- ID:
- ivo://CDS.VizieR/J/PASP/97/753
- Title:
- BVR CCD photometry on NGC 1777
- Short Name:
- J/PASP/97/753
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photographic (B and V) and CCD (B, V, and R) photometry of stars in the remote LMC cluster NGC 1777, and integrated UBV photometry of the inner part of the cluster. A comparison of the results from the two techniques reveals large (~0.20m) systematic differences which we attribute to the difficulty of faint photometry. The photographic calibration depended on images produced by a Racine wedge, while the CCD calibration was accomplished in a manner analogous to photoelectric photometry. The stellar photometry provides a C-M diagram to V=21.5 which includes an evolved main sequence and a well-populated giant branch. A variety of methods, including comparisons of the observations to two sets of isochrones, allows us to estimate the cluster age as 0.9+/-0.2x10^9^ years. However we are only able to estimate the metallicity ([Fe/H]) crudely as -0.7+/-0.5. The C-M diagrams of the field in three regions near NGC 1777 indicate the presence of stars in the age range 1x10^9^ to >=3x10^9^ years, although we are unable to discern whether a mixture of two or more distinct populations or a continuous distribution of field-star ages is responsible for this spread.
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- ID:
- ivo://CDS.VizieR/J/ApJ/652/458
- Title:
- BVRH{alpha} photometry of candidates Be stars
- Short Name:
- J/ApJ/652/458
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present B, V, R, and H{alpha} photometry of eight clusters in the Small Magellanic Cloud, five in the Large Magellanic Cloud, and three Galactic clusters and use two-color diagrams (2-CDs) to identify candidate Be star populations in these clusters. We find evidence that the Be phenomenon is enhanced in low-metallicity environments, based on the observed fractional early-type candidate Be star content of clusters of age 10-25Myr.
- ID:
- ivo://CDS.VizieR/J/A+A/415/521
- Title:
- BVRIJK and velocities for MC Cepheids
- Short Name:
- J/A+A/415/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high precision and well sampled BVRIJK light curves and radial velocity curves for a sample of five (+1) Cepheids in the SMC. In addition we present radial velocity curves for five (+1) Cepheids in the LMC. The low metallicity ([Fe/H]~-0.7) SMC stars have been selected for use in a Baade-Wesselink type analysis to constrain the metallicity effect on the Cepheid Period-Luminosity relation. The stars have periods of around 15 days so they are similar to the Cepheids observed by the Extragalactic Distance Scale Key Project on the Hubble Space Telescope. We show that the stars are representative of the SMC Cepheid population at that period and thus will provide a good sample for the proposed analysis. The actual Baade-Wesselink analysis are presented in Strom et al., 2004, Cat. <J/A+A/415/531>.
- ID:
- ivo://CDS.VizieR/J/ApJS/142/71
- Title:
- BVRI observations of LMC Cepheids
- Short Name:
- J/ApJS/142/71
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A homogeneous set of ground-based BVRI observations of ~600 Cepheids is presented to check the Cepheid period-luminosity (PL) zero point for the Large Magellanic Cloud (LMC). The sample of Cepheids is completely self-contained and has been reduced consistently to eliminate photometric differences caused by combining multiple sources of photometry. The Cepheid distances to nearby galaxies obtained by the Hubble Space Telescope (HST) Key Project on the Extragalactic Distance Scale were computed assuming a "standard" PL relation based on a compilation of photoelectric observations of 34 Cepheids and a standard distance modulus to the LMC of 18.50. The final Key Project results substituted a statistically stronger PL relation obtained by the OGLE collaboration. In this paper we compare our data with the OGLE PL relation; the subsample of LMC Cepheids with similar periods to those discovered in the nearby galaxies is fainter at the relevant periods by 0.04+/-0.02mag than the OGLE sample. Substituting in turn this PL relation for that of the OGLE collaboration would raise the Hubble constant by 2%+/-1%, a correction which is not significant. The multicolor data set will also be useful in considering the effects of reddening and chemical composition and deriving an improved Cepheid period-luminosity relation for the LMC.
- ID:
- ivo://CDS.VizieR/J/MNRAS/386/1380
- Title:
- BVRI photometry of LMC star clusters
- Short Name:
- J/MNRAS/386/1380
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a CCD photometric and mass function study of nine young Large Magellanic Cloud star clusters, namely NGC 1767, 1994, 2002, 2003, 2006, SL 538, NGC 2011, 2098 and 2136. BVRI data, reaching down to V~21mag, were collected from the 3.5-m NTT/EFOSC2 in subarcsec seeing conditions. For NGC 1767, 1994, 2002, 2003, 2011 and 2136, broad-band photometric CCD data are presented for the first time.
- ID:
- ivo://CDS.VizieR/J/A+A/436/117
- Title:
- BVR photometry in N214C
- Short Name:
- J/A+A/436/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the Large Magellanic Cloud HII region N 214C using imaging and spectroscopy obtained at the ESO New Technology Telescope. On the basis of the highest resolution images so far obtained of the OB association LH 110, we show that the main exciting source of the HII region, Sk -71 51, is in fact a tight cluster of massive stars consisting of at least 6 components in an area ~4" wide. Spectroscopic observations allow us to revise the spectral type of the main component (#17) to O2V((f*))+OB, a very rare, hot type. We also classify several other stars associated with N 214C and study the extinction and excitation characteristics of the HII region. Moreover, we obtain BVR photometry and astrometry of 2365 stars and from the corresponding color-magnitude diagram study the stellar content of N 214C and the surrounding LH 110. Furthermore, we discover a striking compact blob of ionized gas in the outer northern part of N 214C. A spherical structure of ~5", in radius (~1.3pc), it is split into two lobes by absorbing dust running diametrically through its center. We discuss the possible nature of this object.
- ID:
- ivo://CDS.VizieR/J/AJ/136/1039
- Title:
- CaII index of SMC red giant branch stars
- Short Name:
- J/AJ/136/1039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present stellar metallicities derived from Ca II triplet spectroscopy in over 350 red giant branch stars in 13 fields distributed in different positions in the Small Magellanic Cloud, ranging from ~1{deg} to ~4{deg} from its center. In the innermost fields, the average metallicity is [Fe/H]~-1. This value decreases when we move away toward outermost regions. This is the first detection of a spectroscopic metallicity gradient in this galaxy. We show that the metallicity gradient is related to an age gradient, in the sense that more metal-rich stars, which are also younger, are concentrated in the central regions of the galaxy.
- ID:
- ivo://CDS.VizieR/J/A+A/582/A59
- Title:
- CaIIK spectra of 7 Galactic and MC open clusters
- Short Name:
- J/A+A/582/A59
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The large and small-scale (pc) structure of the Galactic interstellar medium can be investigated by utilising spectra of early- type stellar probes of known distances in the same region of the sky. This paper determines the variation in line strength of CaII at 3933.661{AA} as a function of probe separation for a large sample of stars, including a number of sightlines in the Magellanic Clouds. FLAMES-GIRAFFE data taken with the Very Large Telescope towards early-type stars in 3 Galactic and 4 Magellanic open clusters in CaII are used to obtain the velocity, equivalent width, column density, and line width of interstellar Galactic calcium for a total of 657 stars, of which 443 are Magellanic Cloud sightlines. In each cluster there are between 43 and 111 stars observed. Additionally, FEROS and UVES CaII K and NaI D spectra of 21 Galactic and 154 Magellanic early-type stars are presented and combined with data from the literature to study the calcium column density - parallax relationship.
- ID:
- ivo://CDS.VizieR/J/AJ/132/1630
- Title:
- CaII spectroscopy in Magellanic Cloud clusters
- Short Name:
- J/AJ/132/1630
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the FORS2 instrument on the Very Large Telescope, we have obtained near-infrared spectra for more than 200 stars in 28 populous LMC clusters. This cluster sample spans a large range of ages (~113Gyr) and metallicities (-0.3>~[Fe/H]>~-2.0) and has good areal coverage of the LMC disk. The strong absorption lines of the Ca II triplet are used to derive cluster radial velocities and abundances. We determine mean cluster velocities to typically 1.6km/s and mean metallicities to 0.04dex (random error). For eight of these clusters, we report the first spectroscopically determined metallicities based on individual cluster stars, and six of these eight have no published radial velocity measurements. Combining our data with archival Hubble Space Telescope WFPC2 photometry, we find that the newly measured cluster, NGC 1718, is one of the most metal-poor ([Fe/H]~-0.80) intermediate-age (~2Gyr) inner disk clusters in the LMC. Similar to what was found by previous authors, this cluster sample has radial velocities consistent with that of a single rotating disk system, with no indication that the newly reported clusters exhibit halo kinematics. In addition, our findings confirm previous results that show that the LMC lacks the metallicity gradient typically seen in non-barred spiral galaxies, suggesting that the bar is driving the mixing of stellar populations in the LMC.
- ID:
- ivo://CDS.VizieR/J/AJ/139/1168
- Title:
- CaII spectroscopy of SMC fields stars
- Short Name:
- J/AJ/139/1168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained metallicities of ~360 red giant stars distributed in 15 Small Magellanic Cloud (SMC) fields from near-infrared spectra covering the CaII triplet lines using the VLT + FORS2.
