Available OEJV publications
INVESTIGATION OF THE PHYSICAL ORIGIN OF MULTIWAVELENGTH VARIABILITY IN ACCRETING COMPACT OBJECTS
AbstractThis paper deals with the effects of physical processes on multiwavelength variability of intermediate polars. Intermediate polars are binary systems consisting of a white dwarf that accretes matter from a red dwarf. This causes variability in the system’s observed brightness and spectra, making intermediate polars variable stars. The process of inverse Compton scattering was simulated for changing parametres of the system. For the simulation, Monte Carlo methods were used. We found that in the hot post-shock region, photon energies are increased by inverse Compton scattering. The effects vary with changing mass accretion rate, where for higher mass accretion rate, photons are upscattered to higher energies.
NEW FEATURES IN SOFTWARE OCFIT
AbstractSoftware OCFit is designed for fitting O-C diagrams of eclipsing binaries and transiting exoplanets by standard analytical models (e.g. light-time effect or apsidal motion). The program is written in the modern language Python. A very intuitive graphic user interface is also a part of this software. Moreover, OCFit could be used as a Python package in your own code. Its development started in 2015. GUI was published three years later. Here, we present changes and the newly implemented features in this software since its publishing in 2018 (mainly during the year 2022).
ESTIMATING THE PERIODS OF FOUR LUMINOUS BLUE VARIABLES (LBVS): η CAR, AG CAR, HR CAR, AND S DOR
AbstractThis article discusses four Luminous Blue Variables (LBVs): η Car, AG Car, HR Car in the Milky Way and S Dor in the LMC. LBVs are difficult stars to understand because of their sudden eruptions. Time scales for these "great eruptions" are uncertain, possibly hundreds to thousands of years. Historical data on some of these stars from the AID International Database have been analysed using the AAVSO Vstar program, with the date-compensated discrete Fourier transformation (DCDFT) and with the CLEANest algorithm. The results show that there are multiple periods in the range of ten to thirty years, in addition to the much longer time scales of the significant eruptions, which are beyond the scope of this research.
TIME-SERIES PHOTOMETRY AND ANALYSIS OF THE BY DRACONIS CLASS STAR: GSC 05586-00270
M.S. Brincat, C. Galdies, W. Grech, K. Hills, M. Mifsud
AbstractThis study investigates GSC 05586-00270 (a BY Draconis star) through data obtained from the ASAS-SN survey and additional observations from several observatories in Malta and another at La Palma (Spain). The study reveals the star's multi-period variability, with a primary period of 9.098805 ± 0.001507 days. Our analysis demonstrates that the primary period is relatively stable. Data analysis also divulged occasional fading and systematic variations in brightness and colour as the star undergoes rotation coupled with phenomena emanating from magnetic activity. A long-term period of approximately 4442 days was also identified, suggesting potential star spot migration influenced by other external factors. As opposed to some BY Draconis stars that are single, our analysis indicates that GSC 05586-00270 is likely to be a binary star system, influencing further the star's brightness variations. These findings shed light on the dynamic nature of this star and highlight the need for more comprehensive research to understand its behaviour further.
PERIOD CHANGES OF FOUR CEPHEID VARIABLES
M. Hontarenko, V. Marsakova, I. Andronov
AbstractWe have analysed the AAVSO (2023) photometric (UBVRI) observations of several dozens of Cepheids and W Vir variables. These observations allowed us to find the period changes of four Cepheid variables: zeta Gem, VX Cyg, V Lac, TT Aql. Mean phase light curves were obtained for 3-5 time intervals of observations using trigonometrical polynomial approximations of data in the V-band. VX Cyg shows the period decrease in 400 days interval that is also accompanied by the decrease of asymmetry. It was impossible to find regularities of period changes of other variables within error estimates due to the relatively small amount of observed cycles.
PROPERTIES OF THE LOW-AMPLITUDE W URSAE MAJORIS BINARY GSC 02873-03309
Ch. Lloyd, I. Miller
AbstractGSC 02873-03309 is a low-amplitude W~Ursae Majoris eclipsing binary with a period of 0.4996319(2) d. The eclipses have depths of 0.107 and 0.102 mag in the TESS data suggesting a low inclination. The absolute magnitude is consistent with other W UMa systems of similar period, and there is currently no evidence of period change.
R. Nesci, A. Vagnozzi, S. Valentini
AbstractThe light curve of the cataclismic variable ASASSN-18aan is studied using recent observations of the MC589 Observatory, giving an orbital Period and Epoch fully consistent with the data obtained after the discovery flare in 2018. Archival data from ASASSN, ZTF and Gaia were used to check if its flares have a quasi-periodic behaviour. A recurrence time scale of about 11 months is found, confirming a previous tentative result using the historic plate archive of the Asiago Observatory. The next outbursts are expected by April 2023 and March 2024.
CANDIDATE TRIPLE-STAR SYSTEM WITH ELLIPSOIDAL COMPONENTS DETECTED IN VULPECULA THROUGH TESS PHOTOMETRY
G. Conzo, M. Moriconi, I. Peretto
AbstractMaGiV-1 is a candidate triple ellipsoidal star system in Vulpecula at coordinates RA(J2000) 19:52:19:13 and DEC(J2000) +23:29:59:7 classied as ELL+ELL, number 2344411 in AAVSO VSX database. Through photometry from the TESS Space Telescope, two signicant periods describing the orbital times of the components were identied using the Fourier transform. The analysis led to determining P(A-BC) = (4.269+-0.213)d the orbital period of the A-BC pair, the primary component with the secondary component described by another pair, and P(BC) = (0.610+-0.031)d the orbital period of the BC pair, the inner ellipsoidal system. However, it cannot be completely ruled out that the shorter period can be explained by pulsations of one of the two components (e.g. by the GDOR type).
CCD MINIMA FOR SELECTED ECLIPSING BINARIES IN 2022
R.H. Nelson, K.B. Alton
AbstractA total of 150 CCD determinations of times of minimum for selected eclipsing binaries occurring in 2022 are presented. These were obtained at either Mountain Ash Observatory in Prince George, BC, Canada or Desert Blooms Observatory in Benson, AZ, USA.
UBVRI PHOTOMETRY OF BETELGEUSE OVER 23 YEARS SINCE 1999
Y. Ogane, O. Ohshima, D. Taniguchi, N. Takanashi
OEJV Issue 233 (04.11.2022):
Data - Table 1
Data - Table 2
AbstractWe report the results of our continuous UBVRI-band photometry of Betelgeuse from 1999 to 2022 using the same photometric system. There are two advantages in our observation: (1) we used a photodiode as a detector to avoid saturation, and (2) our data set includes U-band light curve, which is not widely observed in recent CCD photometries. Using our light curves, we conducted the periodicity analysis, and found ~405- and ~2160- day periods. We also discuss the tentative detection of a long-period variation over 20 years or longer. Finally, we discuss the peculiar variation of the U - B color index during the 'Great Dimming' event between late 2019 and early 2020.
DISCOVERY OF FOUR DELTA SCUTI STARS
AbstractFour stars, namely TYC 1615-03493-1, TYC 3672-00435-1, GSC 3672-0481, and TYC 5130-00273-1, are announced as new variables for the first time. The stars were observed as by-product and by applying standard photometry techniques, their light curves were obtained and analyzed using Fourier transformation methods. The results of the analyses showed that all of them are delta Scuti type pulsators, they exhibit multi-periodic oscillations and their dominant pulsation frequencies are derived.
A PHOTOMETRIC STUDY OF THE ACTIVE EW/RS BINARY STAR SYSTEM: GSC 05586-00371
M.S. Brincat, C. Galdies, W. Grech, F. Tavakkoli, K. Hills
AbstractGSC 05586-00371 is a fast-rotating (Prot ≈ 0.44 days) eclipsing binary. Our study showed that this star system is an overcontact eclipsing binary star that belongs to the W UMa class with characteristics of RS CVn type stars. We studied this binary system by photometric means through the V and I bandpass where data by the ASAS-SN survey have also been utilized. our photometry yielded a more precise orbital period that was obtained on its discovery. ASAS-SN data over a 6-year period revealed a long-term photometric wave that is attributed to star spot activity. We monitored the binary system over a 73-hour monitoring period to detect any possible flares from the system, where two consecutive events were monitored from one of our observing stations. Through the use of the Wilson-Devinney program as applied by Binary Maker 3.0, we have obtained a model for this binary system that reveals the presence of star spots on both components. Our results show that the star spot activity is rather dynamic where their influence on the system’s light output changed on seasonal timescales.
PERIOD CHANGES OF MIRA VARIABLES IN THE M16-M17 REGION
R. Nesci, I. Soszyński, T. Tuvikene
AbstractWe analyzed the light curves of 165 AGB variables, mostly Miras, in the sky area centered between M16 and M17 (l = 16, b = 0), using the OGLE GVS database in the IC band. Comparison with the published light curves, derived about 50 years earlier by P. Maffei using Kodak I-N photographic plates, allowed us to find no significant period changes in any star. Remarkably, a few stars of the sample appear to have substantially changed their average luminosity, the most striking case being KZ Ser. We provide a better identification for three stars: IX Ser, NSV 10522, and NSV 10326, all of them being Miras. We classify the light curves of 6 stars, discovered but not classified by Maffei, (GL Ser, NSV 10271, NSV 10326, NSV 10522, NSV 10677, and NSV 10772) five of them being new Miras, and confirm the R CrB nature of V391 Sct. The magnitude scale used by Maffei is compared to the modern IC one.
NEW SEMIREGULAR VARIABLE STAR NEAR THE WIZARD NEBULA - EVOLUTION OF THE RED GIANT "MACOMP_V1"
G. Conzo, M. Moriconi, P.G. Marotta
AbstractThe red giant MaCoMP_V1 in Cepheus at coordinates RA (J2000) 22:49:05:49 DEC (J2000) +57:52:41:6 is a semiregular variable star classified as SRS, number 2225960 in the AAVSO VSX database. Using the Fourier transform, the period P = (24.7510±0.062)d was evaluated and, with the support of the ASAS-SN and ZTF surveys, a well-defined light curve was made. The analysis resulted in the fundamental physical parameters of MaCoMP_V1, such as the mass M = (4.97±0.38)M(Sun) and radius R = (40.5±6.7)R(Sun), with consistent values suggesting the characteristics of a semiregular red giant. In addition, the effective temperature Teff = (4500±135)K from the Gaia catalog and the stellar evolution based on the Schönberg- Chandraskehar limit was estimated.
FIVE NEW FAINT CATACLYSMIC VARIABLES FROM THE ZWICKY TRANSIENT FACILITY
Ch. Lloyd, K. Bernhard
AbstractA search of faint, large-amplitude variables in the Zwicky Transient Facility data has led to the identication of five new CVs. Four of the stars, ZTFJ010013.34+610809.8, ZTFJ051913.86+293006.0, ZTFJ210441.02+394052.7 and ZTFJ210705.14+394617.7 are probbly SS Cyg-type systems, while ZTFJ173854.93+175136.3 is a likely SU UMa system.
CR DEL - LONG TERM INVESTIGATION OF PERIOD BEHAVIOUR
T. Berthold, K. Häussler, D. Hunger, B. Jacobs, J. Steingrüber
AbstractAlmost 80 years of photometric history of this RRc type variable star are presented. The period has found to be stable with a likely trend to increase typical for that type of stars.
CCD MINIMA FOR SELECTED ECLIPSING BINARIES IN 2021
AbstractThis is the 24th annual report of CCD eclipse minima timings by this observer. Here we present a total of 214 minima timings of 195 eclipsing binaries acquired in the calendar year 2021.
TIMES OF MINIMA OF THE ECLIPSING BINARY V0674 LYR
R.G. Karimov, B.M. Hafizov, O.A. Burhonov
AbstractWe present 43 times of minima for the W Ursae Majoris type eclipsing binary V0674 Lyr. The observations were obtained using the Zeiss-600 telescope at the Maidanak astronomical observatory in Uzbekistan from 2018 to 2020.
NEW CMOS PHOTOMETRY AND ARCHIVAL PHOTOGRAPHIC OBSERVATIONS OF THE W UMA STAR V752 CEN: EXTENDING THE O-C RECORD OF PERIOD CHANGES
J. Innis, D. Coates
AbstractWe present new CMOS Bayer g-band photometry of the southern W UMa star V752 Cen, presenting two new times of primary minimum, and use archival photographic photometry from the Bamberg Sky Survey (mid 1960s) and the Harvard plate collection (∼1890 to 1990) to extend the O-C diagram back in time to ∼1900. Earlier authors have reported a constant period from the earliest published photometry in 1970 to about the year 2000, when a sudden change occurred to an increasing period. The archival photographic record presented here indicates the period was effectively constant back to 1900. Our 2020 data are also consistent with reported period increase. The V752 Cen system is known from earlier work to be a W UMa binary orbiting a lower mass spectroscopic binary. Our preliminary calculations, based on the reported centre-of-mass velocity change of the W UMa binary, suggest the wide orbit may have a period near 245 d, and could give rise to a light-travel time-effect of order 0.02 d. This does not however appear to be consistent with the SuperWASP photometric O-C results. Hence we suggest that considerable uncertainty exists concerning the properties of the wide orbit.
CCD PHOTOMETRY, PERIOD ANALYSIS AND EVOLUTIONARY STATUS OF THE PULSATING VARIABLE TYC 3292-1328-1
Multi-color (BVIc) CCD-derived photometric data were acquired from TYC 3292-1328-1, a pulsating variable classified as a high amplitude δ Scuti-type (HADS) system. Analysis of precise time-series lightcurve (LC) data was accomplished using discrete Fourier transformation which revealed a mean fundamental mode (f0) of oscillation at 10.20831±0.00027 d-1 along with five other partial harmonics (2f0 and 6f0). No other statistically significant frequency shared by all bandpasses was resolved following successive pre-whitening of each residual signal. While no other times-of-maximum were found in the literature, 26 new ToMx values are reported herein. The evolutionary status, age and physical nature of TYC 3292-1328-1 were modeled using the PAdova & TRieste Stellar Evolution Code (PARSEC) for generating stellar tracks and isochrones. At this time, all available results for TYC 3292-1328-1 are consistent with its classification as a HADS variable.
VARIABILITY OF L261 IN M 13
After the discovery in April 2021 of the variability of the star L199 (now V63), belonging to the globular cluster Messier 13 (NGC 6205), between June and October 2021, we have studied twenty of the brightest stars, excluding the well-known red giant variables: surprisingly a good part of them shows some degree of variability in the range 0.05-0.25 magnitude in V band. In this work, we present light curves, average magnitudes, periods and amplitudes of the star L261 (2MASS J16413476+3627596), a red giant star located in the cluster, that we have studied using the CCD images obtained in the campaigns of 2019, 2020 and 2021, which we have joined the photometric measurements obtained by Osborn & Fuenmayor (1977), Kopacki et al. (2003), Deras et al. (2019) and ASAS-SN (from 2018 to 2021). The results suggest that this moderately bright star (average magnitude in 2021: 12.206 ± 0.027 V) is multiperiodic. It has at least two periods of different length which modulates its light curve over time: a period of variable duration (31 ± 5 days: between 26 and 36 days according to the campaign) joins another shorter (4.8 to 7.6 days) very marked in all the data sets used. With this discovery, Messier 13 now has 64 confirmed variable stars.
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.