Galactic spiral structure - Proceedings of the Royal Society A
... We describe the structure and composition of six major stellar streams in a population of 20 574 local stars in the New Hipparcos Reduction with known radial velocities. We find that, once fast moving stars are excluded, almost all stars belong to one of these streams. The results of our investigatio ...
... We describe the structure and composition of six major stellar streams in a population of 20 574 local stars in the New Hipparcos Reduction with known radial velocities. We find that, once fast moving stars are excluded, almost all stars belong to one of these streams. The results of our investigatio ...
Revised physical elements of the astrophysically important O9.5+O9
... which the apsidal motion was convincingly detected. Thanks to this, it became the subject of numerous studies. The history of its investigation is summarised in the papers by Hill & Holmgren (1995) and Holmgren et al. (1995) and need not be repeated here. We only mention some more recent studies rel ...
... which the apsidal motion was convincingly detected. Thanks to this, it became the subject of numerous studies. The history of its investigation is summarised in the papers by Hill & Holmgren (1995) and Holmgren et al. (1995) and need not be repeated here. We only mention some more recent studies rel ...
A large-scale CO survey of the Rosette Molecular Cloud: assessing
... between these flows and embedded young clusters or known young luminous stars. These ...
... between these flows and embedded young clusters or known young luminous stars. These ...
Millisecond Pulsars in X-Ray Binaries - CIERA
... in many LMXBs may be hidden by accreted material. Interestingly, the nuclearpowered pulsars offer a statistically unbiased probe of the spin distribution of recycled pulsars and show that this distribution cuts off sharply above 730 Hz, well below the breakup spin rate for most neutron star equation ...
... in many LMXBs may be hidden by accreted material. Interestingly, the nuclearpowered pulsars offer a statistically unbiased probe of the spin distribution of recycled pulsars and show that this distribution cuts off sharply above 730 Hz, well below the breakup spin rate for most neutron star equation ...
Multi-dimensional structure of accreting young stars
... T eff (see e.g. Chabrier & Baraffe 1997). The small scale surface convection resulting from the rapidly decreasing pressure scale height near the surface of a star as well as steep surface radial gradients require a smaller radial spacing near the surface. We thus design the radial grid for the 2D s ...
... T eff (see e.g. Chabrier & Baraffe 1997). The small scale surface convection resulting from the rapidly decreasing pressure scale height near the surface of a star as well as steep surface radial gradients require a smaller radial spacing near the surface. We thus design the radial grid for the 2D s ...
STELLAR MASSES AND STAR FORMATION RATES OF LENSED DUSTY STAR-FORMING... FROM THE SPT SURVEY
... To understand cosmic mass assembly in the Universe at early epochs, we primarily rely on measurements of stellar mass and star formation rate of distant galaxies. In this paper, we present stellar masses and star formation rates of six high-redshift (2.8 ≤ z ≤ 5.7) dusty, star-forming galaxies (DSFG ...
... To understand cosmic mass assembly in the Universe at early epochs, we primarily rely on measurements of stellar mass and star formation rate of distant galaxies. In this paper, we present stellar masses and star formation rates of six high-redshift (2.8 ≤ z ≤ 5.7) dusty, star-forming galaxies (DSFG ...
The Role of Radioactive Isotopes in Astrophysics
... with primary elements. These seed nuclei are required in order that secondary nuclei be produced from them in stars. He emphasized especially 14 N, 18 O, 19 F and 22 Ne in that regard, each of which depends on initial primary C and O nuclei within the initial composition of later-generation massive ...
... with primary elements. These seed nuclei are required in order that secondary nuclei be produced from them in stars. He emphasized especially 14 N, 18 O, 19 F and 22 Ne in that regard, each of which depends on initial primary C and O nuclei within the initial composition of later-generation massive ...
GAS KINEMATICS ON GMC SCALES IN M51 WITH PAWS: CLOUD
... and its global patterns of star formation. In this paper we continue our study of the interacting Whirlpool galaxy M51 (D=7.6 Mpc; Ciardullo et al. 2002), which is more representative of a typical star forming galaxy than the well-studied lower mass galaxies in the Local Group. The unparalleled high ...
... and its global patterns of star formation. In this paper we continue our study of the interacting Whirlpool galaxy M51 (D=7.6 Mpc; Ciardullo et al. 2002), which is more representative of a typical star forming galaxy than the well-studied lower mass galaxies in the Local Group. The unparalleled high ...
The peculiar dipping events in the disc-bearing young
... deepest event observed in the EPIC 204278916 light curve corresponds to τ ≈ 65 per cent, thus implying that at least some of the clumps are a sizable fraction of the parent star. This is however a strong lower limit since a completely opaque spherical clump would produce a symmetrical dip, which we ...
... deepest event observed in the EPIC 204278916 light curve corresponds to τ ≈ 65 per cent, thus implying that at least some of the clumps are a sizable fraction of the parent star. This is however a strong lower limit since a completely opaque spherical clump would produce a symmetrical dip, which we ...
Monte Carlo simulations of X-ray absorption in the interstellar medium
... Although prior measurements of X-ray radiation from the sun exist, the first detection of a cosmical X-ray source in 1962 was still a surprise. It turned out that the signal cames from the binary system Scorpius X-1. Still a long time after this discovery, the physical process leading to the observe ...
... Although prior measurements of X-ray radiation from the sun exist, the first detection of a cosmical X-ray source in 1962 was still a surprise. It turned out that the signal cames from the binary system Scorpius X-1. Still a long time after this discovery, the physical process leading to the observe ...
Physics of the Interstellar and Intergalactic Medium
... (c) Compare this rate coefficient to the rate coefficient for ionization by electron impact [Eq. (2.12)]. 2.3 Consider a dust grain of radius a, and mass M mH , where mH is the mass of an H atom. Suppose that the grain is initially at rest in a gas of H atoms with number density nH and temperature ...
... (c) Compare this rate coefficient to the rate coefficient for ionization by electron impact [Eq. (2.12)]. 2.3 Consider a dust grain of radius a, and mass M mH , where mH is the mass of an H atom. Suppose that the grain is initially at rest in a gas of H atoms with number density nH and temperature ...
Evolution in circumstellar envelopes of Be stars: From disks to rings?
... At the same time the Fe ii and Si ii line emission reappeared with a large width. The narrower doublepeaked emission in O i 8446 had lost a bit in width and two-thirds in peak height. But it had acquired a broad pedestal with the same total width as the other two lines. Like the Hα emission, this ox ...
... At the same time the Fe ii and Si ii line emission reappeared with a large width. The narrower doublepeaked emission in O i 8446 had lost a bit in width and two-thirds in peak height. But it had acquired a broad pedestal with the same total width as the other two lines. Like the Hα emission, this ox ...
Structure of the hot object in the symbiotic prototype Z And during its
... Methods. Analysis of the far ultraviolet, optical low- and high-resolution spectroscopy and U BVR photometry. Reconstruction of the spectral energy distribution (SED) during the outburst. The Raman scattering process. Results. At the initial stages of the outburst the hot object was characterized by ...
... Methods. Analysis of the far ultraviolet, optical low- and high-resolution spectroscopy and U BVR photometry. Reconstruction of the spectral energy distribution (SED) during the outburst. The Raman scattering process. Results. At the initial stages of the outburst the hot object was characterized by ...
PDF - ASSA
... pulsar wind nebulae, the final stages in the evolution of massive stars. There, charged particles are accelerated to extreme velocities. When these particles encounter light or gas in and around the cosmic accelerators, they emit gamma rays. Very high-energy gamma rays can be measured on Earth by obs ...
... pulsar wind nebulae, the final stages in the evolution of massive stars. There, charged particles are accelerated to extreme velocities. When these particles encounter light or gas in and around the cosmic accelerators, they emit gamma rays. Very high-energy gamma rays can be measured on Earth by obs ...
Stellar evolution
Stellar evolution is the process by which a star changes during its lifetime. Depending on the mass of the star, this lifetime ranges from a few million years for the most massive to trillions of years for the least massive, which is considerably longer than the age of the universe. The table shows the lifetimes of stars as a function of their masses. All stars are born from collapsing clouds of gas and dust, often called nebulae or molecular clouds. Over the course of millions of years, these protostars settle down into a state of equilibrium, becoming what is known as a main-sequence star.Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase. Stars with at least half the mass of the Sun can also begin to generate energy through the fusion of helium at their core, whereas more-massive stars can fuse heavier elements along a series of concentric shells. Once a star like the Sun has exhausted its nuclear fuel, its core collapses into a dense white dwarf and the outer layers are expelled as a planetary nebula. Stars with around ten or more times the mass of the Sun can explode in a supernova as their inert iron cores collapse into an extremely dense neutron star or black hole. Although the universe is not old enough for any of the smallest red dwarfs to have reached the end of their lives, stellar models suggest they will slowly become brighter and hotter before running out of hydrogen fuel and becoming low-mass white dwarfs.Stellar evolution is not studied by observing the life of a single star, as most stellar changes occur too slowly to be detected, even over many centuries. Instead, astrophysicists come to understand how stars evolve by observing numerous stars at various points in their lifetime, and by simulating stellar structure using computer models.In June 2015, astronomers reported evidence for Population III stars in the Cosmos Redshift 7 galaxy at z = 6.60. Such stars are likely to have existed in the very early universe (i.e., at high redshift), and may have started the production of chemical elements heavier than hydrogen that are needed for the later formation of planets and life as we know it.