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821. RR Lyrae star candidates from SDSS-DR15
ID:
ivo://CDS.VizieR/J/ApJS/246/8
Title:
RR Lyrae star candidates from SDSS-DR15
Short Name:
J/ApJS/246/8
Date:
21 Oct 2021
Publisher:
CDS
Description:
With the increase of known RR Lyrae stars, it is reliable to create classifiers of RR Lyrae stars based on their photometric data or combined photometric and spectroscopic data. Nevertheless the total number of known RR Lyrae stars is still too small compared with the large survey databases. So classification of RR Lyrae stars and other sources belongs to imbalanced learning. Based on Sloan Digital Sky Survey (SDSS) photometric and spectroscopic data, we apply cost-sensitive Random Forests fit for imbalanced learning to preselect RR Lyrae star candidates. Only with photometric data, u-g,g-r,r-i,i-z is the best input pattern. While also considering physical parameters (Teff, [Fe/H], log(g)), the optimal input pattern is Teff, [Fe/H], log(g), u-g,g-r,r-i,i-z, at this moment for cost-sensitive Random Forests, the performance metrics of completeness, contamination, and Matthews correlation coefficient are 0.975, 0.019, and 0.975, respectively. It indicates that adding stellar physical parameters is helpful for identifying RR Lyrae stars from other stars. We apply the best classifiers on the SDSS photometric data and combined photometric data with physical parameters to select RR Lyrae star candidates. Finally 11,041 photometric candidates with spectral type A and F are obtained, and then 304 candidates with physical parameters are selected out. Among the 304 candidates, a small part are HB stars, BS stars, RGB stars, and peculiar stars, and the rest are unknown in the Simbad database. These candidates may be used as the input catalog for time-series follow-up observations.
822. RR Lyrae stars BV photometry in UMa I
ID:
ivo://CDS.VizieR/J/ApJ/767/62
Title:
RR Lyrae stars BV photometry in UMa I
Short Name:
J/ApJ/767/62
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have performed the first study of the variable star population of Ursa Major I (UMa I), an ultra-faint dwarf satellite recently discovered around the Milky Way (MW) by the Sloan Digital Sky Survey. Combining time series observations in the B and V bands from four different telescopes, we have identified seven RR Lyrae stars in UMa I, of which five are fundamental-mode (RRab) and two are first-overtone pulsators (RRc). Our V, B-V color-magnitude diagram of UMa I reaches V~23mag (at a signal-to-noise ratio of ~6) and shows features typical of a single old stellar population. The mean pulsation period of the RRab stars <P_ab_>=0.628, {sigma}=0.071 days (or <P_ab_>=0.599, {sigma}=0.032 days, if V4, the longest period and brightest variable, is discarded) and the position on the period-amplitude diagram suggest an Oosterhoff-intermediate classification for the galaxy. The RR Lyrae stars trace the galaxy horizontal branch (HB) at an average apparent magnitude of <V(RR)>=20.43+/-0.02mag (average on six stars and discarding V4), giving in turn a distance modulus for UMa I of (m-M)_0_=19.94+/-0.13mag, distance d=97.3_-5.7_^+6.0^kpc, in the scale where the distance modulus of the Large Magellanic Cloud is 18.5+/-0.1mag. Isodensity contours of UMa I red giants and HB stars (including the RR Lyrae stars identified in this study) show that the galaxy has an S-shaped structure, which is likely caused by the tidal interaction with the MW. Photometric metallicities were derived for six of the UMa I RR Lyrae stars from the parameters of the Fourier decomposition of the V-band light curves, leading to an average metal abundance of [Fe/H]=-2.29dex ({sigma}=0.06dex, average on six stars) on the Carretta et al. (2009, J/A+A/505/117) metallicity scale.
823. RR Lyrae stars from the PS1 3{pi} survey
ID:
ivo://CDS.VizieR/J/AJ/153/204
Title:
RR Lyrae stars from the PS1 3{pi} survey
Short Name:
J/AJ/153/204
Date:
21 Oct 2021
Publisher:
CDS
Description:
RR Lyrae stars may be the best practical tracers of Galactic halo (sub-)structure and kinematics. The PanSTARRS1 (PS1) 3{pi} survey offers multi-band, multi-epoch, precise photometry across much of the sky, but a robust identification of RR Lyrae stars in this data set poses a challenge, given PS1's sparse, asynchronous multi-band light curves (<~12 epochs in each of five bands, taken over a 4.5yr period). We present a novel template fitting technique that uses well-defined and physically motivated multi-band light curves of RR Lyrae stars, and demonstrate that we get accurate period estimates, precise to 2s in >80% of cases. We augment these light-curve fits with other features from photometric time-series and provide them to progressively more detailed machine-learned classification models. From these models, we are able to select the widest (three-fourths of the sky) and deepest (reaching 120kpc) sample of RR Lyrae stars to date. The PS1 sample of ~45000 RRab stars is pure (90%) and complete (80% at 80kpc) at high galactic latitudes. It also provides distances that are precise to 3%, measured with newly derived period-luminosity relations for optical/near-infrared PS1 bands. With the addition of proper motions from Gaia and radial velocity measurements from multi-object spectroscopic surveys, we expect the PS1 sample of RR Lyrae stars to become the premier source for studying the structure, kinematics, and the gravitational potential of the Galactic halo. The techniques presented in this study should translate well to other sparse, multi-band data sets, such as those produced by the Dark Energy Survey and the upcoming Large Synoptic Survey Telescope Galactic plane sub-survey.
824. RR Lyrae stars in and around NGC 6441
ID:
ivo://CDS.VizieR/J/AJ/155/171
Title:
RR Lyrae stars in and around NGC 6441
Short Name:
J/AJ/155/171
Date:
21 Oct 2021
Publisher:
CDS
Description:
Detailed elemental abundance patterns of metal-poor ([Fe/H]~-1 dex) stars in the Galactic bulge indicate that a number of them are consistent with globular cluster (GC) stars and may be former members of dissolved GCs. This would indicate that a few per cent of the Galactic bulge was built up from destruction and/or evaporation of GCs. Here, an attempt is made to identify such presumptive stripped stars originating from the massive, inner Galaxy GC NGC 6441 using its rich RR Lyrae variable star (RRL) population. We present radial velocities of 40 RRLs centered on the GC NGC 6441. All 13 of the RRLs observed within the cluster tidal radius have velocities consistent with cluster membership, with an average radial velocity of 24+/-5 km/s and a star-to-star scatter of 11 km/s. This includes two new RRLs that were previously not associated with the cluster. Eight RRLs with radial velocities consistent with cluster membership but up to three time the distance from the tidal radius are also reported. These potential extra-tidal RRLs also have exceptionally long periods, which is a curious characteristic of the NGC 6441 RRL population that hosts RRLs with periods longer than seen anywhere else in the Milky Way. As expected of stripped cluster stars, most are inline with the cluster's orbit. Therefore, either the tidal radius of NGC 6441 is underestimated and/or we are seeing dissolving cluster stars stemming from NGC 6441 that are building up the old spheroidal bulge.
825. RR Lyrae stars in GCVS observed by the QES
ID:
ivo://CDS.VizieR/J/other/IBVS/6106
Title:
RR Lyrae stars in GCVS observed by the QES
Short Name:
J/other/IBVS/610
Date:
21 Oct 2021
Publisher:
CDS
Description:
We used the light curve archive of the Qatar Exoplanet Survey to investigate the RR Lyrae variable stars listed in the GCVS. Of 588 variables studied, we reclassified 14 as eclipsing binaries, one as an RS CVn type variable, one as an irregular variable, four as classical Cepheids, and one as a type II Cepheid, while also improving their periods. We also report new RR Lyrae sub-type classifications for 65 variables and improve on the GCVS period estimates for 135 RR Lyrae variables. There are seven double-mode RR Lyrae stars in the sample for which we measured their fundamental and first overtone periods. Finally, we detected the Blazhko effect in 38 of the RR Lyrae stars for the first time and we successfully measured the Blazhko period for 26 of them.
826. RR Lyrae stars in M4. II. Spitzer/IRAC phot.
ID:
ivo://CDS.VizieR/J/ApJ/808/11
Title:
RR Lyrae stars in M4. II. Spitzer/IRAC phot.
Short Name:
J/ApJ/808/11
Date:
21 Oct 2021
Publisher:
CDS
Description:
New mid-infrared (MIR) period-luminosity (PL) relations are presented for RR Lyrae variables in the globular cluster M4 (NGC 6121). Accurate photometry was obtained for 37 RR Lyrae variables using observations from the Infrared Array Camera on board the Spitzer Space Telescope. The dispersion of M4's PL relations is 0.056, and the uncertainty in the slope is 0.11mag. Additionally, we established calibrated PL relations at 3.6 and 4.5{mu}m using published Hubble Space Telescope geometric parallaxes of five Galactic RR Lyrae stars. The resulting band-averaged distance modulus for M4 is {mu}=11.399+/-0.007(stat)+/-0.080(syst)+/-0.015(cal)+/-0.020(ext). The systematic uncertainty will be greatly reduced when parallaxes of more stars become available from the GAIA mission. Optical and infrared period-color (PC) relations are also presented, and the lack of an MIR PC relation suggests that RR Lyrae stars are not affected by CO absorption in the 4.5{mu}m band.
827. RR Lyrae stars in six ultra-deep fields of M31
ID:
ivo://CDS.VizieR/J/AJ/141/171
Title:
RR Lyrae stars in six ultra-deep fields of M31
Short Name:
J/AJ/141/171
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present HST/ACS observations of RR Lyrae variable stars in six ultra-deep fields of the Andromeda galaxy (M31), including parts of the halo, disk, and giant stellar stream. Past work on the RR Lyrae stars in M31 has focused on various aspects of the stellar populations that make up the galaxy's halo, including their distances and metallicities. This study builds upon this previous work by increasing the spatial coverage (something that has been lacking in previous studies) and by searching for these variable stars in constituents of the galaxy not yet explored.
828. RR Lyrae stars in the Catalina Sky Survey
ID:
ivo://CDS.VizieR/J/ApJ/765/154
Title:
RR Lyrae stars in the Catalina Sky Survey
Short Name:
J/ApJ/765/154
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the analysis of 1207 RR Lyrae found in photometry taken by the Catalina Survey's Mount Lemmon telescope. By combining accurate distances for these stars with measurements for ~14000 type-ab RR Lyrae from the Catalina Schmidt telescope, we reveal an extended association that reaches Galactocentric distances beyond 100kpc and overlaps the Sagittarius stream system. This result confirms earlier evidence for the existence of an outer halo tidal stream resulting from a disrupted stellar system. By comparing the RR Lyrae source density with that expected based on halo models, we find the detection has ~8{sigma} significance. We investigate the distances, radial velocities, metallicities, and period-amplitude distribution of the RR Lyrae. We find that both radial velocities and distances are inconsistent with current models of the Sagittarius stream. We also find tentative evidence for a division in source metallicities for the most distant sources. Following prior analyses, we compare the locations and distances of the RR Lyrae with photometrically selected candidate horizontal branch stars and find supporting evidence that this structure spans at least 60{deg} of the sky. We investigate the prospects of an association between the stream and the unusual globular cluster NGC 2419.
829. RR Lyrae stars in the Sgr dwarf
ID:
ivo://CDS.VizieR/J/A+A/375/909
Title:
RR Lyrae stars in the Sgr dwarf
Short Name:
J/A+A/375/909
Date:
21 Oct 2021
Publisher:
CDS
Description:
We carried out a period analysis on ~3700 RR Lyrae stars on two Schmidt fields centred on (l, b)=(3.1{deg}, -77.1{deg}) and (6.6{deg}, -10.8{deg}) respectively, covering an area of ~50{deg}^2^. These stars are distributed almost evenly between the Sagittarius dwarf galaxy (Sgr) and the Milky Way. Files in the "lcurves" directory are the light curves of the multi-periodic RR Lyraes discovered towards the Sgr dwarf galaxy. This set includes stars in Sgr and also foreground Galactic RR Lyraes.
830. RR Lyrae stars in the Sgr dwarf galaxy
ID:
ivo://CDS.VizieR/J/A+A/357/871
Title:
RR Lyrae stars in the Sgr dwarf galaxy
Short Name:
J/A+A/357/871
Date:
21 Oct 2021
Publisher:
CDS
Description:
We carried out a search for RR Lyrae stars towards the Sagittarius dwarf galaxy based on two series of photographic Schmidt plates. This search yielded 4013 RR Lyrae stars (3947 mono-periodic, and 66 multi-periodic) spread over ~50 square degrees between Galactic latitudes b=-4{deg} and b=-15{deg}. The analysis of this catalog of RR Lyraes allowed us to map the structure of the Sagittarius dwarf galaxy behind the high density of Galactic foreground stars (this paper, Paper I), and to study the properties of the old stellar population in the Sgr dwarf (Paper II, Cseresnjes, 2001, Cat. <J/A+A/375/909>).