- ID:
- ivo://CDS.VizieR/J/AJ/98/2086
- Title:
- CCD photometry of NGC 2257 RR Lyrae
- Short Name:
- J/AJ/98/2086
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- B and V band CCD photometry is used to study 33 cluster and nine field RR Lyrae variables near the LMC cluster, NGC 2257. It is found that the mean magnitudes for the two groups differ by 0.17 mag. The cluster and field variables both have an Fe/H abundance ratio of -1.8+/-0.1. The results are compared used to compare NGC 2257 with galactic globular clusters, showing that NGC 2257 is indistinguishable from its local counterparts.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/112/618
- Title:
- CCD photometry of variable stars in M9
- Short Name:
- J/AJ/112/618
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD observations have been used to derive precise light curves for six of the previously known RR Lyrae variables in the Oosterhoff type II globular cluster M9 and to search for additional variables. Nine variables have been discovered, eight of the RR Lyrae type. As a result, the total number of RR Lyrae variables has been revised from 9 to 17 (9 RRc and 8 RRab), the mean period of the RRc stars has been revised from 0.341d to 0.342d and that of the RRab stars from 0.621d to 0.638d. Simon's method that relates physical properties of RRc stars to the pulsation period and Fourier phase parameter {phi}_31_ has been used to determine the mass, luminosity, and temperature for one of the RRc stars. Published observations of RR Lyrae stars in M15 have been used to test Simon's method (1993ApJ...410..526S, 1993, IAUCo, 139, 315) and the results are promising. The formulae of Jurcsik and Kovacs (1996A&A...312..111J) for relating Fourier parameters of RRab stars to [Fe/H] have been used to derive a metal abundance for M9.
- ID:
- ivo://CDS.VizieR/J/A+AS/129/337
- Title:
- CCD photometry of YY Orionis stars
- Short Name:
- J/A+AS/129/337
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of photometric monitoring in the UBVRI bands of 5 YY Orionis stars and 2 other variable stars are presented. Each source was observed in the period of 1996, Nov. 23 to Dec. 2 and of 1996, Dec. 23 to 1997,Jan. 2 at the 1-m telescope of Wise Observatory, Israel. Tables.dat contain the luminosity variation of each star as deviation from its average observed magnitude.
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/42.75
- Title:
- CCD RV light curve of M15 RR Lyrae
- Short Name:
- J/other/RMxAA/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Results of CCD photometry using V and R filters are reported for 33 RR Lyrae stars in M15. Applying the approach of Fourier decomposition of the light curves, the physical parameters of the type RRab and RRc variables were estimated. The cluster is Oosterhoff type II and the values for the iron content and distance are: [Fe/H]=-1.98+/-0.24 and d=8.67+/-0.41kpc, respectively. The mean values of the physical parameters determined for the RR Lyrae stars place the cluster precisely into the sequences Oosterhoff type - metallicity and metallicity - effective temperature, valid for globular clusters. Evidences of evolution from the ZAHB are found for the RRc but not for the RRab stars.
- ID:
- ivo://CDS.VizieR/II/162
- Title:
- CCD search for Cepheids in Crux and Centaurus
- Short Name:
- II/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains the results of a photometric survey for variable stars in a 9.4 square degree region along the galactic plane in Crux and Centaurus. A total of 300308 stars were observed at seven epochs over 42 days; 224 524 of these stars were detected at multiple epochs and were tested for possible variations in brightness that exceed observational error. 2422 stars are identified as variable at a formal confidence level of 99%; 270 of the new variables brighter than I=14.0 are classified as long period variables. A list of 242 likely short period variables with RMS amplitudes >=0.060mag is given. From this list, 37 Cepheid candidates were selected after inspection of their light curves.
- ID:
- ivo://CDS.VizieR/J/AJ/162/52
- Title:
- Census of variable stars toward Serpens Main
- Short Name:
- J/AJ/162/52
- Date:
- 14 Mar 2022 06:55:43
- Publisher:
- CDS
- Description:
- We monitored a 3deg^2^ area toward Serpens Main in the Pan-STARRS1 r, i, and z bands from 2016 April to September. Light curves of more than 11000 stars in each band were obtained, and 143 variables have been identified. Among those, 119 variables are new discoveries, while 24 variables were previously known. We present variability classes and periods of 99 stars. Of these, 81 are located in the upper giant branch, displaying long periods, while the remaining 18 variables are pre-main-sequence objects with short periods. We also identify eight eclipsing binary systems, including the known binary V0623Ser, and derive their physical parameters. According to a clustering analysis of Gaia DR2 stars in the observed field, there are 10 variable members in Serpens Main, where six members have been classified as young stellar objects in previous studies. Here we provide color-magnitude and color-color diagrams for these variables. The color variability of most variables in the color-magnitude diagrams produces the expected displacements, while the movements of cluster members point in different directions; this behavior may be associated with accretion spots or circumstellar disks.
- ID:
- ivo://CDS.VizieR/J/AJ/156/171
- Title:
- Cepheid abund.: multiphase results & spatial gradients
- Short Name:
- J/AJ/156/171
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Parameters and abundances have been derived for 435 Cepheids based on an analysis of 1127 spectra. Results from five or more phases are available for 52 of the program stars. The latter set of stars span periods between 1.5 and 68 days. The parameters and abundances show excellent consistency across phase. For iron, the average range in the determined abundance is 0.11 from these 52 stars. For 163 stars with more than one phase available the average range is 0.07. The variation in effective temperature tracks well with phase, as does the total broadening velocity. The gravity and microturbulent velocity follow phase, but with less variation and regularity. Abundance gradients have been derived using Gaia DR2 (Cat. I/345) parallax data, as well as Bayesian distance estimates based upon Gaia DR2 from Bailer-Jones et al. (2018, Cat. I/347). The abundance gradient derived for iron is d[Fe/H]/dR=-0.05 dex/kpc, similar to gradients derived in previous studies.
- ID:
- ivo://CDS.VizieR/J/ApJ/522/802
- Title:
- Cepheid calibration of SN 1989B in NGC 3627
- Short Name:
- J/ApJ/522/802
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Repeated imaging observations have been made of NGC 3627 with the Hubble Space Telescope in 1997 - 1998 over an interval of 58 days. Images were obtained on 12 epochs in the F555W band and on five epochs in the F814W band. The galaxy hosted the prototypical, "Branch normal," type Ia supernova SN 1989B. A total of 83 variables have been found, of which 68 are definite Cepheid variables with periods ranging from 75 to 3.85 days. The dereddened distance modulus is determined to be (m-M)_o_=30.22{+/-}0.12 (internal uncertainty) using a subset of the Cepheid data whose reddening and error parameters are secure.
- ID:
- ivo://CDS.VizieR/J/ApJ/885/161
- Title:
- 90 cepheid candidates nearby NGC 6814
- Short Name:
- J/ApJ/885/161
- Date:
- 08 Mar 2022
- Publisher:
- CDS
- Description:
- We present a Cepheid-based distance to the nearby Seyfert galaxy NGC6814 from Hubble Space Telescope observations. We obtained F555W and F814W imaging over the course of 12 visits with logarithmic time spacing in 2013 August-October. We detected and made photometric measurements for 16469 unique sources across all images in both filters, from which we identify 90 excellent Cepheid candidates spanning a range of periods of 13-84days. We find evidence for incompleteness in the detection of candidates at periods <21days. Based on the analysis of Cepheid candidates above the incompleteness limit, we determine a distance modulus for NGC6814 relative to the LMC of {mu}_rel,LMC_=13.200_-0.031_^+0.031^mag. Adopting the recent constraint of the distance modulus to the LMC determined by Pietrzynski et al., we find m-M=31.677_-0.041_^+0.041^ which gives a distance of 21.65{+/-}0.41Mpc to NGC6814.
- ID:
- ivo://CDS.VizieR/J/A+A/659/A167
- Title:
- Cepheid Period-Wesenheit-Metallicity relation
- Short Name:
- J/A+A/659/A167
- Date:
- 23 Mar 2022 15:18:20
- Publisher:
- CDS
- Description:
- Classical Cepheids (DCEPs) represent a fundamental tool to calibrate the extragalactic distance scale. However, they are also powerful stellar population tracers, in the context of Galactic studies. The forthcoming Data Release 3 (DR3) of the Gaia mission will allow us to study with unprecedented detail the structure, the dynamics and the chemical properties of the Galactic disc, and in particular of the spiral arms, where most Galactic DCEPs reside. In this paper we aim at quantifying the metallicity dependence of the Galactic DCEPs Period-Wesenheit (PWZ) relation in the Gaia bands. We adopt a sample of 499 DCEPs with metal abundances from high-resolution spectroscopy, in conjunction with Gaia Early Data Release 3 parallaxes and photometry to calibrate a PWZ relation in the Gaia bands. We find a significant metallicity term, of the order of -0.5mag/dex, which is larger than the values measured in the NIR bands by different authors. Our best PWZ relation is W=(-5.988+/-0.018)-(3.176+/-0.044)(logP-1.0)-(0.520+/-0.090)[Fe/H]. We validate our PWZ relations by using the distance to the Large Magellanic Cloud as a benchmark, finding a very good agreement with the geometric distance provided by eclipsing binaries. As an additional test, we evaluate the metallicity gradient of the young Galactic disc, finding -0.0527+/-0.0022dex/kpc, in very good agreement with previous results.
