Search results for "Red-giant branch"
showing 5 items of 5 documents
A parametric description of the 3D structure of the Galactic bar/bulge using the VVV survey
2017
We study the structure of the inner Milky Way using the latest data release of the Vista Variables in Via Lactea (VVV) survey. The VVV is a deep near-infrared, multi-colour photometric survey with a coverage of 300 square degrees towards the Bulge/Bar. We use Red Clump (RC) stars to produce a high-resolution dust map of the VVV's field of view. From de-reddened colour-magnitude diagrams we select Red Giant Branch stars to investigate their 3D density distribution within the central 4 kpc. We demonstrate that our best-fit parametric model of the Bulge density provides a good description of the VVV data, with a median percentage residual of 5$\%$ over the fitted region. The strongest of the o…
Spectroscopy of red giants in the open clusters NGC 1545 and Tr2
2011
The results of local thermodynamic equilibrium (LTE) abundance analysis are presented for four red giants in the fields of open clusters NGC 1545 and Tr2. The membership of HD 27276, HD 27292 and HD 16068 was confirmed and the age of NGC 1545 was updated: log age(yr) = 7.95. A mild deficiency of iron-group elements was found on average for NGC 1545 and Tr2, [Fe/H]=−0.13 and −0.07 with an uncertainty of about 0.08 dex. Oxygen and carbon are moderately depleted in all cluster giants, [O/Fe]=−0.23 ± 0.05 dex and [C/Fe]=−0.56 ± 0.07 dex on average. Nitrogen is enhanced, [N/Fe] values in range +0.4 to +1.2 dex, and lithium depleted. Sodium is slightly enhanced, [Na/Fe]=+0.26 ± 0.04 dex on avera…
Radio-ejection and bump-related orbital period gap of millisecond binary pulsars
2005
The monotonic increase of the radius of low mass stars during their ascent on the red giant branch halts when they suffer a temporary contraction. This occurs when the hydrogen burning shell reaches the discontinuity in hydrogen content left from the maximum increase in the convective extension, at the time of the first dredge up, and produces a well known "bump" in the luminosity function of the red giants of globular clusters. If the giant is the mass losing component in a binary in which mass transfer occurs on the nuclear evolution time scale, this event produces a temporary stop in the mass transfer, which we will name "bump related" detachment. If the accreting companion is a neutron …
High-resolution spectroscopy of two metal-poor red giants: HD 232078 and HD 218732
2010
An abundance analysis for 35 chemical elements based on a high-resolution (R = 67 000) optical spectra of two metal-poor ([Fe/H] ≈ - 1.50) halo red giants, HD 232078 and HD 218732, is presented. Abundances of 10 chemical elements were derived for the first time. Both red giants are chromospherically active and optically variable, located close to the red giant branch tip. Abundances of both stars generally follow typical halo star abundance distribution, while HD 218732 should have experienced a deep mixing episode and could be a first ascent asymptotic giant branch star.
The Gaia-ESO Survey: impact of extra mixing on C and N abundances of giant stars
2018
The GES survey using FLAMES at the VLT has obtained high-resolution UVES spectra for a large number of giant stars, allowing a determination of the abundances of the key chemical elements C and N at their surface. The surface abundances of these chemical species are well-known to change in stars during their evolution on the red giant branch after the first dredge-up episod, as a result of extra-mixing phenomena. We investigate the effects of thermohaline mixing on C and N abundances using the first comparison between the GES [C/N] determinations with simulations of the observed fields using a model of stellar population synthesis. We explore the effects of thermohaline mixing on the chemic…