scholarly journals Thermophysical Model for Realistic Surface Layers on Airless Small Bodies: Applied to Study the Spin Orientation and Surface Dust Properties of (24) Themis from WISE/NEOWISE Multiepoch Thermal Light Curves

2021 ◽  
Vol 913 (2) ◽  
pp. 96
Author(s):  
Liang-Liang Yu ◽  
Wing-Huen Ip
Keyword(s):  
Light Curves ◽  
Surface Layers ◽  
Spin Orientation ◽  
Small Bodies ◽  
Surface Dust ◽  
Thermophysical Model ◽  
Thermal Light

scholarly journals Secular and rotational light curves of 6478 Gault

2019 ◽  
Vol 490 (1) ◽  
pp. 219-230 ◽  
Author(s):  
Ignacio Ferrín ◽  
Cesar Fornari ◽  
Agustín Acosta
Keyword(s):  
Absolute Magnitude ◽  
Light Curves ◽  
Physical Parameters ◽  
Evolutionary Stage ◽  
Rotational Period ◽  
Main Belt ◽  
Phase Effect ◽  
Surface Dust ◽  
Show Evidence ◽  
Highly Evolved

ABSTRACT We obtained 877 images of active asteroid 6478 Gault on 41 nights from 2019 January 10 to June 8, using several telescopes. We created the phase, secular, and rotational light curves of Gault, from which several physical parameters can be derived. From the phase plot, we find that no phase effect was evident. This implies that an optically thick cloud of dust surrounded the nucleus hiding the surface. The secular light curve (SLC) shows several zones of activity, the origin of which is speculative. From the SLC plots, a robust absolute magnitude can be derived and we find mV (1,1,α) = 16.11 ± 0.05. We also found a rotational period Prot = 3.360 ± 0.005 h and show evidence that 6478 might be a binary. The parameters of the pair are derived. Previous works have concluded that 6478 is in a state of rotational disruption and the above rotational period supports this result. Our conclusion is that 6478 Gault is a suffocated comet getting rid of its suffocation by expelling surface dust into space using the centrifugal force. This is an evolutionary stage in the lifetime of some comets. Besides being a main-belt comet (MBC), the object is classified as a dormant Methuselah Lazarus, meaning Gault is both highly evolved and has a decaying perihelion distance.

scholarly journals Three-dimensional heat transfer effects in external layers of a magnetized neutron star

2020 ◽  
Vol 497 (3) ◽  
pp. 2883-2892
Author(s):  
Ilya A Kondratyev ◽  
Sergey G Moiseenko ◽  
Gennady S Bisnovatyi-Kogan ◽  
Maria V Glushikhina
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Thermal Conductivity ◽  
Neutron Star ◽  
Magnetic Fields ◽  
Three Dimensional ◽  
Light Curves ◽  
Quadrupole Component ◽  
Thermal Light ◽  
Quadrupole Magnetic Field

ABSTRACT Determination of a magnetic field structure on a neutron star (NS) surface is an important problem of a modern astrophysics. In a presence of strong magnetic fields, a thermal conductivity of a degenerate matter is anisotropic. In this paper, we present 3D anisotropic heat transfer simulations in outer layers of magnetized NSs, and construct synthetic thermal light curves. We have used a different from previous works tensorial thermal conductivity coefficient of electrons, derived from the analytical solution of the Boltzmann equation by the Chapman–Enskog method. We have obtained an NS surface temperature distribution in presence of dipole-plus-quadrupole magnetic fields. We consider a case, in which magnetic axes of a dipole and quadrupole components of the magnetic field are not aligned. To examine observational manifestations of such fields, we have generated thermal light curves for the obtained temperature distributions using a composite blackbody model. It is shown that the simplest (only zero-order spherical function in quadrupole component) non-coaxial dipole-plus-quadrupole magnetic field distribution can significantly affect the thermal light curves, making pulse profiles non-symmetric and amplifying pulsations in comparison to the pure-dipolar field.

Distance to SN 1987A and the LMC

1999 ◽  
Vol 190 ◽  
pp. 549-554
Author(s):  
Nino Panagia
Keyword(s):  
Angular Size ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Distance Modulus ◽  
Absolute Size ◽  
Sn 1987A

Using the new reductions of the IUE light curves by Sonneborn et al. (1997) and an extensive set of HST images of SN 1987A we have repeated and improved Panagia et al. (1991) analysis to obtain a better determination of the distance to the supernova. In this way we have derived an absolute size of the ringRabs= (6.23 ± 0.08) x 1017cm and an angular sizeR″ = 808 ± 17 mas, which give a distance to the supernovad(SN1987A) = 51.4 ± 1.2 kpc and a distance modulusm–M(SN1987A) = 18.55 ± 0.05. Allowing for a displacement of SN 1987A position relative to the LMC center, the distance to the barycenter of the Large Magellanic Cloud is also estimated to bed(LMC) = 52.0±1.3 kpc, which corresponds to a distance modulus ofm–M(LMC) = 18.58±0.05.

Quasi-Periodic Oscillations in Dwarf Novae

1979 ◽  
Vol 46 ◽  
pp. 77-88
Author(s):  
Edward L. Robinson
Keyword(s):  
Binary Systems ◽  
Outer Edge ◽  
Light Curves ◽  
Close Binary ◽  
Bright Spot ◽  
Dwarf Novae ◽  
Periodic Oscillations ◽  
High Frequencies ◽  
Short Period ◽  
Typical Time

Three distinct kinds of rapid variations have been detected in the light curves of dwarf novae: rapid flickering, short period coherent oscillations, and quasi-periodic oscillations. The rapid flickering is seen in the light curves of most, if not all, dwarf novae, and is especially apparent during minimum light between eruptions. The flickering has a typical time scale of a few minutes or less and a typical amplitude of about .1 mag. The flickering is completely random and unpredictable; the power spectrum of flickering shows only a slow decrease from low to high frequencies. The observations of U Gem by Warner and Nather (1971) showed conclusively that most of the flickering is produced by variations in the luminosity of the bright spot near the outer edge of the accretion disk around the white dwarf in these close binary systems.

The Eclipsing Binary WX Eridani

1979 ◽  
Vol 46 ◽  
pp. 385
Author(s):  
M.B.K. Sarma ◽  
K.D. Abhankar
Keyword(s):  
Light Curve ◽  
Spectral Type ◽  
Orbital Period ◽  
Primary Component ◽  
Light Curves ◽  
Absorption Feature ◽  
Primary Star ◽  
Eclipsing Binary ◽  
The Times ◽  
Phase Angles

AbstractThe Algol-type eclipsing binary WX Eridani was observed on 21 nights on the 48-inch telescope of the Japal-Rangapur Observatory during 1973-75 in B and V colours. An improved period of P = 0.82327038 days was obtained from the analysis of the times of five primary minima. An absorption feature between phase angles 50-80, 100-130, 230-260 and 280-310 was present in the light curves. The analysis of the light curves indicated the eclipses to be grazing with primary to be transit and secondary, an occultation. Elements derived from the solution of the light curve using Russel-Merrill method are given. From comparison of the fractional radii with Roche lobes, it is concluded that none of the components have filled their respective lobes but the primary star seems to be evolving. The spectral type of the primary component was estimated to be F3 and is found to be pulsating with two periods equal to one-fifth and one-sixth of the orbital period.

Comments on collision mechanics in ring systems

1984 ◽  
Vol 75 ◽  
pp. 407-422
Author(s):  
William K. Hartmann
Keyword(s):  
Asteroid Belt ◽  
Surface Erosion ◽  
Surface Layers ◽  
Ring Systems ◽  
Eclipse Observations ◽  
Saturn’S Rings ◽  
Saturn's Rings

ABSTRACTThe nature of collisions within ring systems is reviewed with emphasis on Saturn's rings. The particles may have coherent icy cores and less coherent granular or frosty surface layers, consistent with thermal eclipse observations. Present-day collisions of such ring particles do not cause catastrophic fragmentation of the particles, although some minor surface erosion and reaccretion is possible. Evolution by collisional fragmentation is thus not as important as in the asteroid belt.

Applications of Photoelectron Microscopy

1976 ◽  
Vol 34 ◽  
pp. 506-507
Author(s):  
William J. Baxter
Keyword(s):  
Electron Microscopy ◽  
Thermal Decomposition ◽  
Chemical Composition ◽  
Ultraviolet Radiation ◽  
Thin Layer ◽  
Edge Effects ◽  
Electron Optics ◽  
Surface Layers ◽  
Crystalline Orientation ◽  
Fluorescent Screen

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.

Etching of Polymers by Oxygen Plasma

1968 ◽  
Vol 26 ◽  
pp. 408-409
Author(s):  
Virgil Peck ◽  
W. L. Carter
Keyword(s):  
Molecular Weight ◽  
Oxygen Plasma ◽  
Flow Time ◽  
Microscopical Study ◽  
Surface Layers ◽  
Organic Vapors ◽  
Sample Position ◽  
Accuracy Of Measurement ◽  
Bulk Polymers ◽  
Electron Microscopical

Any electron microscopical study of the morphology of bulk polymers has throughout the years been hampered by the lack of any real ability to produce meaningful surface variations for replication. True etching of polymers should show crystalline and amorphous regions in some form of relief. The use of solvents, acids, organic vapors, and inert ion bombardment to etch samples has proved to be useful only in limited applications. Certainly many interpretations of these results are subject to question.The recent use of a radiofrequency (R. F.) plasma of oxygen to degrade and remove organic material with only minor heating has opened a new possibility for etching polymers. However, rigid control of oxygen flow, time, current, and sample position are necessary in order to obtain reproducible results. The action is confined to surface layers; the molecular weight of the polymer residue after heavy etching is the same as the molecular weight of the polymer before attack, within the accuracy of measurement.

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