Information Bulletin on Variable Stars

Published by Konkoly Observatory
Publications
The sky area (10 ′ × 10 ′ ) around EE Cep (reprinted from Mikolajewski et al. 2003). The blue 
EE Cep is a unique system in which a Be star is eclipsed by a dark dusty disk, making this star similar to the famous epsilon Aur in many respects. The depth and the duration of the EE Cep eclipses change to a large extent. The last two eclipses were observed in the framework of extensive international campaigns. The joint analysis of these campaigns data and historical photometry, enabled us to propose a model of this system, which implies a disk precession with a period approximately 11-12 times larger than the orbital period. This model predicts that the forthcoming eclipse should be among the deepest observed, reaching about 2 mag. The next eclipse approaches - the photometric minimum should occur around August 23, 2014. Here we would like to announce a new, third international campaign with purpose to verify the disk precession model and to put more constraints on the physical parameters of this system.
 
Kepler light curve of KIC 2835289 in time (left) and phase (right). Chromospheric activity complicates the modeling of this ellipsoidal variable, but with 4 years of uninterrupted data, the intrinsic ellipsoidal signal can be extracted to a high precision.  
KIC 2835289 is a triple stellar system that consists of an inner ellipsoidal variable with an orbital period of ~0.86 days and an outer star that eclipses the inner pair every ~750 days. Two eclipse events were observed by the Kepler mission, but they do not fully constrain our photodynamical models. The next eclipse event will occur on May 14 UT, and we solicit community involvement to follow it up from the ground. All details are available in the attached call. Please contact the authors to join the follow-up campaign.
 
ROTSEIIId daily averaged differential light curve (upper panel) and X-ray light curve (lower panel) of the Be/X-ray system V0332+53 (MJD = JD − 2400000.5). Daily averages of RXTE/ASM 5.0-15.0 keV band light curve and 15-50 keV SWIFT/BAT light curve (properly scaled and shifted) are shown. Vertical line represents PAP and arrows denote spectroscopic observation times. 
Hα profiles observed on Sep 21 and Oct 29, 2008, before and during the X-ray activity. 
We have been monitoring the binary system V0332+53 (optical counterpart is BQ Cam) since 2004 using 45 cm ROTSEIIId telescope and RTT150 (Russian-Turkish 1.5 m Telescope) located at Bakirlitepe, Antalya, Turkey. We report on the long-term variability of this system up to the present date. There exists a fading of 0.2 mag in the light of BQ Cam after MJD 53400. The fading in the light curve of BQ Cam could be due to a decrease in the density or in the size of the circumstellar disk. We present optical spectroscopic observations obtained before (at MJD 54730) and during (at MJD 54768) the new X-ray activity reported by Krimm et al. (2008). The observed Ha line profiles were single-peaked and almost symmetric. The present EW values are found to be similar to the ones observed during the fading of infrared magnitudes of Negueruela et al. (1999). Ha emission lines were found to be red-shifted by ~140 km/s which were larger than the findings of Corbet et al. (1986). We suggest that brightening of the disk after MJD 54700 may be due to the precession of the disk.
 
The average spectrum of J1321, obtained with the VATT. The strong He II emission and single-peaked lines are typical of polars.
The phase plot of the six light curves from Figure 2. Note the extreme variation near φ ∼ 0.5, as well as the phase shifts of the secondary minimum near φ ∼ 0.2 and the variable depth of the primary minimum at φ ∼ 0.7.
We present photometric and spectroscopic observations of the cataclysmic variable MASTER OT J132104.04+560957.8 which strongly indicate that it is a polar with an orbital period of 91 minutes. The optical light curve shows two maxima and two minima per orbital cycle, with considerable variation in the strength of the secondary maximum and in the morphology and depth of the minima.
 
Images of RW Aur binary in UBVRI photometric bands. The primary component RW Aur A is placed in the origin of the coordinate system.
UBVRI-photometry for A and B components of RW Aur for two epochs: the thin lines are for HST observation (Nov. 1994), the thick lines are for our observation. The dash-dotted line corresponds to the HST data shifted down by 3 m .1 and up by 0 m .7 for A and B components, respectively. The circles are obtained from HST data by applying a sum of gray extinction with ∆m = 2.87 and selective extinction with A V = 0.44 using a standard reddening curve.
Resolved UBVRI photometry of RW Aur binary was performed on November 13/14, 2014 during the deep dimming of RW Aur with a newly installed 2.5 meter telescope of the Caucasus observatory of Lomonosov Moscow State University at the mount Shatzhatmaz. At that moment RW Aur A was $\simeq 3^m$ fainter than in November 1994 in all spectral bands. We explain the current RW Aur A dimming as a result of eclipse of the star by dust particles with size $>1 \mu m.$ We found that RW Aur B is also a variable star: it was brighter than 20 years ago at $0.7^m$ in each of UBVRI band (gray brightening).
 
With the step-and-stare approach of the K2 mission, Kepler will be able to observe a large number of Cepheid an RR Lyrae stars. In this paper we describe the target selection efforts, and the first impressions based on the K2 two-wheel engineering test data. We also summarize the scientific goals that can be achieved by Kepler, including the understanding of the various additional modes and the Blazhko effect, population studies and the possibilities to observe extragalactic stars in selected campaigns.
 
Broad-band photometric and moderate-resolution spectroscopic observations of the young eruptive star V1647 Ori, obtained between 28 August and 1 September 2008, are presented. The observed magnitudes and emission line equivalent widths of the star indicate that the initial conditions of the new outburst are very similar to those of the previous one in 2004.
 
O−C diagram for EZ Lac. Empty symbols for secondary minima. 
We present several CCD minima observations of eclipsing binaries. New ephemeris is given for GSC 03881-00579 and EZ Lac........http://www.konkoly.hu/cgi-bin/IBVS?6033
 
New photometry and radial velocities of the eclipsing binary GSC 3870-01172 are reported. Si- multaneous analysis of the data using the Direct Distance Estimation method yields the absolute parameters, as well as the distance to the binary. A comparison of the distances and proper motions indicates that the nearby star GSC 3870-01361 may be a third component of the system.
 
GDS light curve in r and i with additional IPHAS, DENIS, and GSC II data points; the IPHAS error is smaller than the symbol size. 
GDS r magnitudes; the first line gives the magnitude of co-added images between 2010 and 2012.
IJK s color-color diagram: blue curve-main sequence stars; blue crosses-position of B0, A0, F0, G0, K0, M0 stars; red dashed-dotted lines-reddening paths for A V = 3.5; cyan areaexpected colors for planetary nebulae; green and purple cross-2MASS J06422218-0226285. 
We discovered the outburst of 2MASS J06422218-0226285. Between end 2012 and early 2014, this object brightened by 3 mag in r and i, and by 3.7 mag in J. Since then, it has stayed at high brightness of about 16 mag in r and 15 mag in i. Possible explanations for this kind of light curve might be a Catalysmic Variable, a Symbiotic Binary or a FUor or EXor type Young Stellar Object. The color properties favor an outbursting Young Stellar Object.
 
GDS J0702414-023501 on archival sky survey plates (position of the star is indicated). The captions provide information on emulsions and filters used, as well as the epoch the plate was taken.  
(J − H) vs. (H − K s ) diagram, indicating the positions of GDS J0702414-023501 (red and green dots) and several confirmed RCB variables (open symbols), Mira variables (filled symbols) and the RV Tauri star UY Ara (cross). See text for details.  
(W 2 − W 3) vs. (W 3 − W 4) diagram, indicating the positions of GDS J0702414-023501 (red and green dots) and several confirmed RCB variables (open symbols), Mira variables (filled symbols) and the RV Tauri star UY Ara (cross). See text for details.  
Spectral energy distribution of GDS J0702414-023501, based on data from various catalogues, as indicated in the inset legend. The solid line indicates a polynomial fit of 6th order.  
The GDS light and colour curves of GDS J0702414-023501, based on recent, newly reduced and as yet unpublished GDS data (M. Hackstein, private communication). Red and black dots indicate, respectively, GDS i ′ and r ′ data.
2MASS J07024146-0235017 = GDS J0702414-023501 was included in the "Catalogue enriched with R CrB stars" on grounds of its near- and mid-infrared colours. The object, which corresponds to the carbon star IRAS 07001-0230 = CGCS 6197, has been found to exhibit large amplitude variability in its Bochum Galactic Disk Survey light curve. Taking into account all available data, GDS J0702414-023501 is here proposed as a new candidate Mira star.
 
We present 105 times of minima of 33 eclipsing binaries.
 
We have performed a new search for DPVs of short period in the ASAS catalog (Pojmanski, G., 1997), focusing on those stars with orbital periods between 2 to 3 days which also show variations in their brightness. From a total of 244 objects, we have found another candidate to DPV, one whose mean brightness is gradually decreasing. By fitting a 3rd order polynomial to the mean magnitude and then moving it to zero for a second analysis, a gradual decrease over 2500 days was revealed. During the last 1000 days of this decrease, a 42% increase in the variation between the minimum and maximum values of the magnitude was observed. We determined the orbital period by using the PDM IRAF software (Stellingwerf 1978) and estimated the errors for the orbital period and long cycle by visual inspection of the light curves phased with trial periods near the minimum of the periodogram given by PDM.
 
We present 114 times of minima of 6 ultra-short orbital period eclipsing binaries.
 
Spectroscopic results of HU Tauri that I presented in my Ph.D thesis (Parthasarathy 1979) are published in this paper. The H-alpha line of the secondary is detected. The detection of H-alpha line of the secondary is confirmed based on the high resolution Coude Reticon spectra obtained with the 2.1-m telescope of the McDonald observatory.
 
We present the second part of a new Name-List of variable stars containing information on 2161 variable stars recently designated in the system of the General Catalogue of Variable Stars. With the exception of unusual variables named upon request from the IAU CBAT or for other reasons, these stars are in the range of J2000.0 right ascensions from 6 to 16 hours.
 
We report the discovery of 2 previously undetected pulsation frequencies in the known roAp star HD 177765. Photometric observations by the Kepler space telescope during K2 Campaign 7 show low-amplitude pulsations (4-11 micro mag) previously unseen in photometry. We show the pulsations to be stable over the observation period, and demonstrate that the separation of the frequencies is not representative of the large frequency separation quantity needed to perform asteroseismic analysis.
 
The Puppis field was observed between 2011 and 2014 in the search for transitingextrasolar planets. To characterize the field, an automatic variable search was applied asdescribed by Fruth et al. (2012). With the automatic procedure 1829 new variables werediscovered and 26 previously known variables were confirmed (Dreyer et al. 2018). Beyond this work, the data was also analysed for potential transitevents by the Box-Fitting Least Square (BLS) method (Kovac et al. 2002, Fruth et al.2013). This yieldeda list of objects with tentative period, duration and depth, not included in the list ofDreyer et al (2018). The light curves of these potential candidates were visually inspectedand further modelled by TLCM, a transit light curve model to get thebasic parameters,developed by Csizmadia (2020). Thereby the period was confirmed or improved andthe type of binary was determined. Identification and variability data for the stars aresummarized in Tables 1–2; phase curves for each variable are presented in Figures 1–18.Photometry data files are also available online.
 
We present new transit observations acquired between 2014 and 2018 for the hot exoplanets GJ 436 b, HAT-P-3 b, HAT-P-19 b, WASP-3 b, and XO-2 b. New mid-transit times extend the timespan covered by observations of these exoplanets and allow us to refine their transit ephemerides. All new transits are consistent with linear ephemerides.
 
Optical (BVRI) and infrared (JHK) photometry of the gamma-ray nova Nova Sco 2012 (V1324 Sco) is presented and the lightcurve reconstructed and discussed. An interstellar reddening E(B-V)=1.23 is derived. Dust begun to form at an early date in the nova, only one magnitude down and 20 days past maximum optical brightness and caused an extinction of at least 6 magnitudes in V band, that cleared some months later. This unusual early dust formation compromises the application of the magnitude at maximum versus rate of decline (MMRD) relations in estimating the distance to the nova.
 
We present our photometric results of OV Boo obtained during the 2017 outburst.
 
The spectroscopic and photometric variability of CGCS 6107 has been studied with four telescopes from 2015 to 2018. The star varied between R=11.4 and 14.2 mag with a time scale of ~500 days. An appreciable color variation was observed, the star being bluer when brighter. Hα emission was present around maxima. The spectrum is that of an N type giant veiled by a variable dusty envelope.
 
We present the special Name-List of variable stars containing information on 1270 variable stars recently designated in the system of the General Catalogue of Variable Stars, which are mostly former suspected variables from the NSV catalogue.
 
The nightly residual light variations of BD Vir (dots). Solid line is a two frequency fit to the data.
The "Thai Sky Survey for oEA Stars" (THASSOS) project is focused on searching for and studies of new mass-accreting pulsating components of a semi-detached Algoltype systems, so called class of oEA stars suggested by Mkrtichian et al. (2002, 2004). oEA components of binaries have been evolved into the instability strip after the first high- mass transfer stage and show δ Sct-like oscillations like classical δ Sct-type stars in well detached eclipsing binary systems, without any history of mass transfer. BD Vir is a 2.548572-day semi-detached Algol type eclipsing binary system with an A8V primary component, showing long-term orbital period variation (Kreiner, 2004). The new CCD photometric observations for BDVir were obtained during 4 nights (February 13, March 13, 31 and April 20, 2017) using the 0.5m telescope of Thai National Observatory in Thailand. All observations were made at the orbital phase interval 0.45- 0.72. Johnson B-filter was used, exposures varied from 20 to 80 seconds depending on seeing and the weather conditions. All stars in the field of view were reduced by SExtractor and the Python written codes for differential photometry. Exposures were binned by 4 points to get a better accuracy. The comparison star TYC 6120-50-1 (RA = 13h27m16.s245 DEC= -16°07'45.''85) was used. Pulsational variations were searched for in the out-of-eclipse parts of the light curve after removal of slow orbital light variations using the low order polynomial fits. Residual light curves are shown in Figure 1. We searched for periodic variations in the residual data by using the Period04 software (Lenz & Breger, 2005). We applied the Discrete Fourier Transforms (DFT) and the signal pre-whitening techniques for consecutive detection of signals in the data. Steps of DFT analyses and consecutive pre-whitenings of found frequencies are shown in Figure 2 from top to bottom. We detected two pulsation frequencies at 34.159 c/d and 29.735 c/d. Frequencies, amplitudes of oscillations and their accuracies are listed in Table 1. Conclusion: We discovered short-period pulsational light oscillations in a primary massaccreting component of the semi-detached eclipsing binary system BD Vir. We conclude, that BD Vir is a new member of oEA group of pulsators suggested by Mkrtichian et al. (2002, 2004).
 
Top-cited authors
Ángel Arenas Soní
  • Universidad Nacional Autónoma de México
Keny Vargas
  • Universidad de Monterrey
Oriana Trejo
Hugo Huepa
  • Universidad Nacional Autónoma de México
J. H. Pena
  • Universidad Nacional Autónoma de México