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- ID:
- ivo://CDS.VizieR/J/AJ/145/113
- Title:
- JHK photometry in Cyg OB7. II. Variable stars
- Short Name:
- J/AJ/145/113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a subset of the results of a three-season, 124 nights, near-infrared monitoring campaign of the dark clouds Lynds 1003 and Lynds 1004 in the Cygnus OB7 star-forming region. In this paper, we focus on the field star population. Using three seasons of UKIRT J, H, and K-band observations spanning 1.5 years, we obtained high-quality photometry on 9200 stars down to J=17mag, with photometric uncertainty better than 0.04mag. After excluding known disk-bearing stars we identify 149 variables-1.6% of the sample. Of these, about 60 are strictly periodic, with periods predominantly <2days. We conclude this group is dominated by eclipsing binaries. A few stars have long period signals of between 20 and 60 days. About 25 stars have weak modulated signals, but it was not clear if these were periodic. Some of the stars in this group may be diskless young stellar objects with relatively large variability due to cool starspots. The remaining ~60 stars showed variations which appear to be purely stochastic.
- ID:
- ivo://CDS.VizieR/J/AJ/121/3160
- Title:
- JHK photometry near the Trapezium region
- Short Name:
- J/AJ/121/3160
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of J, H, and Ks time-series photometry obtained with the southern 2MASS telescope over a 0.84{deg}x6{deg} region centered near the Trapezium region of the Orion Nebula cluster. These data are used to establish the near-infrared variability properties of premain-sequence stars in Orion on timescales of ~1-36days, ~2 months, and ~2 years. A total of 1235 near-infrared variable stars are identified, ~93% of which are likely associated with the Orion A molecular cloud.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2714
- Title:
- JHK photometry of M92 variable stars
- Short Name:
- J/AJ/129/2714
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present near-infrared (NIR) J-, H-, and K-band time series observations of the Galactic globular cluster (GGC) M92.
- ID:
- ivo://CDS.VizieR/J/ApJS/193/12
- Title:
- JHK photometry of Northern Galactic Cepheids
- Short Name:
- J/ApJS/193/12
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared photometric measurements for 131 Northern Galactic Cepheids are presented. The Cepheid light curves are sampled with an average of 22 measurements per star fully covering the phase of each Cepheid. The J, H, and K light curves for each Cepheid were uniformly interpolated to find the intensity mean magnitudes within each band. The results are consistent within +/-1% for 26 stars in common with previous studies. This paper is the first in a projected series of two papers which will provide additional fundamental data for Cepheids in the Galaxy, namely, NIR photometry and line-of-sight extinction. In the course of this project, 93 additional variables were fortuitously observed within the Cepheid program fields, 82 of which have previously not been identified.
- 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.
- 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.
- 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.
- 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).
- 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.
