- ID:
- ivo://CDS.VizieR/J/AcA/66/307
- Title:
- NGC 362 variable V light curves
- Short Name:
- J/AcA/66/307
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The field of the globular cluster NGC 362 was monitored between 1997 and 2015 in a search for variable stars. BV light curves were obtained for 151 periodic or likely periodic variable stars, over a hundred of which are new detections. Twelve newly detected variable stars are proper-motion members of the cluster: two SX Phe and two RR Lyr pulsators, one contact binary, three detached or semi-detached eclipsing binaries, and four spotted variable stars. The most interesting objects among these are the binary blue straggler V20 with an asymmetric light curve, and the 8.1d semidetached binary V24 located on the red giant branch of NGC 362, which is a Chandra X-ray source. We also provide substantial new data for 24 previously known variable stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/117/1313
- Title:
- NGC 6441 VI photometry
- Short Name:
- J/AJ/117/1313
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present time-series VI photometry of the metal-rich ([Fe/H]=-0.53) globular cluster NGC 6441. Our color-magnitude diagram shows that the extended blue horizontal branch seen in Hubble Space Telescope data exists in the outermost reaches of the cluster.
- ID:
- ivo://CDS.VizieR/J/PASP/120/1183
- Title:
- NIR fluxes of 14 cool variable stars
- Short Name:
- J/PASP/120/1183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New flux data are presented for nine non-variable stars and 14 evolved variable stars with spectral types M and C. The data are from measurements of 21 passbands in the wavelength range from 7440{AA} to 10834{AA}, and they are comparable to measurements made by Wing some 40 years ago. Because the extinction algorithm applied to the new data is based partly on up-to-date calculations of telluric water-vapor effects, those calculations are tested for accuracy. In addition, methods used to calibrate standard stars both outside and inside the Paschen confluence are explained. After reddening corrections are applied to the flux data for the variable stars, those data are used to calculate color temperatures. In turn, those temperatures are used to derive blanketing corrections to color temperatures measured in the Wing filter system. Indices of absorption strength are calculated by comparing the flux data to blackbody colors derived from the color temperatures. It is found that the standard errors of those temperatures range from 3% to less than 1%. For the variable stars, the standard errors for the flux data range from 6.8mmag to 11.6mmag. For the non-variable stars, the corresponding standard error is about 6.0mmag.
- ID:
- ivo://CDS.VizieR/J/ApJ/898/46
- Title:
- NIR LCs of RRab stars from the VVV survey
- Short Name:
- J/ApJ/898/46
- Date:
- 21 Mar 2022 07:11:54
- Publisher:
- CDS
- Description:
- Aiming to extend the census of RR Lyrae stars to highly reddened low-latitude regions of the central Milky Way, we performed a deep near-IR variability search using data from the VISTA Variables in the Via Lactea (VVV) survey of the bulge, analyzing the photometric time series of over a hundred million point sources. In order to separate fundamental-mode RR Lyrae (RRab) stars from other periodically variable sources, we trained a deep bidirectional long short-term memory recurrent neural network (RNN) classifier using VVV survey data and catalogs of RRab stars discovered and classified by optical surveys. Our classifier attained a ~99% precision and recall for light curves with signal-to-noise ratio above 60, and is comparable to the best-performing classifiers trained on accurate optical data. Using our RNN classifier, we identified over 4300 hitherto unknown bona fide RRab stars toward the inner bulge. We provide their photometric catalog and VVV J,H,Ks photometric time series.
- ID:
- ivo://CDS.VizieR/J/AJ/160/220
- Title:
- NIR light curve of 234 RR Lyrae in Messier 3
- Short Name:
- J/AJ/160/220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new near-infrared (NIR), JHKs, time-series observations of RR-Lyrae variables in the Messier-3 (NGC5272) globular cluster using the WIRCam instrument at the 3.6m Canada-France-Hawaii Telescope. Our observations cover a sky area of ~21'x21' around the cluster center and provide an average of 20 epochs of homogeneous JHKs-band photometry. New homogeneous photometry is used to estimate robust mean magnitudes for 175 fundamental-mode (RRab), 47 overtone-mode (RRc), and 11 mixed-mode (RRd) variables. Our sample of 233 RR-Lyrae variables is the largest thus far obtained in a single cluster with time-resolved, multiband NIR photometry. NIR-to-optical amplitude ratios for RR-Lyrae in Messier-3 exhibit a systematic increase moving from RRc to short-period (P<0.6day) and long-period (P>~0.6day) RRab variables. We derive JHKs-band period-luminosity relations for RRab, RRc, and the combined sample of variables. Absolute calibrations based on the theoretically predicted period-luminosity-metallicity relations for RR Lyrae stars yield a distance modulus, {mu}=15.041{+/-}0.017(statistical){+/-}0.036(systematic)mag, to Messier-3. When anchored to trigonometric parallaxes for nearby RR-Lyrae stars from the Hubble Space Telescope and the Gaia mission, our distance estimates are consistent with those resulting from the theoretical calibrations, albeit with relatively larger systematic uncertainties.
- ID:
- ivo://CDS.VizieR/J/A+A/576/A30
- Title:
- NIR light-curve templates for classical Cepheids
- Short Name:
- J/A+A/576/A30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new near-infrared (NIR) light-curve templates for fundamental (FU, J, H, Ks) and first overtone (FO, J) classical Cepheids. The new templates together with period-luminosity and period-Wesenheit (PW) relations provide Cepheid distances from single-epoch observations with a precision only limited by the intrinsic accuracy of the method adopted. The templates rely on a very large set of Galactic and Magellanic Cloud Cepheids (FU, ~600; FO, ~200) with well-sampled NIR (IRSF data set) and optical (V, I; OGLE data set) light-curves. To properly trace the change in the shape of the light-curve as a function of pulsation period, we split the sample of calibrating Cepheids into ten different period bins. The templates for the first time cover FO Cepheids and the short-period range of FU Cepheids (P<=5-days). Moreover, the phase zero-point is anchored to the phase of the mean magnitude along the rising branch. The new approach has several advantages in sampling the light-curve of bump Cepheids when compared with the canonical phase of maximum light. We also provide new empirical estimates of the NIR-to-optical amplitude ratios for FU and FO Cepheids. We perform detailed analytical fits using seventh-order Fourier series and multi-Gaussian periodic functions. The latter are characterized by fewer free parameters (nine vs. fifteen). The mean NIR magnitudes based on the new templates are up to 80% more accurate than single-epoch NIR measurements and up to 50% more accurate than the mean magnitudes based on previous NIR templates, with typical associated uncertainties ranging from 0.015mag (J band) to 0.019mag (K_S_ band). Moreover, we find that errors on individual distance estimates for Small Magellanic Cloud Cepheids derived from NIR PW relations are essentially reduced to the intrinsic scatter of the adopted relations. Thus, the new templates are the ultimate tool for estimating precise Cepheid distances from NIR single-epoch observations, which can be safely adopted for future interesting applications, including deriving the 3D structure of the Magellanic Clouds.
- ID:
- ivo://CDS.VizieR/J/AJ/154/263
- Title:
- NIR photometry of 77 RR Lyrae stars
- Short Name:
- J/AJ/154/263
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained single-phase near-infrared (NIR) magnitudes in the J and K bands for 77 RR Lyrae (RRL) stars in the Fornax Dwarf Spheroidal Galaxy. We have used different theoretical and empirical NIR period-luminosity-metallicity calibrations for RRL stars to derive their absolute magnitudes, and found a true, reddening-corrected distance modulus of 20.818+/-0.015(statistical)+/-0.116(systematic) mag. This value is in excellent agreement with the results obtained within the Araucaria Project from the NIR photometry of red clump stars (20.858+/-0.013 mag), the tip of the red giant branch (20.84+/-0.04+/-0.14 mag), as well as with other independent distance determinations to this galaxy. The effect of metallicity and reddening is substantially reduced in the NIR domain, making this method a robust tool for accurate distance determination at the 5% level. This precision is expected to reach the level of 3% once the zero points of distance calibrations are refined thanks to the Gaia mission. NIR period-luminosity-metallicity relations of RRL stars are particularly useful for distance determinations to galaxies and globular clusters up to 300 kpc, that lack young standard candles, like Cepheids.
- ID:
- ivo://CDS.VizieR/J/ApJS/211/3
- Title:
- NIR photometry variability in {rho} Oph
- Short Name:
- J/ApJS/211/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Presented are the results of a near-IR photometric survey of 1678 stars in the direction of the {rho} Ophiuchus ({rho} Oph) star forming region using data from the 2MASS Calibration Database. For each target in this sample, up to 1584 individual J-, H-, and Ks-band photometric measurements with a cadence of ~1 day are obtained over three observing seasons spanning ~2.5 yr; it is the most intensive survey of stars in this region to date. This survey identifies 101 variable stars with {Delta}Ks-band amplitudes from 0.044 to 2.31 mag and {Delta}(J-Ks) color amplitudes ranging from 0.053 to 1.47 mag. Of the 72 young {rho} Oph star cluster members included in this survey, 79% are variable; in addition, 22 variable stars are identified as candidate members. Based on the temporal behavior of the Ks time-series, the variability is distinguished as either periodic, long time-scale or irregular. This temporal behavior coupled with the behavior of stellar colors is used to assign a dominant variability mechanism. A new period-searching algorithm finds periodic signals in 32 variable stars with periods between 0.49 to 92 days. The chief mechanism driving the periodic variability for 18 stars is rotational modulation of cool starspots while 3 periodically vary due to accretion-induced hot spots. The time-series for six variable stars contains discrete periodic "eclipse-like" features with periods ranging from 3 to 8 days. These features may be asymmetries in the circumstellar disk, potentially sustained or driven by a proto-planet at or near the co-rotation radius. Aperiodic, long time-scale variations in stellar flux are identified in the time-series for 31 variable stars with time-scales ranging from 64 to 790 days. The chief mechanism driving long time-scale variability is variable extinction or mass accretion rates. The majority of the variable stars (40) exhibit sporadic, aperiodic variability over no discernable time-scale. No chief variability mechanism could be identified for these variable stars.
- ID:
- ivo://CDS.VizieR/II/287
- Title:
- Northern Sky Variability Survey (NSVS)
- Short Name:
- II/287
- Date:
- 23 Nov 2021 00:31:33
- Publisher:
- CDS
- Description:
- The Northern Sky Variability Survey (NSVS) is a temporal record of the sky over the optical magnitude range from 8 to 15.5. It was conducted in the course of the first-generation Robotic Optical Transient Search Experiment (ROTSE-I) using a robotic system of four comounted unfiltered telephoto lenses equipped with CCD cameras. The survey was conducted from Los Alamos, New Mexico, and primarily covers the entire northern sky. Some data in southern fields between declinations 0{deg} and -38{deg} are also available, although with fewer epochs and noticeably lesser quality. The NSVS contains light curves for approximately 14 million objects. With a 1-yr baseline and typically 100-500 measurements per object, the NSVS is the most extensive record of stellar variability across the bright sky available today. In a median field, bright unsaturated stars attain a point-to-point photometric scatter of ~0.02mag and position errors within 2. At Galactic latitudes |b|<20{deg}, the data quality is limited by severe blending due to the ~14" pixel size. We present basic characteristics of the data set and describe data collection, analysis, and distribution. All NSVS photometric measurements are available for on-line public access from the Sky Database for Objects in Time-Domain (SkyDOT) at Los Alamos National Laboratory. Copies of the full survey photometry may also be requested on tape.
- ID:
- ivo://CDS.VizieR/J/AJ/114/1190
- Title:
- NSV 09295: A double-mode RR Lyrae
- Short Name:
- J/AJ/114/1190
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An analysis of more than 2000 CCD observations of the field RR Lyrae star NSV 09295 shows that the star is a double-mode RR Lyrae (RRd) variable with P_0_=0.46334d and P_1_=0.34423d. This brings the total of known field RRd stars in the Milky Way galaxy to four. These four variables are compared with the RRd stars in galactic globular clusters and with the field RRd stars in the LMC, and in the Draco and Sculptor dwarf galaxies. It appears that all known RRd stars have a metal abundance of less than [Fe/H]=-1.6. (c) 1997 American Astronomical Society.
