scholarly journals Multiperiodicity, modulations and flip-flops in variable star light curves

2011 ◽  
Vol 535 ◽  
pp. A23 ◽  
Author(s):  
J. Pelt ◽  
N. Olspert ◽  
M. J. Mantere ◽  
I. Tuominen
Keyword(s):  
Variable Star ◽  
Light Curves

scholarly journals Analyzing Light Curves for Variable Star Classification

2020 ◽  
Author(s):  
Melinda Soares Furtado ◽  
Christopher Moore ◽  
Rachel McClure
Keyword(s):  
Variable Star ◽  
Light Curves ◽  
Star Classification

scholarly journals A Catalogue of Ultraviolet Observations of Chromospherically Active Binary Stars

1996 ◽  
Vol 152 ◽  
pp. 183-184
Author(s):  
C. La Dous ◽  
Alvaro Giménez
Keyword(s):  
Binary Stars ◽  
Variable Star ◽  
Ultraviolet Spectrum ◽  
Light Curves ◽  
Background Information ◽  
Low Resolution ◽  
Physical Information ◽  
The Individual ◽  
Ultraviolet Observations ◽  
Provide Background Information

We present the recently-published IUE-ULDA Access Guide on Chromospherically Active Binary Stars which should be of interest for the interpretation and analysis of EU V data obtained for this type of objects. We provide background information on both high and low resolution IUE spectra of chromospherically active late-type binary stars that have been taken until the end of 1992. Physical information on all systems, arranged by variable star name, together with characteristics of the individual exposures, the position of the observation in the orbital light curves, and an average low resolution ultraviolet spectrum are given.

scholarly journals Towards a 1% measurement of the Hubble constant: accounting for time dilation in variable-star light curves

2019 ◽  
Vol 631 ◽  
pp. A165
Author(s):  
Richard I. Anderson
Keyword(s):  
Variable Star ◽  
Hubble Constant ◽  
Light Curves ◽  
Type Ia Supernovae ◽  
Host Galaxies ◽  
Pulsating Stars ◽  
Distant Galaxies ◽  
Type Ia ◽  
Absolute Magnitudes ◽  
Ia Supernovae

Assessing the significance and implications of the recently established Hubble tension requires the comprehensive identification, quantification, and mitigation of uncertainties and/or biases affecting H0 measurements. Here, we investigate the previously overlooked distance scale bias resulting from the interplay between redshift and Leavitt laws in an expanding Universe: Redshift-Leavitt bias (RLB). Redshift dilates oscillation periods of pulsating stars residing in supernova-host galaxies relative to periods of identical stars residing in nearby (anchor) galaxies. Multiplying dilated log P with Leavitt Law slopes leads to underestimated absolute magnitudes, overestimated distance moduli, and a systematic error on H0. Emulating the SH0ES distance ladder, we estimate an associated H0 bias of (0.27 ± 0.01)% and obtain a corrected H0 = 73.70 ± 1.40 km s−1 Mpc−1. RLB becomes increasingly relevant as distance ladder calibrations pursue greater numbers of ever more distant galaxies hosting both Cepheids (or Miras) and type-Ia supernovae. The measured periods of oscillating stars can readily be corrected for heliocentric redshift (e.g. of their host galaxies) in order to ensure H0 measurements free of RLB.

The Ultraviolet Variations of ι Cas

1976 ◽  
Vol 32 ◽  
pp. 589-602
Author(s):  
M.R. Molnar ◽  
A.D. Mallama ◽  
D.G. Soskey ◽  
A.V. Holm
Keyword(s):  
Ultraviolet Light ◽  
Variable Star ◽  
Great Circle ◽  
Light Curves ◽  
Primary Minimum ◽  
Axis Of Rotation ◽  
Rotator Model ◽  
Oblique Rotator ◽  
Magnetic Dipole Field ◽  
Ap Stars

SummaryThe Ap variable star ι Cas was observed with the photometers on OAO-2 covering the spectral range λλ 1430-4250. The ultraviolet light curves show a double wave with primary minimum and maximum at ϕ = 0.00 and 0.35, respectively. Secondary minimum light is at ϕ = 0.65 with secondary maximum at ϕ = 0.85. The light curves longward of λ3150 vary in opposition to those shortward of this “null region”.Ground-based coude spectra show that the Fe II and Cr II line strengths have a double-wave variation such that maximum strength occurs at minimum ultraviolet light. We suggest that the strong ultraviolet opacities due to photoionization and line blanketing by these metals may cause the observed photometric variations.We have also constructed an oblique-rotator model which shows iron and chromium lying in a great circle band rather than in circular spots. These elements have been observed to lie in bands along the magnetic equator in several other Ap stars such as α2CVn, HD 173650, and 108 Aqr. Thus, we predict that the inclination of the magnetic dipole field with respect to the axis of rotation is about 84°.

Flexible Variable Star Extractor - new software for variable stars detection using CCD photometry

2017 ◽  
Vol 7 (1-2) ◽  
pp. 3-5
Author(s):  
V. Breus
Keyword(s):  
Time Series ◽  
Computer Program ◽  
Variable Star ◽  
Variable Stars ◽  
Light Curves ◽  
Multiple Comparison ◽  
Ccd Photometry ◽  
Comparison Stars ◽  
The Impact ◽  
Outlying Point

We developed a computer program for variable stars detection using CCD photometry. It works with "varfind data" that could be exported after processing CCD frames using C-Munipack. The program chooses the comparison stars automatically, processes all time series using multiple comparison stars to get final light curves. We developed few filters and criteria that allow reducing the impact of outlying points, imaging artefacts and low quality CCD frames without careful manual time series reduction. We implemented the calculation of various variable detection indices. The pipeline has a possibility of plotting a two-channel diagram of selected pair of indices or mean brightness of the star for manual check if any outlying point is a variable candidate. The program is available at http://uavso.org.ua/varsearch/.

scholarly journals Multiperiodicity, modulations and flip-flops in variable star light curves

2013 ◽  
Vol 559 ◽  
pp. A97 ◽  
Author(s):  
M. Lindborg ◽  
M. J. Mantere ◽  
N. Olspert ◽  
J. Pelt ◽  
T. Hackman ◽  
...  
Keyword(s):  
Variable Star ◽  
Light Curves

scholarly journals Hydrodynamic Models of Low-Mass Pulsating Supergiants with Radiative Transfer

1989 ◽  
Vol 111 ◽  
pp. 264-264
Author(s):  
A.B. Foken
Keyword(s):  
Radiative Transfer ◽  
Variable Star ◽  
Stable Limit Cycle ◽  
Light Curves ◽  
Transfer Model ◽  
Stable Limit ◽  
Type Ii ◽  
Hydrodynamic Models ◽  
Stellar Pulsations ◽  
Low Mass

AbstractA method of calculating nonlinear stellar pulsations including nonstationary radiative transfer in a grey spherical atmosphere is described. With the help of this method eleven type II supergiant radiative models were constructed with masses of 0.6M⊙, luminosities ranging from 128L⊙ to 3123L⊙ and periods in the range from 1.123 to 46 days. A stable limit cycle was found to be accessible only by models with an effective temperature between 5700K and 6165K. The model with Te = 6165K is stable, whereas the models cooler than 5700K show nonregular behavior. Transition from strictly periodic to nonregular pulsation arises when M/R ≲ 0.018, due to high amplitudes, δr/r ≈ 1, and strong shocks in the atmosphere. The radiative transfer effects lead to some decay in the radial amplitude, as well as to a more significant decrease, about 0.6 magnitudes, in the light variation. A photometric comparison between the light curves of the models calculated with and without transfer and the observed light curve of the variable star No. 154 in M3 shows that the results predicted by the transfer model are in much better agreement with obervational data.

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