نتایج جستجو برای: giant star
تعداد نتایج: 129999 فیلتر نتایج به سال:
Open and globular star clusters have served as benchmarks for the study of stellar evolution owing to their supposed nature as simple stellar populations of the same age and metallicity. After a brief review of some of the pioneering work that established the importance of imaging stars in these systems, we focus on several recent studies that have challenged our fundamental picture of star clu...
Type Ia supernovae are important cosmological distance indicators. Each of these bright supernovae supposedly results from the thermonuclear explosion of a white dwarf star that, after accreting material from a companion star, exceeds some mass limit, but the true nature of the progenitor star system remains controversial. Here we report the spectroscopic detection of circumstellar material in ...
We argue that the bursting, transient X-ray source GRO J1744-28 is a binary consisting of a very low-mass (M ≈ 0.2M⊙), highly evolved giant star that is transferring mass by Roche lobe overflow onto a high-mass (M ≈ 1.8M⊙) neutron star. We explore a picture in which the bursts are due to thermonuclear flashes in matter that has accreted onto the neutron star. We attribute the unusually hard spe...
Relativistic nuclear energy density functionals (RNEDF) have become a standard framework for nuclear structure studies of ground-state properties and collective excitations over the entire nuclide chart [1]. By employing recent observational constraints on the neutron star mass, a universal RNEDF has been established that simultaneously describes the properties of finite nuclei and neutron star...
The star 1SWASP J024743.37−251549.2 was recently discovered to be a binary star in which an A-type dwarf star eclipses the remnant of a disrupted red giant star (WASP 0247−25B). The remnant is in a rarely-observed state evolving to higher effective temperatures at nearly constant luminosity prior to becoming a very low-mass white dwarf composed almost entirely of helium, i.e., it is a pre-He-WD...
Photoevaporation driven by the ultraviolet radiation from massive stars severely limits the lifetime of protoplanetary discs around stars formed within stellar clusters. I investigate the resulting influence of clustered environments on the probability of giant planet formation, and show that for clusters as rich, or richer than, Orion, the time available for planet formation is likely to be li...
We report the results of a photometric search for giant stars associated with the cores of four high velocity clouds (HVCs) – two of which are compact HVCs – using the Las Campanas Du Pont 2.5 meter and Cerro Tololo Blanco 4 meter telescopes in combination with a system of filters (Washington M , T2 + DDO51) useful for identifying low surface gravity, evolved stars. Identical observations of ne...
The rotation of horizontal branch stars places important constraints on angular momentum evolution in evolved stars and therefore rotational mixing on the giant branch. Prompted by new observations of rotation rates of horizontal branch stars, we calculate simple models for the angular momentum evolution of a globular cluster giant star from the base of the giant branch to the star’s appearance...
We first review on the peculiar characteristics of the bursting and flaring activity of the Soft Gamma-ray Repeaters and Anomalous Xray Pulsars. We then report on the properties of the SGR 1806-20’s Giant Flare occurred on 2004 December 27th, with particular interest on the pre and post flare intensity/hardness correlated variability. We show that these findings are consistent with the picture ...
In this letter we present the discovery of a very light planetary companion to the star μAra (HD 160691). The planet orbits its host once every 9.5 days, and induces a sinusoidal radial velocity signal with a semi-amplitude of 4.1 m s, the smallest Doppler amplitude detected so far. These values imply a mass of m2 sin i=14 M⊕ (earth-masses). This detection represents the discovery of a planet w...
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