100,618 research outputs found
Lithium abundances of bulge RGB stars (Lebzelter+, 2012)
No full textThe table presents the coordinates (J2000) and J-, H-, and K-band magnitudes from the 2MASS catalogue, the radial velocities measured from the spectra, their estimated temperature and surface gravity log g,
general metal and lithium abundances for the Li-detected stars, as well
as a flag for foreground star candidates. The foreground star candidates
were selected by their proper motion in the SPM4 catalogue. All stars are located in a 25 arcmin diameter field centred on the Galactic coordinates (l,b)=(0,-10).
(1 data file)
Semi-regular red giants as distance indicators
No full textContext. Semi-regular variables (SRVs) are similar to Miras in brightness, and they also follow one or more period–luminosity relations (PLRs), though not necessarily the same one as Miras. As potential standard candles they are more challenging than Miras because of their smaller variability amplitudes and less regular light curves, but they are substantially more numerous and especially promising for probing old stellar populations.
Aims. We aim to characterise the variability of SRVs, specifically focusing on their connection with Miras, in order to prepare the ground for investigating their potential as distance indicators.
Methods. We examine SRVs and Miras in the Magellanic Clouds from OGLE-III observations, with data from Gaia and 2MASS. After cleaning the sample of variability periods unrelated to pulsation, we classify each source by chemical type and combination of pulsation modes. We examine the results in terms of global photometric and pulsation properties.
Results. We identify four SRV groups that fit the general evolutionary scenario predicted by theory. SRVs dominated by fundamental-mode pulsation are very similar to Miras, especially if mono-periodic. They further split into two subgroups, one of which follows the same sequence as Miras in the period–luminosity and period–amplitude diagrams, without discontinuity.
Conclusions. The similarities between Miras and SRVs suggest that the latter can be adopted as distance indicators in a way that is complementary to the use of the former, thereby at least doubling the available number of long-period variables (LPVs) suitable for use as distance indicators. The traditional amplitude-based separation between Miras and SRVs is not necessarily appropriate, and a more physically sound criterion should also involve pulsation periods. While this would require comparatively longer time-series, they are expected to become accessible in the coming years even for weak sources thanks to current and future large-scale surveys. The table of reclassified LPVs is made public
A CRIRES-POP Atlas of the K Giant 10 Leo
No full textThe CRIRES-POP project (Lebzelter et al. [2]) will provide a public database of high-res, high S:N, NIR spectra of stars spanning the HR diagram. A relevant part of this library for the evolved star community will be the high quality reference spectra of several cool evolved giants. These atlases will be valuable references for future research, and will include comprehensive line identifications, abundance measurements, and isotope ratios, alongside stellar parameters derived through the inclusion of other data sources. All CRIRES observations have been completed, and reduction and analysis of the spectra, including improved telluric subtraction and wavelength calibration, is ongoing. We present here preliminary results of the first atlas to be produced, that of K1 III giant 10 Leo
The Contribution of Asymptotic Giant Branch Stars to the Infrared Luminosities of Galaxies
No full textUsing resolved stellar photometry in Hubble Space Telescope WFC3 images of 22 nearby galaxies, we measure the fraction of near-infrared (NIR) luminosity produced by short-lived asymptotic giant branch (AGB) stars. While AGB stars represent a negligible number fraction of stars in a given galaxy, they can contribute as much as 30% of the total NIR flux, even though local galaxies have large populations of red giant branch stars. In the early Universe, the AGB contribution to the total IR luminosity could be as high as 80%. For younger metal-rich galaxies, the AGB models used in this study tend to under-predict the contribution of the AGB to the galaxy's luminosity (at NIR wavelengths). The same models tend to over-predict the AGB for old metal-poor systems
Low-mass lithium-rich AGB stars in the Galactic bulge: evidence for cool bottom processing?
No full textLetter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Modelling Long-Period Variables in the Gaia Era
No full textLuminous red giant stars exhibit variability due to stellar pulsation, that is interconnected with uncertain processes (convection, mass loss and dust formation) and results in observable features that are strongly related to stellar properties. These so-called long-period variables (LPVs) provide us with a powerful tool to infer global stellar parameters and constrain the physics of late evolutionary phases in intermediate- and old-age stellar populations. Moreover, their period-luminosity relations represent a highly promising distance indicator. Large-scale optical microlensing surveys carried out during the last few decades made ideal laboratories out of the Magellanic Clouds to investigate the ensemble properties of LPVs with low impact from distance and interstellar extinction. Building on those results, the second data release (DR2) from the Gaia mission is providing new insight on these objects and novel methods to exploit them in the study of the evolution of stars and stellar populations. These results, together with related developments, are summarized here...
Li abundnces along the RGB: FLAMES_GIRAFFE Spectra of a large sample of low-mass bulge stars
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