A survey of galaxy redshifts. I - Data reduction techniques

Tonry, J.; Davis, Marc

doi:10.1086/112569

Cited by 1,422 publications

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“…The resulting correction was deemed satisfactory. The radial velocities (RVs) of the observed stars were measured with a cross-correlation (CC) technique (Tonry & Davis 1979) by means of the fxcor IRAF task. Radial velocity standards acquired with the same instrument were used as templates for the CC.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Lithium-rich giants in the Galactic thick disk

Monaco

Villanova

Bidin

et al. 2011

A&A

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Context. Lithium is a fragile element, which is easily destroyed in the stellar interior. The existence of lithium-rich giants still represents a challenge for stellar evolution models. Aims. We have collected a large database of high-resolution stellar spectra of 824 candidate thick-disk giants having 2 MASS photometry and proper motions measured by the Southern Proper-Motion Program (SPM). In order to investigate the nature of Li-rich giants, we searched this database for giants presenting a strong Li I resonance line. Methods. We performed a chemical abundance analysis on the selected stars with the MOOG code along with proper ATLAS-9 model atmospheres. The iron content and atmospheric parameters were fixed by using the equivalent width of a sample of Fe lines. We also derive abundances for C, N, and O and measure or derive lower limits on the 12 C/ 13 C isotopic ratios, which is a sensible diagnostic of the stars evolutionary status. Results. We detected five stars with a lithium abundance higher than 1.5, i.e. Li-rich according to the current definition. One of them (SPM-313132) has A(Li) > 3.3 and, because of this, belongs to the group of the rare super Li-rich giants. Its kinematics makes it a likely thin-disk member and its atmospheric parameters are compatible with it being a 4 M star either on the red giant branch (RGB) or the early asymptotic giant branch. This object is the first super Li-rich giant detected at this phase. The other four are likely low-mass thick-disk stars evolved past the RGB luminosity bump, as determined from their metallicities and atmospheric parameters. The most evolved of them lies close to the RGB-tip. It has A(Li) > 2.7 and a low 12 C/ 13 C isotopic ratio, close to the cool bottom processing predictions.

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Section: Observations and Data Reductionmentioning

confidence: 99%

Lithium-rich giants in the Galactic thick disk

Monaco

Villanova

Bidin

et al. 2011

A&A

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“…RVs were measured by Fourier cross-correlation (Tonry & Davis 1979), using the IRAF 1 task FXCOR. In brief, all the spectra were cross-correlated with one template spectrum chosen among the stars belonging to the observed sample (stars S07 and S56 for σ Ori and L04 and L17 for λ Ori).…”

Section: Radial Velocitiesmentioning

confidence: 99%

FLAMES spectroscopy of low-mass stars in the young clusters σ Ori and λ Ori

Sacco

Franciosini²,

Randich

et al. 2008

A&A

181

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Aims. We performed a detailed membership selection and studied the accretion properties of low-mass stars in the two apparently very similar young (1-10 Myr) clusters σ Ori and λ Ori. Methods. We observed 98 and 49 low-mass (0.2-1.0 M ) stars in σ Ori and λ Ori respectively, using the multi-object optical spectrograph FLAMES at the VLT, with the high-resolution (R ∼ 17 000) HR15N grating (6470-6790 Å). We used radial velocities, Li and Hα to establish cluster membership and Hα and other optical emission lines to analyze the accretion properties of members. Results. We identified 65 and 45 members of the σ Ori and λ Ori clusters, respectively, and discovered 16 new candidate binary systems. We also measured rotational broadening for 20 stars and estimated the mass accretion rates in 25 stars of the σ Ori cluster, finding values between 10 −11 and 10 −7.7 M yr −1 and in 4 stars of the λ Ori cluster, finding values between 10 −11 and 10 −10.1 M yr −1 . Comparing our results with the infrared photometry obtained by the Spitzer satellite, we find that the fraction of stars with disks and the fraction of active disks is larger in the σ Ori cluster (52 ± 9% and 78 ± 16%) than in λ Ori (28 ± 8% and 40 ± 20%). Conclusions. The different disk and accretion properties of the two clusters could be due either to the effect of the high-mass stars and the supernova explosion in the λ Ori cluster or to different ages of the cluster populations. Further observations are required to draw a definitive conclusion.

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“…Velocity errors are measured from the full-width-athalf-maximum of the cross-correlation peak using the rstatistic (Tonry & Davis 1979). Empirical validation us- Table 1.…”

Section: Radial Velocities and Errorsmentioning

confidence: 99%

A Gemini snapshot survey for double degenerates

Kilic

Brown

Gianninas

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the results from a Gemini snapshot radial-velocity survey of 44 lowmass white dwarf candidates selected from the Sloan Digital Sky Survey spectroscopy. To find sub-hour orbital period binary systems, our time-series spectroscopy had cadences of 2 to 8 min over a period of 20-30 min. Through follow-up observations at Gemini and the MMT, we identify four double degenerate binary systems with periods ranging from 53 min to 7 h. The shortest period system, SDSS J123549.88+154319.3, was recently identified as a subhour period detached binary by Breedt and collaborators. Here we refine the orbital and physical parameters of this system. High-speed and time domain survey photometry observations do not reveal eclipses or other photometric effects in any of our targets. We compare the period distribution of these four systems with the orbital period distribution of known double white dwarfs; the median period decreases from 0.64 to 0.24 d for M = 0.3 − 0.5M ⊙ to M < 0.3M ⊙ white dwarfs. However, we do not find a statistically significant correlation between the orbital period and white dwarf mass.

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A survey of galaxy redshifts. I - Data reduction techniques

Cited by 1,422 publications

References 0 publications

Lithium-rich giants in the Galactic thick disk

Lithium-rich giants in the Galactic thick disk

FLAMES spectroscopy of low-mass stars in the young clusters σ Ori and λ Ori

A Gemini snapshot survey for double degenerates

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