scholarly journals Photometry of R Coronae Borealis Stars during the Recovery Phase of their Declines

2003 ◽  
Vol 20 (2) ◽  
pp. 159-164 ◽  
Author(s):  
Lj. Skuljan ◽  
P. L. Cottrell ◽  
A. C. Gilmore ◽  
P. M. Kilmartin
Keyword(s):  
New Zealand ◽  
Interstellar Dust ◽  
Dust Cloud ◽  
Recovery Phase ◽  
Asymptotic Approach ◽  
Maximum Brightness ◽  
Photometric Observations ◽  
R Coronae Borealis Stars ◽  
Selective Extinction

AbstractThe photometric observations (UBVRI) of nine cool R Coronae Borealis (RCB) stars have been collected at Mt John University Observatory, New Zealand, over a period of twelve years. The analysis of the magnitude–colour and colour–colour diagrams for the recovery phase demonstrates that all declines exhibit a similar asymptotic approach to their normal brightness. Declines return to maximum brightness along a line with essentially the same slope that does not depend on the star or the depth of the decline. Assuming a uniform obscuration of the photosphere by the dust cloud during the recovery phase, the extinction properties of the material were determined. The ratio of total to selective extinction (RV) for the RCB stars in our sample is in the range 2.5 to 4.6, indicating that the obscuring dust has extinction properties similar to that of the interstellar dust. Observations have been compared with the theoretical extinction curves for different sorts of grains.

scholarly journals Photometry of R Coronae Borealis Stars during the Recovery Phases of Their Declines

2000 ◽  
Vol 176 ◽  
pp. 113-113
Author(s):  
Ljiljana Skuljan ◽  
Peter L. Cottrell
Keyword(s):  
Interstellar Dust ◽  
Large Scale ◽  
Laboratory Data ◽  
Recovery Phase ◽  
Variable Stars ◽  
Maximum Brightness ◽  
Photometric Observations ◽  
Rare Class ◽  
Acceptable Theory

AbstractR Coronae Borealis (RCB) stars are a rare class of variable stars, well-known by their declines, but still posing two fundamental questions: what is the origin and what is the nature of their unpredictable minima? Possible contributions to the answering of these questions could use large-scale surveys, by discovering new RCB stars. In addition, photometric databases from these surveys and other long-term photometric programs of targeted stars can be used to compile information about these decline phases.The photometric observations (UBVRI) of nine cool RCB stars have been collected at Mt John University Observatory, New Zealand, for the last ten years. Analysis of the magnitude–color diagrams for the recovery phase of a number of declines of these stars has been made in order to determine the extinction properties of the dust. The photometric magnitudes and colors show significant changes during the RCB declines. The asymptotic approach to the normal brightness can be seen on the magnitude–color diagrams from the recovery phase. This is observed for all RCB declines, and without exception is independent of their decline amplitude. According to the most acceptable theory, the distribution of the dust matter in the cloud which causes the light fading can be considered uniform as the stars recover to the maximum brightness. The slopes of the magnitude–color and color–color diagrams from the recovery phase of 26 observed RCB declines have been used in order to define the normalized extinction quantity Aλ/AV. Although the extinction curve in the UBVRI region is not a good indicator of the type and size of the particles, our data show that the material causing the RCB declines has extinction properties similar to that for the interstellar medium. The reddening parameter (RBV = AV/E(B – V)) for the RCB stars in our sample is in the range 2.5 to 4.6, similar to the interstellar dust. Observations have been compared with the theoretical extinction curves for different sorts of grains. The extinction properties in the U region follow the trend of the UV data from other RCB observations as well as laboratory data for amorphous carbon.

scholarly journals Polarization of Light by Dust in Galaxies

1973 ◽  
Vol 52 ◽  
pp. 209-212
Author(s):  
Aina Elvius
Keyword(s):  
Interstellar Dust ◽  
Scattering Of Light ◽  
Preliminary Results ◽  
Polarization Of Light ◽  
Selective Extinction

Several galaxies were observed for polarization during April and May 1972. Preliminary results are presented concerning those galaxies where polarization can be expected because of selective extinction or scattering of light by interstellar dust.

scholarly journals A photometric and spectroscopic study of R Coronae Borealis stars in the LMC

1991 ◽  
Vol 148 ◽  
pp. 351-352
Author(s):  
W. A. Lawson ◽  
P. L. Cottrell ◽  
K. R. Pollard
Keyword(s):  
High Resolution ◽  
Spectroscopic Study ◽  
Large Magellanic Cloud ◽  
Magellanic Cloud ◽  
Light Curves ◽  
Photometric Observations ◽  
R Coronae Borealis Stars

Over the last several years we have obtained photometric observations of the four suspected (W Men, HV 5637, HV 12671, HV 12842) R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC). Fourier analyses of the light curves has revealed some periodicity in HV 12842, where there appear to be at least two closely spaced periods of 55 and 60 d. High resolution spectra of HV 12842, obtained with the Ango-Australian Telescope (AAT), indicate that it has similar atmospheric properties to a number of warmer galactic RCB and hydrogen-deficient Carbon (HdC) stars, e.g. R CrB, RY Sgr and XX Cam.

Destiny+ Dust Analyzer – Campaign & timeline preparation for interplanetary & interstellar dust observation during the 4-year transfer phase from Earth to Phaethon

2020 ◽  
Author(s):  
Maximilian Sommer ◽  
Harald Krüger ◽  
Ralf Srama ◽  
Takayuki Hirai ◽  
Masanori Kobayashi ◽  
...  
Keyword(s):  
Electric Propulsion ◽  
Interstellar Dust ◽  
Impact Ionization ◽  
Interplanetary Space ◽  
Dust Cloud ◽  
Dust Particles ◽  
Transfer Phase ◽  
Moon System ◽  
The Earth ◽  
The Impact

<p align="justify">The Destiny+ mission (Demonstration and Experiment of Space Technology for Interplanetary voyage Phaethon fLyby and dUst Science) has been selected as part of its M-class Space Science Program by the Japanese space agency JAXA/ISAS and is set to launch in 2023/2024. The mission target is the active asteroid (3200) Phaethon with a projected flyby in early 2028. The scientific payload consists of two cameras (the Telescopic Camera for Phaethon, TCAP, and the Multi-band Camera for Phaethon, MCAP), and the Destiny+ Dust Analyzer (DDA). DDA is the technological successor to the Cosmic Dust Analyzer (CDA) aboard Cassini-Huygens, which prominently investigated the dust environment of the Saturnian system. The DDA sensor is designed as a combination of impact ionization time-of-flight mass spectrometer and trajectory sensor, which will allow for the analysis of sub-micron and micron sized dust particles with respect to their composition (mass resolution m/Δm ≈ 100-150), mass, electrical charge, velocity (about 10% accuracy), and impact direction (about 10° accuracy).</p> <p align="justify">Besides attempting to sample the impact-generated dust cloud around Phaethon during the flyby, DDA will be actively observing the interplanetary & interstellar dust environment over the roughly four years spanning cruise phase from the Earth-Moon system through interplanetary space. After launch into a GTO-like orbit, Destiny+ will first employ its solar-electric propulsion system to spiral up to the lunar orbit within about 18 months, followed by a series of lunar swingbys and interim coasting phases in distant cislunar space, accumulating momentum to leave the Earth-Moon system at high excess velocity. The subsequent roughly 2-year interplanetary transfer to intercept Phaethon will be characterized by moderate orbital eccentricity of up to 0.1 and largely unpowered coasting phases.</p> <p align="justify">During these four years, the DDA sensor will benefit from a maximum pointing coverage range enabled by its dual-axis pointing mechanism and spacecraft attitude flexibility (during times of unpowered flight). This will allow for exhaustive mapping and analysis of the different interplanetary dust populations, as well as interstellar dust encountered in the region between 0.9-1.1 AU.</p> <p align="justify">Here, we give a progress report on the science planning efforts for the 4-year transfer phase. We present a tentative observation timeline that assigns scientific campaigns to different phases of the mission, taking into account results of various dust models, as well as operational and technical constraints.</p>

scholarly journals Models of Reflection Nebulae

1965 ◽  
Vol 7 ◽  
pp. 111-121
Author(s):  
T. P. Roark ◽  
J. Mayo Greenberg
Keyword(s):  
Optical Properties ◽  
Simple Model ◽  
Electromagnetic Scattering ◽  
Interstellar Dust ◽  
Radial Direction ◽  
Dust Cloud ◽  
Mie Theory ◽  
Color Differences ◽  
Reflection Nebulae ◽  
Observational Program

A Feasibility Study For an Observational Program was made to investigate models of reflection nebulae. Specifically, for a relatively simple model of an interstellar dust cloud with a source of illumination nearby, predictions of the color of the nebula, relative to the source color, at points along any radial direction from the source are sought. Furthermore, from these color differences, the possibility is studied of discriminating between the effects produced by the cloud-source-observer geometry and those due to the assumed optical properties of the scattering particles. If such discrimination is feasible, the types of observations that would be most useful in separating the effects must be known to the investigator.Plane-parallel slab models similar to those of reference 1 in which the scattering particles are distributed isotropically and homogeneously were used. The scattering properties of the particles were assumed to be those obtained by using the Mie theory of electromagnetic scattering.

scholarly journals The Influence of the Ratio of Total to Selective Extinction on the Determination of the Mass Loss Rate of Wolf Rayet Stars from Infrared Excess Measurements

1982 ◽  
Vol 99 ◽  
pp. 197-201
Author(s):  
P.S. The ◽  
K.A. van der Hucht ◽  
M. Arens
Keyword(s):  
Mass Loss ◽  
Loss Rate ◽  
Near Infrared ◽  
Mass Loss Rate ◽  
Infrared Excess ◽  
Photometric Observations ◽  
Order Of Magnitude ◽  
Selective Extinction ◽  
Loss Rates

It is shown that the mass loss rate of the WN7 star HD 93162 decreases with larger values of the ratio of total to selective extinction R. for HD 93162 the mass loss rate will change one order of magnitude, only if ΔR ∼ 2. Mass loss rates are derived for nine other WR stars of which visual, red and near-infrared photometric observations were obtained.

scholarly journals Physical Modeling of the Zodiacal Dust Cloud

2001 ◽  
Vol 204 ◽  
pp. 17-34 ◽  
Author(s):  
Leonid M. Ozernoy
Keyword(s):  
Solar System ◽  
Physical Modeling ◽  
Interstellar Dust ◽  
Extrasolar Planets ◽  
Dust Cloud ◽  
Interplanetary Dust ◽  
Asteroid Belt ◽  
Dust Particles ◽  
Resonant Structure ◽  
Zodiacal Light

This review is based on extensive work done in collaboration with N. Gorkavyi, J. Mather, and T. Taidakova, which aimed at physical modeling of the interplanetary dust (IPD) cloud in the Solar System, i.e., establishing a link between the observable characteristics of the zodiacal cloud and the dynamical and physical properties of the parent minor bodies. Our computational approach permits one to integrate the trajectories of hundreds of particles and to effectively store up to 1010–11 positions with modest computer resources, providing a high fidelity 3D distribution of the dust. Our numerical codes account for the major dynamical effects that govern the motion of IPD particles: Poynting-Robertson (P-R) drag and solar wind drag; solar radiation pressure; particle evaporation; gravitational scattering by the planets; and the influence of mean-motion resonances. The incorporation of secular resonances and collisions of dust particles (both mutual and with interstellar dust) is underway. We have demonstrated the efficacy of our codes by performing the following analyses: (i) simulation of the distribution of Centaurs (comets scattered in their journey from the Kuiper belt inward in the Solar System) and revealing the effects of the outer planets in producing ‘cometary belts’; (ii) detailed inspection of a rich resonant structure found in these belts, which predicts the existence of gaps similar to the Kirkwood gaps in the main asteroid belt; (iii) a preliminary 3-D physical model of the IPD cloud, which includes three dust components – asteroidal, cometary, and kuiperoidal – and is consistent with the available data of Pioneer and Voyager dust detectors; (iv) modeling of the IPD cloud, which provides a zodiacal light distribution in accord, to the order of 1%, with a subset of the COBE/DIRBE observations; and (v) showing that the resonant structure in dusty circumstellar disks of Vega and Epsilon Eridani is a signature of embedded extrasolar planets. Further improvements of our modeling and their importance for astronomy and cosmology are outlined.

scholarly journals The New Zealand Experience of a Design-Led Approach to Post-Earthquake Recovery in Christchurch

2020 ◽  
Vol 3 (3) ◽  
pp. p89
Author(s):  
Diane Brand ◽  
Natalie Allen ◽  
Greer O’Donnell
Keyword(s):  
New Zealand ◽  
Community Engagement ◽  
Recovery Phase ◽  
Top Down ◽  
Recovery Approach ◽  
Green City

This paper evaluates the masterplan for Christchurch which was conceived in the wake of the 2011 earthquakes, against projects completed in the intervening 8 years, paying special attention to three key objectives of the blueprint: a low-rise/compact core, a green city, and an accessible city. The paper finds that the design-led, top down, recovery approach forms a minimal framework for recovery, and that successful regeneration following the recovery phase will require significant community engagement and coherent governance.

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