Chromospheric activity of periodic variable stars (including eclipsing binaries) observed in DR2 LAMOST stellar spectral survey

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 >1 million classifications corresponding to >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.

Download Full-text

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201833142 ◽

2018 ◽

Vol 617 ◽

pp. A32 ◽

Cited By ~ 8

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.

Download Full-text

Professional/Amateur Cooperation in the Study of Variable Stars as Illustrated by the Fourth Edition of the GCVS

International Astronomical Union Colloquium ◽

10.1017/s0252921100092800 ◽

1988 ◽

Vol 98 ◽

pp. 188-189

Author(s):

M.S. Frolov

Keyword(s):

Classical Group ◽

Cataclysmic Variables ◽

Variable Stars ◽

Eclipsing Binaries ◽

Fourth Edition ◽

Rr Lyrae Stars ◽

Rr Lyrae ◽

Long Time ◽

Hand Involvement ◽

Lyrae Stars

Let us divide variable stars into two main groups: the first “classical” group, includes objects known for a long time, such as Cepheids, RR-Lyrae stars, Miras, cataclysmic variables, eclipsing binaries, etc. The second group includes micropulsating variables of δ Scuti and β Cephei types, magnetic variables, rotating variables of BY Draconis type, etc.Historically, the contribution of amateurs in investigating the first group was very significant, and it continues to increase. On the other hand, involvement in studying the second group of stars was practically equal to zero some years ago, but today one can see the beginnings of an expansion of amateur work on this second group of variables – among brighter objects, of course. One reason is the beginning of cooperation between amateurs and professional astronomers having powerful instruments.

Download Full-text

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

International Astronomical Union Colloquium ◽

10.1017/s0252921100088722 ◽

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.

Download Full-text

Commission 27. (Variable Stars.)

Transactions of the International Astronomical Union ◽

10.1017/s0251107x00017636 ◽

1936 ◽

Vol 5 ◽

pp. 336-337

Author(s):

A. A. Nijland ◽

Felix De Roy

Keyword(s):

Variable Stars ◽

Eclipsing Binaries ◽

General Assembly ◽

Draft Report ◽

The Future

The draft report was discussed, and adopted with some alterations and additions. The following resolutions were referred to the General Assembly:1.The Commission recommends that the yearly subsidy granted by the Union for the publication of the Cracow Ephemerides of Eclipsing Binaries (Prof. T. Banachiewicz) be continued to the amount of 700 gold francs, and expresses the wish that the decimal division of the day used in these ephemerides will be, in the future, counted from Greenwich Noon.2.The Union having endorsed the proposal made by Prof. Grouiller to compile a list of unpublished observations of Variable Stars, and recommended that this compilation be published by the Union, the Commission recommends that a subsidy of 200 gold francs should be granted to that object.3.The Commission recommends that Prof. Nijland’s Lists A, B, and C, brought up to date, together with a new list D, should be published by the Union with a subsidy not exceeding 300 gold francs.

Download Full-text

A search for variable subdwarf B stars in TESS full frame images – I. Variable objects in the southern ecliptic hemisphere

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2991 ◽

2020 ◽

Vol 499 (4) ◽

pp. 5508-5526

Author(s):

S K Sahoo ◽

A S Baran ◽

S Sanjayan ◽

J Ostrowski

Keyword(s):

Preliminary Analysis ◽

Variable Stars ◽

Eclipsing Binaries ◽

Spectral Classification ◽

B Stars ◽

Mode Identification ◽

Pulsating Stars ◽

Subdwarf B Stars ◽

Amplitude Spectra

ABSTRACT We report the results of our search for pulsating subdwarf B stars in full frame images, sampled at 30 min cadence and collected during Year 1 of the TESS mission. Year 1 covers most of the southern ecliptic hemisphere. The sample of objects we checked for pulsations was selected from a subdwarf B stars data base available to public. Only two positive detections have been achieved, however, as a by-product of our search we found 1807 variable objects, most of them not classified, hence their specific variability class cannot be confirmed at this stage. Our preliminary discoveries include: 2 new subdwarf B (sdB) pulsators, 26 variables with known sdB spectra, 83 non-classified pulsating stars, 83 eclipsing binaries (detached and semidetached), a mix of 1535 pulsators and non-eclipsing binaries, two novae, and 77 variables with known (non-sdB) spectral classification. Among eclipsing binaries we identified two known HW Vir systems and four new candidates. The amplitude spectra of the two sdB pulsators are not rich in modes, but we derive estimates of the modal degree for one of them. In addition, we selected five sdBV candidates for mode identification among 83 pulsators and describe our results based on this preliminary analysis. Further progress will require spectral classification of the newly discovered variable stars, which hopefully include more subdwarf B stars.

Download Full-text

Advances in Telescope and Detector Technologies – Impacts on the Study and Understanding of Binary Star and Exoplanet Systems

Proceedings of the International Astronomical Union ◽

10.1017/s1743921311026792 ◽

2011 ◽

Vol 7 (S282) ◽

pp. 11-20

Author(s):

Edward F. Guinan ◽

Scott Engle ◽

Edward J. Devinney

Keyword(s):

New Technologies ◽

Frequency Comb ◽

Binary Star ◽

Space Missions ◽

Variable Stars ◽

Eclipsing Binaries ◽

Wide Field ◽

Large Telescope ◽

Exoplanet Systems ◽

The Impact

AbstractCurrent and planned telescope systems (both on the ground and in space) as well as new technologies will be discussed with emphasis on their impact on the studies of binary star and exoplanet systems. Although no telescopes or space missions are primarily designed to study binary stars (what a pity!), several are available (or will be shortly) to study exoplanet systems. Nonetheless those telescopes and instruments can also be powerful tools for studying binary and variable stars. For example, early microlensing missions (mid-1990s) such as EROS, MACHO and OGLE were initially designed for probing dark matter in the halos of galaxies but, serendipitously, these programs turned out to be a bonanza for the studies of eclipsing binaries and variable stars in the Magellanic Clouds and in the Galactic Bulge. A more recent example of this kind of serendipity is the Kepler Mission. Although Kepler was designed to discover exoplanet transits (and so far has been very successful, returning many planetary candidates), Kepler is turning out to be a “stealth” stellar astrophysics mission returning fundamentally important and new information on eclipsing binaries, variable stars and, in particular, providing a treasure trove of data of all types of pulsating stars suitable for detailed Asteroseismology studies. With this in mind, current and planned telescopes and networks, new instruments and techniques (including interferometers) are discussed that can play important roles in our understanding of both binary star and exoplanet systems. Recent advances in detectors (e.g. laser frequency comb spectrographs), telescope networks (both small and large – e.g. Super-WASP, HAT-net, RoboNet, Las Combres Observatory Global Telescope (LCOGT) Network), wide field (panoramic) telescope systems (e.g. Large Synoptic Survey Telescope (LSST) and Pan-Starrs), huge telescopes (e.g. the Thirty Meter Telescope (TMT), the Overwhelming Large Telescope (OWL) and the Extremely Large Telescope (ELT)), and space missions, such as the James Webb Space Telescope (JWST), the possible NASA Explorer Transiting Exoplanet Survey Satellite (TESS – recently approved for further study) and Gaia (due for launch during 2013) will all be discussed. Also highlighted are advances in interferometers (both on the ground and from space) and imaging now possible at sub-millimeter wavelengths from the Extremely Long Array (ELVA) and Atacama Large Millimeter Array (ALMA). High precision Doppler spectroscopy, for example with HARPS, HIRES and more recently the Carnegie Planet Finder Spectrograph, are currently returning RVs typically better than ~2-m/s for some brighter exoplanet systems. But soon it should be possible to measure Doppler shifts as small as ~10-cm/s – sufficiently sensitive for detecting Earth-size planets. Also briefly discussed is the impact these instruments will have on the study of eclipsing binaries, along with future possibilities of utilizing methods from the emerging field of Astroinformatics, including: the Virtual Observatory (VO) and the possibilities of analyzing these huge datasets using Neural Network (NN) and Artificial Intelligence (AI) technologies.

Download Full-text

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

Symposium - International Astronomical Union ◽

10.1017/s0074180900200934 ◽

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.

Download Full-text

Eclipsing Binaries in the LMC: a Wealth of Data for Astrophysical Tests

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307004310 ◽

2006 ◽

Vol 2 (S240) ◽

pp. 377-379

Author(s):

A. Derekas ◽

L. L. Kiss ◽

T. R. Bedding

Keyword(s):

Large Magellanic Cloud ◽

Variable Stars ◽

Period Change ◽

Eclipsing Binaries ◽

Third Body ◽

Orbital Inclination ◽

Eclipsing Stars ◽

Period Distribution ◽

New Period ◽

Clean Sample

AbstractWe have analysed publicly available MACHO observations of 6833 variable stars in the Large Magellanic Cloud, classified as eclipsing binaries. After finding that a significant fraction of the sample was misclassified, we redetermined periods and variability class for all stars, producing a clean sample of 3031 eclipsing binaries. We have investigated their distribution in the period-color-luminosity space, which was used, for example, to assign a foreground probability to every object and establish new period-luminosity relations to selected types of eclipsing stars. We found that the orbital period distribution of LMC binaries is very similar to those of the SMC and the Milky Way. We have also determined the rate of period change for every star using the O-C method, discovering about 40 eclipsing binaries with apsidal motion, 45 systems with cyclic period changes and about 80 stars with parabolic O-C diagrams. In a few objects we discovered gradual amplitude variation, which can be explained by changes in the orbital inclination caused by a perturbing third body in the system.

Download Full-text