Available OEJV publications
PROPERTIES OF THE RECENTLY DISCOVERED ECLIPSING BINARY GSC 03421-01402
Ch. Lloyd, J. Screech
GSC 03421-01402 is a low-amplitude eclipsing binary with a period of 7.6800475(44) d. The eclipsing binary is one component of a close pair identified in the Gaia EDR3 data with delta G = 0.45 mag. The light-curve suggests that the primary eclipse is total with an observed depth of 0.13 mag, but due to dilution the true depth could be approximately 0.23 or 0.37 mag. A weak, 0.02 mag, secondary eclipse is seen displaced slightly to phase 0.491. The system is probably a detached Algol-type eclipsing binary dominated by a mid G-type primary, but until the uncertainties in the relative magnitudes and distance are resolved much remains in doubt.
PROCEEDINGS OF THE 52nd CONFERENCE ON VARIABLE STARS RESEARCH
Editor-in-chief: R. Kocián
The Variable Star and Exoplanet Section of the Czech Astronomical Society organised a traditional autumn conference on research and news in variable stars. In 2020, all human activities were affected by a global pandemic. The restrictions associated with the pandemic also affected the holding of our conference. For the first time in the conference's history, we were forced to move it to a virtual space. Despite all the obstacles and limitations of the internet meeting, many quality contributions were made, and many questions were answered in subsequent discussions. Some of these contributions are presented in this paper. Of course, all presented contributions can also be viewed on our YouTube channel. We can only believe that in 2021 we will meet face to face again.
VX HYA TIME KEEPING. STROBOSCOPIC ANALYSIS
Photometric observations of the double-mode pulsator VX Hya are presented. They are analyzed with a stroboscopic method, completed by Fourier analysis.
26 NEW MIRA VARIABLES FROM THE ZTF SURVEY
K. Bernhard, S. Hümmerich
We have continued our search for hitherto unregistered Mira variables in publicly available sky survey data, using observations from the Zwicky Transient Facility and the information provided in the Zwicky Transient Facility Suspected Variables Catalog, which led to the discovery of 26 new Mira stars. Essential data as well as light curves and phase plots for all stars are presented.
GSC 03588-09315 IS A LOW-AMPLITUDE DELTA SCUTI VARIABLE
Ch. Lloyd, Y. Öğmen, G. Walker, K. Menzies, G. Stone, D. Boyd
Time-series observations of GSC 03588-09315 show it is a very low amplitude, multiperiodic delta Scuti variable at the limit of detectability. Five frequencies have been identified at 13.86819(24), 8.10026(79), 5.01966(79), 11.67281(55) and 8.17490(59) c/d with amplitudes of 10, 5, 5, 4, and 3 mmag respectively. The spectral energy distribution of the star is very closely matched to a spectral type of F0V, but it is probably 1.3 mag brighter than a main-sequence star, so is likely to be evolved.
SEARCH FOR PERIOD CHANGES IN MIRA STARS
R. Nesci, G. Rocchi
We reobserved in the RC and i'Sloan bands, during the years 2020-2021, seven Mira variables in Cassiopeia, for which historical i'Sloan light curves were available from Asiago Observatory plates taken in the years 1967-84. The aim was to check if any of them had undergone a substantial change in the period or in the light curve shape. Very recent public data form ZTF-DR5 were also used to expand our time base window. A marked color change was detected for all the stars along their variability cycle. The star V890 Cas showed a significant period decrease of 12% from 483 to 428 days, one of the largest known to date. All the stars, save AV Cas, showed a smaller variation amplitude in the recent CCD data, possibly due to a photometric accuracy higher than that of the photographic plates.
MINIMA AND MAXIMA TIMINGS OF SEVERAL VARIABLE STARS
We present 228 times of minima of 33 eclipsing binaries and nine maxima timings of two pulsating stars. The majority of the objects are newly discovered variables and they were observed as by product. The observations were employed five different telescopes with diameters from 20cm up to 2.3m and six cameras in three different observatories located in Greece.
CONFIRMATION OF SEVEN FAINT ATLAS VARIABLE STAR CANDIDATES
N. Thomas, C. Guan
A pilot survey conducted at the Lookout Observatory has confirmed seven faint (V ~ 13 to 17) variables in the region of Kepler-76b that were recently discovered by the Asteroid Terrestrial-Impact Last Alert System (ATLAS). The ATLAS survey identified 315,000 probably variables within its wide-field survey in 2018. The faintness (down to r ~ 18) and small amplitudes (down to 0.02 mag) included in these candidates makes external validation difficult. Our confirmation of seven such variable stars gives credibility to the ATLAS list. Further, the agreement between various surveys and LO data validates the use of our new survey for variable star and exoplanet research.
L199, A NEW VARIABLE STAR IN M13
During a routine study of the variable stars of Messier 13 (NGC 6205 = Cl 1639+365) we have discovered the variability of L199 (TYC 2588-1386-2), a red giant star member of the cluster: using the photometric data –in V band– obtained in the 2019 and 2020 campaigns we have verified its variability. Data from the Zwicky Transient Facility (ZTF) and Deras et al. (2019) were utilized to determine its type of variability and period estimation: our data suggest that it is a semiregular red giant, similar to the other variables of this type of the cluster, whose cycles of photometric variation are not identical; we derived a period of ~27 days (although without a regular periodicity) and an amplitude smaller: 0.08 ± 0.03 magnitudes in V band although they may be somewhat larger or smaller. With this discovery the cluster now has 63 variable stars.
CCD MINIMA FOR SELECTED ECLIPSING BINARIES IN 2020
A total of 212 CCD determinations of times of minima for selected eclipsing binaries occurring in 2020 are presented. These were obtained at either Mountain Ash Observatory in Prince George, BC, Canada or Desert Blooms Observatory in Benson, AZ, USA.
B.R.N.O. CONTRIBUTIONS #41 - TIMES OF MINIMA
M. Lehký, K. Hoňková, L. Šmelcer, M. Souza de Joode, F. Bílek, et al.
This paper presents 2109 times of minima for 965 objects acquired by 59 members and cooperating observers of the Variable Star and Exoplanet Section of the Czech Astronomical Society (B.R.N.O. Observing project). These observations were submitted to the website of the Variable Star and Exoplanet Section of the Czech Astronomical Society between November 2016 and March 2018.
NEW ECLIPSING BINARY TIMES OF MINIMA IN THE NORTHERN SKY MEASURED DURING THE YEAR 2020
We present 167 times of minima of 69 eclipsing binaries in the Northern Sky determined from differential, partly multicolor photometry, during the year 2020.
CK AQR TIME KEEPING. EVIDENCE FOR A THIRD BODY
OEJV Issue 209 (30.12.2020):
Photometric measurements of the contact binary system CK Aqr are presented. 49 new times of minimum were obtained between 2005 and 2020. Along with already published observations, this allows the derivation of an improved ephemeris. The resulting O-C diagram shows oscillations which are interpreted as the light time travel effect due to a third component, with a period of 8.2 years.
PROCEEDINGS OF THE 51st CONFERENCE ON VARIABLE STARS RESEARCH
Editor-in-chief: R. Kocián
The Variable Star and Exoplanet Section of the Czech Astronomical Society organized traditional autumn conference on research and news in the field of variable stars. The conference was held in a comfortable space of Ostrava Planetarium. In addition to the many contributions that were presented on site, we had the opportunity to hear lectures of invited speakers from abroad via Internet transmission. All presented contributions can be viewed on our YouTube channel.
THE BRIGHT ECLIPSING BINARY NSV 4031 IS NOT VARIABLE
Ch. Lloyd, D. Conner, R. Pickard, E. N. Walker
Observations of the supposed eclipsing binary NSV 4031 from time-series photometry and data from several synoptic instruments show no evidence of an eclipse or any periodic variation with an amplitude above 0.05 magnitudes. The spectral energy distribution of the star is very closely matched to a spectral type of F5IV.
FOUR CANDIDATE BINARY STARS WITH STRONG REFLECTION EFFECT FROM THE ZWICKY TRANSIENT FACILITY
K. Bernhard, S. Hümmerich
AbstractWe present five stars from the ZTF Catalogue of Periodic Variable Stars whose properties are fully compatible with variable stars of GCVS-type R, that is, short-period binary systems with light variations dominated by strong reflection effect. If verified by spectroscopic studies, our results show that the variability amplitude limit of 1.0 mag (V) currently listed in the International Variable Star Index can be exceeded and may be in need of revision.
NEW CCD TIMES OF MINIMA OF ECCENTRIC ECLIPSING BINARY SYSTEMS IN 2017-2019
M.-J. Jeong, C.-H. Kim, M.-H. Song, E.-C. Sung, J.-H. Park, K.-Y. Han, T.-S. Jeong, C. Han
AbstractWe present 88 times of minima for 56 eccentric eclipsing binary systems determined from photometric observations at the Sobaeksan Optical Astronomical Observatory (SOAO) in Republic of Korea from February 2017 to December 2019.