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1151. RRLs in globulars. IV. UBVRI photometry in Omega Cen
ID:
ivo://CDS.VizieR/J/AJ/152/170
Title:
RRLs in globulars. IV. UBVRI photometry in Omega Cen
Short Name:
J/AJ/152/170
Date:
21 Oct 2021
Publisher:
CDS
Description:
New accurate and homogeneous optical UBVRI photometry has been obtained for variable stars in the Galactic globular cluster {omega} Cen (NGC 5139). We secured 8202 CCD images covering a time interval of 24 years and a sky area of 84x48arcmin. The current data were complemented with data available in the literature and provided new, homogeneous pulsation parameters (mean magnitudes, luminosity amplitudes, periods) for 187 candidate {omega} Cen RR Lyrae (RRLs). Among them we have 101 RRc (first overtone) and 85 RRab (fundamental) variables, and a single candidate RRd (double-mode) variable. Candidate Blazhko RRLs show periods and colors that are intermediate between the RRc and RRab variables, suggesting that they are transitional objects. A comparison of the period distribution and the Bailey diagram indicates that RRLs in {omega} Cen show a long-period tail not present in typical Oosterhoff II (OoII) globulars. The RRLs in dwarf spheroidals and in ultra-faint dwarfs have properties between Oosterhoff intermediate and OoII clusters. Metallicity plays a key role in shaping the above evidence. These findings do not support the hypothesis that {omega} Cen is the core remnant of a spoiled dwarf galaxy. Using optical period-Wesenheit relations that are reddening-free and minimally dependent on metallicity we find a mean distance to {omega} Cen of 13.71+/-0.08+/-0.01mag (semi-empirical and theoretical calibrations). Finally, we invert the I-band period-luminosity-metallicity relation to estimate individual RRLs' metal abundances. The metallicity distribution agrees quite well with spectroscopic and photometric metallicity estimates available in the literature.
1152. RRLs in globulars. V.{omega} Centauri NIR photometry
ID:
ivo://CDS.VizieR/J/AJ/155/137
Title:
RRLs in globulars. V.{omega} Centauri NIR photometry
Short Name:
J/AJ/155/137
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a new complete near-infrared (NIR, JHK_s_) census of RR Lyrae stars (RRLs) in the globular {omega} Cen (NGC 5139). We collected 15472 JHK_s_ images with 4-8 m class telescopes over 15 years (2000-2015) covering a sky area around the cluster center of 60x34 arcmin^2^. These images provided calibrated photometry for 182 out of the 198 cluster RRL candidates with 10 to 60 measurements per band. We also provide new homogeneous estimates of the photometric amplitude for 180 (J), 176 (H) and 174 (K_s_) RRLs. These data were supplemented with single-epoch JK_s_ magnitudes from VHS (Mcmahon et al. 2013Msngr.154...35M) and with single-epoch H magnitudes from 2MASS (Cat. VII/233). Using proprietary optical and NIR data together with new optical light curves (ASAS-SN) we also updated pulsation periods for 59 candidate RRLs. As a whole, we provide JHK_s_ magnitudes for 90 RRab (fundamentals), 103 RRc (first overtones) and one RRd (mixed-mode pulsator). We found that NIR/optical photometric amplitude ratios increase when moving from first overtone to fundamental and to long-period (P>0.7 days) fundamental RRLs. Using predicted period-luminosity-metallicity relations, we derive a true distance modulus of 13.674+/-0.008+/-0.038 mag (statistical error and standard deviation of the median) based on spectroscopic iron abundances, and of 13.698+/-0.004+/-0.048 mag based on photometric iron abundances. We also found evidence of possible systematics at the 5%-10% level in the zero-point of the period-luminosity relations based on the five calibrating RRLs whose parallaxes had been determined with the HST.
1153. RR Lyrae AllWise photometry
ID:
ivo://CDS.VizieR/J/MNRAS/440/L96
Title:
RR Lyrae AllWise photometry
Short Name:
J/MNRAS/440/L96
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use photometry from the recent AllWISE Data Release of the Wide-field Infrared Survey Explorer (WISE) of 129 calibration stars, combined with prior distances obtained from the established M_V_-[Fe/H] relation and Hubble Space Telescope trigonometric parallax, to derive mid-infrared period-luminosity relations for RR Lyrae pulsating variable stars. We derive relations in the W1, W2 and W3 wavebands (3.4, 4.6 and 12um, respectively), and for each of the two main RR Lyrae sub-types (RRab and RRc). We report an error on the period-luminosity relation slope for RRab stars of 0.2. We also fit posterior distances for the calibration catalogue and find a median fractional distance error of 0.8 per cent.
1154. RR Lyrae as tracers in the Virgo overdensity region
ID:
ivo://CDS.VizieR/J/ApJ/831/165
Title:
RR Lyrae as tracers in the Virgo overdensity region
Short Name:
J/ApJ/831/165
Date:
21 Oct 2021
Publisher:
CDS
Description:
We use a combination of spatial distribution and radial velocity to search for halo substructures in a sample of 412 RR Lyrae stars (RRLSs) that covers a region of ~525 square degrees of the Virgo overdensity (VOD) and spans distances from the Sun from 4 to 75kpc. With a friends-of-friends algorithm we identified six high-significance groups of RRLSs in phase space, which we associate mainly with the VOD and with the Sagittarius stream. Four other groups were also flagged as less significant overdensities. Three high-significance and three lower-significance groups have distances between ~10 and 20kpc, which places them in the distance range attributed by others to the VOD. The largest of these is the Virgo stellar stream at 19kpc, which has 18 RRLSs, a factor of two increase over the number known previously. While these VOD groups are distinct according to our selection criteria, their overlap in position and distance and, in a few cases, similarity in radial velocity are suggestive that they may not all stem from separate accretion events. Even so, the VOD appears to be caused by more than one overdensity. The Sagittarius (Sgr) stream is a very obvious feature in the background of the VOD at a mean distance of 44kpc. Two additional high-significance groups were detected at distances >40kpc. Their radial velocities and locations differ from the expected path of the Sgr debris in this part of the sky, and they are likely to be remnants of other accretion events.
1155. RR Lyrae candidates in Aqr halo stream
ID:
ivo://CDS.VizieR/J/other/NewA/27.1
Title:
RR Lyrae candidates in Aqr halo stream
Short Name:
J/other/NewA/27.
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Aquarius stream has been recently discovered in the course of the RAVE Survey. It is a chemically coherent structure, originating from the tidal disruption of a 12Gyr, [Fe/H]=-1.0 globular cluster. We have surveyed a ~284deg^2^ area of the sky containing the 15 known members of the Aquarius stream looking for RR Lyr variables. RR Lyr variables are primary distance indicators and discovering some of them firmly associated with the Aquarius stream would provide a 3D representation of its Galactic orbit and would probe the spatial structure of the Galactic gravitational potential. During September and October 2012, we have obtained on-purpose, epoch photometry in the Landolt BV and Sloan gri bands with the APASS South telescopes located at Cerro Tololo. Our data are uniformly complete to V=15.2mag over the whole surveyed area, the faintest recorded stars reaching V=18mag. We have found 71 RR Lyr variables, and a firm pulsation period was derived for 53 of them. Our census of RR Lyr variables is complete to a distance of 8kpc from the Sun. For all objects we provide distances and light- and color-curves, mean values and amplitudes in all five BVgri passbands, finding charts and accurate local photometric sequences. About half of the RR Lyr variables we have discovered were previously known, but we provide the first multi-band photometric data. They were in fact mostly discovered as by-products of white-light patrol searches for optical counterparts to gamma-ray bursters or potentially hazardous asteroids.
1156. RR Lyrae candidates in the MW outer halo
ID:
ivo://CDS.VizieR/J/ApJ/849/150
Title:
RR Lyrae candidates in the MW outer halo
Short Name:
J/ApJ/849/150
Date:
21 Oct 2021
Publisher:
CDS
Description:
RR Lyrae stars are ideal massless tracers that can be used to study the total mass and dark matter content of the outer halo of the Milky Way (MW). This is because they are easy to find in the light-curve databases of large stellar surveys and their distances can be determined with only knowledge of the light curve. We present here a sample of 112 RR Lyr stars beyond 50kpc in the outer halo of the MW, excluding the Sgr streams, for which we have obtained moderate-resolution spectra with Deimos on the Keck II Telescope. Four of these have distances exceeding 100kpc. These were selected from a much larger set of 447 candidate RR Lyr stars that were data-mined using machine-learning techniques applied to the light curves of variable stars in the Palomar Transient Facility database. The observed radial velocities taken at the phase of the variable corresponding to the time of observation were converted to systemic radial velocities in the Galactic standard of rest. From our sample of 112 RR Lyr stars we determine the radial velocity dispersion in the outer halo of the MW to be ~90km/s at 50kpc, falling to about 65km/s near 100 kpc once a small number of major outliers are removed. With reasonable estimates of the completeness of our sample of 447 candidates and assuming a spherical halo, we find that the stellar density in the outer halo declines as r^-4^.
1157. 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.
1158. 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.
1159. 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.
1160. 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.