Relationships between the Johnson and Kron-Cousins VRI photometric systems

Fernie, J. D.

doi:10.1086/131254

Cited by 80 publications

(71 citation statements)

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“…The extinction laws given by Dean et al (1978) and Rieke & Lebofsky (1985) were adopted. The relations established by Fernie (1983) between the photometric systems of Johnson and Cousins were used, and the results agree well with those obtained from Bessell (1979). Colors from 2MASS were transformed into the Caltech (CIT) system, 2 http://irsa.ipac.caltech.edu/applications/DUST/ and from this into the TCS (Telescopio Carlos Sánchez) system, following the relations established by Carpenter (2001) and Alonso et al (1998) (infrared flux method, IRFM).…”

Section: Abundance Derivationmentioning

confidence: 56%

High-resolution abundance analysis of very metal-poor r-I stars

Mello

Hill

Barbuy

et al. 2014

A&A

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Context. Moderately r-process-enriched stars (r-I; +0.3 ≤ [Eu/Fe] ≤ +1.0) are at least four times as common as those that are greatly enriched in r-process elements (r-II; [Eu/Fe] > +1.0), and the abundances in their atmospheres are important tools for obtaining a better understanding of the nucleosynthesis processes responsible for the origin of the elements beyond the iron peak. Aims. The main aim of this work is to derive abundances for a sample of seven metal-poor stars with −3.4 ≤ [Fe/H] ≤ −2.4 classified as r-I stars, to understand the role of these stars for constraining the astrophysical nucleosynthesis event(s) that is (are) responsible for the production of the r-process, and to investigate whether they differ, in any significant way, from the r-II stars. Methods. We carried out a detailed abundance analysis based on high-resolution spectra obtained with the VLT/UVES spectrograph, using spectra in the wavelength ranges 3400-4500 Å, 6800-8200 Å, and 8700-10 000 Å, with resolving power R ∼ 40 000 (blue arm) and R ∼ 55 000 (red arm). The OSMARCS LTE 1D model atmosphere grid was employed, along with the spectrum synthesis code Turbospectrum. Results. We have derived abundances of the light elements Li, C, and N, the α-elements Mg, Si, S, Ca, and Ti, the odd-Z elements Al, K, and Sc, the iron-peak elements V, Cr, Mn, Fe, Co, and Ni, and the trans-iron elements from the first peak (Sr, Y, Zr, Mo, Ru, and Pd), the second peak (Ba, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Yb), the third peak (Os and Ir, as upper limits), and the actinides (Th) regions. The results are compared with values for these elements for r-II and "normal" very and extremely metal-poor stars reported in the literature, ages based on radioactive chronometry are explored using different models, and a number of conclusions about the r-process and the r-I stars are presented. Hydrodynamical models were used for some elements, and general behaviors for the 3D corrections were presented. Although the abundance ratios of the second r-process peak elements (usually associated with the main r-process) are nearly identical for r-I and r-II stars, the first r-process peak abundance ratios (probably associated with the weak r-process) are more enhanced in r-I stars than in r-II stars, suggesting that differing nucleosynthesis pathways were followed by stars belonging to these two different classifications.

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Section: Abundance Derivationmentioning

confidence: 56%

High-resolution abundance analysis of very metal-poor r-I stars

Mello

Hill

Barbuy

et al. 2014

A&A

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“…This allows us to use the extinction as a further membership criterion, by defining the extinction ranges expected for the cluster members. Since this survey targeted fainter and thus potentially more extincted members, we explored the extinction distribution of our newly found objects with Li I absorption (2000) isochrones for 1, 10, and 100 Myr are displayed, transformed into the Johnsons system according to Fernie (1983) and Getman et al (2012). An extinction vector (Cardelli et al 1989) is also displayed.…”

Section: Membershipmentioning

confidence: 99%

The low-mass stellar population in the young cluster Tr 37

Sicilia‐Aguilar

Kim

Соболев

et al. 2013

A&A

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Aims. We present a study of accretion and protoplanetary disks around M-type stars in the 4 Myr-old cluster Tr 37. With a well-studied solar-type population, Tr 37 is a benchmark for disk evolution. Methods. We used low-resolution spectroscopy to identify and classify 141 members (78 new ones) and 64 probable members, mostly M-type stars. Hα emission provides information about accretion. Optical, 2MASS, Spitzer, and WISE data are used to trace the spectral energy distributions (SEDs) and search for disks. We construct radiative transfer models to explore the structures of fulldisks, pre-transition, transition, and dust-depleted disks. Results. Including the new members and the known solar-type stars, we confirm that a substantial fraction (∼2/5) of disks show signs of evolution, either as radial dust evolution (transition/pre-transition disks) or as a more global evolution (with low small-dust masses, dust settling, and weak/absent accretion signatures). Accretion is strongly dependent on the SED type. About half of the transition objects are consistent with no accretion, and dust-depleted disks have weak (or undetectable) accretion signatures, especially among M-type stars. Conclusions. The analysis of accretion and disk structure suggests a parallel evolution of dust and gas. We find several distinct classes of evolved disks, based on SED type and accretion status, pointing to different disk dispersal mechanisms and probably different evolutionary paths. Dust depletion and opening of inner holes appear to be independent processes: most transition disks are not dust-depleted, and most dust-depleted disks do not require inner holes. The differences in disk structure between M-type and solar-type stars in Tr 37 (4 Myr old) are not as remarkable as in the young, sparse, Coronet cluster (1−2 Myr old), suggesting that other factors, like the environment/interactions in each cluster, are likely to play an important role in the disk evolution and dispersal. Finally, we also find some evidence of clumpy star formation or mini-clusters within Tr 37.

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“…The Alonso calibration is however in the Johnson photometric system only, so we convert the Johnson-Cousin colour of OGLE-2008-BLG-209S using the relation by Fernie (1983), giving (V − I) J = 0.924. Applying Eq.…”

Section: Inconsistenciesmentioning

confidence: 99%

Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars

Bensby¹,

Johnson

Cohen³

et al. 2009

A&A

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Aims. Our aims are twofold. First we aim to evaluate the robustness and accuracy of stellar parameters and detailed elemental abundances that can be derived from high-resolution spectroscopic observations of microlensed dwarf and subgiant stars. We then aim to use microlensed dwarf and subgiant stars to investigate the abundance structure and chemical evolution of the Milky Way Bulge. Contrary to the cool giant stars, with their extremely crowded spectra, the dwarf stars are hotter, their spectra are cleaner, and the elemental abundances of the atmospheres of dwarf and subgiant stars are largely untouched by the internal nuclear processes of the star. Methods. We present a detailed elemental abundance analysis of OGLE-2008-BLG-209S, the source star of a new microlensing event towards the Bulge, for which we obtained a high-resolution spectrum with the MIKE spectrograph on the Magellan Clay telescope. We have performed four different analyses of OGLE-2008-BLG-209S. One method is identical to the one used for a large comparison sample of F and G dwarf stars, mainly thin and thick disc stars, in the Solar neighbourhood. We have also re-analysed three previous microlensed dwarf stars OGLE-2006

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Relationships between the Johnson and Kron-Cousins VRI photometric systems

Abstract: The transformations in (V-R), (V-I), and (R -I) between the photometric systems of Johnson and Kron-Cousins are investigated using the new Johnson URVRI standards now appearing in The Astronomical Almanac. Transformations for very red stars are determined separately from other data.

Cited by 80 publications

References 0 publications

High-resolution abundance analysis of very metal-poor r-I stars

High-resolution abundance analysis of very metal-poor r-I stars

The low-mass stellar population in the young cluster Tr 37

Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars

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