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Start Over Subject infrared photometry Subject variable stars Subject globular star clusters
1. BVIc light curves of 3 type II Cepheids
ID:
ivo://CDS.VizieR/J/AJ/139/2300
Title:
BVIc light curves of 3 type II Cepheids
Short Name:
J/AJ/139/2300
Date:
21 Oct 2021
Publisher:
CDS
Description:
Light curves in the B, V, and Ic passbands have been obtained for the type II Cepheids V154 in M3 and V42 and V84 in M5. Alternating cycle behavior, similar to that seen among RV Tauri variables, is confirmed for V84. Old and new observations, spanning more than a century, show that V154 has increased in period while V42 has decreased in period. V84, on the other hand, has shown large, erratic changes in period that do not appear to reflect the long-term evolution of V84 through the Hertzsprung-Russel diagram.
2. BVRI photometry in NGC4147
ID:
ivo://CDS.VizieR/J/PASP/117/1325
Title:
BVRI photometry in NGC4147
Short Name:
J/PASP/117/1325
Date:
21 Oct 2021
Publisher:
CDS
Description:
New BVRI broadband photometry and astrometry are presented for the globular cluster NGC 4147, based upon measurements derived from 524 ground-based CCD images mostly either donated by colleagues or retrieved from public archives. We have also reanalyzed five exposures of the cluster obtained with WFPC2 on the Hubble Space Telescope in the F439W and F555W (B and V) filters.
3. Cepheids in the young LMC cluster NGC 1866
ID:
ivo://CDS.VizieR/J/A+A/440/487
Title:
Cepheids in the young LMC cluster NGC 1866
Short Name:
J/A+A/440/487
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new near-IR light curves for six Cepheids in the young blue LMC cluster NGC 1866 as well as high precision radial velocity curves for ten Cepheids in NGC 1866 and two in NGC 2031. For the six Cepheids in NGC 1866 with new J and K light curves we determine distances and absolute magnitudes by applying the near-IR surface brightness method. We find that the formal error estimates on the derived distances are underestimated by about a factor of two. We find excellent agreement between the absolute magnitudes for the low metallicity LMC Cepheids with the Period-Luminosity (P-L) relation determined by the near-IR surface brightness (ISB) method for Galactic Cepheids suggesting that the slope of the P-L relations for low metallicity and solar metallicity samples could be very similar in contrast to other recent findings. Still there appears to be significant disagreement between the observed slopes of the OGLE based apparent P-L relations in the LMC and the slopes derived from ISB analysis of Galactic Cepheids, and by inference for Magellanic Cloud Cepheids, indicating a possible intrinsic problem with the ISB method itself. Resolving this problem could reaffirm the P-L relation as the prime distance indicator applicable as well to metallicities significantly different from the LMC value.
4. CTIO/DECam photometry of RR Lyrae stars in M5
ID:
ivo://CDS.VizieR/J/AJ/154/85
Title:
CTIO/DECam photometry of RR Lyrae stars in M5
Short Name:
J/AJ/154/85
Date:
21 Oct 2021
Publisher:
CDS
Description:
We characterize the absolute magnitudes and colors of RR Lyrae stars in the globular cluster M5 in the ugriz filter system of the Dark Energy Camera (DECam). We provide empirical period-luminosity (P-L) relationships in all five bands based on 47 RR Lyrae stars of the type ab and 14 stars of the type c. The P-L relationships were found to be better constrained for the fundamental-mode RR Lyrae stars in the riz passbands, with dispersions of 0.03, 0.02 and 0.02mag, respectively. The dispersion of the color at minimum light was found to be small, supporting the use of this parameter as a means to obtain accurate interstellar extinctions along the line of sight up to the distance of the RR Lyrae star. We found a trend of color at minimum light with a pulsational period that, if taken into account, brings the dispersion in color at minimum light to 0.016 mag for the (r-i), (i-z), and (r-z) colors. These calibrations will be very useful for using RR Lyrae stars from DECam observations as both standard candles for distance determinations and color standards for reddening measurements.
5. Globular cluster NGC 6397 variable stars
ID:
ivo://CDS.VizieR/J/other/NewA/88.J1607
Title:
Globular cluster NGC 6397 variable stars
Short Name:
J/other/NewA/88.
Date:
22 Feb 2022
Publisher:
CDS
Description:
We present a new time-series VI CCD photometry of the globular cluster NGC 6397, from which we obtained and analysed the light curves of 35 variables carefully identified in the cluster field. We assessed the membership of the variables with an astrometric analysis based on Gaia DR2 data. The cluster colour-magnitude diagram was differentially de- reddened and cleaned of non members, which allowed us to fit isochrones for [Fe/H]=-2.0dex in the range 13.0-13.5Gyr, for a mean reddening E(B-V)=0.19, and a distance of 2.5kpc. This distance was confirmed using the period-luminosity relation for the cluster's five SX Phoenicis variables (V10, V11, V15, V21, and V23) present among its blue stragglers, yielding 2.24+/-0.13kpc. We also modelled the light curves of four eclipsing binaries (V4, V5, V7, and V8), and gave the parameters of the systems; the contact binaries V7 and V8 have distances consistent with that of the cluster. NGC 6397 appears to harbour no RR Lyrae stars, being its horizontal branch remarkably blue, much like that of its analogous cluster, M10. To match the blue tail of the horizontal branch population, models of 0.64-0.66M_{sun}_ with mass loss at the RGB are required, indicating rather thin shell masses for horizontal branch stars.
6. JHK photometry of M92 variable stars
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.
7. 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.
8. LMC NIR survey. IV. Type II Cepheid variables
ID:
ivo://CDS.VizieR/J/AJ/153/154
Title:
LMC NIR survey. IV. Type II Cepheid variables
Short Name:
J/AJ/153/154
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present time-series observations of Population II Cepheids in the Large Magellanic Cloud at near-infrared (JHK_s_) wavelengths. Our sample consists of 81 variables with accurate periods and optical (VI) magnitudes from the OGLE survey, covering various subtypes of pulsators (BL Herculis, W Virginis, and RV Tauri). We generate light-curve templates using high-quality I-band data in the LMC from OGLE and K_s_-band data in the Galactic bulge from VISTA Variables in Via Lactea survey (2010NewA...15..433M) and use them to obtain robust mean magnitudes. We derive period-luminosity (P-L) relations in the near-infrared and Period-Wesenheit (P-W) relations by combining optical and near-infrared data. Our P-L and P-W relations are consistent with published work when excluding long-period RV Tauris. We find that Pop II Cepheids and RR Lyraes follow the same P-L relations in the LMC. Therefore, we use trigonometric parallax from the Gaia DR1 (Cat. I/337) for VY Pyx and the Hubble Space Telescope parallaxes for k Pav and 5 RR Lyrae variables to obtain an absolute calibration of the Galactic K_s_-band P-L relation, resulting in a distance modulus to the LMC of {mu}_LMC_=18.54+/-0.08 mag. We update the mean magnitudes of Pop II Cepheids in Galactic globular clusters using our light-curve templates and obtain distance estimates to those systems, anchored to a precise late-type eclipsing binary distance to the LMC. We find that the distances to these globular clusters based on Pop II Cepheids are consistent (within 2{sigma}) with estimates based on the M_V_-[Fe/H] relation for horizontal branch stars.
9. NGC 5024 (M53) RR Lyrae VI light curves
ID:
ivo://CDS.VizieR/J/MNRAS/420/1333
Title:
NGC 5024 (M53) RR Lyrae VI light curves
Short Name:
J/MNRAS/420/1333
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the discovery of amplitude and phase modulations typical of the Blazhko effect in 22 RRc and nine RRab type RR Lyrae stars in NGC 5024 (M53). This brings the confirmed Blazhko variables in this cluster to 23 RRc and 11 RRab stars, which represent 66 and 37 per cent of the total population of RRc and RRab stars in the cluster, respectively, making NGC 5024 the globular cluster with the largest presently known population of Blazhko RRc stars. We place a lower limit of 52 per cent on the overall incidence rate of the Blazhko effect among the RR Lyrae population in this cluster. New data have allowed us to refine the pulsation periods. The limitations imposed by the time span and sampling of our data prevent reliable estimations of the modulation periods. The amplitudes of the modulations range between 0.02 and 0.39mag. The RRab and RRc are neatly separated in the colour-magnitude diagram, and the RRc Blazhko variables are on average redder than their stable counterparts; these two facts may support the hypothesis that the horizontal branch (HB) evolution in this cluster is towards the red and that the Blazhko modulations in the RRc stars are connected with the pulsation mode switch.
10. NGC 2419 variable star population
ID:
ivo://CDS.VizieR/J/AJ/141/81
Title:
NGC 2419 variable star population
Short Name:
J/AJ/141/81
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present B, V, and I CCD light curves for 101 variable stars belonging to the globular cluster NGC 2419, 60 of which are new discoveries, based on data sets obtained at the Telescopio Nazionale Galileo, the Subaru telescope, and the Hubble Space Telescope. The sample includes 75 RR Lyrae stars (38 RRab, 36 RRc, and one RRd), one Population II Cepheid, 12 SX Phoenicis variables, two delta Scuti stars, three binary systems, five long-period variables, and three variables of uncertain classification.

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