- ID:
- ivo://CDS.VizieR/J/ApJS/237/28
- Title:
- WISE catalog of periodic variable stars
- Short Name:
- J/ApJS/237/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled the first all-sky mid-infrared variable-star catalog based on Wide-field Infrared Survey Explorer five-year survey data. Requiring more than 100 detections for a given object, 50282 carefully and robustly selected periodic variables are discovered, of which 34769 (69%) are new. Most are located in the Galactic plane and near the equatorial poles. A method to classify variables based on their mid-infrared light curves is established using known variable types in the General Catalog of Variable Stars. Careful classification of the new variables results in a tally of 21427 new EW-type eclipsing binaries, 5654 EA-type eclipsing binaries, 1312 Cepheids, and 1231 RR Lyrae. By comparison with known variables available in the literature, we estimate that the misclassification rate is 5% and 10% for short- and long- period variables, respectively. A detailed comparison of the types, periods, and amplitudes with variables in the Catalina catalog shows that the independently obtained classifications parameters are in excellent agreement. This enlarged sample of variable stars will not only be helpful to study Galactic structure and extinction properties, but can also be used to constrain stellar evolution theory and provide potential candidates for the James Webb Space Telescope.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/453/133
- Title:
- WISE view of RV Tauri stars
- Short Name:
- J/MNRAS/453/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed study based on infrared (IR) photometry of all Galactic RV Tauri stars from the General Catalogue of Variable Stars (GCVS). RV Tauri stars are the brightest among the Population II Cepheids. They are thought to evolve away from the asymptotic giant branch (AGB) towards the white dwarf domain. IRAS detected several RV Tauri stars because of their large IR excesses and it was found that they occupy a specific region in the [12]-[25], [25]-[60] IRAS two-colour diagram. We used the all sky survey of Wide-field Infrared Survey Explorer to extend these studies and compare the IR properties of all RV Tauri stars in the GCVS with a selected sample of post-AGB objects with the goal to place the RV Tauri pulsators in the context of post-AGB evolution. Moreover, we correlated the IR properties of both the RV Tauri stars and the comparison sample with other observables like binarity and the presence of a photospheric chemical anomaly called depletion. We find that Galactic RV Tauri stars display a range of IR properties and we differentiate between disc sources, objects with no IR excess and objects for which the spectral energy distribution (SED) is uncertain. We obtain a clear correlation between disc sources and binarity. RV Tauri stars with a variable mean magnitude are exclusively found among the disc sources. We also find evidence for disc evolution among the binaries. Furthermore our studies show that the presence of a disc seems to be a necessary but not sufficient condition for the depletion process to become efficient.
- ID:
- ivo://CDS.VizieR/J/AJ/162/92
- Title:
- 126 X-rays sources around the cepheid {eta} Aql
- Short Name:
- J/AJ/162/92
- Date:
- 14 Mar 2022 07:02:20
- Publisher:
- CDS
- Description:
- X-ray bursts have recently been discovered in the Cepheids {delta}Cep and {beta}Dor modulated by the pulsation cycle. We have obtained an observation of the Cepheid {eta}Aql with the XMM-Newton satellite at the phase of maximum radius; the phase at which there is a burst of X-rays in {delta}Cep. No X-rays were seen from the Cepheid {eta}Aql at this phase, and the implications for Cepheid upper atmospheres are discussed. We have also used the combination of X-ray sources, as well as Gaia and 2MASS data, to search for a possible grouping around the young intermediate mass Cepheid. No indication of such a group was found.
- ID:
- ivo://CDS.VizieR/J/MNRAS/427/1517
- Title:
- XY And and UZ Vir light curves
- Short Name:
- J/MNRAS/427/1517
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a thorough analysis of multicolour CCD observations of two modulated RRab-type variables, XY And and UZ Vir. These Blazhko stars show relatively simple light-curve modulation with the usual multiplet structures in their Fourier spectra. One additional, independent frequency with linear-combination terms of the pulsation frequency is also detected in the residual spectrum of each of the two stars. The amplitude and phase relations of the triplet components are studied in detail. Most of the epoch-independent phase differences show a slight, systematic colour dependence. However, these trends have opposite signs in the two stars. The mean values of the global physical parameters and their changes with the Blazhko phase are determined, utilizing the inverse photometric method (IPM). The modulation properties and the IPM results are compared for the two variables. The pulsation period of XY And is the shortest when its pulsation amplitude is the highest, while UZ Vir has the longest pulsation period at this phase of the modulation. Despite this contrasting behaviour, the phase relations of the variations in their mean physical parameters are similar. These results do not agree with the predictions of the Blazhko model of Stothers.
- ID:
- ivo://CDS.VizieR/J/ApJS/190/203
- Title:
- 3.6 years of DIRBE NIR stellar light curves
- Short Name:
- J/ApJS/190/203
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The weekly averaged near-infrared fluxes for 2652 stars were extracted from the cold and warm era all-sky maps of the Diffuse Infrared Background Experiment (DIRBE). Since the DIRBE program only archived the individual Calibrated Infrared Observations for the 10 month cold era mission, the weekly averaged fluxes were all that were available for the warm era. The steps required to extract stellar fluxes are described as are the adjustments that were necessary to correct the results for several systematic effects. The observations are at a cadence of once a week for 3.6 years (~1300 days), providing continuous sampling on variable stars that span the entire period for the longest fundamental pulsators. The stars are divided into three categories: those with large amplitude of variability, smaller amplitude variables, and sources whose near-infrared brightness do not vary according to our classification criteria. We show examples of the results and the value of the added baseline in determining the phase lag between the visible and infrared.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/38
- Title:
- 25-years photometry of V1057 Cygni
- Short Name:
- J/MNRAS/434/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The FU Orionis type of variable star (FUor), V1057 Cygni, underwent a nova-like outburst in 1969-1970. Among the FUors, V1057 Cyg is notable for having the most dramatic post-maximum decrease in brightness. Thus, photometric monitoring of this object is important for interpretations of the cause of this event. Here, we study the behaviour of V1057 Cyg over the last 25 years on the basis of our optical and infrared observations. The optical and near-infrared observations of V1057 Cyg started in 1974, and we present all our data (up to the end of 2011), including 1085 and 167 nights of optical and infrared photometry, respectively. The UBVRIJHKLM light curves for 1985-2011 show that despite the increased photometric activity, after a rapid decrease in brightness in the mid-1990s, the average level of brightness remained practically constant. After the object becomes fainter than V~11.5mag, a swerve appears in the track of the colour-magnitude diagram. The light variability shows a different periodicity in different spectral regions. We have discovered a period of 1631+/-60d in the BVR bands (1995-2011) and 523+/-40d in the RIJHK bands (2002-2011) with amplitudes of 0.5-0.3mag. The 523-d period is presumably correlated with the changes in the radial velocity of an emission component in LiI. We conclude that the observed properties of the FUor star V1057 Cyg are in accordance with current models of FUors involving binary or multiple systems.
- ID:
- ivo://CDS.VizieR/J/MNRAS/472/808
- Title:
- YJKs light curves of SMC Classical Cepheids
- Short Name:
- J/MNRAS/472/808
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The VISTA near-infrared YJKs survey of the Magellanic System (VMC) is collecting deep Ks-band time-series photometry of pulsating stars hosted by the two Magellanic Clouds and their connecting bridge. Here, we present Y, J, Ks light curves for a sample of 717 Small Magellanic Cloud (SMC) Classical Cepheids (CCs). These data, complemented with our previous results and V magnitude from literature, allowed us to construct a variety of period-luminosity and period-Wesenheit relationships, valid for Fundamental, First and Second Overtone pulsators. These relations provide accurate individual distances to CCs in the SMC over an area of more than 40 deg^2^. Adopting literature relations, we estimated ages and metallicities for the majority of the investigated pulsators, finding that (i) the age distribution is bimodal, with two peaks at 120+/-10 and 220+/-10Myr; (i) the more metal-rich CCs appear to be located closer to the centre of the galaxy. Our results show that the three-dimensional distribution of the CCs in the SMC is not planar but heavily elongated for more than 25-30kpc approximately in the east/north-east towards south-west direction. The young and old CCs in the SMC show a different geometric distribution. Our data support the current theoretical scenario predicting a close encounter or a direct collision between the Clouds some 200Myr ago and confirm the presence of a Counter-Bridge predicted by some models. The high-precision three-dimensional distribution of young stars presented in this paper provides a new test bed for future models exploring the formation and evolution of the Magellanic System.
- ID:
- ivo://CDS.VizieR/J/ApJ/848/97
- Title:
- Young stellar variables with KELT for K2. I.
- Short Name:
- J/ApJ/848/97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- One of the most well-studied young stellar associations, Taurus-Auriga, was observed by the extended Kepler mission, K2, in the spring of 2017. K2 Campaign 13 (C13) is a unique opportunity to study many stars in this young association at high photometric precision and cadence. Using observations from the Kilodegree Extremely Little Telescope (KELT) survey, we identify "dippers," aperiodic and periodic variables among K2 C13 target stars. This release of the KELT data provides the community with long-time baseline observations to assist in the understanding of the more exotic variables in the association. Transient-like phenomena on timescales of months to years are known characteristics in the light curves of young stellar objects, making contextual pre- and post-K2 observations critical to understanding their underlying processes. We are providing a comprehensive set of the KELT light curves for known Taurus-Auriga stars in K2 C13. The combined data sets from K2 and KELT should permit a broad array of investigations related to star formation, stellar variability, and protoplanetary environments.
- ID:
- ivo://CDS.VizieR/J/ApJ/878/7
- Title:
- 2yr obs. of JHK variability of stars in Tr37
- Short Name:
- J/ApJ/878/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have monitored nearly a square degree in IC 1396A/Tr 37 over 21 epochs extending over 2014-2016 for sources variable in the JHK bands. In our data, 65%+/-8% of previously identified cluster members show variations, compared with <=0.3% of field stars. We identify 119 members of Tr 37 on the basis of variability, forming an unbiased sample down to the brown dwarf regime. The K-band luminosity function in Tr 37 is similar to that of IC 348 but shifted to somewhat brighter values, implying that the K- and M-type members of Tr 37 are younger than those in IC 348. We introduce methods to classify the causes of variability, based on behavior in the color-color and color-magnitude diagrams. Accretion hot spots cause larger variations at J than at K with substantial scatter in the diagrams; there are at least a dozen, with the most active resembling EXors. Eleven sources are probably dominated by intervention of dust clumps in their circumstellar disks, with color behavior indicating the presence of grains larger than for interstellar dust, presumably due to grain growth in their disks. Thirteen sources have larger variations at K than at J or H. For 11 of them, the temperature fitted to the variable component is very close to 2000K, suggesting that the changes in output are caused by turbulence at the inner rim of the circumstellar disk exposing previously protected populations of grains.
- ID:
- ivo://CDS.VizieR/J/AJ/150/145
- Title:
- YSOVAR infrared photometry in GGD12-15
- Short Name:
- J/AJ/150/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an IR-monitoring survey with the Spitzer Space Telescope of the star-forming region GGD 12-15. More than 1000 objects were monitored, including about 350 objects within the central 5', which is found to be especially dense in cluster members. The monitoring took place over 38 days and is part of the Young Stellar Object VARiability project. The region was also the subject of a contemporaneous 67 ks Chandra observation. The field includes 119 previously identified pre-main sequence star candidates. X-rays are detected from 164 objects, 90 of which are identified with cluster members. Overall, we find that about half the objects in the central 5' are young stellar objects (YSOs) based on a combination of their spectral energy distribution, IR variability, and X-ray emission. Most of the stars with IR excess relative to a photosphere show large amplitude (>0.1 mag) mid-infrared (mid-IR) variability. There are 39 periodic sources, and all but one is found to be a cluster member. Almost half of the periodic sources do not show IR excesses. Overall, more than 85% of the Class I, flat spectrum, and Class II sources are found to vary. The amplitude of the variability is larger in more embedded YSOs. Most of the Class I/II objects exhibit redder colors in a fainter state, which is compatible with time-variable extinction. A few become bluer when fainter, which can be explained with significant changes in the structure of the inner disk. A search for changes in the IR due to X-ray events is carried out, but the low number of flares prevented an analysis of the direct impact of X-ray flares on the IR light curves. However, we find that X-ray detected Class II sources have longer timescales for change in the MIR than a similar set of non-X-ray detected Class IIs.