- ID:
- ivo://CDS.VizieR/J/ApJ/712/L21
- Title:
- Calcium abundances in 17 globular clusters
- Short Name:
- J/ApJ/712/L21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use abundances of Ca, O, Na, and Al from high-resolution UVES spectra of 200 red giants in 17 globular clusters (GCs) to investigate the correlation found by Lee et al. (2009Icar..199..413C) between chemical enrichment from SNII and star-to-star variations in light elements in GC stars. We find that (1) the [Ca/H] variations between first and second generation stars are tiny in most GCs (~0.02-0.03dex, comparable with typical observational errors). In addition, (2) using a large sample of red giants in M4 (NGC 6121) with abundances from UVES spectra from Marino et al. (2008, Cat. J/A+A/490/625), we find that Ca and Fe abundances in the two populations of Na-poor and Na-rich stars are identical.
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- ID:
- ivo://CDS.VizieR/J/AJ/135/836
- Title:
- Calcium triplet index in LMC stars
- Short Name:
- J/AJ/135/836
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Infrared CaII triplet (CaT) spectroscopy has been used to derive stellar metallicities for individual stars in four Large Magellanic Cloud fields situated at galactocentric distances of 3{deg}, 5{deg}, 6{deg}, and 8{deg} to the north of the bar. The combination of spectroscopy with deep CCD photometry has allowed us to break the RGB age-metallicity degeneracy and compute the ages for the objects observed spectroscopically. The obtained age-metallicity relationships (AMRs) for our four fields are statistically indistinguishable. We conclude that the lower mean metallicity in the outermost field is a consequence of it having a lower fraction of intermediate-age stars, which are more metal-rich than the older stars. The disk AMR is similar to that for clusters. However, the lack of objects with ages between 3 and 10Gyr is not observed in the field population. Finally, we used data from the literature to derive consistently the AMR of the bar. Simple chemical evolution models have been used to reproduce the observed AMRs with the purpose of investigating which mechanism has participated in the evolution of the disk and bar.
- ID:
- ivo://CDS.VizieR/J/A+AS/130/513
- Title:
- Calcium triplet synthesis
- Short Name:
- J/A+AS/130/513
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present theoretical equivalent widths for the sum of the two strongest lines of the calcium triplet, CaT index, in the near-IR ({lambda}{lambda} 8542, 8662{AA}), using evolutionary synthesis techniques and the most recent models and observational data for this feature in individual stars. We compute the CaT index for Single Stellar Populations (instantaneous burst, standard Salpeter-type IMF at four different metallicities, Z=0.004, 0.008, 0.02 (solar) and 0.05, and ranging in age from very young bursts of star formation (few Myr) to old stellar populations, up to 17Gyr, representative of galactic globular clusters, elliptical galaxies and bulges of spirals. The interpretation of the observed equivalent widths of CaT in different stellar systems is discussed. Composite-population models are also computed as a tool to interpret the CaT detections in star-forming regions, in order to disentangle between the component due to Red Supergiant stars, RSG, and the underlying, older, population. CaT is found to be an excellent metallicity-indicator for populations older than 1 Gyr, practically independent of the age. We discuss its application to remove the age-metallicity degeneracy, characteristic of all studies of galaxy evolution based on the usual integrated indices (both broad band colors and narrow band indices). The application of the models computed here to the analysis of a sample of elliptical galaxies will be discussed in a forthcoming paper Gorgas et al. 1997).
- ID:
- ivo://CDS.VizieR/J/AZh/82/437
- Title:
- Calculated chemical composition of galactic PN
- Short Name:
- J/AZh/82/437
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a study of the chemical compositions of Galactic planetary nebulae taking into account two types of inhomogeneity in the nebular gas density in their envelopes are reported. New analytical expressions for the ionization correction factors have been derived and are used to determine the chemical compositions of the nebular gas in Galactic planetary nebulae. The abundances of He, N, O, Ne, S, and Ar have been found for 193 objects. The Y-Z diagrams for various He abundances are analyzed for type II planetary nebulae separately and jointly with HII regions. The primordial helium abundance Yp and enrichment ratio dY/dZ are determined, and the resulting values are compared with the data of other authors. Radial abundance gradients in the Galactic disk are studied using type II planetary nebulae.
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/471
- Title:
- Calculated spectra for HeH^+^
- Short Name:
- J/MNRAS/357/471
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The wavelength and Einstein A coefficient are calculated for all rotation-vibration transitions of ^4^HeH^+^, ^3^HeH^+^, ^4^He^2^H^+^ and ^3^He^2^H^+^, giving a complete line list and the partition function for ^4^HeH^+^ and its isotopologues. This opacity is included in the calculation of the total opacity of low-metallicity stars and its effect is analysed for different conditions of temperature, density and hydrogen number fraction. For a low helium number fraction (as in the Sun), it is found that HeH^+^ has a visible but small effect for very low densities ({rho}<=10^-10^g/cm^3^), at temperatures around 3500K. However, for high helium number fraction, the effect of HeH^+^ becomes important for higher densities ({rho}<=10^-6^g/cm^3^), its effect being most important for a temperature around 3500K. Synthetic spectra for a variety of different conditions are presented.
- ID:
- ivo://CDS.VizieR/J/A+AS/137/269
- Title:
- Calern Observatory absolute declinations
- Short Name:
- J/A+AS/137/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A regular observational programme with a photoelectric astrolabe have been performed at ``Observatoire du Calern" (Observatoire de la Cote d'Azur, OCA, {phi}=+43{deg}44'55.011"; {lambda}=-0^h^27^m^42.44^s^, Calern, Caussols, France) for the last twenty years. It has been almost fully automatized between 1984 and 1987. Since 1988 the photoelectric astrolabe was used without any modification. In addition to determining the daily orientation of the local vertical, the yearly analysis of the residuals permits to derive corrections to the used star catalogue Vigouroux et al. (1992A&AS...96..477V). A global reduction method was applied for the ASPHO observations. The new form of the equations Martin & Leister (1997A&AS..126..169M) give us the possibility of using the entire set of the observing program using data taken at two zenith distances (30{deg} and 45{deg}). The program contains about 41648 stars' transits of 269 different stars taken at ``Observatoire du Calern" (OCA). The reduction was based on the HIPPARCOS system. We discuss the possibility of computing absolute declinations through stars belonging simultaneously to the 30{deg} and 45{deg} zenith distances programmes. The absolute declination corrections were determined for 185 stars with precision of 0.027" and the value of the determined equator correction is -0.018"+/-0.005". The instrumental effects were also determined. The mean epoch is 1995.29.
- ID:
- ivo://CDS.VizieR/J/A+A/622/A50
- Title:
- Calibrated grid of rotating single star models
- Short Name:
- J/A+A/622/A50
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Massive star evolution is dominated by various physical effects, including mass loss, overshooting, and rotation, but the prescriptions of their effects are poorly constrained, even affecting our understanding of the main sequence. We aim to constrain massive star evolution models using the unique testbed eclipsing binary HD166734 with new grids of MESA stellar evolution models, adopting calibrated prescriptions of overshooting, mass loss, and rotation. We introduce a novel tool: the "mass-luminosity plane" or "M-L plane", as an equivalent to the traditional HR diagram, utilising it to reproduce the testbed binary HD166734 with newly calibrated MESA stellar evolution models for single stars. We can only reproduce the Galactic binary system with an enhanced amount of core overshooting (alpha_ov_=0.5), mass loss, and rotational mixing. We can utilise the gradient in the M-L plane to constrain the amount of mass loss to 0.5-1.5 times the standard Vink et al. (2001A&A...369..574V) prescriptions, and we can exclude extreme reduction or multiplication factors. The extent of the vectors in the M-L plane leads us to conclude that the amount of core overshooting is larger than is normally adopted in contemporary massive star evolution models. We furthermore conclude that rotational mixing is mandatory to get the nitrogen abundance ratios between the primary and secondary components to be correct (3:1) in our testbed binary system. Our calibrated grid of models, alongside our new M-L plane approach, present the possibility of a widened main sequence due to an increased demand for core overshooting. The increased amount of core overshooting is not only needed to explain the extended main sequence, but the enhanced overshooting is also needed to explain the location of the upper-luminosity limit of the red supergiants. Finally, the increased amount of core overshooting has - via the compactness parameter - implications for supernova explodibility.
- ID:
- ivo://CDS.VizieR/J/PASP/120/1128
- Title:
- Calibrated griz magnitudes of Tycho stars
- Short Name:
- J/PASP/120/1128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometric calibration at an accuracy of ~5% in an arbitrary celestial location is frequently needed. However, existing all-sky astronomical catalogue do not reach this accuracy, and time consuming photometric calibration procedures are required. I fitted the Hipparcos B_T_, and V_T_ magnitudes, along with the 2MASS J, H, and K magnitudes of Tycho-2 catalog-stars with stellar spectral templates. From the best fit spectral template derived for each star, I calculated its synthetic SDSS griz magnitudes, and constructed an all-sky catalog of griz magnitudes of bright stars (V<12). Testing this method on SDSS photometric telescope observations, I find that the photometric accuracy, for a single star, is usually about 0.12, 0.12, 0.10 and 0.08 mag (1sigma), for the g, r, i, and z-bands, respectively. However, by using ~10 such stars, the typical errors per calibrated field (systematic + statistical) can be reduced to about 0.04, 0.03, 0.02, and 0.02 mag, in the g, r, i, and z-bands, respectively. Therefore, in cases for which several calibration stars can be observed in the field of view of an instrument, it is possible to photometrically calibrate the image.
- ID:
- ivo://CDS.VizieR/J/ApJ/835/25
- Title:
- Calibrated solar S-index time series
- Short Name:
- J/ApJ/835/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The most commonly used index of stellar magnetic activity is the instrumental flux scale of singly ionized calcium H & K line core emission, S, developed by the Mount Wilson Observatory (MWO) HK Project, or the derivative index R'_HK_. Accurately placing the Sun on the S scale is important for comparing solar activity to that of the Sun-like stars. We present previously unpublished measurements of the reflected sunlight from the Moon using the second-generation MWO HK photometer during solar cycle 23 and determine cycle minimum S_23,min_=0.1634+/-0.0008, amplitude {Delta}S_23_=0.0143+/-0.0012, and mean <S_23_>=0.1701+/-0.0005. By establishing a proxy relationship with the closely related National Solar Observatory Sacramento Peak calcium K emission index, itself well correlated with the Kodaikanal Observatory plage index, we extend the MWO S time series to cover cycles 15-24 and find on average <S_min_>=0.1621+/-0.0008, <{Delta}S_cyc_>=0.0145+/-0.0012, <S_cyc_>=0.1694+/-0.0005. Our measurements represent an improvement over previous estimates that relied on stellar measurements or solar proxies with non-overlapping time series. We find good agreement from these results with measurements by the Solar-Stellar Spectrograph at Lowell Observatory, an independently calibrated instrument, which gives us additional confidence that we have accurately placed the Sun on the S-index flux scale.
- ID:
- ivo://CDS.VizieR/J/ApJ/744/138
- Title:
- Calibrated visibilities of {epsilon} Eri
- Short Name:
- J/ApJ/744/138
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We measured the angular diameter of the exoplanet host star {epsilon} Eridani using the Navy Optical Interferometer. We determined its physical radius, effective temperature, and mass by combining our measurement with the star's parallax, photometry from the literature, and the Yonsei-Yale isochrones, respectively. We used the resulting stellar mass of 0.82+/-0.05M_{sun}_ plus the mass function from Benedict et al. to calculate the planet's mass, which is 1.53+/-0.22M_Jupiter_. Using our new effective temperature, we also estimated the extent of the habitable zone for the system.
