- ID:
- ivo://CDS.VizieR/J/A+A/631/A37
- Title:
- Classical Cepheids consistent radial velocities
- Short Name:
- J/A+A/631/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate radial velocities (vrad) of Cepheids are mandatory within the context of Cepheid distance measurements using the Baade-Wesselink technique. The most common vrad derivation method consists in cross-correlating the observed stellar spectra with a binary template and measuring a velocity on the resulting mean profile. Nevertheless, for Cepheids and other pulsating stars, the spectral lines selected within the template as well as the way of fitting the cross-correlation function (CCF) have a direct and significant impact on the measured vrad. Our first aim is to detail the steps to compute consistent CCFs and vrad of Cepheids. Next, this study aims at characterising the impact of Cepheid spectral properties and vrad computation methods on the resulting line profiles and vrad time series. We collected more than 3900 high-resolution spectra from seven different spectrographs of 64 Classical Milky Way (MW) Cepheids. These spectra were normalised and standardised using a single custom-made process on pre-defined wavelength ranges.We built six tailored correlation templates selecting unblended spectral lines of different depths based on a synthetic Cepheid spectrum, on three different wavelength ranges from 3900 to 8000{AA}. Each observed spectrum was cross-correlated with these templates to build the corresponding CCFs, adopted as the proxy for the spectrum mean line profile. We derived a set of line profile observables as well as three different vrad measurements from each CCF and two custom proxies for the CCF quality and amount of signal. This study presents a large catalogue of consistent Cepheid CCFs and vrad time series. It confirms that each step of the process has a significant impact on the deduced vrad: the wavelength, the template line depth and width, and the vrad computation method. The way towards more robust Cepheid vrad time series seems to go through steps that minimise the asymmetry of the line profile and its impact on the vrad. Centroid or first-moment vrad, that exhibit slightly smaller amplitudes but significantly smaller scatter than Gaussian or biGaussian vrad, should therefore be favoured. Stronger or deeper spectral lines also tend to be less asymmetric and lead to more robust vrad than weaker lines.
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- ID:
- ivo://CDS.VizieR/J/ApJ/832/176
- Title:
- Classical Cepheids in MCs. I. LMC disk
- Short Name:
- J/ApJ/832/176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed investigation of the Large Magellanic Cloud (LMC) disk using classical Cepheids. Our analysis is based on optical (I, V; OGLE-IV), near-infrared (NIR: J, H, K_S_) and mid-infrared (MIR: w1; WISE) mean magnitudes. By adopting new templates to estimate the NIR mean magnitudes from single-epoch measurements, we build the currently most accurate, largest, and homogeneous multi-band data set of LMC Cepheids. We determine Cepheid individual distances using optical and NIR Period-Wesenheit relations (PWRs), to measure the geometry of the LMC disk and its viewing angles. Cepheid distances based on optical PWRs are precise at 3%, but accurate to 7%, while the ones based on NIR PWRs are more accurate (to 3%), but less precise (2%-15%), given the higher photometric error on the observed magnitudes. We found an inclination of i=25.05+/-0.02(stat.)+/-0.55(syst.){deg}, and a position angle of the lines of nodes P.A.=150.76+/-0.02(stat.)+/-0.07(syst.){deg}. These values agree well with estimates based either on young (Red Supergiants) or on intermediate-age (Asymptotic Giant Branch, Red Clump) stellar tracers, but they significantly differ from evaluations based on old (RR Lyrae) stellar tracers. This indicates that young/intermediate and old stellar populations have different spatial distributions. Finally, by using the reddening-law fitting approach, we provide a reddening map of the LMC disk, which is 10 times more accurate and 2 times larger than similar maps in the literature. We also found an LMC true distance modulus of {mu}_0,LMC_=18.48+/-0.10(stat. and syst.)mag, in excellent agreement with the currently most accurate measurement.
- ID:
- ivo://CDS.VizieR/J/A+A/453/535
- Title:
- Classification of bright mid-IR sources
- Short Name:
- J/A+A/453/535
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Context: The stellar populations in the central region of the Galaxy are poorly known because of the high visual extinction and very great source density in this direction. Aims: To use recent infrared surveys for studying the dusty stellar objects in this region. Methods: We analyse the content of a ~20x20arcmin^2 field centred at (l,b)=(-0.27,-0.06) observed at 7 and 15 microns as part of the ISOGAL survey. These ISO observations are more than an order of magnitude better in sensitivity and spatial resolution than the IRAS observations. The sources are cross-associated with other catalogues to identify various types of objects. We then derive criteria to distinguish young objects from post-main sequence stars. Results: We find that a sample of about 50 young stellar objects and ultra-compact HII regions emerges, out of a population of evolved AGB stars. We demonstrate that the sources colours and spatial extents, as they appear in the ISOGAL catalogue, possibly complemented with MSX photometry at 21 microns, can be used to determine whether the ISOGAL sources brighter than 300mJy at 15 microns (or [15]<4.5mag) are young objects or late-type evolved stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/2917
- Title:
- Classification of Hipparcos variables
- Short Name:
- J/MNRAS/427/2917
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hipparcos catalogue (ESA 1997, Cat. I/239) and the AAVSO Variable Star Index (Watson et al., 2011, Cat. B/vsx) are employed to complement the training set of periodic variables of Dubath et al. (2011, Cat. J/MNRAS/414/2602) with irregular and non-periodic representatives, leading to 3881 sources in total which described 24 variability types. The attributes employed to characterize light-curve features are selected according to their relevance for classification. Classifier models are produced with random forests and a multi-stage methodology based on Bayesian networks, achieving overall misclassification rates under 12%. Both classifiers are applied to predict variability types for 6051 Hipparcos variables associated with uncertain or missing types in the literature.
- ID:
- ivo://CDS.VizieR/J/other/Obs/131.315
- Title:
- CL Eri, CM Eri, CN Eri BVIc light curves
- Short Name:
- J/other/Obs/131.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A total of total of 1071 B, V, Ic-band CCD frames are taken for three GCVS RR Lyr-type variables (CL Eri, CM Eri, and CN Eri), for which only coordinates were known. Observations were made with the 76-cm telescope of the South African Astronomical Observatory using an SBIG CCD ST-10XME. The inferred periods and light-curves confirm that CL Eri (P=0.644d), which was found to exhibit the Blazhko effect, and CN Eri (P=0.580d) are RR Lyr-type variables. CM Eri is most probably a Population-Il Cepheid with a period of 0.824d.
- ID:
- ivo://CDS.VizieR/J/MNRAS/437/906
- Title:
- Cl* IC 348 H 254 VRI light curves
- Short Name:
- J/MNRAS/437/906
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present new photometric and radial velocity data for the PMS {delta} Sct star H254, member of the young cluster IC 348. Photometric V, R_C_, I_C_ light curves were obtained at the Loiano and Asiago telescopes. The radial velocity data were acquired by means of the SARG@Telescopio Nazionale Galileo spectrograph. High-resolution spectroscopy allowed us to derive precise stellar parameters and the chemical composition of the star, obtaining Teff=6750+/-150K; logg=14.1+/-0.4dex and [Fe/H]=-0.07+/-0.12dex. Photometric and spectroscopic data were used to estimate the total absorption in the V band A_V_=2.06+/-0.05mag, in agreement with previous estimates. We adopted the technique of the difference in phase and amplitude between different photometric bands and radial velocities to verify that H254 is (definitely) pulsating in a radial mode. This occurrence allowed us to apply the CORS realization of the Baade-Wesselink method to obtain a value for the linear radius of H254 equal to 3.3+/-0.7R_{sun}_. This result was used in conjunction with photometry and effective temperature to derive a distance estimate of 273+/-23pc for H254, and, in turn for IC 348, the host cluster. This value is in agreement within the errors with the results derived from several past determinations and the evaluation obtained through the Hipparcos} parallaxes. Finally, we derived the luminosity of H254 and studied its position in the Hertzsprung-Russell diagram. From this analysis it results that this {delta} Scuti occupies a position close to the red edge of the instability strip, pulsates in the fundamental mode, has a mass of about 2.2M_{sun}_ and an age of 5+/-1Myr, older than previous estimates.
- ID:
- ivo://CDS.VizieR/J/other/BASI/40.51
- Title:
- Cl* NGC 2539 CKY V3 and V4 BV light curves
- Short Name:
- J/other/BASI/40.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD photometric observations of the eclipsing contact binaries (EW type) V3 and V4 of the cluster NGC 2539 were made in the B and V bands using the 2m telescope at the IUCAA-Girawali Observatory in India. The light curves have been obtained and using the Wilson-Devinney code, the combined photometric solutions have been presented here. The photometric solutions have revealed that both V3 and V4 are W-type contact binary systems with mass ratios of 0.806 and 1.001 respectively. Revised orbital periods, absolute masses and radii of the components have been obtained.
- ID:
- ivo://CDS.VizieR/J/PAZh/23/458
- Title:
- Close binary system V502 Cyg in Cyg T2
- Short Name:
- J/PAZh/23/458
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photoelectric UBVR observations of the short period close binary system V502 Cyg in the T association Cyg T2 are presented.
- ID:
- ivo://CDS.VizieR/J/A+A/475/559
- Title:
- 12CO(1-0) and 12CO(2-1) maps of EP Aqr
- Short Name:
- J/A+A/475/559
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CO rotational lines are frequently used to trace the outflows from AGB stars. Some profiles are composite, with a narrow component super-imposed on a broader one. These profiles have been interpreted in different ways, calling for episodic mass loss, a bipolar flow, or a circumstellar disk.
- ID:
- ivo://CDS.VizieR/II/250
- Title:
- Combined General Catalogue of Variable Stars
- Short Name:
- II/250
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The GCVS is the only reference source on all known variable stars. This version contains all of the electronically-readable version as distributed by the Sternberg Astronomical Institute and Institute of Astronomy (Russian Acad.Sci.), Moscow. It includes the catalog of variable stars, updated and completed with the Name-Lists of Variables Stars Nos.67-77 (see IBVS No.2681,1985; No.3058,1987; No.3323,1989; No.3530,1990; No.3840,1993; No.4140,1995; No.4471,1997; No.4659, 1999; No.4870, 2000; No.5135, 2001; No.5422, 2003) a catalog of suspected variables, a cross-index of variable star names, a catalog of extragalactic variables, and a catalog of supernovae.
