Observations of Taurus A and the Quasi-Stellar Source 3C 273 at 1.53cm

1965 ◽  
Vol 77 ◽  
pp. 178 ◽  
Author(s):  
D. R. W. Williams ◽  
W. J. Welch ◽  
D. D. Thornton
Keyword(s):  
Stellar Source

Interaction of solid bodies with atmospheres of protoplanets

2018 ◽  
Vol 14 (S345) ◽  
pp. 351-352
Author(s):  
Ernst A. Dorfi ◽  
Florian Ragossnig
Keyword(s):  
Kinetic Energy ◽  
Physical Properties ◽  
Planet Formation ◽  
Frictional Heating ◽  
Protoplanetary Disk ◽  
Small Bodies ◽  
Early Stages ◽  
Break Up ◽  
Solid Bodies ◽  
Stellar Source

AbstractDuring the early stages of planet formation accretion of small bodies add mass to the planet and deposit their energy kinetic energy. Caused by frictional heating and/or large stagnation pressures within the dense and extended atmospheres most of the in-falling bodies get destroyed by melting or break-up before they impact on the planet’s surface. The energy is added to the atmospheric layers rather than heating the planet directly. These processes can significantly alter the physical properties of protoplanets before they are exposed with their primordial atmospheres to the early stellar source when the protoplanetary disk becomes evaporated.

scholarly journals A Model for R Aqr from HST

1992 ◽  
Vol 151 ◽  
pp. 425-428
Author(s):  
Denis Burgarella ◽  
Manfred Vogel ◽  
Francesco Paresce
Keyword(s):  
Mass Transfer ◽  
Binary System ◽  
High Spatial Resolution ◽  
Ambient Medium ◽  
Spherically Symmetric ◽  
Symbiotic Star ◽  
Radiative Shock ◽  
Giant Star ◽  
The Core ◽  
Stellar Source

High spatial resolution observations R Aqr have been carried out with the HST/FOC. R Aqr is the nearest symbiotic star, i.e. an interacting system consisting of a cool giant star and a hot ionizing source embedded in a larger and complex nebula. We suggest, here, that the binary system is composed of a Mira and a hot stellar source with a radiation temperature of T* ≈ 40 000 K, a luminosity of L ≈ 10L⊙ and a radius R ≲ 0.1 R⊙. Mass transfer between the two components of the system occurs via capture of the Mira wind. Of the plausible mechanisms that may produce the R Aqr jet, an accretion/ejection scenario or the collision of winds seem to be unlikely, but spectral observations of the core are needed to conclude. Another possible origin is based on a spherically symmetric stellar wind that sweeps out a cavity in an ambient medium. This bubble elongates in the directions of least resistance, and matter eventually flows out through two symmetric nozzles. Comparison with models shows that the emission in the NE and SW outer features of the jets is due to a radiative shock but the pre-shock gas must be partially photoionized by the central hot stellar source.

scholarly journals Short-Lived Nuclei in the Early Solar System: A Low Mass Stellar Source?

2003 ◽  
Vol 20 (4) ◽  
pp. 356-370 ◽  
Author(s):  
M. Busso ◽  
R. Gallino ◽  
G. J. Wasserburg
Keyword(s):  
Solar System ◽  
Asymptotic Giant Branch ◽  
Early Solar System ◽  
Uncertainty Range ◽  
System A ◽  
Free Decay ◽  
Low Mass ◽  
Stellar Source ◽  
Review Current

AbstractWe discuss possible stellar origins of short-lived radioactive nuclei with meanlife τ ≤ 100 Myr, which were shown to be alive in the Early Solar System (ESS). We first review current ideas on the production of nuclides having 10 ≤ τ ≤ 100 Myr, which presumably derive from the continuous interplay of galactic astration, nucleosynthesis from massive supernovae and free decay in the interstellar medium. The abundance of the shorter lived 53Mn might be explained by this same scenario. Then we consider the nuclei 107Pd, 26Al, 41Ca and 60Fe, whose early solar system abundances are too high to have originated in this way. Present evidence favours a stellar origin, particularly for 107Pd, 26Al and 60Fe, rather than an in situ production by energetic solar particles. The idea of an encounter (rather close in time and space) between the forming Sun and a dying star is therefore discussed: this star may or may not have also triggered the solar formation. Recent nucleosynthesis calculations for the yields of the relevant short-lived isotopes and of their stable reference nuclei are discussed. Massive stars evolving to type II supernovae (either leaving a neutron star or a black hole as a remnant) seem incapable of explaining the four most critical ESS radioactivities in their observed abundance ratios. An asymptotic giant branch (AGB) star seems to be a viable source, especially if of relatively low initial mass (M ≤ 3 M⊙) and with low neutron exposure: this model can provide a solution for 26Al, 41Ca and 107Pd, with important contributions to 60Fe, which are inside the present uncertainty range of the 60Fe early solar system abundance. Such a model requires that 26Al is produced substantially on the AGB by cool bottom processing. The remaining inventory of short-lived species in the solar nebula would then be attributed to the continuous galactic processing, with the exception of 10Be, which must reflect production by later proton bombardment at a low level during early solar history.

ASCAObservations of “Type 2” LINERs: Evidence for a Stellar Source of Ionization

2000 ◽  
Vol 533 (2) ◽  
pp. 729-743 ◽  
Author(s):  
Yuichi Terashima ◽  
Luis C. Ho ◽  
Andrew F. Ptak ◽  
Richard F. Mushotzky ◽  
Peter J. Serlemitsos ◽  
...  
Keyword(s):  
Stellar Source

scholarly journals Energy distribution of Be stars

1994 ◽  
Vol 162 ◽  
pp. 422-424 ◽  
Author(s):  
Gopal C. Kilambi
Keyword(s):  
Far Infrared ◽  
Central Star ◽  
Infrared Region ◽  
Stellar Winds ◽  
Be Stars ◽  
Line Profiles ◽  
Spectrophotometric Data ◽  
Stellar Energy ◽  
Early Type Stars ◽  
Stellar Source

Be stars are defined to be non-supergiant early-type stars of spectral type B showing at times Balmer emission lines in their spectra. These stars often develop strong stellar winds considered to be variable in nature (Slettebak 1988) and have high rotational velocities compared to normal stars of similar spectral types. They also tend to show an excess amount of energy in the near- and far-infrared region compared to normal stars which is presumed to be due the surrounding material around the central star. Thus, the observed energy is a combination of that due to the stellar source and the surrounding material. Various attempts have been made to disentangle the stellar energy component from that of the circumstellar component in order to understand the nature, size and temperature of the envelope. These include:a) Radius determination based on IR excess (Gehrz et al. 1974, Dachs and Hanuschik 1984; Waters et al. 1987),b) Radius estimates from polarization and spectrophotometric data (Jones 1979),c) Envelope dimensions derived from the width of shell absorption cores (Kogure 1969; Hirata and Kogure 1977),d) Dachs et al. (1992) attempted to understand the physical properties, flow patterns and density distribution of the gas by a comparison of synthetic emission line profiles and empirical profiles measured for real Be stars.

A stellar source of lithium is caught in the act

Physics Today ◽  
2015 ◽  
Vol 68 (5) ◽  
pp. 16-17
Author(s):  
Johanna L. Miller
Keyword(s):  
Stellar Source

Quasi-Stellar Source, 3C 273 B: Variability in Radio Emission

Science ◽  
1965 ◽  
Vol 150 (3692) ◽  
pp. 78-79
Author(s):  
George B. Field
Keyword(s):  
Radio Emission ◽  
Stellar Source

scholarly journals Uniqueness and evolutionary status of MWC 349A

2010 ◽  
Vol 6 (S272) ◽  
pp. 632-633
Author(s):  
Vladimir Strelnitski ◽  
Kamber Schwarz ◽  
John Bieging ◽  
Josh T. Fuchs ◽  
Gary Walker
Keyword(s):  
Observational Data ◽  
High Gain ◽  
Radio Continuum ◽  
Circumstellar Disk ◽  
Evolutionary Status ◽  
Hydrogen Recombination ◽  
Protoplanetary Nebula ◽  
Ordinary Member ◽  
Stellar Source

AbstractMWC349A, which had remained an ordinary member of the MWC catalog for a few decades, is now known as: (1) the brightest stellar source of radio continuum; (2) the only known high-gain natural maser in hydrogen recombination lines; and (3) the only strictly proven natural high-gain laser (in IR hydrogen recombination lines). These phenomena seem to occur in the circumstellar disk seen almost edge-on. They help us understand the structure and kinematics of the disk. The evolutionary status of MWC 349A is still debated: a young HAeBe star with a pre-planetary disk or an old B[e] star or even a protoplanetary nebula? We discuss new observational data obtained at the Maria Mitchell Observatory and elsewhere which may cast light on this issue.

Quasi-Stellar Source, 3C 273 B: Variability in Radio Emission

Science ◽  
1965 ◽  
Vol 150 (3692) ◽  
pp. 78-79 ◽  
Author(s):  
G. B. Field
Keyword(s):  
Radio Emission ◽  
Stellar Source
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