- ID:
- ivo://CDS.VizieR/J/A+A/566/A43
- Title:
- EPOCH Project. EROS-2 LMC periodic variables
- Short Name:
- J/A+A/566/A43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The EPOCH (EROS-2 periodic variable star classification using machine learning) project aims to detect periodic variable stars in the EROS-2 light curve database. In order to classify these variables, we first build a training set by compiling known variables in the Large Magellanic Could area from the OGLE and MACHO surveys. We crossmatch these variables with the EROS-2 sources and extract 22 variability features from 28,392 light curves of the corresponding EROS-2 sources. We then use Random Forests to classify the EROS-2 sources in the training set. We design the model to separate not only Delta Scuti stars, RR Lyraes, Cepheids, eclipsing binaries and long-period variables, the "superclasses", but also their subclasses, such as RRab, RRc, RRd and RRe for RR Lyraes, and similarly for the other variable types. We apply the trained model to the entire EROS-2 LMC database containing about 29 million sources and find 117,234 periodic variable candidates. Out of these 117,234 periodic variables, 55,285 have not been discovered by either OGLE or MACHO variability studies. This set comprises 1906 Delta Scuti stars, 6,607 RR Lyraes, 638 Cepheids, 178 Type II Cepheids, 34,562 eclipsing binaries and 11,394 long-period variables.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/447/2404
- Title:
- Equivalent width of 21 RR Lyrae stars
- Short Name:
- J/MNRAS/447/2404
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have analysed a sample of 18 RR Lyrae stars (17 fundamental-mode - RRab - and one first overtone - RRc) and three Population II Cepheids (two BL Her stars and one W Vir star), for which high-resolution (R>=30000), high signal-to-noise (S/N>=30) spectra were obtained with either SARG at the Telescopio Nazionale Galileo (La Palma, Spain) or UVES at the ESO Very Large Telescope (Paranal, Chile). Archival data were also analyzed for a few stars, sampling >~3 phases for each star. We obtained atmospheric parameters (T_eff_, logg, v_t_, and [M/H]) and abundances of several iron-peak and {alpha}-elements (Fe, Cr, Ni, Mg, Ca, Si, and Ti) for different pulsational phases, obtaining <[{alpha}/Fe]>=+0.31+/-0.19dex over the entire sample covering -2.2<[Fe/H]<-1.1dex. We find that silicon is indeed extremely sensitive to the phase, as reported by previous authors, and cannot be reliably determined. Apart from this, metallicities and abundance ratios are consistently determined, regardless of the phase, within 0.10-0.15 dex, although caution should be used in the range 0<~{phi}<~0.15. Our results agree with literature determinations for both variable and non-variable field stars, obtained with very different methods, including low and high-resolution spectroscopy. W Vir and BL Her stars, at least in the sampled phases, appear indistinguishable from RRab from the spectroscopic analysis point of view. Our large sample, covering all pulsation phases, confirms that chemical abundances can be obtained for RR Lyrae with the classical EW-based technique and static model atmospheres, even rather close to the shock phases.
- ID:
- ivo://CDS.VizieR/J/A+A/412/495
- Title:
- Equivalent widths for 6 RS CVn systems
- Short Name:
- J/A+A/412/495
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photospheric parameters and abundances are presented for a sample of single-lined chromospherically active binaries from a differential LTE analysis of high-resolution spectra. Abundances have been derived for 13 chemical species, including several key elements such as Li, Mg, and Ca.
- ID:
- ivo://CDS.VizieR/J/A+A/495/249
- Title:
- EROS-2 beat Cepheids in Magellanic Clouds
- Short Name:
- J/A+A/495/249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a systematic search of Beat Cepheids (BC) in the Magellanic Clouds from the EROS-2 database. Observations were carried out on the MARLY telescope (ESO La Silla, Chile) between July 1996 and March 2003. A specific pipeline was developed to extract periodic light curves from the photometric data obtained with the PEIDA package (Ansari, 1996VA.....40..519A). Two different populations are identified in each Cloud: the BCs pulsating on the fundamental and first overtone modes (FO/F objects) simultaneously, and those pulsating on the first and second overtones (SO/FO objects). A Fourier analysis was performed on each light curve. We derived lower, higher and mean values of metallicities for the FO/F objects, using linear nonadiabatic convective stellar models.
- ID:
- ivo://CDS.VizieR/J/A+A/389/149
- Title:
- EROS II periodic stars towards Galactic spiral arm
- Short Name:
- J/A+A/389/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a search for variable stars in a photometric survey of a six square degree region along the Galactic plane at (l=305{deg}, b=-0.8{deg}) and (l=330{deg}, b=-2.5{deg}). This survey was performed in the framework of the EROS II (Experience de Recherche d'Objets Sombres) microlensing program. The variable stars were found among 1913576 stars that were monitored between April and June 1998 in two passbands, with an average of 60 measurements. For the periodicity search, a new method is proposed well suited when the photometric data are unevenly distributed in time, as is our case. 1362 objects whose luminosity varies were selected. Among them we identified 9 Cepheids, 19 RR Lyrae, 34 Miras, 176 eclipsing binaries and 266 Semi-Regular stars. Most of them are newly identified objects. The cross-identification with known catalogues has been performed. Our catalogue and light curves are available from our Web site (http://www.lal.in2p3.fr/recherche/eros/GSA/EROS2-GSA-periodic.html)
- ID:
- ivo://CDS.VizieR/J/A+A/536/A60
- Title:
- EROS-2 Long Period Variables in LMC
- Short Name:
- J/A+A/536/A60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The EROS-2 survey has produced a database of millions of time series from stars monitored for more than six years, allowing us to classify some of their sources into different variable star types. Among the so-called, long period variables (LPVs), which are known to follow particular sequences in the period-luminosity diagram, we find long secondary period variables whose variability origin remains a matter of debate. We analyze data for the 856864 variable stars that have been discovered in the Large Magellanic Cloud (LMC) that are present in the EROS-2 database, to detect, classify, and characterize LPVs.
- ID:
- ivo://CDS.VizieR/J/A+A/303/137
- Title:
- EROS Variables: Cepheids in the bar of LMC
- Short Name:
- J/A+A/303/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD phase-binned light curves at 490nm for 97 Cepheid variable stars in the bar of the LMC. The photometry was obtained as part of the French EROS project and has excellent phase coverage, permitting accurate decomposition into Fourier components. We identify as `sinusoidal' or s-Cepheids those stars with periods less than 5.5d and small second-harmonic components. These stars comprise ~30% of our sample and most form a sequence ~1mag brighter than the LMC classical Cepheids in the period-luminosity diagram. They are also generally bluer and have lower-amplitude light curves. We infer that the s-Cepheids are first-overtone pulsators because, when their periods are converted to expected fundamental-mode values, they obey a common period-luminosity-colour relation with classical Cepheids. This also confirms the reality of the colour term in the Cepheid period-luminosity-colour relation. Further, the blue edge of the classical Cepheid instability strip agrees well with the theoretical calculations for the fundamental mode made by Chiosi et al. 1993 (=1993ApJS...86..541C) for the Hertzsprung-Russell and period-luminosity diagrams, but we find that our observed s-Cepheids are >0.2mag brighter and bluer than the Chiosi et al. predictions for the first-overtone. We identify a number of features in plots of our stars' Fourier-component amplitude ratios and phase differences. These features have been identified with resonances between different pulsation modes. In the LMC we find these features seem to occur at periods very similar to Galactic ones for classical Cepheids, but at different periods for s-Cepheids. We discover a double-mode Cepheid in the LMC, for which P(first overtone)/P(fundamental)=0.710+/-0.001, very similar to observed ratios for Galactic double-mode Cepheids.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/3039
- Title:
- Eruptive variable protostars from VVV EW
- Short Name:
- J/MNRAS/465/3039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In a companion work (Contreras Pena et al., 2017MNRAS.465.3011C, Paper I), we detected a large population of highly variable Young Stellar Objects (YSOs) in the Vista Variables in the Via Lactea (VVV) survey, typically with class I or flat spectrum spectral energy distributions and diverse light-curve types. Here we present infrared spectra (0.9-2.5 {mu}m) of 37 of these variables, many of them observed in a bright state. The spectra confirm that 15/18 sources with eruptive light curves have signatures of a high accretion rate, either showing EXor-like emission features ({Delta}v=2 CO, Br{gamma}) and/or FUor-like features ({Delta}v=2 CO and H_2_O strongly in absorption). Similar features were seen in some long-term periodic YSOs and faders but not in dippers or short-term variables. The sample includes some dusty Mira variables (typically distinguished by smooth Mira-like light curves), two cataclysmic variables and a carbon star. In total, we have added 19 new objects to the broad class of eruptive variable YSOs with episodic accretion. Eruptive variable YSOs in our sample that were observed at bright states show higher accretion luminosities than the rest of the sample. Most of the eruptive variables differ from the established FUor and EXor subclasses, showing intermediate outburst durations and a mixture of their spectroscopic characteristics. This is in line with a small number of other recent discoveries. Since these previously atypical objects are now the majority amongst embedded members of the class, we propose a new classification for them as MNors. This term (pronounced emnor) follows V1647 Ori, the illuminating star of McNeil's Nebula.
- ID:
- ivo://CDS.VizieR/J/PASP/132/K4202
- Title:
- Evryscope-South survey
- Short Name:
- J/PASP/132/K4202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using photometric data collected by Evryscope-South, we search for nearby young variable systems on the upper main sequence (UMS) and pre-main sequence (PMS). The Evryscopes are all-sky high-cadence telescope arrays operating in the Northern and Southern hemispheres. We base our search on a Gaia-selected catalog of young neighborhood upper- and pre-main sequence stars which were chosen through both astrometric and photometric criteria. We analyze 44971 Evryscope-South light curves in search of variability. We recover 615 variables, with 378 previously known, and 237 new discoveries including 84 young eclipsing binaries (EB) candidates. We discover a new highly eccentric binary system and recover a further four previously known systems, with periods ranging from 299 to 674hr. We find 158 long-period (>50hr) candidate EB systems, 9 from the PMS and 149 from the UMS, which will allow constraints on the mass/radius/age relation. These long-period EBs include a 179.3hr PMS system and a 867.8hr system from the UMS. For PMS variable candidates we estimate system ages, which range from 1 to 23Myr for non-EBs and from 2 to 17Myr for EBs. Other non-EB discoveries that show intrinsic variability will allow relationships between stellar rotation rates, ages, activity, and mass to be characterized.
- ID:
- ivo://CDS.VizieR/J/MNRAS/495/4924
- Title:
- Exoplanets in Southern open clusters
- Short Name:
- J/MNRAS/495/4924
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The scope of the project 'A PSF-based Approach to TESS High Quality data Of Stellar clusters' (PATHOS) is the extraction and analysis of high-precision light curves of stars in stellar clusters and young associations for the identification of candidate exoplanets and variable stars. The cutting-edge tools used in this project allow us to measure the real flux of stars in dense fields, minimizing the effects due to contamination by neighbour sources. We extracted about 200000 light curves of stars in 645 open clusters located in the Southern ecliptic hemisphere and observed by TESS during the first year of its mission. We searched for transiting signals and we found 33 objects of interest, 11 of which are strong candidate exoplanets. Because of the limited SNR, we did not find any Earth or super-Earth. We identified two Neptune-size planets orbiting stars with R*<1.5R_{sun}_, implying a frequency f*=1.3+/-0.95 per cent consistent with the frequency around field stars. The seven Jupiter candidates around stars with R*<1.5R_{sun}_ imply a frequency f*=0.19+/-0.07 per cent, which is smaller than in the field. more complete estimate of the survey completeness and false positive rate is needed to confirm these results. Light curves used in this work will be made available to the astronomical community on the Mikulski Archive for Space Telescope under the project PATHOS.
