- ID:
- ivo://CDS.VizieR/J/MNRAS/386/313
- Title:
- IR observations of Mira variables
- Short Name:
- J/MNRAS/386/313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Published data for large-amplitude asymptotic giant branch variables in the Large Magellanic Cloud (LMC) are re-analysed to establish the constants for an infrared (K) period-luminosity relation of the form MK={rho}[logP-2.38]+{delta}. A slope of {rho}=-3.51+/-0.20 and a zero-point of {delta}=-7.15+/-0.06 are found for oxygen-rich Miras (if a distance modulus of 18.39+/-0.05 is used for the LMC). Assuming this slope is applicable to Galactic Miras we discuss the zero-point for these stars using the revised Hipparcos parallaxes together with published very long baseline interferometry (VLBI) parallaxes for OH masers and Miras in globular clusters. These result in a mean zero-point of {delta}=-7.25+/-0.07 for O-rich Galactic Miras. The zero-point for Miras in the Galactic bulge is not significantly different from this value.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/566/A37
- Title:
- Iron abundances for 42 Galactic Cepheids
- Short Name:
- J/A+A/566/A37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present homogeneous and accurate iron abundances for 42 Galactic Cepheids based on high resolution (R~38000) high signal-to-noise ratio (S/N>=100) optical spectra collected with UVES at VLT (128 spectra). The above abundances were complemented with high-quality iron abundances provided either by our group (86) or available in the literature. We were careful to derive a common metallicity scale and ended up with a sample of 450 Cepheids. We also estimated accurate individual distances for the entire sample by using homogeneous near-infrared photometry and the reddening free period-Wesenheit relations. The new metallicity gradient is linear over a broad range of Galactocentric distances (R_G_~5-19kpc) and agrees quite well with similar estimates available in the literature (-0.060+/-0.002dex/kpc). We also uncover evidence that suggests that the residuals of the metallicity gradient are tightly correlated with candidate Cepheid groups (CGs). The candidate CGs have been identified as spatial overdensities of Cepheids located across the thin disk. They account for a significant fraction of the residual fluctuations, and also for the large intrinsic dispersion of the metallicity gradient. We performed a detailed comparison with metallicity gradients based on different tracers: OB stars and open clusters. We found very similar metallicity gradients for ages younger than 3Gyr, while for older ages we found a shallower slope and an increase in the intrinsic spread. The above findings rely on homogeneous age, metallicity, and distance scales. Finally, by using a large sample of Galactic and Magellanic Cepheids for which accurate iron abundances are available, we found that the dependence of the luminosity amplitude on metallicity is vanishing.
- ID:
- ivo://CDS.VizieR/J/AJ/158/105
- Title:
- IR photometry of field RR Lyrae variable stars
- Short Name:
- J/AJ/158/105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch infrared photometry in the K_s_-band for 74 bright RR Lyrae variable stars tied directly to the Two-Micron All-Sky Survey (2MASS) photometric system. We systematize additional K-band photometry from the literature to the 2MASS system and combine it to obtain photometry for 146 RR Lyrae stars on a consistent, modern system. A set of outlier stars in the literature photometry is identified and discussed. Reddening estimates for each star are gathered from the literature and combined to provide an estimate of the interstellar absorption affecting each star, and we find excellent agreement with another source in the literature. We utilize trigonometric parallaxes from the Second Data Release of the European Space Agency's Gaia astrometric satellite to determine the absolute magnitude, M_Ks_ for each of these stars, and analyze them using the astrometry-based luminosity prescription to obtain a parallax-based calibration of M_K_ (RR). Our period-luminosity-metallicity relationship is M_Ks_=(-2.8+/-0.2)(logP+0.27)+(0.12+/-0.02) ([Fe/H]+1.3)-(0.41+/-0.03) mag. A Gaia global zero-point error of {pi}_zp_=-0.042+/-0.013 mas is determined for this sample of RR Lyrae stars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/273
- Title:
- IR photometry of NGC 1893 variables
- Short Name:
- J/MNRAS/442/273
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present time series photometry of 104 variable stars in the cluster region NGC 1893. The association of the present variable candidates to the cluster NGC 1893 has been determined by using (U-B)/(B-V) and (J-H)/(H-K) two colour diagrams, and V/(V-I) colour-magnitude diagram. 45 stars are found to be main-sequence variables and these could be B-type variable stars associated with the cluster. We classified these objects as {beta} Cep, slowly pulsating B stars and new class variables as discussed by Mowlavi et al. (2013, Cat. J/A+A/554/A108). These variable candidates show ~0.005 to ~0.02mag brightness variations with periods of <1.0d. 17 new class variables are located in the H-R diagram between the slowly pulsating B stars and {delta} Scuti variables. Pulsation could be one of the causes for periodic brightness variations in these stars. The X-ray emission of present main-sequence variables associated with the cluster lies in the saturated region of X-ray luminosity versus period diagram and follows the general trend by Pizzolato et al. (2003, Cat. J/A+A/397/147).
- ID:
- ivo://CDS.VizieR/J/MNRAS/481/4206
- Title:
- IRSF survey of variable stars in the SMC
- Short Name:
- J/MNRAS/481/4206
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A very long-term near-infrared variable star survey towards the Large and Small Magellanic Clouds (LMC and SMC) was carried out using the 1.4m InfraRed Survey Facility at the South African Astronomical Observatory. This project was initiated in 2000 December in the LMC, and in 2001 July in the SMC. Since then an area of 3deg^2^ along the bar in the LMC and an area of 1deg^2^ in the central part of the SMC have been repeatedly observed. This survey is ongoing, but results obtained with data taken until 2017 December are reported in this paper. Over more than 15yr we have observed the two survey areas more than one hundred times. This is the first survey that provides near-infrared time-series data with such a long time baseline and on such a large scale. This paper describes the observations in the SMC and publishes a point source photometric catalogue, a variable source catalogue, and time-series data.
- ID:
- ivo://CDS.VizieR/J/AJ/151/146
- Title:
- IRS spectra with features of crystalline silicates
- Short Name:
- J/AJ/151/146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The crystalline silicate features are mainly reflected in infrared bands. The Spitzer Infrared Spectrograph (IRS) collected numerous spectra of various objects and provided a big database to investigate crystalline silicates in a wide range of astronomical environments. We apply the manifold ranking algorithm to perform a systematic search for the spectra with crystalline silicate features in the Spitzer IRS Enhanced Products available. In total, 868 spectra of 790 sources are found to show the features of crystalline silicates. These objects are cross-matched with the SIMBAD database as well as with the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST)/DR2 (Luo et al. 2016, Cat. V/149). The average spectrum of young stellar objects shows a variety of features dominated either by forsterite or enstatite or neither, while the average spectrum of evolved objects consistently present dominant features of forsterite in AGB, OH/IR, post-AGB, and planetary nebulae. They are identified optically as early-type stars, evolved stars, galaxies and so on. In addition, the strength of spectral features in typical silicate complexes is calculated. The results are available through CDS for the astronomical community to further study crystalline silicates.
- ID:
- ivo://CDS.VizieR/J/AJ/155/99
- Title:
- IR variability among YSOs in the Serpens South cluster
- Short Name:
- J/AJ/155/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a time-variability study of young stellar objects (YSOs) in the Serpens South cluster performed at 3.6 and 4.5 {mu}m with the Spitzer Space Telescope; this study is part of the Young Stellar Object VARiability project. We have collected light curves for more than 1500 sources, including 85 cluster members, over 38 days. This includes 44 class I sources, 19 sources with flat spectral energy distributions (SEDs), 17 class II sources, and five diskless YSO candidates. We find a high variability fraction among embedded cluster members of ~70%, whereas young stars without a detectable disk display no variability. We detect periodic variability for 32 sources with periods primarily in the range of 0.2-14 days and a subset of fast rotators thought to be field binaries. The timescale for brightness changes are shortest for stars with the most photospheric SEDs and longest for those with flat or rising SEDs. While most variable YSOs become redder when fainter, as would be expected from variable extinction, about 10% get bluer as they get fainter. One source, SSTYSV J183006.13-020108.0, exhibits "cyclical" color changes.
- ID:
- ivo://CDS.VizieR/J/ApJ/850/137
- Title:
- ISLAndS project. III. Variable stars
- Short Name:
- J/ApJ/850/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a census of variable stars in six M31 dwarf spheroidal satellites observed with the Hubble Space Telescope. We detect 870 RR Lyrae (RRL) stars in the fields of And I (296), II (251), III (111), XV (117), XVI (8), and XXVIII (87). We also detect a total of 15 Anomalous Cepheids, three eclipsing binaries, and seven field RRL stars compatible with being members of the M31 halo or the Giant Stellar Stream. We derive robust and homogeneous distances to the six galaxies using different methods based on the properties of the RRL stars. Working with the up-to-date set of Period-Wesenheit (I, B-I) relations published by Marconi et al., we obtain distance moduli of {mu}0=[24.49, 24.16, 24.36, 24.42, 23.70, 24.43]mag (respectively), with systematic uncertainties of 0.08mag and statistical uncertainties <0.11mag. We have considered an enlarged sample of 16 M31 satellites with published variability studies, and compared their pulsational observables (e.g., periods and amplitudes) with those of 15 Milky Way satellites for which similar data are available. The properties of the (strictly old) RRL in both satellite systems do not show any significant difference. In particular, we found a strikingly similar correlation between the mean period distribution of the fundamental RRL pulsators (RRab) and the mean metallicities of the galaxies. This indicates that the old RRL progenitors were similar at the early stage in the two environments, suggesting very similar characteristics for the earliest stages of evolution of both satellite systems.
- ID:
- ivo://CDS.VizieR/J/A+A/406/51
- Title:
- ISO long period variables in SMC
- Short Name:
- J/A+A/406/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This article presents the study of the light curves extracted from the MACHO database of a sample of stars observed by the Infrared Space Observatory in the Small Magellanic Cloud. These stars belong to the ISO Mini-Survey catalogue of the Magellanic Clouds (ISO MCMS, Loup et al., in preparation). Most of them are in the asymptotic giant branch (AGB) and supergiant phases. The dominant period and amplitude of pulsation have been derived and the stars have been classified as Mira or Semi Regular pulsators.
- ID:
- ivo://CDS.VizieR/J/AcA/54/347
- Title:
- IVB mag of LMC ellipsoidal variables
- Short Name:
- J/AcA/54/347
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the OGLE-II and OGLE-III photometry of red giants in the Large Magellanic Cloud to select and study objects revealing ellipsoidal variability. We detected 1546 candidates for long period ellipsoidal variables and 121 eclipsing binary systems with clear ellipsoidal modulation.
