- 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.
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Search Results
- 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.
- 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).
- ID:
- ivo://CDS.VizieR/J/A+A/528/A42
- Title:
- VRi light curves of the lensed QSO HE 0435-1223
- Short Name:
- J/A+A/528/A42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present VRi photometric observations of the quadruply imaged quasar HE0435-1223, carried out with the Danish 1.54m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as a function of time.
21145. VRI light curves of TT Her
- ID:
- ivo://CDS.VizieR/J/ApJ/783/35
- Title:
- VRI light curves of TT Her
- Short Name:
- J/ApJ/783/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new radial velocities and photometry of the short-period Algol TT Herculis. Previous attempts to model the light curves of the system have met with limited success, primarily because of the lack of a reliable mass ratio. Our spectroscopic observations are the first to result in radial velocities for the secondary star, and thus provide a spectroscopic mass ratio. Simultaneous analysis of the radial velocities and new photometry shows that the system is a double contact binary, with a rapidly rotating primary that fills its limiting lobe.
- ID:
- ivo://CDS.VizieR/J/ApJS/229/21
- Title:
- VRI monitoring of the QSO 3C 273 in 2005-2016
- Short Name:
- J/ApJS/229/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have monitored the quasar 3C 273 in the optical V, R, and I bands from 2005 to 2016. Intraday variability (IDV) is detected on seven nights. The variability amplitudes on most of the nights are less than 10%, and on four nights, more than 20%. When considering the nights with time spans >4hr, the duty cycle (DC) is 14.17%. Over the 12yrs, the overall magnitude and color index variabilities are {Delta}I=0.67, {Delta}R=0.72, {Delta}V=0.68, and {Delta}(V-R)=0.25, respectively. The largest clear IDV has an amplitude of 42% over just 5.8 minutes, and the weakest detected IDV is 5.4% over 175 minutes. The BWB (bluer when brighter) chromatic trend is dominant for 3C 273 and appears at different flux levels on intraday timescales. The BWB trend exists for short-term timescales and intermediate-term timescales but different timescales have different correlations. There is no BWB trend for our whole time-series data sets. A significant anticorrelation between the BWB trend and length of timescales is found. Combining with V-band data from previous works, we find a possible quasi-periodicity of P=3918+/-1112 days. The possible explanations for the observed variability, BWB chromatic trend, and periodicity are discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/128/846
- Title:
- VRI observations of CE Leonis
- Short Name:
- J/AJ/128/846
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present complete VRI light curves of the contact binary CE Leo and provide detailed photometric solutions, as well as an analysis of its period variation. A total of 73 times of minima over 50years, including our observations, were used for the period study.
- ID:
- ivo://CDS.VizieR/J/AZh/84/885
- Title:
- VRI observations of radio source S5 0716+71
- Short Name:
- J/AZh/84/885
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of VRI photometry of the gravitationally lensed system Q2237+0305 carried out on the 1.5-m telescope of Maidanak observatory in 2004-2005 are presented. The distance between the components is of the order of 1".
- ID:
- ivo://CDS.VizieR/J/ApJ/669/525
- Title:
- VRI photometric standards for NGC 6946
- Short Name:
- J/ApJ/669/525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new, very late time optical photometry and spectroscopy of the interesting Type II-P supernova SN 2002hh, in NGC 6946. Gemini/GMOS-N has been used to acquire visible spectra at six epochs between 2004 August and 2006 July, following the evolution of the SN from age 661 to 1358-days. Few optical spectra of Type II supernovae with ages greater than 1yr exist. In addition, g', r', and i' images were acquired at all six epochs. The spectral and photometric evolution of SN 2002hh has been very unusual. Measures of the brightness of this SN, both in the R and I bands, as well as in the Halpha emission flux, show no significant fading over an interval of nearly 2-years.
- ID:
- ivo://CDS.VizieR/J/ApJS/176/262
- Title:
- VRI photometry and theta values in open clusters
- Short Name:
- J/ApJS/176/262
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, new Cousins VRI data are presented for NGC 752 and Praesepe, and new and extant data are combined into an augmented database for M67. For those three clusters, catalogs containing Cousins VRI photometry, reddening-corrected values of (V-K)J, and temperatures are produced. The same is done for Coma by using both previously published and newly derived Cousins photometry. An extant set of catalogs for the Hyades is updated to include V magnitudes and values of (R-I)C that were published after the original catalogs appeared. Finally, M67 V magnitudes published previously by Sandquist are corrected for an effect that depends on location on the face of the cluster. The corrected data and values of (V-I)C given by Sandquist are then set out in a supplementary catalog.
