ Boo star with a resolved debris disk, suggests that the λ Boo phenomenon may be related to the presence of a dynamic debris disk, perhaps perturbed by migrating planets. However, only 64 λ Boo stars are known, and those stars were discovered with different techniques, making it problematic to use that sample for statistical purposes, including determining the frequency of debris disks. The purpose of this paper is to derive a new sample of λ Boo stars using a technique that does not lead to biases with respect to the presence of infrared excesses. Through spectroscopic observations in the southern hemisphere, we have discovered 33 λ Boo stars and have confirmed 12 others. As a step toward determining the proportion of λ Boo stars with infrared excesses, we have used WISE data to examine the infrared properties of this sample out to 22 μm. On this basis, we cannot conclude that λ Boo stars have a greater tendency than normal A-type stars to show infrared excesses. However, observing this sample at longer wavelengths may change that conclusion, as many λ Boo debris disks are cool and do not radiate strongly at 22 μm.

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Classification of Population II Stars in the Vilnius Photometric System. II. Results

Cited by 5 publications

References 10 publications

Chemical composition of red horizontal branch stars in the thick disk of the Galaxy

Chemical composition of red horizontal branch stars in the thick disk of the Galaxy

Radial Velocity Studies of Close Binary Stars. VIII.

The Discovery of λ Bootis Stars: The Southern Survey I

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