- ID:
- ivo://CDS.VizieR/J/AJ/143/101
- Title:
- The classification of Kepler B-star variables
- Short Name:
- J/AJ/143/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The light curves of 252 B-star candidates in the Kepler database are analyzed in a similar fashion to that done by Balona et al. (2011MNRAS.413.2403B) to further characterize B-star variability, increase the sample of variable B stars for future study, and to identify stars whose power spectra include particularly interesting features such as frequency groupings. Stars are classified as either constant light emitters, {beta} Cep stars, slowly pulsating B stars (SPBs), hybrid pulsators, binaries or stars whose light curves are dominated by rotation (Bin/Rot), hot subdwarfs, or white dwarfs. One-hundred stars in our sample were found to be either light constants or to be variable at a level of less than 0.02mmag. We increase the number of candidate B-star variables found in the Kepler database by Balona et al. (2011MNRAS.413.2403B) in the following fashion: {beta} Cep stars from 0 to 10, SPBs from eight to 54, hybrid pulsators from seven to 21, and Bin/Rot stars from 23 to 82. For comparison purposes, approximately 51 SPBs and six hybrids had been known prior to 2007. The number of {beta} Cep stars known prior to 2004 was 93. A secondary result of this study is the identification of an additional 11 pulsating white dwarf candidates, four of which possess frequency groupings.
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Search Results
- ID:
- ivo://CDS.VizieR/J/other/OEJV/185
- Title:
- The Czech Variable Star Catalogue
- Short Name:
- J/other/OEJV/185
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We present the first release of the Czech Variable star catalogue that currently contains 1228 stars whose variability was discovered by 60 Czech observers. The catalogue contains confirmed variable stars of various types, but also candidates. We give precise coordinates, cross identification with other catalogues, information about constellation, variability type, brightness, light elements, name of the discoverer and year of discovery. In eighty-eight percent of stars the variability type is estimated, for more than 60% of the stars the light ephemerides are given.
- ID:
- ivo://CDS.VizieR/J/A+A/363/L1
- Title:
- The distance modulus of the LMC
- Short Name:
- J/A+A/363/L1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use double-mode RR Lyrae (RRd) stars from the MACHO variable star database of the Large Magellanic Cloud (LMC) to estimate its distance, by utilizing photometric data, linear pulsation and stellar atmosphere models. If we set E_(B-V)_=0.11 and [M/H]=-1.5 for LMC, we get M-m=18.52mag. The fact that the distance moduli obtained in this and in our former studies of cluster RRd and Small Magellanic Cloud beat Cepheids agree so well, implies that the only serious source of error is the zero point of the temperature scale, which should not have larger than +/-0.10mag effect on the distance modulus.
- ID:
- ivo://CDS.VizieR/J/AJ/155/116
- Title:
- The globular cluster M14.II. Variable stars
- Short Name:
- J/AJ/155/116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present time-series BVI photometry for the Galactic globular cluster NGC 6402 (M14). The data consist of ~137 images per filter, obtained using the 0.9 and 1.0 m SMARTS telescopes at the Cerro Tololo Inter-American Observatory. The images were obtained during two observing runs in 2006-2007. The image-subtraction package ISIS, along with DAOPHOT II/ALLFRAME, was used to perform crowded-field photometry and search for variable stars. We identified 130 variables, eight of which are new discoveries. The variable star population is comprised of 56 ab-type RR Lyrae stars, 54 c-type RR Lyrae, 6 type II Cepheids, 1 W UMa star, 1 detached eclipsing binary, and 12 long-period variables. We provide Fourier decomposition parameters for the RR Lyrae, and discuss the physical parameters and photometric metallicity derived therefrom. The M14 distance modulus is also discussed, based on different approaches for the calibration of the absolute magnitudes of RR Lyrae stars. The possible presence of second-overtone RR Lyrae in M14 is critically addressed, with our results arguing against this possibility. By considering all of the RR Lyrae stars as members of the cluster, we derive <P_ab_>=0.589 days. This, together with the position of the RR Lyrae stars of both Bailey types in the period-amplitude diagram, suggests an Oosterhoff-intermediate classification for the cluster. Such an intermediate Oosterhoff type is much more commonly found in nearby extragalactic systems, and we critically discuss several other possible indications that may point to an extragalactic origin for this cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/156/186
- Title:
- The High Cadence Transit Survey (HiTS)
- Short Name:
- J/AJ/156/186
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The High Cadence Transient Survey (HiTS) aims to discover and study transient objects with characteristic timescales between hours and days, such as pulsating, eclipsing, and exploding stars. This survey represents a unique laboratory to explore large etendue observations from cadences of about 0.1 days and test new computational tools for the analysis of large data. This work follows a fully data science approach, from the raw data to the analysis and classification of variable sources. We compile a catalog of ~15 million object detections and a catalog of ~2.5 million light curves classified by variability. The typical depth of the survey is 24.2, 24.3, 24.1, and 23.8 in the u, g, r, and i bands, respectively. We classified all point-like nonmoving sources by first extracting features from their light curves and then applying a random forest classifier. For the classification, we used a training set constructed using a combination of cross-matched catalogs, visual inspection, transfer/active learning, and data augmentation. The classification model consists of several random forest classifiers organized in a hierarchical scheme. The classifier accuracy estimated on a test set is approximately 97%. In the unlabeled data, 3485 sources were classified as variables, of which 1321 were classified as periodic. Among the periodic classes, we discovered with high confidence one {delta} Scuti, 39 eclipsing binaries, 48 rotational variables, and 90 RR Lyrae, and for the nonperiodic classes, we discovered one cataclysmic variable, 630 QSOs, and one supernova candidate.
- ID:
- ivo://CDS.VizieR/J/A+A/630/A92
- Title:
- The Hubble Catalog of Variables
- Short Name:
- J/A+A/630/A92
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hubble Catalog of Variables (HCV) is the first full, homogeneous, catalog of variable sources found in the Hubble Source Catalog (HSC), which is built out of publicly available images obtained with the WFPC2, ACS and WFC3 instruments onboard the Hubble Space Telescope. The HCV is the deepest catalog of variables available. It includes variable stars in our Galaxy and nearby galaxies, as well as transients and variable active galactic nuclei. The HCV contains 84428 candidate variable sources (out of 3.7 million HSC sources that were searched for variability) with V<=27mag; for 11115 of them the variability is detected in more than one filter. The data points in a light curve range from 5 to 120, the time baseline ranges from under a day to over 15 years, while ~8% of variables have amplitudes in excess of 1mag.
- ID:
- ivo://CDS.VizieR/J/ApJS/193/26
- Title:
- The M33 synoptic stellar survey. I.
- Short Name:
- J/ApJS/193/26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have conducted a ground-based BVI synoptic survey of the Local Group galaxy M33 which covers most of its disk and spans a period of 7 years. The survey targets luminous, long-period variables such as Cepheids and Miras and combines images from the DIRECT project and follow-up observations at the WIYN 3.5m telescope. This paper, the first in a series, presents the discovery and characterization of 564 Cepheid variables, which represent a factor of two increase over previous samples with calibrated point-spread function (PSF) photometry. We also describe the details of the observations and analysis of the survey data, including the use of archival Hubble Space Telescope images to characterize biases in our ground-based PSF photometry.
- ID:
- ivo://CDS.VizieR/J/AJ/153/170
- Title:
- The M33 Synoptic Stellar Survey. II. Mira variables
- Short Name:
- J/AJ/153/170
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the discovery of 1847 Mira candidates in the Local Group galaxy M33 using a novel semi-parametric periodogram technique coupled with a random forest classifier. The algorithms were applied to ~2.4*10^5^ I-band light curves previously obtained by the M33 Synoptic Stellar Survey. We derive preliminary period-luminosity relations at optical, near-infrared, and mid-infrared wavelengths and compare them to the corresponding relations in the Large Magellanic Cloud.
- ID:
- ivo://CDS.VizieR/J/A+AS/139/135
- Title:
- The Optical Spectrum of RR Tel
- Short Name:
- J/A+AS/139/135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The symbiotic nova RR Telescopii has been observed with the 3.9 m telescope at the Anglo-Australian Observatory (AAO), using the University College London Echelle Spectrograph (UCLES) in conjunction with a Tek CCD. It displays a rich emission line spectrum, ranging in excitation from NI to NiVIII. We present a list of 811 measured lines, with their suggested identifications and absolute line intensities, covering a wavelength range from 3180 to 9455 A. The absolute line intensities have been derived by comparing the high resolution data with a flux-calibrated low resolution spectrum taken with the Australian National University 2.3 m telescope. All of the lines have been successfully identified. Comparing our results with those of previous studies indicates that the RR Tel system is advancing towards higher degrees of ionisation.
- ID:
- ivo://CDS.VizieR/J/ApJ/841/84
- Title:
- Theoretical framework for RR Lyrae. II. MIR data
- Short Name:
- J/ApJ/841/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new theoretical period-luminosity-metallicity (PLZ) relations for RR Lyrae stars (RRLs) at Spitzer and WISE wavelengths. The PLZ relations were derived using nonlinear, time-dependent convective hydrodynamical models for a broad range of metal abundances (Z=0.0001-0.0198). In deriving the light curves, we tested two sets of atmospheric models and found no significant difference between the resulting mean magnitudes. We also compare our theoretical relations to empirical relations derived from RRLs in both the field and in the globular cluster M4. Our theoretical PLZ relations were combined with multi-wavelength observations to simultaneously fit the distance modulus, {mu}0, and extinction, A_V_, of both the individual Galactic RRL and of the cluster M4. The results for the Galactic RRL are consistent with trigonometric parallax measurements from Gaia's first data release. For M4, we find a distance modulus of {mu}0=11.257+/-0.035mag with A_V_=1.45+/-0.12mag, which is consistent with measurements from other distance indicators. This analysis has shown that, when considering a sample covering a range of iron abundances, the metallicity spread introduces a dispersion in the PL relation on the order of 0.13mag. However, if this metallicity component is accounted for in a PLZ relation, the dispersion is reduced to ~0.02mag at mid-infrared wavelengths.
