Tentative Identification of Main-Sequence Stars in the Nuclear Bulge of the Galaxy

1974 ◽  
Vol 188 ◽  
pp. L9 ◽  
Author(s):  
Sidney van den Bergh
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Tentative Identification ◽  
The Galaxy

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.

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 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 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.

scholarly journals β Cephei and SPB stars in the Large Magellanic Cloud

2004 ◽  
Vol 193 ◽  
pp. 225-229 ◽  
Author(s):  
Z. Kołaczkowski ◽  
A. Pigulski ◽  
I. Soszyński ◽  
A. Udalski ◽  
M. Szymański ◽  
...  
Keyword(s):  
Main Sequence ◽  
Large Magellanic Cloud ◽  
Progress Report ◽  
Magellanic Cloud ◽  
Main Sequence Stars ◽  
The Galaxy ◽  
Low Order

AbstractThis is a progress report of the study of pulsating main-sequence stars in the LMC. Using the OGLE-II photometry supplemented by the MACHO photometry, we find 64 β Cephei stars in the LMC. Their periods are generally much longer than observed in stars of this type in the Galaxy (the median value is 0.27 d compared with 0.17 d in the Galaxy). In 20 stars with short periods attributable to the β Cephei-type instability, we also find modes with periods longer than ~0.4d. They are likely low-order g modes, which means that in these stars both kinds of variability, β Cephei and SPB, are observed. We also show examples of the multiperiodic SPB stars in the LMC, the first beyond our Galaxy.

scholarly journals Chemical Abundances in Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 215-224 ◽  
Author(s):  
Manuel Peimbert
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Type Ii ◽  
Orion Nebula ◽  
Main Sequence Stars ◽  
Chemical Abundances ◽  
Element Abundances ◽  
Oxygen Gradient ◽  
The Galaxy ◽  
Halo Population

PN can be divided into four types depending on their chemical composition. In order of decreasing heavy element abundances the types are: I) He and N rich, II) intermediate population, III) high velocity, and IV) halo population. The type II PN are overabundant in N and C relative to the Orion Nebula. Well defined gradients across the galactic disk of He, N and O are derived from type II PN; the oxygen gradient is similar to the metallicity gradient derived from GK giants and F main sequence stars. By comparing the O, Ne and S abundances of PN of types III and IV with the Fe abundances of stars of similar population it is found that the O, Ne and S enrichment in the Galaxy probably took place before the Fe enrichment.

scholarly journals Optical and H-Alpha Emission from Unresolved Red Dwarf Stars in the Galaxy

1990 ◽  
Vol 139 ◽  
pp. 107-109
Author(s):  
G. Szécsényi-Nagy
Keyword(s):  
Main Sequence ◽  
Stellar Content ◽  
Main Sequence Stars ◽  
M Dwarfs ◽  
Dwarf Stars ◽  
Alpha Emission ◽  
Cool Stars ◽  
Red Dwarfs ◽  
The Galaxy ◽  
Red Dwarf Stars

Although many of the nearest dim and cool stars (the red dwarfs) were catalogued in the early sixties, the majority of the astronomers did not realize that these objects provide almost nine tenths of all the stars in our Galaxy. In fact 90-95% of the stars in the solar vicinity (r ≤ 25 pc) are main sequence stars, and at least 80% of them are M dwarfs. Outside the main sequence (MS) one can find a few subdwarfs and somewhat more white dwarfs, but the contribution of this latter type is not known precisely. Estimates range between 4% and 8%. The relative frequency of giants and supergiants can not be determined from the census of the local star population because they are not represented in a statistically meaningful number. But investigations of much greater cosmic volumes demonstrate that luminosity classes Ia, Ib, II, III, and IV altogether contribute fewer than 1% of the stellar content of the Galaxy.

scholarly journals Colours and Teff of Main Sequence Stars Covering the Galactic Metallicity Range

1995 ◽  
Vol 164 ◽  
pp. 368-368
Author(s):  
A. Alonso ◽  
S. Arribas ◽  
C. Martínez-Roger
Keyword(s):  
Temperature Scale ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Flux Method ◽  
Absolute Flux ◽  
The Galaxy ◽  
Effective Temperatures ◽  
Bolometric Correction ◽  
Flux Calibration ◽  
Hr Diagram

We present the results of a general programme aimed to study the effects of metallicity on the temperature scale of late main sequence stars (F0-K5). A sample of approximately 400 stars with published UBV(RI) and ubvy – β photometry has been collected from the literature. A three years campaign of observations (Alonso et al. 1994b) was carried out to obtain JHK photometry in order to apply the InfraRed Flux Method (IRFM) to derive effective temperatures. The effect of metallicity on Colour-Colour IR diagrams is discussed. The absolute flux calibration in the IR was revised in Alonso et al. (1994a). The effect of metallicity on the bolometric correction has been studied in Alonso et al. (1995) in order to derive bolometric fluxes. The temperatures have been derived by applying the IRFM using new Kurucz models. Teff = f(Colours, [Fe/H], log(g)) relations are obtained for dwarfs covering the ranges 4000K ≤ Teff ≤ 8000K, 3.5 ≤ logg ≤ 5.00, +0.5 ≤ [Fe/H] ≤ −3.00 which expands considerably the database of previous works. These relations are used to check atmosphere models through the analysis of UBV RIJH Kubvy – β synthetic photometry in combination with the IRFM. The transformation from the theoretical HR diagram into an observational one is analyzed with the new relations. The influence of these points on the study of the evolution of the Galaxy is briefly discussed.

scholarly journals A Flatter metallicity gradient in the Galactic disk: non-LTE abundance calculations of OB stars

2003 ◽  
Vol 212 ◽  
pp. 162-163 ◽  
Author(s):  
Simone Daflon ◽  
Katia Cunha
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Main Sequence Stars ◽  
Chemical Abundances ◽  
Stellar Abundances ◽  
Ob Stars ◽  
The Galaxy ◽  
Aluminum Silicon

We present non-LTE abundances of carbon, nitrogen, oxygen, magnesium, aluminum, silicon and sulfur, derived for a sample of 70 O9-B2 main sequence stars of the Galactic disk and analyze the distribution of the chemical abundances in terms of radial gradients within 4.4-12.9 kpc from the center of the Galaxy. The derived gradients are flatter than those presented by the most recent studies about the radial gradients of stellar abundances.

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