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 The Variable Star Population in the Center of 47 Tuc as denned by HST Observations

1995 ◽  
Vol 155 ◽  
pp. 335-336
Author(s):  
Ronald L. Gilliland ◽  
Peter D. Edmonds ◽  
Larry Petro ◽  
Abhijit Saha ◽  
Michael Shara
Keyword(s):  
Time Series ◽  
Globular Clusters ◽  
Variable Star ◽  
High Spatial Resolution ◽  
Variable Stars ◽  
Light Curves ◽  
Dynamic Evolution ◽  
Limited Time ◽  
Blue Stragglers ◽  
Breeding Grounds

AbstractThe high stellar densities at the centre of some globular clusters provide prolific breeding grounds for exotic stars, e.g., the 11 msec pulsars in 47 Tuc and numerous blue stragglers. The same high density of stars as viewed on the sky makes ground-based photometry problematic for variable star detection. Even a very few tight binaries can be of fundamental importance for the dynamic evolution of the cluster core. We present results of a continuous 40-hour sequence of U-band CCD exposures acquired with WF/PC on HST. The high spatial resolution coupled with a stable PSF allows nearly Poisson limited time series on some 20,000 stars. The 1000 second sampling and long coverage provide excellent sensitivity to W UMa and δ Scuti variations. Light curves are shown for selected variables and the relative frequencies of binary and variable stars are discussed.

scholarly journals An autoregressive model for irregular time series of variable stars

2016 ◽  
Vol 12 (S325) ◽  
pp. 259-262
Author(s):  
Susana Eyheramendy ◽  
Felipe Elorrieta ◽  
Wilfredo Palma
Keyword(s):  
Time Series ◽  
Gravitational Lensing ◽  
Autoregressive Model ◽  
Likelihood Estimation ◽  
Estimation Procedure ◽  
Variable Stars ◽  
Light Curves ◽  
Finite Sample ◽  
Harmonic Model ◽  
Dependency Structure

AbstractThis paper discusses an autoregressive model for the analysis of irregularly observed time series. The properties of this model are studied and a maximum likelihood estimation procedure is proposed. The finite sample performance of this estimator is assessed by Monte Carlo simulations, showing accurate estimators. We implement this model to the residuals after fitting an harmonic model to light-curves from periodic variable stars from the Optical Gravitational Lensing Experiment (OGLE) and Hipparcos surveys, showing that the model can identify time dependency structure that remains in the residuals when, for example, the period of the light-curves was not properly estimated.

scholarly journals Asteroseismic potential of CHEOPS

2018 ◽  
Vol 620 ◽  
pp. A203 ◽  
Author(s):  
A. Moya ◽  
S. Barceló Forteza ◽  
A. Bonfanti ◽  
S. J. A. J. Salmon ◽  
V. Van Grootel ◽  
...  
Keyword(s):  
Time Series ◽  
Main Sequence ◽  
Uncertainty Reduction ◽  
Light Curves ◽  
Accuracy And Precision ◽  
Mass Uncertainty ◽  
The Impact ◽  
Host Stars

Context. Asteroseismology has been impressively boosted during the last decade mainly thanks to space missions such as Kepler/K2 and CoRoT. This has a large impact, in particular, in exoplanetary sciences since the accurate characterization of the exoplanets is convoluted in most cases with the characterization of their hosting star. In the decade before the expected launch of the ESA mission PLATO 2.0, only two important missions will provide short-cadence high-precision photometric time-series: NASA–TESS and ESA–CHEOPS missions, both having high capabilities for exoplanetary sciences. Aims. In this work we want to explore the asteroseismic potential of CHEOPS time-series. Methods. Following the works estimating the asteroseismic potential of Kepler and TESS, we have analysed the probability of detecting solar-like pulsations using CHEOPS light-curves. Since CHEOPS will collect runs with observational times from hours up to a few days, we have analysed the accuracy and precision we can obtain for the estimation of νmax. This is the only asteroseismic observable we can recover using CHEOPS observations. Finally, we have analysed the impact of knowing νmax in the characterization of exoplanet host stars. Results. Using CHEOPS light-curves with the expected observational times we can determine νmax for massive G and F-type stars from late main sequence (MS) on, and for F, G, and K-type stars from post-main sequence on with an uncertainty lower than a 5%. For magnitudes V <  12 and observational times from eight hours up to two days, the HR zone of potential detectability changes. The determination of νmax leads to an internal age uncertainty reduction in the characterization of exoplanet host stars from 52% to 38%; mass uncertainty reduction from 2.1% to 1.8%; radius uncertainty reduction from 1.8% to 1.6%; density uncertainty reduction from 5.6% to 4.7%, in our best scenarios.

scholarly journals Binary, Pulsating, and Irregular Variables Among Planetary Nuclei

1989 ◽  
Vol 114 ◽  
pp. 473-476 ◽  
Author(s):  
Howard E. Bond ◽  
Robin Ciardullo
Keyword(s):  
Planetary Nebula ◽  
Variable Stars ◽  
Close Binaries ◽  
Two Dimensional ◽  
Ccd Photometry ◽  
Photoelectric Photometry ◽  
The Past ◽  
Ccd Detector ◽  
Differential Photometry ◽  
Comparison Stars

For the past two years, the authors have been carrying out a program of CCD photometry of planetary-nebula nuclei (PNNs), using the 0.9-m telescopes at Kitt Peak National and Cerro Tololo Inter-American Observatories. The aim of this program is to investigate the variability of PNNs on timescales of minutes to days, in order to search for close binaries and pulsators, as well as unexpected new classes of variable stars.The program represents an extension of the photoelectric photometry of PNNs carried out by Bond and Grauer (1987). Use of the two-dimensional CCD detector allows us to model and subtract the nebulosity surrounding a PNN, in addition to providing exactly simultaneous observations of the PNN and several nearby comparison stars. The latter allow us to compensate for variable atmospheric transparency, permitting accurate differential photometry to be obtained even when the observing conditions are not photometric.

scholarly journals CCD VI time-series of the extremely metal-poor globular cluster M92: revisiting its variable star population

2020 ◽  
Vol 494 (3) ◽  
pp. 3212-3226 ◽  
Author(s):  
M A Yepez ◽  
A Arellano Ferro ◽  
D Deras
Keyword(s):  
Time Series ◽  
Globular Cluster ◽  
Variable Star ◽  
Variable Stars ◽  
Frequency Spectra ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
New Variables ◽  
Gaia Dr2

ABSTRACT We present an analysis of VI CCD time-series photometry of the Oo II type globular cluster M92. The variable star population of the cluster is studied with the aim of revising their classifications, identifications, frequency spectra, and to select indicators of the parental cluster metallicity and distance. The Fourier decomposition of RR Lyrae light curves lead to the estimation of mean [Fe/H]spec = −2.20 ± 0.18 and distance of 8.3 ± 0.2 kpc. Four new variables are reported: one RRd (V40), a multimode SX Phe (V41), an SR (V42), and one RRc (F1) that is most likely not a cluster member. The AC nature of V7 is confirmed. The double mode nature of the RRc star V11 is not confirmed and its amplitude modulations are most likely due to the Blazhko effect. Two modes are found in the known RRc variable V13. It is argued that the variable V30, previously classified as RRab is, in fact, a BL Her-type star not belonging to the cluster. Using the Gaia-DR2 proper motions, we identified 5012 stars in the field of the cluster, which are very likely cluster members, and for which we possess photometry, enabling the production of a refined colour–magnitude diagram. This also allowed us to identify a few variable stars that do not belong to the cluster. The RR Lyrae pulsation modes on the HB are cleanly separated by the first overtone red edge, a common feature in all Oo II-type clusters.

scholarly journals CCD PHOTOMETRY USING MULTIPLE COMPARISON STARS

2004 ◽  
Vol 21 (3) ◽  
pp. 191-200 ◽  
Author(s):  
Yonggi Kim ◽  
Ivan L. Andronov ◽  
Young-Beom Jeon
Keyword(s):  
Multiple Comparison ◽  
Ccd Photometry ◽  
Comparison Stars

scholarly journals Activity of (2060) Chiron possibly caused by impacts?

2018 ◽  
Vol 475 (2) ◽  
pp. 2512-2518 ◽  
Author(s):  
Stefan Cikota ◽  
Estela Fernández-Valenzuela ◽  
Jose Luis Ortiz ◽  
Nicolás Morales ◽  
René Duffard ◽  
...  
Keyword(s):  
Time Series ◽  
Mass Loss ◽  
Surface Brightness ◽  
Light Curves ◽  
Loss Mechanism ◽  
Long Tail ◽  
Absolute Magnitudes ◽  
The Impact ◽  
Possible Cause ◽  
Calar Alto

Abstract The centaur 95P/(2060) Chiron is showing comet-like activity since its discovery, but the mass-loss mechanisms triggering its activity remained unexplained. Although the collision rates in the centaur region are expected to be very low, and impacts are thought not to be responsible for the mass-loss, since the recent indications that Chiron might possess a ring similar to Chariklo's, and assuming that there is debris orbiting around, the impact triggered mass-loss mechanism should not be excluded as a possible cause of its activity. From time series observations collected on Calar Alto Observatory in Spain between 2014 and 2016, we found that the photometric scatter in Chiron's data is larger than a control star's scatter, indicating a possible microactivity, possibly caused by debris falling back to Chiron's surface and lifting small clouds of material. We also present rotational light curves, and measurements of Chiron's absolute magnitudes, which are consistent with the models supporting the presumption that Chiron possesses rings. By co-adding the images acquired in 2015, we have detected an ∼5 arcsec long tail, showing a surface brightness of 25.3 mag(V) arcsec−2.

Accuracy in variable star work: The three-star single-channel technique

1993 ◽  
Vol 136 ◽  
pp. 106-112
Author(s):  
Michel Breger
Keyword(s):  
Extinction Coefficient ◽  
Variable Star ◽  
Single Channel ◽  
Variable Stars ◽  
Different Types ◽  
Comparison Stars

AbstractThe three-star technique for photoelectric photometers is discussed. The technique is used to study millimag variations of variable stars with periods in the range of 30 minutes to a few days. It is emphasized that for highest precision two comparison stars should be used and observed as often as the variable star. The different types of numbers used to express the precision of measurement are discussed together with possible misinterpretations.Finally, the successful use of an extinction coefficient derived from differential extinction between the three stars is illustrated with measurements showing an extreme amount of instrumental sensitivity drift.

A new pipeline for astrometry and photometry of asteroids

2018 ◽  
Vol 14 (A30) ◽  
pp. 43-43
Author(s):  
Y. Klç ◽  
M. Kaplan ◽  
Z. Eker
Keyword(s):  
Open Source ◽  
Light Curves ◽  
Multiple Comparison ◽  
Differential Photometry ◽  
Comparison Stars

AbstractUsing Python 3, astropy and astrometry.net, we have developed a pipeline to obtain photometric light curves of asteroids automatically queried by the SkyBoT database from sequential FITS images. The pipeline provides: pre-reduction of data, astrometry, standard differential photometry and light curves by auto-selecting multiple comparison stars (maximum user-defined) from NOMAD catalog via VizieR. The code is an open source, free and hosted on GitHub with the GNU GPL v3 license.

scholarly journals CCD photometry with small telescopes

1986 ◽  
Vol 118 ◽  
pp. 33-46
Author(s):  
Alistair R. Walker
Keyword(s):  
Variable Star ◽  
Ccd Camera ◽  
Light Curves ◽  
Ccd Photometry

CCD photometry with small telescopes often complements the use of such detectors on larger telescopes and in addition it is ideally suited to projects, such as determining variable star light curves, that require considerable amounts of observing time. Following a discussion of some of the techniques found useful for producing accurate CCD photometry, the results of several projects carried out with the SAAO 1m CCD camera are presented.

Sign in / Sign up

Export Citation Format

Share Document