- ID:
- ivo://CDS.VizieR/J/ApJ/826/110
- Title:
- Boo-127 and Boo-980 high-resolution spectra
- Short Name:
- J/ApJ/826/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundance measurements of two metal-poor red giant stars in the ultra-faint dwarf galaxy Bootes I, based on Magellan/MIKE high-resolution spectra. For Boo-980, with [Fe/H]=-3.1 , we present the first elemental abundance measurements, while Boo-127, with [Fe/H]=-2.0 , shows abundances in good agreement with previous measurements. Light and iron-peak element abundance ratios in the two Bootes I stars, as well as those of most other Bootes I members, collected from the literature, closely resemble those of regular metal-poor halo stars. Neutron-capture element abundances Sr and Ba are systematically lower than the main halo trend and also show a significant abundance spread. Overall, this is similar to what has been found for other ultra-faint dwarf galaxies. We apply corrections to the carbon abundances (commensurate with stellar evolutionary status) of the entire sample and find 21% of stars to be carbon-enhanced metal-poor (CEMP) stars, compared to 13% without using the carbon correction. We reassess the metallicity distribution functions for the CEMP stars and non-CEMP stars, and confirm earlier claims that CEMP stars might belong to a different, earlier population. Applying a set of abundance criteria to test to what extent Bootes I could be a surviving first galaxy suggests that it is one of the earliest assembled systems that perhaps received gas from accretion from other clouds in the system, or from swallowing a first galaxy or building block type object. This resulted in the two stellar populations observable today.
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- ID:
- ivo://CDS.VizieR/J/A+A/486/177
- Title:
- Bulge field stars from FLAMES-GIRAFFE spectra
- Short Name:
- J/A+A/486/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We determine the iron distribution function (IDF) for bulge field stars, in three different fields along the Galactic minor axis and at latitudes b=-4{deg}, b=-6{deg}, and b=-12{deg}. A fourth field including NGC 6553 is also included in the discussion. About 800 bulge field K giants were observed with the GIRAFFE spectrograph of FLAMES@VLT at spectral resolution R~20000. Several of them were observed again with UVES at R~45000 to insure the accuracy of the measurements. The LTE abundance analysis yielded stellar parameters and iron abundances that allowed us to construct an IDF for the bulge that, for the first time, is based on high-resolution spectroscopy for each individual star.
- ID:
- ivo://CDS.VizieR/J/ApJ/663/277
- Title:
- BVI of NGC 5466 red giants and blue stragglers
- Short Name:
- J/ApJ/663/277
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present wide-field BVI photometry for about 11500 stars in the low-metallicity cluster NGC 5466. We have detected the red giant branch bump for the first time, although it is at least 0.2mag fainter than expected relative to the turnoff. The number of red giants (relative to main-sequence turnoff stars) is in excellent agreement with stellar models from the Yonsei-Yale and Teramo groups, and slightly high compared to Victoria-Regina models. This adds to evidence that an abnormally large ratio of red giant to main-sequence stars is not correlated with cluster metallicity.
- ID:
- ivo://CDS.VizieR/J/ApJ/611/323
- Title:
- BVI photometry of M5 giant branch stars
- Short Name:
- J/ApJ/611/323
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have tabulated lists of upper red giant, horizontal-, and asymptotic giant branch (RGB, HB, and AGB) stars in the globular cluster M5 that are complete to over 10' from the core for the RGB and AGB samples, and 8' for the HB sample. The large samples give us the most precise value of R_2_=N_AGB_/N_HB_ to date for a single globular cluster (0.176+/-0.018).
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/265
- Title:
- BVI photometry of omega Cen red giants
- Short Name:
- J/MNRAS/357/265
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalogue of omega Cen is based on ground-based observations using FORS1@VLT and contains more than 100,000 stars covering an area of 9"x9" around the center of the cluster. The limiting magnitude is V>=21mag and the positional accuracy is better than 0.2" .
- ID:
- ivo://CDS.VizieR/J/BaltA/14/41
- Title:
- BV(RI)C photometry of 4 S-type AGB
- Short Name:
- J/BaltA/14/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present FCAPT differential Johnson BV and Cousins RI photometry and radial velocities of the S-type AGB stars RS Cnc, ST Her, OP Her and HR Peg. We performed multiperiodic analyses of this photometry to learn about the frequencies of variability. The B, V, R, and I light curves are generally in phase. RS Cnc has periods of order 122 and 248 days. Repeating the analyses using our data with the extensive V and R photometry of Percy et al. (2001PASP..113..983P) shows several periods near 248 days and a period near 135 days. The primary period of ST Her appears to be about 144 days although it is manifested most readily by its 103 day alias. OP Her and HR Peg exhibit periods, respectively, of about 416 and 116 days and of 54 and 74 days. The differences between our data set and the larger one of Percy et al. (2001PASP..113..983P) for RS Cnc raises important questions about multiperiodic analyses for AGB stars.
- ID:
- ivo://CDS.VizieR/J/A+A/385/884
- Title:
- BVRIJHK photometry of 27 post-AGB candidates
- Short Name:
- J/A+A/385/884
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- BVRIJHK photometric observations are presented for 27 post-AGB candidates. Almost all objects show a double peaked spatial energy distribution (SED) curve in the optical to far-infrared wavelengths. Seventeen objects were classified as post-AGB stars on the basis of their spectral type, location in the IRAS color-color diagram and SED. The physical parameters of the observed post-AGB stars, the inner radius of the detached shell, the mass of the shell and the distance were derived using the simple dust shell model. We compared our observational sequence of post-AGB objects to the theoretical evolutionary sequence (Schoenberner, 1983ApJ...272..708S; Bloecker, 1995, Cat. <J/A+A/299/755>) in the stellar temperatures versus age diagram. We found that two post-AGB stars, IRAS 05040+4820 and 08187-1905, have low stellar temperature with a large dynamical age of the dust shell. They appear to provide the first observational evidence that some low-mass stars bypass the planetary nebulae stage because of their slow increase in stellar temperature.
- ID:
- ivo://CDS.VizieR/J/other/JAD/13.3
- Title:
- BVRI light curves of some cool giant stars
- Short Name:
- J/other/JAD/13.3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We examine Johnson BV and Cousins RI photometry of the cool giant stars HR 1105, HD 35155, HR 4088, TU CVn, IT Vir, and HR 7442, that the first author obtained with the Four College Automated Photoelectric Telescope. The new data for HR 1105 show that its variability is more complex than previously thought. Except a 0.3 phase gap in the photometry of HD 35155, the amplitude of variability is fairly constant. For HR 4088, except for one season, we did not find any periods shorter than 100 days. For the barium star IT Vir assuming the orbital period is the photometric period, the light curves consist of two similar subparts each one-half of the orbital period long. But there are problems with concluding that this star is an ellipsoidal variable. For HR 7442, more data is needed to derive an accurate period. A few observations are also presented of HR 1556, HR 363, HD 58521, and HD 49368.
- ID:
- ivo://CDS.VizieR/J/ApJ/462/241
- Title:
- Ca abundance for Omega Cen red giants
- Short Name:
- J/ApJ/462/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an unbiased catalog of calcium abundances for 517 red giants brighter than M_V_~-1 in the chemically inhomogeneous globular cluster omega Centauri. The basic features of the abundance distribution are as follows: (1) few, if any, stars exist on the giant branch of omega Cen with [Ca/H] less than -1.6; (2) there is a well-defined peak in the distribution at [Ca/H]=-1.4, with a long tail stretching up to ~[Ca/H]~-0.3; and (3) the distribution is bimodal with a second smaller peak in the distribution at [Ca/H]=-0.9.
- ID:
- ivo://CDS.VizieR/J/ApJS/219/7
- Title:
- Ca,by photometry in globular clusters. I. M22
- Short Name:
- J/ApJS/219/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the multiple stellar populations in one of the peculiar globular clusters (GCs), M22, using new ground-based wide-field Ca by and Hubble Space Telescope Wide-Field Camera 3 photometry with equivalent passbands, confirming our previous result that M22 has a distinctive red giant branch (RGB) split mainly due to the difference in metal abundances. We also make use of radial velocity measurements by others of the large number of cluster membership stars. Our main results are the following. (1) The RGB and the subgiant branch number ratios show that the calcium-weak (Ca-w) group is the dominant population of the cluster. However, an irreconcilable difference can be seen in the rather simple classification into two horizontal branches by others. (2) Each group has its own CN-CH anticorrelation. However, the alleged CN-CH positive correlation is likely illusory. (3) The location of the RGB bump of the calcium-strong (Ca-s) group is significantly fainter, which may pose a challenge to the helium enhancement scenario in the Ca-s group. (4) The positions of the centers are similar. (5) The Ca-w group is slightly more centrally concentrated, whereas the Ca-s is more elongated at larger radii. (6) The mean radial velocities for both groups are similar, but the Ca-s group has a larger velocity dispersion. (7) The Ca-s group rotates faster. The plausible scenario for the formation of M22 is that it formed via a merger of two GCs in a dwarf galaxy environment and accreted later to our Galaxy.
