- ID:
- ivo://CDS.VizieR/J/A+A/360/529
- Title:
- BVI photometry of 4 young open clusters
- Short Name:
- J/A+A/360/529
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD observations in the B, V, and I passbands obtained for stars in the fields of the open clusters Pismis 22, NGC 6178, NGC 6216, and Ruprecht 130, projected not far from the Galactic centre (|l|<30{deg}, |b|<2{deg}). The sample consists of about 790 stars reaching down to V~18-19mag. From the analysis of the colour magnitude diagrams, we confirmed the physical reality of the clusters and derived their reddening, distance and age. In addition, we obtained flux-calibrated integrated spectra in the range 3500-9200{AA} for the cluster sample. The equivalent widths of the Balmer lines provided us with age estimates, while the comparison with template spectra allowed us to derive both foreground reddening and age. The photometric and spectroscopic results reveal that the four studied objects are young open clusters with ages ranging between 35 and 50Myr. The clusters, located between 1.0kpc and 4.3kpc from the Sun, are affected by different amounts of interstellar visual absorption (0.6=~A_v_=~6.0).
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/139/2014
- Title:
- BV light curves of 11 RR Lyrae
- Short Name:
- J/AJ/139/2014
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- It is not easy to identify and classify low-amplitude variables, but it is important that the classification is done correctly. We use photometry and spectroscopy to classify low-amplitude variables in a 246deg^2^ part of the Akerlof et al. (2000, Cat. J/AJ/119/1901) field. Akerlof and Collaborators found that 38% of the RR Lyrae stars in their 2000deg^2^ test field were RR1 (type c). This suggests that these RR Lyrae stars belong to an Oosterhoff Type II population, while their period distribution is primarily Oosterhoff Type I. Our observations support their RR0 (type ab) classifications; however, six of the seven stars that they classified as RR1 (type c) are eclipsing binaries. Our classifications are supported by spectroscopic metallicities, line-broadening, and Galactic rotation measurements. Our 246deg^2^ field contains 16 RR Lyrae stars that are brighter than m_R_=14.5; only four of these are RR1 (type c). This corresponds to an Oosterhoff Type I population in agreement with the period distribution.
- ID:
- ivo://CDS.VizieR/J/A+A/418/249
- Title:
- BV light curves of WX Eridani
- Short Name:
- J/A+A/418/249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- WX Eri is an eclipsing binary system for which one component was reported to show Delta Scuti type pulsations with periods close to integer fractions of the orbital period. This makes it an interesting candidate for investigating the interaction between binarity and pulsation and a potential new member of the recently defined group of mass-accreting pulsating components (gainers) in semi-detached Algol binaries called 'oscillating EA' stars. We present new photometric time-series observations of this star. The Wilson-Devinney code was applied to find the best fitting model for the eclipsing binary's light curve. The aim of the observations was to investigate the short-period Delta Scuti type pulsations of WX Eri. However, no evidence for the presence of such oscillations was found in our data.
- ID:
- ivo://CDS.VizieR/J/AJ/117/2868
- Title:
- BV photometry in M2 (NGC 7089)
- Short Name:
- J/AJ/117/2868
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present BV CCD photometry for 30 RR Lyrae variables, including 13 newly discovered, in the Oosterhoff type II globular cluster M2. New light curves and ephemerides are presented. Our observations cover magnitudes ranging from the red giant branch tip to ~3mag below the turnoff, allowing us to determine accurate fundamental photometric parameters. With the discovery of new RR Lyrae variables, the mean periods of the RRab and RRc variables are <P_ab_>=0.685+/-0.022days and <P_c_>=0.333+/-0.013days, respectively. The number ratio of the RRc type variables to the total number of RR Lyrae type variables is n(c)/n(ab+c)=0.40. The RR Lyrae pulsational mode transition occurs between the fundamental period of 0.528-days and 0.556-days. From star counts along the horizontal branch (HB), we obtain two HB color distribution indices, (B-R)/(B+V+R)=0.92 and B2/(B+V+R)=0.46. The period-change rates are also derived. The mean period-change rate from six RRab variables is <{beta}>=0.06+/-0.04days/Myr, which agrees well with the predictions of Lee's 1991 model. Our color-magnitude diagram shows a very extended blue HB tail, and there are no significant blue HB gaps in M2.
- ID:
- ivo://CDS.VizieR/J/AJ/121/318
- Title:
- BV photometry in NGC 5986
- Short Name:
- J/AJ/121/318
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained new CCD BV photometry of the little-studied southern Galactic globular cluster NGC 5986, including light curves of five of its RR Lyrae variables. The cluster's red giant branch bump is detected for the first time, at V=16.47 +/-0.03. We derive a reddening and true distance modulus of E(B-V)=0.29+/-0.02 and (m-M)_0_=15.15+/-0.10, respectively. The cluster's color-magnitude diagram reveals a mostly blue horizontal branch, like that of M13 or M2, and quite unlike M3; yet all of these clusters have nearly identical metallicities ([Fe/H]_CG97_=-1.35). We show that the RR Lyrae variables in NGC 5986 are about 0.2mag brighter on average than those in M3, an important exception to the often-employed, universal M_V_(RR)-[Fe/H] relation. Finally, we note that NGC 5986 contains two luminous stars with spectral types A-F, which are likely to be post-asymptotic giant branch (PAGB) objects. The V-band luminosity function of such yellow PAGB stars is a promising standard candle. We suggest that the luminosity function is sharply peaked at M_V_(PAGB)=-3.28+/-0.07.
- ID:
- ivo://CDS.VizieR/J/A+A/328/167
- Title:
- BV photometry in supergiant shell LMC4
- Short Name:
- J/A+A/328/167
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The youngest stellar populations of a 'J'-shaped region inside the supergiant shell (SGS) LMC4 have been analysed with CCD photometry in B, V passbands. This region consists of 2 coherent strips, one from the east to the west reaching about 400pc across the OB superassociation LH 77 and another extending about 850pc from south to north. The standard photometric methods yield for each of the 25 CCD fields a colour-magnitude diagram (CMD) which is used for age determination of the youngest star population by isochrone fitting. The resultant ages lie in the range from 9Myr to 16Myr without correlation with the distance to the LMC 4 centre. We therefore conclude that there must have been one triggering event for star formation inside this large LMC SGS with a diameter of 1.4kpc.
- ID:
- ivo://CDS.VizieR/J/A+AS/144/227
- Title:
- BV photometry of M71
- Short Name:
- J/A+AS/144/227
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- File table2 contains coordinates (J2000) and B,V magnitudes and B-V colours with corresponding errors of 4450 stars in a 20'x20' region centered on the globular cluster M 71 (NGC 6838). The limiting magnitude of the catalogue is about V=18.0 The observations were made in 1995 at Calar Alta Observatory.
- ID:
- ivo://CDS.VizieR/J/AJ/116/1775
- Title:
- BV photometry of M53
- Short Name:
- J/AJ/116/1775
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The first large-format CCD color-magnitude diagram (CMD) in the B and V passbands is presented for the Galactic globular cluster M53 (NGC 5024). The observations consist of 40 pairs of B and V CCD frames with FWHM<1.2" in a pattern covering a 12'x13' region of M53. These frames were used to produce color-magnitude data for more than 20,000 stars from the tip of the red giant branch (RGB) to about 2 mag below the main-sequence turnoff (V~22). The CMD reveals a classic example of a metal-poor stellar system, with the horizontal branch (HB) predominantly blueward of the RR Lyrae instability strip and the relatively steep RGB. The blue HB of M53 does not show the blue tail phenomenon that is observed in M15. The relative age dating based on the color difference between the turnoff and the base of RGB reveals no significant age difference ({Delta}t<1Gyr) between M53 and M92. We have discovered 114 new blue straggler stars (BSSs) in the field of M53. The analysis of bright (V<19.39) BSSs clearly shows a bimodal radial distribution with a high frequency in the inner and outer regions but a distinct dip in the intermediate region. The distribution is similar to that found in M3, a globular cluster with a similar central density and concentration.
- ID:
- ivo://CDS.VizieR/J/MNRAS/243/492
- Title:
- BV Photometry of NGC 6791
- Short Name:
- J/MNRAS/243/492
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD BV photometry to V=20.5 of stars in the old open cluster NGC 6791 is presented. Comparison with the theoretical isochrones of VandenBerg gives a cluster age in the range of 10 to 12.5Gyr, and an apparent distance modulus of 13.45mag, adopting a solar metallicity. This cluster is only marginally younger than Palomar 12, which is the youngest globular cluster known. A search for short-period variables in the cluster field led to the discovery of only one low-amplitude variable, probably belonging to the FK Com-type stars. A very blue star was detected which may be an extremely young white dwarf formed in the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/112/1061
- Title:
- BV photometry of NGC 7099
- Short Name:
- J/AJ/112/1061
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New BV CCD photometry for the bright stars in cluster fields centered on the core of NGC 7099 is presented. The morphology of the LF though the turnoff region is similar to that found in other metal-poor clusters in that the relative number of turnoff to giant stars is lower than predicted by canonical models. Comparisons with evolutionary sequences of horizontal branch stars suggest a reddening E(B-V)=0.06 and a distance modulus (m-M)_V=14.83. Isochrone fits to [Fe/H]=-2.03, [O/Fe]=+0.70 models are consistent with an age of at least 14 Gyr. The model LF for this age accurately predicts the brightness of the tip of the red giant branch (RGB) as well as the location of the break which signals the transition from the base of the RGB to the main sequence. There is an indication that the evolutionary pause on the RGB, which manifests itself as a bump in the LF, occurs one magnitude fainter than the models predict. The excess of HB stars with respect to giants is confirmed and implies a helium abundance Y=0.28, which is higher than that found in other metal-poor globular clusters from the R method. From a comparison with the metal-rich, blue horizontal branch cluster NGC 288, it is argued that age cannot by itself be the solution to the second parameter problem.
