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531. BV light curves of 11 RR Lyrae
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.
532. BV photometry and Li abundances in NGC3960
ID:
ivo://CDS.VizieR/J/A+A/475/539
Title:
BV photometry and Li abundances in NGC3960
Short Name:
J/A+A/475/539
Date:
21 Oct 2021
Publisher:
CDS
Description:
Old open clusters are very useful targets to investigate mechanisms responsible for lithium (Li) depletion during the main sequence. Comparison of the Li abundances in clusters of different age allows us to understand the efficiency of the Li destruction process. To determine the membership and Li abundance in a sample of candidate members of the open cluster NGC 3960 (age ~1Gyr), aiming to fill the gap between 0.6 and 2Gyr in the empirical description of the behavior of the average Li abundance as a function of the stellar age. We use VLT/FLAMES Giraffe spectra to determine the radial velocities and thus the membership of a sample of 113 photometrically selected candidate cluster members. From the analysis of the Li line we derive Li abundances for both cluster members and non-members. 39 stars have radial velocities consistent with membership, with an expected fraction of contaminating field stars of about 20%. Li is detected in 29 of the radial velocity members; we consider these stars as cluster members, while we make the reasonable assumption that the remaining 10 radial velocity members without Li are among the contaminating stars. Li abundances of the stars hotter than about 6000K are similar to those of stars in the Hyades, while they are slightly smaller for cooler stars. This confirms that NGC 3960 is older than the Hyades. The average Li abundance of stars cooler than about 6000K indicates that the Li Pop. I plateau might start at ~1Gyr, rather than 2Gyr, which is the upper limit previously derived in the literature. We also find that the fraction of field stars with high Li abundance (>1.5) is about one third of the whole sample, which is in agreement with previous estimates. The fraction of contaminating field stars is consistent with that previously derived by us from photometry.
533. BV photometry for components of HIP doubles
ID:
ivo://CDS.VizieR/J/A+A/356/141
Title:
BV photometry for components of HIP doubles
Short Name:
J/A+A/356/141
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using observations obtained with the Tycho instrument of the ESA Hipparcos satellite, a two-colour photometry is produced for components of more than 7000 Hipparcos double and multiple stars with angular separations 0.1 to 2.5 arcsec. We publish 9473 components of 5173 systems with separations above 0.3 arcsec. The majority of them did not have Tycho photometry in the Hipparcos catalogue. The magnitudes are derived in the Tycho B_T and V_T passbands, similar to the Johnson passbands. Photometrically resolved components of the binaries with statistically significant trigonometric parallaxes can be put on an HR diagram, the majority of them for the first time.
534. BV photometry in and around 5 globular clusters
ID:
ivo://CDS.VizieR/J/AJ/147/155
Title:
BV photometry in and around 5 globular clusters
Short Name:
J/AJ/147/155
Date:
21 Oct 2021
Publisher:
CDS
Description:
Homogeneous B, V photometry is presented for 19324 stars in and around 5 Magellanic Cloud globular clusters: NGC 1466, NGC 1841, NGC 2210, NGC 2257, and Reticulum. The photometry is derived from eight nights of CCD imaging with the Cerro Tololo Inter-American Observatory 0.9m SMARTS telescope. Instrumental magnitudes were transformed to the Johnson B, V system using accurate calibration relations based on a large sample of Landolt-Stetson equatorial standard stars, which were observed on the same nights as the cluster stars. Residual analysis of the equatorial standards used for the calibration, and validation of the new photometry using Stetson's sample of secondary standards in the vicinities of the five Large Magellanic Cloud clusters, shows excellent agreement with our values in both magnitudes and colors. Color-magnitude diagrams reaching to the main-sequence turnoffs at V~22mag, sigma-magnitude diagrams, and various other summaries are presented for each cluster to illustrate the range and quality of the new photometry. The photometry should prove useful for future studies of the Magellanic Cloud globular clusters, particularly studies of their variable stars.
535. (BV) photometry in Carina dSph
ID:
ivo://CDS.VizieR/J/A+A/572/A10
Title:
(BV) photometry in Carina dSph
Short Name:
J/A+A/572/A10
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present deep photometry of the Carina dwarf Spheroidal galaxy in the B,V filters from CTIO/MOSAIC, out to and beyond the tidal radius of r_ell_~0.48{deg}. The accurately calibrated photometry is combined with spectroscopic metallicity distributions of Red Giant Branch stars to determine the detailed star formation and chemical evolution history of Carina. The star formation history confirms the episodic formation history of Carina and quantifies the duration and strength of each episode in great detail, as a function radius from the centre. Two main episodes of star formation occurred at old (>8Gyr) and intermediate (2-8Gyr) ages, both enriching stars starting from low metallicities ([Fe/H]<-2dex). By dividing the SFH into two components, we determine that 60+/-9 percent of the total number of stars formed within the intermediate age episode. Furthermore, within the tidal radius (0.48{deg} or 888pc) a total mass in stars of 1.07+/-0.08x10^6^M_{sun}_ was formed, giving Carina a stellar mass-to-light ratio of 1.8+/-0.8. Combining the detailed star formation history with spectroscopic observations of RGB stars, we are able to determine the detailed age-metallicity relation of each episode and the timescale of alpha-element evolution of Carina from individual stars. The oldest episode displays a tight age-metallicity relation during ~6Gyr with steadily declining alpha-element abundances and a possible alpha-element knee visible at [Fe/H]~-2.5dex. The intermediate age sequence displays a more complex age-metallicity relation starting from low metallicity and a sequence in alpha-element abundances with a slope much steeper than observed in the old episode, starting from [Fe/H]=-1.8dex and [Mg/Fe]~0.4dex and declining to Mg-poor values ([Mg/Fe]<-0.5dex). This indicates clearly that both episodes of star formation formed from gas with different abundance patterns , inconsistent with simple evolution in an isolated system.
536. BV photometry in Draco molecular cloud
ID:
ivo://CDS.VizieR/J/A+A/364/712
Title:
BV photometry in Draco molecular cloud
Short Name:
J/A+A/364/712
Date:
21 Oct 2021
Publisher:
CDS
Description:
To investigate the distance and linear dimensions of the Draco Molecular Cloud (MBM 41) we have obtained new CCD photometry for a selection of stars in 20 selected areas toward the cores of the cloud. The selected areas were chosen to coincide with the brightest IRAS emitting portions of the cloud, and also with dense ^12^CO emission from the cloud. For each area we have obtained V and B photometry, and a subset of the fields has also been observed through a narrow-band H{alpha} filter and in the U band. We present V and B magnitudes for the 362 stars which have high-quality observations in both bands. The observations were made during the nights of June 29 and June 30, 1993 at the Palomar Observatory, using the 1.5-meter telescope and Palomar 6 Tektronix CCD camera with 24 micron pixels.
537. BV photometry in Leo IV and Leo V dSphs
ID:
ivo://CDS.VizieR/J/ApJ/710/1664
Title:
BV photometry in Leo IV and Leo V dSphs
Short Name:
J/ApJ/710/1664
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained deep photometry in two 1{deg}x1{deg} fields covering the close pair of dwarf spheroidal galaxies Leo IV and Leo V and part of the area in between. From the distribution of likely red giant branch (RGB) and horizontal-branch (HB) stars in the data set, we find that both Leo IV and Leo V are significantly larger than indicated by previous measurements based on shallower data. With a half-light radius of r_h_=4.6'+/-0.8' (206+/-36pc) and r_h_=2.6'+/-0.6' (133+/-31pc), respectively, both systems are now well within the physical size bracket of typical dwarf spheroidal Milky Way satellites. Both are also found to be significantly elongated with an ellipticity of {epsilon}~0.5, a characteristic shared by many of the fainter (M_V_>-8) Milky Way dwarf spheroidals. The large spatial extent of our survey allows us to search for extra-tidal features in the area between the two dwarf galaxies with unprecedented sensitivity. The spatial distribution of candidate RGB and HB stars in this region is found to be non-uniform at the ~3{sigma} level. We investigate different scenarios to explain the close proximity of Leo IV and Leo V, and the possible tidal bridge between them.
538. BV photometry in M2 (NGC 7089)
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.
539. BV photometry in NGC 5986
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.
540. BV photometry in supergiant shell LMC4
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.