Identification of new cataclysmic variables in the 1RXS and USNO-B1.0 catalogs

Денисенко, Д.; Sokolovsky, K. V.

doi:10.1134/s1063773711010038

Cited by 19 publications

(17 citation statements)

References 17 publications

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“…Also selected as a new CV from the ROSAT catalog, 1RXS2223+07 presents a DN light curve with outbursts 2 mag above the average 19.5 mag quiescent level (Denisenko & Sokolovsky 2011). Our spectrum presents broad Balmer and He I emission lines, besides He II 4686Å, on a slightly red continuum, consistent with a DN spectrum.…”

Section: Rxs2223+07 (1rxs J2223356+074515 = Usno-b10 0977-0743560)mentioning

confidence: 68%

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Exploratory Spectroscopy of Magnetic Cataclysmic Variables Candidates and Other Variable Objects

Oliveira¹,

Rodrigues²,

Cieslinski³

et al. 2017

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The increasing number of synoptic surveys made by small robotic telescopes, such as the photometric Catalina Real-Time Transient Survey (CRTS), represents a unique opportunity for the discovery of variable sources and improves the statistical samples of such classes of objects. Our goal is the discovery of magnetic Cataclysmic Variables (mCVs). These are rare objects, which probe interesting accretion scenarios controlled by the white dwarf magnetic field. In particular, improved statistics of mCVs would help to address open questions on their formation and evolution. We performed an optical spectroscopy survey to search for signatures of magnetic accretion in 45 variable objects selected mostly from the CRTS. In this sample we found 32 CVs, 22 being mCV candidates from which 13 are previously unreported as such. If the proposed classifications are confirmed, it would represent an increase of 4% in the number of known polars and 12% in the number of known IPs. A fraction of our initial sample was classified as extragalactic sources or other types of variable stars by the inspection of the identification spectra. Despite the inherent complexity in identifying a source as a mCV, variability-based selection followed by spectroscopic snapshot observations has proved to be an efficient strategy for their discoveries, being a relatively inexpensive approach in terms of telescope time.

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Section: Rxs2223+07 (1rxs J2223356+074515 = Usno-b10 0977-0743560)mentioning

confidence: 68%

“…= USNO-B1.0 1103-0421031) This is another CV discovered by Denisenko & Sokolovsky (2011) among X-ray sources in the ROSAT catalog . It was classified as a possible dwarf nova by its X-ray hardness ratio.…”

Section: Rxs1929+20 (1rxs J1929266+202038mentioning

confidence: 91%

Exploratory Spectroscopy of Magnetic Cataclysmic Variables Candidates and Other Variable Objects

Oliveira¹,

Rodrigues²,

Cieslinski³

et al. 2017

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“…This is accomplished even if good filtering is performed to remove image artefacts, cosmic ray hits, and point spread function (PSF) wings of a bright nearby objects (e.g. Fruchter & Hook 2002;Bernard et al 2010;Denisenko & Sokolovsky 2011;Ramsay et al 2014;Desai et al 2016). This is because stochastic and non-stochastic variations do not look that different from the viewpoint of statistical and correlated indices, especially for low signal-to-noise data.…”

Section: Summary Of Recommendationsmentioning

confidence: 99%

New insights into time series analysis

Lopes

Cross

2017

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Context. Statistical parameters are used to draw conclusions in a vast number of fields such as finance, weather, industrial, and science. These parameters are also used to identify variability patterns on photometric data to select non-stochastic variations that are indicative of astrophysical effects. New, more efficient, selection methods are mandatory to analyze the huge amount of astronomical data. Aims. We seek to improve the current methods used to select non-stochastic variations on non-correlated data. Methods. We used standard and new data-mining parameters to analyze non-correlated data to find the best way to discriminate between stochastic and non-stochastic variations. A new approach that includes a modified Strateva function was performed to select non-stochastic variations. Monte Carlo simulations and public time-domain data were used to estimate its accuracy and performance. Results. We introduce 16 modified statistical parameters covering different features of statistical distribution such as average, dispersion, and shape parameters. Many dispersion and shape parameters are unbound parameters, i.e. equations that do not require the calculation of average. Unbound parameters are computed with single loop and hence decreasing running time. Moreover, the majority of these parameters have lower errors than previous parameters, which is mainly observed for distributions with few measurements. A set of non-correlated variability indices, sample size corrections, and a new noise model along with tests of different apertures and cut-offs on the data (BAS approach) are introduced. The number of mis-selections are reduced by about 520% using a single waveband and 1200% combining all wavebands. On the other hand, the even-mean also improves the correlated indices introduced in Paper I. The mis-selection rate is reduced by about 18% if the even-mean is used instead of the mean to compute the correlated indices in the WFCAM database. Even-statistics allows us to improve the effectiveness of both correlated and non-correlated indices. Conclusions. The selection of non-stochastic variations is improved by non-correlated indices. The even-averages provide a better estimation of mean and median for almost all statistical distributions analyzed. The correlated variability indices, which are proposed in the first paper of this series, are also improved if the even-mean is used. The even-parameters will also be useful for classifying light curves in the last step of this project. We consider that the first step of this project, where we set new techniques and methods that provide a huge improvement on the efficiency of selection of variable stars, is now complete. Many of these techniques may be useful for a large number of fields. Next, we will commence a new step of this project regarding the analysis of period search methods.

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“…This object (hereafter 1RXS J185310) was originally selected as a variable optical counterpart of a ROSAT X-ray source (Denisenko & Sokolovsky 2011). The designation DDE 14 was also given (Denisenko 2011 …”

Section: Rxs J1853100+594509mentioning

confidence: 99%

Survey of period variations of superhumps in SU UMa-type dwarf novae. VII. The seventh year (2014–2015)

Katô

Hambsch

Dubovský

et al. 2015

Publications of the Astronomical Society of Japan

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Continuing the project described by Kato et al. (2009, PASJ, 61, S395), we collected times of superhump maxima for 102 SU UMa-type dwarf novae, observed mainly during the 2014-2015 season, and characterized these objects. Our project has greatly improved the statistics of the distribution of orbital periods, which is a good approximation of the distribution of cataclysmic variables at the terminal evolutionary stage, and has confirmed the presence of a period minimum at a period of 0.053 d and a period spike just above this period. The number density monotonically decreased toward the longer period and there was no strong indication of a period gap. We detected possible negative superhumps in Z Cha. It is possible that normal outbursts are also suppressed by the presence of a disk tilt in this system. There was no indication of enhanced orbital humps just preceding the superoutburst, and this result favors the thermal-tidal disk instability as the origin of superoutbursts. We detected superhumps in three AM CVn-type dwarf novae. Our observations and recent other detections suggest that 8% of objects showing dwarf nova-type outbursts are AM CVn-type objects. AM CVn-type objects and EI Psc-type objects may be more abundant than previously recognized. OT J213806, a WZ Sge-type object, exhibited remarkably different features between the 2010 and 2014 superoutbursts. Although the 2014 superoutburst was much fainter, the plateau phase was shorter than the 2010 one, and the course of the rebrightening phase was similar. This object indicates that the O − C diagrams of superhumps can indeed be variable, at least in WZ Sge-type objects. Four deeply eclipsing SU UMa-type dwarf novae (ASASSN-13cx, ASASSN-14ag, ASASSN15bu, and NSV 4618) were identified. We studied long-term trends in supercycles in MM Hya and CY UMa and found systematic variations of supercycles of ∼20%.

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Identification of new cataclysmic variables in the 1RXS and USNO-B1.0 catalogs

Cited by 19 publications

References 17 publications

Exploratory Spectroscopy of Magnetic Cataclysmic Variables Candidates and Other Variable Objects

Exploratory Spectroscopy of Magnetic Cataclysmic Variables Candidates and Other Variable Objects

New insights into time series analysis

Survey of period variations of superhumps in SU UMa-type dwarf novae. VII. The seventh year (2014–2015)

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