نتایج جستجو برای: stars
تعداد نتایج: 56510 فیلتر نتایج به سال:
We present proper motions of 72 T Tauri stars located in the central region of Taurus-Auriga (Tau-Aur). These proper motions are taken from a new proper motion catalogue called STARNET. Our sample comprises 17 classical T Tauri stars (CTTS) and 55 weak-line T Tauri stars (WTTS), most of the latter discovered by ROSAT. 53 stars had no proper motion measurement before. Kinematically, 62 of these ...
The nature of Large Magellanic Cloud (LMC) microlensing is determined by the location of the microlensing source stars. If the source stars are in the LMC then LMC microlensing is predominantly halo-lensing, if the source stars are located behind the LMC, then LMC microlensing is dominated by self-lensing. We attempt to distinguish between source stars drawn from the average population of the L...
stars: magnetic fields It is essential for the understanding of stellar structure models of high mass stars to explain why constant stars, non-pulsating chemically peculiar hot Bp stars and pulsating stars co-exist in the slowly pulsating B stars and β Cephei instability strips. We have conducted a search for magnetic fields in the four Bp stars HD 55522, HD 105382, HD 131120, and HD 138769 whi...
We investigate the evolution of collisionally merged stars with mass of ∼ 100M⊙ which might be formed in dense star clusters. We assumed that massive stars with several tens M⊙ collide typically after ∼ 1Myr of the formation of the cluster and performed hydrodynamical simulations of several collision events. Our simulations show that after the collisions, merged stars have extended envelopes an...
We report the discovery of two new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The identification of both stars has been confirmed spectroscopically. One is a cool RCB star (T ef f ∼ 5000 K) characterized by very strong Swan bands of C 2 and violet bands of CN, and weak or absent Balmer lines, G-band and 12 C 13 C bands. The se...
Globular clusters are ideal laboratories to study the evolution of low-mass stars. In this work we concentrate on three types of hot stars observed in globular clusters: horizontal branch stars, UV bright stars, and white dwarfs. After providing some historical background and information on gaps and blue tails we discuss extensively hot horizontal branch stars in metal-poor globular clusters, e...
Frequency analysis of more than 300 stars of the ogle data base on Sculptor galaxy has led to the discovery of 18 double-mode RR Lyrae (RRd) variables. This yields a 20% incidence rate for double-mode pulsation among the variables previously classified as first overtone RR Lyrae stars in this galaxy. Most of the RRd stars cover the period range of 0. 47 < P0 < 0. 49 but there are two stars with...
We report the discovery of two new R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC) using the MACHO project photometry database. The identification of both stars has been confirmed spectroscopically. One is a cool RCB star (T ef f ∼ 5000 K) characterized by very strong Swan bands of C 2 and violet bands of CN, and weak or absent Balmer lines, G-band and 12 C 13 C bands. The se...
We present optical spectra of 45 intermediate mass Herbig Ae/Be stars. Together with the multi-epoch spectroscopic and photometric data compiled for a large sample of these stars and ages estimated for individual stars by using pre-main sequence evolutionary tracks, we have studied the evolution of emission line activity in them. We find that, on average, the Hα emission line strength decreases...
The existence of faint blue stars far above the galactic plane, which have spectra that are similar to nearby Population I B stars, present several interesting questions. Among them are: Can a Population I B star travel from the disk to a position many kiloparsecs above the plane in a relatively short main sequence lifetime? Is it possible that single massive star formation is occurring far fro...
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