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Proceedings of the 41st Conference on Variable Stars Research
2010
In November 2009, another national conference on variable stars, stellar astrophysics in general and on extrasolar planets was organised by Variable Star and Exoplanet section of Czech Astronomical Society. The conference was held in beautiful and one of the oldest observatory in Czech republic - Stefanik Observatory in Prague. Our conferences on variable star research provide unique opportunities for meetings between professional and amateur astronomers and have become a crucial platform for exchanging information and sharing knowledge. These events help to keep the local astronomical community alive and active. This years conference was held on a weekend from November 27 to November 29. All almost 40 participants were able to witness the richness of our field and the joy that research on variable stars brings to our lifes.
COMMISSIONS 27 AND 42 OF THE IAU INFORMATION BULLETIN ON VARIABLE STARS
Apogee ALTA U47+ CCD camera. 1024 x 1024 pixels. Method of data reduction: Reduction of the CCD frames and differential photometry were performed with the standard tasks of IRAF 1 package Method of minimum determination: The minima times of eclipsing binaries were calculated using Kwee & van Woerden's (1956) method. Mid-transit times were calculated by making use of a model-fitting algorithm available via the Exoplanet Transit Database (Poddaný et al. 2010) 2. † Based on the observations performed at Ankara University Kreiken Observatory 1 IRAF is distributed by the National Optical Astronomical Observatories, operated by the Association of the Universities for Research in Astronomy, inc., under cooperative agreement with the National Science Foundation 2 http://var2.astro.cz/ETD/
The Exciting Star of the Berkeley 59/Cepheus OB4 Complex and Other Chance Variable Star Discoveries
Arxiv preprint arXiv: …, 2008
A study is presented regarding the nature of several variable stars sampled during a campaign of photometric monitoring from the Abbey Ridge Observatory: 3 eclipsing binaries, 2 semiregulars, a luminous Be star, and a star of uncertain classification. For one of the eclipsing systems, BD+66°1673, spectroscopic observations reveal it to be an O5 V((f))n star and the probable ionizing star of the Berkeley 59/Cep OB4 complex. An analysis of spectroscopic observations and BV photometry for Berkeley 59 members in conjunction with published observations imply a cluster age of ~2 Myr, a distance of d = 883 ±43 pc, and a reddening of E B-V =1.38 ±0.02. Two of the eclipsing systems are Algol-type, but one appears to be a cataclysmic variable associated with an X-ray source. ALS 10588, a B3 IVn star associated with the Cepheid SV Vul, is of uncertain classification, although consideration is given to it being a slowly pulsating B star. The environmental context of the variables is examined using spectroscopic parallax, 2MASS photometry, and proper motion data, the latter to evaluate the membership of the variable B2 Iabe star HDE 229059 in Berkeley 87, an open cluster that could offer a unique opportunity to constrain empirically the evolutionary lineage of young massive stars. Also presented are our null results for observations of a sample of northern stars listed as Cepheid candidates in the Catalogue of Newly Suspected Variables. deductions to be made concerning a Cepheid's intrinsic reddening and pulsation mode, and offer yet another diagnostic tool for establishing Cepheids as members of open clusters, such calibrators being the foundation for the extragalactic distance scale (Turner and Burke 2002). The photometric signatures of some variable stars can be sufficiently ambiguous that spectroscopic follow-up was necessary to resolve the true nature of the light variations. Preliminary results for the best-studied of the variables, summarized in Table 1, are presented here in order of increasing right ascension. The results for the NSV stars are given at the end. 2. Observations and Equipment The ARO is located in Stillwater Lake, a community ~23 km west of Halifax, Nova Scotia, Canada. The ARO allocates ~2 hours of observing time on each clear night to variable star research, with much of the remainder being used to search for extragalactic supernovae as part of the Puckett Observatory Supernova Search program. The site is quite dark, with typical Sky Quality Meter readings of 20.6 V mag. arcsec-2 on good nights. The observatory houses a 28-cm Celestron Schmidt-Cassegrain telescope equipped with an SBIG ST9-CCD camera and Bessel B and V filters. The facility is remotely accessible and completely automated, allowing unattended acquisition of astronomical and calibration images and providing a software pipeline that calibrates, combines, and performs differential aperture photometry. Much of the design and software development to realize the ARO's capability was completed in the form of the Abbey Ridge Auto-Pilot software (Lane 2007). Other software, in particular MaxIm DL/CCD (George 2007), provides many of the low-level image acquisition and processing functions. Observations and image processing are guided by two data files provided by the observer. The first contains relevant information about each field to be imaged, including a unique identifier, center equatorial coordinates , and exposure times and number of exposures to be taken in each filter. If aperture photometry is to be performed automatically on the field, additional information is needed, including aperture photometry parameters, magnitude of the designated reference star, and equatorial coordinates for each star to be measured. The second file type contains a list of target fields (identifiers) to be observed on a given night. All resulting photometric data represent means for multiple (15-25, or more) short-exposure images, typically of 1 to 60 seconds duration, taken in immediate succession, combined using a noise-reduction algorithm developed by DJL. The algorithm first calibrates the individual images instrumentally, then registers them spatially using stars in the field. The mean and standard deviation are computed for each pixel position in the stack of images. Pixels on a given image that deviate more than a specified number of standard deviations from the mean of pixels at the same pixel positions on the other images are rejected, and a new mean is computed. The process is iterated up to five times until all deviant pixels are rejected, although no more than 30% of the pixels at a given pixel position are ever rejected. The resulting mean, without inclusion of rejected pixels, is used to form the combined image, which is plate-solved astrometrically using the PinPoint Astrometric Engine software (Denny 2007). Differential aperture photometry is performed on each combined image using initial aperture and sky annulus parameters, and equatorial coordinates of the primary target star, reference star, and any number of "check" or other stars. The sky annulus radius and size are pre-selected for each field to be appropriate for all stars measured. The equatorial position of each star is converted to its corresponding X and Y pixel position using the plate solution embedded in the fts header. Aperture photometry is performed on the reference star 3 times iteratively to
Short term period variable stars observed at OAUNI
2019
We present the first scientific results of the program on short term period variable stars observed using the OAUNI facility at the peruvian Andes. These results include good quality light curves of delta Scuti stars, rapidly oscillating stars along with eclipsing and cataclysmic binaries. The photometric precision reached by the available instrumental and equipment, and used in the several scientific subprograms, has satisfied the initial expectations.
GSC 4560–02157: a new long-period eclipsing cataclysmic variable star
Research in Astronomy and Astrophysics, 2015
We study the newly discovered variable star GSC 4560-02157. CCD photometry was performed in 2013-2014, and a spectrum was obtained with the 6-m telescope in June, 2014. GSC 4560-02157 is demonstrated to be a short-period (P = 0.265359 d) eclipsing variable star. All its flat-bottom primary minima are approximately at the same brightness level, while the star's out-of-eclipse brightness and brightness at secondary minimum varies considerably (by up to 0.6 m) from cycle to cycle. Besides, there are short-term (time scale of 0.03-0.04 days) small-amplitude brightness variations out of eclipse. This behavior suggests cataclysmic nature of the star, confirmed with a spectrum taken on June 5, 2014. The spectrum shows numerous emissions of the hydrogen Balmer series, HeI, HeII.
Four New Variable Stars in Ophiuchus
Four new variable stars were discovered by serendipity in the Ophiuchus constellation during photometric analysis of the NEO Asteroid (1988 PA), pictures taken in July 2010 from A81 Balzaretto Observatory in Rome. Based on their light curves and colour indexes, the stars were classified in their variable class and registered in the Variable Star Index (VSX) hosted in the AAVSO web site, respectively as one eclipsing variable EA-type or short period eclipsing subgroup of RS CVn-type (UCAC3 196-166827), identified as the optical counterpart of 1RXS J180755.7+074717 X-ray source, two eclipsing binaries EW-type (UCAC3 196-166958 and UCAC3 196-167279) and one very likely as pulsating variable High Amplitude δ Scuti type (HADS) or SX Phe (UCAC3 196-167073).
Serendipitous observations of UCAC4 686-012519: a short period δ Scuti pulsating star in Andromeda
BAA Variable Star Section Circular, 2020
Serendipitous observations are reported of UCAC4 686-012519 (= ZTF J020549.65+470041.0 = ASASSN-V J020549.64+470040.9) that were made whilst observing transits of the exoplanet HAT-P-32 b using the MicroObservatory. The observations demonstrate the value of MicroObservatory for observing a known transiting exoplanet for ephemeris maintenance whilst simultaneously characterising the stellar variability of another star, and support the findings by the Zwicky Transient Facility and the All-Sky Automated Survey for Supernovae that UCAC4 686-012519 is a δ Scuti variable with a period of ~103 min and an amplitude of ~0.1 mag.
Monthly Notices of the Royal Astronomical Society, 2016
We present photometric and spectroscopic follow-up observations of short-period variables discovered in the OmegaWhite survey, a wide-field high-cadence g-band synoptic survey targeting the Galactic Plane. We have used fast photometry on the SAAO 1.0-and 1.9-m telescopes to obtain light curves of 27 variables, and use these results to validate the period and amplitude estimates from the OmegaWhite processing pipeline. Furthermore, 57 sources (44 unique, 13 with new light curves) were selected for spectroscopic follow-up using either the SAAO 1.9-m telescope or the Southern African Large Telescope. We find that many of these variables have spectra which are consistent with being δ Scuti-type pulsating stars. At higher amplitudes, we detect four possible pulsating white dwarf/subdwarf sources and an eclipsing cataclysmic variable. Due to their rarity, these targets are ideal candidates for detailed followup studies. From spectroscopy, we confirm the symbiotic binary star nature of two variables identified as such in the SIMBAD database. We also report what could possibly be the first detection of the 'Bump Cepheid' phenomena in a δ Scuti star, with OW J175848.21-271653.7 showing a pronounced 22 per cent amplitude dip lasting 3 min during each pulsational cycle peak. However, the precise nature of this target is still uncertain as it exhibits the spectral features of a B-type star.
CCD photometry of the cataclysmic variable star V425 Cas in 2006-2007
2009
We studied the photometric behavior of the cataclysmic variable V425 Cas using CCD observations with the telescopes at Rozhen NAO and Belogradchik AO. The changes of the star magnitude were determined during the period of observations from June 2006 to September 2007 in the bands B and V. Two respective light curves are presented. There were two nights with simultaneous observations in the bands B and I and the corresponding light curves are plotted too. We found correlation between the colours (B-I) and B and the corresponding fluxes.