- ID:
- ivo://CDS.VizieR/J/A+A/442/381
- Title:
- Precise positions of RR Lyrae Stars with Vmax>12.5
- Short Name:
- J/A+A/442/381
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- RR Lyrae stars are of great importance for investigations of Galactic structure. However, a complete compendium of all RR-Lyraes in the solar neighbourhood with accurate classifications and coordinates does not exist to this day. Here we present a catalogue of 561 local RR-Lyrae stars (V_max_>=12.5mag) according to the magnitudes given in the Combined General Catalogue of Variable Stars (GCVS) and 16 fainter ones. The Tycho2 catalogue contains ~100 RR Lyr stars. However, many objects have inaccurate coordinates in the GCVS, the primary source of variable star information, so that a reliable cross-identification is difficult. We identified RR Lyrae from both catalogues based on an intensive literature search. In dubious cases we carried out photometry of fields to identify the variable. Mennessier & Colome (2002, Cat. <J/A+A/390/173>) have published a paper with Tyc2-GCVS identifications, but we found that many of their identifications are wrong.
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- ID:
- ivo://CDS.VizieR/J/A+A/605/A86
- Title:
- Pre-main sequence stars VLT/X-Shooter spectra
- Short Name:
- J/A+A/605/A86
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Studies of the formation and evolution of young stars and their disks rely on knowledge of the stellar parameters of the young stars. The derivation of these parameters is commonly based on comparison with photospheric template spectra. Furthermore, chromospheric emission in young active stars impacts the measurement of mass accretion rates, a key quantity for studying disk evolution. Here we derive stellar properties of low-mass (M*~<2M_{sun}_) pre-main sequence stars without disks, which represent ideal photospheric templates for studies of young stars. We also use these spectra to constrain the impact of chromospheric emission on the measurements of mass accretion rates. The spectra are reduced, flux-calibrated, and corrected for telluric absorption, and are made available to the community. We derive the spectral type for our targets by analyzing the photospheric molecular features present in their VLT/X-Shooter spectra by means of spectral indices and comparison of the relative strength of photospheric absorption features. We also measure effective temperature, gravity, projected rotational velocity, and radial velocity from our spectra by fitting them with synthetic spectra with the ROTFIT tool.The targets have negligible extinction (AV<0.5mag) and spectral type from G5 to K6, and from M6.5 to M8. They thus complement the library of photospheric templates presented in our previous paper. We perform synthetic photometry on the spectra to derive the typical colors of young stars in different filters. We measure the luminosity of the emission lines present in the spectra and estimate the noise due to chromospheric emission in the measurements of accretion luminosity in accreting stars. Results. We provide a calibration of the photospheric colors of young pre-main sequence stars as a function of their spectral type in a set of standard broad-band optical and near-infrared filters. The logarithm of the noise on the accretion luminosity normalized to the stellar luminosity is roughly constant and equal to -2.3 for targets with masses larger than 1 solar mass, and decreases with decreasing temperatures for lower-mass stars. For stars with masses of 1.5Msun and ages of 1-5Myr, the chromospheric noise converts to a limit of measurable mass accretion rates of 3x10^-10^M_{sun}_/yr. The limit on the mass accretion rate set by the chromospheric noise is of the order of the lowest measured values of mass accretion rates in Class II objects.
- ID:
- ivo://CDS.VizieR/J/A+A/360/472
- Title:
- Proper motions in omega Centauri
- Short Name:
- J/A+A/360/472
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The tables present the photometric and astrometric results of an extensive proper motion study of the globular cluster omega Centauri: information on the photographic plates used, variability analysis, astrometric data for 9847 stars, membership determination and surface density profile, cluster proper motion dispersions and systematics and cross-references with star-numbers used by Norris et al. (1997ApJ...487L.187N) and Lynga (1996A&AS..115..297L).
- ID:
- ivo://CDS.VizieR/J/MNRAS/435/3206
- Title:
- Properties of field RR Lyrae variables
- Short Name:
- J/MNRAS/435/3206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use accurate absolute UCAC4 proper motions, V-band photoelectric and CCD photometry including our own and compiled data, WISE W1-band mid-IR photometry, as well as extensive compiled radial-velocity and [Fe/H] data for 403 Galactic field RR Lyrae type variables to determine the kinematical parameters of the Galactic RR Lyrae population and constrain the zero-points of the V-, W1-, and Ks-band period-metallicity-luminosity relations for RR Lyraes via statistical parallax.
- ID:
- ivo://CDS.VizieR/J/AJ/144/129
- Title:
- Properties of 83 known stellar SiO maser sources
- Short Name:
- J/AJ/144/129
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out simultaneous observations of four maser lines, SiO v=1,2, ^29^SiO v=0,J=1-0, and H_2_O 6_16_-5_23_, toward 83 known SiO maser sources without H_2_O maser detections using the Korean VLBI Network single dish telescopes. Both SiO and H_2_O masers were detected from 14 sources, resulting in a detection rate of 16.9%. H_2_O maser emission without SiO maser emission was detected from one source. Therefore, H_2_O maser emission was newly detected from 15 sources. SiO maser emission without H_2_O detection was detected from 55 sources, which gives a total SiO maser detection rate of 83.1% when including sources that have both SiO and H_2_O maser emission detected. SiO v=2 maser emission was detected from nine sources without v=1 maser detection. The SiO v=2 maser sources without the v=1 maser detections need to be investigated, with a large number of v=2 only maser sources related to the development of dust shells and their evolutionary sequence from asymptotic giant branch (AGB) to post-AGB stars. The average values of the peak and integrated antenna temperature ratios of H_2_O to SiO masers are 0.44 and 0.28 in the 14 sources that have both SiO and H_2_O detections. Observational characteristics of several individual sources are noted and the dependence of the different maser intensity ratios on the stellar phase is discussed. In addition, the observational results of SiO and H_2_O masers are discussed in IRAS two-color diagrams.
- ID:
- ivo://CDS.VizieR/J/ApJ/807/127
- Title:
- Properties of 70 RR Lyrae stars in the LMC bar
- Short Name:
- J/ApJ/807/127
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of the analysis of 70 RR Lyrae stars located in the bar of the Large Magellanic Cloud (LMC). Combining the spectroscopically determined metallicity of these stars from the literature with precise periods from the OGLE III catalog (Soszynski et al. 2009, J/AcA/59/1) and multi-epoch K_s_ photometry from the VISTA survey of the Magellanic Clouds system, we derive a new near-infrared period-luminosity-metallicity (PL_Ks_Z) relation for RR Lyrae variables. In order to fit the relation we use a fitting method developed specifically for this study. The zero-point of the relation is estimated two different ways: by assuming the value of the distance to the LMC and by using Hubble Space Telescope parallaxes of five RR Lyrae stars in the Milky Way (MW). The difference in distance moduli derived by applying these two approaches is ~0.2 mag. To investigate this point further we derive the PL_Ks_Z relation based on 23 MW RR Lyrae stars that had been analyzed in Baade-Wesselink studies. We compared the derived PL_Ks_Z relations for RR Lyrae stars in the MW and LMC. Slopes and zero-points are different, but still consistent within the errors. The shallow slope of the metallicity term is confirmed by both LMC and MW variables. The astrometric space mission Gaia is expected to provide a huge contribution to the determination of the RR Lyrae PL_Ks_Z relation; however, calculating an absolute magnitude from the trigonometric parallax of each star and fitting a PL_Ks_Z relation directly to period and absolute magnitude leads to biased results. We present a tool to achieve an unbiased solution by modeling the data and inferring the slope and zero-point of the relation via statistical methods.
- ID:
- ivo://CDS.VizieR/J/AJ/155/183
- Title:
- Properties of variables in the NGC 1846 field
- Short Name:
- J/AJ/155/183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Intermediate-age (IA) star clusters in the Large Magellanic Cloud (LMC) present extended main-sequence turn-offs (MSTO) that have been attributed to either multiple stellar populations or an effect of stellar rotation. Recently it has been proposed that these extended main sequences can also be produced by ill-characterized stellar variability. Here we present Gemini-S/Gemini Multi-Object Spectrometer (GMOS) time series observations of the IA cluster NGC 1846. Using differential image analysis, we identified 73 new variable stars, with 55 of those being of the Delta Scuti type, that is, pulsating variables close the MSTO for the cluster age. Considering completeness and background contamination effects, we estimate the number of {delta} Sct belonging to the cluster between 40 and 60 members, although this number is based on the detection of a single {delta} Sct within the cluster half-light radius. This amount of variable stars at the MSTO level will not produce significant broadening of the MSTO, albeit higher-resolution imaging will be needed to rule out variable stars as a major contributor to the extended MSTO phenomenon. Though modest, this amount of {delta} Sct makes NGC 1846 the star cluster with the highest number of these variables ever discovered. Lastly, our results present a cautionary tale about the adequacy of shallow variability surveys in the LMC (like OGLE) to derive properties of its {delta} Sct population.
- ID:
- ivo://CDS.VizieR/J/ApJ/850/96
- Title:
- PS1 3{pi} RRab stars within the Sgr stream
- Short Name:
- J/ApJ/850/96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive and precise description of the Sagittarius (Sgr) stellar stream's 3D geometry as traced by its old stellar population. This analysis draws on the sample of ~44000 RR Lyrae (RRab) stars from the Pan-STARRS1 (PS1) 3{pi} survey, which is ~80% complete and ~90% pure within 80 kpc, and extends to >~120kpc with a distance precision of ~3% . A projection of RR Lyrae stars within |^~^B|_{sun}_<9{deg} of the Sgr stream's orbital plane reveals the morphology of both the leading and the trailing arms at very high contrast across much of the sky. In particular, the map traces the stream near- contiguously through the distant apocenters. We fit a simple model for the mean distance and line-of-sight depth of the Sgr stream as a function of the orbital plane angle ^~^{Lambda}_{sun}_, along with a power-law background model for the field stars. This modeling results in estimates of the mean stream distance precise to ~1% and it resolves the stream's line-of-sight depth. These improved geometric constraints can serve as new constraints for dynamical stream models.
- ID:
- ivo://CDS.VizieR/J/ApJ/844/L4
- Title:
- PS1 RRab stars for tracing outer Virgo overdensity
- Short Name:
- J/ApJ/844/L4
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of spatially distinct stellar density features near the apocenters of the Sagittarius (Sgr) stream's main leading and trailing arm. These features are clearly visible in a high-fidelity stellar halo map that is based on RR Lyrae from Pan-STARRS1: there is a plume of stars 10kpc beyond the apocenter of the leading arm, and there is a "spur" extending to 130kpc, almost 30kpc beyond the previously detected apocenter of the trailing arm. Such an apocenter substructure is qualitatively expected in any Sgr stream model, as stars stripped from the progenitor at different pericenter passages become spatially separated there. The morphology of these new Sgr stream substructures could provide much-needed new clues and constraints for modeling the Sgr system, including the level of dynamical friction that Sgr has experienced. We also report the discovery of a new, presumably unrelated halo substructure at 80kpc from the Sun and 10{deg} from the Sgr orbital plane, which we dub the outer Virgo overdensity.
- ID:
- ivo://CDS.VizieR/J/A+A/572/A34
- Title:
- Pulsating solar-like stars in Kepler
- Short Name:
- J/A+A/572/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Kepler ultra-high precision photometry of long and continuous observations provides a unique dataset in which surface rotation and variability can be studied for thousands of stars. Because many of these old field stars also have independently measured asteroseismic ages, measurements of rotation and activity are particularly interesting in the context of age-rotation-activity relations. In particular, age-rotation relations generally lack good calibrators at old ages, a problem that this Kepler sample of old-field stars is uniquely suited to address. We study the surface rotation and photometric magnetic activity of a subset of 540 solar-like stars on the main-sequence and the subgiant branch for which stellar pulsations have been measured.
