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1641. VRIH{alpha} photometry of NGC 2264 variables
ID:
ivo://CDS.VizieR/J/A+A/430/1005
Title:
VRIH{alpha} photometry of NGC 2264 variables
Short Name:
J/A+A/430/1005
Date:
21 Oct 2021
Publisher:
CDS
Description:
Table 1 lists 405 periodic variable stars we found in the area of NGC 2264 between. It contains information of the position, brightness, colours, and period of these stars. It also lists the spectral type taken from the literature (if available) as well as the alternative identification numbers of the stars which we used in the analysis process. The results presented here are based on a photometric monitoring program of a 34'x34' field in NGC 2264 carried out with the Wide-Field-Imager (WFI) attached to the ESO/MPG 2.2m telescope on La Silla, Chile. Observations were obtained on 44 nights in the I_C_ band during a period of two months between Dec. 2000 and March 2001. We also obtained several additional images through V, R_C_ and H{alpha} filters.
1642. VRIJHK LCs of the binary T Tauri star V582 Mon
ID:
ivo://CDS.VizieR/J/AJ/159/135
Title:
VRIJHK LCs of the binary T Tauri star V582 Mon
Short Name:
J/AJ/159/135
Date:
21 Oct 2021
Publisher:
CDS
Description:
The binary T Tauri star V582Mon (KH15D) is surrounded by a tilted and nodally precessing ring of dusty material, which has caused periodic occultations of one or both stars over the last 50 years. Here, we present multi-color time-series photometry (VRIJHK) throughout the 2017/2018 observing season, when the ring was covering the entire orbit of star A and gradually exposing the orbit of star B. We calculate the mean apparent magnitude of star B to be I=14.08. Besides the periodic eclipses of star B due to its orbital motion, we observed unexpected dips in brightness indicative of partially transparent stellar-sized clumps within the ring. The wavelength dependence of these events is suggestive of extinction by dust grains significantly larger than typical interstellar dust grains. The photometric variability observed while star B is being uncovered by the trailing edge of the ring is not simply the time reversal of the behavior seen when star A was being covered by the leading edge. Whereas the leading edge appeared to be very sharply defined, the trailing edge is "clumpy" and "fuzzy" (transparent), with a more gradual transition in opacity. The clumpiness and transparency of the occulting material provide a unique opportunity to study the properties of dust grains in a likely planet-forming zone.
1643. VRIJHK photometry of the T Tauri binary KH 15D
ID:
ivo://CDS.VizieR/J/AJ/155/47
Title:
VRIJHK photometry of the T Tauri binary KH 15D
Short Name:
J/AJ/155/47
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present VRIJHK photometry of the KH 15D T Tauri binary system for the 2015/2016 and 2016/2017 observing seasons. For the first time in the modern (CCD) era, we are seeing Star B fully emerge from behind the trailing edge of the precessing circumbinary ring during each apastron passage. We are, therefore, able to measure its luminosity and color. Decades of photometry on the system now allow us to infer the effective temperature, radius, mass, and age of each binary component. We find our values to be in good agreement with previous studies, including archival photographic photometry from the era when both stars were fully visible, and they set the stage for a full model of the system that can be constructed once radial velocity measurements are available. We also present the first high-sensitivity radio observations of the system, taken with the Atacama Large Millimeter/submillimeter Array and the Submillimeter Array. The respective 2.0 and 0.88 mm observations provide an upper limit on the circumbinary (gas and dust) disk mass of 1.7 M_Jup_ and reveal an extended CO outflow, which overlaps with the position, systemic velocity, and orientation of the KH 15D system and is certainly associated with it. The low velocity, tight collimation, and extended nature of the emission suggest that the outflow is inclined nearly orthogonal to the line of sight, implying it is also orthogonal to the circumbinary ring. The position angle of the radio outflow also agrees precisely with the direction of polarization of the optical emission during the faint phase. A small offset between the optical image of the binary and the central line of the CO outflow remains a puzzle and possible clue to the jet launching mechanism.
1644. VrI light curves of NGC6981 variables
ID:
ivo://CDS.VizieR/J/MNRAS/413/1275
Title:
VrI light curves of NGC6981 variables
Short Name:
J/MNRAS/413/1275
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results from 10 nights of observations of the globular cluster NGC 6981 (M72) in the V, R and I Johnson wavebands. We employed the technique of difference image analysis to perform precision differential photometry on the time-series images, which enabled us to carry out a census of the understudied variable star population of the cluster. We show that 20 suspected variables in the literature are actually non-variable, and we confirm the variable nature of another 29 variables while refining their ephemerides. We also detect 11 new RR Lyrae variables and three new SX Phe variables, bringing the total confirmed variable star count in NGC 6981 to 43. We performed Fourier decomposition of the light curves for a subset of RR Lyrae stars and used the Fourier parameters to estimate the fundamental physical parameters of the stars using relations available in the literature. Mean values of these physical parameters have allowed us to estimate the physical parameters of the parent cluster. We derive a metallicity of [Fe/H]_ZW_~-1.48+/-0.03 on the Zinn & West scale (or [Fe/H]_UVES_~-1.38+/-0.03 on the new Carretta et al. scale) for NGC 6981, and distances of ~16.73+/-0.36 and ~16.68+/-0.36kpc from analysis of the RR0 and RR1 stars separately. We also confirm the Oosterhoff type I classification for the cluster, and show that our colour-magnitude data are consistent with the age of ~12.75+/-0.75Gyr derived by Dotter et al.
1645. VrI light curves of NGC7099 variables
ID:
ivo://CDS.VizieR/J/A+A/555/A36
Title:
VrI light curves of NGC7099 variables
Short Name:
J/A+A/555/A36
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the analysis of 26 nights of V and I time-series observations from 2011 and 2012 of the globular cluster M 30 (NGC 7099). We used our data to search for variable stars in this cluster and refine the periods of known variables; we then used our variable star light curves to derive values for the cluster's parameters. We used difference image analysis to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate was possible. We also derive an estimate for the age of the cluster by fitting theoretical isochrones to our colour-magnitude diagram (CMD). Out of 13 stars previously catalogued as variables, we find that only 4 are bona fide variables. We detect two new RR Lyrae variables, and confirm two additional RR Lyrae candidates from the literature. We also detect four other new variables, including an eclipsing blue straggler system, and an SX Phoenicis star. This amounts to a total number of confirmed variable stars in M 30 of 12. We perform Fourier decomposition of the light curves of the RR Lyrae stars to derive cluster parameters using empirical relations. We find a cluster metallicity [Fe/H]_ZW_=-2.01+/-0.04, or [Fe/H]_UVES_=-2.11+/-0.06, and a distance of 8.32+/-0.20kpc (using RR0 variables), 8.10 kpc (using one RR1 variable), and 8.35+/-0.42kpc (using our SX Phoenicis star detection in M 30). Fitting isochrones to the CMD, we estimate an age of 13.0+/-1.0Gyr for M 30.
1646. VrI light curves of NGC1904 variables
ID:
ivo://CDS.VizieR/J/A+A/548/A92
Title:
VrI light curves of NGC1904 variables
Short Name:
J/A+A/548/A92
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the analysis of 11 nights of V and I time-series observations of the globular cluster NGC 1904 (M 79). Using this we searched for variable stars in this cluster and attempted to refine the periods of known variables, making use of a time baseline spanning almost 8 years. We use our data to derive the metallicity and distance of NGC 1904. We used difference imaging to reduce our data to obtain high-precision light curves of variable stars. We then estimated the cluster parameters by performing a Fourier decomposition of the light curves of RR Lyrae stars for which a good period estimate was possible. We also derive an estimate for the age of the cluster by fitting theoretical isochrones to our colour-magnitude diagram (CMD). Out of 13 stars previously classified as variables, we confirm that 10 are bona fide variables. We cannot detect variability in one other within the precision of our data, while there are two which are saturated in our data frames, but we do not find sufficient evidence in the literature to confirm their variability. We also detect a new RR Lyrae variable, giving a total number of confirmed variable stars in NGC 1904 of 11. Using the Fourier parameters, we find a cluster metallicity [Fe/H]_ZW_=-1.63+/-0.14, or [Fe/H]_UVES_=-1.57+/-0.18, and a distance of 13.3+/-0.4kpc (using RR0 variables) or 12.9kpc (using the one RR1 variable in our sample for which Fourier decomposition was possible).
1647. VRI photometry of IC5070 variable stars
ID:
ivo://CDS.VizieR/J/A+A/627/A135
Title:
VRI photometry of IC5070 variable stars
Short Name:
J/A+A/627/A135
Date:
21 Oct 2021
Publisher:
CDS
Description:
We observed a field of 16'x16' in the star-forming region Pelican Nebula (IC 5070) at BVRI wavelengths for 90 nights spread over one year in 2012-2013. More than 250 epochs in VRI-bands are used to identify and classify variables up to V~21mag. We present a catalogue of optical time-series photometry with periods, mean-magnitudes and classifications for 95 variable stars including 67 pre-main-sequence variables towards star-forming region IC 5070. The pre-main-sequence variables are further classified as candidate classical T Tauri and weak-line T Tauri stars based on their light curve variations and the locations on the color-color and color-magnitude diagrams using optical and infrared data together with Gaia DR2 astrometry. Classical T Tauri stars display variability amplitudes up to three times the maximum fluctuation in disk-free weak-line T Tauri stars, which show strong periodic variations. Short-term variability is missed in our photometry within single nights. Several classical T Tauri stars display long-lasting (>10 days) single or multiple fading and brightening events up to a couple of magnitudes at optical wavelengths.
1648. VR light curve of ASAS-North Cepheids
ID:
ivo://CDS.VizieR/J/AJ/137/4598
Title:
VR light curve of ASAS-North Cepheids
Short Name:
J/AJ/137/4598
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained VR photometry of 282 Cepheid variable star candidates from the northern part of the All Sky Automated Survey (ASAS). These together with data from the ASAS and the Northern Sky Variability Survey (NSVS) were used to redetermine the periods of the stars.
1649. VR light curves of AA Tau in 2007-2013
ID:
ivo://CDS.VizieR/J/A+A/557/A77
Title:
VR light curves of AA Tau in 2007-2013
Short Name:
J/A+A/557/A77
Date:
21 Oct 2021
Publisher:
CDS
Description:
AA Tau has been monitored for more than 20 years since 1987, exhibiting a nearly constant brightness level of V=12.5mag. We report here that in 2011 it suddenly faded away, becoming 2 magnitudes fainter in the V-band, and has remained in this deep state since then. We investigate the origin of the sudden dimming of the AA Tau system. We report new optical and near-IR photometry and spectroscopy obtained during the fading event.
1650. VR light curves of M2 variables
ID:
ivo://CDS.VizieR/J/MNRAS/372/69
Title:
VR light curves of M2 variables
Short Name:
J/MNRAS/372/69
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the results of CCD V and R photometry of the RR Lyrae stars in M2. The periodicities of most variables are revised and new ephemerides are calculated. Light-curve decomposition of the RR Lyrae stars was carried out and the corresponding mean physical parameters [Fe/H]=-1.47, Teff=6276K, logL=1.63L_{sun}_ and M_V_=0.71 from nine RRab and [Fe/H]=-1.61, M=0.54M_{sun}_, Teff=7215K, logL=1.74L_{sun}_ and M_V_=0.71 from two RRc stars were calculated. A comparison of the radii obtained from the above luminosity and temperature with predicted radii from non-linear convective models is discussed. The estimated mean distance to the cluster is 10.49+/-0.15kpc. These results place M2 correctly in the general globular cluster sequences for Oosterhoff type, mass, luminosity and temperature, all as a function of the metallicity. Mean relationships for M, logL/L_{sun}_, Teff and MV as a function of [Fe/H] for a family of globular clusters are offered. These trends are consistent with evolutionary and structural notions on the horizontal branch. Eight new variables are reported.