scholarly journals Measuring the Absolute Total Intrinsic Redshifts (Surface Gravity Plus the Convective Blueshift) of the Main-sequence Stars and Red Giants using Gaia Data

2019 ◽  
Vol 871 (1) ◽  
pp. 119
Author(s):  
De-Chang Dai ◽  
ZhiGang Li ◽  
Dejan Stojkovic
Keyword(s):  
Main Sequence ◽  
Surface Gravity ◽  
Red Giants ◽  
Main Sequence Stars ◽  
The Absolute

scholarly journals The empirical Gaia G-band extinction coefficient

2018 ◽  
Vol 614 ◽  
pp. A19 ◽  
Author(s):  
C. Danielski ◽  
C. Babusiaux ◽  
L. Ruiz-Dern ◽  
P. Sartoretti ◽  
F. Arenou
Keyword(s):  
Extinction Coefficient ◽  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Empirical Method ◽  
Spectral Energy ◽  
Red Giants ◽  
Main Sequence Stars ◽  
Empirical Estimation ◽  
Two Samples ◽  
Data Release

Context. The first Gaia data release unlocked the access to photometric information for 1.1 billion sources in the G-band. Yet, given the high level of degeneracy between extinction and spectral energy distribution for large passbands such as the Gaia G-band, a correction for the interstellar reddening is needed in order to exploit Gaia data. Aims. The purpose of this manuscript is to provide the empirical estimation of the Gaia G-band extinction coefficient kG for both the red giants and main sequence stars in order to be able to exploit the first data release DR1. Methods. We selected two samples of single stars: one for the red giants and one for the main sequence. Both samples are the result of a cross-match between Gaia DR1 and 2MASS catalogues; they consist of high-quality photometry in the G-, J- and KS-bands. These samples were complemented by temperature and metallicity information retrieved from APOGEE DR13 and LAMOST DR2 surveys, respectively. We implemented a Markov chain Monte Carlo method where we used (G – KS)0 versus Teff and (J – KS)0 versus (G – KS)0, calibration relations to estimate the extinction coefficient kG and we quantify its corresponding confidence interval via bootstrap resampling. We tested our method on samples of red giants and main sequence stars, finding consistent solutions. Results. We present here the determination of the Gaia extinction coefficient through a completely empirical method. Furthermore we provide the scientific community with a formula for measuring the extinction coefficient as a function of stellar effective temperature, the intrinsic colour (G – KS)0, and absorption.

scholarly journals Mass-Losing Peculiar Red Giants: The Comparison Between Theory and Observations

1989 ◽  
Vol 106 ◽  
pp. 339-347
Author(s):  
M. Jura
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Main Sequence ◽  
Mass Loss Rate ◽  
Solar Neighborhood ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Main Sequence Stars ◽  
Dwarf Stars ◽  
White Dwarf Stars

AbstractThe mass loss from evolved red giants is considered. It seems that red giants on the Asymptotic Giant Branch (AGB) are losing between 3 and 6 10-4 MΘ kpc-2 yr-1 in the solar neighborhood. If all the main sequence stars between 1 and 5 MΘ ultimately evolve into white dwarfs with masses of 0.7 MΘ the predicted mass loss rate in the solar neighborhood from these stars is 8 10-4 MΘ kpc-2 yr-1. Although there are still uncertainties, it appears that there is no strong disagreement between theory and observation. However, it could also be that we have not yet identified much of the source of the mass-loss from pre-white dwarf stars.

scholarly journals An Improvement in the Visual Surface Brightness Scale for B5-F5 Main Sequence Stars

1985 ◽  
Vol 111 ◽  
pp. 523-524
Author(s):  
L. Pastori ◽  
G. Malaspina
Keyword(s):  
Surface Brightness ◽  
Color Index ◽  
Main Sequence ◽  
Surface Gravity ◽  
Main Sequence Stars ◽  
Interferometric Method ◽  
Gravity Effects ◽  
Good Agreement ◽  
Angular Diameters

Angular diameters of 593 B5-F5 main sequence stars listed in the “Catalogue of apparent diameters and absolute radii of stars” (CADARS; Fracassini et al. 1981) have been analysed in order to improve the precision of the visual surface brightness Sv. The new relations between this quantity and the color index (B-V)o turn out to be in good agreement with those found with the interferometric method (Barnes et al. 1978). Moreover, the results suggest that surface gravity effects may bias the Sv-(B-V)o relations.

scholarly journals Observational Evidence for Atmospheric Chemical Composition Peculiarities Relevant to Stellar Evolution

1977 ◽  
Vol 4 (2) ◽  
pp. 119-135
Author(s):  
B. E. J. Pagel
Keyword(s):  
Chemical Composition ◽  
Stellar Evolution ◽  
Supernova Remnant ◽  
Main Sequence ◽  
Observational Evidence ◽  
Galactic Evolution ◽  
Red Giants ◽  
Main Sequence Stars ◽  
Separation Processes ◽  
Cassiopeia A

Abundance peculiarities in successive stages of stellar evolution are reviewed. Main-sequence stars show anomalies in lithium and, on the upper main sequence, the Am, Ap and Bp effects, which may be largely due to separation processes, and helium and CNO anomalies to which nuclear evolution and mixing could have contributed. Red giants of both stellar Populations commonly show more or less extreme variations among the C, N, 0 isotopes, sometimes accompanied by s-process enhancement, due to mixing out in various evolutionary stages. Detailed anomalies expected from galactic evolution are also briefly considered. Novae show strong effects in C, N, 0 and synthesis of heavier elements is displayed by the supernova remnant Cassiopeia A.

scholarly journals On the Progenitor of SNR 0509-67.5

2011 ◽  
Vol 7 (S281) ◽  
pp. 337-340
Author(s):  
Ashley Pagnotta ◽  
Bradley E. Schaefer
Keyword(s):  
Main Sequence ◽  
Large Magellanic Cloud ◽  
Red Giants ◽  
Main Sequence Stars ◽  
The West ◽  
Companion Star ◽  
X Ray ◽  
Type Ia ◽  
Recurrent Nova ◽  
Error Circle

AbstractWe have used three independent methods to determine an accurate and precise geometric center of SNR 0509-67.5, at RA=05:09:31.208, DEC=−67:31:17.48 (J2000). This supernova, which occurred approximately 400 years ago in the Large Magellanic Cloud, was confirmed to be a Type Ia by Rest et al. (2005), Rest et al. (2008) based on spectra of a light echo from the eruption. If this supernova had a single-degenerate progenitor system, we would see the “leftover” companion star within a certain distance of the remnant's center. Accounting for an offset due to enhanced ISM in the west-southwest quadrant of the remnant, we find the eruption position to be at RA=05:09:30.976, DEC=−67:31:17.90; the error circle which should contain any possible ex-companion star has a radius of 1.60″ for 99.73% (3-sigma) containment. This accounts for the proper motion of the stars, the possibility of kicks from the supernova, and asymmetries in the explosion and remnant expansion. We find no possible ex-companion stars within this ellipse, to a limiting magnitude of V=26.9: there are no red giants, which precludes symbiotic progenitors, no subgiants, which when combined with the lack of red giants precludes recurrent nova progenitors, and no main sequence stars with mass greater than 1.16 solar masses (V brighter than 22.7 mag), which precludes persistent supersoft X-ray source progenitors. Indeed, all published SD models are eliminated, so we conclude that this particular Type Ia supernova had a double-degenerate progenitor.

scholarly journals The Globular Cluster ω Centauri and its RR Lyrae Variables

1989 ◽  
Vol 111 ◽  
pp. 141-167
Author(s):  
R.J. Dickens
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Red Giants ◽  
Horizontal Branch ◽  
Main Sequence Stars ◽  
Chemical Enrichment ◽  
Rr Lyrae ◽  
Stellar Pulsation ◽  
Stellar Ages ◽  
Period Shift

AbstractThe significance of some of the unusual characteristics of the globular cluster ω Centauri in various fundamental problems is explored. Interest is centred on the properties of the cluster RR Lyraes, and what they can contribute to studies of early cluster chemical enrichment, stellar pulsation, the distance scale, stellar evolution, stellar ages and the Oosterhoff period-shift problem. This article, which is intended to highlight problems and progress rather than give a comprehensive review, includes new results based on photometry of the RR Lyraes, red giants, subgiants, horizontal-branch and main sequence stars in the cluster.

scholarly journals Bipolar flows and jets from stars of different spectral types: Observations

1987 ◽  
Vol 122 ◽  
pp. 39-50
Author(s):  
Martin Cohen
Keyword(s):  
Main Sequence ◽  
Cataclysmic Variables ◽  
Circumstellar Disks ◽  
Red Giants ◽  
Main Sequence Stars ◽  
Hot Stars

The fact that bipolar flows are widespread among stars of very different spectral types is emphasized. First, the stars associated with the phenomenon are divided into broad types: protostars and pre-main-sequence stars; red giants; symbiotic objects; protoplanetaries; planetaries; novae and cataclysmic variables; and peculiar hot stars. Second, the evidence for circumstellar “disks” or toroids is considered among these different categories of star. Finally, the possible role of binarity is discussed.

scholarly journals The rate of planet–star coalescences due to tides and stellar evolution

2019 ◽  
Vol 490 (2) ◽  
pp. 2390-2404
Author(s):  
Alexander V Popkov ◽  
Sergei B Popov
Keyword(s):  
Main Sequence ◽  
Tidal Energy ◽  
Red Giants ◽  
Population Synthesis ◽  
Main Sequence Stars ◽  
Tidal Dissipation ◽  
X Ray ◽  
Different Types ◽  
Near Future ◽  
New Facilities

ABSTRACT Orbits of close-in planets can shrink significantly due to dissipation of tidal energy in a host star. This process can result in star–planet coalescence within the Galactic lifetime. In some cases, such events can be accompanied by an optical or/and UV/X-ray transient. Potentially, these outbursts can be observed in near future with new facilities such as LSST from distances about few Mpc. We use a population synthesis model to study this process and derive the rate of star–planet mergers of different types. Mostly, planets are absorbed by red giants. However, these events, happening with the rate about 3 per year, mostly do not produce detectable transients. The rate of mergers with main sequence stars depends on the effectiveness of tidal dissipation; for reasonable values of stellar tidal quality factor, such events happen in a Milky Way-like galaxy approximately once in 70 yr or more rarely. This rate is dominated by planets with low masses. Such events do not produce bright transients having maximum luminosities ≲ 1036.5 erg s−1. Brighter events, related to massive planets, with maximum luminosity ∼1037.5–1038 erg s−1, have the rate nearly five times smaller.

scholarly journals The Gaia-ESO Survey: Lithium enrichment histories of the Galactic thick and thin disc

2018 ◽  
Vol 610 ◽  
pp. A38 ◽  
Author(s):  
X. Fu ◽  
D. Romano ◽  
A. Bragaglia ◽  
A. Mucciarelli ◽  
K. Lind ◽  
...  
Keyword(s):  
Main Sequence ◽  
Big Bang ◽  
Galactic Cosmic Rays ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Main Sequence Stars ◽  
Lithium Abundance ◽  
Thin Disc ◽  
Relative Contribution ◽  
Solar Metallicity

Lithium abundance in most of the warm metal-poor main sequence stars shows a constarnt plateau (A(Li) ~ 2.2 dex) and then the upper envelope of the lithium vs. metallicity distribution increases as we approach solar metallicity. Meteorites, which carry information about the chemical composition of the interstellar medium (ISM) at the solar system formation time, show a lithium abundance A(Li) ~ 3.26 dex. This pattern reflects the Li enrichment history of the ISM during the Galaxy lifetime. After the initial Li production in big bang nucleosynthesis, the sources of the enrichment include asymptotic giant branch (AGB) stars, low-mass red giants, novae, type II supernovae, and Galactic cosmic rays. The total amount of enriched Li is sensitive to the relative contribution of these sources. Thus different Li enrichment histories are expected in the Galactic thick and thin disc. We investigate the main sequence stars observed with UVES in Gaia-ESO Survey iDR4 catalogue and find a Li- [α/Fe] anticorrelation independent of [Fe/H], Teff, and log (g). Since in stellar evolution different α enhancements at the same metallicity do not lead to a measurable Li abundance change, the anticorrelation indicates that more Li is produced during the Galactic thin disc phase than during the Galactic thick disc phase. We also find a correlation between the abundance of Li and s-process elements Ba and Y, and they both decrease above the solar metallicity, which can be explained in the framework of the adopted Galactic chemical evolution models.

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