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801. RR Lyrae candidates in VVV
ID:
ivo://CDS.VizieR/J/A+A/642/A58
Title:
RR Lyrae candidates in VVV
Short Name:
J/A+A/642/A58
Date:
21 Oct 2021
Publisher:
CDS
Description:
The creation of a 3D map of the bulge using RR Lyrae (RRL) is one of the main goals of the VISTA Variables in the Via Lactea Survey (VVV) and VVV(X) surveys. The overwhelming number of sources undergoing analysis undoubtedly requires the use of automatic procedures. In this context, previous studies have introduced the use of machine learning (ML) methods for the task of variable star classification. Our goal is to develop and test an entirely automatic ML-based procedure for the identification of RRLs in the VVV Survey. This automatic procedure is meant to be used to generate reliable catalogs integrated over several tiles in the survey. Following the reconstruction of light curves, we extracted a set of period- and intensity-based features, which were already defined in previous works. Also, for the first time, we put a new subset of useful color features to use. We discuss in considerable detail all the appropriate steps needed to define our fully automatic pipeline, namely: the selection of quality measurements; sampling procedures; classifier setup, and model selection. As a result, we were able to construct an ensemble classifier with an average recall of 0.48 and average precision of 0.86 over 15 tiles. We also made all our processed datasets available and we published a catalog of candidate RRLs. Perhaps most interestingly, from a classification perspective based on photometric broad-band data, our results indicate that color is an informative feature type of the RRL objective class that should always be considered in automatic classification methods via ML. We also argue that recall and precision in both tables and curves are high-quality metrics with regard to this highly imbalanced problem. Furthermore, we show for our VVV data-set that to have good estimates, it is important to use the original distribution more abundantly than reduced samples with an artificial balance. Finally, we show that the use of ensemble classifiers helps resolve the crucial model selection step and that most errors in the identification of RRLs are related to low-quality observations of some sources or to the increased difficulty in resolving the RRL-C type given the data.
802. RR Lyrae cand. in the Galactic Center
ID:
ivo://CDS.VizieR/J/ApJ/863/79
Title:
RR Lyrae cand. in the Galactic Center
Short Name:
J/ApJ/863/79
Date:
21 Oct 2021
Publisher:
CDS
Description:
Deep near-IR images from the VISTA Variables in the Via Lactea (VVV) Survey were used to search for RR Lyrae stars within 100 arcmin from the Galactic Center. A large sample of 960 RR Lyrae of type ab (RRab) stars were discovered. A catalog is presented featuring the positions, magnitudes, colors, periods, and amplitudes for the sample, in addition to estimated reddenings, distances, and metallicities, and measured individual relative proper motions. We use the reddening-corrected Wesenheit magnitudes, defined as W_Ks_=Ks-0.428x(J-Ks), in order to isolate bona fide RRL belonging to the Galaxy Center, finding that 30 RRab are foreground/background objects. We measure a range of extinctions from A_Ks_=0.19 to 1.75mag for the RRab in this region, finding that large extinction is the main cause of the sample incompleteness. The mean period is P=0.5446+/-0.0025d, yielding a mean metallicity of [Fe/H]=-1.30+/-0.01 ({sigma}=0.33)dex for the RRab sample in the Galactic Center region. The median distance for the sample is D=8.05+/-0.02kpc. We measure the RRab surface density using the less reddened region sampled here, finding a density of 1000 RRab/sq deg at a projected Galactocentric distance R_G_=1.6deg. Under simple assumptions, this implies a large total mass (M>10^9^M_{sun}_) for the old and metal-poor population contained inside RG. We also measure accurate relative proper motions, from which we derive tangential velocity dispersions of {sigma}V_l_=125.0 and {sigma}V_b_=124.1km/s along the Galactic longitude and latitude coordinates, respectively. The fact that these quantities are similar indicate that the bulk rotation of the RRab population is negligible, and implies that this population is supported by velocity dispersion. In summary, there are two main conclusions of this study. First, the population as a whole is no different from the outer bulge RRab, predominantly a metal-poor component that is shifted with respect to the Oosterhoff type I population defined by the globular clusters in the halo. Second, the RRab sample, as representative of the old and metal-poor stellar population in the region, has high velocity dispersions and zero rotation, suggesting a formation via dissipational collapse.
803. RR Lyrae GCVS and TYC2 identifiers
ID:
ivo://CDS.VizieR/J/A+A/390/173
Title:
RR Lyrae GCVS and TYC2 identifiers
Short Name:
J/A+A/390/173
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Tycho-2 catalogue (<I/259>) provides astrometric and photometric data for the 2.5 million brightest stars in the sky. Therefore it can provide much larger samples than the Hipparcos samples used to date in statistical studies. The object of this paper is the cross-identification of Tycho-2 sources and known variable stars of RR Lyrae type. The Tycho-2 data of cross-identified sources are added into the ASTRID specialized database. The present selection almost doubles the size of the sample of RR Lyrae stars with available proper motions.
804. RR Lyrae in Draco dSph
ID:
ivo://CDS.VizieR/J/AJ/127/861
Title:
RR Lyrae in Draco dSph
Short Name:
J/AJ/127/861
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the first CCD variability study of the Draco dwarf spheroidal galaxy. The data were obtained with the Fred Lawrence Whipple Observatory 1.2m telescope on Mount Hopkins, Arizona, between 1998 August 19 and 1999 June 20, over 22 nights, over a period of 10 months, covering a 22'x22' field centered at {alpha}=17h19m57.5s, {delta}=57{deg}50'05" (J2000.0). The analysis of the BVI images produced 163 variable stars, 146 of which were RR Lyrae: 123 RRab, 16 RRc, 6 RRd, and one RR12. The other variables include a SX Phe star, four anomalous Cepheids, and a field eclipsing binary. Using the short distance scale statistical parallax calibration of Gould & Popowski (1998ApJ...508..844G) and 94 RRab stars from our field, we obtain a distance modulus of (m-M)_0_=19.40+/-0.02(stat)+/-0.15(syst)mag for Draco, corresponding to a distance of 75.8+/-0.7(stat)+/-5.4(syst)kpc. By comparing the spread in magnitudes of RRab stars in B, V, and I, we find no evidence for internal dust in the Draco dwarf spheroidal galaxy. The catalog of all variables, as well as their photometry and finding charts, is available electronically via anonymous ftp and the World Wide Web. The complete set of the CCD frames is available upon request.
805. RR Lyrae in 15 Galactic globular clusters
ID:
ivo://CDS.VizieR/J/MNRAS/439/3765
Title:
RR Lyrae in 15 Galactic globular clusters
Short Name:
J/MNRAS/439/3765
Date:
21 Oct 2021
Publisher:
CDS
Description:
The period-metallicity-WISE W1- and W2-band luminosity relations are derived for RR Lyrae stars based on WISE epoch photometry for 360 and 275 stars in 15 and 9 Galactic globular clusters, respectively. Our final relations have the form <M_W1_>={gamma}_W1-(2.381+/-0.097)logP_F_+(0.096+/-0.021)[Fe/H] and <M_W2_>={gamma}_W2_-(2.269+/-0.127)logP_F_+(0.108+/-0.021)[Fe/H], where [Fe/H] values are on the scale of Carretta et al. (2009A&A...508..695C). We obtained two appreciably discrepant estimates for the zero-points {gamma}_W1_ and {gamma}_W2_ of both relations: one based on a statistical-parallax analysis - {gamma}_W1_=-0.829+/-0.093 and {gamma}_W2_=-0.776+/-0.093 and another, significantly brighter one, based on Hubble Space Telescope (HST) Fine Guidance Sensor (FGS) trigonometric parallaxes - {gamma}_W1,HST_=-1.150+/-0.077 and {gamma}_W2,HST_=-1.105+/-0.077. The period-metallicity-luminosity relations in the two bands yield highly consistent distance moduli for the calibrator clusters and the distance moduli computed using the W1- and W2-band relations with the HST zero-points agree well with those computed by Sollima, Cacciari & Valenti based on their derived period-metallicity-K-band luminosity relation whose zero-point is tied to the HST trigonometric parallax of RR Lyrae itself ({Delta}DM0 =0.04 and 0.06, respectively, with a scatter of only 0.06).
806. RR Lyrae in M32
ID:
ivo://CDS.VizieR/J/MNRAS/425/1459
Title:
RR Lyrae in M32
Short Name:
J/MNRAS/425/1459
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present time series photometry of two fields near M32 using archival observations from the Advanced Camera for Surveys Wide Field Channel on-board the Hubble Space Telescope. One field is centred about 2arcmin from M32, while the other is located 15arcmin to the south-east of M31. The imaging covers a time baseline sufficient for the identification and characterization of a total number of 1139 RR Lyrae variables of which 821 are ab-type and 318 are c-type.
807. RR Lyrae in M62 (NGC6266)
ID:
ivo://CDS.VizieR/J/AJ/140/1766
Title:
RR Lyrae in M62 (NGC6266)
Short Name:
J/AJ/140/1766
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new time-series CCD photometry, in the B and V bands, for the moderately metal-rich ([Fe/H]=~-1.3) Galactic globular cluster M62 (NGC 6266). The present data set is the largest obtained so far for this cluster and consists of 168 images per filter, obtained with the Warsaw 1.3m telescope at the Las Campanas Observatory and the 1.3m telescope of the Cerro Tololo Inter-American Observatory, in two separate runs over the time span of 3 months.
808. RR Lyrae in new galactic bulge window
ID:
ivo://CDS.VizieR/J/AJ/114/2596
Title:
RR Lyrae in new galactic bulge window
Short Name:
J/AJ/114/2596
Date:
21 Oct 2021
Publisher:
CDS
Description:
Identifications, light curves, periods, and other pertinent data are presented for RR Lyrae variables found in a galactic bulge region not previously surveyed for these stars. The region (centered at l=0.2, b=-5.8) includes the globular cluster NGC 6558 where probable RR Lyrae members are discussed.
809. RR Lyrae in NGC 6101
ID:
ivo://CDS.VizieR/J/other/PASA/29.72
Title:
RR Lyrae in NGC 6101
Short Name:
J/other/PASA/29.
Date:
21 Oct 2021
Publisher:
CDS
Description:
V- and I-band observations were taken over 9 months to study the RR Lyrae population in the metal-poor diffuse globular cluster NGC 6101. We identify one new variable, which is either a potential long-period red giant variable or eclipsing binary, and recover all previously identified RR Lyraes. One previously studied RR Lyrae is reclassified as an RRc type, while two period estimations have been significantly refined. We confirm that NGC 6101 is Oosterhoff type II with a high ratio of n(c)/n(ab+c)=0.833 with a very long mean RRab period of 0.86d. By using theoretical RR Lyrae period-luminosity-metallicity relations, we use our V- and I-band RR Lyrae data to gain an independent estimate of the reddening towards this cluster of E(B-V)=0.15+/-.04 and derive a distance of 12.8+/-0.8kpc. The majority of the work in this study was undertaken by upper secondary school students involved in the Space to Grow astronomy education project in Australia.
810. RR Lyrae in Northern Sky Variability Survey
ID:
ivo://CDS.VizieR/J/AJ/132/1202
Title:
RR Lyrae in Northern Sky Variability Survey
Short Name:
J/AJ/132/1202
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use data from the Northern Sky Variability Survey (NSVS), obtained from the first-generation Robotic Optical Transient Search Experiment (ROTSE-I), to identify and study RR Lyrae variable stars in the solar neighborhood. We initially identified 1197 RRab (RR0) candidate stars brighter than the ROTSE median magnitude V=14. Periods, amplitudes, and mean V magnitudes are determined for a subset of 1188 RRab stars with well-defined light curves. Metallicities are determined for 589 stars by the Fourier parameter method and by the relationship between period, amplitude, and [Fe/H]. We comment on the difficulties of clearly classifying RRc (RR1) variables in the NSVS data set. Distances to the RRab stars are calculated using an adopted luminosity-metallicity relation with corrections for interstellar extinction. The 589 RRab stars in our final sample are used to study the properties of the RRab population within 5kpc of the Sun. The Bailey diagram of period versus amplitude shows that the largest component of this sample belongs to Oosterhoff type I. Metal-rich ([Fe/H]>-1) RRab stars appear to be associated with the Galactic disk. Our metal-rich RRab sample may include a thin-disk, as well as a thick-disk population, although the uncertainties are too large to establish this. There is some evidence among the metal-rich RRab stars for a decline in scale height with increasing [Fe/H], as was found by Layden. The distribution of RRab stars with -1<[Fe/H]<-1.25 indicates that within this metallicity range the RRab stars are a mixture of stars belonging to halo and disk populations.