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591. JHK photometry of 1203 variables in ONC
ID:
ivo://CDS.VizieR/J/AJ/150/132
Title:
JHK photometry of 1203 variables in ONC
Short Name:
J/AJ/150/132
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using UKIRT on Mauna Kea, we have carried out a new near-infrared J, H, K monitoring survey of almost a square degree of the star-forming Orion Nebula Cluster with observations on 120 nights over three observing seasons, spanning a total of 894 days. We monitored ~15000 stars down to J~20 using the WFCAM instrument, and have extracted 1203 significantly variable stars from our data. By studying variability in young stellar objects (YSOs) in the H-K, K color-magnitude diagram, we are able to distinguish between physical mechanisms of variability. Many variables show color behavior indicating either dust-extinction or disk/accretion activity, but we find that when monitored for longer periods of time, a number of stars shift between these two variability mechanisms. Further, we show that the intrinsic timescale of disk/accretion variability in young stars is longer than that of dust-extinction variability. We confirm that variability amplitude is statistically correlated with evolutionary class in all bands and colors. Our investigations of these 1203 variables have revealed 73 periodic AA Tau type variables, many large-amplitude and long-period (P>15 days) YSOs, including three stars showing widely spaced periodic brightening events consistent with circumbinary disk activity, and four new eclipsing binaries. These phenomena and others indicate the activity of long-term disk/accretion variability processes taking place in young stars. We have made the light curves and associated data for these 1203 variables available online.
592. JHKs magnitudes of variables in NGC 5128
ID:
ivo://CDS.VizieR/J/A+A/406/75
Title:
JHKs magnitudes of variables in NGC 5128
Short Name:
J/A+A/406/75
Date:
21 Oct 2021
Publisher:
CDS
Description:
The first variable star catalogue in a giant elliptical galaxy NGC 5128 (Centaurus A) is presented. Using multi-epoch observations with ISAAC at the VLT we have detected 1504 red variables in two halo fields covering 10.46-arcmin square. For the variables with at least 10 good measurements, periods and amplitudes were determined using Fourier analysis and non-linear sine-curve fitting algorithms. The final catalogue contains 1146 long period variables with well established light curve parameters. Periods, amplitudes, JsHKs photometry as well as individual KS-band magnitudes are provided for all the variables. The distribution of amplitudes ranges from 0.3 to a few magnitudes in the Ks-band, with a median value around 0.7mag. The amplitudes, mean magnitudes and periods indicate that the majority of variables belong to the class of long period variables with semiregular and Mira variables. Exhaustive simulations were performed in order to assess the completeness of our catalogue and the accuracy of the derived periods.
593. JHKs photometry of Cha I variables
ID:
ivo://CDS.VizieR/J/AJ/124/1001
Title:
JHKs photometry of Cha I variables
Short Name:
J/AJ/124/1001
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of a J, H, and Ks photometric monitoring campaign of a 0.72{deg}x6{deg} area centered on the Chamaeleon I star-forming region. Data were obtained on 15 separate nights over a 4 month time interval, from January to May 2000, using the Two Micron All Sky Survey south telescope. Out of a total of 34,539 sources brighter than the photometric completeness limits (J=16.0, H=15.2, and Ks=14.8), 95 exhibit near-infrared variability in one or more bands. The variables can be grouped into a population of bright, red objects that are associated with the Chamaeleon I association and a population of faint, blue variables that are dispersed over the full 6{deg} of the survey and are likely field stars or older pre-main-sequence stars unrelated to the present-day Chamaeleon I molecular cloud. Ten new candidate members of Chamaeleon I, including eight brown dwarf candidates, have been identified based on variability and/or near-infrared-excess emission in the J-H versus H-Ks color-color diagram. We also provide a compendium of astrometry and J, H, and Ks photometry for previously identified members and candidate members of Chamaeleon I.
594. JHKs photometry of 92 LMC Cepheids
ID:
ivo://CDS.VizieR/J/AJ/128/2239
Title:
JHKs photometry of 92 LMC Cepheids
Short Name:
J/AJ/128/2239
Date:
21 Oct 2021
Publisher:
CDS
Description:
Near-infrared J, H, and K_s_ photometric measurements of 92 Cepheids in the Large Magellanic Cloud are presented. The stars are spread over the face of the Cloud, their periods range from 3 to 100 days, and their light curves are sampled at an average of 22 phase points per star. The intensity-weighted mean magnitudes and colors define period-luminosity-color (PL or PLC) relations whose uncertainties due to differential metal abundance and reddening/extinction effects are minimal. The dispersions in the infrared PL, PLC, and extinction-free period-Wesenheit relations are extremely small, amounting to less than 0.10mag (or 5% in distance).
595. JHKs photometry of LMC cluster Cepheids
ID:
ivo://CDS.VizieR/J/A+A/462/599
Title:
JHKs photometry of LMC cluster Cepheids
Short Name:
J/A+A/462/599
Date:
21 Oct 2021
Publisher:
CDS
Description:
This work presents IR photometry for two young clusters known to contain sizeable Cepheid populations: NGC 1866 and NGC 2031. The goal is to determine light curves and period-luminosity (PL) relations in the near-IR, to assess the similarity between cluster and field pulsators, and to examine the predictive capability of current pulsation models. The light curves are obtained from multiwavelength broadband J,H,Ks photometry of Cepheids in both clusters, with periods previously established from optical photometry. Mean magnitudes for the Cepheids are used to construct period-luminosity (PL) relations in the near-IR. The properties in the PL planes are compared with the behavior of field Cepheids in the LMC and with the predictions of recent pulsational models, both canonical and overluminous. Cluster and field Cepheids are homogeneous and the inclusion of the cluster Cepheids in the field sample extends the PL relation. The slope of the PL relation is constant over the whole period range and does not show, at least in the adopted IR bands, the break in slope at P~10d reported by some authors. A comparison with the predictions of pulsation models allows an estimate for the distance moduli of NGC 1866 and NGC 2031. The two clusters are found to lie at essentially the same distance. Fitting of theoretical models to the data gives, for the K filter, (m-M)_0_=18.62+/-0.10 if canonical models are used and (m-M)_0_=18.42+/-0.10 if overluminous models are used.
596. JHKs photometry of LPVs in M33
ID:
ivo://CDS.VizieR/J/A+A/487/131
Title:
JHKs photometry of LPVs in M33
Short Name:
J/A+A/487/131
Date:
21 Oct 2021
Publisher:
CDS
Description:
Wide-field JHKs near-infrared observations covering an area of 1.8x1.8deg^2^ centred on M33 were obtained using WFCAM at UKIRT. These data show a large population of intermediate-age asymptotic giant branch stars (AGB). We have used both C-type and M-type AGB stars to determine spatial variations in metallicity and mean age across the galaxy. We distinguished between C-type and M-type AGB stars from their location in the colour-magnitude diagram (J-Ks, Ks). The distribution of these stars is supported by a cross-identification between our sample and a catalogue of optically confirmed, long-period variable stars, as well as with the list of sources detected by Spitzer in the mid-infrared. We calculated the C/M ratio and the orientation of the galaxy in the sky, and compared the Ks magnitude distribution with theoretical distributions spanning a range of metallicities and star formation rates (SFRs). The C/M ratio surface map confirms a metallicity gradient in the galaxy corresponding to a spread in [Fe/H]=0.6dex with substructures in the inner and outer galaxy. Magnitude and colour variations suggest orientation and extinction effects on the galaxy disc. Maps showing the distribution of mean age and metallicity obtained from the Ks method suggest that: the outer galaxy disc/halo is metal poorer than the nuclear region and metal-rich clumps in the inner galaxy change location with time. The average outer ring and nuclear stellar population is ~6Gyr old while central regions are a few Gyr younger.
597. JHKs photometry of T2Cs in globular clusters
ID:
ivo://CDS.VizieR/J/MNRAS/370/1979
Title:
JHKs photometry of T2Cs in globular clusters
Short Name:
J/MNRAS/370/1979
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the result of our near-infrared observations (JHKs) for type II Cepheids (including possible RV Tau stars) in galactic globular clusters. We detected variations of 46 variables in 26 clusters (10 new discoveries in seven clusters) and present their light curves. Their periods range from 1.2d to over 80d. They show a well-defined period-luminosity relation at each wavelength. Two type II Cepheids in NGC 6441 also obey the relation if we assume the horizontal branch stars in NGC 6441 are as bright as those in metal-poor globular clusters in spite of the high metallicity of the cluster.
598. JHKs photometry of VVV RR Lyrae stars
ID:
ivo://CDS.VizieR/J/ApJ/857/54
Title:
JHKs photometry of VVV RR Lyrae stars
Short Name:
J/ApJ/857/54
Date:
21 Oct 2021
Publisher:
CDS
Description:
RR Lyrae stars (RRLs) are tracers of the Milky Way's fossil record, holding valuable information on its formation and early evolution. Owing to the high interstellar extinction endemic to the Galactic plane, distant RRLs lying at low Galactic latitudes have been elusive. We attained a census of 1892 high-confidence RRLs by exploiting the near-infrared photometric database of the VVV survey's disk footprint spanning ~70{deg} of Galactic longitude, using a machine-learned classifier. Novel data-driven methods were employed to accurately characterize their spatial distribution using sparsely sampled multi-band photometry. The RRL metallicity distribution function (MDF) was derived from their K_s_-band light-curve parameters using machine-learning methods. The MDF shows remarkable structural similarities to both the spectroscopic MDF of red clump giants and the MDF of bulge RRLs. We model the MDF with a multi-component density distribution and find that the number density of stars associated with the different model components systematically changes with both the Galactocentric radius and vertical distance from the Galactic plane, equivalent to weak metallicity gradients. Based on the consistency with results from the ARGOS survey, three MDF modes are attributed to the old disk populations, while the most metal-poor RRLs are probably halo interlopers. We propose that the dominant [Fe/H] component with a mean of -1dex might correspond to the outskirts of an ancient Galactic spheroid or classical bulge component residing in the central Milky Way. The physical origins of the RRLs in this study need to be verified by kinematical information.
599. JHKs, WISE and Spitzer data of Galactic Cepheids
ID:
ivo://CDS.VizieR/J/ApJ/852/78
Title:
JHKs, WISE and Spitzer data of Galactic Cepheids
Short Name:
J/ApJ/852/78
Date:
21 Oct 2021
Publisher:
CDS
Description:
Classical Cepheids are well-known and widely used distance indicators. As distance and extinction are usually degenerate, it is important to develop suitable methods to robustly anchor the distance scale. Here, we introduce a near-infrared optimal distance method to determine both the extinction values of and distances to a large sample of 288 Galactic classical Cepheids. The overall uncertainty in the derived distances is less than 4.9%. We compare our newly determined distances to the Cepheids in our sample with previously published distances to the same Cepheids with Hubble Space Telescope parallax measurements and distances based on the IR surface brightness method, Wesenheit functions, and the main-sequence fitting method. The systematic deviations in the distances determined here with respect to those of previous publications is less than 1%-2%. Hence, we constructed Galactic mid-IR period-luminosity (PL) relations for classical Cepheids in the four Wide-Field Infrared Survey Explorer (WISE) bands (W1, W2, W3, and W4) and the four Spitzer Space Telescope bands ([3.6], [4.5], [5.8], and [8.0]). Based on our sample of hundreds of Cepheids, the WISE PL relations have been determined for the first time; their dispersion is approximately 0.10mag. Using the currently most complete sample, our Spitzer PL relations represent a significant improvement in accuracy, especially in the [3.6] band which has the smallest dispersion (0.066mag). In addition, the average mid-IR extinction curve for Cepheids has been obtained: A_W1_/A_Ks_~0.560, A_W2_/A_Ks_~0.479, A_W3_/A_Ks_~0.507, A_W4_/A_Ks_~0.406, A_[3.6]_/A_Ks_~0.481, A_[4.5]_/A_Ks_~0.469, A_[5.8]_/A_Ks_~0.427, and A_[8.0]_/A_Ks_~0.427mag.
600. JHK variable stars in M33
ID:
ivo://CDS.VizieR/J/MNRAS/411/263
Title:
JHK variable stars in M33
Short Name:
J/MNRAS/411/263
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have conducted a near-infrared monitoring campaign at the UK InfraRed Telescope (UKIRT), of the Local Group spiral galaxy M 33 (Triangulum). The main aim was to identify stars in the very final stage of their evolution, and for which the luminosity is more directly related to the birth mass than the more numerous less-evolved giant stars that continue to increase in luminosity. The most extensive dataset was obtained in the K-band with the UIST instrument for the central 4'x4' (1kpc^2^) --- this contains the nuclear star cluster and inner disc. These data, taken during the period 2003-2007, were complemented by J- and H-band images. Photometry was obtained for 18,398 stars in this region; of these, 812 stars were found to be variable, most of which are Asymptotic Giant Branch (AGB) stars. Our data were matched to optical catalogues of variable stars and carbon stars, and to mid-infrared photometry from the Spitzer Space Telescope. In this first of a series of papers, we present the methodology of the variability survey and the photometric catalogue, which is made publicly available at the Centre de Donnees astronomiques de Strasbourg (CDS), and discuss the properties of the variable stars. Most dusty AGB stars had not been previously identified in optical variability surveys, and our survey is also more complete for these types of stars than the Spitzer survey.