scholarly journals Studying bright variable stars with the Multi-site All-Sky CAmeRA (MASCARA)

2018 ◽  
Vol 617 ◽  
pp. A32 ◽  
Author(s):  
O. Burggraaff ◽  
G. J. J. Talens ◽  
J. Spronck ◽  
A.-L. Lesage ◽  
R. Stuik ◽  
...  
Keyword(s):  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Previous Record ◽  
La Palma ◽  
Powerful Means ◽  
New Variables ◽  
Candidate Variable ◽  
Order Variability

Context. The Multi-site All-Sky CAmeRA (MASCARA) aims to find the brightest transiting planet systems by monitoring the full sky at magnitudes 4 < V < 8.4, taking data every 6.4 s. The northern station has been operational on La Palma since February 2015. These data can also be used for other scientific purposes, such as the study of variable stars. Aims. In this paper we aim to assess the value of MASCARA data for studying variable stars by determining to what extent known variable stars can be recovered and characterised, and how well new, unknown variables can be discovered. Methods. We used the first 14 months of MASCARA data, consisting of the light curves of 53 401 stars with up to one million flux points per object. All stars were cross-matched with the VSX catalogue to identify known variables. The MASCARA light curves were searched for periodic flux variability using generalised Lomb–Scargle periodograms. If significant variability of a known variable was detected, the found period and amplitude were compared with those listed in the VSX database. If no previous record of variability was found, the data were phase folded to attempt a classification. Results. Of the 1919 known variable stars in the MASCARA sample with periods 0.1 < P < 10 days, amplitudes >2%, and that have more than 80 h of data, 93.5% are recovered. In addition, the periods of 210 stars without a previous VSX record were determined, and 282 candidate variable stars were newly identified. We also investigated whether second order variability effects could be identified. The O’Connell effect is seen in seven eclipsing binaries, of which two have no previous record of this effect. Conclusions. MASCARA data are very well suited to study known variable stars. They also serve as a powerful means to find new variables among the brightest stars in the sky. Follow-up is required to ensure that the observed variability does not originate from faint background objects.

scholarly journals SuperWASP variable stars: classifying light curves using citizen science

2021 ◽  
Vol 502 (1) ◽  
pp. 1299-1311
Author(s):  
Heidi B Thiemann ◽  
Andrew J Norton ◽  
Hugh J Dickinson ◽  
Adam McMaster ◽  
Ulrich C Kolb
Keyword(s):  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Data Set ◽  
Resultant Data ◽  
Sky Survey ◽  
Short Period ◽  
Contact Binaries ◽  
Analysis Of Results

ABSTRACT We present the first analysis of results from the SuperWASP variable stars Zooniverse project, which is aiming to classify 1.6 million phase-folded light curves of candidate stellar variables observed by the SuperWASP all sky survey with periods detected in the SuperWASP periodicity catalogue. The resultant data set currently contains &gt;1 million classifications corresponding to &gt;500 000 object–period combinations, provided by citizen–scientist volunteers. Volunteer-classified light curves have ∼89 per cent accuracy for detached and semidetached eclipsing binaries, but only ∼9 per cent accuracy for rotationally modulated variables, based on known objects. We demonstrate that this Zooniverse project will be valuable for both population studies of individual variable types and the identification of stellar variables for follow-up. We present preliminary findings on various unique and extreme variables in this analysis, including long-period contact binaries and binaries near the short-period cut-off, and we identify 301 previously unknown binaries and pulsators. We are now in the process of developing a web portal to enable other researchers to access the outputs of the SuperWASP variable stars project.

scholarly journals A Comparison Between Binary Star Light Curves and Those of Possible Binary Asteroids

1984 ◽  
Vol 80 ◽  
pp. 387-392
Author(s):  
H. J. Schober
Keyword(s):  
Light Curve ◽  
Binary Star ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Binary Asteroids ◽  
Binary Nature ◽  
Rotation Rates ◽  
Photoelectric Observations

AbstractSince about ten years coordinated programs of photoelectric observations of asteroids are carried out to derive rotation rates and light curves. Quite a number of those asteroids exhibit features in their light curves, with similar characteristics as variable stars and especially eclipsing binaries. This would allow also an interpretation that there might be an evidence for the binary nature of some asteroids, based on observational hints. A few examples are given and a list of indications for the possible binary nature of asteroids, based on their light curve features, is presented.

scholarly journals First CCD observations of Magellanic Cloud variable stars from the Mt John University Observatory, New Zealand

1991 ◽  
Vol 148 ◽  
pp. 381-381
Author(s):  
William Tobin ◽  
A. C. Gilmore ◽  
Alan Wadsworth ◽  
S.R.D. West
Keyword(s):  
New Zealand ◽  
Evaluation Process ◽  
Variable Stars ◽  
Magellanic Cloud ◽  
Magellanic Clouds ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Ccd Observations ◽  
Differential Photometry

Late in 1988 the Mt John University Observatory acquired a cryogenic CCD system from Photometrics Ltd (Tucson). The chip is a Thomson CSF TH7882 CDA comprising 384 × 576 pixels. As part of the evaluation process, we have begun two differential photometry programs of the Magellanic Clouds using the Mt John 0.6m Boller & Chivens telescope. On this telescope each CCD pixel corresponds to 0.6 arcsec. Mt John's southerly latitude (44°S) permits year-round observations of the Clouds.The first program concerns B, V and I photometry of five blue eclipsing binaries selected, on the basis of Gaposchkin's (1970, 1977) photographic light curves, to have roughly equal components with minimal interaction. HV 12634 has also been observed for comparison with the CCD light curves published by Jensen et al. (1988). Fig. 1 shows the B observations so far obtained for HV 1761, but the reduction is preliminary, being based on aperture-integrated magnitudes. The field is populous, and a final reduction will require use of a crowded-field reduction package such as ROMAFOT.

Multifilter time-series observations of three short period ATLAS variable stars

2019 ◽  
Vol 490 (1) ◽  
pp. 1283-1293
Author(s):  
Chris Koen
Keyword(s):  
False Alarm Probability ◽  
Variable Stars ◽  
Reflection Effect ◽  
M Dwarfs ◽  
Alert System ◽  
Short Period ◽  
Period Detection ◽  
Hot Subdwarfs ◽  
Candidate Variable

ABSTRACT The ‘Asteroid Terrestrial-impact Last Alert System’ discovered hundreds of thousands of new candidate variable stars. Follow-up observations of three of these are reported in this paper. The targets were selected on the basis of having high probability of being periodic (false alarm probability for period detection smaller than 10−5), short periods (P < 0.2 d), and being relatively bright (g′ < 17). The targets were also chosen to be either very blue (g′ − i′ < −0.4, r′ − z′ < −0.4) or very red (g′ − i′ > 2.2, r′ − z′ > 1.5) as periodic variables with these colours are relatively rare. Two of the stars are hot subdwarfs, both of which are likely reflection effect binaries. In both cases simple models suggest that the companions may have masses very close to or below 0.1 $\, \mathrm{M}_\odot$. The third star is also a binary, which appears to consist of two M dwarfs in a near contact configuration. At 0.12 d its period is one of the shortest known for M-type binaries.

scholarly journals Period Analyses Without O-C Diagrams

2011 ◽  
Vol 7 (S282) ◽  
pp. 391-394 ◽  
Author(s):  
Zdeněk Mikulášek ◽  
Miloslav Zejda ◽  
Jan Janík
Keyword(s):  
Least Squares Method ◽  
Weighted Least Squares ◽  
Intermediate Stage ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Phase Information ◽  
General Applicability ◽  
Weighted Least Squares Method ◽  
Phase Functions

AbstractWe present a versatile method appropriate for the period analyses of observations containing phase information of all kinds of periodic or nearly periodic variable stars on the basis of phenomenological modelling of their phase curves and phase functions. The approach is based on rigorous application of a non-linear weighted least-squares method exploiting all available observational data and does not need an O-C diagram as an intermediate stage for period analyses. However, this approach enables us to determine precise times of extrema of light curves, to calculate ephemerides and construct plausible O-C diagrams. We substantiate the general applicability of the method on eclipsing binaries research.

scholarly journals TheKepler Missionand Eclipsing Binaries

2006 ◽  
Vol 2 (S240) ◽  
pp. 236-243 ◽  
Author(s):  
David Koch ◽  
William Borucki ◽  
Gibor Basri ◽  
Timothy Brown ◽  
Douglas Caldwell ◽  
...  
Keyword(s):  
Eclipsing Binaries ◽  
Light Curves ◽  
Field Of View ◽  
Habitable Zone ◽  
Target List ◽  
Kepler Mission ◽  
Photometric Observations ◽  
Single Field ◽  
Verification Process

AbstractTheKepler Missionis a space-based photometric mission with a differential photometric precision of 14 ppm (atV= 12 for a 6.5 hour transit). It is designed to continuously observe a single field of view (FOV) of greater then 100 square degrees in the Cygnus-Lyra region for four or more years. The primary goal of the mission is to monitor more than one-hundred thousand stars for transits of Earth-size and smaller planets in the habitable zone of solar-like stars. In the process, many eclipsing binaries (EB) will also be detected and light curves produced. To enhance and optimize the mission results, the stellar characteristics for all the stars in theKeplerFOV withV< 16 will have been determined prior to launch. As part of the verification process, stars with transit candidates will have radial-velocity follow-up observations performed to determine the component masses and thereby separate eclipses caused by stellar companions from transits caused by planets. The result will be a rich database on EBs. The community will have access to the archive for further analysis, such as, for EB modeling of the high-precision light curves. A guest observer program is also planned to allow for photometric observations of objects not on the target list but within the FOV.

scholarly journals DIRECT Distances to Local Group Galaxies

2000 ◽  
Vol 176 ◽  
pp. 182-186 ◽  
Author(s):  
Dimitar D. Sasselov
Keyword(s):  
Local Group ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Stepping Stones ◽  
The Past ◽  
Cepheid Variables ◽  
Direct Distance ◽  
Nearby Galaxies

AbstractThe two nearby galaxies, M31 and M33, are stepping stones for most of our current efforts to understand the evolving universe at large scales. We are undertaking a long term project, called DIRECT, to improve the direct distance estimate to M31 and M33. The massive photometry we have obtained as part of our project over the past 3 years provides us with very good light curves for known and new Cepheid variables, a large number of eclipsing binaries and other variable stars.

scholarly journals A PSF-based Approach to TESS High quality data Of Stellar clusters (PATHOS) – I. Search for exoplanets and variable stars in the field of 47 Tuc

2019 ◽  
Vol 490 (3) ◽  
pp. 3806-3823 ◽  
Author(s):  
D Nardiello ◽  
L Borsato ◽  
G Piotto ◽  
L S Colombo ◽  
E E Manthopoulou ◽  
...  
Keyword(s):  
High Precision ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Quality Data ◽  
Stellar Clusters ◽  
High Quality ◽  
High Quality Data ◽  
Stellar Cluster ◽  
Crowded Environments

ABSTRACT The TESS mission will survey ∼85  per cent of the sky, giving us the opportunity of extracting high-precision light curves of millions of stars, including stellar cluster members. In this work, we present our project ‘A PSF-based Approach to TESS High quality data Of Stellar clusters’ (PATHOS), aimed at searching and characterize candidate exoplanets and variable stars in stellar clusters using our innovative method for the extraction of high-precision light curves of stars located in crowded environments. Our technique of light-curve extraction involves the use of empirical point spread functions (PSFs), an input catalogue and neighbour-subtraction. The PSF-based approach allows us to minimize the dilution effects in crowded environments and to extract high-precision photometry for stars in the faint regime (G &gt; 13). For this pilot project, we extracted, corrected, and analysed the light curves of 16 641 stars located in a dense region centred on the globular cluster 47 Tuc. We were able to reach the TESS magnitude T ∼ 16.5 with a photometric precision of ${\sim} 1{{\ \rm per\ cent}}$ on the 6.5-h time-scale; in the bright regime we were able to detect transits with depth of ∼34 parts per million. We searched for variables and candidate transiting exoplanets. Our pipeline detected one planetary candidate orbiting a main-sequence star in the Galactic field. We analysed the period–luminosity distribution for red-giant stars of 47 Tuc and the eclipsing binaries in the field. Light curves are uploaded on the Mikulski Archive for Space Telescopes under the project PATHOS.

scholarly journals Planets, candidates, and binaries from the CoRoT/Exoplanet programme

2018 ◽  
Vol 619 ◽  
pp. A97 ◽  
Author(s):  
M. Deleuil ◽  
S. Aigrain ◽  
C. Moutou ◽  
J. Cabrera ◽  
F. Bouchy ◽  
...  
Keyword(s):  
Major Axis ◽  
Space Mission ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Current Status ◽  
False Alarms ◽  
Semi Major Axis ◽  
Contact Binaries ◽  
Initial List

The CoRoT space mission observed 163 665 stars over 26 stellar fields in the faint star channel. The exoplanet teams detected a total of 4123 transit-like features in the 177 454 light curves. We present the complete re-analysis of all these detections carried out with the same softwares so that to ensure their homogeneous analysis. Although the vetting process involves some human evaluation, it also involves a simple binary flag system over basic tests: detection significance, presence of a secondary, difference between odd and even depths, colour dependence, V-shape transit, and duration of the transit. We also gathered the information from the large accompanying ground-based programme carried out on the planet candidates and checked how useful the flag system could have been at the vetting stage of the candidates. From the initial list of transit-like features, we identified and separated 824 false alarms of various kind, 2269 eclipsing binaries among which 616 are contact binaries and 1653 are detached ones, 37 planets and brown dwarfs, and 557 planet candidates. We provide the catalogue of all these transit-like features, including false alarms. For the planet candidates, the catalogue gives not only their transit parameters but also the products of their light curve modelling: reduced radius, reduced semi-major axis, and impact parameter, together with a summary of the outcome of follow-up observations when carried out and their current status. For the detached eclipsing binaries, the catalogue provides, in addition to their transit parameters, a simple visual classification. Among the planet candidates whose nature remains unresolved, we estimate that eight (within an error of three) planets are still to be identified. After correcting for geometric and sensitivity biases, we derived planet and brown dwarf occurrences and confirm disagreements with Kepler estimates, as previously reported by other authors from the analysis of the first runs: small-size planets with orbital period less than ten days are underabundant by a factor of three in the CoRoT fields whereas giant planets are overabundant by a factor of two. These preliminary results would however deserve further investigations using the recently released CoRoT light curves that are corrected of the various instrumental effects and a homogeneous analysis of the stellar populations observed by the two missions.

scholarly journals The ASAS-SN Catalog of Variable Stars IX: The Spectroscopic Properties of Galactic Variable Stars

2021 ◽  
Author(s):  
T Jayasinghe ◽  
C S Kochanek ◽  
K Z Stanek ◽  
B J Shappee ◽  
T W-S Holoien ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Spectroscopic Properties ◽  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Pulsation Period ◽  
Strongly Correlated ◽  
Fixed Temperature ◽  
V Band ◽  
Long Baseline

Abstract The All-Sky Automated Survey for Supernovae (ASAS-SN) provides long baseline (∼4 yrs) V −band light curves for sources brighter than V≲ 17 mag across the whole sky. We produced V-band light curves for a total of ∼61.5 million sources and systematically searched these sources for variability. We identified ∼426, 000 variables, including ∼219, 000 new discoveries. Most (${\sim }74\%$) of our discoveries are in the Southern hemisphere. Here we use spectroscopic information from LAMOST, GALAH, RAVE, and APOGEE to study the physical and chemical properties of these variables. We find that metal-poor eclipsing binaries have orbital periods that are shorter than metal-rich systems at fixed temperature. We identified rotational variables on the main-sequence, red giant branch and the red clump. A substantial fraction (${\gtrsim }80\%$) of the rotating giants have large vrot or large NUV excesses also indicative of fast rotation. The rotational variables have unusual abundances suggestive of analysis problems. Semi-regular variables tend to be lower metallicity ($\rm [Fe/H]{\sim }-0.5$) than most giant stars. We find that the APOGEE DR16 temperatures of oxygen-rich semi-regular variables are strongly correlated with the WRP − WJK color index for $\rm T_{eff}\lesssim 3800$ K. Using abundance measurements from APOGEE DR16, we find evidence for Mg and N enrichment in the semi-regular variables. We find that the Aluminum abundances of the semi-regular variables are strongly correlated with the pulsation period, where the variables with $\rm P\gtrsim 60$ days are significantly depleted in Al.

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