scholarly journals The transiting dust clumps in the evolved disc of the Sun-like UXor RZ Psc

2017 ◽  
Vol 4 (1) ◽  
pp. 160652 ◽  
Author(s):  
Grant M. Kennedy ◽  
Matthew A. Kenworthy ◽  
Joshua Pepper ◽  
Joseph E. Rodriguez ◽  
Robert J. Siverd ◽  
...  
Keyword(s):  
Light Curve ◽  
Optical Depth ◽  
Variable Stars ◽  
Circumstantial Evidence ◽  
Asteroid Belt ◽  
Evolutionary Status ◽  
The Sun ◽  
Infrared Excess ◽  
Optical Photometry ◽  
Rz Psc

RZ Psc is a young Sun-like star, long associated with the UXor class of variable stars, which is partially or wholly dimmed by dust clumps several times each year. The system has a bright and variable infrared excess, which has been interpreted as evidence that the dimming events are the passage of asteroidal fragments in front of the host star. Here, we present a decade of optical photometry of RZ Psc and take a critical look at the asteroid belt interpretation. We show that the distribution of light curve gradients is non-uniform for deep events, which we interpret as possible evidence for an asteroidal fragment-like clump structure. However, the clumps are very likely seen above a high optical depth midplane, so the disc’s bulk clumpiness is not revealed. While circumstantial evidence suggests an asteroid belt is more plausible than a gas-rich transition disc, the evolutionary status remains uncertain. We suggest that the rarity of Sun-like stars showing disc-related variability may arise because (i) any accretion streams are transparent and/or (ii) turbulence above the inner rim is normally shadowed by a flared outer disc.

scholarly journals New mercury-manganese stars and candidates from LAMOST DR4

2021 ◽  
Vol 645 ◽  
pp. A34
Author(s):  
E. Paunzen ◽  
S. Hümmerich ◽  
K. Bernhard
Keyword(s):  
Main Sequence ◽  
Variable Stars ◽  
Evolutionary Status ◽  
The Sun ◽  
Early Type ◽  
Rotational Modulation ◽  
Bona Fide ◽  
Statistical Studies ◽  
Age Range ◽  
Age Estimates

Aims. The present work presents our efforts at identifying new mercury-manganese (HgMn/CP3) stars using spectra obtained with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST). Methods. Suitable candidates were searched for among pre-selected early-type spectra from LAMOST DR4 using a modified version of the MKCLASS code that probes several Hg II and Mn II features. The spectra of the resulting 332 candidates were visually inspected. Using parallax data and photometry from Gaia DR2, we investigated magnitudes, distances from the Sun, and the evolutionary status of our sample stars. We also searched for variable stars using diverse photometric survey sources. Results. We present 99 bona fide CP3 stars, 19 good CP3 star candidates, and seven candidates. Our sample consists of mostly new discoveries and contains, on average, the faintest CP3 stars known (peak distribution 9.5 ≤ G ≤ 13.5 mag). All stars are contained within the narrow spectral temperature-type range from B6 to B9.5, in excellent agreement with the expectations and the derived mass estimates (2.4 ≤ M⊙ ≤ 4 for most objects). Our sample stars are between 100 Myr and 500 Myr old and cover the whole age range from zero-age to terminal-age main sequence. They are almost homogeneously distributed at fractional ages on the main sequence ≤80%, with an apparent accumulation of objects between fractional ages of 50% to 80%. We find a significant impact of binarity on the mass and age estimates. Eight photometric variables were discovered, most of which show monoperiodic variability in agreement with rotational modulation. Conclusions. Together with the recently published catalogue of APOGEE CP3 stars, our work significantly increases the sample size of known Galactic CP3 stars, paving the way for future in-depth statistical studies.

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

Ultralong-period Cepheids: a possible primary distance indicator?

2012 ◽  
Vol 8 (S289) ◽  
pp. 282-286 ◽  
Author(s):  
G. Fiorentino ◽  
F. Annibali ◽  
G. Clementini ◽  
R. Contreras Ramos ◽  
M. Marconi ◽  
...  
Keyword(s):  
Spiral Galaxies ◽  
Hubble Space Telescope ◽  
Hubble Constant ◽  
Variable Stars ◽  
Evolutionary Status ◽  
Stellar Systems ◽  
Classical Cepheids ◽  
Type Ia ◽  
Distance Indicator ◽  
Crucial Test

AbstractWe present a project that aims to provide a complete theoretical and observational framework for an as yet unexplored class of variable stars, the ultralong-period Cepheids (P longer than 80–100 days). Given their very high luminosities (MV up to −7 mag), with the Hubble Space Telescope we will be able to observe them easily in stellar systems located at large distances (~ 100 Mpc). This limit will be further increased, out to the Hubble flow (~ 350 Mpc), using future ground-based facilities such as the European Extremely Large Telescope. The nature of their pulsation is as yet unclear, as is their evolutionary status, which seems different from the central helium-burning phase generally associated with classical Cepheids. These objects have been found to cover a very large metallicity range, from [Fe/H] ~ −2 dex to solar values, and they are located in heterogeneous stellar systems, from dwarf to spiral galaxies. Once completely characterized, they could provide a crucial test, since they have been found in all Type Ia supernova host spiral galaxies that have been monitored for variability over long periods and that currently offer sound constraints on the estimated value of the Hubble constant.

scholarly journals The Principle of Least Interaction Action

1974 ◽  
Vol 3 ◽  
pp. 489-489
Author(s):  
M. W. Ovenden
Keyword(s):  
Solar System ◽  
Planetary System ◽  
Satellite System ◽  
Asteroid Belt ◽  
Correct Prediction ◽  
The Sun ◽  
Approximate Methods ◽  
Satellites Of Jupiter ◽  
History Of ◽  
Minimum Interaction

AbstractThe intuitive notion that a satellite system will change its configuration rapidly when the satellites come close together, and slowly when they are far apart, is generalized to ‘The Principle of Least Interaction Action’, viz. that such a system will most often be found in a configuration for which the time-mean of the action associated with the mutual interaction of the satellites is a minimum. The principle has been confirmed by numerical integration of simulated systems with large relative masses. The principle lead to the correct prediction of the preference, in the solar system, for nearly-commensurable periods. Approximate methods for calculating the evolution of an actual satellite system over periods ˜ 109 yr show that the satellite system of Uranus, the five major satellites of Jupiter, and the five planets of Barnard’s star recently discovered, are all found very close to their respective minimum interaction distributions. Applied to the planetary system of the Sun, the principle requires that there was once a planet of mass ˜ 90 Mθ in the asteroid belt, which ‘disappeared’ relatively recently in the history of the solar system.

scholarly journals Hydrodynamic Models of Solar and Stellar Flares

1989 ◽  
Vol 104 (1) ◽  
pp. 289-298
Author(s):  
Giovanni Peres
Keyword(s):  
High Resolution ◽  
Light Curve ◽  
Solar Flares ◽  
Impulsive Phase ◽  
Light Curves ◽  
Physical Parameters ◽  
The Sun ◽  
Hydrodynamic Models ◽  
X Ray ◽  
Stellar Flares

AbstractThis paper discusses the hydrodynamic modeling of flaring plasma confined in magnetic loops and its objectives within the broader scope of flare physics. In particular, the Palermo-Harvard model is discussed along with its applications to the detailed fitting of X-ray light curves of solar flares and to the simulation of high-resolution Caxix spectra in the impulsive phase. These two approaches provide complementary constraints on the relevant features of solar flares. The extension to the stellar case, with the fitting of the light curve of an X-ray flare which occurred on Proxima Centauri, demonstrates the feasibility of using this kind of model for stars too. Although the stellar observations do not provide the wealth of details available for the Sun, and, therefore, constrain the model more loosely, there are strong motivations to pursue this line of research: the wider range of physical parameters in stellar flares and the possibility of studying further the solar-stellar connection.

Simultaneous infrared and optical photometry of the Eclipsing Dwarf Nova V2051 Ophiuchi

1986 ◽  
Vol 6 (3) ◽  
pp. 306-308 ◽  
Author(s):  
D. J. Watts ◽  
R. D. Watson
Keyword(s):  
Light Curve ◽  
Optical Photometry ◽  
Dwarf Nova

AbstractA complete orbital light-curve of V2051 Oph in the IR H band is presented, together with a second eclipse in the J band. Simultaneous Rc band data were obtained. Eclipse depths in Rc, J and H are 1.8 mag, 1.0 mag and 0.8 mag respectively. No evidence for ellipsoidal variations due to the secondary was seen and constraints on the secondary are discussed.

Light Curve Analysis and Evolutionary Status of the RS CVn type Eclipsing Binary RZ Eridani

Algols ◽  
1989 ◽  
pp. 357-357
Author(s):  
P. Vivekananda Rao ◽  
B. V. N. S. Prakash Rao ◽  
M. B. K. Sarma
Keyword(s):  
Light Curve ◽  
Curve Analysis ◽  
Evolutionary Status ◽  
Light Curve Analysis ◽  
Eclipsing Binary

scholarly journals The Hyper Suprime-Cam SSP transient survey in COSMOS: Overview

2019 ◽  
Vol 71 (4) ◽  
Author(s):  
Naoki Yasuda ◽  
Masaomi Tanaka ◽  
Nozomu Tominaga ◽  
Ji-an Jiang ◽  
Takashi J Moriya ◽  
...  
Keyword(s):  
Light Curve ◽  
Deep Layer ◽  
High Redshift ◽  
Galactic Nuclei ◽  
Variable Stars ◽  
Photometric Redshifts ◽  
Data Set ◽  
Type Ia ◽  
Strategic Program ◽  
Ia Supernovae

Abstract We present an overview of a deep transient survey of the COSMOS field with the Subaru Hyper Suprime-Cam (HSC). The survey was performed for the 1.77 deg2 ultra-deep layer and 5.78 deg2 deep layer in the Subaru Strategic Program over six- and four-month periods from 2016 to 2017, respectively. The ultra-deep layer reaches a median depth per epoch of 26.4, 26.3, 26.0, 25.6, and 24.6 mag in g, r, i, z, and y bands, respectively; the deep layer is ∼0.6 mag shallower. In total, 1824 supernova candidates were identified. Based on light-curve fitting and derived light-curve shape parameter, we classified 433 objects as Type Ia supernovae (SNe); among these candidates, 129 objects have spectroscopic or COSMOS2015 photometric redshifts and 58 objects are located at z > 1. Our unique data set doubles the number of Type Ia SNe at z > 1 and enables various time-domain analyses of Type II SNe, high-redshift superluminous SNe, variable stars, and active galactic nuclei.

2.1.8 Sources of Interplanetary Dust: Asteroids

1976 ◽  
Vol 31 ◽  
pp. 187-205 ◽  
Author(s):  
J. S. Dohnanyi
Keyword(s):  
Interplanetary Dust ◽  
Asteroid Belt ◽  
The Sun ◽  
Number Density ◽  
Zodiacal Cloud ◽  
Relative Contribution ◽  
Potential Source ◽  
Asteroidal Belt ◽  
Pioneer 10

AbstractThe asteroid belt is examined as a potential source of interplanetary dust. Using results from the Pioneer-10 experiments the relative contribution of asteroidal and cometary particles to the Zodiacal cloud is estimated using methods developed in earlier studies of meteoroidal collisions (collisional model). It is found that the contribution of asteroidal particles to dust in the asteroidal belt is small compared with the number density of cometary type particles. Similar conclusions apply to the Zodiacal cloud between the sun and the asteroid belt. When definitive criteria for differentiating between comets and asteroids become available, a reexamination of some of our conclusions may become necessary.The distribution of asteroidal rotations is analyzed; it is found that the gross features of the distribution can be reproduced using the collisional model.

Sign in / Sign up

Export Citation Format

Share Document