scholarly journals Stellar statistics along the ecliptic and the impact on the K2 mission concept

2014 ◽  
Vol 14 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Andrej Prša ◽  
Annie Robin ◽  
Thomas Barclay
Keyword(s):  
Main Sequence ◽  
Target Selection ◽  
Ecliptic Plane ◽  
Galactic Latitude ◽  
Gold Mine ◽  
Main Sequence Stars ◽  
Satellite Attitude ◽  
The Galaxy ◽  
Orbital Periods ◽  
The Impact

AbstractK2 is the mission concept for a repurposedKeplermission that uses two reaction wheels to maintain the satellite attitude and provide ~81 days of coverage for ten 105 deg2fields along the ecliptic in the first 2.5 years of operation. We examine stellar populations based on the updated Besançon model of the Galaxy, comment on the general properties for the entire ecliptic plane, and provide stellar occurrence rates in the first six tentative K2 campaigns grouped by spectral type and luminosity class. For each campaign we distinguish between main the sequence stars and giants, and provide their density profile as a function of galactic latitude. We introduce the crowding metric that serves for optimized target selection across the campaigns. For all main sequence stars we compute the expected planetary occurrence rates for three planet sizes: 2–4, 4–8 and 8–32 R⊕with orbital periods up to 50 days. In conjunction with Gaia and the upcoming Transiting Exoplanet Survey Satellite and Plato missions, K2 will become a gold mine for stellar and planetary astrophysics.

scholarly journals The Evolutionary Status of the Secondaries of Cataclysmic Binaries

1983 ◽  
Vol 72 ◽  
pp. 257-262
Author(s):  
H. Ritter
Keyword(s):  
Probability Distribution ◽  
Main Sequence ◽  
The Other ◽  
Initial Mass ◽  
Evolutionary Status ◽  
Mass Ratio ◽  
Main Sequence Stars ◽  
Cataclysmic Binaries ◽  
Low Mass ◽  
Orbital Periods

ABSTRACTIt is shown that the secondary components of cataclysmic binaries with orbital periods of less than ~10 hours are indistinguishable from ordinary low-mass main-sequence stars and that, therefore, they are essentially unevolved. On the other hand, it is shown that, depending on the mass ratio of the progenitor system, the secondary of a cataclysmic binary could be significantly evolved. The fact that nevertheless most of the observed secondaries are essentially unevolved can be accounted for by assuming that the probability distribution for the initial mass ratio is not strongly peaked towards unity mass ratio.

scholarly journals Chemically Peculiar Stars Among Spectroscopic Binaries – Revisited

1993 ◽  
Vol 138 ◽  
pp. 137-142 ◽  
Author(s):  
Wilhelm Seggewiss
Keyword(s):  
Relative Frequency ◽  
Main Sequence ◽  
Statistical Investigation ◽  
Spectroscopic Binaries ◽  
Main Sequence Stars ◽  
Eccentric Orbits ◽  
Peculiar Stars ◽  
Orbital Periods ◽  
Chemically Peculiar Stars ◽  
The Masses

AbstractThis paper presents a new statistical investigation of peculiar A-type stars (Am, Ap, Hg-Mn) among spectroscopic binary (SB) stars. The relative frequency of Am (CP 1) stars is 55% in the spectral range A1 to A6 of main-sequence stars. The Ap (CP 2) stars amount to 15% in the range B9 to A2. The Hg-Mn stars are concentrated to the spectral types B8 to AO and reach a relative frequency of 23%. The Am SB stars have the shortest orbital periods and the smallest eccentricities (30% circular) whereas the Ap SB stars show a strong tendency to long periods and highly eccentric orbits (only 10% circular). The masses of the Am stars agree with the masses of non-peculiar SB stars of corresponding spectral type.

First galaxy SED: Contribution from pre-main-sequence stars

2019 ◽  
Vol 15 (S341) ◽  
pp. 287-288
Author(s):  
Hiroto Mitani ◽  
Naoki Yoshida ◽  
Kazuyuki Omukai ◽  
Takashi Hosokawa
Keyword(s):  
Energy Distribution ◽  
Main Sequence ◽  
Spectral Energy Distribution ◽  
Mass Function ◽  
Initial Mass Function ◽  
Spectral Energy ◽  
Population Synthesis ◽  
Main Sequence Stars ◽  
The Galaxy ◽  
First Galaxies

AbstractWe calculate the spectral energy distribution of the first galaxies which contain pre-main-sequence stars by using the stellar evolution code Modules for Experiments in Stellar Astrophysics, the spectra model BT-Settl, and the stellar population synthesis code PEGASE. We calculate the galaxy spectral energy distribution for Salpeter Initial Mass Function. We find that very young first galaxies are bright also in mid-infrared, and the contribution of pre-main-sequence stars can be significant over 0.1 Myr after a star-formation episode.

scholarly journals The Impact of Starspots on Mass and Age Estimates for Pre-main Sequence Stars

2015 ◽  
Vol 10 (S314) ◽  
pp. 91-94
Author(s):  
Garrett Somers ◽  
Marc H. Pinsonneault
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Late Type ◽  
Main Sequence Stars ◽  
Eclipsing Binary ◽  
Lithium Depletion ◽  
The Impact ◽  
Age Estimates ◽  
Hr Diagram

AbstractWe investigate the impact of starspots on the evolution of late-type stars during the pre-main sequence (pre-MS). We find that heavy spot coverage increases the radii of stars by 4–10%, consistent with inflation factors in eclipsing binary systems, and suppresses the rate of pre-MS lithium depletion, leading to a dispersion in zero-age MS Li abundance (comparable to observed spreads) if a range of spot properties exist within clusters from 3-10 Myr. This concordance with data implies that spots induce a range of radii at fixed mass during the pre-MS. These spots decrease the luminosity and Teff of stars, leading to a displacement on the HR diagram. This displacement causes isochrone derived masses and ages to be systematically under-estimated, and can lead to the spurious appearance of an age spread in a co-eval population.

scholarly journals Metallicity Mapping with gri Photometry: The Virgo Overdensity and the Halos of the Galaxy

2009 ◽  
Vol 5 (S262) ◽  
pp. 127-130
Author(s):  
Timothy C. Beers ◽  
Deokkeun An ◽  
Jennifer A. Johnson ◽  
Marc H. Pinsonneault ◽  
Donald M. Terndrup ◽  
...  
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Abundance Estimates ◽  
The Galaxy ◽  
Metal Abundance ◽  
Nearby Stars ◽  
Metal Abundances ◽  
Photometric Measurements ◽  
Halo Population ◽  
Recent Interpretation

AbstractWe describe the methodology required for estimation of photometric estimates of metallicity based on the SDSS gri passbands, which can be used to probe the properties of main-sequence stars beyond ~10 kpc, complementing studies of nearby stars from more metallicity-sensitive color indices that involve the u passband. As a first application of this approach, we determine photometric metal abundance estimates for individual main-sequence stars in the Virgo Overdensity, which covers almost 1000 deg2 on the sky, based on a calibration of the metallicity sensitivity of stellar isochrones in the gri filter passbands using field stars with well-determined spectroscopic metal abundances. Despite the low precision of the method for individual stars, internal errors of σ[Fe/H]~0.1 dex can be achieved for bulk stellar populations. The global metal abundance of the Virgo Overdensity determined in this way is 〈[Fe/H]〉 = −2.0±0.1 (internal) ±0.5 (systematic), from photometric measurements of 0.7 million stars with heliocentric distances from ~10 kpc to ~20 kpc. A preliminary metallicity map, based on results for 2.9 million stars in the northern SDSS DR-7 footprint, exhibits a shift to lower metallicities as one proceeds from the inner- to the outer-halo population, consistent with recent interpretation of the kinematics of local samples of stars with spectroscopically available metallicity estimates and full space motions.

scholarly journals NIR Spectroscopy of the Most Massive Open Cluster in the Galaxy: Westerlund 1

2007 ◽  
Vol 3 (S246) ◽  
pp. 113-114 ◽  
Author(s):  
S. Mengel ◽  
L. E. Tacconi-Garman
Keyword(s):  
Cluster Expansion ◽  
Main Sequence ◽  
Velocity Dispersion ◽  
Open Cluster ◽  
Nir Spectroscopy ◽  
Radial Velocities ◽  
Main Sequence Stars ◽  
Central Wavelength ◽  
Cluster Mass ◽  
The Galaxy

AbstractUsing ISAAC/VLT, we have obtained individual spectra of all NIR-bright stars in the central 2′ × 2′ of the cluster Westerlund 1 (Wd 1) with a resolution of R ≈ 9000 at a central wavelength of 2.30 μm. This allowed us to determine radial velocities of ten post-main-sequence stars, and from these values a velocity dispersion. Assuming virial equilibrium, the dispersion of σ = 8.4 km/s leads to a total dynamical cluster mass of 1.25 × 105M⊙, comparable to the photometric mass of the cluster. There is no extra-virial motion which would have to be interpreted as a signature of cluster expansion or dissolution.

scholarly journals Observed binary populations reflect the Galactic history

2020 ◽  
Vol 641 ◽  
pp. A163 ◽  
Author(s):  
J. Vos ◽  
A. Bobrick ◽  
M. Vučković
Keyword(s):  
Mass Transfer ◽  
Main Sequence ◽  
Fine Tuning ◽  
Red Giants ◽  
Core Mass ◽  
The Galaxy ◽  
History Of ◽  
Low Mass ◽  
Orbital Periods ◽  
Binary Evolution

Context. Wide hot subdwarf B (sdB) binaries with main-sequence companions are outcomes of stable mass transfer from evolved red giants. The orbits of these binaries show a strong correlation between their orbital periods and mass ratios. The origins of this correlation have, so far, been lacking a conclusive explanation. Aims. We aim to find a binary evolution model which can explain the observed correlation. Methods. Radii of evolved red giants, and hence the resulting orbital periods, strongly depend on their metallicity. We performed a small but statistically significant binary population synthesis study with the binary stellar evolution code MESA. We used a standard model for binary mass loss and a standard metallicity history of the Galaxy. The resulting sdB systems were selected based on the same criteria as was used in observations and then compared with the observed population. Results. We have achieved an excellent match to the observed period-mass ratio correlation without explicitly fine-tuning any parameters. Furthermore, our models produce a very good match to the observed period-metallicity correlation. We predict several new correlations, which link the observed sdB binaries to their progenitors, and a correlation between the orbital period, metallicity, and core mass for subdwarfs and young low-mass helium white dwarfs. We also predict that sdB binaries have distinct orbital properties depending on whether they formed in the Galactic bulge, thin or thick disc, or the halo. Conclusions. We demonstrate, for the first time, how the metallicity history of the Milky Way is imprinted in the properties of the observed post-mass transfer binaries. We show that Galactic chemical evolution is an important factor in binary population studies of interacting systems containing at least one evolved low-mass (Minit <  1.6 M⊙) component. Finally, we provide an observationally supported model of mass transfer from low-mass red giants onto main-sequence stars.

scholarly journals Searching for Faint Planetary Nebulae Using the Digital Sky Survey

2010 ◽  
Vol 27 (2) ◽  
pp. 156-165 ◽  
Author(s):  
George H. Jacoby ◽  
Matthias Kronberger ◽  
Dana Patchick ◽  
Philipp Teutsch ◽  
Jaakko Saloranta ◽  
...  
Keyword(s):  
Main Sequence ◽  
Total Population ◽  
Accurate Estimate ◽  
Close Binary ◽  
Main Sequence Stars ◽  
Chemical Enrichment ◽  
Sky Survey ◽  
The Galaxy ◽  
Data Collections ◽  
Galactic Planetary Nebula

AbstractRecent Hα surveys such as SHS and IPHAS have improved the completeness of the Galactic planetary nebula (PN) census. We now know of ∼3000 PNe in the Galaxy, but this is far short of most estimates, typically ~25 000 or more for the total population. The size of the Galactic PN population is required to derive an accurate estimate of the chemical enrichment rates of nitrogen, carbon, and helium. In addition, a high PN count (>20 000) is strong evidence that most main-sequence stars of mass 1–8 M⊙ will go through a PN phase, while a low count (<10 000) argues that special conditions (e.g. close binary interactions) are required to form a PN. We describe a technique for finding hundreds more PNe using the existing data collections of the digital sky surveys, thereby improving the census of Galactic PNe.

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